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Re: [Qemu-devel] [PATCH] target-i386: add Intel AVX-512 support


From: Eduardo Habkost
Subject: Re: [Qemu-devel] [PATCH] target-i386: add Intel AVX-512 support
Date: Mon, 27 Oct 2014 13:48:54 -0200
User-agent: Mutt/1.5.23 (2014-03-12)

On Fri, Oct 24, 2014 at 07:55:10AM +0200, Paolo Bonzini wrote:
[...]
> I think we can keep the macros.  The actual cleanup would be to have a
> single member for the 32 512-bit ZMM registers, instead of splitting
> xmm/ymmh/zmmh/zmm_hi16.  This will get rid of the YMM_* and ZMM_*
> registers.  However, we could not use simple memcpy()s to marshal in and
> out of the XSAVE data.  We can do it in 2.2.

Now, about the actual 2.3 plans: I believe the xmm/ymmh/zmmh/zmm_hi16
separation actually makes the code simpler, because the only code
touching those registers inside QEMU is xsave/vmstate state
loading/saving, where the bits of the ZMM registers are split into
different sections/fields exactly in the same way.

We can still eliminate the YMM_* and ZMM_* macros while keeping
xmm/ymmh/zmmh/zmm_hi16 as separate fields, and having a single zmm_regs
member would just add unnecessary complexity to the
XSAVE<->CPUX86State<->VMState translation code.

(But if one day TCG starts implementing AVX or AVX512, then it may be
worthwhile to move the ZMM registers into a single field.)

-- 
Eduardo



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