[PATCH] D43079: [TTI CostModel] change default cost of FP ops to 1 (PR36280)

[Evgeny Astigeevich via Phabricator via llvm-commits]

eastig added a comment.

Hi Sanjay,

The patch caused regressions in the LLVM benchmarks and in Spec2k/Spec2k6 benchmarks on AArch64 Cortex-A53:

SingleSource/Benchmarks/Misc/matmul_f64_4x4:  49%
MultiSource/Benchmarks/TSVC/LoopRerolling-flt/LoopRerolling-flt: 5.32%
CFP2000/188.ammp/188.ammp: 3.58%
CFP2000/177.mesa/177.mesa: 2.48%
CFP2006/444.namd/444.namd: 2.49%

The regression of SingleSource/Benchmarks/Misc/matmul_f64_4x4 can also be seen on the public bot: http://lnt.llvm.org/db_default/v4/nts/90636 
It is 128.85%.

The main difference in generated code is FMUL(FP, scalar) instead of FMUL(SIMD, scalar):

  fmul d20, d16, d2

instead of

  fmul v17.2d, v1.2d, v5.2d

This also caused code size increase: 6.04% in SingleSource/Benchmarks/Misc/matmul_f64_4x4

I am working on a reproducer.

Thanks,
Evgeny Astigeevich


Repository:
  rL LLVM

https://reviews.llvm.org/D43079