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Re: [Qemu-devel] [PATCH] ppc: Three floating point fixes
From: |
Richard Henderson |
Subject: |
Re: [Qemu-devel] [PATCH] ppc: Three floating point fixes |
Date: |
Sun, 18 Aug 2019 09:10:01 +0100 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 |
On 8/16/19 11:59 PM, Aleksandar Markovic wrote:
>> From: "Paul A. Clarke" <address@hidden>
...
>> ISA 3.0B has xscvdpspn leaving its result in word 1 of the target
> register,
>> and mffprwz expecting its input to come from word 0 of the source
> register.
>> This sequence fails with QEMU, as a shift is required between those two
>> instructions. However, the hardware splats the result to both word 0
> and
>> word 1 of its output register, so the shift is not necessary.
>> Expect a future revision of the ISA to specify this behavior.
>>
>
> Hmmm... Isn't this a gcc bug (using undocumented hardware feature), given
> everything you said here?
The key here is "expect a future revision of the ISA to specify this behavior".
It's clearly within IBM's purview to adjust the specification to document a
previously undocumented hardware feature.
r~
- [Qemu-devel] [PATCH] ppc: Three floating point fixes, Paul A. Clarke, 2019/08/16
- Re: [Qemu-devel] [PATCH] ppc: Three floating point fixes, Aleksandar Markovic, 2019/08/16
- Re: [Qemu-devel] [PATCH] ppc: Three floating point fixes, Aleksandar Markovic, 2019/08/17
- Re: [Qemu-devel] [PATCH] ppc: Three floating point fixes,
Richard Henderson <=
- Re: [Qemu-devel] [PATCH] ppc: Three floating point fixes, Aleksandar Markovic, 2019/08/18
- Re: [Qemu-devel] [PATCH] ppc: Three floating point fixes, David Gibson, 2019/08/19
- Re: [Qemu-devel] [PATCH] ppc: Three floating point fixes, Aleksandar Markovic, 2019/08/19
- Re: [Qemu-devel] [Qemu-ppc] [PATCH] ppc: Three floating point fixes, Paul Clarke, 2019/08/19
- Re: [Qemu-devel] [Qemu-ppc] [PATCH] ppc: Three floating point fixes, David Gibson, 2019/08/20
- Re: [Qemu-devel] [Qemu-ppc] [PATCH] ppc: Three floating point fixes, Peter Maydell, 2019/08/20
- Re: [Qemu-devel] [Qemu-ppc] [PATCH] ppc: Three floating point fixes, David Gibson, 2019/08/22
Re: [Qemu-devel] [PATCH] ppc: Three floating point fixes, Richard Henderson, 2019/08/18
Re: [Qemu-devel] [PATCH] ppc: Three floating point fixes, David Gibson, 2019/08/19