[all-commits] [llvm/llvm-project] ac8a9f: [memprof] Undrift MemProfRecord (#120138)

[Kazu Hirata via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: ac8a9f8fffb605514056f53f12f1fba94ee933e9
      https://github.com/llvm/llvm-project/commit/ac8a9f8fffb605514056f53f12f1fba94ee933e9
  Author: Kazu Hirata <kazu at google.com>
  Date:   2024-12-18 (Wed, 18 Dec 2024)

  Changed paths:
    M llvm/lib/Transforms/Instrumentation/MemProfiler.cpp
    A llvm/test/Transforms/PGOProfile/memprof-undrift.test

  Log Message:
  -----------
  [memprof] Undrift MemProfRecord (#120138)

This patch undrifts source locations in MemProfRecord before readMemprof
starts the matching process.

The thoery of operation is as follows:

1. Collect the lists of direct calls, one from the IR and the other
   from the profile.

2. Compute the correspondence (called undrift map in the patch)
   between the two lists with longestCommonSequence.

3. Apply the undrift map just before readMemprof consumes
   MemProfRecord.

The new function gated by a flag that is off by default.



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