From: Richard Biener <rguenther@suse.de>
Date: Tue, 22 Jun 2021 08:14:02 +0000 (+0200)
Subject: tree-optimization/101151 - fix irreducible region check for sinking
X-Git-Tag: basepoints/gcc-13~6595
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=a2ef8395fa970498985764514044e5fd00f7d5c0;p=thirdparty%2Fgcc.git

tree-optimization/101151 - fix irreducible region check for sinking

The check whether two blocks are in the same irreducible region
and thus post-dominance checks being unreliable was incomplete
since an irreducible region can contain reducible sub-regions but
if one block is in the irreducible part and one not the check
still doesn't work as expected.

2021-06-22  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/101151
	* tree-ssa-sink.c (statement_sink_location): Expand irreducible
	region check.

	* gcc.dg/torture/pr101151.c: New testcase.
---

diff --git a/gcc/testsuite/gcc.dg/torture/pr101151.c b/gcc/testsuite/gcc.dg/torture/pr101151.c
new file mode 100644
index 000000000000..15c9a7b7f57f
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/torture/pr101151.c
@@ -0,0 +1,19 @@
+/* { dg-do compile } */
+
+int a, *b = &a, c, d;
+int main() {
+  *b;
+  if (a) {
+  L1:
+    a = 0;
+  L2:
+    if (d) {
+      while (b)
+        ;
+      goto L1;
+    }
+  }
+  if (c)
+    goto L2;
+  return 0;
+}
diff --git a/gcc/tree-ssa-sink.c b/gcc/tree-ssa-sink.c
index d252cbb5c518..92f444ec1c81 100644
--- a/gcc/tree-ssa-sink.c
+++ b/gcc/tree-ssa-sink.c
@@ -398,7 +398,14 @@ statement_sink_location (gimple *stmt, basic_block frombb,
 		      && dominated_by_p (CDI_POST_DOMINATORS, commondom, bb)
 		      /* If the blocks are possibly within the same irreducible
 			 cycle the above check breaks down.  */
-		      && !(bb->flags & commondom->flags & BB_IRREDUCIBLE_LOOP))
+		      && !((bb->flags & commondom->flags & BB_IRREDUCIBLE_LOOP)
+			   && bb->loop_father == commondom->loop_father)
+		      && !((commondom->flags & BB_IRREDUCIBLE_LOOP)
+			   && flow_loop_nested_p (commondom->loop_father,
+						  bb->loop_father))
+		      && !((bb->flags & BB_IRREDUCIBLE_LOOP)
+			   && flow_loop_nested_p (bb->loop_father,
+						  commondom->loop_father)))
 		    continue;
 		  bb = EDGE_PRED (bb, PHI_ARG_INDEX_FROM_USE (use_p))->src;
 		}