c: Fix handling of [[gnu::musttail] return in if and else bodies [PR119311]

The following new testcase FAILs with C (and succeeds with C++).
c_parser_handle_musttail is used in c_parser_compound_statement_nostart
where it is directly passed to c_parser_statement_after_labels, and in
c_parser_all_labels where it is returned.  Now, out of the 3
c_parser_all_labels callers, c_parser_statement passes it down to
c_parser_statement_after_labels, but c_parser_if_body and c_parser_else_body
don't, so if there are return statements with [[gnu::musttail]] or
[[clang::musttail]] directly in if or else bodies rather than wrapped with
{}s, we throw that information away.

2025-03-18  Jakub Jelinek  <jakub@redhat.com>

	PR c/119311
	* c-parser.cc (c_parser_if_body): Pass result of c_parser_all_labels
	as last argument to c_parser_statement_after_labels.
	(c_parser_else_body): Likewise.

	* c-c++-common/musttail14.c: Use * instead of \* in the regexps.
	* c-c++-common/musttail25.c: New test.

1 files changed, 28 insertions, 0 deletions

diff --git a/gcc/testsuite/c-c++-common/musttail25.c b/gcc/testsuite/c-c++-common/musttail25.c
new file mode 100644
index 0000000..ab28698
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/musttail25.c
@@ -0,0 +1,28 @@
+/* PR c/119311 */
+/* { dg-do compile { target musttail } } */
+/* { dg-options "-O2 -fdump-tree-optimized" } */
+/* { dg-final { scan-tree-dump-times "  \[^\n\r]* = bar \\\(\[^\n\r]*\\\); \\\[tail call\\\] \\\[must tail call\\\]" 1 "optimized" } } */
+/* { dg-final { scan-tree-dump-times "  \[^\n\r]* = baz \\\(\[^\n\r]*\\\); \\\[tail call\\\] \\\[must tail call\\\]" 1 "optimized" } } */
+/* { dg-final { scan-tree-dump-not "  (?:bar|baz) \\\(\[^\n\r]*\\\); \\\[tail call\\\]" "optimized" } } */
+
+
+[[gnu::noipa]] int
+bar (int x, int y)
+{
+  return x + y;
+}
+
+[[gnu::noipa]] int
+baz (int x, int y)
+{
+  return x * y;
+}
+
+int
+foo (int a, int b)
+{
+  if (a > b)
+    [[gnu::musttail]] return bar (a - b, b);
+  else
+    [[gnu::musttail]] return baz (a, b - a);
+}