[all-commits] [llvm/llvm-project] 9fed48: [BOLT] Explicitly check for returns when extending...

[Amir Ayupov via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 9fed480f183d9cfa784228cd77b2c0a642fca697
      https://github.com/llvm/llvm-project/commit/9fed480f183d9cfa784228cd77b2c0a642fca697
  Author: Amir Ayupov <aaupov at fb.com>
  Date:   2025-06-17 (Tue, 17 Jun 2025)

  Changed paths:
    M bolt/include/bolt/Profile/DataAggregator.h
    M bolt/lib/Profile/DataAggregator.cpp
    M bolt/test/X86/callcont-fallthru.s

  Log Message:
  -----------
  [BOLT] Explicitly check for returns when extending call continuation profile (#143295)

Call continuation logic relies on assumptions about fall-through origin:
- the branch is external to the function,
- fall-through start is at the beginning of the block,
- the block is not an entry point or a landing pad.

Leverage trace information to explicitly check whether the origin is a
return instruction, and defer to checks above only in case of
DSO-external branch source.

This covers both regular and BAT cases, addressing call continuation
fall-through undercounting in the latter mode, which improves BAT
profile quality metrics. For example, for one large binary:
- CFG discontinuity 21.83% -> 0.00%,
- CFG flow imbalance 10.77%/100.00% -> 3.40%/13.82% (weighted/worst)
- CG flow imbalance 8.49% —> 8.49%.

Depends on #143289.

Test Plan: updated callcont-fallthru.s



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