[gcc r14-4229] c++: unroll pragma in templates [PR111529]

[gcc r14-4229] c++: unroll pragma in templates [PR111529]

[Jason Merrill]

https://gcc.gnu.org/g:9c62af101e11e1cce573c2b3d2e18b403412dbc8

commit r14-4229-g9c62af101e11e1cce573c2b3d2e18b403412dbc8
Author: Jason Merrill <jason@redhat.com>
Date:   Fri Sep 22 12:10:11 2023 +0100

    c++: unroll pragma in templates [PR111529]
    
    We were failing to handle ANNOTATE_EXPR in tsubst_copy_and_build, leading to
    problems with substitution of any wrapped expressions.
    
    Let's also not tell users that lambda templates are available in C++14.
    
            PR c++/111529
    
    gcc/cp/ChangeLog:
    
            * parser.cc (cp_parser_lambda_declarator_opt): Don't suggest
            -std=c++14 for lambda templates.
            * pt.cc (tsubst_expr): Move ANNOTATE_EXPR handling...
            (tsubst_copy_and_build): ...here.
    
    gcc/testsuite/ChangeLog:
    
            * g++.dg/ext/unroll-4.C: New test.

Diff:
---
 gcc/cp/parser.cc                    |  7 ++-----
 gcc/cp/pt.cc                        | 14 +++++++-------
 gcc/testsuite/g++.dg/ext/unroll-4.C | 16 ++++++++++++++++
 3 files changed, 25 insertions(+), 12 deletions(-)

diff --git a/gcc/cp/parser.cc b/gcc/cp/parser.cc
index 0e1cbbfe051..f3abae716fe 100644
--- a/gcc/cp/parser.cc
+++ b/gcc/cp/parser.cc
@@ -11695,11 +11695,8 @@ cp_parser_lambda_declarator_opt (cp_parser* parser, tree lambda_expr)
      an opening angle if present.  */
   if (cp_lexer_next_token_is (parser->lexer, CPP_LESS))
     {
-      if (cxx_dialect < cxx14)
-	pedwarn (parser->lexer->next_token->location, OPT_Wc__14_extensions,
-		 "lambda templates are only available with "
-		 "%<-std=c++14%> or %<-std=gnu++14%>");
-      else if (pedantic && cxx_dialect < cxx20)
+      if (cxx_dialect < cxx20
+	  && (pedantic || cxx_dialect < cxx14))
 	pedwarn (parser->lexer->next_token->location, OPT_Wc__20_extensions,
 		 "lambda templates are only available with "
 		 "%<-std=c++20%> or %<-std=gnu++20%>");
diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index 9b100e12a23..ea5379098a5 100644
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -19913,13 +19913,6 @@ tsubst_expr (tree t, tree args, tsubst_flags_t complain, tree in_decl)
 				    templated_operator_saved_lookups (t),
 				    complain));
 
-    case ANNOTATE_EXPR:
-      tmp = RECUR (TREE_OPERAND (t, 0));
-      RETURN (build3_loc (EXPR_LOCATION (t), ANNOTATE_EXPR,
-			  TREE_TYPE (tmp), tmp,
-			  RECUR (TREE_OPERAND (t, 1)),
-			  RECUR (TREE_OPERAND (t, 2))));
-
     case PREDICT_EXPR:
       RETURN (add_stmt (copy_node (t)));
 
@@ -21868,6 +21861,13 @@ tsubst_copy_and_build (tree t,
 	RETURN (op);
       }
 
+    case ANNOTATE_EXPR:
+      op1 = RECUR (TREE_OPERAND (t, 0));
+      RETURN (build3_loc (EXPR_LOCATION (t), ANNOTATE_EXPR,
+			  TREE_TYPE (op1), op1,
+			  RECUR (TREE_OPERAND (t, 1)),
+			  RECUR (TREE_OPERAND (t, 2))));
+
     default:
       /* Handle Objective-C++ constructs, if appropriate.  */
       {
diff --git a/gcc/testsuite/g++.dg/ext/unroll-4.C b/gcc/testsuite/g++.dg/ext/unroll-4.C
new file mode 100644
index 00000000000..d488aca974e
--- /dev/null
+++ b/gcc/testsuite/g++.dg/ext/unroll-4.C
@@ -0,0 +1,16 @@
+// PR c++/111529
+// { dg-do compile { target c++11 } }
+// { dg-additional-options -Wno-c++20-extensions }
+
+template <int>
+void f() {
+  []<int>() {
+    #pragma GCC unroll 9
+    for (int i = 1; i; --i) {
+    }
+  };
+}
+
+int main() {
+  f<0>();
+}