linux-kernel - Re: [Suggestion] [x86]: Compiler Option Os is better on latest x86

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Date:	Thu, 24 Jan 2013 09:35:29 -0600
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Borislav Petkov <bp@...e.de>, Ingo Molnar <mingo@...nel.org>,
	ling.ma.program@...il.com, mingo@...hat.com, tglx@...utronix.de,
	linux-kernel@...r.kernel.org, Ma Ling <ling.ml@...pay.com>
Subject: Re: [Suggestion] [x86]: Compiler Option Os is better on latest x86

On 01/24/2013 09:25 AM, Borislav Petkov wrote:
> On Thu, Jan 24, 2013 at 08:56:26AM -0600, H. Peter Anvin wrote:
>> There has been occasional talk about a -Ok(ernel) option to gcc, but
>> that would require someone to go through gcc and figure out what bits
>> makes sense and which don't...
> 
> Yep, such an option has a great potential for us and, if done right,
> would be very cool. It could probably be taught to insert HWEIGHT,
> RDRAND, CLFLUSH and whatever other insns we have the inline asm versions
> for... and query CPUID before that... uuh, nice stuff.
> 
> The alternative would be to fork gcc and call it kcc...
> 
> /me runs away pretty quickly without even turning back :-)
> 

I don't expect we'll be teaching gcc about the alternatives mechanism.
-Ok was about optimization, basically a "sane -Os".

	-hpa

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