[PATCH] Fix PR87776

[Richard Biener]

The following fixes a thinko in the rpo-vn-max-loop-depth param handling.

Bootstrapped and tested on x86_64-unknown-linux-gnu.

Richard.

>From 172251b9fdd1ace4c18fb9308be3f4f3ed868241 Mon Sep 17 00:00:00 2001
From: Richard Guenther <rguent...@suse.de>
Date: Wed, 31 Oct 2018 13:33:21 +0100
Subject: [PATCH] fix-pr87776

        PR tree-optimization/87776
        * tree-ssa-sccvn.c (do_rpo_vn): Do not mark backedges
        executable when iterating but running into rpo-vn-max-loop-depth
        and not eliding the iteration.

        * gcc.dg/torture/pr87776.c: New testcase.

diff --git a/gcc/testsuite/gcc.dg/torture/pr87776.c 
b/gcc/testsuite/gcc.dg/torture/pr87776.c
new file mode 100644
index 00000000000..1f150702dcf
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/torture/pr87776.c
@@ -0,0 +1,40 @@
+/* { dg-do compile } */
+/* { dg-additional-options "--param rpo-vn-max-loop-depth=2" } */
+
+int wp;
+
+void
+ff (void)
+{
+  int *s3 = &wp;
+
+  for (wp = 0; wp < 1; ++wp)
+    {
+      if (wp != 0)
+       {
+o8:
+         ;
+       }
+      else
+       {
+b7:
+         while (wp < 1)
+           {
+           }
+       }
+
+      for (*s3 = 0; *s3 < 1; ++*s3)
+       {
+         for (wp = 0; wp < 1; ++wp)
+           for (wp = 0; wp < 1; ++wp)
+             {
+             }
+
+         for (wp = 0; wp < 1; ++wp)
+           goto o8;
+
+         for (wp = 0; wp < 1; ++wp)
+           goto b7;
+       }
+    }
+}
diff --git a/gcc/tree-ssa-sccvn.c b/gcc/tree-ssa-sccvn.c
index 38330754769..43641916d52 100644
--- a/gcc/tree-ssa-sccvn.c
+++ b/gcc/tree-ssa-sccvn.c
@@ -6449,7 +6449,6 @@ do_rpo_vn (function *fn, edge entry, bitmap exit_bbs,
              FOR_EACH_EDGE (e, ei, header->preds)
                if (e->flags & EDGE_DFS_BACK)
                  {
-                   e->flags |= EDGE_EXECUTABLE;
                    /* There can be a non-latch backedge into the header
                       which is part of an outer irreducible region.  We
                       cannot avoid iterating this block then.  */
@@ -6462,6 +6461,8 @@ do_rpo_vn (function *fn, edge entry, bitmap exit_bbs,
                                   e->src->index, e->dest->index, loop->num);
                        non_latch_backedge = true;
                      }
+                   else
+                     e->flags |= EDGE_EXECUTABLE;
                  }
              rpo_state[bb_to_rpo[header->index]].iterate = non_latch_backedge;
            }