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Re: basic asm and memory clobbers


On Fri, Nov 20, 2015 at 02:05:01PM +0100, Richard Henderson wrote:
> I'd be perfectly happy to deprecate and later completely remove basic asm 
> within functions.
> 
> Because IMO it's essentially useless.  It has no inputs, no outputs, and no 
> way to tell the compiler what machine state has been changed.  We can say 
> that "it clobbers everything", but that's not actually useful, and quite 
> difficult as you're finding out.
> 
> It seems to me that it would be better to remove the feature, forcing what 
> must be an extremely small number of users to audit and update to extended 
> asm.

Should  asm("bla");  then be an extended asm with no input, no outputs,
no (non-automatic) clobbers?  That would be the most straightforward and
logical semantics, but will it break user code?


Segher


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