[PATCH] D20983: [InstCombine] scalarizePHI should not assume the code it sees has been CSE'd

[Michael Kuperstein via llvm-commits]

mkuper created this revision.
mkuper added reviewers: majnemer, spatel.
mkuper added a subscriber: llvm-commits.

scalarizePHI only looks for phis that have exactly two users - the "latch" use, and an extract. Unfortunately, we can not assume such extracts have been CSEd, since InstCombine itself may create an extract which is a duplicate of an existing one. This extends it to handle several extracts from the same index.

This hopefully fixes the performance regression in PR27988.

http://reviews.llvm.org/D20983

Files:
  lib/Transforms/InstCombine/InstCombineVectorOps.cpp
  test/Transforms/InstCombine/vec_phi_extract.ll
  test/Transforms/LoopVectorize/PowerPC/vsx-tsvc-s173.ll

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