tree-optimization/100934 - properly mark irreducible regions for DOM

The jump threading code requires marked irreducible regions for the
purpose of validating jump threading paths but DOM fails to provide
that resulting in mised number of iteration upper bounds clearing.

2021-06-14  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/100934
	* tree-ssa-dom.c (pass_dominator::execute): Properly
	mark irreducible regions.

	* gcc.dg/torture/pr100934.c: New testcase.

diff --git a/gcc/testsuite/gcc.dg/torture/pr100934.c b/gcc/testsuite/gcc.dg/torture/pr100934.c
new file mode 100644 (file)
index 0000000..43b7884
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/torture/pr100934.c
@@ -0,0 +1,21 @@
+/* { dg-do run } */
+
+int a, b, c, d, e;
+int main()
+{
+  int f = 0, g = 0;
+  for (; f < 2; f++)
+    {
+      int h, i;
+      for (h = 0; h < 2; h++)
+       {
+         b = e = g ? a % g : 0;
+         c = d;
+         for (i = 0; i < 1; i++)
+           g = 0;
+         for (; g < 2; g++)
+           ;
+       }
+    }
+  return 0;
+}

diff --git a/gcc/tree-ssa-dom.c b/gcc/tree-ssa-dom.c
index 075b1ccb9dea97ebc549b982c7520a6ef6a6f32c..c231e6c84677da0d3eb21cb66e8bce40182cc123 100644 (file)
--- a/gcc/tree-ssa-dom.c
+++ b/gcc/tree-ssa-dom.c
@@ -727,7 +727,8 @@ pass_dominator::execute (function *fun)
      gcc.dg/tree-ssa/pr21417.c can't be threaded if loop preheader is
      missing.  We should improve jump threading in future then
      LOOPS_HAVE_PREHEADERS won't be needed here.  */
-  loop_optimizer_init (LOOPS_HAVE_PREHEADERS | LOOPS_HAVE_SIMPLE_LATCHES);
+  loop_optimizer_init (LOOPS_HAVE_PREHEADERS | LOOPS_HAVE_SIMPLE_LATCHES
+                      | LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS);
 
   /* We need accurate information regarding back edges in the CFG
      for jump threading; this may include back edges that are not part of