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 --git a/gcc/testsuite/gcc.dg/torture/pr109331.c b/gcc/testsuite/gcc.dg/torture/pr109331.c
new file mode 100644 (file)
index 0000000..72c57b9
--- /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 bb0fa306312fa3a10dfd03336da05ea3435c90c3..9b567440ba4f1cb40f1507984e5d4e023623f834 100644 (file)
--- 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)