re PR tree-optimization/78312 (wrong code due to ssa-backprop)

2016-11-14  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/78312
	* gimple-ssa-backprop.c (backprop::prepare_change): Reset
	flow-sensitive info.

	* gcc.dg/torture/pr78312.c: New testcase.

From-SVN: r242380

gcc/ChangeLog

+2016-11-14  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/78312
+	* gimple-ssa-backprop.c (backprop::prepare_change): Reset
+	flow-sensitive info.
+
 2016-11-14  Georg-Johann Lay  <avr@gjlay.de>
 
 	PR target/78093

gcc/gimple-ssa-backprop.c

@@ -728,6 +728,7 @@ backprop::prepare_change (tree var)
 {
   if (MAY_HAVE_DEBUG_STMTS)
     insert_debug_temp_for_var_def (NULL, var);
+  reset_flow_sensitive_info (var);
 }
 
 /* STMT has been changed.  Give the fold machinery a chance to simplify

gcc/testsuite/ChangeLog

+2016-11-14  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/78312
+	* gcc.dg/torture/pr78312.c: New testcase.
+
 2016-11-14  Georg-Johann Lay  <avr@gjlay.de>
 
 	PR target/78093

gcc/testsuite/gcc.dg/torture/pr78312.c

+/* { dg-do run } */
+
+typedef unsigned short u16;
+
+static u16 a;
+
+u16 __attribute__ ((noinline, noclone))
+foo (int p1)
+{
+  a = -(p1 > 0);
+  a *= 0 != a;
+  a *= (unsigned)a;
+  return a;
+}
+
+int
+main ()
+{
+  u16 x = foo (1);
+  if (x != 1)
+    __builtin_abort();
+  return 0;
+}