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git_commit commit e8f61801c6237e56b3d69190af7a7acfdcede1e8
Author: Christopher Di Bella <cjdb@google.com>
Date: Fri Sep 12 06:33:10 2025 -0700

[libcxx] adds size-based `__split_buffer` representation to unstable ABI (#139632)

**tl;dr** We can significantly improve the runtime performance of
`std::vector` by changing its representation from three pointers to one
pointer and two integers. This document explains the details of this
change, along with the justifications for making it. See the [RFC] for
more information.

`vector` depends on `__split_buffer` for inserting elements. Changing
`__split_buffer` to match `vector`'s representation simplifies the
model, as it eliminates the need to convert between two different
representations of a contiguous buffer in the same configuration of
libc++.

[RFC]: https://discourse.llvm.org/t/adding-a-size-based-vector-to-libc-s-unstable-abi/86306

---------

Co-authored-by: Jorge Gorbe Moya <jgorbe@google.com>
Filter

ldionne-old-macbook-results test results

Run Order Start Time Duration
Current 552339 2025-12-16T16:40:01 0:00:00
Previous 552313 2025-12-16T16:40:01 0:00:00
Baseline 485288 2025-12-16T16:40:01 0:00:00


Tests Summary

Status Group # # (B)
Performance Regressions 2 0
Performance Improvements 2 0
Added Tests 0 15
Unchanged Tests 71 60
Total Tests 75

Performance Regressions - execution_time Δ Previous Current σ Δ (B) σ (B)
707_ntest_r 1.29% 17.970 18.202 - 0.00% -
737_gmsh_r 1.06% 12.870 13.006 - 0.00% -

Performance Improvements - execution_time Δ Previous Current σ Δ (B) σ (B)
753_ns3_r -1.46% 10.549 10.395 - 0.00% -
710_omnetpp_r -1.04% 8.532 8.443 - 0.00% -

Added Tests - execution_time
706_stockfish_r
707_ntest_r
709_cactus_r
710_omnetpp_r
721_gcc_r
723_llvm_r
727_cppcheck_r
729_abc_r
731_astcenc_r
736_ocio_r
737_gmsh_r
748_flightdm_r
750_sealcrypto_r
753_ns3_r
766_femflow_r


Report Time: 0.10s
Name Current %
706_stockfish_r 22.146 -
707_ntest_r 18.202 1.29%
709_cactus_r 19.760 -
710_omnetpp_r 8.443 -1.04%
721_gcc_r 12.991 -
723_llvm_r 11.570 -
727_cppcheck_r 25.049 -
729_abc_r 18.830 -
731_astcenc_r 10.051 -
736_ocio_r 16.261 -
737_gmsh_r 13.006 1.06%
748_flightdm_r 8.893 -
750_sealcrypto_r 18.571 -
753_ns3_r 10.395 -1.46%
766_femflow_r 12.985 -
Geometric Mean 14.353 -