Re: [Xen-devel] [PATCH 1/3] x86emul: use DstEax also for {, I}{MUL, DIV}

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 16.08.16 at 16:08, <andrew.cooper3@xxxxxxxxxx> wrote:
> On 16/08/16 10:32, Jan Beulich wrote:
>> Just like said in commit c0bc0adf24 ("x86emul: use DstEax where
>> possible"): While it avoids just a few instructions, we should
>> nevertheless make use of generic code as much as possible.
>>
>> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
> 
> This does reduce the amount of code, but it isn't strictly true.  The
> mul and div instructions are DstEaxEdx, as are a number of other
> instructions.
> 
> We shouldn't end up with special casing the eax part because we have an
> easy literal for it, but leaving the edx hard coded because that is
> easier to express in the current code.

I think the code reduction is nevertheless worth it, and reduction
here can only help readability imo. Would you be okay if I added
a comment to the place where the DstEax gets set here? (Note
that DstEdxEax wouldn't be true for 8-bit operations, so I'd rather
not use this as another alias or even a completely new operand
kind description. And please also remember that the tables don't
express all operands in all cases anyway - just consider
SHLD/SHRD.)

Jan


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