[gcc r13-3545] tree-optimization/107447 - avoid hoisting returns-twice calls in LIM

[gcc r13-3545] tree-optimization/107447 - avoid hoisting returns-twice calls in LIM

[Richard Biener]

https://gcc.gnu.org/g:1add3635563b39e3c0e9bed4930d11b3f605fdd3

commit r13-3545-g1add3635563b39e3c0e9bed4930d11b3f605fdd3
Author: Richard Biener <rguenther@suse.de>
Date:   Fri Oct 28 14:20:36 2022 +0200

    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.

Diff:
---
 gcc/testsuite/gcc.dg/torture/pr107447.c | 23 +++++++++++++++++++++++
 gcc/tree-ssa-loop-im.cc                 | 13 +++++++++----
 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 00000000000..06f7b7b15ae
--- /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 2ea815050d1..2119d4072d3 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))
     {