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[AMDGPU] Propagate dead flag during pre-RA exec mask optimizations
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Authored by critson on Jul 11 2020, 8:41 PM.

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Summary

Preserve SCC dead flags in SIOptimizeExecMaskingPreRA.
This helps with removing redundant s_andn2 instructions later.

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critson created this revision.Jul 11 2020, 8:41 PM
Herald added a project: Restricted Project. · View Herald TranscriptJul 11 2020, 8:41 PM
arsenm added inline comments.Jul 13 2020, 6:06 AM
llvm/lib/Target/AMDGPU/SIOptimizeExecMaskingPreRA.cpp
171–172

You know the exact 2 opcodes here, so you can just hardcode the scc index (which I think is just the last operand in both cases)

critson updated this revision to Diff 277457.Jul 13 2020, 9:17 AM

Hard code SCC operand number.

rampitec accepted this revision.Jul 13 2020, 9:51 AM
This revision is now accepted and ready to land.Jul 13 2020, 9:51 AM
This revision was automatically updated to reflect the committed changes.