[PATCH] D131478: AMDGPU: mbcnt allow for non-zero src1 for known-bits
Jay Foad via Phabricator via llvm-commits
llvm-commits at lists.llvm.org
Fri Aug 19 06:12:18 PDT 2022
foad added inline comments.
================
Comment at: llvm/lib/Target/AMDGPU/AMDGPUISelLowering.cpp:4606
+ // These return at most the (wavefront size - 1) + src1
+ // As long as src1 is an immediate we can calc known bits
+ KnownBits Src1Known = DAG.computeKnownBits(Op.getOperand(2), Depth + 1);
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Comment seems misleading since this can give useful results even when src1 is not an immediate.
Also you could make this slightly simpler and more accurate by constructing a KnownBits for 0..(wavefront size - 1) (i.e. the high 26 or 27 bits are known zero) and then calling computeForAddSub to combine it with the known bits of src1.
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D131478/new/
https://reviews.llvm.org/D131478
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