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Re: mips instructions


ian@zembu.com (Ian Lance Taylor) writes:
>    Okay, I've been looking through the new mips32 and 64 isas.  I've found
>    a few instructions in opcodes/mips-opc.c that I can't find a description
>    for anywhere:
> 
>    mfc2
>    mfc3
>    mtc2
>    mtc3
> 
>    These are part of the original mips1 spec, but I can't find them in the
>    new spec anywhere.  Did I just miss the part where it said that all
>    original mips1 instructions were supported?
> 
> I have a vague recollection that MIPS took the bit definitions for
> these coprocessor instructions and defined them as new instructions.
> Take a look at the bit patterns for the new instructions, and see if
> they overlap with these.

That's true for some, especially for the cp3 instructions.  However,
MIPS32/MIPS64 really do define m.c2.  (presumably, the notion is, with
all of these cores coming out of the woodwork, it may well be
reasonable for people to define a cproprocessor 2.)


As far as I'm concerned, the cp3 instructions are good catch-alls for
the those forms for disassembly.  They shouldn't be used for assembly.



chris

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