[libcxx-commits] [libcxx] [libc++] Don't push and pop extensions diagnostics when using clang modules (PR #85917)

[Nikolas Klauser via libcxx-commits]

https://github.com/philnik777 created https://github.com/llvm/llvm-project/pull/85917

Clang modules take a significant compile time hit when pushing and popping diagnostics. Since all the headers are marked as system headers in the modulemap, we can simply disable this pushing and popping when building with clang modules.


>From 22ffb5122986b4dbc60c542946d88d0bd9e4e46b Mon Sep 17 00:00:00 2001
From: Nikolas Klauser <nikolasklauser at berlin.de>
Date: Wed, 20 Mar 2024 12:01:23 +0100
Subject: [PATCH] [libc++] Don't push and pop extensions diagnostics when using
 clang modules

---
 libcxx/include/__config | 31 ++++++++++++++++++++-----------
 1 file changed, 20 insertions(+), 11 deletions(-)

diff --git a/libcxx/include/__config b/libcxx/include/__config
index 11e13e0c24986a..d7f77e4a01ac88 100644
--- a/libcxx/include/__config
+++ b/libcxx/include/__config
@@ -838,21 +838,30 @@ typedef __char32_t char32_t;
 #  define _LIBCPP_CLANG_DIAGNOSTIC_IGNORED_CXX23_EXTENSION _LIBCPP_CLANG_DIAGNOSTIC_IGNORED("-Wc++2b-extensions")
 #endif
 
+#  if !__has_feature(modules)
+#    define _LIBCPP_PUSH_EXTENSION_DIAGNOSTICS                                                                         \
+      _LIBCPP_DIAGNOSTIC_PUSH                                                                                          \
+      _LIBCPP_CLANG_DIAGNOSTIC_IGNORED("-Wc++11-extensions")                                                           \
+      _LIBCPP_CLANG_DIAGNOSTIC_IGNORED("-Wc++14-extensions")                                                           \
+      _LIBCPP_CLANG_DIAGNOSTIC_IGNORED("-Wc++17-extensions")                                                           \
+      _LIBCPP_CLANG_DIAGNOSTIC_IGNORED("-Wc++20-extensions")                                                           \
+      _LIBCPP_CLANG_DIAGNOSTIC_IGNORED_CXX23_EXTENSION                                                                 \
+      _LIBCPP_GCC_DIAGNOSTIC_IGNORED("-Wc++14-extensions")                                                             \
+      _LIBCPP_GCC_DIAGNOSTIC_IGNORED("-Wc++17-extensions")                                                             \
+      _LIBCPP_GCC_DIAGNOSTIC_IGNORED("-Wc++20-extensions")                                                             \
+      _LIBCPP_GCC_DIAGNOSTIC_IGNORED("-Wc++23-extensions")
+#    define _LIBCPP_POP_EXTENSION_DIAGNOSTICS _LIBCPP_DIAGNOSTIC_POP
+#  else
+#    define _LIBCPP_PUSH_EXTENSION_DIAGNOSTICS
+#    define _LIBCPP_POP_EXTENSION_DIAGNOSTICS
+#  endif
+
 // Inline namespaces are available in Clang/GCC/MSVC regardless of C++ dialect.
 // clang-format off
-#  define _LIBCPP_BEGIN_NAMESPACE_STD _LIBCPP_DIAGNOSTIC_PUSH                                                          \
-                                      _LIBCPP_CLANG_DIAGNOSTIC_IGNORED("-Wc++11-extensions")                           \
-                                      _LIBCPP_CLANG_DIAGNOSTIC_IGNORED("-Wc++14-extensions")                           \
-                                      _LIBCPP_CLANG_DIAGNOSTIC_IGNORED("-Wc++17-extensions")                           \
-                                      _LIBCPP_CLANG_DIAGNOSTIC_IGNORED("-Wc++20-extensions")                           \
-                                      _LIBCPP_CLANG_DIAGNOSTIC_IGNORED_CXX23_EXTENSION                                 \
-                                      _LIBCPP_GCC_DIAGNOSTIC_IGNORED("-Wc++14-extensions")                             \
-                                      _LIBCPP_GCC_DIAGNOSTIC_IGNORED("-Wc++17-extensions")                             \
-                                      _LIBCPP_GCC_DIAGNOSTIC_IGNORED("-Wc++20-extensions")                             \
-                                      _LIBCPP_GCC_DIAGNOSTIC_IGNORED("-Wc++23-extensions")                             \
+#  define _LIBCPP_BEGIN_NAMESPACE_STD _LIBCPP_PUSH_EXTENSION_DIAGNOSTICS                                               \
                                       namespace _LIBCPP_TYPE_VISIBILITY_DEFAULT std {                                  \
                                inline namespace _LIBCPP_ABI_NAMESPACE {
-#  define _LIBCPP_END_NAMESPACE_STD }} _LIBCPP_DIAGNOSTIC_POP
+#  define _LIBCPP_END_NAMESPACE_STD }} _LIBCPP_POP_EXTENSION_DIAGNOSTICS
 
 #  define _LIBCPP_BEGIN_NAMESPACE_FILESYSTEM _LIBCPP_BEGIN_NAMESPACE_STD                                               \
                                              inline namespace __fs { namespace filesystem {