Date: Thu, 13 Apr 2017 04:29:10 +0000 From: Jaydeep Patil <Jaydeep.Patil@...tec.com> To: Andre McCurdy <armccurdy@...il.com>, "musl@...ts.openwall.com" <musl@...ts.openwall.com> Subject: RE: microMIPS32R2 O32 port Hi, With this branch (micromips32r2_v2) we are supporting microMIPS cores that co-exist with MIPS. The MUSL library must be built with -minterlink-compressed option as there are couple of hand-written MIPS only functions. For microMIPS only cores we will create a different subarch. Thanks, Jaydeep >-----Original Message----- >From: Andre McCurdy [mailto:armccurdy@...il.com] >Sent: 13 April 2017 AM 03:17 >To: musl@...ts.openwall.com >Cc: Jaydeep Patil >Subject: Re: [musl] [MUSL] 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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