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Date: Mon, 6 Apr 2026 14:33:40 +0200
From: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
To: "Maciej W. Rozycki" <macro@orcam.me.uk>
Cc: linux-mips@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] MIPS: kernel: Remove $0 clobber from `mult_sh_align_mod'
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References: <alpine.DEB.2.21.2603281409240.60268@angie.orcam.me.uk>
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On Sat, Mar 28, 2026 at 02:29:10PM +0000, Maciej W. Rozycki wrote:
> Remove rubbish $0 clobber added to inline asm within `mult_sh_align_mod' 
> with the removal of support for GCC versions below 3.4 made with commit 
> 57810ecb581a ("MIPS: Remove GCC_IMM_ASM & GCC_REG_ACCUM macros").  
> 
> Previously a macro was used that, depending on GCC version, expanded to 
> either `accum' or $0.  Since the latter choice was only a placeholder to 
> keep the syntax consistent and the register referred is hardwired, there 
> is no point in having it here as it has no effect on code generation.  
> 
> Signed-off-by: Maciej W. Rozycki <macro@orcam.me.uk>
> ---
>  arch/mips/kernel/r4k-bugs64.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> linux-mips-cpu-bugs64-gcc-reg-accum-zero.diff
> Index: linux-macro/arch/mips/kernel/r4k-bugs64.c
> ===================================================================
> --- linux-macro.orig/arch/mips/kernel/r4k-bugs64.c
> +++ linux-macro/arch/mips/kernel/r4k-bugs64.c
> @@ -91,7 +91,7 @@ void mult_sh_align_mod(long *v1, long *v
>  		".set	pop"
>  		: "=&r" (lv1), "=r" (lw)
>  		: "r" (m1), "r" (m2), "r" (s), "I" (0)
> -		: "hi", "lo", "$0");
> +		: "hi", "lo");
>  	/* We have to use single integers for m1 and m2 and a double
>  	 * one for p to be sure the mulsidi3 gcc's RTL multiplication
>  	 * instruction has the workaround applied.  Older versions of

applied to mips-next

Thomas.

-- 
Crap can work. Given enough thrust pigs will fly, but it's not necessarily a
good idea.                                                [ RFC1925, 2.3 ]