From d1c7837d2d6e5a2997228681166ed8c814891881 Mon Sep 17 00:00:00 2001
From: Richard Biener <rguenther@suse.de>
Date: Wed, 29 Jan 2025 13:25:14 +0100
Subject: [PATCH] tree-optimization/114052 - consider infinite sub-loops when
 lowering iter bound

When we walk stmts to find always executed stmts with UB in the last
iteration to be able to reduce the iteration count by one we fail
to consider infinite subloops in the last iteration that would make
such stmt not execute.  The following adds this.

	PR tree-optimization/114052
	* tree-ssa-loop-niter.cc (maybe_lower_iteration_bound): Check
	for infinite subloops we might not exit.

	* gcc.dg/pr114052-1.c: New testcase.
---
 gcc/testsuite/gcc.dg/pr114052-1.c | 41 +++++++++++++++++++++++++++++++
 gcc/tree-ssa-loop-niter.cc        |  9 ++++++-
 2 files changed, 49 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/gcc.dg/pr114052-1.c

diff --git a/gcc/testsuite/gcc.dg/pr114052-1.c b/gcc/testsuite/gcc.dg/pr114052-1.c
new file mode 100644
index 00000000000..98e93bf670d
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr114052-1.c
@@ -0,0 +1,41 @@
+/* { dg-do run } */
+/* { dg-require-effective-target signal } */
+/* { dg-require-effective-target alarm } */
+/* { dg-options "-O2" } */
+
+#include <stdint.h>
+#include <unistd.h>
+#include <signal.h>
+#include <stdlib.h>
+
+volatile int y;
+void __attribute__((noipa)) put(int x)
+{
+  if (y)
+    __builtin_printf ("%i\n", x);
+}
+
+void __attribute__((noipa)) f(void)
+{
+  int counter = 0;
+  while (1) {
+      if (counter >= 2) continue;
+      put (counter++);
+  }
+}
+
+void do_exit (int i)
+{
+  exit (0);
+}
+
+int main()
+{
+  struct sigaction s;
+  sigemptyset (&s.sa_mask);
+  s.sa_handler = do_exit;
+  s.sa_flags = 0;
+  sigaction (SIGALRM, &s, NULL);
+  alarm (1);
+  f();
+}
diff --git a/gcc/tree-ssa-loop-niter.cc b/gcc/tree-ssa-loop-niter.cc
index de8d5ae6233..7743970bf3d 100644
--- a/gcc/tree-ssa-loop-niter.cc
+++ b/gcc/tree-ssa-loop-niter.cc
@@ -4757,7 +4757,14 @@ maybe_lower_iteration_bound (class loop *loop)
           FOR_EACH_EDGE (e, ei, bb->succs)
 	    {
 	      if (loop_exit_edge_p (loop, e)
-		  || e == loop_latch_edge (loop))
+		  || e == loop_latch_edge (loop)
+		  /* When exiting an inner loop, verify it is finite.  */
+		  || (!flow_bb_inside_loop_p (bb->loop_father, e->dest)
+		      && !finite_loop_p (bb->loop_father))
+		  /* When we enter an irreducible region and the entry
+		     does not contain a bounding stmt assume it might be
+		     infinite.  */
+		  || (bb->flags & BB_IRREDUCIBLE_LOOP))
 		{
 		  found_exit = true;
 		  break;
-- 
2.47.3