[libclang][index] Skip already indexed function bodies more aggressively

[jkorous]

Summary

It seems like there's no reason not to use the up-to-date information we have in TUSkipBodyControl::isParsed().

I compared performance on small part of clang compilation database - seems like it might be tiny bit faster.

WDYT?

/usr/bin/time fish -c "bin/c-index-test -index-compile-db compile_commands.json > /dev/null ^ /dev/null"

master 30.66 real 30.20 user 0.45 sys
master 30.49 real 29.98 user 0.47 sys
master 30.34 real 29.88 user 0.45 sys

patched 30.41 real 29.95 user 0.45 sys
patched 29.89 real 29.44 user 0.44 sys
patched 29.72 real 29.26 user 0.45 sys

[akyrtzi]

Are you sure the difference is not random noise? It's not clear to me under which conditions you would encounter the same region in NewParsedRegions within the same TU. I assume this would be the case if the same file is parsed multiple times, but I'd expect this to be uncommon within the same TU.
I'd recommend to add some counters of when NewParsedRegions.count(region) is true and when ParsedRegions.count(region) is true, and print them at the end.

[jkorous]

Actually, I suppose you are right - it would be ODR-violation otherwise. Never mind.

clang/tools/libclang/Indexing.cpp

 public:
   ~SessionSkipBodyData() = default;
 
   void copyTo(PPRegionSetTy &Set) {
     std::lock_guard<std::mutex> MG(Mux);
     Set = ParsedRegions;
   }
 
-  void update(ArrayRef<PPRegion> Regions) {
+  void update(const PPRegionSetTy& Regions) {
     std::lock_guard<std::mutex> MG(Mux);
     ParsedRegions.insert(Regions.begin(), Regions.end());
   }
 };
 
 class TUSkipBodyControl {
   SessionSkipBodyData &SessionData;
   PPConditionalDirectiveRecord &PPRec;
   Preprocessor &PP;
 
   PPRegionSetTy ParsedRegions;
-  SmallVector<PPRegion, 32> NewParsedRegions;
+  PPRegionSetTy NewParsedRegions;
+
   PPRegion LastRegion;
   bool LastIsParsed;
 
 public:
   TUSkipBodyControl(SessionSkipBodyData &sessionData,
                     PPConditionalDirectiveRecord &ppRec,
                     Preprocessor &pp)
     : SessionData(sessionData), PPRec(ppRec), PP(pp) {
     SessionData.copyTo(ParsedRegions);
   }
 
   bool isParsed(SourceLocation Loc, FileID FID, const FileEntry *FE) {
     PPRegion region = getRegion(Loc, FID, FE);
     if (region.isInvalid())
       return false;
 
     // Check common case, consecutive functions in the same region.
     if (LastRegion == region)
       return LastIsParsed;
 
     LastRegion = region;
-    LastIsParsed = ParsedRegions.count(region);
+    LastIsParsed = NewParsedRegions.count(region) || ParsedRegions.count(region);
     if (!LastIsParsed)
-      NewParsedRegions.push_back(region);
+      NewParsedRegions.insert(std::move(region));
     return LastIsParsed;
   }
 
   void finished() {
     SessionData.update(NewParsedRegions);
   }
 
 private: