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[X86] Add NEG to isUseDefConvertible.

Authored by craig.topper on Jul 12 2019, 10:52 AM.

Description

[X86] Add NEG to isUseDefConvertible.

We can use the C flag from NEG to detect that the input was zero.

Really we could probably use the Z flag too. But C matches what
we'd do for usubo 0, X.

Haven't found a test case for this due to the usubo formation
in CGP. But I verified if I comment out the CGP code this
transformation catches some of the same cases.

llvm-svn: 365929

Details

Committed
craig.topperJul 12 2019, 10:52 AM
Parents
rGce8c35a33dfb: [X86][AVX] Add PR34359 shuffle test case.
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