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| author | Fangrui Song <i@maskray.me> | 2024-06-19 10:30:13 -0700 |
|---|---|---|
| committer | GitHub <noreply@github.com> | 2024-06-19 10:30:13 -0700 |
| commit | fb17bbce80cf76ce1a31eff463f451f626bc36b5 (patch) | |
| tree | ddcc0415c422b0ed2b56670526f5514f8459c938 /llvm/lib/IR/Module.cpp | |
| parent | 58d7a6e0e6361871442df956bb88798ce602b09d (diff) | |
| download | llvm-fb17bbce80cf76ce1a31eff463f451f626bc36b5.zip llvm-fb17bbce80cf76ce1a31eff463f451f626bc36b5.tar.gz llvm-fb17bbce80cf76ce1a31eff463f451f626bc36b5.tar.bz2 | |
[DenseMap] Update combineHashValue
`combineHashValue` is a custom bit mixer from 2008
(5fc8ab6d187aefbf1d2cbd36e191e675b14db8f6) used for std::pair and
std::tuple. It has a long dependency chain and slow. Replace it with
a simply multiply-xorshift style hash using a constant from
splitmix64[1]. abseil-cpp and carbon also use this style, but with
uint128 to probably get a lower avalanche bias. We don't use uint128 for
MSVC portability.
Measured time to compute [0,1000000000) values on an i7-11850H:
* old: 1.163s
* new: 0.427s
[1]: https://jonkagstrom.com/tuning-bit-mixers/index.html
Pull Request: https://github.com/llvm/llvm-project/pull/95970
Diffstat (limited to 'llvm/lib/IR/Module.cpp')
0 files changed, 0 insertions, 0 deletions