Messages in this thread | | | Date | Wed, 8 Sep 2010 23:14:11 +0100 | Subject | Re: Promoting Crusoe and Geode Processors to i686 Status | From | Nick Lowe <> |
| |
Hi,
Here goes...
-mtune tunes the binary for given architecture. This as opposed to defining the baseline architecture, and thus available instruction set, which -march does.
I believe that -mtune is predominantly used for instruction scheduling. GCC uses it when it's reordering instructions to optimise for specific micro-architecture over others.
With -mtune=i686, I am of the opinion that you instruct the compiler, and give it the opportunity, to deliver a better ordering of the instructions. In this case, better ordering for i686 than you would get with -mtune=generic32.
I'm probably wrong somehow, it's probably marginal, and I'll concede to your infinitely better knowledge any day! That's why I phrased it as a question! :)
Cheers,
Nick
On Wed, Sep 8, 2010 at 10:39 PM, H. Peter Anvin <hpa@zytor.com> wrote: > On 09/07/2010 05:27 PM, Nick Lowe wrote: >> >> 2) Should there be the special case that forces the suboptimal >> -mtune=generic32 to work around the binutils NOPL bug or, as I think, >> should people just update to a sane binutils version? (It's a special >> case triggered where CONFIG_X86_P6_NOP is not set.) >> > > What's suboptimal about it? > > -hpa > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |