From: Josh Poimboeuf <jpoimboe@redhat.com>
To: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
x86@kernel.org, Peter Zijlstra <peterz@infradead.org>,
Andy Lutomirski <luto@kernel.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] x86: use register variable to get stack pointer value
Date: Fri, 29 Sep 2017 10:38:28 -0500 [thread overview]
Message-ID: <20170929153828.rtxwllhsjgiaeaos@treble> (raw)
In-Reply-To: <20170929141537.29167-1-aryabinin@virtuozzo.com>
On Fri, Sep 29, 2017 at 05:15:36PM +0300, Andrey Ryabinin wrote:
> Currently we use current_stack_pointer() function to get the value
> of the stack pointer register. Since commit f5caf621ee35
> ("x86/asm: Fix inline asm call constraints for Clang") we have stack
> register variable declared. It can be used instead of current_stack_pointer()
> function which allows to optimize away some excessive "mov %rsp, %<dst>"
> instructions:
>
> -mov %rsp,%rdx
> -sub %rdx,%rax
> -cmp $0x3fff,%rax
> -ja ffffffff810722fd <ist_begin_non_atomic+0x2d>
>
> +sub %rsp,%rax
> +cmp $0x3fff,%rax
> +ja ffffffff810722fa <ist_begin_non_atomic+0x2a>
>
> Remove current_stack_pointer(), rename __asm_call_sp to current_stack_pointer
> and use it instead of removed function.
>
> Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com>
--
Josh
next prev parent reply other threads:[~2017-09-29 15:38 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-09-29 14:15 [PATCH] x86: use register variable to get stack pointer value Andrey Ryabinin
2017-09-29 15:38 ` Josh Poimboeuf [this message]
2017-09-29 18:37 ` Andy Lutomirski
2017-09-29 19:16 ` Josh Poimboeuf
2017-09-29 20:15 ` [tip:x86/urgent] x86/asm: Use " tip-bot for Andrey Ryabinin
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