InstructionSimplify: Relanding r301766
Summary:
Re-applying r301766 with a fix to a typo and a regression test.
The log message for r301766 was:
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InstructionSimplify: Canonicalize shuffle operands. NFC-ish.
Summary:
Apply canonicalization rules:
1. Input vectors with no elements selected from can be replaced with undef.
2. If only one input vector is constant it shall be the second one.
This allows constant-folding to cover more ad-hoc simplifications that
were in place and avoid duplication for RHS and LHS checks.
There are more rules we may want to add in the future when we see a
justification. e.g. mask elements that select undef elements can be
replaced with undef.
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Reviewers: spatel, RKSimon
Reviewed By: spatel
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D32863
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@302373 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed