Re: [PATCHv5 4/4] KVM: emulator: optimize "rep ins" handling.

[Avi Kivity <avi@redhat.com>]

On 08/05/2012 06:18 PM, Gleb Natapov wrote:
> On Sun, Aug 05, 2012 at 06:03:12PM +0300, Avi Kivity wrote:
>> On 07/30/2012 05:38 PM, Gleb Natapov wrote:
>> > Optimize "rep ins" by allowing emulator to write back more than one
>> > datum at a time. Introduce new operand type OP_MEM_STR which tells
>> > writeback() that dst contains pointer to an array that should be written
>> > back as opposite to just one data element.
>> > 
>> >  
>> >  	if (ctxt->rep_prefix && (ctxt->d & String)) {
>> > +		unsigned int count;
>> >  		struct read_cache *r = &ctxt->io_read;
>> > -		register_address_increment(ctxt, &ctxt->regs[VCPU_REGS_RCX], -1);
>> > +		if ((ctxt->d & SrcMask) == SrcSI)
>> > +			count = ctxt->src.count;
>> > +		else
>> > +			count = ctxt->dst.count;
>> > +		register_address_increment(ctxt, &ctxt->regs[VCPU_REGS_RCX],
>> > +				-count);
>> >  
>> 
>> count is unsigned.  Does it sign extend correctly in
>> register_address_increment()?
>> 
> I think it sign extent before register_address_increment() when compiler
> sees -count. count is in the range 1-1024 here, so there shouldn't be a
> problem. By I welcome better suggestions.

There is actually no problem since the 'inc' parameter is signed.

-- 
error compiling committee.c: too many arguments to function