[all-commits] [llvm/llvm-project] d883a4: [libc] Implement sinf function that is correctly r...

[lntue via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: d883a4ad02d867e7037bd4ec342016c402484148
      https://github.com/llvm/llvm-project/commit/d883a4ad02d867e7037bd4ec342016c402484148
  Author: Tue Ly <lntue.h at gmail.com>
  Date:   2022-07-22 (Fri, 22 Jul 2022)

  Changed paths:
    M libc/cmake/modules/LLVMLibCObjectRules.cmake
    M libc/docs/math.rst
    M libc/src/__support/FPUtil/CMakeLists.txt
    A libc/src/__support/FPUtil/except_value_utils.h
    M libc/src/math/generic/CMakeLists.txt
    A libc/src/math/generic/range_reduction.h
    A libc/src/math/generic/range_reduction_fma.h
    M libc/src/math/generic/sinf.cpp
    M libc/test/src/math/exhaustive/CMakeLists.txt
    M libc/test/src/math/exhaustive/sinf_test.cpp
    M libc/test/src/math/sinf_test.cpp
    M utils/bazel/llvm-project-overlay/libc/BUILD.bazel

  Log Message:
  -----------
  [libc] Implement sinf function that is correctly rounded to all rounding modes.

Implement sinf function that is correctly rounded to all rounding modes.

- We use a simple range reduction for `pi/16 < |x|` :
    Let `k = round(x / pi)` and `y = (x/pi) - k`.
    So `k` is an integer and `-0.5 <= y <= 0.5`.
Then
```
sin(x) = sin(y*pi + k*pi)
          = (-1)^(k & 1) * sin(y*pi)
          ~ (-1)^(k & 1) * y * P(y^2)
```
    where `y*P(y^2)` is a degree-15 minimax polynomial generated by Sollya with:
```
> P = fpminimax(sin(x*pi)/x, [|0, 2, 4, 6, 8, 10, 12, 14|], [|D...|], [0, 0.5]);
```

- Performance benchmark using perf tool from CORE-MATH project
(https://gitlab.inria.fr/core-math/core-math/-/tree/master) on Ryzen 1700:
Before this patch (not correctly rounded):
```
$ CORE_MATH_PERF_MODE="rdtsc" ./perf.sh sinf
CORE-MATH reciprocal throughput   : 17.892
System LIBC reciprocal throughput : 25.559
LIBC reciprocal throughput        : 29.381
```
After this patch (correctly rounded):
```
$ CORE_MATH_PERF_MODE="rdtsc" ./perf.sh sinf
CORE-MATH reciprocal throughput   : 17.896
System LIBC reciprocal throughput : 25.740

LIBC reciprocal throughput        : 27.872
LIBC reciprocal throughput        : 20.012     (with `-msse4.2` flag)
LIBC reciprocal throughput        : 14.244     (with `-mfma` flag)
```

Reviewed By: zimmermann6

Differential Revision: https://reviews.llvm.org/D123154