Date: Wed, 12 Apr 2017 14:47:20 -0700 From: Andre McCurdy <armccurdy@...il.com> To: musl@...ts.openwall.com Cc: Jaydeep Patil <Jaydeep.Patil@...tec.com> Subject: Re: microMIPS32R2 O32 port On Wed, Apr 12, 2017 at 1:27 PM, Rich Felker <dalias@...c.org> wrote: > On Wed, Apr 12, 2017 at 09:25:35PM +0200, Szabolcs Nagy wrote: >> * Jaydeep Patil <Jaydeep.Patil@...tec.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. According to: https://imagination-technologies-cloudfront-assets.s3.amazonaws.com/documentation/MIPS_Architecture_microMIPS32_InstructionSet_AFP_P_MD00582_06.04.pdf "microMIPS is also an alternative to the MIPS® instruction encoding and can be implemented in parallel or stand-alone." "If only one ISA mode exists (either MIPS or microMIPS) then this mode switch mechanism does not exist" > 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
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