clobber list in inline assembly for calls

Ian Lance Taylor iant@google.com
Sat Jan 8 05:24:00 GMT 2011


Daniel Mierswa <impulze@impulze.org> writes:

> On 08.01.2011 05:50, Ian Lance Taylor wrote:
>> You are correct: you have to list all the caller-saved registers in the
>> clobber list.  On 32-bit x86 this is all the registers other than %ebp,
>> %ebx, %edi and %esi.
>> 
>> Ian
>
> If I'm not mistaken that should leave eax, ecx and edx. What about "cc"
> and "memory" though?

Good point, yes, you should add an explicit "memory" clobber.  You don't
need to explicitly clobber "cc".  That is a fixed register (actually gcc
calls it "flags") and as such gcc won't make any particular assumptions
about it in any case.

Ian



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