[llvm-dev] LLVM LNT floating point performance tests on X86 - using the llvm-test-suite benchmarks

[Florian Hahn via llvm-dev]

> On May 19, 2021, at 17:08, Blower, Melanie I <melanie.blower at intel.com> wrote:
> 
> What I'm trying to do is to determine whether the patch I'm submitting is going to cause benchmarking problems that force the patch to be reverted--since that happened the last time I committed the patch (several months ago).


IIUC the problem with the patch was not runtime performance, but unexpected results causing some tests/benchmarks to fail.

I think you might need to select a CPU on X86 to cause the mis-compares. Below the commands I used to reproduce the failure of MultiSource/Applications/oggenc/oggenc. Note `-march=native`. Without that, the test passes. There are a couple of other failures as well.


> cmake -G Ninja \                
    -DCMAKE_C_COMPILER=/path/to/bin/clang \
    -DCMAKE_C_FLAGS="-O3 -march=native" -DCMAKE_CXX_FLAGS="-O3 -march=native" \
    Path/to/llvm-test-suite

> ninja MultiSource/Applications/oggenc/oggenc

> llvm-lit MultiSource/Applications/oggenc/
-- Testing: 1 tests, 1 workers --
FAIL: test-suite :: MultiSource/Applications/oggenc/oggenc.test (1 of 1)
********************
Failed Tests (1):
  test-suite :: MultiSource/Applications/oggenc/oggenc.test
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