[gcc r13-6928] tree-optimization/109331 - make sure to clean up the CFG after forwprop

[gcc r13-6928] tree-optimization/109331 - make sure to clean up the CFG after forwprop

[Richard Biener]

https://gcc.gnu.org/g:86efc490ab86bfa00720479b4714da23cd7df797

commit r13-6928-g86efc490ab86bfa00720479b4714da23cd7df797
Author: Richard Biener <rguenther@suse.de>
Date:   Wed Mar 29 11:59:16 2023 +0200

    tree-optimization/109331 - make sure to clean up the CFG after forwprop
    
    When forwprop discovers unreachable code or makes decisions based
    on unreachable edges make sure to cleanup the CFG since otherwise
    SSA form can become invalid.
    
            PR tree-optimization/109331
            * tree-ssa-forwprop.cc (pass_forwprop::execute): When we
            discover a taken edge make sure to cleanup the CFG.
    
            * gcc.dg/torture/pr109331.c: New testcase.

Diff:
---
 gcc/testsuite/gcc.dg/torture/pr109331.c | 16 ++++++++++++++++
 gcc/tree-ssa-forwprop.cc                |  6 +++++-
 2 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/gcc/testsuite/gcc.dg/torture/pr109331.c b/gcc/testsuite/gcc.dg/torture/pr109331.c
new file mode 100644
index 00000000000..72c57b9b74c
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/torture/pr109331.c
@@ -0,0 +1,16 @@
+/* { dg-do compile } */
+
+char *ustol_dpp;
+void ustol(int flags)
+{
+  char *s;
+  if (s)
+    flags |= 3;
+  switch (flags & 3)
+  case 3:
+    while (*s)
+    case '+':
+      ++s;
+  if (flags)
+    ustol_dpp = s;
+}
diff --git a/gcc/tree-ssa-forwprop.cc b/gcc/tree-ssa-forwprop.cc
index bb0fa306312..9b567440ba4 100644
--- a/gcc/tree-ssa-forwprop.cc
+++ b/gcc/tree-ssa-forwprop.cc
@@ -4046,7 +4046,11 @@ pass_forwprop::execute (function *fun)
 
       /* Mark outgoing exectuable edges.  */
       if (edge e = find_taken_edge (bb, NULL))
-	e->flags |= EDGE_EXECUTABLE;
+	{
+	  e->flags |= EDGE_EXECUTABLE;
+	  if (EDGE_COUNT (bb->succs) > 1)
+	    cfg_changed = true;
+	}
       else
 	{
 	  FOR_EACH_EDGE (e, ei, bb->succs)