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From: Andi Kleen <andi@firstfloor.org>
To: "H.J. Lu" <hjl.tools@gmail.com>
Cc: LKML <linux-kernel@vger.kernel.org>,
	"H. Peter Anvin" <hpa@zytor.com>,
	Andi Kleen <andi@firstfloor.org>
Subject: Re: [PATCH] Use -mskip-rax-setup if supported
Date: Thu, 16 Apr 2015 23:25:51 +0200	[thread overview]
Message-ID: <20150416212551.GY2366@two.firstfloor.org> (raw)
In-Reply-To: <CAMe9rOrfDo3MGaQc_s5crw3TrYhS8NtqeyRcUFiA0yAV8e9Nig@mail.gmail.com>

On Thu, Apr 16, 2015 at 02:23:44PM -0700, H.J. Lu wrote:
> GCC 5 added a compiler option, -mskip-rax-setup, for x86-64.  It skips
> setting up the RAX register when SSE is disabled and there are no
> variable arguments passed in vector registers.  Since kernel doesn't
> pass vector registers to functions with variable arguments, this option
> can be used to optimize the x86-64 kernel.  For kernel 3.17:
> 
>     text   data    bss    dec      hex   filename
> 11455921 2204048 5853184 19513153 129bf41 vmlinux #with -mskip-rax-setup
> 11480079 2204048 5853184 19537311 12a1d9f vmlinux

Patch looks good to me.

Reviewed-by: Andi Kleen <ak@linux.intel.com>

-Andi

  reply	other threads:[~2015-04-16 21:25 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-04-16 21:23 [PATCH] Use -mskip-rax-setup if supported H.J. Lu
2015-04-16 21:25 ` Andi Kleen [this message]
2015-04-25 17:26 ` Borislav Petkov

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