[PATCH] D21951: [LVI] Use DenseMap::find_as in LazyValueInfo.

[Justin Lebar via llvm-commits]

jlebar created this revision.
jlebar added a reviewer: reames.
jlebar added a subscriber: llvm-commits.

This lets us avoid creating and destroying a CallbackVH every time we
check the cache.

This is good for a 2% e2e speedup when compiling one of the large Eigen
tests at -O3.

FTR, I tried making the ValueCache hashtable one-level -- i.e., mapping
a pair (Value*, BasicBlock*) to a lattice value, and that didn't seem to
provide any additional improvement.  Saving a word in LVILatticeVal by
merging the Tag and Val fields also didn't yield a speedup.

http://reviews.llvm.org/D21951

Files:
  lib/Analysis/LazyValueInfo.cpp

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