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From: Leon Alrae <leon.alrae@imgtec.com>
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Date: Mon, 19 Oct 2015 17:40:26 +0100
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Subject: Re: [Qemu-devel] [PATCH v2] target-mips: remove wrong checks for
 recip.fmt and rsqrt.fmt
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To: Petar Jovanovic <petar.jovanovic@rt-rk.com>, qemu-devel@nongnu.org, petar.jovanovic@imgtec.com

On 11/10/15 21:30, Aurelien Jarno wrote:
> (sorry for the late answer)
> 
> On 2015-08-26 14:12, Petar Jovanovic wrote:
>> From: Petar Jovanovic <petar.jovanovic@imgtec.com>
>>
>> Instructions recip.{s|d} and rsqrt.{s|d} do not require 64-bit FPU neither
>> they require any particular mode for its FPU. This patch removes the checks
>> that may break a program that uses these instructions.
> 
> That is correct. That said these instructions do require at least a
> MIPS32R2 or a MIPS64R1 CPU. I guess we should add these checks now that
> check_cop1x do not guard them anymore.

I suspect that this might too restrictive if we take into account also
legacy processors. As far as I know these instructions were already
present in MIPS IV implementations. I think it'll be safer if for the
pre-MIPS32R2 and pre-MIPS64R1 CPUs we keep the check_cop1x. (actually
I'm not certain if check_cop1x is correct, but at least we aren't
relaxing the previous restrictions too much).

Regards,
Leon