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[AMDGPU] Fix DPP combiner check for exec modification

Description

[AMDGPU] Fix DPP combiner check for exec modification

Summary:
r363675 changed the exec modification helper function, now called
execMayBeModifiedBeforeUse, so that if no UseMI is specified it checks
all instructions in the basic block, even beyond the last use. That
meant that the DPP combiner no longer worked in any basic block that
ended with a control flow instruction, and in particular it didn't work
on code sequences generated by the atomic optimizer.

Fix it by reinstating the old behaviour but in a new helper function
execMayBeModifiedBeforeAnyUse, and limiting the number of instructions
scanned.

Reviewers: arsenm, vpykhtin

Subscribers: kzhuravl, nemanjai, jvesely, wdng, nhaehnle, yaxunl, dstuttard, tpr, t-tye, hiraditya, kbarton, MaskRay, jfb, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D64393

Details

Committed
foadJul 12 2019, 8:59 AM
Differential Revision
D64393: [AMDGPU] Fix DPP combiner check for exec modification
Parents
rL365909: [clang-format][tests] Explicitly specify style in some tests
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