linux-kernel - Re: X32 psABI status update

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Date:	Wed, 16 Mar 2011 22:21:16 -0700
From:	"H.J. Lu" <hjl.tools@...il.com>
To:	Mike Frysinger <vapier@...too.org>
Cc:	libc-alpha@...rceware.org, GCC Development <gcc@....gnu.org>,
	LKML <linux-kernel@...r.kernel.org>, x32-abi@...glegroups.com
Subject: Re: X32 psABI status update

On Wed, Mar 16, 2011 at 7:57 PM, Mike Frysinger <vapier@...too.org> wrote:
> On Wednesday, March 16, 2011 08:39:57 H.J. Lu wrote:
>> On Tue, Mar 15, 2011 at 10:24 PM, Mike Frysinger wrote:
>> > so we get back to my original e-mail:
>> >        are you getting a unique host tuple for this ?  or are you
>> > extending x86_64-linux-gnu ?  so the only way of knowing which ABI is to
>> > check for the output of the compiler+compiler flags ?
>>
>> As I said, the target is x86_64- linux-gnu and you just add -mx32 to
>> CFLAGS. The x86_64- linux-gnu binutils and GCC support  x32.
>
> ok, took long enough, but that answers most things.  your usage of "x32-"
> prefixed binaries in the documentation seems to imply a lot more than the fact
> you just picked those locally to avoid system collisions.  this isnt a wiki
> page, otherwise i'd clean things up for you.

Any suggestion how to create a wiki page for x32?

> in looking at the gcc files, it doesnt seem like there's any defines setup to
> declare x32 directly.  instead, you'd have to do something like:
> #ifdef __x86_64__
> # if __SIZEOF_LONG__ == 8
> /* x86_64 */
> # else
> /* x32 */
> # endif
> #endif
>
> any plans on adding an __x32__ (or whatever) cpp symbol to keep people from
> coming up with their own special/broken crap ?  or are there some already that
> i'm not seeing ?

The idea is in most cases, you only need to check __x86_64__ since x32 and
x86-64 are very close.  In some cases, x32 is very different from x86_64, like
assembly codes on long and pointer, you can check __x86_64__ and __LP64__.
In glibc, I used a different approach by using macros REG_RAX, .., MOV_LP,
ADD_LP, SUB_LP and CMP_LP in assembly codes.

I added a simple howto for x32 compiling to

https://sites.google.com/site/x32abi/

Thanks.

-- 
H.J.
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