[gcc r10-9828] tree-optimization/100566 - fix another predication issue in VN

[Richard Biener <rguenth@gcc.gnu.org>]

https://gcc.gnu.org/g:9ddc622a15d05510e7ab17ca1584d7fdb828d64e

commit r10-9828-g9ddc622a15d05510e7ab17ca1584d7fdb828d64e
Author: Richard Biener <rguenther@suse.de>
Date:   Wed May 12 15:39:52 2021 +0200

    tree-optimization/100566 - fix another predication issue in VN
    
    This amends the fix for PR100053 where I failed to amend all edge
    tests in dominated_by_p_w_unex.
    
    2021-05-12  Richard Biener  <rguenther@suse.de>
    
            PR tree-optimization/100566
            * tree-ssa-sccvn.c (dominated_by_p_w_unex): Properly handle
            allow_back for all edge queries.
    
            * gcc.dg/torture/pr100566.c: New testcase.
    
    (cherry picked from commit 097fde5e7514e909f2e8472be2e008d0cab2260d)

Diff:
---
 gcc/testsuite/gcc.dg/torture/pr100566.c | 36 +++++++++++++++++++++++++++++++++
 gcc/tree-ssa-sccvn.c                    |  6 ++++--
 2 files changed, 40 insertions(+), 2 deletions(-)

diff --git a/gcc/testsuite/gcc.dg/torture/pr100566.c b/gcc/testsuite/gcc.dg/torture/pr100566.c
new file mode 100644
index 00000000000..ed856913639
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/torture/pr100566.c
@@ -0,0 +1,36 @@
+/* { dg-do run } */
+
+volatile int s, c;
+
+__attribute__((noipa)) void
+foo (void)
+{
+  if (c++ > 1)
+    __builtin_abort ();
+}
+
+__attribute__((noipa)) int
+bar (void)
+{
+  int i = 0, j = s;
+  if (j == 0)
+    goto lab;
+  for (i = 0; i < j; i++)
+    {
+    lab:
+      foo ();
+      if (!j)
+        goto lab;
+    }
+  return 0;
+}
+
+int
+main ()
+{
+  s = 1;
+  bar ();
+  if (c != 1)
+    __builtin_abort ();
+  return 0;
+}
diff --git a/gcc/tree-ssa-sccvn.c b/gcc/tree-ssa-sccvn.c
index 9b0d730d11d..f6b1bd174c3 100644
--- a/gcc/tree-ssa-sccvn.c
+++ b/gcc/tree-ssa-sccvn.c
@@ -4448,7 +4448,8 @@ dominated_by_p_w_unex (basic_block bb1, basic_block bb2, bool allow_back)
   /* Iterate to the single executable bb2 successor.  */
   edge succe = NULL;
   FOR_EACH_EDGE (e, ei, bb2->succs)
-    if (e->flags & EDGE_EXECUTABLE)
+    if ((e->flags & EDGE_EXECUTABLE)
+	|| (!allow_back && (e->flags & EDGE_DFS_BACK)))
       {
 	if (succe)
 	  {
@@ -4466,7 +4467,8 @@ dominated_by_p_w_unex (basic_block bb1, basic_block bb2, bool allow_back)
 	{
 	  FOR_EACH_EDGE (e, ei, succe->dest->preds)
 	    if (e != succe
-		&& (e->flags & EDGE_EXECUTABLE))
+		&& ((e->flags & EDGE_EXECUTABLE)
+		    || (!allow_back && (e->flags & EDGE_DFS_BACK))))
 	      {
 		succe = NULL;
 		break;