RFC: Should x86-64 support arbitrary calling conventions?

[H.J. Lu]

On Thu, Mar 23, 2017 at 4:14 PM, Richard Henderson <rth@twiddle.net> wrote:
> On 03/24/2017 01:41 AM, H.J. Lu wrote:
>>
>> +# ifdef STATE_SAVE_MASK
>> +       movl $STATE_SAVE_MASK, %eax
>> +       xorl %edx, %edx
>> +       # Clear the XSAVE Header.
>> +       movq $0, (STATE_SAVE_OFFSET + 512)(%rsp)
>> +       movq $0, (STATE_SAVE_OFFSET + 512 + 8)(%rsp)
>> +       movq $0, (STATE_SAVE_OFFSET + 512 + 8 * 2)(%rsp)
>> +       movq $0, (STATE_SAVE_OFFSET + 512 + 8 * 3)(%rsp)
>> +       movq $0, (STATE_SAVE_OFFSET + 512 + 8 * 4)(%rsp)
>> +       movq $0, (STATE_SAVE_OFFSET + 512 + 8 * 5)(%rsp)
>> +       movq $0, (STATE_SAVE_OFFSET + 512 + 8 * 6)(%rsp)
>> +       movq $0, (STATE_SAVE_OFFSET + 512 + 8 * 7)(%rsp)
>>  # endif
>
>
> You've just cleared %rdx.  Use that instead of 8*4 bytes of immediate zeros.
>
> Given that you have to ifdef this code into place, isn't it somewhat
> pointless to hide xsave behind a macro in the next line?
>
>> +       STATE_SAVE STATE_SAVE_OFFSET(%rsp)
>
>
> I think it would be clearer to inline the two save instructions instead.
>
>

Good ideas.  Here is the updated patch.

-- 
H.J.
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