[all-commits] [llvm/llvm-project] f75973: [BOLT][AArch64] Add support for SPE brstack format...

[Ádám Kallai via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: f75973949b0e51eb4b3852c903d08bc72bf5d459
      https://github.com/llvm/llvm-project/commit/f75973949b0e51eb4b3852c903d08bc72bf5d459
  Author: Ádám Kallai <kadam at inf.u-szeged.hu>
  Date:   2025-06-20 (Fri, 20 Jun 2025)

  Changed paths:
    M bolt/include/bolt/Profile/DataAggregator.h
    M bolt/include/bolt/Utils/CommandLineOpts.h
    M bolt/lib/Profile/DataAggregator.cpp
    A bolt/test/perf2bolt/AArch64/perf2bolt-spe.test
    A bolt/test/perf2bolt/X86/perf2bolt-spe.test
    M bolt/tools/driver/llvm-bolt.cpp
    M bolt/unittests/Profile/CMakeLists.txt
    A bolt/unittests/Profile/PerfSpeEvents.cpp

  Log Message:
  -----------
  [BOLT][AArch64] Add support for SPE brstack format (#129231)

Since Linux 6.14, Perf gained the ability to report SPE branch events
using the `brstack` format, which matches the layout of LBR/BRBE.

This patch reuses the existing LBR parsing logic to support SPE.

Example SPE brstack format:
```bash
perf script -i perf.data -F pid,brstack --itrace=bl
```
```
  PID       FROM / TO / PREDICTED

16984  0x72e342e5f4/0x72e36192d0/M/-/-/11/RET/-
16984  0x72e7b8b3b4/0x72e7b8b3b8/PN/-/-/11/COND/-
16984  0x72e7b92b48/0x72e7b92b4c/PN/-/-/8/COND/-
16984  0x72eacc6b7c/0x760cc94b00/P/-/-/9/RET/-
16984  0x72e3f210fc/0x72e3f21068/P/-/-/4//-
16984  0x72e39b8c5c/0x72e3627b24/P/-/-/4//-
16984  0x72e7b89d20/0x72e7b92bbc/P/-/-/4/RET/-
```

SPE brstack flags can be two characters long: `PN` or `MN`:
- `P` = predicted branch
- `M` = mispredicted branch
- `N` = optionally appears when the branch is NOT-TAKEN
    - flag is relevant only to  conditional branches


Example of usage with BOLT:

1. Capture SPE branch events:
```bash
perf record -e 'arm_spe_0/branch_filter=1/u' -- binary
```

2. Convert profile for BOLT:
```bash
perf2bolt -p perf.data -o perf.fdata --spe binary
```

3. Run BOLT Optimization:
```bash
llvm-bolt binary -o binary.bolted --data   perf.fdata ...
```

A unit test verifies the parsing of the 'SPE brstack format'.

---------

Co-authored-by: Paschalis Mpeis <paschalis.mpeis at arm.com>



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