[analyzer] Fix StdLibraryFunctionsChecker performance issue

`initFunctionSummaries` lazily initializes a data structure with
function summaries for standard library functions.  It is called for
every pre-, post-, and eval-call events, i.e. 3 times for each call on
the path.  If the initialization doesn't find any standard library
functions in the translation unit, it will get re-tried (with the same
effect) many times even for small translation units.

For projects not using standard libraries, the speed-up can reach 50%
after this patch.

Differential Revision: https://reviews.llvm.org/D98244

1 files changed, 4 insertions, 1 deletions

diff --git a/clang/lib/StaticAnalyzer/Checkers/StdLibraryFunctionsChecker.cpp b/clang/lib/StaticAnalyzer/Checkers/StdLibraryFunctionsChecker.cpp
index d1c366a..38a9d4b 100644
--- a/clang/lib/StaticAnalyzer/Checkers/StdLibraryFunctionsChecker.cpp
+++ b/clang/lib/StaticAnalyzer/Checkers/StdLibraryFunctionsChecker.cpp
@@ -508,6 +508,7 @@ class StdLibraryFunctionsChecker
   mutable FunctionSummaryMapType FunctionSummaryMap;
 
   mutable std::unique_ptr<BugType> BT_InvalidArg;
+  mutable bool SummariesInitialized = false;
 
   static SVal getArgSVal(const CallEvent &Call, ArgNo ArgN) {
     return ArgN == Ret ? Call.getReturnValue() : Call.getArgSVal(ArgN);
@@ -823,7 +824,7 @@ StdLibraryFunctionsChecker::findFunctionSummary(const CallEvent &Call,
 
 void StdLibraryFunctionsChecker::initFunctionSummaries(
     CheckerContext &C) const {
-  if (!FunctionSummaryMap.empty())
+  if (SummariesInitialized)
     return;
 
   SValBuilder &SVB = C.getSValBuilder();
@@ -2485,6 +2486,8 @@ void StdLibraryFunctionsChecker::initFunctionSummaries(
         Signature(ArgTypes{VoidPtrRestrictTy}, RetType{VoidTy}),
         Summary(EvalCallAsPure));
   }
+
+  SummariesInitialized = true;
 }
 
 void ento::registerStdCLibraryFunctionsChecker(CheckerManager &mgr) {