re PR tree-optimization/39746 (Fail pr34513.c and pr34513.C at -O1 and above)

2009-04-17  Richard Guenther  <rguenther@suse.de>

	PR tree-optimization/39746
	* tree-ssa-alias.c (ref_maybe_used_by_call_p_1): Remove
	special-casing for builtins and static variable use/def.
	(call_may_clobber_ref_p_1): Likewise.

From-SVN: r146240

gcc/ChangeLog

+2009-04-17  Richard Guenther  <rguenther@suse.de>
+
+	PR tree-optimization/39746
+	* tree-ssa-alias.c (ref_maybe_used_by_call_p_1): Remove
+	special-casing for builtins and static variable use/def.
+	(call_may_clobber_ref_p_1): Likewise.
+
 2009-04-16  Ian Lance Taylor  <iant@google.com>
 
 	* df.h: Include "timevar.h".

gcc/tree-ssa-alias.c

@@ -737,7 +737,7 @@ refs_may_alias_p (tree ref1, tree ref2)
 static bool
 ref_maybe_used_by_call_p_1 (gimple call, tree ref)
 {
-  tree base, fndecl;
+  tree base;
   unsigned i;
   int flags = gimple_call_flags (call);
 
@@ -758,14 +758,8 @@ ref_maybe_used_by_call_p_1 (gimple call, tree ref)
      cannot possibly use it.  */
   if (DECL_P (base)
       && !may_be_aliased (base)
-      /* But local statics can be used through recursion!  */
-      && (!is_global_var (base)
-	  /* But not via builtins.
-	     ???  We just assume that this is true if we are not a
-	     builtin function ourself.  */
-	  || (!DECL_BUILT_IN (cfun->decl)
-	      && (fndecl = gimple_call_fndecl (call))
-	      && DECL_BUILT_IN (fndecl))))
+      /* But local statics can be used through recursion.  */
+      && !is_global_var (base))
     goto process_args;
 
   /* Check if base is a global static variable that is not read
@@ -865,7 +859,7 @@ ref_maybe_used_by_stmt_p (gimple stmt, tree ref)
 static bool
 call_may_clobber_ref_p_1 (gimple call, tree ref)
 {
-  tree fndecl, base;
+  tree base;
 
   /* If the call is pure or const it cannot clobber anything.  */
   if (gimple_call_flags (call)
@@ -884,15 +878,11 @@ call_may_clobber_ref_p_1 (gimple call, tree ref)
      cannot possibly clobber it.  */
   if (DECL_P (base)
       && !may_be_aliased (base)
-      /* But local non-readonly statics can be modified through recursion!  */
+      /* But local non-readonly statics can be modified through recursion
+         or the call may implement a threading barrier which we must
+	 treat as may-def.  */
       && (TREE_READONLY (base)
-	  || !is_global_var (base)
-	  /* But not via builtins.
-	     ???  We just assume that this is true if we are not a
-	     builtin function ourself.  */
-	  || (!DECL_BUILT_IN (cfun->decl)
-	      && (fndecl = gimple_call_fndecl (call))
-	      && DECL_BUILT_IN (fndecl))))
+	  || !is_global_var (base)))
     return false;
 
   /* Check if base is a global static variable that is not written