[fpc-devel] Bounty for MIPS

[Mark Morgan Lloyd]

Pierre Free Pascal wrote:
>>> Questions:
>>>   It seems like GNU AS has a different MUPS syntax as traditional MIPS
>>> assembler, but I didn't find precise information about this;
>>> Could someone give me some pointers?
>> I don't think I've got access to any MIPS as other than gas, but if
>> necessary I could put the disc that came with my problematic SGI system
>> into a PC server and investigate whether it has any development software
>> (it's a fairly minimal IRIX).
>>
>> What differences did you have in mind?
> Take a look at trunk/rtl/linux/mips/prt0.as
> This file is non-functional, but it seems to contain some disassembly
> of a start code (probably from some other compiler...)
> This disassembly syntax seems quite different from
> the other assembler code (below in same file and in other sources
> seem more like gnu as generated by GCC if using --save-temps.
> 
> Well, at least register naming is different (using a4 or s7 instead of $sp
> and $X
> where X is a number...)

I agree that there's something odd with that, but I was working against 
the rtl/linux/mipsel one. Also:

"Note that register names are 0, 1 etc. with $ as a mandatory sigil, and 
that register assignment is right-to-left; versions of GNU as from 2.18 
onwards also support symbolic register names a0, a1 etc. There is a 
delay slot after branch etc. instructions." 
http://wiki.lazarus.freepascal.org/Assembler_and_ABI_Resources#MIPS

I forget what version gas is currently at, but that's a comparatively 
recent change so I think there's a good argument either for converting 
back to the numeric form, or having an include file with symbolic 
definitions available for older versions.

> Anyway, maybe the content of rtl/mips/prt0.as isn't really MIPS assembler at
> all :(

Somebody's working notes by the looks of it.

Can anybody say whether David Zhang did his port in isolation, or was he 
in discussion with core developers?

-- 
Mark Morgan Lloyd
markMLl .AT. telemetry.co .DOT. uk

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