tree-optimization/107447 - avoid hoisting returns-twice calls in LIM

The following makes sure to not hoist returns-twice calls in LIM
since we have no way to move the abnormal edge associated with it
and we are prone having stray abnormal edges in the IL which will
then cause IL verification failures even when the actual call
does not return twice.

	PR tree-optimization/107447
	* tree-ssa-loop-im.cc (determine_max_movement): Do not
	hoist returns-twice calls.

	* gcc.dg/torture/pr107447.c: New testcase.

2 files changed, 32 insertions, 4 deletions

diff --git a/gcc/testsuite/gcc.dg/torture/pr107447.c b/gcc/testsuite/gcc.dg/torture/pr107447.c
new file mode 100644
index 0000000..06f7b7b
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/torture/pr107447.c
@@ -0,0 +1,23 @@
+/* { dg-do compile } */
+
+int n;
+
+void
+bar (int, int);
+
+__attribute__ ((noinline, returns_twice)) int
+zero (void)
+{
+  return 0;
+}
+
+void
+foo (void)
+{
+  (void) zero ();
+
+  n = 0;
+
+  for (;;)
+    bar (zero (), n);
+}
diff --git a/gcc/tree-ssa-loop-im.cc b/gcc/tree-ssa-loop-im.cc
index 2ea8150..2119d40 100644
--- a/gcc/tree-ssa-loop-im.cc
+++ b/gcc/tree-ssa-loop-im.cc
@@ -835,10 +835,15 @@ determine_max_movement (gimple *stmt, bool must_preserve_exec)
 
       return true;
     }
-  else
-    FOR_EACH_SSA_TREE_OPERAND (val, stmt, iter, SSA_OP_USE)
-      if (!add_dependency (val, lim_data, loop, true))
-	return false;
+
+  /* A stmt that receives abnormal edges cannot be hoisted.  */
+  if (is_a <gcall *> (stmt)
+      && (gimple_call_flags (stmt) & ECF_RETURNS_TWICE))
+    return false;
+
+  FOR_EACH_SSA_TREE_OPERAND (val, stmt, iter, SSA_OP_USE)
+    if (!add_dependency (val, lim_data, loop, true))
+      return false;
 
   if (gimple_vuse (stmt))
     {