tree-ssa-alias.c (ref_maybe_used_by_call_p_1): Non-aliased decls are only used if...

2009-04-07  Richard Guenther  <rguenther@suse.de>

	* tree-ssa-alias.c (ref_maybe_used_by_call_p_1): Non-aliased
	decls are only used if passes as parameters or if they are
	local statics and the call is not to a builtin.
	(call_may_clobber_ref_p_1): Likewise.

From-SVN: r145676

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index c01b7d96f07ce9ab4fb8350cbbe651b9e4957568..13c4eb2ffb2fc851976a037a17cc284ffb033024 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,10 @@
+2009-04-07  Richard Guenther  <rguenther@suse.de>
+
+       * tree-ssa-alias.c (ref_maybe_used_by_call_p_1): Non-aliased
+       decls are only used if passes as parameters or if they are
+       local statics and the call is not to a builtin.
+       (call_may_clobber_ref_p_1): Likewise.
+
 2009-04-07  Paolo Bonzini  <bonzini@gnu.org>
 
        * expr.c (do_store_flag): Remove last argument.  Simplify code

diff --git a/gcc/tree-ssa-alias.c b/gcc/tree-ssa-alias.c
index a85858e17af9d0928734d50013a5f2baf17be0bf..f97502a606aead61fbf783cc250fb187f6f3fdd6 100644 (file)
--- a/gcc/tree-ssa-alias.c
+++ b/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;
+  tree base, fndecl;
   unsigned i;
   int flags = gimple_call_flags (call);
 
@@ -754,6 +754,20 @@ ref_maybe_used_by_call_p_1 (gimple call, tree ref)
       || !DECL_P (base))
     return true;
 
+  /* If the reference is based on a decl that is not aliased the call
+     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))))
+    goto process_args;
+
   /* Check if base is a global static variable that is not read
      by the function.  */
   if (TREE_CODE (base) == VAR_DECL
@@ -851,7 +865,7 @@ ref_maybe_used_by_stmt_p (gimple stmt, tree ref)
 static bool
 call_may_clobber_ref_p_1 (gimple call, tree ref)
 {
-  tree base;
+  tree fndecl, base;
 
   /* If the call is pure or const it cannot clobber anything.  */
   if (gimple_call_flags (call)
@@ -866,6 +880,21 @@ call_may_clobber_ref_p_1 (gimple call, tree ref)
       || CONSTANT_CLASS_P (base))
     return false;
 
+  /* If the reference is based on a decl that is not aliased the call
+     cannot possibly clobber it.  */
+  if (DECL_P (base)
+      && !may_be_aliased (base)
+      /* But local non-readonly statics can be modified through recursion!  */
+      && (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))))
+    return false;
+
   /* Check if base is a global static variable that is not written
      by the function.  */
   if (TREE_CODE (base) == VAR_DECL