re PR tree-optimization/85257 (wrong code with -O -fno-tree-ccp and reading zeroed vector member)

	PR tree-optimization/85257
	* fold-const.c (native_encode_vector): If not all elts could fit
	and off is -1, return 0 rather than offset.
	* tree-ssa-sccvn.c (vn_reference_lookup_3): Pass
	(offseti - offset2) / BITS_PER_UNIT as 4th argument to
	native_encode_expr.  Verify len * BITS_PER_UNIT >= maxsizei.  Don't
	adjust buffer in native_interpret_expr call.

	* gcc.dg/pr85257.c: New test.

From-SVN: r259206

gcc/ChangeLog

+2018-04-07  Jakub Jelinek  <jakub@redhat.com>
+
+	PR tree-optimization/85257
+	* fold-const.c (native_encode_vector): If not all elts could fit
+	and off is -1, return 0 rather than offset.
+	* tree-ssa-sccvn.c (vn_reference_lookup_3): Pass
+	(offseti - offset2) / BITS_PER_UNIT as 4th argument to
+	native_encode_expr.  Verify len * BITS_PER_UNIT >= maxsizei.  Don't
+	adjust buffer in native_interpret_expr call.
+
 2018-04-07  Monk Chiang  <sh.chiang04@gmail.com>
 
 	* config/nds32/constants.md (unspec_volatile_element): Add cache

gcc/fold-const.c

@@ -7307,7 +7307,7 @@ native_encode_vector (const_tree expr, unsigned char *ptr, int len, int off)
 	return 0;
       offset += res;
       if (offset >= len)
-	return offset;
+	return (off == -1 && i < count - 1) ? 0 : offset;
       if (off != -1)
 	off = 0;
     }

gcc/testsuite/ChangeLog

+2018-04-07  Jakub Jelinek  <jakub@redhat.com>
+
+	PR tree-optimization/85257
+	* gcc.dg/pr85257.c: New test.
+
 2018-04-06  Eric Botcazou  <ebotcazou@adacore.com>
 
 	* g++.dg/opt/pr85196.C: New test.

gcc/testsuite/gcc.dg/pr85257.c

+/* PR tree-optimization/85257 */
+/* { dg-do run { target int128 } } */
+/* { dg-options "-O2 -fno-tree-ccp" } */
+
+typedef __int128 V __attribute__ ((__vector_size__ (16 * sizeof (__int128))));
+
+__int128 __attribute__ ((noipa))
+foo (void)
+{
+  V v = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16 };
+  return v[5];
+}
+
+int
+main ()
+{
+  if (foo () != 6)
+    __builtin_abort ();
+  return 0;
+}

gcc/tree-ssa-sccvn.c

@@ -2038,8 +2038,9 @@ vn_reference_lookup_3 (ao_ref *ref, tree vuse, void *vr_,
 	  if (TREE_CODE (rhs) == SSA_NAME)
 	    rhs = SSA_VAL (rhs);
 	  len = native_encode_expr (gimple_assign_rhs1 (def_stmt),
-				    buffer, sizeof (buffer));
-	  if (len > 0)
+				    buffer, sizeof (buffer),
+				    (offseti - offset2) / BITS_PER_UNIT);
+	  if (len > 0 && len * BITS_PER_UNIT >= maxsizei)
 	    {
 	      tree type = vr->type;
 	      /* Make sure to interpret in a type that has a range
@@ -2048,10 +2049,7 @@ vn_reference_lookup_3 (ao_ref *ref, tree vuse, void *vr_,
 		  && maxsizei != TYPE_PRECISION (vr->type))
 		type = build_nonstandard_integer_type (maxsizei,
 						       TYPE_UNSIGNED (type));
-	      tree val = native_interpret_expr (type,
-						buffer
-						+ ((offseti - offset2)
-						   / BITS_PER_UNIT),
+	      tree val = native_interpret_expr (type, buffer,
 						maxsizei / BITS_PER_UNIT);
 	      /* If we chop off bits because the types precision doesn't
 		 match the memory access size this is ok when optimizing