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RE: Macro expansion on MIPS

>>> Is there a way to disable macro expansion on MIPS? More specific the 
>>> replacement of 64bit instructions into two 32bit ones.
>>> ...
>> From: []
>> Have you considered O64?  It's like O32 except with 64 bit registers 
>> and 64-bit operations.  It gives you much of the benefits you'd get 
>> from N32 with a lot less effort.  We've used it for years with 
>> excellent results.
>We have a very customized VxWorks 5 and a lot of in-house software.
> It would be too much work to switch entirely to a new ABI in a few 
>weeks/months. So I really want to get everything building and running 
>with the new toolchain. 64bit pointers are too much overhead for us, 
>so we will likely go to N32 in the near future. But first things first,
> and that's a new toolchain. 

O64, in spite of its name, uses 32 bit pointers.  The best way to understand it is "O32 with 64 bit registers".  So all pointers remain the same, the register usage is the same (four A registers for argument passing, for example), and most importantly, the ABICALLS mechanism is the same as O32.

>From past experience (working on millions of lines of code, much of it custom), it is indeed possible to do this in a few weeks.  It involves a few trivial changes to a small number of assembly files, plus recompiling everything.  The main effort is (a) building the O64 multilibs of the toolchain, (b) testing.

And by the way, your code will then be faster and smaller.  All for probably less effort than manually fixing up 64 bit assembly operations.


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