[PATCH] D48662: [InstCombine] reverse canonicalization of binops to allow more shuffle folding

[Sanjay Patel via Phabricator via llvm-commits]

spatel created this revision.
spatel added reviewers: RKSimon, lebedev.ri, efriedma.
Herald added a subscriber: mcrosier.

This is a superset of https://reviews.llvm.org/D48485 that includes transforming an 'or' back into an 'add' in addition to the shl+mul case shown there.

Here, we need value tracking to determine that the 'or' can be reversed into an 'add'.

IIUC, there are only a handful of opcodes where we'll try this. To repeat from the other review - I think we're distinguishing this pattern from the scenario where we have eliminated a binop completely and need to materialize a 'ghost' op with an identity constant.


https://reviews.llvm.org/D48662

Files:
  lib/Transforms/InstCombine/InstCombineVectorOps.cpp
  test/Transforms/InstCombine/shuffle_select.ll

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