[clang] [clang] [NFC] Skip macro source-location check for names that can't warn (PR #208862)

[via cfe-commits]

https://github.com/AnonMiraj updated https://github.com/llvm/llvm-project/pull/208862

>From fcf318165e95224d26c37b0da81f1c6bb0f6399c Mon Sep 17 00:00:00 2001
From: Anonmiraj <ezzibrahimx at gmail.com>
Date: Sat, 11 Jul 2026 02:51:32 +0300
Subject: [PATCH 1/2] [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

>From c4093a81e10cc2976ca179bb478e0a407778e38e Mon Sep 17 00:00:00 2001
From: Anonmiraj <ezzibrahimx at gmail.com>
Date: Sat, 11 Jul 2026 03:11:11 +0300
Subject: [PATCH 2/2] fix formatting

---
 clang/lib/Lex/PPDirectives.cpp | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/clang/lib/Lex/PPDirectives.cpp b/clang/lib/Lex/PPDirectives.cpp
index 0323743ad9b20..402b3f43d7fb9 100644
--- a/clang/lib/Lex/PPDirectives.cpp
+++ b/clang/lib/Lex/PPDirectives.cpp
@@ -401,8 +401,7 @@ bool Preprocessor::CheckMacroName(Token &MacroNameTok, MacroUse isDefineUndef,
   MacroDiag D = MD_NoWarn;
   if (isDefineUndef == MU_Define) {
     D = shouldWarnOnMacroDef(*this, II);
-  }
-  else if (isDefineUndef == MU_Undef)
+  } else if (isDefineUndef == MU_Undef)
     D = shouldWarnOnMacroUndef(*this, II);
   if (D != MD_NoWarn && !SourceMgr.isInSystemHeader(MacroNameLoc) &&
       !SourceMgr.isInPredefinedFile(MacroNameLoc)) {