Re: [MUSL] microMIPS32R2 O32 port

[Rich Felker <dalias@libc.org>]

On Wed, Apr 12, 2017 at 09:25:35PM +0200, Szabolcs Nagy wrote:
> * Jaydeep Patil <Jaydeep.Patil@imgtec.com> [2017-04-12 11:54:10 +0000]:
> > Hi Rich,
> > 
> > We can reuse existing MIPS code for microMIPS. There are places where we read from $ra must be compiled for MIPS.
> > Please refer to https://github.com/JaydeepIMG/musl-1/tree/micromips32r2_v2 for modifications.
> > 
> 
> is micromips a different encoding for mips instructions
> that works on some cpus but not others?

Yes, it's something like thumb or thumb2 on arm, or the riscv
compressed isa. What I'm not clear on is whether there are
micromips-only cpu models that can't execute normal mips.

If so we probably need the ability to build musl as micromips, but as
long as cpus which support both support interworking (calls between
the two type of code in the same process) reasonably, I don't think
there's any reason to consider it a different subarch.

If not (that is, if all cpus that support micromips also support the
normal mips isa) then I fail to see why there's any need to compile
musl's asm files as micromips. They're not size or performance
bottlenecks.

Rich