gcc/ipa-modref.h

   1 /* Search for references that a functions loads or stores.
   2    Copyright (C) 2019-2022 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 IPA_MODREF_H
  21 #define IPA_MODREF_H
  22
  23 typedef modref_tree <alias_set_type> modref_records;
  24 typedef unsigned short eaf_flags_t;
  25
  26 /* Single function summary.  */
  27
  28 struct GTY(()) modref_summary
  29 {
  30   /* Load and stores in function (transitively closed to all callees)  */
  31   modref_records *loads;
  32   modref_records *stores;
  33   auto_vec<modref_access_node> GTY((skip)) kills;
  34   auto_vec<eaf_flags_t> GTY((skip)) arg_flags;
  35
  36   eaf_flags_t retslot_flags;
  37   eaf_flags_t static_chain_flags;
  38
  39   unsigned writes_errno : 1;
  40   /* Side effects does not include memory loads and stores which are
  41      expressed using loads, stores and calls_interposable fields.  */
  42   unsigned side_effects : 1;
  43   /* If true function can not be CSE optimized because it may behave
  44      differently even if invoked with same inputs.  */
  45   unsigned nondeterministic : 1;
  46   /* IF true the function may read any reachable memory but not use
  47      it for anything useful.  This may happen i.e. when interposing
  48      function with optimized out conditional with unoptimized one.
  49
  50      In this situation the loads summary is not useful for DSE but
  51      it is still useful for CSE.  */
  52   unsigned calls_interposable : 1;
  53
  54   /* Flags computed by finalize method.  */
  55
  56   /* Total number of accesses in loads tree.  */
  57   unsigned int load_accesses;
  58   /* global_memory_read is not set for functions calling functions
  59      with !binds_to_current_def which, after interposition, may read global
  60      memory but do nothing useful with it (except for crashing if some
  61      stores are optimized out.  */
  62   unsigned global_memory_read : 1;
  63   unsigned global_memory_written : 1;
  64   unsigned try_dse : 1;
  65
  66
  67   modref_summary ();
  68   ~modref_summary ();
  69   void dump (FILE *);
  70   bool useful_p (int ecf_flags, bool check_flags = true);
  71   void finalize (tree);
  72 };
  73
  74 modref_summary *get_modref_function_summary (cgraph_node *func);
  75 modref_summary *get_modref_function_summary (gcall *call, bool *interposed);
  76 void ipa_modref_cc_finalize ();
  77 void ipa_merge_modref_summary_after_inlining (cgraph_edge *e);
  78
  79 /* All flags that are implied by the ECF_CONST functions.  */
  80 static const int implicit_const_eaf_flags
  81    = EAF_NO_DIRECT_CLOBBER | EAF_NO_INDIRECT_CLOBBER
  82     | EAF_NO_DIRECT_ESCAPE | EAF_NO_INDIRECT_ESCAPE
  83     | EAF_NO_DIRECT_READ | EAF_NO_INDIRECT_READ
  84     | EAF_NOT_RETURNED_INDIRECTLY;
  85
  86 /* All flags that are implied by the ECF_PURE function.  */
  87 static const int implicit_pure_eaf_flags
  88    = EAF_NO_DIRECT_CLOBBER | EAF_NO_INDIRECT_CLOBBER
  89     | EAF_NO_DIRECT_ESCAPE | EAF_NO_INDIRECT_ESCAPE;
  90
  91 /* All flags implied when we know we can ignore stores (i.e. when handling
  92    call to noreturn).  */
  93 static const int ignore_stores_eaf_flags
  94    = EAF_NO_DIRECT_CLOBBER | EAF_NO_INDIRECT_CLOBBER
  95     | EAF_NO_DIRECT_ESCAPE | EAF_NO_INDIRECT_ESCAPE;
  96
  97 /* Return slot is write-only.  */
  98 static const int implicit_retslot_eaf_flags
  99    = EAF_NO_DIRECT_READ | EAF_NO_INDIRECT_READ
 100      | EAF_NO_INDIRECT_ESCAPE | EAF_NO_INDIRECT_CLOBBER
 101      | EAF_NOT_RETURNED_INDIRECTLY;
 102
 103 /* If function does not bind to current def (i.e. it is inline in comdat
 104    section), the modref analysis may not match the behavior of function
 105    which will be later symbol interposed to.  All side effects must match
 106    however it is possible that the other function body contains more loads
 107    which may trap.
 108    MODREF_FLAGS are flags determined by analysis of function body while
 109    FLAGS are flags known otherwise (i.e. by fnspec, pure/const attributes
 110    etc.)  */
 111 static inline int
 112 interposable_eaf_flags (int modref_flags, int flags)
 113 {
 114   /* If parameter was previously unused, we know it is only read
 115      and its value is not used.  */
 116   if ((modref_flags & EAF_UNUSED) && !(flags & EAF_UNUSED))
 117     {
 118       modref_flags &= ~EAF_UNUSED;
 119       modref_flags |= EAF_NO_DIRECT_ESCAPE | EAF_NO_INDIRECT_ESCAPE
 120                       | EAF_NOT_RETURNED_DIRECTLY | EAF_NOT_RETURNED_INDIRECTLY
 121                       | EAF_NO_DIRECT_CLOBBER | EAF_NO_INDIRECT_CLOBBER;
 122     }
 123   /* We can not determine that value is not read at all.  */
 124   if ((modref_flags & EAF_NO_DIRECT_READ) && !(flags & EAF_NO_DIRECT_READ))
 125     modref_flags &= ~EAF_NO_DIRECT_READ;
 126   if ((modref_flags & EAF_NO_INDIRECT_READ) && !(flags & EAF_NO_INDIRECT_READ))
 127     modref_flags &= ~EAF_NO_INDIRECT_READ;
 128   return modref_flags;
 129 }
 130
 131 #endif