Google Git
Sign in
llvm / llvm-project / lld / 7cc89695f580cea66ca961849dce958fbaa5e9a4
commit7cc89695f580cea66ca961849dce958fbaa5e9a4[log] [tgz]
authorShoaib Meenai <smeenai@fb.com>Fri Nov 12 16:07:07 2021 -0800
committerCopybara-Service <copybara-worker@google.com>Tue Nov 16 16:36:19 2021 -0800
treea7875543e2dd6941a81da200f715ff83218e7b67
parent09c2e2dd0bb19bf72364438d64ce1989f458aacc [diff]
[MachO] Shrink reloc from 32 bytes to 24 bytes

The `r_address` field of `relocation_info` is only 4 bytes, so our
offset field (which is the `r_address` field adjusted for subsection
splitting) also only needs to be 4 bytes. This reduces the structure
size from 32 bytes to 24 bytes.

Combined with https://reviews.llvm.org/D113813, this is a minor perf
improvement for linking an internal app, tested on two machines:

```
           smol-relocs     baseline        difference (95% CI)
sys_time   7.367 ± 0.138   7.543 ± 0.157   [  +0.9% ..   +3.8%]
user_time  21.843 ± 0.351  21.861 ± 0.450  [  -1.3% ..   +1.4%]
wall_time  20.301 ± 0.307  20.556 ± 0.324  [  +0.1% ..   +2.4%]
samples    16              16

           smol-relocs     baseline        difference (95% CI)
sys_time   2.923 ± 0.050   2.992 ± 0.018   [  +1.4% ..   +3.4%]
user_time  10.345 ± 0.039  10.448 ± 0.023  [  +0.8% ..   +1.2%]
wall_time  12.068 ± 0.071  12.229 ± 0.021  [  +1.0% ..   +1.7%]
samples    15              12
```

More importantly though, this change by itself reduces our maximum
resident set size by 220 MB (2.75%, from 7.85 GB to 7.64 GB) on the
first machine. On the second machine, it reduces it by 125 MB (1.94%,
from 6.31 GB to 6.19 GB).

Reviewed By: #lld-macho, int3

Differential Revision: https://reviews.llvm.org/D113818

GitOrigin-RevId: 93bf271f27439d133616815266b50db4a294e118
2 files changed
tree: a7875543e2dd6941a81da200f715ff83218e7b67
  1. cmake/
  2. COFF/
  3. Common/
  4. docs/
  5. ELF/
  6. include/
  7. lib/
  8. MachO/
  9. MinGW/
  10. test/
  11. tools/
  12. unittests/
  13. utils/
  14. wasm/
  15. .clang-format
  16. .clang-tidy
  17. .gitignore
  18. CMakeLists.txt
  19. CODE_OWNERS.TXT
  20. LICENSE.TXT
  21. README.md
README.md

LLVM Linker (lld)

This directory and its subdirectories contain source code for the LLVM Linker, a modular cross platform linker which is built as part of the LLVM compiler infrastructure project.

lld is open source software. You may freely distribute it under the terms of the license agreement found in LICENSE.txt.

Benchmarking

In order to make sure various developers can evaluate patches over the same tests, we create a collection of self contained programs.

It is hosted at https://s3-us-west-2.amazonaws.com/linker-tests/lld-speed-test.tar.xz

The current sha256 is 10eec685463d5a8bbf08d77f4ca96282161d396c65bd97dc99dbde644a31610f.