linux-kernel - Re: Why not build kernel with -O3

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Message-ID: <CACmZjJJd0t_fSQMATN=-LJwm683+tqR90sPPAaCUCvNJ+P8MoQ@mail.gmail.com>
Date:	Wed, 8 Apr 2015 21:19:11 +0800
From:	Pengfei Yuan <0xcoolypf@...il.com>
To:	Austin S Hemmelgarn <ahferroin7@...il.com>
Cc:	Mike Galbraith <umgwanakikbuti@...il.com>,
	linux-kernel@...r.kernel.org
Subject: Re: Why not build kernel with -O3

2015-04-08 20:06 GMT+08:00 Austin S Hemmelgarn <ahferroin7@...il.com>:
> I can't remember any off the top of my head, but it does say explicitly in
> the GCC manual to be careful with -O3.  IIRC, most of the issues relate to
> -O3 enabling -ffast-math (which tends to really mess with code that expects
> strict IEEE 754 compliance), so it may not be as much of an issue for kernel
> code.  You might look into some of the projects that use -O3 by default (I
> think most of the Mozilla so0ftware does these days, and I know that there
> are others, I just can't remember what right now).
>

I am afraid you are talking about -Ofast, not -O3.
See https://gcc.gnu.org/onlinedocs/gcc/Optimize-Options.html

Yuan
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