LCOV - code coverage report
Current view: top level - gcc - opt-problem.h (source / functions) Hit Total Coverage
Test: gcc.info Lines: 33 33 100.0 %
Date: 2020-04-04 11:58:09 Functions: 2 2 100.0 %
Legend: Lines: hit not hit | Branches: + taken - not taken # not executed Branches: 0 0 -

           Branch data     Line data    Source code
       1                 :            : /* Rich information on why an optimization wasn't possible.
       2                 :            :    Copyright (C) 2018-2020 Free Software Foundation, Inc.
       3                 :            :    Contributed by David Malcolm <dmalcolm@redhat.com>.
       4                 :            : 
       5                 :            : This file is part of GCC.
       6                 :            : 
       7                 :            : GCC is free software; you can redistribute it and/or modify it under
       8                 :            : the terms of the GNU General Public License as published by the Free
       9                 :            : Software Foundation; either version 3, or (at your option) any later
      10                 :            : version.
      11                 :            : 
      12                 :            : GCC is distributed in the hope that it will be useful, but WITHOUT ANY
      13                 :            : WARRANTY; without even the implied warranty of MERCHANTABILITY or
      14                 :            : FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
      15                 :            : for more details.
      16                 :            : 
      17                 :            : You should have received a copy of the GNU General Public License
      18                 :            : along with GCC; see the file COPYING3.  If not see
      19                 :            : <http://www.gnu.org/licenses/>.  */
      20                 :            : 
      21                 :            : #ifndef GCC_OPT_PROBLEM_H
      22                 :            : #define GCC_OPT_PROBLEM_H
      23                 :            : 
      24                 :            : #include "diagnostic-core.h" /* for ATTRIBUTE_GCC_DIAG.  */
      25                 :            : #include "optinfo.h" /* for optinfo.  */
      26                 :            : 
      27                 :            : /* This header declares a family of wrapper classes for tracking a
      28                 :            :    success/failure value, while optionally supporting propagating an
      29                 :            :    opt_problem * describing any failure back up the call stack.
      30                 :            : 
      31                 :            :    For instance, at the deepest point of the callstack where the failure
      32                 :            :    happens, rather than:
      33                 :            : 
      34                 :            :      if (!check_something ())
      35                 :            :        {
      36                 :            :          if (dump_enabled_p ())
      37                 :            :            dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
      38                 :            :                             "foo is unsupported.\n");
      39                 :            :          return false;
      40                 :            :        }
      41                 :            :      // [...more checks...]
      42                 :            : 
      43                 :            :      // All checks passed:
      44                 :            :      return true;
      45                 :            : 
      46                 :            :    we can capture the cause of the failure via:
      47                 :            : 
      48                 :            :      if (!check_something ())
      49                 :            :        return opt_result::failure_at (stmt, "foo is unsupported");
      50                 :            :      // [...more checks...]
      51                 :            : 
      52                 :            :      // All checks passed:
      53                 :            :      return opt_result::success ();
      54                 :            : 
      55                 :            :    which effectively returns true or false, whilst recording any problem.
      56                 :            : 
      57                 :            :    opt_result::success and opt_result::failure return opt_result values
      58                 :            :    which "looks like" true/false respectively, via operator bool().
      59                 :            :    If dump_enabled_p, then opt_result::failure also creates an opt_problem *,
      60                 :            :    capturing the pertinent data (here, "foo is unsupported " and "stmt").
      61                 :            :    If dumps are disabled, then opt_problem instances aren't
      62                 :            :    created, and it's equivalent to just returning a bool.
      63                 :            : 
      64                 :            :    The opt_problem can be propagated via opt_result values back up
      65                 :            :    the call stack to where it makes most sense to the user.
      66                 :            :    For instance, rather than:
      67                 :            : 
      68                 :            :      bool ok = try_something_that_might_fail ();
      69                 :            :      if (!ok)
      70                 :            :        {
      71                 :            :          if (dump_enabled_p ())
      72                 :            :            dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
      73                 :            :                             "some message.\n");
      74                 :            :          return false;
      75                 :            :        }
      76                 :            : 
      77                 :            :    we can replace the bool with an opt_result, so if dump_enabled_p, we
      78                 :            :    assume that if try_something_that_might_fail, an opt_problem * will be
      79                 :            :    created, and we can propagate it up the call chain:
      80                 :            : 
      81                 :            :      opt_result ok = try_something_that_might_fail ();
      82                 :            :      if (!ok)
      83                 :            :        {
      84                 :            :          if (dump_enabled_p ())
      85                 :            :            dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
      86                 :            :                             "some message.\n");
      87                 :            :          return ok; // propagating the opt_result
      88                 :            :        }
      89                 :            : 
      90                 :            :    opt_result is an opt_wrapper<bool>, where opt_wrapper<T> is a base
      91                 :            :    class for wrapping a T, optionally propagating an opt_problem in
      92                 :            :    case of failure_at (when dumps are enabled).  Similarly,
      93                 :            :    opt_pointer_wrapper<T> can be used to wrap pointer types (where non-NULL
      94                 :            :    signifies success, NULL signifies failure).
      95                 :            : 
      96                 :            :    In all cases, opt_wrapper<T> acts as if the opt_problem were one of its
      97                 :            :    fields, but the opt_problem is actually stored in a global, so that when
      98                 :            :    compiled, an opt_wrapper<T> is effectively just a T, so that we're
      99                 :            :    still just passing e.g. a bool around; the opt_wrapper<T> classes
     100                 :            :    simply provide type-checking and an API to ensure that we provide
     101                 :            :    error-messages deep in the callstack at the places where problems
     102                 :            :    occur, and that we propagate them.  This also avoids having
     103                 :            :    to manage the ownership of the opt_problem instances.
     104                 :            : 
     105                 :            :    Using opt_result and opt_wrapper<T> documents the intent of the code
     106                 :            :    for the places where we represent success values, and allows the C++ type
     107                 :            :    system to track where the deepest points in the callstack are where we
     108                 :            :    need to emit the failure messages from.  */
     109                 :            : 
     110                 :            : /* A bundle of information about why an optimization failed (e.g.
     111                 :            :    vectorization), and the location in both the user's code and
     112                 :            :    in GCC itself where the problem occurred.
     113                 :            : 
     114                 :            :    Instances are created by static member functions in opt_wrapper
     115                 :            :    subclasses, such as opt_result::failure.
     116                 :            : 
     117                 :            :    Instances are only created when dump_enabled_p ().  */
     118                 :            : 
     119                 :      13131 : class opt_problem
     120                 :            : {
     121                 :            :  public:
     122                 :      57165 :   static opt_problem *get_singleton () { return s_the_problem; }
     123                 :            : 
     124                 :            :   opt_problem (const dump_location_t &loc,
     125                 :            :                const char *fmt, va_list *ap)
     126                 :            :     ATTRIBUTE_GCC_DUMP_PRINTF (3, 0);
     127                 :            : 
     128                 :            :   const dump_location_t &
     129                 :        224 :   get_dump_location () const { return m_optinfo.get_dump_location (); }
     130                 :            : 
     131                 :        112 :   const optinfo & get_optinfo () const { return m_optinfo; }
     132                 :            : 
     133                 :            :   void emit_and_clear ();
     134                 :            : 
     135                 :            :  private:
     136                 :            :   optinfo m_optinfo;
     137                 :            : 
     138                 :            :   static opt_problem *s_the_problem;
     139                 :            : };
     140                 :            : 
     141                 :            : /* A base class for wrapper classes that track a success/failure value, while
     142                 :            :    optionally supporting propagating an opt_problem * describing any
     143                 :            :    failure back up the call stack.  */
     144                 :            : 
     145                 :            : template <typename T>
     146                 :            : class opt_wrapper
     147                 :            : {
     148                 :            :  public:
     149                 :            :   typedef T wrapped_t;
     150                 :            : 
     151                 :            :   /* Be accessible as the wrapped type.  */
     152                 :   15880763 :   operator wrapped_t () const { return m_result; }
     153                 :            : 
     154                 :            :   /* No public ctor.  */
     155                 :            : 
     156                 :     263109 :   wrapped_t get_result () const { return m_result; }
     157                 :      57165 :   opt_problem *get_problem () const { return opt_problem::get_singleton (); }
     158                 :            : 
     159                 :            :  protected:
     160                 :   17079342 :   opt_wrapper (wrapped_t result, opt_problem */*problem*/)
     161                 :            :   : m_result (result)
     162                 :            :   {
     163                 :            :     /* "problem" is ignored: although it looks like a field, we
     164                 :            :        actually just use the opt_problem singleton, so that
     165                 :            :        opt_wrapper<T> in memory is just a T.  */
     166                 :            :   }
     167                 :            : 
     168                 :            :  private:
     169                 :            :   wrapped_t m_result;
     170                 :            : };
     171                 :            : 
     172                 :            : /* Subclass of opt_wrapper<T> for bool, where
     173                 :            :    - true signifies "success", and
     174                 :            :    - false signifies "failure"
     175                 :            :    whilst effectively propagating an opt_problem * describing any failure
     176                 :            :    back up the call stack.  */
     177                 :            : 
     178                 :            : class opt_result : public opt_wrapper <bool>
     179                 :            : {
     180                 :            :  public:
     181                 :            :   /* Generate a "success" value: a wrapper around "true".  */
     182                 :            : 
     183                 :   16347221 :   static opt_result success () { return opt_result (true, NULL); }
     184                 :            : 
     185                 :            :   /* Generate a "failure" value: a wrapper around "false", and,
     186                 :            :      if dump_enabled_p, an opt_problem.  */
     187                 :            : 
     188                 :     479858 :   static opt_result failure_at (const dump_location_t &loc,
     189                 :            :                                 const char *fmt, ...)
     190                 :            :           ATTRIBUTE_GCC_DUMP_PRINTF (2, 3)
     191                 :            :   {
     192                 :     479858 :     opt_problem *problem = NULL;
     193                 :     479858 :     if (dump_enabled_p ())
     194                 :            :       {
     195                 :      13205 :         va_list ap;
     196                 :      13205 :         va_start (ap, fmt);
     197                 :      13205 :         problem = new opt_problem (loc, fmt, &ap);
     198                 :      13205 :         va_end (ap);
     199                 :            :       }
     200                 :     479858 :     return opt_result (false, problem);
     201                 :            :   }
     202                 :            : 
     203                 :            :   /* Given a failure wrapper of some other kind, make an opt_result failure
     204                 :            :      object, for propagating the opt_problem up the call stack.  */
     205                 :            : 
     206                 :            :   template <typename S>
     207                 :            :   static opt_result
     208                 :            :   propagate_failure (opt_wrapper <S> other)
     209                 :            :   {
     210                 :            :     return opt_result (false, other.get_problem ());
     211                 :            :   }
     212                 :            : 
     213                 :            :  private:
     214                 :            :   /* Private ctor.  Instances should be created by the success and failure
     215                 :            :      static member functions.  */
     216                 :   16827081 :   opt_result (wrapped_t result, opt_problem *problem)
     217                 :   16347221 :   : opt_wrapper <bool> (result, problem)
     218                 :            :   {}
     219                 :            : };
     220                 :            : 
     221                 :            : /* Subclass of opt_wrapper<T> where T is a pointer type, for tracking
     222                 :            :    success/failure, where:
     223                 :            :    - a non-NULL value signifies "success", and
     224                 :            :    - a NULL value signifies "failure",
     225                 :            :    whilst effectively propagating an opt_problem * describing any failure
     226                 :            :    back up the call stack.  */
     227                 :            : 
     228                 :            : template <typename PtrType_t>
     229                 :            : class opt_pointer_wrapper : public opt_wrapper <PtrType_t>
     230                 :            : {
     231                 :            :  public:
     232                 :            :   typedef PtrType_t wrapped_pointer_t;
     233                 :            : 
     234                 :            :   /* Given a non-NULL pointer, make a success object wrapping it.  */
     235                 :            : 
     236                 :            :   static opt_pointer_wrapper <wrapped_pointer_t>
     237                 :     197964 :   success (wrapped_pointer_t ptr)
     238                 :            :   {
     239                 :     273255 :     return opt_pointer_wrapper <wrapped_pointer_t> (ptr, NULL);
     240                 :            :   }
     241                 :            : 
     242                 :            :   /* Make a NULL pointer failure object, with the given message
     243                 :            :      (if dump_enabled_p).  */
     244                 :            : 
     245                 :            :   static opt_pointer_wrapper <wrapped_pointer_t>
     246                 :       4038 :   failure_at (const dump_location_t &loc,
     247                 :            :               const char *fmt, ...)
     248                 :            :     ATTRIBUTE_GCC_DUMP_PRINTF (2, 3)
     249                 :            :   {
     250                 :       4038 :     opt_problem *problem = NULL;
     251                 :       4038 :     if (dump_enabled_p ())
     252                 :            :       {
     253                 :            :         va_list ap;
     254                 :        557 :         va_start (ap, fmt);
     255                 :        557 :         problem = new opt_problem (loc, fmt, &ap);
     256                 :        557 :         va_end (ap);
     257                 :            :       }
     258                 :       4038 :     return opt_pointer_wrapper <wrapped_pointer_t> (NULL, problem);
     259                 :            :   }
     260                 :            : 
     261                 :            :   /* Given a failure wrapper of some other kind, make a NULL pointer
     262                 :            :      failure object, propagating the problem.  */
     263                 :            : 
     264                 :            :   template <typename S>
     265                 :            :   static opt_pointer_wrapper <wrapped_pointer_t>
     266                 :      50265 :   propagate_failure (opt_wrapper <S> other)
     267                 :            :   {
     268                 :            :     return opt_pointer_wrapper <wrapped_pointer_t> (NULL,
     269                 :      50265 :                                                     other.get_problem ());
     270                 :            :   }
     271                 :            : 
     272                 :            :   /* Support accessing the underlying pointer via ->.  */
     273                 :            : 
     274                 :     233658 :   wrapped_pointer_t operator-> () const { return this->get_result (); }
     275                 :            : 
     276                 :            :  private:
     277                 :            :   /* Private ctor.  Instances should be built using the static member
     278                 :            :      functions "success" and "failure".  */
     279                 :     252267 :   opt_pointer_wrapper (wrapped_pointer_t result, opt_problem *problem)
     280                 :     320252 :   : opt_wrapper<PtrType_t> (result, problem)
     281                 :            :   {}
     282                 :            : };
     283                 :            : 
     284                 :            : /* A typedef for wrapping "tree" so that NULL_TREE can carry an
     285                 :            :    opt_problem describing the failure (if dump_enabled_p).  */
     286                 :            : 
     287                 :            : typedef opt_pointer_wrapper<tree> opt_tree;
     288                 :            : 
     289                 :            : #endif /* #ifndef GCC_OPT_PROBLEM_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.