Bug 1501903 - Cache the results of inThirdPartyPath. r=andi

The function is called a lot for the same paths and is rather costly, so
cache the results for each path.

Depends on D9758

Differential Revision: https://phabricator.services.mozilla.com/D9759

--HG--
extra : moz-landing-system : lando

build/clang-plugin/MozCheckAction.cpp

@@ -23,3 +23,5 @@ public:
 
 static FrontendPluginRegistry::Add<MozCheckAction> X("moz-check",
                                                      "check moz action");
+
+DenseMap<unsigned, bool> InThirdPartyPathCache;

build/clang-plugin/Utils.h

@@ -345,9 +345,17 @@ inline bool isPlacementNew(const CXXNewExpr *Expression) {
   return true;
 }
 
+extern DenseMap<unsigned, bool> InThirdPartyPathCache;
+
 inline bool inThirdPartyPath(SourceLocation Loc, const SourceManager &SM) {
   Loc = SM.getFileLoc(Loc);
 
+  unsigned id = SM.getFileID(Loc).getHashValue();
+  auto pair = InThirdPartyPathCache.find(id);
+  if (pair != InThirdPartyPathCache.end()) {
+    return pair->second;
+  }
+
   SmallString<1024> RawFileName = SM.getFilename(Loc);
   llvm::sys::fs::make_absolute(RawFileName);
   SmallString<1024> FileName;
@@ -374,11 +382,13 @@ inline bool inThirdPartyPath(SourceLocation Loc, const SourceManager &SM) {
 
       // We found a match!
       if (IThirdPartyB == ThirdPartyE) {
+        InThirdPartyPathCache.insert(std::make_pair(id, true));
         return true;
       }
     }
   }
 
+  InThirdPartyPathCache.insert(std::make_pair(id, false));
   return false;
 }