https://github.com/AnonMiraj created https://github.com/llvm/llvm-project/pull/208862
While profiling Linux headers, I noticed that `Preprocessor::CheckMacroName` performs expensive source-location queries for every macro, even when no diagnostic is possible. We can avoid this overhead by only performing these checks when the macro name is actually a reserved identifier or keyword, skipping them entirely for ordinary macros. | | basket Ir | | --- | --- | | before | 10,690,004,315 | | after | 10,649,181,540 | | **Δ** | **−40.8M (−0.38%)** | this is a follow up to #137306 and #139492 >From fcf318165e95224d26c37b0da81f1c6bb0f6399c Mon Sep 17 00:00:00 2001 From: Anonmiraj <[email protected]> Date: Sat, 11 Jul 2026 02:51:32 +0300 Subject: [PATCH] [clang] Skip macro source-location check for names that can't warn --- clang/lib/Lex/PPDirectives.cpp | 18 +++++++++--------- 1 file changed, 9 insertions(+), 9 deletions(-) diff --git a/clang/lib/Lex/PPDirectives.cpp b/clang/lib/Lex/PPDirectives.cpp index eb21a510dcf83..0323743ad9b20 100644 --- a/clang/lib/Lex/PPDirectives.cpp +++ b/clang/lib/Lex/PPDirectives.cpp @@ -396,16 +396,16 @@ bool Preprocessor::CheckMacroName(Token &MacroNameTok, MacroUse isDefineUndef, // Macro names with reserved identifiers are accepted if built-in or passed // through the command line (the later may be present if -dD was used to // generate the preprocessed file). - // NB: isInPredefinedFile() is relatively expensive, so keep it at the end - // of the condition. - if (!SourceMgr.isInSystemHeader(MacroNameLoc) && + // NB: isInPredefinedFile() (via getPresumedLoc) is relatively expensive, so + // only run it for names that can actually warn. + MacroDiag D = MD_NoWarn; + if (isDefineUndef == MU_Define) { + D = shouldWarnOnMacroDef(*this, II); + } + else if (isDefineUndef == MU_Undef) + D = shouldWarnOnMacroUndef(*this, II); + if (D != MD_NoWarn && !SourceMgr.isInSystemHeader(MacroNameLoc) && !SourceMgr.isInPredefinedFile(MacroNameLoc)) { - MacroDiag D = MD_NoWarn; - if (isDefineUndef == MU_Define) { - D = shouldWarnOnMacroDef(*this, II); - } - else if (isDefineUndef == MU_Undef) - D = shouldWarnOnMacroUndef(*this, II); if (D == MD_KeywordDef) { // We do not want to warn on some patterns widely used in configuration // scripts. This requires analyzing next tokens, so do not issue warnings _______________________________________________ cfe-commits mailing list [email protected] https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
