[all-commits] [llvm/llvm-project] 484319: [libc] Make expm1f correctly rounded when the targ...

[lntue via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 484319f4972850d6e9bb3d433042cb56806ba183
      https://github.com/llvm/llvm-project/commit/484319f4972850d6e9bb3d433042cb56806ba183
  Author: Tue Ly <lntue.h at gmail.com>
  Date:   2022-06-03 (Fri, 03 Jun 2022)

  Changed paths:
    M libc/src/math/generic/expm1f.cpp
    M libc/test/src/math/CMakeLists.txt
    M libc/test/src/math/exhaustive/CMakeLists.txt
    M libc/test/src/math/exhaustive/expm1f_test.cpp
    M libc/test/src/math/expm1f_test.cpp

  Log Message:
  -----------
  [libc] Make expm1f correctly rounded when the targets have no FMA instructions.

Add another exceptional value and fix the case when |x| is small.

Performance tests with CORE-MATH project scripts:
With FMA instructions on Ryzen 1700:
```
$ ./perf.sh expm1f
LIBC-location: /home/lnt/experiment/llvm/llvm-project/build/projects/libc/lib/libllvmlibc.a
CORE-MATH reciprocal throughput   : 15.362
System LIBC reciprocal throughput : 53.194
LIBC reciprocal throughput        : 14.595
$ ./perf.sh expm1f --latency
LIBC-location: /home/lnt/experiment/llvm/llvm-project/build/projects/libc/lib/libllvmlibc.a
CORE-MATH latency   : 57.755
System LIBC latency : 147.020
LIBC latency        : 60.269
```
Without FMA instructions:
```
$ ./perf.sh expm1f
LIBC-location: /home/lnt/experiment/llvm/llvm-project/build/projects/libc/lib/libllvmlibc.a
CORE-MATH reciprocal throughput   : 15.362
System LIBC reciprocal throughput : 53.300
LIBC reciprocal throughput        : 18.020
$ ./perf.sh expm1f --latency
LIBC-location: /home/lnt/experiment/llvm/llvm-project/build/projects/libc/lib/libllvmlibc.a
CORE-MATH latency   : 57.758
System LIBC latency : 147.025
LIBC latency        : 70.304
```

Reviewed By: michaelrj

Differential Revision: https://reviews.llvm.org/D123440