[IRSimilarity] Strip out the findSimilarity call from the constructor

[lanza]

Summary

Both doInitialize and runOnModule were running the entire analysis
due to the actual work being done in the constructor. Strip it out here
and only get the similarity during runOnModule.

[AndrewLitteken]

I don't think anything in future patches uses the constructor either so should be ok.

Besides the comment, this looks fine to me, but I would like one of the other reviewers to look at it since I'm still fairly new to LLVM developer community.

llvm/lib/Analysis/IRSimilarityIdentifier.cpp

664

We can get rid of/change this comment now.

[AndrewLitteken]

With the nit about the comment this LGTM

[paquette]

LGTM

[AndrewLitteken]

If there are no objections, can I merge this on behalf of @lanza?

llvm/include/llvm/Analysis/IRSimilarityIdentifier.h

 ///
 /// A list of the different similarity groups is then returned after
 /// analyzing the module.
 class IRSimilarityIdentifier {
 public:
   IRSimilarityIdentifier()
       : Mapper(&InstDataAllocator, &InstDataListAllocator) {}
 
-  /// \param M the module to find similarity in.
-  explicit IRSimilarityIdentifier(Module &M)
-      : Mapper(&InstDataAllocator, &InstDataListAllocator) {
-    findSimilarity(M);
-  }
-
 private:
   /// Map the instructions in the module to unsigned integers, using mapping
   /// already present in the Mapper if possible.
   ///
   /// \param [in] M Module - To map to integers.
   /// \param [in,out] InstrList - The vector to append IRInstructionData to.
   /// \param [in,out] IntegerMapping - The vector to append integers to.
   void populateMapper(Module &M, std::vector<IRInstructionData *> &InstrList,

llvm/lib/Analysis/IRSimilarityIdentifier.cpp

 
 IRSimilarityIdentifierWrapperPass::IRSimilarityIdentifierWrapperPass()
     : ModulePass(ID) {
   initializeIRSimilarityIdentifierWrapperPassPass(
       *PassRegistry::getPassRegistry());
 }
 
 bool IRSimilarityIdentifierWrapperPass::doInitialization(Module &M) {
-  IRSI.reset(new IRSimilarityIdentifier(M));
+  IRSI.reset(new IRSimilarityIdentifier());
   return false;
 }
 
 bool IRSimilarityIdentifierWrapperPass::doFinalization(Module &M) {
   IRSI.reset();
   return false;
 }
 
 bool IRSimilarityIdentifierWrapperPass::runOnModule(Module &M) {
   // All the real work is done in the constructor for the pass.
-  IRSI.reset(new IRSimilarityIdentifier(M));
+  IRSI->findSimilarity(M);
   return false;
 }
 
 AnalysisKey IRSimilarityAnalysis::Key;
 IRSimilarityIdentifier IRSimilarityAnalysis::run(Module &M,
                                                ModuleAnalysisManager &) {
 
-  return IRSimilarityIdentifier(M);
+  auto IRSI = IRSimilarityIdentifier();
+  IRSI.findSimilarity(M);
+  return IRSI;
 }
 
 PreservedAnalyses
 IRSimilarityAnalysisPrinterPass::run(Module &M, ModuleAnalysisManager &AM) {
   IRSimilarityIdentifier &IRSI = AM.getResult<IRSimilarityAnalysis>(M);
   Optional<SimilarityGroupList> &SimilarityCandidatesOpt = IRSI.getSimilarity();
 
   for (std::vector<IRSimilarityCandidate> &CandVec : *SimilarityCandidatesOpt) {