extended asm and input parameters

[Andrew Haley]

On 07/04/2013 11:07 AM, dw wrote:
> Hey Andrew, thanks for the response.
> 
>  > main:
>  > .LFB1:
>  >     leaq    -32(%rsp), %rdi
>  >     movl    $32, %ecx
>  >     xorl    %eax, %eax
>  > #APP
>  > # 2 "z.c" 1
>  >     rep stosb
>  > # 0 "" 2
>  > # 2 "z.c" 1
>  >     rep stosb
>  > # 0 "" 2
>  > #NO_APP
>  >     xorl    %eax, %eax
>  >     ret
> 
> Interesting.  So, you are getting the duplicate zeroing of eax, but not 
> the duplicate loading of rdi.  That's certainly an improvement.
> 
> I'm using 4.8.0.  You?  If this is something that was improved in 4.8.1, 
> perhaps it's time for me to upgrade.

Ah, I'm on 4.7.  So this might be a regression: we should check.

> Any special compile switches other than -Os?

No.

>  > By the way, your asm is wrong: stosb modifies its registers, and you
>  > must tell GCC that.
> 
> I'll assume this was intended to be humorous.

Absolutely not.  This is critical.

Andrew.