re PR tree-optimization/91180 (wrong code at -O and above with __builtin_memset())

2019-07-17  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/91180
	* tree-ssa-sccvn.c (vn_reference_lookup_3): Fix offset
	computation for memset partial defs.

	* gcc.dg/torture/pr91180.c: New testcase.

From-SVN: r273548

gcc/ChangeLog

+2019-07-17  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/91180
+	* tree-ssa-sccvn.c (vn_reference_lookup_3): Fix offset
+	computation for memset partial defs.
+
 2019-07-17  Jakub Jelinek  <jakub@redhat.com>
 
 	* gimple.h (enum gf_mask): Remove GF_OMP_FOR_SIMD, change

gcc/testsuite/ChangeLog

+2019-07-17  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/91180
+	* gcc.dg/torture/pr91180.c: New testcase.
+
 2019-07-17  Jakub Jelinek  <jakub@redhat.com>
 
 	PR tree-optimization/91157

gcc/testsuite/gcc.dg/torture/pr91180.c

+/* { dg-do run } */
+
+int
+main ()
+{
+#if __SIZEOF_INT__ == 4
+  unsigned x = 0xffffffff;
+  __builtin_memset (1 + (char *) &x, 0, 2);
+  if (x != 0xff0000ff)
+    __builtin_abort ();
+#endif
+  return 0;
+}

gcc/tree-ssa-sccvn.c

@@ -2486,7 +2486,7 @@ vn_reference_lookup_3 (ao_ref *ref, tree vuse, void *data_,
 	{
 	  pd_data pd;
 	  pd.rhs = build_constructor (NULL_TREE, NULL);
-	  pd.offset = offset2i - offseti;
+	  pd.offset = (offset2i - offseti) / BITS_PER_UNIT;
 	  pd.size = leni;
 	  return data->push_partial_def (pd, vuse, maxsizei);
 	}