re PR middle-end/89008 (O2 and O1 results differ for simple test)

2019-01-23  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/89008
	* tree-ssa-reassoc.c (eliminate_using_constants): For * 0 do
	not leave another stray operand.

	* gcc.dg/torture/pr89008.c: New testcase.

From-SVN: r268186

gcc/ChangeLog

+2019-01-23  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/89008
+	* tree-ssa-reassoc.c (eliminate_using_constants): For * 0 do
+	not leave another stray operand.
+
 2019-01-23  Jakub Jelinek  <jakub@redhat.com>
 
 	* BASE-VER: Bump to 9.0.1.

gcc/testsuite/ChangeLog

+2019-01-23  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/89008
+	* gcc.dg/torture/pr89008.c: New testcase.
+
 2019-01-23  Eric Botcazou  <ebotcazou@adacore.com>
 
 	* gnat.dg/specs/opt4.ads: New test.

gcc/testsuite/gcc.dg/torture/pr89008.c

+/* { dg-do run } */
+/* { dg-require-effective-target int32plus } */
+
+unsigned long a, c;
+unsigned b;
+int d, e;
+long f()
+{
+  unsigned long g = 0;
+  for (d = 0; d < 5; d += 2)
+    for (e = 0; e < 5; e += 3)
+      {
+	c = 4 + b;
+	g = -b - b;
+	b = 5 * (b << 24);
+      }
+  a = g;
+  return 0;
+}
+
+int main()
+{
+  f();
+  if (a)
+    __builtin_abort();
+  return 0;
+}

gcc/tree-ssa-reassoc.c

@@ -1015,7 +1015,7 @@ eliminate_using_constants (enum tree_code opcode,
 		    fprintf (dump_file, "Found * 0, removing all other ops\n");
 
 		  reassociate_stats.ops_eliminated += ops->length () - 1;
-		  ops->truncate (1);
+		  ops->truncate (0);
 		  ops->quick_push (oelast);
 		  return;
 		}