Date: Mon, 14 Oct 2019 10:18:59 -0400 From: Rich Felker <dalias@...c.org> To: musl@...ts.openwall.com Subject: Re: [PATCH] mips: add single-instruction math functions On Wed, Sep 11, 2019 at 01:05:04PM +0300, info@...ile-stream.com wrote: > > non-commit text: > gcc puts annoying nop into the delay slot for these functions, e.g.: > abs.d $f0,$f12 > jr $ra > nop > is there any way to get rid of this without using pure .S? I'm taking care of merging this now, since it seems concerns about abs2008 being able to be treated as an isa level were adequately addressed, and one interesting thing is that I don't see the above happening. My mips toolchain is gcc 6.3.0 and I get: 00000000 <fabs>: 0: 03e00008 jr ra 4: 46206005 abs.d $f0,$f12 Perhaps you have an older gcc, or there's some option that affects whether it can use delay slots? It looks like gcc is emitting the code as: #APP # 8 "../../src/math/mips/fabs.c" 1 abs.d $f0,$f12 # 0 "" 2 #NO_APP jr $31 but not using the noreorder directive, allowing the assembler to reorder into delay slots. Rich
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