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On Fri, 6 Feb 2015, Matthew Fortune wrote:

> >  Native systems have <sys/asm.h> for such ABI dependencies, including
> > stuff to set up $gp.  Perhaps we could reuse these bits, the licence I
> > think allows us to.
> That's a good idea. Perhaps I should take that on as part of some cleanup
> of the MIPS backend in the next stage1. I'm looking to rework how the
> ISA_HAS logic works so perhaps there would be value in doing this mostly in
> a header that can also be used for assembly programmers. That would naturally
> mean we get all the other nice assembly macros available in the backend of
> GCC too.

 This consideration made me realise I've had a patch outstanding for some 
10 years to convert all the `BAL x' instructions there to `BLTZAL $0, x'.  
This has always been a good idea in case implementations recognised the 
special case and avoided involving branch prediction, and I believe it has 
become even more apparent with r6 calling it NAL.

 I'll see if I can submit it to glibc soon -- as you may have been aware 
10 years ago wasn't exactly the most friendly period in glibc maintenance 
and hence I wasn't very prompt with patch submissions.


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