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| author | Phoebe Wang <phoebe.wang@intel.com> | 2022-08-03 16:38:34 +0800 |
|---|---|---|
| committer | Phoebe Wang <phoebe.wang@intel.com> | 2022-08-03 17:09:36 +0800 |
| commit | c2066d19cda20d0e98b95da1493e6c3f26fd9618 (patch) | |
| tree | 879dd63f7e28d322455843ac2aeb1d71b9bfb654 /llvm/lib/ExecutionEngine/Interpreter/ExternalFunctions.cpp | |
| parent | 7ae5d00afaf39fae78e411cb44f665e1dc52b356 (diff) | |
| download | llvm-c2066d19cda20d0e98b95da1493e6c3f26fd9618.zip llvm-c2066d19cda20d0e98b95da1493e6c3f26fd9618.tar.gz llvm-c2066d19cda20d0e98b95da1493e6c3f26fd9618.tar.bz2 | |
[X86][MC] Always emit `rep` prefix for `bsf`
`BMI` new instruction `tzcnt` has better performance than `bsf` on new
processors. Its encoding has a mandatory prefix '0xf3' compared to
`bsf`. If we force emit `rep` prefix for `bsf`, we will gain better
performance when the same code run on new processors.
GCC has already done this way: https://c.godbolt.org/z/6xere6fs1
Fixes #34191
Reviewed By: skan
Differential Revision: https://reviews.llvm.org/D130956
Diffstat (limited to 'llvm/lib/ExecutionEngine/Interpreter/ExternalFunctions.cpp')
0 files changed, 0 insertions, 0 deletions