ipa-modref bits for unsequenced and reproducible

C attributes reproducible and unsequenced implies that calling function twice
leads to same effect if parameters are otherwise unchanged (function call
itself does not count).  This is bit bit stronger that modref's notion of
nondeterminism that says that same inputs will yield same outputs (function
call itself does count).

This patch makes reproducible/unsequenced imply determinism and cleans up
determinism handling.  By itself it is not useful, since we can not make use of it
unless we know what are the inputs/outputs of the function which I plan to handle
by the "fn spec" attribute.

gcc/ChangeLog:

	* ipa-modref.cc (modref_summary::useful_p): const/pure implies
	determinism.
	(modref_summary_lto::useful_p): Likewise.
	(ignore_nondeterminism_p): Add CALLEE_FNTYPE parameter; check for
	reproducible/unsequenced
	(modref_access_analysis::record_access_p): Use ignore_nondeterminism_p
	when handling volatile accesses.
	(modref_access_analysis::get_access_for_fnspec): Update.
	(modref_access_analysis::process_fnspec): Cleanup handling of NOVOPS.
	(modref_access_analysis::analyze_call): Use ignore_nondeterminism_p
	when handling asm statements.
	(modref_access_analysis::analyze_stmt): Update.
	(propagate_unknown_call): Update.
	(modref_propagate_in_scc): Update.
	(ipa_merge_modref_summary_after_inlining): Update.

1 files changed, 53 insertions, 37 deletions

diff --git a/gcc/ipa-modref.cc b/gcc/ipa-modref.cc
index 12ac0e7..08a7740 100644
--- a/gcc/ipa-modref.cc
+++ b/gcc/ipa-modref.cc
@@ -336,15 +336,13 @@ modref_summary::useful_p (int ecf_flags, bool check_flags)
       && remove_useless_eaf_flags (static_chain_flags, ecf_flags, false))
     return true;
   if (ecf_flags & ECF_CONST)
-    return ((!side_effects || !nondeterministic)
-	    && (ecf_flags & ECF_LOOPING_CONST_OR_PURE));
+    return (!side_effects && (ecf_flags & ECF_LOOPING_CONST_OR_PURE));
   if (loads && !loads->every_base)
     return true;
   else
     kills.release ();
   if (ecf_flags & ECF_PURE)
-    return ((!side_effects || !nondeterministic)
-	    && (ecf_flags & ECF_LOOPING_CONST_OR_PURE));
+    return (!side_effects && (ecf_flags & ECF_LOOPING_CONST_OR_PURE));
   return stores && !stores->every_base;
 }
 
@@ -409,15 +407,13 @@ modref_summary_lto::useful_p (int ecf_flags, bool check_flags)
       && remove_useless_eaf_flags (static_chain_flags, ecf_flags, false))
     return true;
   if (ecf_flags & (ECF_CONST | ECF_NOVOPS))
-    return ((!side_effects || !nondeterministic)
-	    && (ecf_flags & ECF_LOOPING_CONST_OR_PURE));
+    return (!side_effects && (ecf_flags & ECF_LOOPING_CONST_OR_PURE));
   if (loads && !loads->every_base)
     return true;
   else
     kills.release ();
   if (ecf_flags & ECF_PURE)
-    return ((!side_effects || !nondeterministic)
-	    && (ecf_flags & ECF_LOOPING_CONST_OR_PURE));
+    return (!side_effects && (ecf_flags & ECF_LOOPING_CONST_OR_PURE));
   return stores && !stores->every_base;
 }
 
@@ -794,13 +790,25 @@ namespace {
 /* Return true if ECF flags says that nondeterminism can be ignored.  */
 
 static bool
-ignore_nondeterminism_p (tree caller, int flags)
+ignore_nondeterminism_p (tree caller, int flags, tree callee_fntype)
 {
-  if (flags & (ECF_CONST | ECF_PURE))
+  int caller_flags = flags_from_decl_or_type (caller);
+  if ((flags | caller_flags) & (ECF_CONST | ECF_PURE))
     return true;
   if ((flags & (ECF_NORETURN | ECF_NOTHROW)) == (ECF_NORETURN | ECF_NOTHROW)
       || (!opt_for_fn (caller, flag_exceptions) && (flags & ECF_NORETURN)))
     return true;
+  /* C language defines unsequenced and reproducible functions
+     to be deterministic.  */
+  if (lookup_attribute ("unsequenced", TYPE_ATTRIBUTES (TREE_TYPE (caller)))
+      || lookup_attribute ("reproducible",
+			   TYPE_ATTRIBUTES (TREE_TYPE (caller))))
+    return true;
+  if (callee_fntype
+      && (lookup_attribute ("unsequenced", TYPE_ATTRIBUTES (callee_fntype))
+	  || lookup_attribute ("reproducible",
+			       TYPE_ATTRIBUTES (callee_fntype))))
+    return true;
   return false;
 }
 
@@ -1151,7 +1159,8 @@ modref_access_analysis::record_access_lto (modref_records_lto *tt, ao_ref *ref,
 bool
 modref_access_analysis::record_access_p (tree expr)
 {
-  if (TREE_THIS_VOLATILE (expr))
+  if (TREE_THIS_VOLATILE (expr)
+      && !ignore_nondeterminism_p (current_function_decl, 0, NULL))
     {
       if (dump_file)
 	fprintf (dump_file, " (volatile; marking nondeterministic) ");
@@ -1288,7 +1297,8 @@ modref_access_analysis::merge_call_side_effects
 	  changed = true;
 	}
       if (!m_summary->nondeterministic && callee_summary->nondeterministic
-	  && !ignore_nondeterminism_p (current_function_decl, flags))
+	  && !ignore_nondeterminism_p (current_function_decl, flags,
+				       gimple_call_fntype (call)))
 	{
 	  if (dump_file)
 	    fprintf (dump_file, " - merging nondeterministic.\n");
@@ -1455,6 +1465,7 @@ modref_access_analysis::get_access_for_fnspec (gcall *call, attr_fnspec &fnspec,
     }
   return a;
 }
+
 /* Apply side effects of call STMT to CUR_SUMMARY using FNSPEC.
    If IGNORE_STORES is true ignore them.
    Return false if no useful summary can be produced.   */
@@ -1472,7 +1483,8 @@ modref_access_analysis::process_fnspec (gcall *call)
 	  && stmt_could_throw_p (cfun, call)))
     {
       set_side_effects ();
-      if (!ignore_nondeterminism_p (current_function_decl, flags))
+      if (!ignore_nondeterminism_p (current_function_decl, flags,
+				    gimple_call_fntype (call)))
 	set_nondeterministic ();
     }
 
@@ -1625,13 +1637,7 @@ modref_access_analysis::analyze_call (gcall *stmt)
       if (dump_file)
 	fprintf (dump_file, gimple_call_internal_p (stmt)
 		 ? " - Internal call" : " - Indirect call.\n");
-      if (flags & ECF_NOVOPS)
-        {
-	  set_side_effects ();
-	  set_nondeterministic ();
-        }
-      else
-	process_fnspec (stmt);
+      process_fnspec (stmt);
       return;
     }
   /* We only need to handle internal calls in IPA mode.  */
@@ -1800,7 +1806,8 @@ modref_access_analysis::analyze_stmt (gimple *stmt, bool always_executed)
   switch (gimple_code (stmt))
    {
    case GIMPLE_ASM:
-      if (gimple_asm_volatile_p (as_a <gasm *> (stmt)))
+      if (gimple_asm_volatile_p (as_a <gasm *> (stmt))
+	  && !ignore_nondeterminism_p (current_function_decl, 0, NULL))
 	set_nondeterministic ();
       if (cfun->can_throw_non_call_exceptions
 	  && stmt_could_throw_p (cfun, stmt))
@@ -4592,17 +4599,20 @@ propagate_unknown_call (cgraph_node *node,
 	  cur_summary_lto->side_effects = true;
 	  changed = true;
 	}
-      if (cur_summary && !cur_summary->nondeterministic
-	  && !ignore_nondeterminism_p (node->decl, ecf_flags))
-	{
-	  cur_summary->nondeterministic = true;
-	  changed = true;
-	}
-      if (cur_summary_lto && !cur_summary_lto->nondeterministic
-	  && !ignore_nondeterminism_p (node->decl, ecf_flags))
+      if (!ignore_nondeterminism_p (node->decl, ecf_flags,
+				    e->callee ? TREE_TYPE (e->callee->decl)
+					      : NULL_TREE))
 	{
-	  cur_summary_lto->nondeterministic = true;
-	  changed = true;
+	  if (cur_summary && !cur_summary->nondeterministic)
+	    {
+	      cur_summary->nondeterministic = true;
+	      changed = true;
+	    }
+	  if (cur_summary_lto && !cur_summary_lto->nondeterministic)
+	    {
+	      cur_summary_lto->nondeterministic = true;
+	      changed = true;
+	    }
 	}
     }
   if (ecf_flags & (ECF_CONST | ECF_NOVOPS))
@@ -4869,14 +4879,18 @@ modref_propagate_in_scc (cgraph_node *component_node)
 		}
 	      if (callee_summary && !cur_summary->nondeterministic
 		  && callee_summary->nondeterministic
-		  && !ignore_nondeterminism_p (cur->decl, flags))
+		  && !ignore_nondeterminism_p
+			  (cur->decl, flags,
+			   TREE_TYPE (callee_edge->callee->decl)))
 		{
 		  cur_summary->nondeterministic = true;
 		  changed = true;
 		}
 	      if (callee_summary_lto && !cur_summary_lto->nondeterministic
 		  && callee_summary_lto->nondeterministic
-		  && !ignore_nondeterminism_p (cur->decl, flags))
+		  && !ignore_nondeterminism_p
+			  (cur->decl, flags,
+			   TREE_TYPE (callee_edge->callee->decl)))
 		{
 		  cur_summary_lto->nondeterministic = true;
 		  changed = true;
@@ -5358,20 +5372,22 @@ ipa_merge_modref_summary_after_inlining (cgraph_edge *edge)
   if (!(flags & (ECF_CONST | ECF_PURE))
       || (flags & ECF_LOOPING_CONST_OR_PURE))
     {
+      bool set_nondeterministic
+	      = !ignore_nondeterminism_p
+		      (edge->caller->decl, flags,
+		       TREE_TYPE (edge->callee->decl));
       if (to_info)
 	{
 	  if (!callee_info || callee_info->side_effects)
 	    to_info->side_effects = true;
-	  if ((!callee_info || callee_info->nondeterministic)
-	      && !ignore_nondeterminism_p (edge->caller->decl, flags))
+	  if (set_nondeterministic)
 	    to_info->nondeterministic = true;
 	}
       if (to_info_lto)
 	{
 	  if (!callee_info_lto || callee_info_lto->side_effects)
 	    to_info_lto->side_effects = true;
-	  if ((!callee_info_lto || callee_info_lto->nondeterministic)
-	      && !ignore_nondeterminism_p (edge->caller->decl, flags))
+	  if (set_nondeterministic)
 	    to_info_lto->nondeterministic = true;
 	}
      }