[<prev] [next>] [<thread-prev] [day] [month] [year] [list]
Message-ID: <CAAhV-H6NnvSEtb81q5-TZLvK+cR+m8CxzadWmbYjNCTNSDOcRw@mail.gmail.com>
Date: Tue, 18 Jul 2023 16:18:30 +0800
From: Huacai Chen <chenhuacai@...nel.org>
To: WANG Xuerui <kernel@...0n.name>
Cc: Huacai Chen <chenhuacai@...ngson.cn>, loongarch@...ts.linux.dev,
linux-arch@...r.kernel.org, Xuefeng Li <lixuefeng@...ngson.cn>,
Guo Ren <guoren@...nel.org>,
Jiaxun Yang <jiaxun.yang@...goat.com>,
linux-kernel@...r.kernel.org, loongson-kernel@...ts.loongnix.cn
Subject: Re: [PATCH] LoongArch: Cleanup __builtin_constant_p() checking for cpu_has_*
On Tue, Jul 18, 2023 at 3:35 PM WANG Xuerui <kernel@...0n.name> wrote:
>
> On 2023/7/18 14:48, Huacai Chen wrote:
> > In current configuration, cpu_has_lsx and cpu_has_lasx are impossible
> > constants. So cleanup the __builtin_constant_p() checking to reduce the
>
> "cannot be constants"? "impossible constants" sounds like a compile-time
> error to me.
OK, thanks.
Huacai
>
> > complexity.
> >
> > Signed-off-by: Huacai Chen <chenhuacai@...ngson.cn>
> > ---
> > arch/loongarch/include/asm/fpu.h | 11 +++--------
> > 1 file changed, 3 insertions(+), 8 deletions(-)
> >
> > diff --git a/arch/loongarch/include/asm/fpu.h b/arch/loongarch/include/asm/fpu.h
> > index e4193d637f66..f02f4a0d0d64 100644
> > --- a/arch/loongarch/include/asm/fpu.h
> > +++ b/arch/loongarch/include/asm/fpu.h
> > @@ -218,12 +218,7 @@ static inline void restore_lsx(struct task_struct *t)
> >
> > static inline void init_lsx_upper(void)
> > {
> > - /*
> > - * Check cpu_has_lsx only if it's a constant. This will allow the
> > - * compiler to optimise out code for CPUs without LSX without adding
> > - * an extra redundant check for CPUs with LSX.
> > - */
> > - if (__builtin_constant_p(cpu_has_lsx) && !cpu_has_lsx)
> > + if (!cpu_has_lsx)
> > return;
> >
> > _init_lsx_upper();
> > @@ -294,7 +289,7 @@ static inline void restore_lasx_upper(struct task_struct *t) {}
> >
> > static inline int thread_lsx_context_live(void)
> > {
> > - if (__builtin_constant_p(cpu_has_lsx) && !cpu_has_lsx)
> > + if (!cpu_has_lsx)
> > return 0;
> >
> > return test_thread_flag(TIF_LSX_CTX_LIVE);
> > @@ -302,7 +297,7 @@ static inline int thread_lsx_context_live(void)
> >
> > static inline int thread_lasx_context_live(void)
> > {
> > - if (__builtin_constant_p(cpu_has_lasx) && !cpu_has_lasx)
> > + if (!cpu_has_lasx)
> > return 0;
> >
> > return test_thread_flag(TIF_LASX_CTX_LIVE);
>
> For the foreseeable future, the changes seem appropriate to me. FWIW the
> LoongArch kernel would stay as generic as possible so I expect the
> various predicates to almost never exist as constants.
>
> Reviewed-by: WANG Xuerui <git@...0n.name>
>
> --
> WANG "xen0n" Xuerui
>
> Linux/LoongArch mailing list: https://lore.kernel.org/loongarch/
>
Powered by blists - more mailing lists