[PATCH PR70935, Regression 6,7]

[PATCH PR70935, Regression 6,7]

[Yuri Rumyantsev]

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Hi All,

Here is a simple patch which cures the problem with nonlegal
transformation of endless loop. THe fix is simply check that guard
edge destination is not loop latch block.

Bootstrapping and regression testing did not show any new failures.
Is it OK for trunk?

ChangeLog:
2016-05-05  Yuri Rumyantsev  <ysrumyan@gmail.com>

PR debug/70935
* tree-ssa-loop-unswitch.c (find_loop_guard): Reject guard edge with
loop latch destination.

gcc/testsuite/ChangeLog
* gcc.dg/torture/pr70935.c: New test.

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diff --git a/gcc/testsuite/gcc.dg/torture/pr70935.c b/gcc/testsuite/gcc.dg/torture/pr70935.c
new file mode 100755
index 0000000..9ef5a5a
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/torture/pr70935.c
@@ -0,0 +1,39 @@
+/* { dg-do compile } */
+/* { dg-options "-O3 -g" } */
+
+int d0, sj, v0, rp, zi;
+
+void
+zn(void)
+{
+  if (v0 != 0)
+    {
+      int *js, *r3;
+      int pm, gc;
+
+      for (gc = 0; gc < 1; ++gc)
+        {
+          sj = 1;
+          while (sj != 0)
+            ;
+        }
+      r3 = &pm;
+      *js = (long)&gc;
+ka:
+      for (d0 = 0; d0 < 2; ++d0)
+        {
+          d0 = zi;
+          if (zi)
+            for (pm = 2; pm != 0; --pm)
+              ;
+        }
+      while (*r3 != 0)
+        {
+          while (pm)
+            ;
+          ++r3;
+        }
+    }
+  rp = 0;
+  goto ka;
+}

diff --git a/gcc/tree-ssa-loop-unswitch.c b/gcc/tree-ssa-loop-unswitch.c
index dd6fd01..ba1f13c 100644
--- a/gcc/tree-ssa-loop-unswitch.c
+++ b/gcc/tree-ssa-loop-unswitch.c
@@ -532,6 +532,12 @@ find_loop_guard (struct loop *loop)
 		 guard_edge->src->index, guard_edge->dest->index);
       return NULL;
     }
+  if (guard_edge->dest == loop->latch)
+    {
+      if (dump_file && (dump_flags & TDF_DETAILS))
+	fprintf (dump_file, "Guard edge destination is loop latch.\n");
+      return NULL;
+    }
 
   if (dump_file && (dump_flags & TDF_DETAILS))
     fprintf (dump_file,

Re: [PATCH PR70935, Regression 6,7]

[Richard Biener]

On Thu, May 5, 2016 at 5:19 PM, Yuri Rumyantsev <ysrumyan@gmail.com> wrote:
> Hi All,
>
> Here is a simple patch which cures the problem with nonlegal
> transformation of endless loop. THe fix is simply check that guard
> edge destination is not loop latch block.
>
> Bootstrapping and regression testing did not show any new failures.
> Is it OK for trunk?

Ok for trunk and branch.

THanks,
RIchard.

> ChangeLog:
> 2016-05-05  Yuri Rumyantsev  <ysrumyan@gmail.com>
>
> PR debug/70935
> * tree-ssa-loop-unswitch.c (find_loop_guard): Reject guard edge with
> loop latch destination.
>
> gcc/testsuite/ChangeLog
> * gcc.dg/torture/pr70935.c: New test.