[all-commits] [llvm/llvm-project] 628fbb: [libc] Use nearest_integer instructions to improve...

[lntue via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 628fbbef81c5ac806e6dbf2bce18dd44980051b1
      https://github.com/llvm/llvm-project/commit/628fbbef81c5ac806e6dbf2bce18dd44980051b1
  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/expm1f.cpp

  Log Message:
  -----------
  [libc] Use nearest_integer instructions to improve expm1f performance.

Use nearest_integer instructions to improve expf performance.

Performance tests with CORE-MATH's perf tool:

Before the patch:
```
$ ./perf.sh expm1f
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   : 10.096
System LIBC reciprocal throughput : 44.036
LIBC reciprocal throughput        : 11.575

$ ./perf.sh expm1f --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   : 42.239
System LIBC latency : 122.815
LIBC latency        : 50.122
```
After the patch:
```
$ ./perf.sh expm1f
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   : 10.046
System LIBC reciprocal throughput : 43.899
LIBC reciprocal throughput        : 9.179

$ ./perf.sh expm1f --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   : 42.078
System LIBC latency : 120.488
LIBC latency        : 41.528
```

Reviewed By: zimmermann6

Differential Revision: https://reviews.llvm.org/D130502