[PATCH] D88215: Add llvm.loop.unroll.threshold metadata

[Tim Corringham via Phabricator via llvm-commits]

timcorringham created this revision.
Herald added subscribers: llvm-commits, kerbowa, zzheng, hiraditya, tpr, nhaehnle, jvesely, arsenm.
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timcorringham requested review of this revision.

Add new loop metadata llvm.loop.unroll.threshold to allow the initial target
specific unroll threshold value to be specified on a loop by loop basis.

The intention is to be able to to allow more nuanced hints, e.g. specifying a
low threshold value to indicate that a loop may be unrolled if cheap enough
rather than using the all or nothing llvm.loop.unroll.disable metadata.

This new metadata is used in setting the default threshold in the target
specific loop options, so only has any effect for targets that make use of
it - in this change only AMDGPU uses this metadata.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D88215

Files:
  llvm/docs/LangRef.rst
  llvm/lib/Target/AMDGPU/AMDGPUTargetTransformInfo.cpp
  llvm/test/Transforms/LoopUnroll/AMDGPU/unroll-threshold.ll

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