[Clfs-support] 64 bit cross compile

[Koornstra, Reinoud]

Ok Thanks.
Ok, I'll make it BUILD64="-m64 -march=core2"
Core2 can also mean 32 bits, so I do think -m64 is still needed.
Sounds good to you?

-----Original Message-----
From: clfs-support-bounces at lists.cross-lfs.org [mailto:clfs-support-bounces at lists.cross-lfs.org] On Behalf Of Nicholai Vesterløkke
Sent: Thursday, March 19, 2009 2:18 AM
To: CLFS Support
Subject: Re: [Clfs-support] 64 bit cross compile

> "Koornstra, Reinoud" <koornstra at hp.com>
> I read in the gcc release notes:
Try 'info gcc' for the full manual

> "Tuning for Intel Core 2 processors is available via -mtune=core2 
> and -march=core2"
> 
> Is there any difference in setting -mtune and -march?
Yes,  mtune is only reordering instructions.
mach is generating code specific for the arch, and it also reorder 
instructions, that is why mach implies mtune.

> The BUILD64="-m64" is something that is advised on the clfs page for
> building for 64 bit.
m32/m64 is about the size on integer, float, etc.
 Since you are compiling for 64 bit, you should use m64, but I don't know 
if setting mach=core2 also implies m64.

> When building tools they start every time with: CC="${CC} ${BUILD64}"
> Hence I am considering to say BUILD64="-m64 -march=core2"
> Maybe this is already not necessary, in which case BUILD64="-m64 -
> march=core2 -mtune=core2"
> Would be totally useless and redundant?
Yes, IMHO

Regards
Nicholai
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