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Re: X18 on AArch64


Am 07.07.2015 um 23:01 schrieb pinskia@gmail.com:
> What does the elf abi say about x18, I thought it was just another temp. If the target does not use it as a platform reg.  Note there are many assembly files which might use x18 also due to that. 
> 
> So this means you need wrapper functions when moving between the different abis. Nothing much can be done in gcc really. Please push this back to wine instead. 
> 
> Also I think windows had a bad choice of using x18 when there was a system register already for tls. 
> 
> Thanks,
> Andrew

Hi,
I guess i haven't explained the problem too good.
The problem already starts with Wines environment which includes things we can't do something about like the loader/dynamic linker...
Using wrapper functions in Wine is not feasible, that'd be a massive infrastructure change to huge and old codebase, would need a lot of work
and in the end won't get upstream.
What's needed is, is that distributions don't use x18 by default, so we need a good patch for that, hence i ask for a usable chain register (X8-X15?)
Truly it would be better to upstream that to gcc, but I don't have much hope left.
For the ELF ABI thing, i didn't found specific calling conventions or register usage description in it...
For the windows thing, good choices are not part of their development process ;)


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