re PR c/60819 (dse1 removing not-dead insn (aliasing issue?))

2014-04-14  Richard Biener  <rguenther@suse.de>
	Marc Glisse  <marc.glisse@inria.fr>

	PR c/60819
	c-family/
	* c-common.c (convert_vector_to_pointer_for_subscript): Properly
	apply may-alias the scalar pointer type when applicable.

	* gcc.target/i386/vec-may_alias.c: New testcase.

Co-Authored-By: Marc Glisse <marc.glisse@inria.fr>

From-SVN: r209365

gcc/c-family/ChangeLog

+2014-04-14  Richard Biener  <rguenther@suse.de>
+	Marc Glisse  <marc.glisse@inria.fr>
+
+	PR c/60819
+	* c-common.c (convert_vector_to_pointer_for_subscript): Properly
+	apply may-alias the scalar pointer type when applicable.
+
 2014-04-12  Igor Zamyatin  <igor.zamyatin@intel.com>
 
 	PR middle-end/60467

gcc/c-family/c-common.c

@@ -11784,8 +11784,21 @@ convert_vector_to_pointer_for_subscript (location_t loc,
 
       c_common_mark_addressable_vec (*vecp);
       type = build_qualified_type (TREE_TYPE (type), TYPE_QUALS (type));
-      type = build_pointer_type (type);
       type1 = build_pointer_type (TREE_TYPE (*vecp));
+      bool ref_all = TYPE_REF_CAN_ALIAS_ALL (type1);
+      if (!ref_all
+	  && !DECL_P (*vecp))
+	{
+	  /* If the original vector isn't declared may_alias and it
+	     isn't a bare vector look if the subscripting would
+	     alias the vector we subscript, and if not, force ref-all.  */
+	  alias_set_type vecset = get_alias_set (*vecp);
+	  alias_set_type sset = get_alias_set (type);
+	  if (!alias_sets_must_conflict_p (sset, vecset)
+	      && !alias_set_subset_of (sset, vecset))
+	    ref_all = true;
+	}
+      type = build_pointer_type_for_mode (type, ptr_mode, ref_all);
       *vecp = build1 (ADDR_EXPR, type1, *vecp);
       *vecp = convert (type, *vecp);
     }

gcc/testsuite/ChangeLog

+2014-04-14  Richard Biener  <rguenther@suse.de>
+	Marc Glisse  <marc.glisse@inria.fr>
+
+	PR c/60819
+	* gcc.target/i386/vec-may_alias.c: New testcase.
+
 2014-04-14  Rainer Orth  <ro@CeBiTec.Uni-Bielefeld.DE>
 
 	* lib/target-supports.exp

gcc/testsuite/gcc.target/i386/vec-may_alias.c

+/* { dg-do run } */
+/* { dg-options "-O2 -w -Wno-abi" } */
+
+typedef int v2si __attribute__ ((vector_size (8)));
+typedef short v4hi __attribute__ ((vector_size (8)));
+typedef short v4hia __attribute__ ((vector_size (8), may_alias));
+
+__attribute__ ((noinline, noclone))
+int f (v2si A, int N)
+{ return ((v4hia)A)[N]; }
+
+__attribute__ ((noinline, noclone))
+int g (v2si A, int N)
+{ return ((v4hi)A)[N]; }
+
+int main()
+{
+  v2si x = { 0, 0 }, y = { 1, 1 };
+  if (f (x, 0) || f (x, 1) || f (x, 2) || f (x, 3))
+    __builtin_abort ();
+  if (g (y, 0) != 1 || g (y, 1) || g (y, 2) != 1 || g (y, 3))
+    __builtin_abort ();
+  return 0;
+}
+