• GCC: xgcc version 16.0.1 20260203 (experimental)

• Host: aarch64-unknown-linux-gnu, DejaGnu/Expect standard with Ubuntu

• Testcase gcc/testsuite/gcc.dg/pr105495.c:

/* { dg-do compile { target aarch64*-*-* } } */
/* { dg-options "-O2 -fdump-tree-optimized" } */
typedef struct { int b; } cond;
__attribute__((noinline)) int __MCF_batch_release_common (cond *p, int c);
__attribute__((noinline)) int test_struct (cond *p, int x) {
  cond c = { x }, n = { 2 };
  __atomic_compare_exchange (p, &c, &n, 1, 0, 0);
  return __MCF_batch_release_common (p, x);
}
/* { dg-final { scan-tree-dump "__MCF_batch_release_common.*\\\[tail call\\\]" "optimized" } } */

• Run:

make -j1 check-gcc RUNTESTFLAGS="dg.exp=pr105495.c"

Result:

FAIL: ... scan-tree-dump optimized "__MCF_batch_release_common.*\\[tail call\\]"

Question:

Is the escaping above the recommended/canonical form for matching [tail call] markers in tree dumps?

If the dump doesn’t contain [tail call], what GCC passes/flags can be used to confirm whether sibling-call optimization happened (tree vs rtl), and what’s the best testsuite check?