LCOV - code coverage report
Current view: top level - gcc - tree-switch-conversion.h (source / functions) Hit Total Coverage
Test: gcc.info Lines: 73 81 90.1 %
Date: 2020-03-28 11:57:23 Functions: 17 21 81.0 %
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           Branch data     Line data    Source code
       1                 :            : /* Tree switch conversion for GNU compiler.
       2                 :            :    Copyright (C) 2017-2020 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 under
       7                 :            : the terms of the GNU General Public License as published by the Free
       8                 :            : Software Foundation; either version 3, or (at your option) any later
       9                 :            : version.
      10                 :            : 
      11                 :            : GCC is distributed in the hope that it will be useful, but WITHOUT ANY
      12                 :            : 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                 :            : #ifndef TREE_SWITCH_CONVERSION_H
      21                 :            : #define TREE_SWITCH_CONVERSION_H
      22                 :            : 
      23                 :            : namespace tree_switch_conversion {
      24                 :            : 
      25                 :            : /* Type of cluster.  */
      26                 :            : 
      27                 :            : enum cluster_type
      28                 :            : {
      29                 :            :   SIMPLE_CASE,
      30                 :            :   JUMP_TABLE,
      31                 :            :   BIT_TEST
      32                 :            : };
      33                 :            : 
      34                 :            : #define PRINT_CASE(f,c) print_generic_expr (f, c)
      35                 :            : 
      36                 :            : /* Abstract base class for representing a cluster of cases.
      37                 :            : 
      38                 :            :    Here is the inheritance hierarachy, and the enum_cluster_type
      39                 :            :    values for the concrete subclasses:
      40                 :            : 
      41                 :            :    cluster
      42                 :            :    |-simple_cluster (SIMPLE_CASE)
      43                 :            :    `-group_cluster
      44                 :            :      |-jump_table_cluster (JUMP_TABLE)
      45                 :            :      `-bit_test_cluster   (BIT_TEST).  */
      46                 :            : 
      47                 :            : class cluster
      48                 :            : {
      49                 :            : public:
      50                 :            :   /* Constructor.  */
      51                 :            :   cluster (tree case_label_expr, basic_block case_bb, profile_probability prob,
      52                 :            :            profile_probability subtree_prob);
      53                 :            : 
      54                 :            :   /* Destructor.  */
      55                 :     144246 :   virtual ~cluster ()
      56                 :            :   {}
      57                 :            : 
      58                 :            :   /* Return type.  */
      59                 :            :   virtual cluster_type get_type () = 0;
      60                 :            : 
      61                 :            :   /* Get low value covered by a cluster.  */
      62                 :            :   virtual tree get_low () = 0;
      63                 :            : 
      64                 :            :   /* Get high value covered by a cluster.  */
      65                 :            :   virtual tree get_high () = 0;
      66                 :            : 
      67                 :            :   /* Debug content of a cluster.  */
      68                 :            :   virtual void debug () = 0;
      69                 :            : 
      70                 :            :   /* Dump content of a cluster.  */
      71                 :            :   virtual void dump (FILE *f, bool details = false) = 0;
      72                 :            : 
      73                 :            :   /* Emit GIMPLE code to handle the cluster.  */
      74                 :            :   virtual void emit (tree, tree, tree, basic_block) = 0;
      75                 :            : 
      76                 :            :   /* Return true if a cluster handles only a single case value and the
      77                 :            :      value is not a range.  */
      78                 :        433 :   virtual bool is_single_value_p ()
      79                 :            :   {
      80                 :        433 :     return false;
      81                 :            :   }
      82                 :            : 
      83                 :            :   /* Return range of a cluster.  If value would overflow in type of LOW,
      84                 :            :      then return 0.  */
      85                 :     261677 :   static unsigned HOST_WIDE_INT get_range (tree low, tree high)
      86                 :            :   {
      87                 :     261677 :     tree r = fold_build2 (MINUS_EXPR, TREE_TYPE (low), high, low);
      88                 :     261677 :     if (!tree_fits_uhwi_p (r))
      89                 :            :       return 0;
      90                 :            : 
      91                 :     261581 :     return tree_to_uhwi (r) + 1;
      92                 :            :   }
      93                 :            : 
      94                 :            :   /* Case label.  */
      95                 :            :   tree m_case_label_expr;
      96                 :            : 
      97                 :            :   /* Basic block of the case.  */
      98                 :            :   basic_block m_case_bb;
      99                 :            : 
     100                 :            :   /* Probability of taking this cluster.  */
     101                 :            :   profile_probability m_prob;
     102                 :            : 
     103                 :            :   /* Probability of reaching subtree rooted at this node.  */
     104                 :            :   profile_probability m_subtree_prob;
     105                 :            : 
     106                 :            : protected:
     107                 :            :   /* Default constructor.  */
     108                 :      10415 :   cluster () {}
     109                 :            : };
     110                 :            : 
     111                 :     133831 : cluster::cluster (tree case_label_expr, basic_block case_bb,
     112                 :     133831 :                   profile_probability prob, profile_probability subtree_prob):
     113                 :            :   m_case_label_expr (case_label_expr), m_case_bb (case_bb), m_prob (prob),
     114                 :     133831 :   m_subtree_prob (subtree_prob)
     115                 :            : {
     116                 :     133831 : }
     117                 :            : 
     118                 :            : /* Subclass of cluster representing a simple contiguous range
     119                 :            :    from [low..high].  */
     120                 :            : 
     121                 :            : class simple_cluster: public cluster
     122                 :            : {
     123                 :            : public:
     124                 :            :   /* Constructor.  */
     125                 :            :   simple_cluster (tree low, tree high, tree case_label_expr,
     126                 :            :                   basic_block case_bb, profile_probability prob);
     127                 :            : 
     128                 :            :   /* Destructor.  */
     129                 :     133831 :   ~simple_cluster ()
     130                 :     133831 :   {}
     131                 :            : 
     132                 :            :   cluster_type
     133                 :     138998 :   get_type ()
     134                 :            :   {
     135                 :     138998 :     return SIMPLE_CASE;
     136                 :            :   }
     137                 :            : 
     138                 :            :   tree
     139                 :     418639 :   get_low ()
     140                 :            :   {
     141                 :     418639 :     return m_low;
     142                 :            :   }
     143                 :            : 
     144                 :            :   tree
     145                 :     380811 :   get_high ()
     146                 :            :   {
     147                 :     380811 :     return m_high;
     148                 :            :   }
     149                 :            : 
     150                 :            :   void
     151                 :          0 :   debug ()
     152                 :            :   {
     153                 :          0 :     dump (stderr);
     154                 :          0 :   }
     155                 :            : 
     156                 :            :   void
     157                 :         41 :   dump (FILE *f, bool details ATTRIBUTE_UNUSED = false)
     158                 :            :   {
     159                 :         41 :     PRINT_CASE (f, get_low ());
     160                 :         41 :     if (get_low () != get_high ())
     161                 :            :       {
     162                 :          2 :         fprintf (f, "-");
     163                 :          2 :         PRINT_CASE (f, get_high ());
     164                 :            :       }
     165                 :         41 :     fprintf (f, " ");
     166                 :         41 :   }
     167                 :            : 
     168                 :          0 :   void emit (tree, tree, tree, basic_block)
     169                 :            :   {
     170                 :          0 :     gcc_unreachable ();
     171                 :            :   }
     172                 :            : 
     173                 :      45734 :   bool is_single_value_p ()
     174                 :            :   {
     175                 :      45734 :     return tree_int_cst_equal (get_low (), get_high ());
     176                 :            :   }
     177                 :            : 
     178                 :            :   /* Low value of the case.  */
     179                 :            :   tree m_low;
     180                 :            : 
     181                 :            :   /* High value of the case.  */
     182                 :            :   tree m_high;
     183                 :            : 
     184                 :            :   /* True if case is a range.  */
     185                 :            :   bool m_range_p;
     186                 :            : };
     187                 :            : 
     188                 :     133831 : simple_cluster::simple_cluster (tree low, tree high, tree case_label_expr,
     189                 :     133831 :                                 basic_block case_bb, profile_probability prob):
     190                 :            :   cluster (case_label_expr, case_bb, prob, prob),
     191                 :     133831 :   m_low (low), m_high (high)
     192                 :            : {
     193                 :     133831 :   m_range_p = m_high != NULL;
     194                 :     133831 :   if (m_high == NULL)
     195                 :     117046 :     m_high = m_low;
     196                 :     133831 : }
     197                 :            : 
     198                 :            : /* Abstract subclass of jump table and bit test cluster,
     199                 :            :    handling a collection of simple_cluster instances.  */
     200                 :            : 
     201                 :            : class group_cluster: public cluster
     202                 :            : {
     203                 :            : public:
     204                 :            :   /* Constructor.  */
     205                 :            :   group_cluster (vec<cluster *> &clusters, unsigned start, unsigned end);
     206                 :            : 
     207                 :            :   /* Destructor.  */
     208                 :            :   ~group_cluster ();
     209                 :            : 
     210                 :            :   tree
     211                 :      11200 :   get_low ()
     212                 :            :   {
     213                 :      11200 :     return m_cases[0]->get_low ();
     214                 :            :   }
     215                 :            : 
     216                 :            :   tree
     217                 :      11200 :   get_high ()
     218                 :            :   {
     219                 :      22400 :     return m_cases[m_cases.length () - 1]->get_high ();
     220                 :            :   }
     221                 :            : 
     222                 :            :   void
     223                 :          0 :   debug ()
     224                 :            :   {
     225                 :          0 :     dump (stderr);
     226                 :          0 :   }
     227                 :            : 
     228                 :            :   void dump (FILE *f, bool details = false);
     229                 :            : 
     230                 :            :   /* List of simple clusters handled by the group.  */
     231                 :            :   vec<simple_cluster *> m_cases;
     232                 :            : };
     233                 :            : 
     234                 :            : /* Concrete subclass of group_cluster representing a collection
     235                 :            :    of cases to be implemented as a jump table.
     236                 :            :    The "emit" vfunc gernerates a nested switch statement which
     237                 :            :    is later lowered to a jump table.  */
     238                 :            : 
     239                 :            : class jump_table_cluster: public group_cluster
     240                 :            : {
     241                 :            : public:
     242                 :            :   /* Constructor.  */
     243                 :       9869 :   jump_table_cluster (vec<cluster *> &clusters, unsigned start, unsigned end)
     244                 :       9869 :   : group_cluster (clusters, start, end)
     245                 :            :   {}
     246                 :            : 
     247                 :            :   cluster_type
     248                 :      29705 :   get_type ()
     249                 :            :   {
     250                 :      29705 :     return JUMP_TABLE;
     251                 :            :   }
     252                 :            : 
     253                 :            :   void emit (tree index_expr, tree index_type,
     254                 :            :              tree default_label_expr, basic_block default_bb);
     255                 :            : 
     256                 :            :   /* Find jump tables of given CLUSTERS, where all members of the vector
     257                 :            :      are of type simple_cluster.  New clusters are returned.  */
     258                 :            :   static vec<cluster *> find_jump_tables (vec<cluster *> &clusters);
     259                 :            : 
     260                 :            :   /* Return true when cluster starting at START and ending at END (inclusive)
     261                 :            :      can build a jump-table.  */
     262                 :            :   static bool can_be_handled (const vec<cluster *> &clusters, unsigned start,
     263                 :            :                               unsigned end);
     264                 :            : 
     265                 :            :   /* Return true if cluster starting at START and ending at END (inclusive)
     266                 :            :      is profitable transformation.  */
     267                 :            :   static bool is_beneficial (const vec<cluster *> &clusters, unsigned start,
     268                 :            :                              unsigned end);
     269                 :            : 
     270                 :            :   /* Return the smallest number of different values for which it is best
     271                 :            :      to use a jump-table instead of a tree of conditional branches.  */
     272                 :            :   static inline unsigned int case_values_threshold (void);
     273                 :            : 
     274                 :            :   /* Return whether jump table expansion is allowed.  */
     275                 :            :   static bool is_enabled (void);
     276                 :            : };
     277                 :            : 
     278                 :            : /* A GIMPLE switch statement can be expanded to a short sequence of bit-wise
     279                 :            : comparisons.  "switch(x)" is converted into "if ((1 << (x-MINVAL)) & CST)"
     280                 :            : where CST and MINVAL are integer constants.  This is better than a series
     281                 :            : of compare-and-banch insns in some cases,  e.g. we can implement:
     282                 :            : 
     283                 :            :         if ((x==4) || (x==6) || (x==9) || (x==11))
     284                 :            : 
     285                 :            : as a single bit test:
     286                 :            : 
     287                 :            :         if ((1<<x) & ((1<<4)|(1<<6)|(1<<9)|(1<<11)))
     288                 :            : 
     289                 :            : This transformation is only applied if the number of case targets is small,
     290                 :            : if CST constains at least 3 bits, and "1 << x" is cheap.  The bit tests are
     291                 :            : performed in "word_mode".
     292                 :            : 
     293                 :            : The following example shows the code the transformation generates:
     294                 :            : 
     295                 :            :         int bar(int x)
     296                 :            :         {
     297                 :            :                 switch (x)
     298                 :            :                 {
     299                 :            :                 case '0':  case '1':  case '2':  case '3':  case '4':
     300                 :            :                 case '5':  case '6':  case '7':  case '8':  case '9':
     301                 :            :                 case 'A':  case 'B':  case 'C':  case 'D':  case 'E':
     302                 :            :                 case 'F':
     303                 :            :                         return 1;
     304                 :            :                 }
     305                 :            :                 return 0;
     306                 :            :         }
     307                 :            : 
     308                 :            : ==>
     309                 :            : 
     310                 :            :         bar (int x)
     311                 :            :         {
     312                 :            :                 tmp1 = x - 48;
     313                 :            :                 if (tmp1 > (70 - 48)) goto L2;
     314                 :            :                 tmp2 = 1 << tmp1;
     315                 :            :                 tmp3 = 0b11111100000001111111111;
     316                 :            :                 if ((tmp2 & tmp3) != 0) goto L1 ; else goto L2;
     317                 :            :         L1:
     318                 :            :                 return 1;
     319                 :            :         L2:
     320                 :            :                 return 0;
     321                 :            :         }
     322                 :            : 
     323                 :            : TODO: There are still some improvements to this transformation that could
     324                 :            : be implemented:
     325                 :            : 
     326                 :            : * A narrower mode than word_mode could be used if that is cheaper, e.g.
     327                 :            :   for x86_64 where a narrower-mode shift may result in smaller code.
     328                 :            : 
     329                 :            : * The compounded constant could be shifted rather than the one.  The
     330                 :            :   test would be either on the sign bit or on the least significant bit,
     331                 :            :   depending on the direction of the shift.  On some machines, the test
     332                 :            :   for the branch would be free if the bit to test is already set by the
     333                 :            :   shift operation.
     334                 :            : 
     335                 :            : This transformation was contributed by Roger Sayle, see this e-mail:
     336                 :            :    http://gcc.gnu.org/ml/gcc-patches/2003-01/msg01950.html
     337                 :            : */
     338                 :            : 
     339                 :            : class bit_test_cluster: public group_cluster
     340                 :            : {
     341                 :            : public:
     342                 :            :   /* Constructor.  */
     343                 :        546 :   bit_test_cluster (vec<cluster *> &clusters, unsigned start, unsigned end,
     344                 :            :                     bool handles_entire_switch)
     345                 :        546 :   :group_cluster (clusters, start, end),
     346                 :        546 :   m_handles_entire_switch (handles_entire_switch)
     347                 :            :   {}
     348                 :            : 
     349                 :            :   cluster_type
     350                 :       1117 :   get_type ()
     351                 :            :   {
     352                 :       1117 :     return BIT_TEST;
     353                 :            :   }
     354                 :            : 
     355                 :            : /*  Expand a switch statement by a short sequence of bit-wise
     356                 :            :     comparisons.  "switch(x)" is effectively converted into
     357                 :            :     "if ((1 << (x-MINVAL)) & CST)" where CST and MINVAL are
     358                 :            :     integer constants.
     359                 :            : 
     360                 :            :     INDEX_EXPR is the value being switched on.
     361                 :            : 
     362                 :            :     MINVAL is the lowest case value of in the case nodes,
     363                 :            :     and RANGE is highest value minus MINVAL.  MINVAL and RANGE
     364                 :            :     are not guaranteed to be of the same type as INDEX_EXPR
     365                 :            :     (the gimplifier doesn't change the type of case label values,
     366                 :            :     and MINVAL and RANGE are derived from those values).
     367                 :            :     MAXVAL is MINVAL + RANGE.
     368                 :            : 
     369                 :            :     There *MUST* be max_case_bit_tests or less unique case
     370                 :            :     node targets.  */
     371                 :            :   void emit (tree index_expr, tree index_type,
     372                 :            :              tree default_label_expr, basic_block default_bb);
     373                 :            : 
     374                 :            :   /* Find bit tests of given CLUSTERS, where all members of the vector
     375                 :            :      are of type simple_cluster.  New clusters are returned.  */
     376                 :            :   static vec<cluster *> find_bit_tests (vec<cluster *> &clusters);
     377                 :            : 
     378                 :            :   /* Return true when RANGE of case values with UNIQ labels
     379                 :            :      can build a bit test.  */
     380                 :            :   static bool can_be_handled (unsigned HOST_WIDE_INT range, unsigned uniq);
     381                 :            : 
     382                 :            :   /* Return true when cluster starting at START and ending at END (inclusive)
     383                 :            :      can build a bit test.  */
     384                 :            :   static bool can_be_handled (const vec<cluster *> &clusters, unsigned start,
     385                 :            :                               unsigned end);
     386                 :            : 
     387                 :            :   /* Return true when COUNT of cases of UNIQ labels is beneficial for bit test
     388                 :            :      transformation.  */
     389                 :            :   static bool is_beneficial (unsigned count, unsigned uniq);
     390                 :            : 
     391                 :            :   /* Return true if cluster starting at START and ending at END (inclusive)
     392                 :            :      is profitable transformation.  */
     393                 :            :   static bool is_beneficial (const vec<cluster *> &clusters, unsigned start,
     394                 :            :                              unsigned end);
     395                 :            : 
     396                 :            : /* Split the basic block at the statement pointed to by GSIP, and insert
     397                 :            :    a branch to the target basic block of E_TRUE conditional on tree
     398                 :            :    expression COND.
     399                 :            : 
     400                 :            :    It is assumed that there is already an edge from the to-be-split
     401                 :            :    basic block to E_TRUE->dest block.  This edge is removed, and the
     402                 :            :    profile information on the edge is re-used for the new conditional
     403                 :            :    jump.
     404                 :            : 
     405                 :            :    The CFG is updated.  The dominator tree will not be valid after
     406                 :            :    this transformation, but the immediate dominators are updated if
     407                 :            :    UPDATE_DOMINATORS is true.
     408                 :            : 
     409                 :            :    Returns the newly created basic block.  */
     410                 :            :   static basic_block hoist_edge_and_branch_if_true (gimple_stmt_iterator *gsip,
     411                 :            :                                                     tree cond,
     412                 :            :                                                     basic_block case_bb,
     413                 :            :                                                     profile_probability prob);
     414                 :            : 
     415                 :            :   /* True when the jump table handles an entire switch statement.  */
     416                 :            :   bool m_handles_entire_switch;
     417                 :            : 
     418                 :            :   /* Maximum number of different basic blocks that can be handled by
     419                 :            :      a bit test.  */
     420                 :            :   static const int m_max_case_bit_tests = 3;
     421                 :            : };
     422                 :            : 
     423                 :            : /* Helper struct to find minimal clusters.  */
     424                 :            : 
     425                 :            : class min_cluster_item
     426                 :            : {
     427                 :            : public:
     428                 :            :   /* Constructor.  */
     429                 :     408611 :   min_cluster_item (unsigned count, unsigned start, unsigned non_jt_cases):
     430                 :            :     m_count (count), m_start (start), m_non_jt_cases (non_jt_cases)
     431                 :            :   {}
     432                 :            : 
     433                 :            :   /* Count of clusters.  */
     434                 :            :   unsigned m_count;
     435                 :            : 
     436                 :            :   /* Index where is cluster boundary.  */
     437                 :            :   unsigned m_start;
     438                 :            : 
     439                 :            :   /* Total number of cases that will not be in a jump table.  */
     440                 :            :   unsigned m_non_jt_cases;
     441                 :            : };
     442                 :            : 
     443                 :            : /* Helper struct to represent switch decision tree.  */
     444                 :            : 
     445                 :            : class case_tree_node
     446                 :            : {
     447                 :            : public:
     448                 :            :   /* Empty Constructor.  */
     449                 :            :   case_tree_node ();
     450                 :            : 
     451                 :            :   /* Return true when it has a child.  */
     452                 :      25830 :   bool has_child ()
     453                 :            :   {
     454                 :      25830 :     return m_left != NULL || m_right != NULL;
     455                 :            :   }
     456                 :            : 
     457                 :            :   /* Left son in binary tree.  */
     458                 :            :   case_tree_node *m_left;
     459                 :            : 
     460                 :            :   /* Right son in binary tree; also node chain.  */
     461                 :            :   case_tree_node *m_right;
     462                 :            : 
     463                 :            :   /* Parent of node in binary tree.  */
     464                 :            :   case_tree_node *m_parent;
     465                 :            : 
     466                 :            :   /* Cluster represented by this tree node.  */
     467                 :            :   cluster *m_c;
     468                 :            : };
     469                 :            : 
     470                 :            : inline
     471                 :      55361 : case_tree_node::case_tree_node ():
     472                 :      55361 :   m_left (NULL), m_right (NULL), m_parent (NULL), m_c (NULL)
     473                 :            : {
     474                 :            : }
     475                 :            : 
     476                 :            : unsigned int
     477                 :    2343460 : jump_table_cluster::case_values_threshold (void)
     478                 :            : {
     479                 :    2343460 :   unsigned int threshold = param_case_values_threshold;
     480                 :            : 
     481                 :    2343460 :   if (threshold == 0)
     482                 :    2343230 :     threshold = targetm.case_values_threshold ();
     483                 :            : 
     484                 :    2343460 :   return threshold;
     485                 :            : }
     486                 :            : 
     487                 :            : /* Return whether jump table expansion is allowed.  */
     488                 :      28465 : bool jump_table_cluster::is_enabled (void)
     489                 :            : {
     490                 :            :   /* If neither casesi or tablejump is available, or flag_jump_tables
     491                 :            :      over-ruled us, we really have no choice.  */
     492                 :      28465 :   if (!targetm.have_casesi () && !targetm.have_tablejump ())
     493                 :            :     return false;
     494                 :      28465 :   if (!flag_jump_tables)
     495                 :          2 :     return false;
     496                 :            : #ifndef ASM_OUTPUT_ADDR_DIFF_ELT
     497                 :            :   if (flag_pic)
     498                 :            :     return false;
     499                 :            : #endif
     500                 :            : 
     501                 :            :   return true;
     502                 :            : }
     503                 :            : 
     504                 :            : /* A case_bit_test represents a set of case nodes that may be
     505                 :            :    selected from using a bit-wise comparison.  HI and LO hold
     506                 :            :    the integer to be tested against, TARGET_EDGE contains the
     507                 :            :    edge to the basic block to jump to upon success and BITS
     508                 :            :    counts the number of case nodes handled by this test,
     509                 :            :    typically the number of bits set in HI:LO.  The LABEL field
     510                 :            :    is used to quickly identify all cases in this set without
     511                 :            :    looking at label_to_block for every case label.  */
     512                 :            : 
     513                 :            : class case_bit_test
     514                 :            : {
     515                 :            : public:
     516                 :            :   wide_int mask;
     517                 :            :   basic_block target_bb;
     518                 :            :   tree label;
     519                 :            :   int bits;
     520                 :            : 
     521                 :            :   /* Comparison function for qsort to order bit tests by decreasing
     522                 :            :      probability of execution.  */
     523                 :            :   static int cmp (const void *p1, const void *p2);
     524                 :            : };
     525                 :            : 
     526                 :            : class switch_decision_tree
     527                 :            : {
     528                 :            : public:
     529                 :            :   /* Constructor.  */
     530                 :      28465 :   switch_decision_tree (gswitch *swtch): m_switch (swtch), m_phi_mapping (),
     531                 :            :     m_case_bbs (), m_case_node_pool ("struct case_node pool"),
     532                 :      28465 :     m_case_list (NULL)
     533                 :            :   {
     534                 :      28465 :   }
     535                 :            : 
     536                 :            :   /* Analyze switch statement and return true when the statement is expanded
     537                 :            :      as decision tree.  */
     538                 :            :   bool analyze_switch_statement ();
     539                 :            : 
     540                 :            :   /* Attempt to expand CLUSTERS as a decision tree.  Return true when
     541                 :            :      expanded.  */
     542                 :            :   bool try_switch_expansion (vec<cluster *> &clusters);
     543                 :            :   /* Compute the number of case labels that correspond to each outgoing edge of
     544                 :            :      switch statement.  Record this information in the aux field of the edge.
     545                 :            :      */
     546                 :            :   void compute_cases_per_edge ();
     547                 :            : 
     548                 :            :   /* Before switch transformation, record all SSA_NAMEs defined in switch BB
     549                 :            :      and used in a label basic block.  */
     550                 :            :   void record_phi_operand_mapping ();
     551                 :            : 
     552                 :            :   /* Append new operands to PHI statements that were introduced due to
     553                 :            :      addition of new edges to case labels.  */
     554                 :            :   void fix_phi_operands_for_edges ();
     555                 :            : 
     556                 :            :   /* Generate a decision tree, switching on INDEX_EXPR and jumping to
     557                 :            :      one of the labels in CASE_LIST or to the DEFAULT_LABEL.
     558                 :            : 
     559                 :            :      We generate a binary decision tree to select the appropriate target
     560                 :            :      code.  */
     561                 :            :   void emit (basic_block bb, tree index_expr,
     562                 :            :              profile_probability default_prob, tree index_type);
     563                 :            : 
     564                 :            :   /* Emit step-by-step code to select a case for the value of INDEX.
     565                 :            :      The thus generated decision tree follows the form of the
     566                 :            :      case-node binary tree NODE, whose nodes represent test conditions.
     567                 :            :      DEFAULT_PROB is probability of cases leading to default BB.
     568                 :            :      INDEX_TYPE is the type of the index of the switch.  */
     569                 :            :   basic_block emit_case_nodes (basic_block bb, tree index,
     570                 :            :                                case_tree_node *node,
     571                 :            :                                profile_probability default_prob,
     572                 :            :                                tree index_type, location_t);
     573                 :            : 
     574                 :            :   /* Take an ordered list of case nodes
     575                 :            :      and transform them into a near optimal binary tree,
     576                 :            :      on the assumption that any target code selection value is as
     577                 :            :      likely as any other.
     578                 :            : 
     579                 :            :      The transformation is performed by splitting the ordered
     580                 :            :      list into two equal sections plus a pivot.  The parts are
     581                 :            :      then attached to the pivot as left and right branches.  Each
     582                 :            :      branch is then transformed recursively.  */
     583                 :            :   static void balance_case_nodes (case_tree_node **head,
     584                 :            :                                   case_tree_node *parent);
     585                 :            : 
     586                 :            :   /* Dump ROOT, a list or tree of case nodes, to file F.  */
     587                 :            :   static void dump_case_nodes (FILE *f, case_tree_node *root, int indent_step,
     588                 :            :                                int indent_level);
     589                 :            : 
     590                 :            :   /* Add an unconditional jump to CASE_BB that happens in basic block BB.  */
     591                 :            :   static void emit_jump (basic_block bb, basic_block case_bb);
     592                 :            : 
     593                 :            :   /* Generate code to compare OP0 with OP1 so that the condition codes are
     594                 :            :      set and to jump to LABEL_BB if the condition is true.
     595                 :            :      COMPARISON is the GIMPLE comparison (EQ, NE, GT, etc.).
     596                 :            :      PROB is the probability of jumping to LABEL_BB.  */
     597                 :            :   static basic_block emit_cmp_and_jump_insns (basic_block bb, tree op0,
     598                 :            :                                               tree op1, tree_code comparison,
     599                 :            :                                               basic_block label_bb,
     600                 :            :                                               profile_probability prob,
     601                 :            :                                               location_t);
     602                 :            : 
     603                 :            :   /* Generate code to jump to LABEL if OP0 and OP1 are equal in mode MODE.
     604                 :            :      PROB is the probability of jumping to LABEL_BB.  */
     605                 :            :   static basic_block do_jump_if_equal (basic_block bb, tree op0, tree op1,
     606                 :            :                                        basic_block label_bb,
     607                 :            :                                        profile_probability prob,
     608                 :            :                                        location_t);
     609                 :            : 
     610                 :            :   /* Reset the aux field of all outgoing edges of switch basic block.  */
     611                 :            :   static inline void reset_out_edges_aux (gswitch *swtch);
     612                 :            : 
     613                 :            :   /* Switch statement.  */
     614                 :            :   gswitch *m_switch;
     615                 :            : 
     616                 :            :   /* Map of PHI nodes that have to be fixed after expansion.  */
     617                 :            :   hash_map<tree, tree> m_phi_mapping;
     618                 :            : 
     619                 :            :   /* List of basic blocks that belong to labels of the switch.  */
     620                 :            :   auto_vec<basic_block> m_case_bbs;
     621                 :            : 
     622                 :            :   /* Basic block with default label.  */
     623                 :            :   basic_block m_default_bb;
     624                 :            : 
     625                 :            :   /* A pool for case nodes.  */
     626                 :            :   object_allocator<case_tree_node> m_case_node_pool;
     627                 :            : 
     628                 :            :   /* Balanced tree of case nodes.  */
     629                 :            :   case_tree_node *m_case_list;
     630                 :            : };
     631                 :            : 
     632                 :            : /*
     633                 :            :      Switch initialization conversion
     634                 :            : 
     635                 :            : The following pass changes simple initializations of scalars in a switch
     636                 :            : statement into initializations from a static array.  Obviously, the values
     637                 :            : must be constant and known at compile time and a default branch must be
     638                 :            : provided.  For example, the following code:
     639                 :            : 
     640                 :            :         int a,b;
     641                 :            : 
     642                 :            :         switch (argc)
     643                 :            :         {
     644                 :            :          case 1:
     645                 :            :          case 2:
     646                 :            :                 a_1 = 8;
     647                 :            :                 b_1 = 6;
     648                 :            :                 break;
     649                 :            :          case 3:
     650                 :            :                 a_2 = 9;
     651                 :            :                 b_2 = 5;
     652                 :            :                 break;
     653                 :            :          case 12:
     654                 :            :                 a_3 = 10;
     655                 :            :                 b_3 = 4;
     656                 :            :                 break;
     657                 :            :          default:
     658                 :            :                 a_4 = 16;
     659                 :            :                 b_4 = 1;
     660                 :            :                 break;
     661                 :            :         }
     662                 :            :         a_5 = PHI <a_1, a_2, a_3, a_4>
     663                 :            :         b_5 = PHI <b_1, b_2, b_3, b_4>
     664                 :            : 
     665                 :            : 
     666                 :            : is changed into:
     667                 :            : 
     668                 :            :         static const int = CSWTCH01[] = {6, 6, 5, 1, 1, 1, 1, 1, 1, 1, 1, 4};
     669                 :            :         static const int = CSWTCH02[] = {8, 8, 9, 16, 16, 16, 16, 16, 16, 16,
     670                 :            :                                  16, 16, 10};
     671                 :            : 
     672                 :            :         if (((unsigned) argc) - 1 < 11)
     673                 :            :           {
     674                 :            :             a_6 = CSWTCH02[argc - 1];
     675                 :            :             b_6 = CSWTCH01[argc - 1];
     676                 :            :           }
     677                 :            :         else
     678                 :            :           {
     679                 :            :             a_7 = 16;
     680                 :            :             b_7 = 1;
     681                 :            :           }
     682                 :            :         a_5 = PHI <a_6, a_7>
     683                 :            :         b_b = PHI <b_6, b_7>
     684                 :            : 
     685                 :            : There are further constraints.  Specifically, the range of values across all
     686                 :            : case labels must not be bigger than param_switch_conversion_branch_ratio
     687                 :            : (default eight) times the number of the actual switch branches.
     688                 :            : 
     689                 :            : This transformation was contributed by Martin Jambor, see this e-mail:
     690                 :            :    http://gcc.gnu.org/ml/gcc-patches/2008-07/msg00011.html  */
     691                 :            : 
     692                 :            : /* The main structure of the pass.  */
     693                 :            : class switch_conversion
     694                 :            : {
     695                 :            : public:
     696                 :            :   /* Constructor.  */
     697                 :            :   switch_conversion ();
     698                 :            : 
     699                 :            :   /* Destructor.  */
     700                 :            :   ~switch_conversion ();
     701                 :            : 
     702                 :            :   /* The following function is invoked on every switch statement (the current
     703                 :            :      one is given in SWTCH) and runs the individual phases of switch
     704                 :            :      conversion on it one after another until one fails or the conversion
     705                 :            :      is completed.  On success, NULL is in m_reason, otherwise points
     706                 :            :      to a string with the reason why the conversion failed.  */
     707                 :            :   void expand (gswitch *swtch);
     708                 :            : 
     709                 :            :   /* Collection information about SWTCH statement.  */
     710                 :            :   void collect (gswitch *swtch);
     711                 :            : 
     712                 :            :   /* Checks whether the range given by individual case statements of the switch
     713                 :            :      switch statement isn't too big and whether the number of branches actually
     714                 :            :      satisfies the size of the new array.  */
     715                 :            :   bool check_range ();
     716                 :            : 
     717                 :            :   /* Checks whether all but the final BB basic blocks are empty.  */
     718                 :            :   bool check_all_empty_except_final ();
     719                 :            : 
     720                 :            :   /* This function checks whether all required values in phi nodes in final_bb
     721                 :            :      are constants.  Required values are those that correspond to a basic block
     722                 :            :      which is a part of the examined switch statement.  It returns true if the
     723                 :            :      phi nodes are OK, otherwise false.  */
     724                 :            :   bool check_final_bb ();
     725                 :            : 
     726                 :            :   /* The following function allocates default_values, target_{in,out}_names and
     727                 :            :      constructors arrays.  The last one is also populated with pointers to
     728                 :            :      vectors that will become constructors of new arrays.  */
     729                 :            :   void create_temp_arrays ();
     730                 :            : 
     731                 :            :   /* Populate the array of default values in the order of phi nodes.
     732                 :            :      DEFAULT_CASE is the CASE_LABEL_EXPR for the default switch branch
     733                 :            :      if the range is non-contiguous or the default case has standard
     734                 :            :      structure, otherwise it is the first non-default case instead.  */
     735                 :            :   void gather_default_values (tree default_case);
     736                 :            : 
     737                 :            :   /* The following function populates the vectors in the constructors array with
     738                 :            :      future contents of the static arrays.  The vectors are populated in the
     739                 :            :      order of phi nodes.  */
     740                 :            :   void build_constructors ();
     741                 :            : 
     742                 :            :   /* If all values in the constructor vector are products of a linear function
     743                 :            :      a * x + b, then return true.  When true, COEFF_A and COEFF_B and
     744                 :            :      coefficients of the linear function.  Note that equal values are special
     745                 :            :      case of a linear function with a and b equal to zero.  */
     746                 :            :   bool contains_linear_function_p (vec<constructor_elt, va_gc> *vec,
     747                 :            :                                    wide_int *coeff_a, wide_int *coeff_b);
     748                 :            : 
     749                 :            :   /* Return type which should be used for array elements, either TYPE's
     750                 :            :      main variant or, for integral types, some smaller integral type
     751                 :            :      that can still hold all the constants.  */
     752                 :            :   tree array_value_type (tree type, int num);
     753                 :            : 
     754                 :            :   /* Create an appropriate array type and declaration and assemble a static
     755                 :            :      array variable.  Also create a load statement that initializes
     756                 :            :      the variable in question with a value from the static array.  SWTCH is
     757                 :            :      the switch statement being converted, NUM is the index to
     758                 :            :      arrays of constructors, default values and target SSA names
     759                 :            :      for this particular array.  ARR_INDEX_TYPE is the type of the index
     760                 :            :      of the new array, PHI is the phi node of the final BB that corresponds
     761                 :            :      to the value that will be loaded from the created array.  TIDX
     762                 :            :      is an ssa name of a temporary variable holding the index for loads from the
     763                 :            :      new array.  */
     764                 :            :   void build_one_array (int num, tree arr_index_type,
     765                 :            :                         gphi *phi, tree tidx);
     766                 :            : 
     767                 :            :   /* Builds and initializes static arrays initialized with values gathered from
     768                 :            :      the switch statement.  Also creates statements that load values from
     769                 :            :      them.  */
     770                 :            :   void build_arrays ();
     771                 :            : 
     772                 :            :   /* Generates and appropriately inserts loads of default values at the position
     773                 :            :      given by GSI.  Returns the last inserted statement.  */
     774                 :            :   gassign *gen_def_assigns (gimple_stmt_iterator *gsi);
     775                 :            : 
     776                 :            :   /* Deletes the unused bbs and edges that now contain the switch statement and
     777                 :            :      its empty branch bbs.  BBD is the now dead BB containing
     778                 :            :      the original switch statement, FINAL is the last BB of the converted
     779                 :            :      switch statement (in terms of succession).  */
     780                 :            :   void prune_bbs (basic_block bbd, basic_block final, basic_block default_bb);
     781                 :            : 
     782                 :            :   /* Add values to phi nodes in final_bb for the two new edges.  E1F is the edge
     783                 :            :      from the basic block loading values from an array and E2F from the basic
     784                 :            :      block loading default values.  BBF is the last switch basic block (see the
     785                 :            :      bbf description in the comment below).  */
     786                 :            :   void fix_phi_nodes (edge e1f, edge e2f, basic_block bbf);
     787                 :            : 
     788                 :            :   /* Creates a check whether the switch expression value actually falls into the
     789                 :            :      range given by all the cases.  If it does not, the temporaries are loaded
     790                 :            :      with default values instead.  */
     791                 :            :   void gen_inbound_check ();
     792                 :            : 
     793                 :            :   /* Switch statement for which switch conversion takes place.  */
     794                 :            :   gswitch *m_switch;
     795                 :            : 
     796                 :            :   /* The expression used to decide the switch branch.  */
     797                 :            :   tree m_index_expr;
     798                 :            : 
     799                 :            :   /* The following integer constants store the minimum and maximum value
     800                 :            :      covered by the case labels.  */
     801                 :            :   tree m_range_min;
     802                 :            :   tree m_range_max;
     803                 :            : 
     804                 :            :   /* The difference between the above two numbers.  Stored here because it
     805                 :            :      is used in all the conversion heuristics, as well as for some of the
     806                 :            :      transformation, and it is expensive to re-compute it all the time.  */
     807                 :            :   tree m_range_size;
     808                 :            : 
     809                 :            :   /* Basic block that contains the actual GIMPLE_SWITCH.  */
     810                 :            :   basic_block m_switch_bb;
     811                 :            : 
     812                 :            :   /* Basic block that is the target of the default case.  */
     813                 :            :   basic_block m_default_bb;
     814                 :            : 
     815                 :            :   /* The single successor block of all branches out of the GIMPLE_SWITCH,
     816                 :            :      if such a block exists.  Otherwise NULL.  */
     817                 :            :   basic_block m_final_bb;
     818                 :            : 
     819                 :            :   /* The probability of the default edge in the replaced switch.  */
     820                 :            :   profile_probability m_default_prob;
     821                 :            : 
     822                 :            :   /* Number of phi nodes in the final bb (that we'll be replacing).  */
     823                 :            :   int m_phi_count;
     824                 :            : 
     825                 :            :   /* Constructors of new static arrays.  */
     826                 :            :   vec<constructor_elt, va_gc> **m_constructors;
     827                 :            : 
     828                 :            :   /* Array of default values, in the same order as phi nodes.  */
     829                 :            :   tree *m_default_values;
     830                 :            : 
     831                 :            :   /* Array of ssa names that are initialized with a value from a new static
     832                 :            :      array.  */
     833                 :            :   tree *m_target_inbound_names;
     834                 :            : 
     835                 :            :   /* Array of ssa names that are initialized with the default value if the
     836                 :            :      switch expression is out of range.  */
     837                 :            :   tree *m_target_outbound_names;
     838                 :            : 
     839                 :            :   /* VOP SSA_NAME.  */
     840                 :            :   tree m_target_vop;
     841                 :            : 
     842                 :            :   /* The first load statement that loads a temporary from a new static array.
     843                 :            :    */
     844                 :            :   gimple *m_arr_ref_first;
     845                 :            : 
     846                 :            :   /* The last load statement that loads a temporary from a new static array.  */
     847                 :            :   gimple *m_arr_ref_last;
     848                 :            : 
     849                 :            :   /* String reason why the case wasn't a good candidate that is written to the
     850                 :            :      dump file, if there is one.  */
     851                 :            :   const char *m_reason;
     852                 :            : 
     853                 :            :   /* True if default case is not used for any value between range_min and
     854                 :            :      range_max inclusive.  */
     855                 :            :   bool m_contiguous_range;
     856                 :            : 
     857                 :            :   /* True if default case does not have the required shape for other case
     858                 :            :      labels.  */
     859                 :            :   bool m_default_case_nonstandard;
     860                 :            : 
     861                 :            :   /* Number of uniq labels for non-default edges.  */
     862                 :            :   unsigned int m_uniq;
     863                 :            : 
     864                 :            :   /* Count is number of non-default edges.  */
     865                 :            :   unsigned int m_count;
     866                 :            : 
     867                 :            :   /* True if CFG has been changed.  */
     868                 :            :   bool m_cfg_altered;
     869                 :            : };
     870                 :            : 
     871                 :            : void
     872                 :      66799 : switch_decision_tree::reset_out_edges_aux (gswitch *swtch)
     873                 :            : {
     874                 :      66799 :   basic_block bb = gimple_bb (swtch);
     875                 :      66799 :   edge e;
     876                 :      66799 :   edge_iterator ei;
     877                 :     411796 :   FOR_EACH_EDGE (e, ei, bb->succs)
     878                 :     344997 :     e->aux = (void *) 0;
     879                 :      66799 : }
     880                 :            : 
     881                 :            : } // tree_switch_conversion namespace
     882                 :            : 
     883                 :            : #endif // TREE_SWITCH_CONVERSION_H

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.