[PATCH] Fix PR82603

[Richard Biener]

Bootstrapped on x86_64-unknown-linux-gnu, testing in progress.

Richard.

2017-10-20  Richard Biener  <rguent...@suse.de>

        PR tree-optimization/82473
        * tree-if-conv.c (predicate_mem_writes): Make sure to only
        remove false predicated stores.

        * gcc.dg/torture/pr82603.c: New testcase.

Index: gcc/tree-if-conv.c
===================================================================
--- gcc/tree-if-conv.c  (revision 253926)
+++ gcc/tree-if-conv.c  (working copy)
@@ -2214,7 +2214,8 @@ predicate_mem_writes (loop_p loop)
        {
          if (!gimple_assign_single_p (stmt = gsi_stmt (gsi)))
            ;
-         else if (is_false_predicate (cond))
+         else if (is_false_predicate (cond)
+                  && gimple_vdef (stmt))
            {
              unlink_stmt_vdef (stmt);
              gsi_remove (&gsi, true);
Index: gcc/testsuite/gcc.dg/torture/pr82603.c
===================================================================
--- gcc/testsuite/gcc.dg/torture/pr82603.c      (nonexistent)
+++ gcc/testsuite/gcc.dg/torture/pr82603.c      (working copy)
@@ -0,0 +1,24 @@
+/* { dg-do compile } */
+/* { dg-additional-options "-ftree-loop-vectorize" } */
+
+int
+mr (unsigned int lf, int ms)
+{
+  unsigned int sw = 0;
+  char *cu = (char *)&ms;
+
+  while (ms < 1)
+    {
+      if (lf == 0)
+       ms = 0;
+      else
+       ms = 0;
+      ms += ((lf > 0) && ((lf > sw) ? 1 : ++*cu));
+    }
+
+  if (lf != 0)
+    cu = (char *)&sw;
+  *cu = lf;
+
+  return ms;
+}