Hi,

MIPS64 appears to be building much better now in trunk, with n64/o32 multilib.

You can likewise adapt the patches to just build either of those or o32.

Have fun!

  René

Sent abroad - http://ExactCODE.com Germany.

On Sep 23, 2010, at 21:19, Jan Rovins <[email protected]> wrote:

> On 9/23/2010 2:39 PM, René Rebe wrote:
>> Hi,
>> 
>> On Sep 23, 2010, at 20:13 , Jan Rovins wrote:
>> 
>>> On 9/23/2010 1:37 PM, Rene Rebe wrote:
>>>> Porting the MIPS bits in dietlibc to 64 bit may only take some hours of 
>>>> trial and error. In fact I may even do so the next days (donations welcome 
>>>> :-).
>>> I looked at that dietlibc code a while ago, and tried to do some things so 
>>> it would build for mips64, but I gave up because there was too much mips32 
>>> specific assembly code in there that would need porting, and my knowledge 
>>> of Mips64 assembly was not sufficient to do this in a reasonable amount of 
>>> time, If you can find a way to bypass those assembly code issues, or are 
>>> not daunted by coding at that level, perhaps a few hours will do it.
>> well, I'm doing such stuff for years.
>> 
>>>> You could mark dietlibc [R] - mips64 temporarily (in it's .desc).
>>> Thanks for the tip.
>>>> I have a local mips64 glibc fix that i am just test build to check 
>>>> regressions and hope to commit any minute.
>>> The glibc solution is at the heart of the mips64 building troubles, I was 
>>> never able to get multilib working, so I bailed out into building it either 
>>> as n64abi or n32abi. for embedded purposes, it may still be good to let the 
>>> user specify whether its multilib, single lib n64 or single lib n32.
>>> 
>>> In building off the trunk as it is right now, I am getting the o32 abi libs 
>>> in /lib and the n32 abi libs in /lib64.
>>> The question arises as to which libs really should be used where.  The o32 
>>> abi libs are the true old 32 bit libs which will allow the running of the 
>>> ancient mips32 binaries on a mips64 system, but the n32 abi libs are of 
>>> more interest to someone running on modern 64bit hardware, and wants to 
>>> maintain a 32 bit user space. the n32 abi relies on some 64bit hardware 
>>> features, and is not usable on 32bit hardware, but it is still a 32 bit 
>>> abi, not a full 64bit abi. I think n32 would be the most common choice for 
>>> a 32bit abi on current Mips technology. I think the true n64 abi should be 
>>> in /lib64. The question is:  does one library solution make sense for every 
>>> one using Mips64, or should we let them pick their own combos?
>> Personally I would set it up like powerpc64, or x86-64, that is default to 
>> the full 64bit binaries in lib64 and have fully backward compatible lib/ 
>> support to support running the vanilla 32bit binaries of the architecture, 
>> which for MIPS would mean o32.
> Yes that makes sense in respect to keeping the /lib setup consistent across 
> all the different architectures  supported by T2.
>> I see little benefit in supporting the n32 variant. Of course anyone is free 
>> to setup his target to build n32 if they want to gain the extra performance 
>> % digit, ... But as outlined I would default to reasonable choices, the 
>> efforts to keep them working are already high enough. The Linux kconfig has 
>> this:
>> 
>>           Select this option if you want to run n32 binaries.  These are
>>           64-bit binaries using 32-bit quantities for addressing and certain
>>           data that would normally be 64-bit.  They are used in special
>>           cases.
>> 
>>           If unsure, say N.
> Even though the kernel says "Say No", I think n32 will be of high intrest to 
> embedded developers, working on new Mips64 hardware.  Once you have the 
> fundamental multilib issues sorted out,  I will submit an other patch to 
> allow the use of n32 in some way that makes sense, and hopefully won't 
> involve too much effort to maintain.
> 
> Jan
>> So this would mean fixing trunk to built n64 binaries instead of n32 gcc is 
>> apparently (accidentally) defaulting to.
>> 
>>      René
>> 
> 

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