[all-commits] [llvm/llvm-project] d89914: [memprof] Add Version2 of IndexedMemProfRecord ser...

[Kazu Hirata via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: d89914f30bc7c180fe349a5aa0f03438ae6c20a4
      https://github.com/llvm/llvm-project/commit/d89914f30bc7c180fe349a5aa0f03438ae6c20a4
  Author: Kazu Hirata <kazu at google.com>
  Date:   2024-04-03 (Wed, 03 Apr 2024)

  Changed paths:
    M llvm/include/llvm/ProfileData/MemProf.h
    M llvm/lib/ProfileData/InstrProfReader.cpp
    M llvm/lib/ProfileData/InstrProfWriter.cpp
    M llvm/lib/ProfileData/MemProf.cpp
    M llvm/unittests/ProfileData/MemProfTest.cpp

  Log Message:
  -----------
  [memprof] Add Version2 of IndexedMemProfRecord serialization (#87455)

I'm currently developing a new version of the indexed memprof format
where we deduplicate call stacks in IndexedAllocationInfo::CallStack
and IndexedMemProfRecord::CallSites.  We refer to call stacks with
integer IDs, namely CallStackId, just as we refer to Frame with
FrameId.  The deduplication will cut down the profile file size by 80%
in a large memprof file of mine.

As a step toward the goal, this patch teaches
IndexedMemProfRecord::{serialize,deserialize} to speak Version2.  A
subsequent patch will add Version2 support to llvm-profdata.

The essense of the patch is to replace the serialization of a call
stack, a vector of FrameIDs, with that of a CallStackId.  That is:

  const IndexedAllocationInfo &N = ...;
  ...
  LE.write<uint64_t>(N.CallStack.size());
  for (const FrameId &Id : N.CallStack)
    LE.write<FrameId>(Id);

becomes:

  LE.write<CallStackId>(N.CSId);



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