2011-01-14 Richard Guenther <rguenther@suse.de>

	PR tree-optimization/47179
	* target.def (ref_may_alias_errno): New target hook.
	* targhooks.h (default_ref_may_alias_errno): Declare.
	* targhooks.c: Include tree-ssa-alias.h and tree-flow.h.
	(default_ref_may_alias_errno): New function.
	* target.h (struct ao_ref_s): Declare.
	* tree-ssa-alias.c: Include target.h.
	(call_may_clobber_ref_p_1): Use the ref_may_alias_errno target hook.
	* Makefile.in (tree-ssa-alias.o): Adjust dependencies.
	(targhooks.o): Likewise.
	* doc/tm.texi.in (TARGET_REF_MAY_ALIAS_ERRNO): Document.
	* doc/tm.texi (TARGET_REF_MAY_ALIAS_ERRNO): Copy documentation.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@168788 138bc75d-0d04-0410-961f-82ee72b054a4

1 files changed, 29 insertions, 0 deletions

diff --git a/gcc/targhooks.c b/gcc/targhooks.c
index 30a58911d2e..225831b9515 100644
--- a/gcc/targhooks.c
+++ b/gcc/targhooks.c
@@ -69,6 +69,8 @@ along with GCC; see the file COPYING3.  If not see
 #include "recog.h"
 #include "intl.h"
 #include "opts.h"
+#include "tree-flow.h"
+#include "tree-ssa-alias.h"
 
 
 bool
@@ -1035,6 +1037,33 @@ default_valid_pointer_mode (enum machine_mode mode)
   return (mode == ptr_mode || mode == Pmode);
 }
 
+/* Determine whether the memory reference specified by REF may alias
+   the C libraries errno location.  */
+bool
+default_ref_may_alias_errno (ao_ref *ref)
+{
+  tree base = ao_ref_base (ref);
+  /* The default implementation assumes the errno location is
+     a declaration of type int or is always accessed via a
+     pointer to int.  We assume that accesses to errno are
+     not deliberately obfuscated (even in conforming ways).  */
+  if (TYPE_UNSIGNED (TREE_TYPE (base))
+      || TYPE_MODE (TREE_TYPE (base)) != TYPE_MODE (integer_type_node))
+    return false;
+  /* The default implementation assumes an errno location
+     declaration is never defined in the current compilation unit.  */
+  if (DECL_P (base)
+      && !TREE_STATIC (base))
+    return true;
+  else if (TREE_CODE (base) == MEM_REF
+	   && TREE_CODE (TREE_OPERAND (base, 0)) == SSA_NAME)
+    {
+      struct ptr_info_def *pi = SSA_NAME_PTR_INFO (TREE_OPERAND (base, 0));
+      return !pi || pi->pt.anything || pi->pt.nonlocal;
+    }
+  return false;
+}
+
 /* Return the mode for a pointer to a given ADDRSPACE, defaulting to ptr_mode
    for the generic address space only.  */