[PATCH] D33493: Speed up preamble loading

[Ivan Donchevskii via Phabricator via cfe-commits]

yvvan updated this revision to Diff 101995.
yvvan added a comment.

"what kind of performance benefits do you get for the preamble load times?"
In cases where many windows headers are included preamble loading takes almost the half of reparse time. With this fix time to load preamble goes towards zero.


https://reviews.llvm.org/D33493

Files:
  include/clang/Frontend/ASTUnit.h
  lib/Frontend/ASTUnit.cpp


Index: lib/Frontend/ASTUnit.cpp
===================================================================
--- lib/Frontend/ASTUnit.cpp
+++ lib/Frontend/ASTUnit.cpp
@@ -1159,6 +1159,8 @@
   if (SavedMainFileBuffer)
     TranslateStoredDiagnostics(getFileManager(), getSourceManager(),
                                PreambleDiagnostics, StoredDiagnostics);
+  else
+    PreambleSrcLocCache.clear();
 
   if (!Act->Execute())
     goto error;
@@ -2601,23 +2603,26 @@
   // remap all the locations to the new view. This includes the diag location,
   // any associated source ranges, and the source ranges of associated fix-its.
   // FIXME: There should be a cleaner way to do this.
-
   SmallVector<StoredDiagnostic, 4> Result;
   Result.reserve(Diags.size());
-  const FileEntry *PreviousFE = nullptr;
-  FileID FID;
+
   for (const StandaloneDiagnostic &SD : Diags) {
     // Rebuild the StoredDiagnostic.
     if (SD.Filename.empty())
       continue;
     const FileEntry *FE = FileMgr.getFile(SD.Filename);
     if (!FE)
       continue;
-    if (FE != PreviousFE) {
-      FID = SrcMgr.translateFile(FE);
-      PreviousFE = FE;
+    SourceLocation FileLoc;
+    auto ItFileID = PreambleSrcLocCache.find(SD.Filename);
+    if (ItFileID == PreambleSrcLocCache.end()) {
+      FileID FID = SrcMgr.translateFile(FE);
+      FileLoc = SrcMgr.getLocForStartOfFile(FID);
+      PreambleSrcLocCache[SD.Filename] = FileLoc;
+    } else {
+      FileLoc = ItFileID->getValue();
     }
-    SourceLocation FileLoc = SrcMgr.getLocForStartOfFile(FID);
+
     if (FileLoc.isInvalid())
       continue;
     SourceLocation L = FileLoc.getLocWithOffset(SD.LocOffset);
Index: include/clang/Frontend/ASTUnit.h
===================================================================
--- include/clang/Frontend/ASTUnit.h
+++ include/clang/Frontend/ASTUnit.h
@@ -188,6 +188,14 @@
   /// some number of calls.
   unsigned PreambleRebuildCounter;
 
+  /// \brief Cache pairs "filename - source location"
+  ///
+  /// Cache contains only source locations from preamble so it is
+  /// guaranteed that they stay valid when the SourceManager is recreated.
+  /// This cache is used when loading preambule to increase performance
+  /// of that loading. It must be cleared when preamble is recreated.
+  llvm::StringMap<SourceLocation> PreambleSrcLocCache;
+
 public:
   class PreambleData {
     const FileEntry *File;


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