[NewGVN] We don't use postdom anymore

[davide]

Summary

Unless I'm horribly mistaken (actually, since I started working on NewGVN I've never seen it using PostDom, as in Analysis/PostDominators.cpp).

[• dberlin]

You are correct.
There are also a few old comments referring to equality propagation in various places, which we don't do yet here either :)

llvm/trunk/lib/Transforms/Scalar/NewGVN.cpp

NewGVN() : FunctionPass(ID) {
     initializeNewGVNPass(*PassRegistry::getPassRegistry());
   }
 
   bool runOnFunction(Function &F) override;
   bool runGVN(Function &F, DominatorTree *DT, AssumptionCache *AC,
               TargetLibraryInfo *TLI, AliasAnalysis *AA, MemorySSA *MSSA);
 
 private:
-  // This transformation requires dominator postdominator info.
   void getAnalysisUsage(AnalysisUsage &AU) const override {
     AU.addRequired<AssumptionCacheTracker>();
     AU.addRequired<DominatorTreeWrapperPass>();
     AU.addRequired<TargetLibraryInfoWrapperPass>();
     AU.addRequired<MemorySSAWrapperPass>();
     AU.addRequired<AAResultsWrapperPass>();
 
     AU.addPreserved<DominatorTreeWrapperPass>();