Merge pull request #7776 from apple/jan_svoboda/20230725-diag-pragma-mappings-scanner

[clang][deps] Skip writing `DIAG_PRAGMA_MAPPINGS` record

Author: jansvoboda11

clang/include/clang/Lex/HeaderSearchOptions.h

@@ -224,6 +224,10 @@ class HeaderSearchOptions {
   /// Primarily used to speed up deserialization during dependency scanning.
   unsigned ModulesSkipHeaderSearchPaths : 1;
 
+  /// Whether to entirely skip writing pragma diagnostic mappings.
+  /// Primarily used to speed up deserialization during dependency scanning.
+  unsigned ModulesSkipPragmaDiagnosticMappings : 1;
+
   unsigned ModulesHashContent : 1;
 
   /// Whether we should include all things that could impact the module in the
@@ -244,7 +248,8 @@ class HeaderSearchOptions {
         ValidateASTInputFilesContent(false), UseDebugInfo(false),
         ModulesValidateDiagnosticOptions(true),
         ModulesSkipDiagnosticOptions(false),
-        ModulesSkipHeaderSearchPaths(false), ModulesHashContent(false),
+        ModulesSkipHeaderSearchPaths(false),
+        ModulesSkipPragmaDiagnosticMappings(false), ModulesHashContent(false),
         ModulesStrictContextHash(false) {}
 
   /// AddPath - Add the \p Path path to the specified \p Group list.

clang/lib/Serialization/ASTWriter.cpp

@@ -1267,8 +1267,8 @@ void ASTWriter::writeUnhashedControlBlock(Preprocessor &PP,
   AddString(FSOpts.WorkingDir, Record);
   Stream.EmitRecord(FILE_SYSTEM_OPTIONS, Record);
 
-  // Write out the diagnostic/pragma mappings.
-  WritePragmaDiagnosticMappings(Diags, /* isModule = */ WritingModule);
+  if (!HSOpts.ModulesSkipPragmaDiagnosticMappings)
+    WritePragmaDiagnosticMappings(Diags, /* isModule = */ WritingModule);
 
   // Header search entry usage.
   auto HSEntryUsage = PP.getHeaderSearchInfo().computeUserEntryUsage();

clang/lib/Tooling/DependencyScanning/DependencyScanningWorker.cpp

@@ -436,6 +436,8 @@ class DependencyScanningAction : public tooling::ToolAction {
     ScanInstance.getHeaderSearchOpts().ModulesStrictContextHash = true;
     ScanInstance.getHeaderSearchOpts().ModulesSkipDiagnosticOptions = true;
     ScanInstance.getHeaderSearchOpts().ModulesSkipHeaderSearchPaths = true;
+    ScanInstance.getHeaderSearchOpts().ModulesSkipPragmaDiagnosticMappings =
+        true;
 
     // Avoid some checks and module map parsing when loading PCM files.
     ScanInstance.getPreprocessorOpts().ModulesCheckRelocated = false;