Message-ID: <4ACCB52D.3020104@redhat.com>
Date: Wed, 07 Oct 2009 08:35:09 -0700
From: Richard Henderson <rth@redhat.com>
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To: Roland McGrath <roland@redhat.com>
CC: Jason Baron <jbaron@redhat.com>, linux-kernel@vger.kernel.org,
       mingo@elte.hu, mathieu.desnoyers@polymtl.ca, tglx@linutronix.de,
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Subject: Re: [PATCH 0/4] jump label patches
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On 10/06/2009 05:14 PM, Roland McGrath wrote:
> Kernel builds usually use -Os.  Is there anything else we can do now (4.4)
> to influence this placement (while keeping the unlikely target block inside
> a scope, i.e. macro, with the asm goto)?

I think -Os includes -freorder-blocks as well.

> 	      if (0) yes: maybe = 1;

Anything with "if (0)" in it (even with __builtin_expect) is going to be 
folded away too early to be useful.

I can't think of any way to manipulate block placement from the source 
level at this time that doesn't add more code along the fast path, 
obviating the asm goto.


r~
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