How reuse inline assembler conditionals?

[Andreas Jaeger]

"Benjamin K." <bkausbk@web.de> writes:

> Example (need x86 compatible system):
>
> int Increment(int a){
>     int tmp;
>     asm volatile(
>     "inc %0\n"
>     : "=r" (tmp)
>     : "0" (a)
>     );
>     return tmp;
> }
>
> x86 cpu will set conditional flags after using INC
> instruction, but this conditional will no be used by
> gcc, why?

gcc does not interpret the asm statement at all.  It especially
considers condition codes as changes on most platforms.

> Gcc will produce something like:
>
> if (Increment(10)==0) {
> }
>
> mov eax,10
> inc eax
> test eax,eax
> jnz Lxx
>
> But "test eax,eax" isn't needed here.
> How can the function be declared to reuse asm conditional flags?

This is impossible AFAIK,

Andreas
-- 
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