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[TargetLowering] Add DemandedElts mask to SimplifyDemandedBits (PR40000)
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Authored by RKSimon on Dec 17 2018, 7:58 AM.

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Summary

This is an initial patch to add the necessary support for a DemandedElts argument to SimplifyDemandedBits, more closely matching computeKnownBits and to help improve vector codegen.

I've added only a small amount of additions necessary to get at least one test to update - a lot more can be done but I'd like to add these methodically with proper test coverage, at the same time the hope is to slowly move some/all of SimplifyDemandedVectorElts into SimplifyDemandedBits as well.

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rL LLVM

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RKSimon created this revision.Dec 17 2018, 7:58 AM
andreadb accepted this revision.Dec 17 2018, 10:00 AM

LGTM. Thanks!

test/CodeGen/X86/combine-sdiv.ll
3052–3057 ↗(On Diff #178467)

Unrelated to your patch.

This could be simplified to:

vpsrlw $8, %xmm1, %xmm1
vpxor %xmm2, %xmm2, %xmm2
vpunpcklbw %xmm2, %xmm0, %xmm2
vpackuswb %xmm1, %xmm2, %xmm0
This revision is now accepted and ready to land.Dec 17 2018, 10:00 AM
This revision was automatically updated to reflect the committed changes.
jfb added a subscriber: jfb.Dec 17 2018, 11:07 AM
jfb added inline comments.
llvm/trunk/lib/CodeGen/SelectionDAG/TargetLowering.cpp
1901

This leaves VT unused. I've removed it in r349377.

RKSimon marked an inline comment as done.Dec 17 2018, 11:16 AM
RKSimon added inline comments.
llvm/trunk/lib/CodeGen/SelectionDAG/TargetLowering.cpp
1901

Thanks @jfb