[all-commits] [llvm/llvm-project] f99ccf: [mlir] Add math polynomial approximation pass

[Eugene Zhulenev via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: f99ccf6516bdd5def4d3bc311330aec92f5cb99d
      https://github.com/llvm/llvm-project/commit/f99ccf6516bdd5def4d3bc311330aec92f5cb99d
  Author: Eugene Zhulenev <ezhulenev at google.com>
  Date:   2021-02-19 (Fri, 19 Feb 2021)

  Changed paths:
    M mlir/include/mlir/Dialect/Math/Transforms/Passes.h
    M mlir/lib/Dialect/Math/Transforms/CMakeLists.txt
    A mlir/lib/Dialect/Math/Transforms/PolynomialApproximation.cpp
    A mlir/test/Dialect/Math/polynomial-approximation.mlir
    M mlir/test/lib/Transforms/CMakeLists.txt
    A mlir/test/lib/Transforms/TestPolynomialApproximation.cpp
    A mlir/test/mlir-cpu-runner/math_polynomial_approx.mlir
    M mlir/tools/mlir-opt/mlir-opt.cpp

  Log Message:
  -----------
  [mlir] Add math polynomial approximation pass

This gives ~30x speedup compared to expanding Tanh into exp operations:

```
name                  old cpu/op  new cpu/op  delta
BM_mlir_Tanh_f32/10    253ns ± 3%    55ns ± 7%  -78.35%  (p=0.000 n=44+41)
BM_mlir_Tanh_f32/100  2.21µs ± 4%  0.14µs ± 8%  -93.85%  (p=0.000 n=48+49)
BM_mlir_Tanh_f32/1k   22.6µs ± 4%   0.7µs ± 5%  -96.68%  (p=0.000 n=32+42)
BM_mlir_Tanh_f32/10k   225µs ± 5%     7µs ± 6%  -96.88%  (p=0.000 n=49+55)

name                  old time/op             new time/op             delta
BM_mlir_Tanh_f32/10    259ns ± 1%               56ns ± 2%  -78.31%        (p=0.000 n=41+39)
BM_mlir_Tanh_f32/100  2.27µs ± 1%             0.14µs ± 5%  -93.89%        (p=0.000 n=46+49)
BM_mlir_Tanh_f32/1k   22.9µs ± 1%              0.8µs ± 4%  -96.67%        (p=0.000 n=30+42)
BM_mlir_Tanh_f32/10k   230µs ± 0%                7µs ± 3%  -96.88%        (p=0.000 n=37+55)
```

This approximations is based on Eigen::generic_fast_tanh function

Reviewed By: mehdi_amini

Differential Revision: https://reviews.llvm.org/D96739