[gcc r15-11486] middle-end/125156 - preserve edge flags in cleanup_control_expr_graph

https://gcc.gnu.org/g:99e00f7ee0e60c13a38d4c68197afd83862173fa

commit r15-11486-g99e00f7ee0e60c13a38d4c68197afd83862173fa
Author: Richard Biener <[email protected]>
Date:   Mon May 4 11:18:24 2026 +0200

    middle-end/125156 - preserve edge flags in cleanup_control_expr_graph
    
    cleanup_control_expr_graph when setting EDGE_FALLTHRU cleared all
    existing edge flags such as EDGE_IRREDUCIBLE_LOOP rather than
    just the no longer relevant EDGE_TRUE_VALUE and EDGE_FALSE_VALUE flags.
    
            PR middle-end/125156
            * tree-cfgcleanup.cc (cleanup_control_expr_graph): Clear
            EDGE_TRUE_VALUE and EDGE_FALSE_VALUE edge flags only.
    
            * gcc.dg/torture/pr125156.c: New testcase.
    
    (cherry picked from commit 7b804275b251cabc9699717713f3870b89ab3395)

Diff:
---
 gcc/testsuite/gcc.dg/torture/pr125156.c | 26 ++++++++++++++++++++++++++
 gcc/tree-cfgcleanup.cc                  |  3 ++-
 2 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/gcc/testsuite/gcc.dg/torture/pr125156.c b/gcc/testsuite/gcc.dg/torture/pr125156.c
new file mode 100644
index 000000000000..bb232b1a436c
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/torture/pr125156.c
@@ -0,0 +1,26 @@
+/* { dg-do compile } */
+
+#include <stdint.h>
+
+int64_t g1, g8;
+
+void g14()
+{
+  int16_t v5;
+  goto lbl_cont30;
+lbl_bf2:
+  g8 = 0;
+lbl_b5:
+  g1 = g1 - 8366249724514421075;
+  switch (v5)
+case 5:
+case 2:
+    goto lbl_b5;
+    goto lbl_bf2;
+lbl_cont30:
+    switch (v5)
+      {
+      case 0: goto lbl_bf2;
+      case 5: goto lbl_b5;
+      }
+}
diff --git a/gcc/tree-cfgcleanup.cc b/gcc/tree-cfgcleanup.cc
index 9a8a668e12b8..bae3215e29ec 100644
--- a/gcc/tree-cfgcleanup.cc
+++ b/gcc/tree-cfgcleanup.cc
@@ -200,7 +200,8 @@ cleanup_control_expr_graph (basic_block bb, gimple_stmt_iterator gsi)
 
   bitmap_set_bit (cfgcleanup_altered_bbs, bb->index);
   gsi_remove (&gsi, true);
-  taken_edge->flags = EDGE_FALLTHRU;
+  taken_edge->flags &= ~(EDGE_TRUE_VALUE|EDGE_FALSE_VALUE);
+  taken_edge->flags |= EDGE_FALLTHRU;
 
   return retval;
 }