[PATCH] tree-optimization/107301 - check if we can duplicate block before doing so

[Richard Biener via Gcc-patches]

Path isolation failed to do that.

Bootstrapped and tested on x86_64-unknown-linux-gnu, pushed.

        PR tree-optimization/107301
        * gimple-ssa-isolate-paths.cc (handle_return_addr_local_phi_arg):
        Check whether we can duplicate the block.
        (find_implicit_erroneous_behavior): Likewise.

        * gcc.dg/torture/pr107301.c: New testcase.
---
 gcc/gimple-ssa-isolate-paths.cc         |  6 ++++--
 gcc/testsuite/gcc.dg/torture/pr107301.c | 15 +++++++++++++++
 2 files changed, 19 insertions(+), 2 deletions(-)
 create mode 100644 gcc/testsuite/gcc.dg/torture/pr107301.c

diff --git a/gcc/gimple-ssa-isolate-paths.cc b/gcc/gimple-ssa-isolate-paths.cc
index 87ecd19ef4a..e4a4e08f549 100644
--- a/gcc/gimple-ssa-isolate-paths.cc
+++ b/gcc/gimple-ssa-isolate-paths.cc
@@ -647,7 +647,8 @@ handle_return_addr_local_phi_arg (basic_block bb, 
basic_block duplicate,
       if (!maybe
          && (flag_isolate_erroneous_paths_dereference
              || flag_isolate_erroneous_paths_attribute)
-         && gimple_bb (use_stmt) == bb)
+         && gimple_bb (use_stmt) == bb
+         && (duplicate || can_duplicate_block_p (bb)))
        {
          duplicate = isolate_path (bb, duplicate, e,
                                    use_stmt, lhs, true);
@@ -765,7 +766,8 @@ find_implicit_erroneous_behavior (void)
                    ? gimple_location (use_stmt)
                    : phi_arg_loc;
 
-                 if (stmt_uses_name_in_undefined_way (use_stmt, lhs, loc))
+                 if (stmt_uses_name_in_undefined_way (use_stmt, lhs, loc)
+                     && (duplicate || can_duplicate_block_p (bb)))
                    {
                      duplicate = isolate_path (bb, duplicate, e,
                                                use_stmt, lhs, false);
diff --git a/gcc/testsuite/gcc.dg/torture/pr107301.c 
b/gcc/testsuite/gcc.dg/torture/pr107301.c
new file mode 100644
index 00000000000..5f0afcc0d10
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/torture/pr107301.c
@@ -0,0 +1,15 @@
+/* { dg-do compile } */
+
+__attribute__ ((pure, returns_twice)) int
+foo (int x)
+{
+  int a;
+
+  a = x ? 3 : 0;
+  x /= a;
+  a = foo (x);
+  if (x == a)
+    __builtin_unreachable ();
+
+  return 0;
+}
-- 
2.35.3