[PATCH] D39960: [InstCombine] In foldSelectOpOp reuse existing selects if present

[John Brawn via Phabricator via llvm-commits]

john.brawn created this revision.
Herald added a reviewer: dberlin.

Currently foldSelectOpOp only optimises selects where the operands have only one use, in order to avoid a proliferation of select instructions. If we can reuse an existing select then we can relax this constraint.

This kind of pattern can happen when GVN PRE phi translation introduces a phi then later both of the phis become selects.


Repository:
  rL LLVM

https://reviews.llvm.org/D39960

Files:
  lib/Transforms/InstCombine/InstCombineSelect.cpp
  test/Transforms/InstCombine/select-reuse.ll

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