[llvm-branch-commits] [flang] [clang] [libcxx] [libc] [compiler-rt] [llvm] [RISCV] Support select optimization (PR #80124)

[Wang Pengcheng via llvm-branch-commits]

wangpc-pp wrote:

> > and the measurement data still stands for RISCV.
> 
> Please give the measurement data in this review or a direct link to it. I tried searching for it, and did not immediately find it.

It's in the Phabricator link (https://reviews.llvm.org/D138990): 

> The headline numbers are these for SPEC2017 on a Neoverse N1:
>
> 500.perlbench_r   -0.12%
> 502.gcc_r         0.02%
> 505.mcf_r         6.02%
> 520.omnetpp_r     0.32%
> 523.xalancbmk_r   0.20%
> 525.x264_r        0.02%
> 531.deepsjeng_r   0.00%
> 541.leela_r       -0.09%
> 548.exchange2_r   0.00%
> 557.xz_r          -0.20%
>
> Running benchmarks with a combination of the llvm-test-suite plus several versions of SPEC gave between a 0.2% and 0.4% geomean improvement depending on the core/run. The instruction count went down by 0.1% too.

The performance gain is related to core implementation. For RISCV, the subtarget feature `FeatureEnableSelectOptimize` can be appended to tune features if it's beneficial.

https://github.com/llvm/llvm-project/pull/80124