LCOV - code coverage report
Current view: top level - gcc - tree-ssa-loop-prefetch.c (source / functions) Hit Total Coverage
Test: gcc.info Lines: 679 769 88.3 %
Date: 2020-03-28 11:57:23 Functions: 38 42 90.5 %
Legend: Lines: hit not hit | Branches: + taken - not taken # not executed Branches: 0 0 -

           Branch data     Line data    Source code
       1                 :            : /* Array prefetching.
       2                 :            :    Copyright (C) 2005-2020 Free Software Foundation, Inc.
       3                 :            : 
       4                 :            : This file is part of GCC.
       5                 :            : 
       6                 :            : GCC is free software; you can redistribute it and/or modify it
       7                 :            : under the terms of the GNU General Public License as published by the
       8                 :            : Free Software Foundation; either version 3, or (at your option) any
       9                 :            : later version.
      10                 :            : 
      11                 :            : GCC is distributed in the hope that it will be useful, but WITHOUT
      12                 :            : ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
      13                 :            : FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
      14                 :            : for more details.
      15                 :            : 
      16                 :            : You should have received a copy of the GNU General Public License
      17                 :            : along with GCC; see the file COPYING3.  If not see
      18                 :            : <http://www.gnu.org/licenses/>.  */
      19                 :            : 
      20                 :            : #include "config.h"
      21                 :            : #include "system.h"
      22                 :            : #include "coretypes.h"
      23                 :            : #include "backend.h"
      24                 :            : #include "target.h"
      25                 :            : #include "rtl.h"
      26                 :            : #include "tree.h"
      27                 :            : #include "gimple.h"
      28                 :            : #include "predict.h"
      29                 :            : #include "tree-pass.h"
      30                 :            : #include "gimple-ssa.h"
      31                 :            : #include "optabs-query.h"
      32                 :            : #include "tree-pretty-print.h"
      33                 :            : #include "fold-const.h"
      34                 :            : #include "stor-layout.h"
      35                 :            : #include "gimplify.h"
      36                 :            : #include "gimple-iterator.h"
      37                 :            : #include "gimplify-me.h"
      38                 :            : #include "tree-ssa-loop-ivopts.h"
      39                 :            : #include "tree-ssa-loop-manip.h"
      40                 :            : #include "tree-ssa-loop-niter.h"
      41                 :            : #include "tree-ssa-loop.h"
      42                 :            : #include "ssa.h"
      43                 :            : #include "tree-into-ssa.h"
      44                 :            : #include "cfgloop.h"
      45                 :            : #include "tree-scalar-evolution.h"
      46                 :            : #include "langhooks.h"
      47                 :            : #include "tree-inline.h"
      48                 :            : #include "tree-data-ref.h"
      49                 :            : #include "diagnostic-core.h"
      50                 :            : #include "dbgcnt.h"
      51                 :            : 
      52                 :            : /* This pass inserts prefetch instructions to optimize cache usage during
      53                 :            :    accesses to arrays in loops.  It processes loops sequentially and:
      54                 :            : 
      55                 :            :    1) Gathers all memory references in the single loop.
      56                 :            :    2) For each of the references it decides when it is profitable to prefetch
      57                 :            :       it.  To do it, we evaluate the reuse among the accesses, and determines
      58                 :            :       two values: PREFETCH_BEFORE (meaning that it only makes sense to do
      59                 :            :       prefetching in the first PREFETCH_BEFORE iterations of the loop) and
      60                 :            :       PREFETCH_MOD (meaning that it only makes sense to prefetch in the
      61                 :            :       iterations of the loop that are zero modulo PREFETCH_MOD).  For example
      62                 :            :       (assuming cache line size is 64 bytes, char has size 1 byte and there
      63                 :            :       is no hardware sequential prefetch):
      64                 :            : 
      65                 :            :       char *a;
      66                 :            :       for (i = 0; i < max; i++)
      67                 :            :         {
      68                 :            :           a[255] = ...;         (0)
      69                 :            :           a[i] = ...;           (1)
      70                 :            :           a[i + 64] = ...;      (2)
      71                 :            :           a[16*i] = ...;        (3)
      72                 :            :           a[187*i] = ...;       (4)
      73                 :            :           a[187*i + 50] = ...;  (5)
      74                 :            :         }
      75                 :            : 
      76                 :            :        (0) obviously has PREFETCH_BEFORE 1
      77                 :            :        (1) has PREFETCH_BEFORE 64, since (2) accesses the same memory
      78                 :            :            location 64 iterations before it, and PREFETCH_MOD 64 (since
      79                 :            :            it hits the same cache line otherwise).
      80                 :            :        (2) has PREFETCH_MOD 64
      81                 :            :        (3) has PREFETCH_MOD 4
      82                 :            :        (4) has PREFETCH_MOD 1.  We do not set PREFETCH_BEFORE here, since
      83                 :            :            the cache line accessed by (5) is the same with probability only
      84                 :            :            7/32.
      85                 :            :        (5) has PREFETCH_MOD 1 as well.
      86                 :            : 
      87                 :            :       Additionally, we use data dependence analysis to determine for each
      88                 :            :       reference the distance till the first reuse; this information is used
      89                 :            :       to determine the temporality of the issued prefetch instruction.
      90                 :            : 
      91                 :            :    3) We determine how much ahead we need to prefetch.  The number of
      92                 :            :       iterations needed is time to fetch / time spent in one iteration of
      93                 :            :       the loop.  The problem is that we do not know either of these values,
      94                 :            :       so we just make a heuristic guess based on a magic (possibly)
      95                 :            :       target-specific constant and size of the loop.
      96                 :            : 
      97                 :            :    4) Determine which of the references we prefetch.  We take into account
      98                 :            :       that there is a maximum number of simultaneous prefetches (provided
      99                 :            :       by machine description).  We prefetch as many prefetches as possible
     100                 :            :       while still within this bound (starting with those with lowest
     101                 :            :       prefetch_mod, since they are responsible for most of the cache
     102                 :            :       misses).
     103                 :            : 
     104                 :            :    5) We unroll and peel loops so that we are able to satisfy PREFETCH_MOD
     105                 :            :       and PREFETCH_BEFORE requirements (within some bounds), and to avoid
     106                 :            :       prefetching nonaccessed memory.
     107                 :            :       TODO -- actually implement peeling.
     108                 :            : 
     109                 :            :    6) We actually emit the prefetch instructions.  ??? Perhaps emit the
     110                 :            :       prefetch instructions with guards in cases where 5) was not sufficient
     111                 :            :       to satisfy the constraints?
     112                 :            : 
     113                 :            :    A cost model is implemented to determine whether or not prefetching is
     114                 :            :    profitable for a given loop.  The cost model has three heuristics:
     115                 :            : 
     116                 :            :    1. Function trip_count_to_ahead_ratio_too_small_p implements a
     117                 :            :       heuristic that determines whether or not the loop has too few
     118                 :            :       iterations (compared to ahead).  Prefetching is not likely to be
     119                 :            :       beneficial if the trip count to ahead ratio is below a certain
     120                 :            :       minimum.
     121                 :            : 
     122                 :            :    2. Function mem_ref_count_reasonable_p implements a heuristic that
     123                 :            :       determines whether the given loop has enough CPU ops that can be
     124                 :            :       overlapped with cache missing memory ops.  If not, the loop
     125                 :            :       won't benefit from prefetching.  In the implementation,
     126                 :            :       prefetching is not considered beneficial if the ratio between
     127                 :            :       the instruction count and the mem ref count is below a certain
     128                 :            :       minimum.
     129                 :            : 
     130                 :            :    3. Function insn_to_prefetch_ratio_too_small_p implements a
     131                 :            :       heuristic that disables prefetching in a loop if the prefetching
     132                 :            :       cost is above a certain limit.  The relative prefetching cost is
     133                 :            :       estimated by taking the ratio between the prefetch count and the
     134                 :            :       total intruction count (this models the I-cache cost).
     135                 :            : 
     136                 :            :    The limits used in these heuristics are defined as parameters with
     137                 :            :    reasonable default values. Machine-specific default values will be
     138                 :            :    added later.
     139                 :            : 
     140                 :            :    Some other TODO:
     141                 :            :       -- write and use more general reuse analysis (that could be also used
     142                 :            :          in other cache aimed loop optimizations)
     143                 :            :       -- make it behave sanely together with the prefetches given by user
     144                 :            :          (now we just ignore them; at the very least we should avoid
     145                 :            :          optimizing loops in that user put his own prefetches)
     146                 :            :       -- we assume cache line size alignment of arrays; this could be
     147                 :            :          improved.  */
     148                 :            : 
     149                 :            : /* Magic constants follow.  These should be replaced by machine specific
     150                 :            :    numbers.  */
     151                 :            : 
     152                 :            : /* True if write can be prefetched by a read prefetch.  */
     153                 :            : 
     154                 :            : #ifndef WRITE_CAN_USE_READ_PREFETCH
     155                 :            : #define WRITE_CAN_USE_READ_PREFETCH 1
     156                 :            : #endif
     157                 :            : 
     158                 :            : /* True if read can be prefetched by a write prefetch. */
     159                 :            : 
     160                 :            : #ifndef READ_CAN_USE_WRITE_PREFETCH
     161                 :            : #define READ_CAN_USE_WRITE_PREFETCH 0
     162                 :            : #endif
     163                 :            : 
     164                 :            : /* The size of the block loaded by a single prefetch.  Usually, this is
     165                 :            :    the same as cache line size (at the moment, we only consider one level
     166                 :            :    of cache hierarchy).  */
     167                 :            : 
     168                 :            : #ifndef PREFETCH_BLOCK
     169                 :            : #define PREFETCH_BLOCK param_l1_cache_line_size
     170                 :            : #endif
     171                 :            : 
     172                 :            : /* Do we have a forward hardware sequential prefetching?  */
     173                 :            : 
     174                 :            : #ifndef HAVE_FORWARD_PREFETCH
     175                 :            : #define HAVE_FORWARD_PREFETCH 0
     176                 :            : #endif
     177                 :            : 
     178                 :            : /* Do we have a backward hardware sequential prefetching?  */
     179                 :            : 
     180                 :            : #ifndef HAVE_BACKWARD_PREFETCH
     181                 :            : #define HAVE_BACKWARD_PREFETCH 0
     182                 :            : #endif
     183                 :            : 
     184                 :            : /* In some cases we are only able to determine that there is a certain
     185                 :            :    probability that the two accesses hit the same cache line.  In this
     186                 :            :    case, we issue the prefetches for both of them if this probability
     187                 :            :    is less then (1000 - ACCEPTABLE_MISS_RATE) per thousand.  */
     188                 :            : 
     189                 :            : #ifndef ACCEPTABLE_MISS_RATE
     190                 :            : #define ACCEPTABLE_MISS_RATE 50
     191                 :            : #endif
     192                 :            : 
     193                 :            : #define L1_CACHE_SIZE_BYTES ((unsigned) (param_l1_cache_size * 1024))
     194                 :            : #define L2_CACHE_SIZE_BYTES ((unsigned) (param_l2_cache_size * 1024))
     195                 :            : 
     196                 :            : /* We consider a memory access nontemporal if it is not reused sooner than
     197                 :            :    after L2_CACHE_SIZE_BYTES of memory are accessed.  However, we ignore
     198                 :            :    accesses closer than L1_CACHE_SIZE_BYTES / NONTEMPORAL_FRACTION,
     199                 :            :    so that we use nontemporal prefetches e.g. if single memory location
     200                 :            :    is accessed several times in a single iteration of the loop.  */
     201                 :            : #define NONTEMPORAL_FRACTION 16
     202                 :            : 
     203                 :            : /* In case we have to emit a memory fence instruction after the loop that
     204                 :            :    uses nontemporal stores, this defines the builtin to use.  */
     205                 :            : 
     206                 :            : #ifndef FENCE_FOLLOWING_MOVNT
     207                 :            : #define FENCE_FOLLOWING_MOVNT NULL_TREE
     208                 :            : #endif
     209                 :            : 
     210                 :            : /* It is not profitable to prefetch when the trip count is not at
     211                 :            :    least TRIP_COUNT_TO_AHEAD_RATIO times the prefetch ahead distance.
     212                 :            :    For example, in a loop with a prefetch ahead distance of 10,
     213                 :            :    supposing that TRIP_COUNT_TO_AHEAD_RATIO is equal to 4, it is
     214                 :            :    profitable to prefetch when the trip count is greater or equal to
     215                 :            :    40.  In that case, 30 out of the 40 iterations will benefit from
     216                 :            :    prefetching.  */
     217                 :            : 
     218                 :            : #ifndef TRIP_COUNT_TO_AHEAD_RATIO
     219                 :            : #define TRIP_COUNT_TO_AHEAD_RATIO 4
     220                 :            : #endif
     221                 :            : 
     222                 :            : /* The group of references between that reuse may occur.  */
     223                 :            : 
     224                 :            : struct mem_ref_group
     225                 :            : {
     226                 :            :   tree base;                    /* Base of the reference.  */
     227                 :            :   tree step;                    /* Step of the reference.  */
     228                 :            :   struct mem_ref *refs;         /* References in the group.  */
     229                 :            :   struct mem_ref_group *next;   /* Next group of references.  */
     230                 :            :   unsigned int uid;             /* Group UID, used only for debugging.  */
     231                 :            : };
     232                 :            : 
     233                 :            : /* Assigned to PREFETCH_BEFORE when all iterations are to be prefetched.  */
     234                 :            : 
     235                 :            : #define PREFETCH_ALL            HOST_WIDE_INT_M1U
     236                 :            : 
     237                 :            : /* Do not generate a prefetch if the unroll factor is significantly less
     238                 :            :    than what is required by the prefetch.  This is to avoid redundant
     239                 :            :    prefetches.  For example, when prefetch_mod is 16 and unroll_factor is
     240                 :            :    2, prefetching requires unrolling the loop 16 times, but
     241                 :            :    the loop is actually unrolled twice.  In this case (ratio = 8),
     242                 :            :    prefetching is not likely to be beneficial.  */
     243                 :            : 
     244                 :            : #ifndef PREFETCH_MOD_TO_UNROLL_FACTOR_RATIO
     245                 :            : #define PREFETCH_MOD_TO_UNROLL_FACTOR_RATIO 4
     246                 :            : #endif
     247                 :            : 
     248                 :            : /* Some of the prefetch computations have quadratic complexity.  We want to
     249                 :            :    avoid huge compile times and, therefore, want to limit the amount of
     250                 :            :    memory references per loop where we consider prefetching.  */
     251                 :            : 
     252                 :            : #ifndef PREFETCH_MAX_MEM_REFS_PER_LOOP
     253                 :            : #define PREFETCH_MAX_MEM_REFS_PER_LOOP 200
     254                 :            : #endif
     255                 :            : 
     256                 :            : /* The memory reference.  */
     257                 :            : 
     258                 :            : struct mem_ref
     259                 :            : {
     260                 :            :   gimple *stmt;                 /* Statement in that the reference appears.  */
     261                 :            :   tree mem;                     /* The reference.  */
     262                 :            :   HOST_WIDE_INT delta;          /* Constant offset of the reference.  */
     263                 :            :   struct mem_ref_group *group;  /* The group of references it belongs to.  */
     264                 :            :   unsigned HOST_WIDE_INT prefetch_mod;
     265                 :            :                                 /* Prefetch only each PREFETCH_MOD-th
     266                 :            :                                    iteration.  */
     267                 :            :   unsigned HOST_WIDE_INT prefetch_before;
     268                 :            :                                 /* Prefetch only first PREFETCH_BEFORE
     269                 :            :                                    iterations.  */
     270                 :            :   unsigned reuse_distance;      /* The amount of data accessed before the first
     271                 :            :                                    reuse of this value.  */
     272                 :            :   struct mem_ref *next;         /* The next reference in the group.  */
     273                 :            :   unsigned int uid;             /* Ref UID, used only for debugging.  */
     274                 :            :   unsigned write_p : 1;         /* Is it a write?  */
     275                 :            :   unsigned independent_p : 1;   /* True if the reference is independent on
     276                 :            :                                    all other references inside the loop.  */
     277                 :            :   unsigned issue_prefetch_p : 1;        /* Should we really issue the prefetch?  */
     278                 :            :   unsigned storent_p : 1;       /* True if we changed the store to a
     279                 :            :                                    nontemporal one.  */
     280                 :            : };
     281                 :            : 
     282                 :            : /* Dumps information about memory reference */
     283                 :            : static void
     284                 :         30 : dump_mem_details (FILE *file, tree base, tree step,
     285                 :            :             HOST_WIDE_INT delta, bool write_p) 
     286                 :            : {
     287                 :         30 :   fprintf (file, "(base ");
     288                 :         30 :   print_generic_expr (file, base, TDF_SLIM);
     289                 :         30 :   fprintf (file, ", step ");
     290                 :         30 :   if (cst_and_fits_in_hwi (step))
     291                 :         22 :     fprintf (file, HOST_WIDE_INT_PRINT_DEC, int_cst_value (step));
     292                 :            :   else
     293                 :          8 :     print_generic_expr (file, step, TDF_SLIM);
     294                 :         30 :   fprintf (file, ")\n");
     295                 :         30 :   fprintf (file, "  delta " HOST_WIDE_INT_PRINT_DEC "\n", delta);
     296                 :         49 :   fprintf (file, "  %s\n\n", write_p ? "write" : "read");
     297                 :         30 : }
     298                 :            : 
     299                 :            : /* Dumps information about reference REF to FILE.  */
     300                 :            : 
     301                 :            : static void
     302                 :         52 : dump_mem_ref (FILE *file, struct mem_ref *ref)
     303                 :            : {
     304                 :         52 :   fprintf (file, "reference %u:%u (", ref->group->uid, ref->uid);
     305                 :         52 :   print_generic_expr (file, ref->mem, TDF_SLIM);
     306                 :         52 :   fprintf (file, ")\n");
     307                 :         52 : }
     308                 :            : 
     309                 :            : /* Finds a group with BASE and STEP in GROUPS, or creates one if it does not
     310                 :            :    exist.  */
     311                 :            : 
     312                 :            : static struct mem_ref_group *
     313                 :        369 : find_or_create_group (struct mem_ref_group **groups, tree base, tree step)
     314                 :            : {
     315                 :            :   /* Global count for setting struct mem_ref_group->uid.  */
     316                 :       1030 :   static unsigned int last_mem_ref_group_uid = 0;
     317                 :            : 
     318                 :       1030 :   struct mem_ref_group *group;
     319                 :            : 
     320                 :       1030 :   for (; *groups; groups = &(*groups)->next)
     321                 :            :     {
     322                 :        840 :       if (operand_equal_p ((*groups)->step, step, 0)
     323                 :        840 :           && operand_equal_p ((*groups)->base, base, 0))
     324                 :        177 :         return *groups;
     325                 :            : 
     326                 :            :       /* If step is an integer constant, keep the list of groups sorted
     327                 :            :          by decreasing step.  */
     328                 :       1234 :       if (cst_and_fits_in_hwi ((*groups)->step) && cst_and_fits_in_hwi (step)
     329                 :       1232 :           && int_cst_value ((*groups)->step) < int_cst_value (step))
     330                 :            :         break;
     331                 :            :     }
     332                 :            : 
     333                 :        192 :   group = XNEW (struct mem_ref_group);
     334                 :        192 :   group->base = base;
     335                 :        192 :   group->step = step;
     336                 :        192 :   group->refs = NULL;
     337                 :        192 :   group->uid = ++last_mem_ref_group_uid;
     338                 :        192 :   group->next = *groups;
     339                 :        192 :   *groups = group;
     340                 :            : 
     341                 :        192 :   return group;
     342                 :            : }
     343                 :            : 
     344                 :            : /* Records a memory reference MEM in GROUP with offset DELTA and write status
     345                 :            :    WRITE_P.  The reference occurs in statement STMT.  */
     346                 :            : 
     347                 :            : static void
     348                 :        369 : record_ref (struct mem_ref_group *group, gimple *stmt, tree mem,
     349                 :            :             HOST_WIDE_INT delta, bool write_p)
     350                 :            : {
     351                 :        369 :   unsigned int last_mem_ref_uid = 0;
     352                 :        369 :   struct mem_ref **aref;
     353                 :            : 
     354                 :            :   /* Do not record the same address twice.  */
     355                 :        527 :   for (aref = &group->refs; *aref; aref = &(*aref)->next)
     356                 :            :     {
     357                 :        295 :       last_mem_ref_uid = (*aref)->uid;
     358                 :            : 
     359                 :            :       /* It does not have to be possible for write reference to reuse the read
     360                 :            :          prefetch, or vice versa.  */
     361                 :        295 :       if (!WRITE_CAN_USE_READ_PREFETCH
     362                 :            :           && write_p
     363                 :            :           && !(*aref)->write_p)
     364                 :            :         continue;
     365                 :        295 :       if (!READ_CAN_USE_WRITE_PREFETCH
     366                 :            :           && !write_p
     367                 :          9 :           && (*aref)->write_p)
     368                 :          0 :         continue;
     369                 :            : 
     370                 :        295 :       if ((*aref)->delta == delta)
     371                 :            :         return;
     372                 :            :     }
     373                 :            : 
     374                 :        232 :   (*aref) = XNEW (struct mem_ref);
     375                 :        232 :   (*aref)->stmt = stmt;
     376                 :        232 :   (*aref)->mem = mem;
     377                 :        232 :   (*aref)->delta = delta;
     378                 :        232 :   (*aref)->write_p = write_p;
     379                 :        232 :   (*aref)->prefetch_before = PREFETCH_ALL;
     380                 :        232 :   (*aref)->prefetch_mod = 1;
     381                 :        232 :   (*aref)->reuse_distance = 0;
     382                 :        232 :   (*aref)->issue_prefetch_p = false;
     383                 :        232 :   (*aref)->group = group;
     384                 :        232 :   (*aref)->next = NULL;
     385                 :        232 :   (*aref)->independent_p = false;
     386                 :        232 :   (*aref)->storent_p = false;
     387                 :        232 :   (*aref)->uid = last_mem_ref_uid + 1;
     388                 :            : 
     389                 :        232 :   if (dump_file && (dump_flags & TDF_DETAILS))
     390                 :            :     {
     391                 :         26 :       dump_mem_ref (dump_file, *aref);
     392                 :            : 
     393                 :         26 :       fprintf (dump_file, "  group %u ", group->uid);
     394                 :         26 :       dump_mem_details (dump_file, group->base, group->step, delta,
     395                 :            :                         write_p);
     396                 :            :     }
     397                 :            : }
     398                 :            : 
     399                 :            : /* Release memory references in GROUPS.  */
     400                 :            : 
     401                 :            : static void
     402                 :        104 : release_mem_refs (struct mem_ref_group *groups)
     403                 :            : {
     404                 :        296 :   struct mem_ref_group *next_g;
     405                 :        296 :   struct mem_ref *ref, *next_r;
     406                 :            : 
     407                 :        296 :   for (; groups; groups = next_g)
     408                 :            :     {
     409                 :        192 :       next_g = groups->next;
     410                 :        424 :       for (ref = groups->refs; ref; ref = next_r)
     411                 :            :         {
     412                 :        232 :           next_r = ref->next;
     413                 :        232 :           free (ref);
     414                 :            :         }
     415                 :        192 :       free (groups);
     416                 :            :     }
     417                 :        104 : }
     418                 :            : 
     419                 :            : /* A structure used to pass arguments to idx_analyze_ref.  */
     420                 :            : 
     421                 :            : struct ar_data
     422                 :            : {
     423                 :            :   class loop *loop;                     /* Loop of the reference.  */
     424                 :            :   gimple *stmt;                         /* Statement of the reference.  */
     425                 :            :   tree *step;                           /* Step of the memory reference.  */
     426                 :            :   HOST_WIDE_INT *delta;                 /* Offset of the memory reference.  */
     427                 :            : };
     428                 :            : 
     429                 :            : /* Analyzes a single INDEX of a memory reference to obtain information
     430                 :            :    described at analyze_ref.  Callback for for_each_index.  */
     431                 :            : 
     432                 :            : static bool
     433                 :        538 : idx_analyze_ref (tree base, tree *index, void *data)
     434                 :            : {
     435                 :        538 :   struct ar_data *ar_data = (struct ar_data *) data;
     436                 :        538 :   tree ibase, step, stepsize;
     437                 :        538 :   HOST_WIDE_INT idelta = 0, imult = 1;
     438                 :        538 :   affine_iv iv;
     439                 :            : 
     440                 :       1076 :   if (!simple_iv (ar_data->loop, loop_containing_stmt (ar_data->stmt),
     441                 :            :                   *index, &iv, true))
     442                 :            :     return false;
     443                 :        415 :   ibase = iv.base;
     444                 :        415 :   step = iv.step;
     445                 :            : 
     446                 :        415 :   if (TREE_CODE (ibase) == POINTER_PLUS_EXPR
     447                 :        415 :       && cst_and_fits_in_hwi (TREE_OPERAND (ibase, 1)))
     448                 :            :     {
     449                 :          8 :       idelta = int_cst_value (TREE_OPERAND (ibase, 1));
     450                 :          8 :       ibase = TREE_OPERAND (ibase, 0);
     451                 :            :     }
     452                 :        415 :   if (cst_and_fits_in_hwi (ibase))
     453                 :            :     {
     454                 :         84 :       idelta += int_cst_value (ibase);
     455                 :         84 :       ibase = build_int_cst (TREE_TYPE (ibase), 0);
     456                 :            :     }
     457                 :            : 
     458                 :        415 :   if (TREE_CODE (base) == ARRAY_REF)
     459                 :            :     {
     460                 :        118 :       stepsize = array_ref_element_size (base);
     461                 :        118 :       if (!cst_and_fits_in_hwi (stepsize))
     462                 :            :         return false;
     463                 :        118 :       imult = int_cst_value (stepsize);
     464                 :        118 :       step = fold_build2 (MULT_EXPR, sizetype,
     465                 :            :                           fold_convert (sizetype, step),
     466                 :            :                           fold_convert (sizetype, stepsize));
     467                 :        118 :       idelta *= imult;
     468                 :            :     }
     469                 :            : 
     470                 :        415 :   if (*ar_data->step == NULL_TREE)
     471                 :        373 :     *ar_data->step = step;
     472                 :            :   else
     473                 :         42 :     *ar_data->step = fold_build2 (PLUS_EXPR, sizetype,
     474                 :            :                                   fold_convert (sizetype, *ar_data->step),
     475                 :            :                                   fold_convert (sizetype, step));
     476                 :        415 :   *ar_data->delta += idelta;
     477                 :        415 :   *index = ibase;
     478                 :            : 
     479                 :        415 :   return true;
     480                 :            : }
     481                 :            : 
     482                 :            : /* Tries to express REF_P in shape &BASE + STEP * iter + DELTA, where DELTA and
     483                 :            :    STEP are integer constants and iter is number of iterations of LOOP.  The
     484                 :            :    reference occurs in statement STMT.  Strips nonaddressable component
     485                 :            :    references from REF_P.  */
     486                 :            : 
     487                 :            : static bool
     488                 :        498 : analyze_ref (class loop *loop, tree *ref_p, tree *base,
     489                 :            :              tree *step, HOST_WIDE_INT *delta,
     490                 :            :              gimple *stmt)
     491                 :            : {
     492                 :        498 :   struct ar_data ar_data;
     493                 :        498 :   tree off;
     494                 :        498 :   HOST_WIDE_INT bit_offset;
     495                 :        498 :   tree ref = *ref_p;
     496                 :            : 
     497                 :        498 :   *step = NULL_TREE;
     498                 :        498 :   *delta = 0;
     499                 :            : 
     500                 :            :   /* First strip off the component references.  Ignore bitfields.
     501                 :            :      Also strip off the real and imagine parts of a complex, so that
     502                 :            :      they can have the same base.  */
     503                 :        498 :   if (TREE_CODE (ref) == REALPART_EXPR
     504                 :        498 :       || TREE_CODE (ref) == IMAGPART_EXPR
     505                 :        498 :       || (TREE_CODE (ref) == COMPONENT_REF
     506                 :         20 :           && DECL_NONADDRESSABLE_P (TREE_OPERAND (ref, 1))))
     507                 :            :     {
     508                 :         12 :       if (TREE_CODE (ref) == IMAGPART_EXPR)
     509                 :          6 :         *delta += int_size_in_bytes (TREE_TYPE (ref));
     510                 :         12 :       ref = TREE_OPERAND (ref, 0);
     511                 :            :     }
     512                 :            : 
     513                 :        498 :   *ref_p = ref;
     514                 :            : 
     515                 :        523 :   for (; TREE_CODE (ref) == COMPONENT_REF; ref = TREE_OPERAND (ref, 0))
     516                 :            :     {
     517                 :         25 :       off = DECL_FIELD_BIT_OFFSET (TREE_OPERAND (ref, 1));
     518                 :         25 :       bit_offset = TREE_INT_CST_LOW (off);
     519                 :         25 :       gcc_assert (bit_offset % BITS_PER_UNIT == 0);
     520                 :            : 
     521                 :         25 :       *delta += bit_offset / BITS_PER_UNIT;
     522                 :            :     }
     523                 :            : 
     524                 :        498 :   *base = unshare_expr (ref);
     525                 :        498 :   ar_data.loop = loop;
     526                 :        498 :   ar_data.stmt = stmt;
     527                 :        498 :   ar_data.step = step;
     528                 :        498 :   ar_data.delta = delta;
     529                 :        498 :   return for_each_index (base, idx_analyze_ref, &ar_data);
     530                 :            : }
     531                 :            : 
     532                 :            : /* Record a memory reference REF to the list REFS.  The reference occurs in
     533                 :            :    LOOP in statement STMT and it is write if WRITE_P.  Returns true if the
     534                 :            :    reference was recorded, false otherwise.  */
     535                 :            : 
     536                 :            : static bool
     537                 :        498 : gather_memory_references_ref (class loop *loop, struct mem_ref_group **refs,
     538                 :            :                               tree ref, bool write_p, gimple *stmt)
     539                 :            : {
     540                 :        498 :   tree base, step;
     541                 :        498 :   HOST_WIDE_INT delta;
     542                 :        498 :   struct mem_ref_group *agrp;
     543                 :            : 
     544                 :        498 :   if (get_base_address (ref) == NULL)
     545                 :            :     return false;
     546                 :            : 
     547                 :        498 :   if (!analyze_ref (loop, &ref, &base, &step, &delta, stmt))
     548                 :            :     return false;
     549                 :            :   /* If analyze_ref fails the default is a NULL_TREE.  We can stop here.  */
     550                 :        375 :   if (step == NULL_TREE)
     551                 :            :     return false;
     552                 :            : 
     553                 :            :   /* Stop if the address of BASE could not be taken.  */
     554                 :        373 :   if (may_be_nonaddressable_p (base))
     555                 :            :     return false;
     556                 :            : 
     557                 :            :   /* Limit non-constant step prefetching only to the innermost loops and 
     558                 :            :      only when the step is loop invariant in the entire loop nest. */
     559                 :        373 :   if (!cst_and_fits_in_hwi (step))
     560                 :            :     {
     561                 :        185 :       if (loop->inner != NULL)
     562                 :            :         {
     563                 :          0 :           if (dump_file && (dump_flags & TDF_DETAILS))
     564                 :            :             {
     565                 :          0 :               fprintf (dump_file, "Memory expression %p\n",(void *) ref ); 
     566                 :          0 :               print_generic_expr (dump_file, ref, TDF_SLIM);
     567                 :          0 :               fprintf (dump_file,":");
     568                 :          0 :               dump_mem_details (dump_file, base, step, delta, write_p);
     569                 :          0 :               fprintf (dump_file, 
     570                 :            :                        "Ignoring %p, non-constant step prefetching is "
     571                 :            :                        "limited to inner most loops \n", 
     572                 :            :                        (void *) ref);
     573                 :            :             }
     574                 :          0 :             return false;    
     575                 :            :          }
     576                 :            :       else
     577                 :            :         {
     578                 :        370 :           if (!expr_invariant_in_loop_p (loop_outermost (loop), step))
     579                 :            :           {
     580                 :          4 :             if (dump_file && (dump_flags & TDF_DETAILS))
     581                 :            :               {
     582                 :          4 :                 fprintf (dump_file, "Memory expression %p\n",(void *) ref );
     583                 :          4 :                 print_generic_expr (dump_file, ref, TDF_SLIM);
     584                 :          4 :                 fprintf (dump_file,":");
     585                 :          4 :                 dump_mem_details (dump_file, base, step, delta, write_p);
     586                 :          4 :                 fprintf (dump_file, 
     587                 :            :                          "Not prefetching, ignoring %p due to "
     588                 :            :                          "loop variant step\n",
     589                 :            :                          (void *) ref);
     590                 :            :               }
     591                 :          4 :               return false;                 
     592                 :            :             }
     593                 :            :         }
     594                 :            :     }
     595                 :            : 
     596                 :            :   /* Now we know that REF = &BASE + STEP * iter + DELTA, where DELTA and STEP
     597                 :            :      are integer constants.  */
     598                 :        369 :   agrp = find_or_create_group (refs, base, step);
     599                 :        369 :   record_ref (agrp, stmt, ref, delta, write_p);
     600                 :            : 
     601                 :        369 :   return true;
     602                 :            : }
     603                 :            : 
     604                 :            : /* Record the suitable memory references in LOOP.  NO_OTHER_REFS is set to
     605                 :            :    true if there are no other memory references inside the loop.  */
     606                 :            : 
     607                 :            : static struct mem_ref_group *
     608                 :        104 : gather_memory_references (class loop *loop, bool *no_other_refs, unsigned *ref_count)
     609                 :            : {
     610                 :        104 :   basic_block *body = get_loop_body_in_dom_order (loop);
     611                 :        104 :   basic_block bb;
     612                 :        104 :   unsigned i;
     613                 :        104 :   gimple_stmt_iterator bsi;
     614                 :        104 :   gimple *stmt;
     615                 :        104 :   tree lhs, rhs;
     616                 :        104 :   struct mem_ref_group *refs = NULL;
     617                 :            : 
     618                 :        104 :   *no_other_refs = true;
     619                 :        104 :   *ref_count = 0;
     620                 :            : 
     621                 :            :   /* Scan the loop body in order, so that the former references precede the
     622                 :            :      later ones.  */
     623                 :       1003 :   for (i = 0; i < loop->num_nodes; i++)
     624                 :            :     {
     625                 :        899 :       bb = body[i];
     626                 :        899 :       if (bb->loop_father != loop)
     627                 :        597 :         continue;
     628                 :            : 
     629                 :       3918 :       for (bsi = gsi_start_bb (bb); !gsi_end_p (bsi); gsi_next (&bsi))
     630                 :            :         {
     631                 :       3314 :           stmt = gsi_stmt (bsi);
     632                 :            : 
     633                 :       3314 :           if (gimple_code (stmt) != GIMPLE_ASSIGN)
     634                 :            :             {
     635                 :        569 :               if (gimple_vuse (stmt)
     636                 :        569 :                   || (is_gimple_call (stmt)
     637                 :          0 :                       && !(gimple_call_flags (stmt) & ECF_CONST)))
     638                 :         55 :                 *no_other_refs = false;
     639                 :        569 :               continue;
     640                 :            :             }
     641                 :            : 
     642                 :       2745 :           if (! gimple_vuse (stmt))
     643                 :       1708 :             continue;
     644                 :            : 
     645                 :       1037 :           lhs = gimple_assign_lhs (stmt);
     646                 :       1037 :           rhs = gimple_assign_rhs1 (stmt);
     647                 :            : 
     648                 :       1037 :           if (REFERENCE_CLASS_P (rhs))
     649                 :            :             {
     650                 :        245 :             *no_other_refs &= gather_memory_references_ref (loop, &refs,
     651                 :        245 :                                                             rhs, false, stmt);
     652                 :        245 :             *ref_count += 1;
     653                 :            :             }
     654                 :       1037 :           if (REFERENCE_CLASS_P (lhs))
     655                 :            :             {
     656                 :        253 :             *no_other_refs &= gather_memory_references_ref (loop, &refs,
     657                 :        253 :                                                             lhs, true, stmt);
     658                 :        253 :             *ref_count += 1;
     659                 :            :             }
     660                 :            :         }
     661                 :            :     }
     662                 :        104 :   free (body);
     663                 :            : 
     664                 :        104 :   return refs;
     665                 :            : }
     666                 :            : 
     667                 :            : /* Prune the prefetch candidate REF using the self-reuse.  */
     668                 :            : 
     669                 :            : static void
     670                 :        138 : prune_ref_by_self_reuse (struct mem_ref *ref)
     671                 :            : {
     672                 :        138 :   HOST_WIDE_INT step;
     673                 :        138 :   bool backward;
     674                 :            : 
     675                 :            :   /* If the step size is non constant, we cannot calculate prefetch_mod.  */
     676                 :        138 :   if (!cst_and_fits_in_hwi (ref->group->step))
     677                 :            :     return;
     678                 :            : 
     679                 :         90 :   step = int_cst_value (ref->group->step);
     680                 :            : 
     681                 :         90 :   backward = step < 0;
     682                 :            : 
     683                 :         90 :   if (step == 0)
     684                 :            :     {
     685                 :            :       /* Prefetch references to invariant address just once.  */
     686                 :          3 :       ref->prefetch_before = 1;
     687                 :          3 :       return;
     688                 :            :     }
     689                 :            : 
     690                 :         87 :   if (backward)
     691                 :            :     step = -step;
     692                 :            : 
     693                 :         87 :   if (step > PREFETCH_BLOCK)
     694                 :            :     return;
     695                 :            : 
     696                 :         84 :   if ((backward && HAVE_BACKWARD_PREFETCH)
     697                 :            :       || (!backward && HAVE_FORWARD_PREFETCH))
     698                 :            :     {
     699                 :            :       ref->prefetch_before = 1;
     700                 :            :       return;
     701                 :            :     }
     702                 :            : 
     703                 :         84 :   ref->prefetch_mod = PREFETCH_BLOCK / step;
     704                 :            : }
     705                 :            : 
     706                 :            : /* Divides X by BY, rounding down.  */
     707                 :            : 
     708                 :            : static HOST_WIDE_INT
     709                 :         13 : ddown (HOST_WIDE_INT x, unsigned HOST_WIDE_INT by)
     710                 :            : {
     711                 :         13 :   gcc_assert (by > 0);
     712                 :            : 
     713                 :         13 :   if (x >= 0)
     714                 :         13 :     return x / (HOST_WIDE_INT) by;
     715                 :            :   else
     716                 :          0 :     return (x + (HOST_WIDE_INT) by - 1) / (HOST_WIDE_INT) by;
     717                 :            : }
     718                 :            : 
     719                 :            : /* Given a CACHE_LINE_SIZE and two inductive memory references
     720                 :            :    with a common STEP greater than CACHE_LINE_SIZE and an address
     721                 :            :    difference DELTA, compute the probability that they will fall
     722                 :            :    in different cache lines.  Return true if the computed miss rate
     723                 :            :    is not greater than the ACCEPTABLE_MISS_RATE.  DISTINCT_ITERS is the
     724                 :            :    number of distinct iterations after which the pattern repeats itself.
     725                 :            :    ALIGN_UNIT is the unit of alignment in bytes.  */
     726                 :            : 
     727                 :            : static bool
     728                 :          0 : is_miss_rate_acceptable (unsigned HOST_WIDE_INT cache_line_size,
     729                 :            :                    HOST_WIDE_INT step, HOST_WIDE_INT delta,
     730                 :            :                    unsigned HOST_WIDE_INT distinct_iters,
     731                 :            :                    int align_unit)
     732                 :            : {
     733                 :          0 :   unsigned align, iter;
     734                 :          0 :   int total_positions, miss_positions, max_allowed_miss_positions;
     735                 :          0 :   int address1, address2, cache_line1, cache_line2;
     736                 :            : 
     737                 :            :   /* It always misses if delta is greater than or equal to the cache
     738                 :            :      line size.  */
     739                 :          0 :   if (delta >= (HOST_WIDE_INT) cache_line_size)
     740                 :            :     return false;
     741                 :            : 
     742                 :          0 :   miss_positions = 0;
     743                 :          0 :   total_positions = (cache_line_size / align_unit) * distinct_iters;
     744                 :          0 :   max_allowed_miss_positions = (ACCEPTABLE_MISS_RATE * total_positions) / 1000;
     745                 :            : 
     746                 :            :   /* Iterate through all possible alignments of the first
     747                 :            :      memory reference within its cache line.  */
     748                 :          0 :   for (align = 0; align < cache_line_size; align += align_unit)
     749                 :            : 
     750                 :            :     /* Iterate through all distinct iterations.  */
     751                 :          0 :     for (iter = 0; iter < distinct_iters; iter++)
     752                 :            :       {
     753                 :          0 :         address1 = align + step * iter;
     754                 :          0 :         address2 = address1 + delta;
     755                 :          0 :         cache_line1 = address1 / cache_line_size;
     756                 :          0 :         cache_line2 = address2 / cache_line_size;
     757                 :          0 :         if (cache_line1 != cache_line2)
     758                 :            :           {
     759                 :          0 :             miss_positions += 1;
     760                 :          0 :             if (miss_positions > max_allowed_miss_positions)
     761                 :            :               return false;
     762                 :            :           }
     763                 :            :       }
     764                 :            :   return true;
     765                 :            : }
     766                 :            : 
     767                 :            : /* Prune the prefetch candidate REF using the reuse with BY.
     768                 :            :    If BY_IS_BEFORE is true, BY is before REF in the loop.  */
     769                 :            : 
     770                 :            : static void
     771                 :         24 : prune_ref_by_group_reuse (struct mem_ref *ref, struct mem_ref *by,
     772                 :            :                           bool by_is_before)
     773                 :            : {
     774                 :         24 :   HOST_WIDE_INT step;
     775                 :         24 :   bool backward;
     776                 :         24 :   HOST_WIDE_INT delta_r = ref->delta, delta_b = by->delta;
     777                 :         24 :   HOST_WIDE_INT delta = delta_b - delta_r;
     778                 :         24 :   HOST_WIDE_INT hit_from;
     779                 :         24 :   unsigned HOST_WIDE_INT prefetch_before, prefetch_block;
     780                 :         24 :   HOST_WIDE_INT reduced_step;
     781                 :         24 :   unsigned HOST_WIDE_INT reduced_prefetch_block;
     782                 :         24 :   tree ref_type;
     783                 :         24 :   int align_unit;
     784                 :            : 
     785                 :            :   /* If the step is non constant we cannot calculate prefetch_before.  */
     786                 :         24 :   if (!cst_and_fits_in_hwi (ref->group->step)) {
     787                 :            :     return;
     788                 :            :   }
     789                 :            : 
     790                 :         22 :   step = int_cst_value (ref->group->step);
     791                 :            : 
     792                 :         22 :   backward = step < 0;
     793                 :            : 
     794                 :            : 
     795                 :         22 :   if (delta == 0)
     796                 :            :     {
     797                 :            :       /* If the references has the same address, only prefetch the
     798                 :            :          former.  */
     799                 :          0 :       if (by_is_before)
     800                 :          0 :         ref->prefetch_before = 0;
     801                 :            : 
     802                 :          0 :       return;
     803                 :            :     }
     804                 :            : 
     805                 :         22 :   if (!step)
     806                 :            :     {
     807                 :            :       /* If the reference addresses are invariant and fall into the
     808                 :            :          same cache line, prefetch just the first one.  */
     809                 :          6 :       if (!by_is_before)
     810                 :            :         return;
     811                 :            : 
     812                 :          6 :       if (ddown (ref->delta, PREFETCH_BLOCK)
     813                 :          3 :           != ddown (by->delta, PREFETCH_BLOCK))
     814                 :            :         return;
     815                 :            : 
     816                 :          3 :       ref->prefetch_before = 0;
     817                 :          3 :       return;
     818                 :            :     }
     819                 :            : 
     820                 :            :   /* Only prune the reference that is behind in the array.  */
     821                 :         16 :   if (backward)
     822                 :            :     {
     823                 :          0 :       if (delta > 0)
     824                 :            :         return;
     825                 :            : 
     826                 :            :       /* Transform the data so that we may assume that the accesses
     827                 :            :          are forward.  */
     828                 :          0 :       delta = - delta;
     829                 :          0 :       step = -step;
     830                 :          0 :       delta_r = PREFETCH_BLOCK - 1 - delta_r;
     831                 :          0 :       delta_b = PREFETCH_BLOCK - 1 - delta_b;
     832                 :            :     }
     833                 :            :   else
     834                 :            :     {
     835                 :         16 :       if (delta < 0)
     836                 :            :         return;
     837                 :            :     }
     838                 :            : 
     839                 :            :   /* Check whether the two references are likely to hit the same cache
     840                 :            :      line, and how distant the iterations in that it occurs are from
     841                 :            :      each other.  */
     842                 :            : 
     843                 :          7 :   if (step <= PREFETCH_BLOCK)
     844                 :            :     {
     845                 :            :       /* The accesses are sure to meet.  Let us check when.  */
     846                 :          7 :       hit_from = ddown (delta_b, PREFETCH_BLOCK) * PREFETCH_BLOCK;
     847                 :          7 :       prefetch_before = (hit_from - delta_r + step - 1) / step;
     848                 :            : 
     849                 :            :       /* Do not reduce prefetch_before if we meet beyond cache size.  */
     850                 :         14 :       if (prefetch_before > absu_hwi (L2_CACHE_SIZE_BYTES / step))
     851                 :          0 :         prefetch_before = PREFETCH_ALL;
     852                 :          7 :       if (prefetch_before < ref->prefetch_before)
     853                 :          7 :         ref->prefetch_before = prefetch_before;
     854                 :            : 
     855                 :          7 :       return;
     856                 :            :     }
     857                 :            : 
     858                 :            :   /* A more complicated case with step > prefetch_block.  First reduce
     859                 :            :      the ratio between the step and the cache line size to its simplest
     860                 :            :      terms.  The resulting denominator will then represent the number of
     861                 :            :      distinct iterations after which each address will go back to its
     862                 :            :      initial location within the cache line.  This computation assumes
     863                 :            :      that PREFETCH_BLOCK is a power of two.  */
     864                 :          0 :   prefetch_block = PREFETCH_BLOCK;
     865                 :          0 :   reduced_prefetch_block = prefetch_block;
     866                 :          0 :   reduced_step = step;
     867                 :          0 :   while ((reduced_step & 1) == 0
     868                 :          0 :          && reduced_prefetch_block > 1)
     869                 :            :     {
     870                 :          0 :       reduced_step >>= 1;
     871                 :          0 :       reduced_prefetch_block >>= 1;
     872                 :            :     }
     873                 :            : 
     874                 :          0 :   prefetch_before = delta / step;
     875                 :          0 :   delta %= step;
     876                 :          0 :   ref_type = TREE_TYPE (ref->mem);
     877                 :          0 :   align_unit = TYPE_ALIGN (ref_type) / 8;
     878                 :          0 :   if (is_miss_rate_acceptable (prefetch_block, step, delta,
     879                 :            :                                reduced_prefetch_block, align_unit))
     880                 :            :     {
     881                 :            :       /* Do not reduce prefetch_before if we meet beyond cache size.  */
     882                 :          0 :       if (prefetch_before > L2_CACHE_SIZE_BYTES / PREFETCH_BLOCK)
     883                 :          0 :         prefetch_before = PREFETCH_ALL;
     884                 :          0 :       if (prefetch_before < ref->prefetch_before)
     885                 :          0 :         ref->prefetch_before = prefetch_before;
     886                 :            : 
     887                 :          0 :       return;
     888                 :            :     }
     889                 :            : 
     890                 :            :   /* Try also the following iteration.  */
     891                 :          0 :   prefetch_before++;
     892                 :          0 :   delta = step - delta;
     893                 :          0 :   if (is_miss_rate_acceptable (prefetch_block, step, delta,
     894                 :            :                                reduced_prefetch_block, align_unit))
     895                 :            :     {
     896                 :          0 :       if (prefetch_before < ref->prefetch_before)
     897                 :          0 :         ref->prefetch_before = prefetch_before;
     898                 :            : 
     899                 :          0 :       return;
     900                 :            :     }
     901                 :            : 
     902                 :            :   /* The ref probably does not reuse by.  */
     903                 :            :   return;
     904                 :            : }
     905                 :            : 
     906                 :            : /* Prune the prefetch candidate REF using the reuses with other references
     907                 :            :    in REFS.  */
     908                 :            : 
     909                 :            : static void
     910                 :        138 : prune_ref_by_reuse (struct mem_ref *ref, struct mem_ref *refs)
     911                 :            : {
     912                 :        138 :   struct mem_ref *prune_by;
     913                 :        138 :   bool before = true;
     914                 :            : 
     915                 :        138 :   prune_ref_by_self_reuse (ref);
     916                 :            : 
     917                 :        302 :   for (prune_by = refs; prune_by; prune_by = prune_by->next)
     918                 :            :     {
     919                 :        164 :       if (prune_by == ref)
     920                 :            :         {
     921                 :        138 :           before = false;
     922                 :        138 :           continue;
     923                 :            :         }
     924                 :            : 
     925                 :         26 :       if (!WRITE_CAN_USE_READ_PREFETCH
     926                 :            :           && ref->write_p
     927                 :            :           && !prune_by->write_p)
     928                 :            :         continue;
     929                 :         26 :       if (!READ_CAN_USE_WRITE_PREFETCH
     930                 :         26 :           && !ref->write_p
     931                 :         20 :           && prune_by->write_p)
     932                 :          2 :         continue;
     933                 :            : 
     934                 :         24 :       prune_ref_by_group_reuse (ref, prune_by, before);
     935                 :            :     }
     936                 :        138 : }
     937                 :            : 
     938                 :            : /* Prune the prefetch candidates in GROUP using the reuse analysis.  */
     939                 :            : 
     940                 :            : static void
     941                 :        126 : prune_group_by_reuse (struct mem_ref_group *group)
     942                 :            : {
     943                 :        126 :   struct mem_ref *ref_pruned;
     944                 :            : 
     945                 :        264 :   for (ref_pruned = group->refs; ref_pruned; ref_pruned = ref_pruned->next)
     946                 :            :     {
     947                 :        138 :       prune_ref_by_reuse (ref_pruned, group->refs);
     948                 :            : 
     949                 :        138 :       if (dump_file && (dump_flags & TDF_DETAILS))
     950                 :            :         {
     951                 :         26 :           dump_mem_ref (dump_file, ref_pruned);
     952                 :            : 
     953                 :         26 :           if (ref_pruned->prefetch_before == PREFETCH_ALL
     954                 :         25 :               && ref_pruned->prefetch_mod == 1)
     955                 :          5 :             fprintf (dump_file, " no restrictions");
     956                 :         21 :           else if (ref_pruned->prefetch_before == 0)
     957                 :          1 :             fprintf (dump_file, " do not prefetch");
     958                 :         20 :           else if (ref_pruned->prefetch_before <= ref_pruned->prefetch_mod)
     959                 :          0 :             fprintf (dump_file, " prefetch once");
     960                 :            :           else
     961                 :            :             {
     962                 :         20 :               if (ref_pruned->prefetch_before != PREFETCH_ALL)
     963                 :            :                 {
     964                 :          0 :                   fprintf (dump_file, " prefetch before ");
     965                 :          0 :                   fprintf (dump_file, HOST_WIDE_INT_PRINT_DEC,
     966                 :            :                            ref_pruned->prefetch_before);
     967                 :            :                 }
     968                 :         20 :               if (ref_pruned->prefetch_mod != 1)
     969                 :            :                 {
     970                 :         20 :                   fprintf (dump_file, " prefetch mod ");
     971                 :         20 :                   fprintf (dump_file, HOST_WIDE_INT_PRINT_DEC,
     972                 :            :                            ref_pruned->prefetch_mod);
     973                 :            :                 }
     974                 :            :             }
     975                 :         26 :           fprintf (dump_file, "\n");
     976                 :            :         }
     977                 :            :     }
     978                 :        126 : }
     979                 :            : 
     980                 :            : /* Prune the list of prefetch candidates GROUPS using the reuse analysis.  */
     981                 :            : 
     982                 :            : static void
     983                 :          0 : prune_by_reuse (struct mem_ref_group *groups)
     984                 :            : {
     985                 :        193 :   for (; groups; groups = groups->next)
     986                 :        126 :     prune_group_by_reuse (groups);
     987                 :          0 : }
     988                 :            : 
     989                 :            : /* Returns true if we should issue prefetch for REF.  */
     990                 :            : 
     991                 :            : static bool
     992                 :        452 : should_issue_prefetch_p (struct mem_ref *ref)
     993                 :            : {
     994                 :            :   /* Do we want to issue prefetches for non-constant strides?  */
     995                 :        452 :   if (!cst_and_fits_in_hwi (ref->group->step)
     996                 :        452 :       && param_prefetch_dynamic_strides == 0)
     997                 :            :     {
     998                 :          0 :       if (dump_file && (dump_flags & TDF_DETAILS))
     999                 :          0 :         fprintf (dump_file,
    1000                 :            :                  "Skipping non-constant step for reference %u:%u\n",
    1001                 :          0 :                  ref->group->uid, ref->uid);
    1002                 :          0 :       return false;
    1003                 :            :     }
    1004                 :            : 
    1005                 :            :   /* Some processors may have a hardware prefetcher that may conflict with
    1006                 :            :      prefetch hints for a range of strides.  Make sure we don't issue
    1007                 :            :      prefetches for such cases if the stride is within this particular
    1008                 :            :      range.  */
    1009                 :        452 :   if (cst_and_fits_in_hwi (ref->group->step)
    1010                 :        452 :       && abs_hwi (int_cst_value (ref->group->step))
    1011                 :        303 :           < (HOST_WIDE_INT) param_prefetch_minimum_stride)
    1012                 :            :     {
    1013                 :          0 :       if (dump_file && (dump_flags & TDF_DETAILS))
    1014                 :          0 :         fprintf (dump_file,
    1015                 :            :                  "Step for reference %u:%u (" HOST_WIDE_INT_PRINT_DEC
    1016                 :            :                  ") is less than the mininum required stride of %d\n",
    1017                 :          0 :                  ref->group->uid, ref->uid, int_cst_value (ref->group->step),
    1018                 :            :                  param_prefetch_minimum_stride);
    1019                 :          0 :       return false;
    1020                 :            :     }
    1021                 :            : 
    1022                 :            :   /* For now do not issue prefetches for only first few of the
    1023                 :            :      iterations.  */
    1024                 :        452 :   if (ref->prefetch_before != PREFETCH_ALL)
    1025                 :            :     {
    1026                 :         28 :       if (dump_file && (dump_flags & TDF_DETAILS))
    1027                 :          4 :         fprintf (dump_file, "Ignoring reference %u:%u due to prefetch_before\n",
    1028                 :          4 :                  ref->group->uid, ref->uid);
    1029                 :         28 :       return false;
    1030                 :            :     }
    1031                 :            : 
    1032                 :            :   /* Do not prefetch nontemporal stores.  */
    1033                 :        424 :   if (ref->storent_p)
    1034                 :            :     {
    1035                 :          2 :       if (dump_file && (dump_flags & TDF_DETAILS))
    1036                 :          2 :         fprintf (dump_file, "Ignoring nontemporal store reference %u:%u\n", ref->group->uid, ref->uid);
    1037                 :          2 :       return false;
    1038                 :            :     }
    1039                 :            : 
    1040                 :            :   return true;
    1041                 :            : }
    1042                 :            : 
    1043                 :            : /* Decide which of the prefetch candidates in GROUPS to prefetch.
    1044                 :            :    AHEAD is the number of iterations to prefetch ahead (which corresponds
    1045                 :            :    to the number of simultaneous instances of one prefetch running at a
    1046                 :            :    time).  UNROLL_FACTOR is the factor by that the loop is going to be
    1047                 :            :    unrolled.  Returns true if there is anything to prefetch.  */
    1048                 :            : 
    1049                 :            : static bool
    1050                 :         63 : schedule_prefetches (struct mem_ref_group *groups, unsigned unroll_factor,
    1051                 :            :                      unsigned ahead)
    1052                 :            : {
    1053                 :         63 :   unsigned remaining_prefetch_slots, n_prefetches, prefetch_slots;
    1054                 :         63 :   unsigned slots_per_prefetch;
    1055                 :         63 :   struct mem_ref *ref;
    1056                 :         63 :   bool any = false;
    1057                 :            : 
    1058                 :            :   /* At most param_simultaneous_prefetches should be running
    1059                 :            :      at the same time.  */
    1060                 :         63 :   remaining_prefetch_slots = param_simultaneous_prefetches;
    1061                 :            : 
    1062                 :            :   /* The prefetch will run for AHEAD iterations of the original loop, i.e.,
    1063                 :            :      AHEAD / UNROLL_FACTOR iterations of the unrolled loop.  In each iteration,
    1064                 :            :      it will need a prefetch slot.  */
    1065                 :         63 :   slots_per_prefetch = (ahead + unroll_factor / 2) / unroll_factor;
    1066                 :         63 :   if (dump_file && (dump_flags & TDF_DETAILS))
    1067                 :         15 :     fprintf (dump_file, "Each prefetch instruction takes %u prefetch slots.\n",
    1068                 :            :              slots_per_prefetch);
    1069                 :            : 
    1070                 :            :   /* For now we just take memory references one by one and issue
    1071                 :            :      prefetches for as many as possible.  The groups are sorted
    1072                 :            :      starting with the largest step, since the references with
    1073                 :            :      large step are more likely to cause many cache misses.  */
    1074                 :            : 
    1075                 :        178 :   for (; groups; groups = groups->next)
    1076                 :        241 :     for (ref = groups->refs; ref; ref = ref->next)
    1077                 :            :       {
    1078                 :        126 :         if (!should_issue_prefetch_p (ref))
    1079                 :          9 :           continue;
    1080                 :            : 
    1081                 :            :         /* The loop is far from being sufficiently unrolled for this
    1082                 :            :            prefetch.  Do not generate prefetch to avoid many redudant
    1083                 :            :            prefetches.  */
    1084                 :        117 :         if (ref->prefetch_mod / unroll_factor > PREFETCH_MOD_TO_UNROLL_FACTOR_RATIO)
    1085                 :          3 :           continue;
    1086                 :            : 
    1087                 :            :         /* If we need to prefetch the reference each PREFETCH_MOD iterations,
    1088                 :            :            and we unroll the loop UNROLL_FACTOR times, we need to insert
    1089                 :            :            ceil (UNROLL_FACTOR / PREFETCH_MOD) instructions in each
    1090                 :            :            iteration.  */
    1091                 :        114 :         n_prefetches = ((unroll_factor + ref->prefetch_mod - 1)
    1092                 :        114 :                         / ref->prefetch_mod);
    1093                 :        114 :         prefetch_slots = n_prefetches * slots_per_prefetch;
    1094                 :            : 
    1095                 :            :         /* If more than half of the prefetches would be lost anyway, do not
    1096                 :            :            issue the prefetch.  */
    1097                 :        114 :         if (2 * remaining_prefetch_slots < prefetch_slots)
    1098                 :          3 :           continue;
    1099                 :            : 
    1100                 :            :         /* Stop prefetching if debug counter is activated.  */
    1101                 :        111 :         if (!dbg_cnt (prefetch))
    1102                 :          0 :           continue;
    1103                 :            : 
    1104                 :        111 :         ref->issue_prefetch_p = true;
    1105                 :        111 :         if (dump_file && (dump_flags & TDF_DETAILS))
    1106                 :         20 :           fprintf (dump_file, "Decided to issue prefetch for reference %u:%u\n",
    1107                 :         20 :                    ref->group->uid, ref->uid);
    1108                 :            : 
    1109                 :        111 :         if (remaining_prefetch_slots <= prefetch_slots)
    1110                 :            :           return true;
    1111                 :        110 :         remaining_prefetch_slots -= prefetch_slots;
    1112                 :        110 :         any = true;
    1113                 :            :       }
    1114                 :            : 
    1115                 :            :   return any;
    1116                 :            : }
    1117                 :            : 
    1118                 :            : /* Return TRUE if no prefetch is going to be generated in the given
    1119                 :            :    GROUPS.  */
    1120                 :            : 
    1121                 :            : static bool
    1122                 :         67 : nothing_to_prefetch_p (struct mem_ref_group *groups)
    1123                 :            : {
    1124                 :         68 :   struct mem_ref *ref;
    1125                 :            : 
    1126                 :         68 :   for (; groups; groups = groups->next)
    1127                 :         73 :     for (ref = groups->refs; ref; ref = ref->next)
    1128                 :         72 :       if (should_issue_prefetch_p (ref))
    1129                 :            :         return false;
    1130                 :            : 
    1131                 :            :   return true;
    1132                 :            : }
    1133                 :            : 
    1134                 :            : /* Estimate the number of prefetches in the given GROUPS.
    1135                 :            :    UNROLL_FACTOR is the factor by which LOOP was unrolled.  */
    1136                 :            : 
    1137                 :            : static int
    1138                 :         65 : estimate_prefetch_count (struct mem_ref_group *groups, unsigned unroll_factor)
    1139                 :            : {
    1140                 :         65 :   struct mem_ref *ref;
    1141                 :         65 :   unsigned n_prefetches;
    1142                 :         65 :   int prefetch_count = 0;
    1143                 :            : 
    1144                 :        190 :   for (; groups; groups = groups->next)
    1145                 :        260 :     for (ref = groups->refs; ref; ref = ref->next)
    1146                 :        135 :       if (should_issue_prefetch_p (ref))
    1147                 :            :         {
    1148                 :        128 :           n_prefetches = ((unroll_factor + ref->prefetch_mod - 1)
    1149                 :        128 :                           / ref->prefetch_mod);
    1150                 :        128 :           prefetch_count += n_prefetches;
    1151                 :            :         }
    1152                 :            : 
    1153                 :         65 :   return prefetch_count;
    1154                 :            : }
    1155                 :            : 
    1156                 :            : /* Issue prefetches for the reference REF into loop as decided before.
    1157                 :            :    HEAD is the number of iterations to prefetch ahead.  UNROLL_FACTOR
    1158                 :            :    is the factor by which LOOP was unrolled.  */
    1159                 :            : 
    1160                 :            : static void
    1161                 :        111 : issue_prefetch_ref (struct mem_ref *ref, unsigned unroll_factor, unsigned ahead)
    1162                 :            : {
    1163                 :        111 :   HOST_WIDE_INT delta;
    1164                 :        111 :   tree addr, addr_base, write_p, local, forward;
    1165                 :        111 :   gcall *prefetch;
    1166                 :        111 :   gimple_stmt_iterator bsi;
    1167                 :        111 :   unsigned n_prefetches, ap;
    1168                 :        111 :   bool nontemporal = ref->reuse_distance >= L2_CACHE_SIZE_BYTES;
    1169                 :            : 
    1170                 :        111 :   if (dump_file && (dump_flags & TDF_DETAILS))
    1171                 :         20 :     fprintf (dump_file, "Issued%s prefetch for reference %u:%u.\n",
    1172                 :            :              nontemporal ? " nontemporal" : "",
    1173                 :         20 :              ref->group->uid, ref->uid);
    1174                 :            : 
    1175                 :        111 :   bsi = gsi_for_stmt (ref->stmt);
    1176                 :            : 
    1177                 :        111 :   n_prefetches = ((unroll_factor + ref->prefetch_mod - 1)
    1178                 :        111 :                   / ref->prefetch_mod);
    1179                 :        111 :   addr_base = build_fold_addr_expr_with_type (ref->mem, ptr_type_node);
    1180                 :        111 :   addr_base = force_gimple_operand_gsi (&bsi, unshare_expr (addr_base),
    1181                 :            :                                         true, NULL, true, GSI_SAME_STMT);
    1182                 :        111 :   write_p = ref->write_p ? integer_one_node : integer_zero_node;
    1183                 :        111 :   local = nontemporal ? integer_zero_node : integer_three_node;
    1184                 :            : 
    1185                 :        222 :   for (ap = 0; ap < n_prefetches; ap++)
    1186                 :            :     {
    1187                 :        111 :       if (cst_and_fits_in_hwi (ref->group->step))
    1188                 :            :         {
    1189                 :            :           /* Determine the address to prefetch.  */
    1190                 :        134 :           delta = (ahead + ap * ref->prefetch_mod) *
    1191                 :         67 :                    int_cst_value (ref->group->step);
    1192                 :         67 :           addr = fold_build_pointer_plus_hwi (addr_base, delta);
    1193                 :         67 :           addr = force_gimple_operand_gsi (&bsi, unshare_expr (addr), true,
    1194                 :            :                                            NULL, true, GSI_SAME_STMT);
    1195                 :            :         }
    1196                 :            :       else
    1197                 :            :         {
    1198                 :            :           /* The step size is non-constant but loop-invariant.  We use the
    1199                 :            :              heuristic to simply prefetch ahead iterations ahead.  */
    1200                 :         44 :           forward = fold_build2 (MULT_EXPR, sizetype,
    1201                 :            :                                  fold_convert (sizetype, ref->group->step),
    1202                 :            :                                  fold_convert (sizetype, size_int (ahead)));
    1203                 :         44 :           addr = fold_build_pointer_plus (addr_base, forward);
    1204                 :         44 :           addr = force_gimple_operand_gsi (&bsi, unshare_expr (addr), true,
    1205                 :            :                                            NULL, true, GSI_SAME_STMT);
    1206                 :            :       }
    1207                 :            : 
    1208                 :        111 :       if (addr_base != addr
    1209                 :        109 :           && TREE_CODE (addr_base) == SSA_NAME
    1210                 :        109 :           && TREE_CODE (addr) == SSA_NAME)
    1211                 :            :         {
    1212                 :        109 :           duplicate_ssa_name_ptr_info (addr, SSA_NAME_PTR_INFO (addr_base));
    1213                 :            :           /* As this isn't a plain copy we have to reset alignment
    1214                 :            :              information.  */
    1215                 :        109 :           if (SSA_NAME_PTR_INFO (addr))
    1216                 :         52 :             mark_ptr_info_alignment_unknown (SSA_NAME_PTR_INFO (addr));
    1217                 :            :         }
    1218                 :            : 
    1219                 :            :       /* Create the prefetch instruction.  */
    1220                 :        111 :       prefetch = gimple_build_call (builtin_decl_explicit (BUILT_IN_PREFETCH),
    1221                 :            :                                     3, addr, write_p, local);
    1222                 :        111 :       gsi_insert_before (&bsi, prefetch, GSI_SAME_STMT);
    1223                 :            :     }
    1224                 :        111 : }
    1225                 :            : 
    1226                 :            : /* Issue prefetches for the references in GROUPS into loop as decided before.
    1227                 :            :    HEAD is the number of iterations to prefetch ahead.  UNROLL_FACTOR is the
    1228                 :            :    factor by that LOOP was unrolled.  */
    1229                 :            : 
    1230                 :            : static void
    1231                 :         61 : issue_prefetches (struct mem_ref_group *groups,
    1232                 :            :                   unsigned unroll_factor, unsigned ahead)
    1233                 :            : {
    1234                 :        178 :   struct mem_ref *ref;
    1235                 :            : 
    1236                 :        178 :   for (; groups; groups = groups->next)
    1237                 :        244 :     for (ref = groups->refs; ref; ref = ref->next)
    1238                 :        127 :       if (ref->issue_prefetch_p)
    1239                 :        111 :         issue_prefetch_ref (ref, unroll_factor, ahead);
    1240                 :         61 : }
    1241                 :            : 
    1242                 :            : /* Returns true if REF is a memory write for that a nontemporal store insn
    1243                 :            :    can be used.  */
    1244                 :            : 
    1245                 :            : static bool
    1246                 :        127 : nontemporal_store_p (struct mem_ref *ref)
    1247                 :            : {
    1248                 :        127 :   machine_mode mode;
    1249                 :        127 :   enum insn_code code;
    1250                 :            : 
    1251                 :            :   /* REF must be a write that is not reused.  We require it to be independent
    1252                 :            :      on all other memory references in the loop, as the nontemporal stores may
    1253                 :            :      be reordered with respect to other memory references.  */
    1254                 :        127 :   if (!ref->write_p
    1255                 :        127 :       || !ref->independent_p
    1256                 :         17 :       || ref->reuse_distance < L2_CACHE_SIZE_BYTES)
    1257                 :            :     return false;
    1258                 :            : 
    1259                 :            :   /* Check that we have the storent instruction for the mode.  */
    1260                 :          2 :   mode = TYPE_MODE (TREE_TYPE (ref->mem));
    1261                 :          2 :   if (mode == BLKmode)
    1262                 :            :     return false;
    1263                 :            : 
    1264                 :          2 :   code = optab_handler (storent_optab, mode);
    1265                 :          2 :   return code != CODE_FOR_nothing;
    1266                 :            : }
    1267                 :            : 
    1268                 :            : /* If REF is a nontemporal store, we mark the corresponding modify statement
    1269                 :            :    and return true.  Otherwise, we return false.  */
    1270                 :            : 
    1271                 :            : static bool
    1272                 :        127 : mark_nontemporal_store (struct mem_ref *ref)
    1273                 :            : {
    1274                 :        127 :   if (!nontemporal_store_p (ref))
    1275                 :            :     return false;
    1276                 :            : 
    1277                 :          2 :   if (dump_file && (dump_flags & TDF_DETAILS))
    1278                 :          2 :     fprintf (dump_file, "Marked reference %u:%u as a nontemporal store.\n",
    1279                 :          2 :              ref->group->uid, ref->uid);
    1280                 :            : 
    1281                 :          2 :   gimple_assign_set_nontemporal_move (ref->stmt, true);
    1282                 :          2 :   ref->storent_p = true;
    1283                 :            : 
    1284                 :          2 :   return true;
    1285                 :            : }
    1286                 :            : 
    1287                 :            : /* Issue a memory fence instruction after LOOP.  */
    1288                 :            : 
    1289                 :            : static void
    1290                 :          2 : emit_mfence_after_loop (class loop *loop)
    1291                 :            : {
    1292                 :          2 :   vec<edge> exits = get_loop_exit_edges (loop);
    1293                 :          2 :   edge exit;
    1294                 :          2 :   gcall *call;
    1295                 :          2 :   gimple_stmt_iterator bsi;
    1296                 :          2 :   unsigned i;
    1297                 :            : 
    1298                 :          4 :   FOR_EACH_VEC_ELT (exits, i, exit)
    1299                 :            :     {
    1300                 :          2 :       call = gimple_build_call (FENCE_FOLLOWING_MOVNT, 0);
    1301                 :            : 
    1302                 :          2 :       if (!single_pred_p (exit->dest)
    1303                 :            :           /* If possible, we prefer not to insert the fence on other paths
    1304                 :            :              in cfg.  */
    1305                 :          2 :           && !(exit->flags & EDGE_ABNORMAL))
    1306                 :          0 :         split_loop_exit_edge (exit);
    1307                 :          2 :       bsi = gsi_after_labels (exit->dest);
    1308                 :            : 
    1309                 :          2 :       gsi_insert_before (&bsi, call, GSI_NEW_STMT);
    1310                 :            :     }
    1311                 :            : 
    1312                 :          2 :   exits.release ();
    1313                 :          2 :   update_ssa (TODO_update_ssa_only_virtuals);
    1314                 :          2 : }
    1315                 :            : 
    1316                 :            : /* Returns true if we can use storent in loop, false otherwise.  */
    1317                 :            : 
    1318                 :            : static bool
    1319                 :         63 : may_use_storent_in_loop_p (class loop *loop)
    1320                 :            : {
    1321                 :         63 :   bool ret = true;
    1322                 :            : 
    1323                 :         63 :   if (loop->inner != NULL)
    1324                 :            :     return false;
    1325                 :            : 
    1326                 :            :   /* If we must issue a mfence insn after using storent, check that there
    1327                 :            :      is a suitable place for it at each of the loop exits.  */
    1328                 :         61 :   if (FENCE_FOLLOWING_MOVNT != NULL_TREE)
    1329                 :            :     {
    1330                 :         61 :       vec<edge> exits = get_loop_exit_edges (loop);
    1331                 :         61 :       unsigned i;
    1332                 :         61 :       edge exit;
    1333                 :            : 
    1334                 :        102 :       FOR_EACH_VEC_ELT (exits, i, exit)
    1335                 :         41 :         if ((exit->flags & EDGE_ABNORMAL)
    1336                 :          0 :             && exit->dest == EXIT_BLOCK_PTR_FOR_FN (cfun))
    1337                 :          0 :           ret = false;
    1338                 :            : 
    1339                 :         61 :       exits.release ();
    1340                 :            :     }
    1341                 :            : 
    1342                 :            :   return ret;
    1343                 :            : }
    1344                 :            : 
    1345                 :            : /* Marks nontemporal stores in LOOP.  GROUPS contains the description of memory
    1346                 :            :    references in the loop.  */
    1347                 :            : 
    1348                 :            : static void
    1349                 :         63 : mark_nontemporal_stores (class loop *loop, struct mem_ref_group *groups)
    1350                 :            : {
    1351                 :         63 :   struct mem_ref *ref;
    1352                 :         63 :   bool any = false;
    1353                 :            : 
    1354                 :         63 :   if (!may_use_storent_in_loop_p (loop))
    1355                 :            :     return;
    1356                 :            : 
    1357                 :        178 :   for (; groups; groups = groups->next)
    1358                 :        244 :     for (ref = groups->refs; ref; ref = ref->next)
    1359                 :        127 :       any |= mark_nontemporal_store (ref);
    1360                 :            : 
    1361                 :         61 :   if (any && FENCE_FOLLOWING_MOVNT != NULL_TREE)
    1362                 :          2 :     emit_mfence_after_loop (loop);
    1363                 :            : }
    1364                 :            : 
    1365                 :            : /* Determines whether we can profitably unroll LOOP FACTOR times, and if
    1366                 :            :    this is the case, fill in DESC by the description of number of
    1367                 :            :    iterations.  */
    1368                 :            : 
    1369                 :            : static bool
    1370                 :         49 : should_unroll_loop_p (class loop *loop, class tree_niter_desc *desc,
    1371                 :            :                       unsigned factor)
    1372                 :            : {
    1373                 :         49 :   if (!can_unroll_loop_p (loop, factor, desc))
    1374                 :            :     return false;
    1375                 :            : 
    1376                 :            :   /* We only consider loops without control flow for unrolling.  This is not
    1377                 :            :      a hard restriction -- tree_unroll_loop works with arbitrary loops
    1378                 :            :      as well; but the unrolling/prefetching is usually more profitable for
    1379                 :            :      loops consisting of a single basic block, and we want to limit the
    1380                 :            :      code growth.  */
    1381                 :         40 :   if (loop->num_nodes > 2)
    1382                 :          0 :     return false;
    1383                 :            : 
    1384                 :            :   return true;
    1385                 :            : }
    1386                 :            : 
    1387                 :            : /* Determine the coefficient by that unroll LOOP, from the information
    1388                 :            :    contained in the list of memory references REFS.  Description of
    1389                 :            :    number of iterations of LOOP is stored to DESC.  NINSNS is the number of
    1390                 :            :    insns of the LOOP.  EST_NITER is the estimated number of iterations of
    1391                 :            :    the loop, or -1 if no estimate is available.  */
    1392                 :            : 
    1393                 :            : static unsigned
    1394                 :         65 : determine_unroll_factor (class loop *loop, struct mem_ref_group *refs,
    1395                 :            :                          unsigned ninsns, class tree_niter_desc *desc,
    1396                 :            :                          HOST_WIDE_INT est_niter)
    1397                 :            : {
    1398                 :         65 :   unsigned upper_bound;
    1399                 :         65 :   unsigned nfactor, factor, mod_constraint;
    1400                 :         65 :   struct mem_ref_group *agp;
    1401                 :         65 :   struct mem_ref *ref;
    1402                 :            : 
    1403                 :            :   /* First check whether the loop is not too large to unroll.  We ignore
    1404                 :            :      PARAM_MAX_UNROLL_TIMES, because for small loops, it prevented us
    1405                 :            :      from unrolling them enough to make exactly one cache line covered by each
    1406                 :            :      iteration.  Also, the goal of PARAM_MAX_UNROLL_TIMES is to prevent
    1407                 :            :      us from unrolling the loops too many times in cases where we only expect
    1408                 :            :      gains from better scheduling and decreasing loop overhead, which is not
    1409                 :            :      the case here.  */
    1410                 :         65 :   upper_bound = param_max_unrolled_insns / ninsns;
    1411                 :            : 
    1412                 :            :   /* If we unrolled the loop more times than it iterates, the unrolled version
    1413                 :            :      of the loop would be never entered.  */
    1414                 :         65 :   if (est_niter >= 0 && est_niter < (HOST_WIDE_INT) upper_bound)
    1415                 :          0 :     upper_bound = est_niter;
    1416                 :            : 
    1417                 :         65 :   if (upper_bound <= 1)
    1418                 :            :     return 1;
    1419                 :            : 
    1420                 :            :   /* Choose the factor so that we may prefetch each cache just once,
    1421                 :            :      but bound the unrolling by UPPER_BOUND.  */
    1422                 :            :   factor = 1;
    1423                 :        158 :   for (agp = refs; agp; agp = agp->next)
    1424                 :        228 :     for (ref = agp->refs; ref; ref = ref->next)
    1425                 :        119 :       if (should_issue_prefetch_p (ref))
    1426                 :            :         {
    1427                 :        112 :           mod_constraint = ref->prefetch_mod;
    1428                 :        112 :           nfactor = least_common_multiple (mod_constraint, factor);
    1429                 :        112 :           if (nfactor <= upper_bound)
    1430                 :        103 :             factor = nfactor;
    1431                 :            :         }
    1432                 :            : 
    1433                 :         49 :   if (!should_unroll_loop_p (loop, desc, factor))
    1434                 :         10 :     return 1;
    1435                 :            : 
    1436                 :            :   return factor;
    1437                 :            : }
    1438                 :            : 
    1439                 :            : /* Returns the total volume of the memory references REFS, taking into account
    1440                 :            :    reuses in the innermost loop and cache line size.  TODO -- we should also
    1441                 :            :    take into account reuses across the iterations of the loops in the loop
    1442                 :            :    nest.  */
    1443                 :            : 
    1444                 :            : static unsigned
    1445                 :         63 : volume_of_references (struct mem_ref_group *refs)
    1446                 :            : {
    1447                 :          0 :   unsigned volume = 0;
    1448                 :          0 :   struct mem_ref_group *gr;
    1449                 :          0 :   struct mem_ref *ref;
    1450                 :            : 
    1451                 :        186 :   for (gr = refs; gr; gr = gr->next)
    1452                 :        256 :     for (ref = gr->refs; ref; ref = ref->next)
    1453                 :            :       {
    1454                 :            :         /* Almost always reuses another value?  */
    1455                 :        133 :         if (ref->prefetch_before != PREFETCH_ALL)
    1456                 :          7 :           continue;
    1457                 :            : 
    1458                 :            :         /* If several iterations access the same cache line, use the size of
    1459                 :            :            the line divided by this number.  Otherwise, a cache line is
    1460                 :            :            accessed in each iteration.  TODO -- in the latter case, we should
    1461                 :            :            take the size of the reference into account, rounding it up on cache
    1462                 :            :            line size multiple.  */
    1463                 :        126 :         volume += param_l1_cache_line_size / ref->prefetch_mod;
    1464                 :            :       }
    1465                 :          0 :   return volume;
    1466                 :            : }
    1467                 :            : 
    1468                 :            : /* Returns the volume of memory references accessed across VEC iterations of
    1469                 :            :    loops, whose sizes are described in the LOOP_SIZES array.  N is the number
    1470                 :            :    of the loops in the nest (length of VEC and LOOP_SIZES vectors).  */
    1471                 :            : 
    1472                 :            : static unsigned
    1473                 :        134 : volume_of_dist_vector (lambda_vector vec, unsigned *loop_sizes, unsigned n)
    1474                 :            : {
    1475                 :        134 :   unsigned i;
    1476                 :            : 
    1477                 :        282 :   for (i = 0; i < n; i++)
    1478                 :        152 :     if (vec[i] != 0)
    1479                 :            :       break;
    1480                 :            : 
    1481                 :        134 :   if (i == n)
    1482                 :            :     return 0;
    1483                 :            : 
    1484                 :          4 :   gcc_assert (vec[i] > 0);
    1485                 :            : 
    1486                 :            :   /* We ignore the parts of the distance vector in subloops, since usually
    1487                 :            :      the numbers of iterations are much smaller.  */
    1488                 :          4 :   return loop_sizes[i] * vec[i];
    1489                 :            : }
    1490                 :            : 
    1491                 :            : /* Add the steps of ACCESS_FN multiplied by STRIDE to the array STRIDE
    1492                 :            :    at the position corresponding to the loop of the step.  N is the depth
    1493                 :            :    of the considered loop nest, and, LOOP is its innermost loop.  */
    1494                 :            : 
    1495                 :            : static void
    1496                 :        143 : add_subscript_strides (tree access_fn, unsigned stride,
    1497                 :            :                        HOST_WIDE_INT *strides, unsigned n, class loop *loop)
    1498                 :            : {
    1499                 :        143 :   class loop *aloop;
    1500                 :        143 :   tree step;
    1501                 :        143 :   HOST_WIDE_INT astep;
    1502                 :        286 :   unsigned min_depth = loop_depth (loop) - n;
    1503                 :            : 
    1504                 :        286 :   while (TREE_CODE (access_fn) == POLYNOMIAL_CHREC)
    1505                 :            :     {
    1506                 :        143 :       aloop = get_chrec_loop (access_fn);
    1507                 :        143 :       step = CHREC_RIGHT (access_fn);
    1508                 :        143 :       access_fn = CHREC_LEFT (access_fn);
    1509                 :            : 
    1510                 :        286 :       if ((unsigned) loop_depth (aloop) <= min_depth)
    1511                 :          0 :         continue;
    1512                 :            : 
    1513                 :        143 :       if (tree_fits_shwi_p (step))
    1514                 :         95 :         astep = tree_to_shwi (step);
    1515                 :            :       else
    1516                 :         48 :         astep = param_l1_cache_line_size;
    1517                 :            : 
    1518                 :        143 :       strides[n - 1 - loop_depth (loop) + loop_depth (aloop)] += astep * stride;
    1519                 :            : 
    1520                 :            :     }
    1521                 :        143 : }
    1522                 :            : 
    1523                 :            : /* Returns the volume of memory references accessed between two consecutive
    1524                 :            :    self-reuses of the reference DR.  We consider the subscripts of DR in N
    1525                 :            :    loops, and LOOP_SIZES contains the volumes of accesses in each of the
    1526                 :            :    loops.  LOOP is the innermost loop of the current loop nest.  */
    1527                 :            : 
    1528                 :            : static unsigned
    1529                 :        133 : self_reuse_distance (data_reference_p dr, unsigned *loop_sizes, unsigned n,
    1530                 :            :                      class loop *loop)
    1531                 :            : {
    1532                 :        133 :   tree stride, access_fn;
    1533                 :        133 :   HOST_WIDE_INT *strides, astride;
    1534                 :        133 :   vec<tree> access_fns;
    1535                 :        133 :   tree ref = DR_REF (dr);
    1536                 :        133 :   unsigned i, ret = ~0u;
    1537                 :            : 
    1538                 :            :   /* In the following example:
    1539                 :            : 
    1540                 :            :      for (i = 0; i < N; i++)
    1541                 :            :        for (j = 0; j < N; j++)
    1542                 :            :          use (a[j][i]);
    1543                 :            :      the same cache line is accessed each N steps (except if the change from
    1544                 :            :      i to i + 1 crosses the boundary of the cache line).  Thus, for self-reuse,
    1545                 :            :      we cannot rely purely on the results of the data dependence analysis.
    1546                 :            : 
    1547                 :            :      Instead, we compute the stride of the reference in each loop, and consider
    1548                 :            :      the innermost loop in that the stride is less than cache size.  */
    1549                 :            : 
    1550                 :        133 :   strides = XCNEWVEC (HOST_WIDE_INT, n);
    1551                 :        133 :   access_fns = DR_ACCESS_FNS (dr);
    1552                 :            : 
    1553                 :        419 :   FOR_EACH_VEC_ELT (access_fns, i, access_fn)
    1554                 :            :     {
    1555                 :            :       /* Keep track of the reference corresponding to the subscript, so that we
    1556                 :            :          know its stride.  */
    1557                 :        145 :       while (handled_component_p (ref) && TREE_CODE (ref) != ARRAY_REF)
    1558                 :          2 :         ref = TREE_OPERAND (ref, 0);
    1559                 :            : 
    1560                 :        143 :       if (TREE_CODE (ref) == ARRAY_REF)
    1561                 :            :         {
    1562                 :         52 :           stride = TYPE_SIZE_UNIT (TREE_TYPE (ref));
    1563                 :         52 :           if (tree_fits_uhwi_p (stride))
    1564                 :         52 :             astride = tree_to_uhwi (stride);
    1565                 :            :           else
    1566                 :          0 :             astride = param_l1_cache_line_size;
    1567                 :            : 
    1568                 :         52 :           ref = TREE_OPERAND (ref, 0);
    1569                 :            :         }
    1570                 :            :       else
    1571                 :            :         astride = 1;
    1572                 :            : 
    1573                 :        143 :       add_subscript_strides (access_fn, astride, strides, n, loop);
    1574                 :            :     }
    1575                 :            : 
    1576                 :        279 :   for (i = n; i-- > 0; )
    1577                 :            :     {
    1578                 :        157 :       unsigned HOST_WIDE_INT s;
    1579                 :            : 
    1580                 :        157 :       s = strides[i] < 0 ?  -strides[i] : strides[i];
    1581                 :            : 
    1582                 :        157 :       if (s < (unsigned) param_l1_cache_line_size
    1583                 :        101 :           && (loop_sizes[i]
    1584                 :        101 :               > (unsigned) (L1_CACHE_SIZE_BYTES / NONTEMPORAL_FRACTION)))
    1585                 :            :         {
    1586                 :            :           ret = loop_sizes[i];
    1587                 :            :           break;
    1588                 :            :         }
    1589                 :            :     }
    1590                 :            : 
    1591                 :        133 :   free (strides);
    1592                 :        133 :   return ret;
    1593                 :            : }
    1594                 :            : 
    1595                 :            : /* Determines the distance till the first reuse of each reference in REFS
    1596                 :            :    in the loop nest of LOOP.  NO_OTHER_REFS is true if there are no other
    1597                 :            :    memory references in the loop.  Return false if the analysis fails.  */
    1598                 :            : 
    1599                 :            : static bool
    1600                 :         65 : determine_loop_nest_reuse (class loop *loop, struct mem_ref_group *refs,
    1601                 :            :                            bool no_other_refs)
    1602                 :            : {
    1603                 :         65 :   class loop *nest, *aloop;
    1604                 :         65 :   vec<data_reference_p> datarefs = vNULL;
    1605                 :         65 :   vec<ddr_p> dependences = vNULL;
    1606                 :         65 :   struct mem_ref_group *gr;
    1607                 :         65 :   struct mem_ref *ref, *refb;
    1608                 :         65 :   auto_vec<loop_p> vloops;
    1609                 :         65 :   unsigned *loop_data_size;
    1610                 :         65 :   unsigned i, j, n;
    1611                 :         65 :   unsigned volume, dist, adist;
    1612                 :         65 :   HOST_WIDE_INT vol;
    1613                 :         65 :   data_reference_p dr;
    1614                 :         65 :   ddr_p dep;
    1615                 :            : 
    1616                 :         65 :   if (loop->inner)
    1617                 :            :     return true;
    1618                 :            : 
    1619                 :            :   /* Find the outermost loop of the loop nest of loop (we require that
    1620                 :            :      there are no sibling loops inside the nest).  */
    1621                 :            :   nest = loop;
    1622                 :         71 :   while (1)
    1623                 :            :     {
    1624                 :         71 :       aloop = loop_outer (nest);
    1625                 :            : 
    1626                 :         71 :       if (aloop == current_loops->tree_root
    1627                 :         20 :           || aloop->inner->next)
    1628                 :            :         break;
    1629                 :            : 
    1630                 :            :       nest = aloop;
    1631                 :            :     }
    1632                 :            : 
    1633                 :            :   /* For each loop, determine the amount of data accessed in each iteration.
    1634                 :            :      We use this to estimate whether the reference is evicted from the
    1635                 :            :      cache before its reuse.  */
    1636                 :         63 :   find_loop_nest (nest, &vloops);
    1637                 :         63 :   n = vloops.length ();
    1638                 :         63 :   loop_data_size = XNEWVEC (unsigned, n);
    1639                 :         63 :   volume = volume_of_references (refs);
    1640                 :            :   i = n;
    1641                 :        134 :   while (i-- != 0)
    1642                 :            :     {
    1643                 :         71 :       loop_data_size[i] = volume;
    1644                 :            :       /* Bound the volume by the L2 cache size, since above this bound,
    1645                 :            :          all dependence distances are equivalent.  */
    1646                 :         71 :       if (volume > L2_CACHE_SIZE_BYTES)
    1647                 :          0 :         continue;
    1648                 :            : 
    1649                 :         71 :       aloop = vloops[i];
    1650                 :         71 :       vol = estimated_stmt_executions_int (aloop);
    1651                 :         71 :       if (vol == -1)
    1652                 :         32 :         vol = expected_loop_iterations (aloop);
    1653                 :         71 :       volume *= vol;
    1654                 :            :     }
    1655                 :            : 
    1656                 :            :   /* Prepare the references in the form suitable for data dependence
    1657                 :            :      analysis.  We ignore unanalyzable data references (the results
    1658                 :            :      are used just as a heuristics to estimate temporality of the
    1659                 :            :      references, hence we do not need to worry about correctness).  */
    1660                 :        186 :   for (gr = refs; gr; gr = gr->next)
    1661                 :        256 :     for (ref = gr->refs; ref; ref = ref->next)
    1662                 :            :       {
    1663                 :        133 :         dr = create_data_ref (loop_preheader_edge (nest),
    1664                 :            :                               loop_containing_stmt (ref->stmt),
    1665                 :        133 :                               ref->mem, ref->stmt, !ref->write_p, false);
    1666                 :            : 
    1667                 :        133 :         if (dr)
    1668                 :            :           {
    1669                 :        133 :             ref->reuse_distance = volume;
    1670                 :        133 :             dr->aux = ref;
    1671                 :        133 :             datarefs.safe_push (dr);
    1672                 :            :           }
    1673                 :            :         else
    1674                 :            :           no_other_refs = false;
    1675                 :            :       }
    1676                 :            : 
    1677                 :        259 :   FOR_EACH_VEC_ELT (datarefs, i, dr)
    1678                 :            :     {
    1679                 :        133 :       dist = self_reuse_distance (dr, loop_data_size, n, loop);
    1680                 :        133 :       ref = (struct mem_ref *) dr->aux;
    1681                 :        133 :       if (ref->reuse_distance > dist)
    1682                 :         11 :         ref->reuse_distance = dist;
    1683                 :            : 
    1684                 :        133 :       if (no_other_refs)
    1685                 :         84 :         ref->independent_p = true;
    1686                 :            :     }
    1687                 :            : 
    1688                 :         63 :   if (!compute_all_dependences (datarefs, &dependences, vloops, true))
    1689                 :            :     return false;
    1690                 :            : 
    1691                 :        317 :   FOR_EACH_VEC_ELT (dependences, i, dep)
    1692                 :            :     {
    1693                 :        254 :       if (DDR_ARE_DEPENDENT (dep) == chrec_known)
    1694                 :         45 :         continue;
    1695                 :            : 
    1696                 :        209 :       ref = (struct mem_ref *) DDR_A (dep)->aux;
    1697                 :        209 :       refb = (struct mem_ref *) DDR_B (dep)->aux;
    1698                 :            : 
    1699                 :        209 :       if (DDR_ARE_DEPENDENT (dep) == chrec_dont_know
    1700                 :        134 :           || DDR_COULD_BE_INDEPENDENT_P (dep)
    1701                 :        343 :           || DDR_NUM_DIST_VECTS (dep) == 0)
    1702                 :            :         {
    1703                 :            :           /* If the dependence cannot be analyzed, assume that there might be
    1704                 :            :              a reuse.  */
    1705                 :         75 :           dist = 0;
    1706                 :            : 
    1707                 :         75 :           ref->independent_p = false;
    1708                 :         75 :           refb->independent_p = false;
    1709                 :            :         }
    1710                 :            :       else
    1711                 :            :         {
    1712                 :            :           /* The distance vectors are normalized to be always lexicographically
    1713                 :            :              positive, hence we cannot tell just from them whether DDR_A comes
    1714                 :            :              before DDR_B or vice versa.  However, it is not important,
    1715                 :            :              anyway -- if DDR_A is close to DDR_B, then it is either reused in
    1716                 :            :              DDR_B (and it is not nontemporal), or it reuses the value of DDR_B
    1717                 :            :              in cache (and marking it as nontemporal would not affect
    1718                 :            :              anything).  */
    1719                 :            : 
    1720                 :            :           dist = volume;
    1721                 :        268 :           for (j = 0; j < DDR_NUM_DIST_VECTS (dep); j++)
    1722                 :            :             {
    1723                 :        134 :               adist = volume_of_dist_vector (DDR_DIST_VECT (dep, j),
    1724                 :            :                                              loop_data_size, n);
    1725                 :            : 
    1726                 :            :               /* If this is a dependence in the innermost loop (i.e., the
    1727                 :            :                  distances in all superloops are zero) and it is not
    1728                 :            :                  the trivial self-dependence with distance zero, record that
    1729                 :            :                  the references are not completely independent.  */
    1730                 :        134 :               if (lambda_vector_zerop (DDR_DIST_VECT (dep, j), n - 1)
    1731                 :        134 :                   && (ref != refb
    1732                 :        129 :                       || DDR_DIST_VECT (dep, j)[n-1] != 0))
    1733                 :            :                 {
    1734                 :          3 :                   ref->independent_p = false;
    1735                 :          3 :                   refb->independent_p = false;
    1736                 :            :                 }
    1737                 :            : 
    1738                 :            :               /* Ignore accesses closer than
    1739                 :            :                  L1_CACHE_SIZE_BYTES / NONTEMPORAL_FRACTION,
    1740                 :            :                  so that we use nontemporal prefetches e.g. if single memory
    1741                 :            :                  location is accessed several times in a single iteration of
    1742                 :            :                  the loop.  */
    1743                 :        134 :               if (adist < L1_CACHE_SIZE_BYTES / NONTEMPORAL_FRACTION)
    1744                 :        130 :                 continue;
    1745                 :            : 
    1746                 :          4 :               if (adist < dist)
    1747                 :            :                 dist = adist;
    1748                 :            :             }
    1749                 :            :         }
    1750                 :            : 
    1751                 :        209 :       if (ref->reuse_distance > dist)
    1752                 :         28 :         ref->reuse_distance = dist;
    1753                 :        209 :       if (refb->reuse_distance > dist)
    1754                 :         46 :         refb->reuse_distance = dist;
    1755                 :            :     }
    1756                 :            : 
    1757                 :         63 :   free_dependence_relations (dependences);
    1758                 :         63 :   free_data_refs (datarefs);
    1759                 :         63 :   free (loop_data_size);
    1760                 :            : 
    1761                 :         63 :   if (dump_file && (dump_flags & TDF_DETAILS))
    1762                 :            :     {
    1763                 :         15 :       fprintf (dump_file, "Reuse distances:\n");
    1764                 :         38 :       for (gr = refs; gr; gr = gr->next)
    1765                 :         49 :         for (ref = gr->refs; ref; ref = ref->next)
    1766                 :         26 :           fprintf (dump_file, " reference %u:%u distance %u\n",
    1767                 :         26 :                    ref->group->uid, ref->uid, ref->reuse_distance);
    1768                 :            :     }
    1769                 :            : 
    1770                 :            :   return true;
    1771                 :            : }
    1772                 :            : 
    1773                 :            : /* Determine whether or not the trip count to ahead ratio is too small based
    1774                 :            :    on prefitablility consideration.
    1775                 :            :    AHEAD: the iteration ahead distance,
    1776                 :            :    EST_NITER: the estimated trip count.  */
    1777                 :            : 
    1778                 :            : static bool
    1779                 :        131 : trip_count_to_ahead_ratio_too_small_p (unsigned ahead, HOST_WIDE_INT est_niter)
    1780                 :            : {
    1781                 :            :   /* Assume trip count to ahead ratio is big enough if the trip count could not
    1782                 :            :      be estimated at compile time.  */
    1783                 :        131 :   if (est_niter < 0)
    1784                 :            :     return false;
    1785                 :            : 
    1786                 :        106 :   if (est_niter < (HOST_WIDE_INT) (TRIP_COUNT_TO_AHEAD_RATIO * ahead))
    1787                 :            :     {
    1788                 :         27 :       if (dump_file && (dump_flags & TDF_DETAILS))
    1789                 :          1 :         fprintf (dump_file,
    1790                 :            :                  "Not prefetching -- loop estimated to roll only %d times\n",
    1791                 :            :                  (int) est_niter);
    1792                 :         27 :       return true;
    1793                 :            :     }
    1794                 :            : 
    1795                 :            :   return false;
    1796                 :            : }
    1797                 :            : 
    1798                 :            : /* Determine whether or not the number of memory references in the loop is
    1799                 :            :    reasonable based on the profitablity and compilation time considerations.
    1800                 :            :    NINSNS: estimated number of instructions in the loop,
    1801                 :            :    MEM_REF_COUNT: total number of memory references in the loop.  */
    1802                 :            : 
    1803                 :            : static bool
    1804                 :        104 : mem_ref_count_reasonable_p (unsigned ninsns, unsigned mem_ref_count)
    1805                 :            : {
    1806                 :        104 :   int insn_to_mem_ratio;
    1807                 :            : 
    1808                 :        104 :   if (mem_ref_count == 0)
    1809                 :            :     return false;
    1810                 :            : 
    1811                 :            :   /* Miss rate computation (is_miss_rate_acceptable) and dependence analysis
    1812                 :            :      (compute_all_dependences) have high costs based on quadratic complexity.
    1813                 :            :      To avoid huge compilation time, we give up prefetching if mem_ref_count
    1814                 :            :      is too large.  */
    1815                 :         85 :   if (mem_ref_count > PREFETCH_MAX_MEM_REFS_PER_LOOP)
    1816                 :            :     return false;
    1817                 :            : 
    1818                 :            :   /* Prefetching improves performance by overlapping cache missing
    1819                 :            :      memory accesses with CPU operations.  If the loop does not have
    1820                 :            :      enough CPU operations to overlap with memory operations, prefetching
    1821                 :            :      won't give a significant benefit.  One approximate way of checking
    1822                 :            :      this is to require the ratio of instructions to memory references to
    1823                 :            :      be above a certain limit.  This approximation works well in practice.
    1824                 :            :      TODO: Implement a more precise computation by estimating the time
    1825                 :            :      for each CPU or memory op in the loop. Time estimates for memory ops
    1826                 :            :      should account for cache misses.  */
    1827                 :         85 :   insn_to_mem_ratio = ninsns / mem_ref_count;
    1828                 :            : 
    1829                 :         85 :   if (insn_to_mem_ratio < param_prefetch_min_insn_to_mem_ratio)
    1830                 :            :     {
    1831                 :         18 :       if (dump_file && (dump_flags & TDF_DETAILS))
    1832                 :          0 :         fprintf (dump_file,
    1833                 :            :                  "Not prefetching -- instruction to memory reference ratio (%d) too small\n",
    1834                 :            :                  insn_to_mem_ratio);
    1835                 :         18 :       return false;
    1836                 :            :     }
    1837                 :            : 
    1838                 :            :   return true;
    1839                 :            : }
    1840                 :            : 
    1841                 :            : /* Determine whether or not the instruction to prefetch ratio in the loop is
    1842                 :            :    too small based on the profitablity consideration.
    1843                 :            :    NINSNS: estimated number of instructions in the loop,
    1844                 :            :    PREFETCH_COUNT: an estimate of the number of prefetches,
    1845                 :            :    UNROLL_FACTOR:  the factor to unroll the loop if prefetching.  */
    1846                 :            : 
    1847                 :            : static bool
    1848                 :         65 : insn_to_prefetch_ratio_too_small_p (unsigned ninsns, unsigned prefetch_count,
    1849                 :            :                                      unsigned unroll_factor)
    1850                 :            : {
    1851                 :         65 :   int insn_to_prefetch_ratio;
    1852                 :            : 
    1853                 :            :   /* Prefetching most likely causes performance degradation when the instruction
    1854                 :            :      to prefetch ratio is too small.  Too many prefetch instructions in a loop
    1855                 :            :      may reduce the I-cache performance.
    1856                 :            :      (unroll_factor * ninsns) is used to estimate the number of instructions in
    1857                 :            :      the unrolled loop.  This implementation is a bit simplistic -- the number
    1858                 :            :      of issued prefetch instructions is also affected by unrolling.  So,
    1859                 :            :      prefetch_mod and the unroll factor should be taken into account when
    1860                 :            :      determining prefetch_count.  Also, the number of insns of the unrolled
    1861                 :            :      loop will usually be significantly smaller than the number of insns of the
    1862                 :            :      original loop * unroll_factor (at least the induction variable increases
    1863                 :            :      and the exit branches will get eliminated), so it might be better to use
    1864                 :            :      tree_estimate_loop_size + estimated_unrolled_size.  */
    1865                 :         65 :   insn_to_prefetch_ratio = (unroll_factor * ninsns) / prefetch_count;
    1866                 :         65 :   if (insn_to_prefetch_ratio < param_min_insn_to_prefetch_ratio)
    1867                 :            :     {
    1868                 :          2 :       if (dump_file && (dump_flags & TDF_DETAILS))
    1869                 :          0 :         fprintf (dump_file,
    1870                 :            :                  "Not prefetching -- instruction to prefetch ratio (%d) too small\n",
    1871                 :            :                  insn_to_prefetch_ratio);
    1872                 :          2 :       return true;
    1873                 :            :     }
    1874                 :            : 
    1875                 :            :   return false;
    1876                 :            : }
    1877                 :            : 
    1878                 :            : 
    1879                 :            : /* Issue prefetch instructions for array references in LOOP.  Returns
    1880                 :            :    true if the LOOP was unrolled.  */
    1881                 :            : 
    1882                 :            : static bool
    1883                 :        133 : loop_prefetch_arrays (class loop *loop)
    1884                 :            : {
    1885                 :        133 :   struct mem_ref_group *refs;
    1886                 :        133 :   unsigned ahead, ninsns, time, unroll_factor;
    1887                 :        133 :   HOST_WIDE_INT est_niter;
    1888                 :        133 :   class tree_niter_desc desc;
    1889                 :        133 :   bool unrolled = false, no_other_refs;
    1890                 :        133 :   unsigned prefetch_count;
    1891                 :        133 :   unsigned mem_ref_count;
    1892                 :            : 
    1893                 :        133 :   if (optimize_loop_nest_for_size_p (loop))
    1894                 :            :     {
    1895                 :          1 :       if (dump_file && (dump_flags & TDF_DETAILS))
    1896                 :          0 :         fprintf (dump_file, "  ignored (cold area)\n");
    1897                 :          1 :       return false;
    1898                 :            :     }
    1899                 :            : 
    1900                 :            :   /* FIXME: the time should be weighted by the probabilities of the blocks in
    1901                 :            :      the loop body.  */
    1902                 :        132 :   time = tree_num_loop_insns (loop, &eni_time_weights);
    1903                 :        132 :   if (time == 0)
    1904                 :            :     return false;
    1905                 :            : 
    1906                 :        131 :   ahead = (param_prefetch_latency + time - 1) / time;
    1907                 :        131 :   est_niter = estimated_stmt_executions_int (loop);
    1908                 :        131 :   if (est_niter == -1)
    1909                 :         67 :     est_niter = likely_max_stmt_executions_int (loop);
    1910                 :            : 
    1911                 :            :   /* Prefetching is not likely to be profitable if the trip count to ahead
    1912                 :            :      ratio is too small.  */
    1913                 :        131 :   if (trip_count_to_ahead_ratio_too_small_p (ahead, est_niter))
    1914                 :            :     return false;
    1915                 :            : 
    1916                 :        104 :   ninsns = tree_num_loop_insns (loop, &eni_size_weights);
    1917                 :            : 
    1918                 :            :   /* Step 1: gather the memory references.  */
    1919                 :        104 :   refs = gather_memory_references (loop, &no_other_refs, &mem_ref_count);
    1920                 :            : 
    1921                 :            :   /* Give up prefetching if the number of memory references in the
    1922                 :            :      loop is not reasonable based on profitablity and compilation time
    1923                 :            :      considerations.  */
    1924                 :        104 :   if (!mem_ref_count_reasonable_p (ninsns, mem_ref_count))
    1925                 :         37 :     goto fail;
    1926                 :            : 
    1927                 :            :   /* Step 2: estimate the reuse effects.  */
    1928                 :         67 :   prune_by_reuse (refs);
    1929                 :            : 
    1930                 :         67 :   if (nothing_to_prefetch_p (refs))
    1931                 :          2 :     goto fail;
    1932                 :            : 
    1933                 :         65 :   if (!determine_loop_nest_reuse (loop, refs, no_other_refs))
    1934                 :          0 :     goto fail;
    1935                 :            : 
    1936                 :            :   /* Step 3: determine unroll factor.  */
    1937                 :         65 :   unroll_factor = determine_unroll_factor (loop, refs, ninsns, &desc,
    1938                 :            :                                            est_niter);
    1939                 :            : 
    1940                 :            :   /* Estimate prefetch count for the unrolled loop.  */
    1941                 :         65 :   prefetch_count = estimate_prefetch_count (refs, unroll_factor);
    1942                 :         65 :   if (prefetch_count == 0)
    1943                 :          0 :     goto fail;
    1944                 :            : 
    1945                 :         65 :   if (dump_file && (dump_flags & TDF_DETAILS))
    1946                 :         15 :     fprintf (dump_file, "Ahead %d, unroll factor %d, trip count "
    1947                 :            :              HOST_WIDE_INT_PRINT_DEC "\n"
    1948                 :            :              "insn count %d, mem ref count %d, prefetch count %d\n",
    1949                 :            :              ahead, unroll_factor, est_niter,
    1950                 :            :              ninsns, mem_ref_count, prefetch_count);
    1951                 :            : 
    1952                 :            :   /* Prefetching is not likely to be profitable if the instruction to prefetch
    1953                 :            :      ratio is too small.  */
    1954                 :         65 :   if (insn_to_prefetch_ratio_too_small_p (ninsns, prefetch_count,
    1955                 :            :                                           unroll_factor))
    1956                 :          2 :     goto fail;
    1957                 :            : 
    1958                 :         63 :   mark_nontemporal_stores (loop, refs);
    1959                 :            : 
    1960                 :            :   /* Step 4: what to prefetch?  */
    1961                 :         63 :   if (!schedule_prefetches (refs, unroll_factor, ahead))
    1962                 :          2 :     goto fail;
    1963                 :            : 
    1964                 :            :   /* Step 5: unroll the loop.  TODO -- peeling of first and last few
    1965                 :            :      iterations so that we do not issue superfluous prefetches.  */
    1966                 :         61 :   if (unroll_factor != 1)
    1967                 :            :     {
    1968                 :         35 :       tree_unroll_loop (loop, unroll_factor,
    1969                 :            :                         single_dom_exit (loop), &desc);
    1970                 :         35 :       unrolled = true;
    1971                 :            :     }
    1972                 :            : 
    1973                 :            :   /* Step 6: issue the prefetches.  */
    1974                 :         61 :   issue_prefetches (refs, unroll_factor, ahead);
    1975                 :            : 
    1976                 :        104 : fail:
    1977                 :        104 :   release_mem_refs (refs);
    1978                 :        104 :   return unrolled;
    1979                 :            : }
    1980                 :            : 
    1981                 :            : /* Issue prefetch instructions for array references in loops.  */
    1982                 :            : 
    1983                 :            : unsigned int
    1984                 :         72 : tree_ssa_prefetch_arrays (void)
    1985                 :            : {
    1986                 :         72 :   class loop *loop;
    1987                 :         72 :   bool unrolled = false;
    1988                 :         72 :   int todo_flags = 0;
    1989                 :            : 
    1990                 :         72 :   if (!targetm.have_prefetch ()
    1991                 :            :       /* It is possible to ask compiler for say -mtune=i486 -march=pentium4.
    1992                 :            :          -mtune=i486 causes us having PREFETCH_BLOCK 0, since this is part
    1993                 :            :          of processor costs and i486 does not have prefetch, but
    1994                 :            :          -march=pentium4 causes targetm.have_prefetch to be true.  Ugh.  */
    1995                 :         72 :       || PREFETCH_BLOCK == 0)
    1996                 :            :     return 0;
    1997                 :            : 
    1998                 :         72 :   if (dump_file && (dump_flags & TDF_DETAILS))
    1999                 :            :     {
    2000                 :         10 :       fprintf (dump_file, "Prefetching parameters:\n");
    2001                 :         10 :       fprintf (dump_file, "    simultaneous prefetches: %d\n",
    2002                 :            :                param_simultaneous_prefetches);
    2003                 :         10 :       fprintf (dump_file, "    prefetch latency: %d\n", param_prefetch_latency);
    2004                 :         10 :       fprintf (dump_file, "    prefetch block size: %d\n", PREFETCH_BLOCK);
    2005                 :         10 :       fprintf (dump_file, "    L1 cache size: %d lines, %d kB\n",
    2006                 :         10 :                L1_CACHE_SIZE_BYTES / param_l1_cache_line_size,
    2007                 :            :                param_l1_cache_size);
    2008                 :         10 :       fprintf (dump_file, "    L1 cache line size: %d\n",
    2009                 :            :                param_l1_cache_line_size);
    2010                 :         10 :       fprintf (dump_file, "    L2 cache size: %d kB\n", param_l2_cache_size);
    2011                 :         10 :       fprintf (dump_file, "    min insn-to-prefetch ratio: %d \n",
    2012                 :            :                param_min_insn_to_prefetch_ratio);
    2013                 :         10 :       fprintf (dump_file, "    min insn-to-mem ratio: %d \n",
    2014                 :            :                param_prefetch_min_insn_to_mem_ratio);
    2015                 :         10 :       fprintf (dump_file, "\n");
    2016                 :            :     }
    2017                 :            : 
    2018                 :         72 :   initialize_original_copy_tables ();
    2019                 :            : 
    2020                 :         72 :   if (!builtin_decl_explicit_p (BUILT_IN_PREFETCH))
    2021                 :            :     {
    2022                 :          4 :       tree type = build_function_type_list (void_type_node,
    2023                 :            :                                             const_ptr_type_node, NULL_TREE);
    2024                 :          4 :       tree decl = add_builtin_function ("__builtin_prefetch", type,
    2025                 :            :                                         BUILT_IN_PREFETCH, BUILT_IN_NORMAL,
    2026                 :            :                                         NULL, NULL_TREE);
    2027                 :          4 :       DECL_IS_NOVOPS (decl) = true;
    2028                 :          4 :       set_builtin_decl (BUILT_IN_PREFETCH, decl, false);
    2029                 :            :     }
    2030                 :            : 
    2031                 :        205 :   FOR_EACH_LOOP (loop, LI_FROM_INNERMOST)
    2032                 :            :     {
    2033                 :        133 :       if (dump_file && (dump_flags & TDF_DETAILS))
    2034                 :         24 :         fprintf (dump_file, "Processing loop %d:\n", loop->num);
    2035                 :            : 
    2036                 :        133 :       unrolled |= loop_prefetch_arrays (loop);
    2037                 :            : 
    2038                 :        133 :       if (dump_file && (dump_flags & TDF_DETAILS))
    2039                 :         24 :         fprintf (dump_file, "\n\n");
    2040                 :            :     }
    2041                 :            : 
    2042                 :         72 :   if (unrolled)
    2043                 :            :     {
    2044                 :         19 :       scev_reset ();
    2045                 :         19 :       todo_flags |= TODO_cleanup_cfg;
    2046                 :            :     }
    2047                 :            : 
    2048                 :         72 :   free_original_copy_tables ();
    2049                 :         72 :   return todo_flags;
    2050                 :            : }
    2051                 :            : 
    2052                 :            : /* Prefetching.  */
    2053                 :            : 
    2054                 :            : namespace {
    2055                 :            : 
    2056                 :            : const pass_data pass_data_loop_prefetch =
    2057                 :            : {
    2058                 :            :   GIMPLE_PASS, /* type */
    2059                 :            :   "aprefetch", /* name */
    2060                 :            :   OPTGROUP_LOOP, /* optinfo_flags */
    2061                 :            :   TV_TREE_PREFETCH, /* tv_id */
    2062                 :            :   ( PROP_cfg | PROP_ssa ), /* properties_required */
    2063                 :            :   0, /* properties_provided */
    2064                 :            :   0, /* properties_destroyed */
    2065                 :            :   0, /* todo_flags_start */
    2066                 :            :   0, /* todo_flags_finish */
    2067                 :            : };
    2068                 :            : 
    2069                 :            : class pass_loop_prefetch : public gimple_opt_pass
    2070                 :            : {
    2071                 :            : public:
    2072                 :     200540 :   pass_loop_prefetch (gcc::context *ctxt)
    2073                 :     401080 :     : gimple_opt_pass (pass_data_loop_prefetch, ctxt)
    2074                 :            :   {}
    2075                 :            : 
    2076                 :            :   /* opt_pass methods: */
    2077                 :     157439 :   virtual bool gate (function *) { return flag_prefetch_loop_arrays > 0; }
    2078                 :            :   virtual unsigned int execute (function *);
    2079                 :            : 
    2080                 :            : }; // class pass_loop_prefetch
    2081                 :            : 
    2082                 :            : unsigned int
    2083                 :         74 : pass_loop_prefetch::execute (function *fun)
    2084                 :            : {
    2085                 :        148 :   if (number_of_loops (fun) <= 1)
    2086                 :            :     return 0;
    2087                 :            : 
    2088                 :         74 :   if ((PREFETCH_BLOCK & (PREFETCH_BLOCK - 1)) != 0)
    2089                 :            :     {
    2090                 :          2 :       static bool warned = false;
    2091                 :            : 
    2092                 :          2 :       if (!warned)
    2093                 :            :         {
    2094                 :          1 :           warning (OPT_Wdisabled_optimization,
    2095                 :            :                    "%<l1-cache-size%> parameter is not a power of two %d",
    2096                 :            :                    PREFETCH_BLOCK);
    2097                 :          1 :           warned = true;
    2098                 :            :         }
    2099                 :          2 :       return 0;
    2100                 :            :     }
    2101                 :            : 
    2102                 :         72 :   return tree_ssa_prefetch_arrays ();
    2103                 :            : }
    2104                 :            : 
    2105                 :            : } // anon namespace
    2106                 :            : 
    2107                 :            : gimple_opt_pass *
    2108                 :     200540 : make_pass_loop_prefetch (gcc::context *ctxt)
    2109                 :            : {
    2110                 :     200540 :   return new pass_loop_prefetch (ctxt);
    2111                 :            : }
    2112                 :            : 
    2113                 :            : 

Generated by: LCOV version 1.0

LCOV profile is generated on x86_64 machine using following configure options: configure --disable-bootstrap --enable-coverage=opt --enable-languages=c,c++,fortran,go,jit,lto --enable-host-shared. GCC test suite is run with the built compiler.