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.

3 files changed, 35 insertions, 7 deletions

diff --git a/gcc/c/c-parser.cc b/gcc/c/c-parser.cc
index 93233a87..d49d5c5 100644
--- a/gcc/c/c-parser.cc
+++ b/gcc/c/c-parser.cc
@@ -8545,8 +8545,8 @@ c_parser_if_body (c_parser *parser, bool *if_p,
   token_indent_info body_tinfo
     = get_token_indent_info (c_parser_peek_token (parser));
   tree before_labels = get_before_labels ();
+  attr_state a = c_parser_all_labels (parser);
 
-  c_parser_all_labels (parser);
   if (c_parser_next_token_is (parser, CPP_SEMICOLON))
     {
       location_t loc = c_parser_peek_token (parser)->location;
@@ -8561,7 +8561,7 @@ c_parser_if_body (c_parser *parser, bool *if_p,
   else
     {
       body_loc_after_labels = c_parser_peek_token (parser)->location;
-      c_parser_statement_after_labels (parser, if_p, before_labels);
+      c_parser_statement_after_labels (parser, if_p, before_labels, NULL, a);
     }
 
   token_indent_info next_tinfo
@@ -8590,8 +8590,8 @@ c_parser_else_body (c_parser *parser, const token_indent_info &else_tinfo,
     = get_token_indent_info (c_parser_peek_token (parser));
   location_t body_loc_after_labels = UNKNOWN_LOCATION;
   tree before_labels = get_before_labels ();
+  attr_state a = c_parser_all_labels (parser);
 
-  c_parser_all_labels (parser);
   if (c_parser_next_token_is (parser, CPP_SEMICOLON))
     {
       location_t loc = c_parser_peek_token (parser)->location;
@@ -8605,7 +8605,7 @@ c_parser_else_body (c_parser *parser, const token_indent_info &else_tinfo,
     {
       if (!c_parser_next_token_is (parser, CPP_OPEN_BRACE))
 	body_loc_after_labels = c_parser_peek_token (parser)->location;
-      c_parser_statement_after_labels (parser, NULL, before_labels, chain);
+      c_parser_statement_after_labels (parser, NULL, before_labels, chain, a);
     }
 
   token_indent_info next_tinfo
diff --git a/gcc/testsuite/c-c++-common/musttail14.c b/gcc/testsuite/c-c++-common/musttail14.c
index e95bc9b..56a52b8 100644
--- a/gcc/testsuite/c-c++-common/musttail14.c
+++ b/gcc/testsuite/c-c++-common/musttail14.c
@@ -1,9 +1,9 @@
 /* PR tree-optimization/118430 */
 /* { 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]* = freddy \\\(\[^\n\r]\*\\\); \\\[tail call\\\] \\\[must tail call\\\]" 1 "optimized" } } */
-/* { dg-final { scan-tree-dump-not "  (?:bar|freddy) \\\(\[^\n\r]\*\\\); \\\[tail call\\\]" "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]* = freddy \\\(\[^\n\r]*\\\); \\\[tail call\\\] \\\[must tail call\\\]" 1 "optimized" } } */
+/* { dg-final { scan-tree-dump-not "  (?:bar|freddy) \\\(\[^\n\r]*\\\); \\\[tail call\\\]" "optimized" } } */
 
 __attribute__ ((noipa)) void
 foo (int x)
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);
+}