[all-commits] [llvm/llvm-project] e06d6e: [SamplePGO] Handle FS discriminators in SampleProf...

[Krzysztof Pszeniczny via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: e06d6ed1ef081eb9858da8066a6036c5dde432eb
      https://github.com/llvm/llvm-project/commit/e06d6ed1ef081eb9858da8066a6036c5dde432eb
  Author: Krzysztof Pszeniczny <kpszeniczny at google.com>
  Date:   2024-05-02 (Thu, 02 May 2024)

  Changed paths:
    M llvm/lib/Transforms/IPO/SampleProfileMatcher.cpp
    M llvm/test/Transforms/SampleProfile/Inputs/non-probe-stale-profile-matching.prof
    M llvm/test/Transforms/SampleProfile/non-probe-stale-profile-matching.ll

  Log Message:
  -----------
  [SamplePGO] Handle FS discriminators in SampleProfileMatcher (#90858)

Currently the code uses FunctionSamples::getCallSiteIdentifier which
will sometimes incorrectly guess that FSAFDO discriminators are probe
based and will convert them incorrectly.

This change doesn't affect builds which don't use FSAFDO, it only fixes
sample profile matching with FS discriminators.

The test for this is manually updated to use discriminator value 15,
which is a perfectly valid base discriminator in the FS world, but
satisfies `isPseudoProbeDiscriminator`, so
`getBaseDiscriminatorFromDiscriminator` will incorrectly extract the
probe index from it.

Note: this change only affects how the base discriminators will be
extracted when doing stale profile matching in the IR-level sample
profile loader. It doesn't add stale profile matching to the MIR-level
FS profile loader pass.



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