[PATCH] Fix PR87328

[Richard Biener]

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

Richard.

2018-09-17  Richard Biener  <rguent...@suse.de>

        PR tree-optimization/87328
        * tree-ssa-sccvn.c (process_bb): Remove assertion about not
        visiting unexecutable backedges when not iterating.
        (do_rpo_vn): Mark all edges not executable even when not
        iterating.

        * gcc.dg/torture/pr87328.c: New testcase.

Index: gcc/tree-ssa-sccvn.c
===================================================================
--- gcc/tree-ssa-sccvn.c        (revision 264364)
+++ gcc/tree-ssa-sccvn.c        (working copy)
@@ -5978,7 +5978,6 @@ process_bb (rpo_elim &avail, basic_block
                fprintf (dump_file,
                         "marking outgoing edge %d -> %d executable\n",
                         e->src->index, e->dest->index);
-             gcc_checking_assert (iterate || !(e->flags & EDGE_DFS_BACK));
              e->flags |= EDGE_EXECUTABLE;
              e->dest->flags |= BB_EXECUTABLE;
            }
@@ -6125,7 +6124,6 @@ process_bb (rpo_elim &avail, basic_block
                         "marking known outgoing %sedge %d -> %d executable\n",
                         e->flags & EDGE_DFS_BACK ? "back-" : "",
                         e->src->index, e->dest->index);
-             gcc_checking_assert (iterate || !(e->flags & EDGE_DFS_BACK));
              e->flags |= EDGE_EXECUTABLE;
              e->dest->flags |= BB_EXECUTABLE;
            }
@@ -6148,7 +6146,6 @@ process_bb (rpo_elim &avail, basic_block
                    fprintf (dump_file,
                             "marking outgoing edge %d -> %d executable\n",
                             e->src->index, e->dest->index);
-                 gcc_checking_assert (iterate || !(e->flags & EDGE_DFS_BACK));
                  e->flags |= EDGE_EXECUTABLE;
                  e->dest->flags |= BB_EXECUTABLE;
                }
@@ -6390,10 +6387,7 @@ do_rpo_vn (function *fn, edge entry, bit
        {
          if (e->flags & EDGE_DFS_BACK)
            has_backedges = true;
-         if (! iterate && (e->flags & EDGE_DFS_BACK))
-           e->flags |= EDGE_EXECUTABLE;
-         else
-           e->flags &= ~EDGE_EXECUTABLE;
+         e->flags &= ~EDGE_EXECUTABLE;
          if (e == entry)
            continue;
          if (bb_to_rpo[e->src->index] > i)
Index: gcc/testsuite/gcc.dg/torture/pr87328.c
===================================================================
--- gcc/testsuite/gcc.dg/torture/pr87328.c      (nonexistent)
+++ gcc/testsuite/gcc.dg/torture/pr87328.c      (working copy)
@@ -0,0 +1,25 @@
+/* { dg-do compile } */
+/* { dg-additional-options "-fno-tree-ccp -fno-tree-forwprop" } */
+
+void
+tp (void)
+{
+  int qt;
+
+  qt = 0;
+  if (qt != 0)
+    {
+      if (0)
+       {
+h5:
+         qt = 0;
+         while (qt < 1)
+           {
+           }
+       }
+
+      ++qt;
+    }
+
+  goto h5;
+}