[clang] [clang] Avoid calling isInSystemMacro() too often (PR #182217)

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang

Author: Timm Baeder (tbaederr)

<details>
<summary>Changes</summary>

This caused a performance regression as reported in https://github.com/llvm/llvm-project/pull/141950

---
Full diff: https://github.com/llvm/llvm-project/pull/182217.diff


1 Files Affected:

- (modified) clang/lib/Basic/DiagnosticIDs.cpp (+2-2) 


``````````diff
diff --git a/clang/lib/Basic/DiagnosticIDs.cpp b/clang/lib/Basic/DiagnosticIDs.cpp
index 804f0d9957f23..fcd2d9f34414e 100644
--- a/clang/lib/Basic/DiagnosticIDs.cpp
+++ b/clang/lib/Basic/DiagnosticIDs.cpp
@@ -570,13 +570,13 @@ DiagnosticIDs::getDiagnosticSeverity(unsigned DiagID, SourceLocation Loc,
   // We also ignore warnings due to system macros. As above, we respect the
   // ForceSystemWarnings override.
   if (State->SuppressSystemWarnings && !Diag.getForceSystemWarnings() &&
-      Loc.isValid() && SM.isInSystemMacro(Loc)) {
+      Loc.isValid()) {
 
     bool ShowInSystemMacro = true;
     if (const StaticDiagInfoRec *Rec = GetDiagInfo(DiagID))
       ShowInSystemMacro = Rec->WarnShowInSystemMacro;
 
-    if (!ShowInSystemMacro)
+    if (!ShowInSystemMacro && SM.isInSystemMacro(Loc))
       return diag::Severity::Ignored;
   }
   // Clang-diagnostics pragmas always take precedence over suppression mapping.

``````````

</details>


https://github.com/llvm/llvm-project/pull/182217