[PATCH v2 03/10] i386: Use generic fmod
Adhemerval Zanella Netto
adhemerval.zanella@linaro.org
Thu Mar 28 14:11:50 GMT 2024
On 27/03/24 18:38, H.J. Lu wrote:
> On Wed, Mar 27, 2024 at 1:37 PM Adhemerval Zanella Netto
> <adhemerval.zanella@linaro.org> wrote:
>>
>>
>>
>> On 27/03/24 16:55, H.J. Lu wrote:
>>> On Wed, Mar 27, 2024 at 12:40 PM Adhemerval Zanella
>>> <adhemerval.zanella@linaro.org> wrote:
>>>>
>>>> The benchtest results shows a slight improvement (Ryzen 5900, gcc
>>>> 13.2.1):
>>>>
>>>> * sysdeps/i386/fpu/e_fmod.S:
>>>> "fmod": {
>>>> "subnormals": {
>>>> "duration": 3.68855e+09,
>>>> "iterations": 2.12608e+08,
>>>> "max": 62.012,
>>>> "min": 16.798,
>>>> "mean": 17.349
>>>> },
>>>> "normal": {
>>>> "duration": 3.88459e+09,
>>>> "iterations": 7.168e+06,
>>>> "max": 2879.12,
>>>> "min": 16.909,
>>>> "mean": 541.934
>>>> },
>>>> "close-exponents": {
>>>> "duration": 3.692e+09,
>>>> "iterations": 1.96608e+08,
>>>> "max": 66.452,
>>>> "min": 16.835,
>>>> "mean": 18.7785
>>>> }
>>>> }
>>>>
>>>> * generic
>>>> "fmod": {
>>>> "subnormals": {
>>>> "duration": 3.68645e+09,
>>>> "iterations": 2.2848e+08,
>>>> "max": 66.896,
>>>> "min": 15.91,
>>>> "mean": 16.1347
>>>> },
>>>> "normal": {
>>>> "duration": 4.1455e+09,
>>>> "iterations": 8.192e+06,
>>>> "max": 3376.18,
>>>> "min": 15.873,
>>>> "mean": 506.043
>>>> },
>>>> "close-exponents": {
>>>> "duration": 3.70197e+09,
>>>> "iterations": 2.08896e+08,
>>>> "max": 69.597,
>>>> "min": 15.947,
>>>> "mean": 17.7216
>>>> }
>>>> }
>>>> ---
>>>> sysdeps/i386/fpu/Versions | 4 ++++
>>>> sysdeps/i386/fpu/e_fmod.S | 18 ------------------
>>>> sysdeps/i386/fpu/e_fmod.c | 2 ++
>>>> sysdeps/i386/fpu/math_err.c | 1 -
>>>> sysdeps/i386/fpu/w_fmod_compat.c | 15 ---------------
>>>> sysdeps/ieee754/dbl-64/e_fmod.c | 5 ++++-
>>>> sysdeps/mach/hurd/i386/libm.abilist | 1 +
>>>> sysdeps/unix/sysv/linux/i386/libm.abilist | 1 +
>>>> 8 files changed, 12 insertions(+), 35 deletions(-)
>>>> delete mode 100644 sysdeps/i386/fpu/e_fmod.S
>>>> create mode 100644 sysdeps/i386/fpu/e_fmod.c
>>>> delete mode 100644 sysdeps/i386/fpu/math_err.c
>>>> delete mode 100644 sysdeps/i386/fpu/w_fmod_compat.c
>>>>
>>>> diff --git a/sysdeps/i386/fpu/Versions b/sysdeps/i386/fpu/Versions
>>>> index a2eec371f1..d37bc1eae6 100644
>>>> --- a/sysdeps/i386/fpu/Versions
>>>> +++ b/sysdeps/i386/fpu/Versions
>>>> @@ -3,4 +3,8 @@ libm {
>>>> # functions used in inline functions or macros
>>>> __expl; __expm1l;
>>>> }
>>>> + GLIBC_2.40 {
>>>> + # No SVID compatible error handling.
>>>> + fmod;
>>>> + }
>>>
>>> This changes the ABI. I assume that it fixes a real bug. Is there a bug
>>> report open for this?
>>>
>>
>> The new version is the way to provide the system without the SVID compat
>> support, which we for all ABIs but i386 on 2.38. For instance:
>>
>> find . -iname libm.abilist | xargs grep -w fmod
>> ./sysdeps/unix/sysv/linux/sparc/sparc32/libm.abilist:GLIBC_2.0 fmod F
>> ./sysdeps/unix/sysv/linux/sparc/sparc32/libm.abilist:GLIBC_2.38 fmod F
>> [...]
>>
>> For i386 specifically, the old SVID symbol will be kept as fmod@GLIBC_2.0.
>>
>
> Does it fix a run-time test which fails without the fix?
>
Not really, but it is one less assembly implementation in favor a generic one
(which also shows a slight improvement on recent chips) and it sync i386
with generic code (so less possible issues, such as the static lib in this
patchset).
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