[all-commits] [llvm/llvm-project] 91ee67: [libc] Use nearest_integer instructions to improve...

[lntue via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 91ee67206289ec80c3c02f063040fa4638be0d63
      https://github.com/llvm/llvm-project/commit/91ee67206289ec80c3c02f063040fa4638be0d63
  Author: Tue Ly <lntue at google.com>
  Date:   2022-07-26 (Tue, 26 Jul 2022)

  Changed paths:
    M libc/docs/math.rst
    M libc/src/math/generic/CMakeLists.txt
    M libc/src/math/generic/expf.cpp

  Log Message:
  -----------
  [libc] Use nearest_integer instructions to improve expf performance.

Use nearest_integer instructions to improve expf performance.

Performance tests with CORE-MATH's perf tool:

Before the patch:
```
$ ./perf.sh expf
LIBC-location: /home/lnt/experiment/llvm-project/build/projects/libc/lib/libllvmlibc.a
GNU libc version: 2.31
GNU libc release: stable
CORE-MATH reciprocal throughput   : 9.860
System LIBC reciprocal throughput : 7.728
LIBC reciprocal throughput        : 12.363

$ ./perf.sh expf --latency
LIBC-location: /home/lnt/experiment/llvm-project/build/projects/libc/lib/libllvmlibc.a
GNU libc version: 2.31
GNU libc release: stable
CORE-MATH latency   : 42.802
System LIBC latency : 35.941
LIBC latency        : 49.808
```

After the patch:
```
$ ./perf.sh expf
LIBC-location: /home/lnt/experiment/llvm/llvm-project/build/projects/libc/lib/libllvmlibc.a
GNU libc version: 2.31
GNU libc release: stable
CORE-MATH reciprocal throughput   : 9.441
System LIBC reciprocal throughput : 7.382
LIBC reciprocal throughput        : 8.843

$ ./perf.sh expf --latency
LIBC-location: /home/lnt/experiment/llvm/llvm-project/build/projects/libc/lib/libllvmlibc.a
GNU libc version: 2.31
GNU libc release: stable
CORE-MATH latency   : 44.192
System LIBC latency : 37.693
LIBC latency        : 44.145
```

Reviewed By: zimmermann6

Differential Revision: https://reviews.llvm.org/D130498