Re: [PATCH v2 0/4] LoongArch: Add some floating-point operations

[tangxiaolin <tangxiaolin@loongson.cn>]

Thanks a lot. These patches look very good,  honestly I have nothing to add.

For lrint and llrint, If you ask my suggestion, I would say adding  
USE_LRINTL_BUILTIN and USE_LRINTF128_BUILTIN (with zero value) is better 
for consistency with other functions like ceil.

I did an experiment, 'scalbn' is indeed not easy to deal with, and I don't have a better idea so far.I tend to add inline assembler for this function instead of builtin if you don't have a better idea.

What do you think?

在 2022/11/14 下午4:05, Xi Ruoyao 写道:
> On Mon, 2022-11-14 at 10:41 +0800, tangxiaolin wrote:
>> How about I do this work on Glibc?
> [Moving the discussion to libc-alpha.]
>
> Go for it.  I'm attaching my draft patches and you can use them as a
> starting point.
>
> rint change is trivial.  for lrint and llrint I'm not sure if we should
> add USE_LRINTL_BUILTIN and USE_LRINTF128_BUILTIN (with zero value) as
> well.  Likewise for logb.
>
> scalbn is a little complicated: I'd prefer to expand M_SCALBN to
> __builtin_scalbn directly instead of calling __scalbn (to avoid the
> overhead calling a function with only two instructions) but it seems not
> easy: some files calling M_SCALBN are compiled with -fmath-errno, with
> which the compiler will refuse to expand __builtin_scalbn.
>
>> 在 2022/11/12 下午3:08, Xi Ruoyao 写道:
>>> On Wed, 2022-11-09 at 21:53 +0800, Xi Ruoyao wrote:
>>>> These patches allow to expand the following builtins to floating
>>>> point
>>>> instructions for LoongArch:
>>>>
>>>> - __builtin_rint{,f}
>>>> - __builtin_{l,ll}rint{,f}
>>>> - __builtin_{l,ll}floor{,f}
>>>> - __builtin_{l,ll}ceil{,f}
>>>> - __builtin_scalb{n,ln}{,f}
>>>> - __builtin_logb{,f}
>>>>
>>>> Bootstrapped and regtested on loongarch64-linux-gnu.  And a
>>>> modified
>>>> Glibc using the builtins for rint{,f}, {l,ll}rint{,f}, and
>>>> logb{,f}
>>>> also survived Glibc test suite.
>>>>
>>>> Please review ASAP because GCC 13 stage 1 will end on Nov. 13th.
>>>>
>>>> v1 -> v2: Only use ftint{rm,rp} instructions if floor and ceil are
>>>> allowed to raise inexact exception.
>>>>
>>>> Xi Ruoyao (4):
>>>>     LoongArch: Rename frint_<fmt> to rint<mode>2
>>>>     LoongArch: Add ftint{,rm,rp}.{w,l}.{s,d} instructions
>>>>     LoongArch: Add fscaleb.{s,d} instructions as ldexp{sf,df}3
>>>>     LoongArch: Add flogb.{s,d} instructions and expand logb{sf,df}2
>>>>
>>>>    gcc/config/loongarch/loongarch.md             | 95
>>>> ++++++++++++++++++-
>>>>    gcc/testsuite/gcc.target/loongarch/flogb.c    | 18 ++++
>>>>    gcc/testsuite/gcc.target/loongarch/frint.c    | 16 ++++
>>>>    gcc/testsuite/gcc.target/loongarch/fscaleb.c  | 48 ++++++++++
>>>>    .../gcc.target/loongarch/ftint-no-inexact.c   | 44 +++++++++
>>>>    gcc/testsuite/gcc.target/loongarch/ftint.c    | 44 +++++++++
>>>>    6 files changed, 261 insertions(+), 4 deletions(-)
>>>>    create mode 100644 gcc/testsuite/gcc.target/loongarch/flogb.c
>>>>    create mode 100644 gcc/testsuite/gcc.target/loongarch/frint.c
>>>>    create mode 100644 gcc/testsuite/gcc.target/loongarch/fscaleb.c
>>>>    create mode 100644 gcc/testsuite/gcc.target/loongarch/ftint-no-
>>>> inexact.c
>>>>    create mode 100644 gcc/testsuite/gcc.target/loongarch/ftint.c
>>>>
>>> Pushed r13-3922.
>>>
>>> I'll be busy in the following week.  Will do the work on Glibc side
>>> after Nov. 20.
>>>