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Re: [Qemu-devel] [PATCH] i386: fix icount processing for repz instructio


From: Paolo Bonzini
Subject: Re: [Qemu-devel] [PATCH] i386: fix icount processing for repz instructions
Date: Thu, 23 Oct 2014 22:19:15 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.2.0


On 10/23/2014 07:05 PM, Richard Henderson wrote:
> On 10/21/2014 06:03 AM, Pavel Dovgalyuk wrote:
>> +    dc->repz_opt = dc->jmp_opt
>> +                    /* Do not optimize repz jumps at all in icount mode, 
>> because
>> +                       rep movsS instructions are execured with different 
>> paths
>> +                       in repz_opt and !repz_opt modes. The first one was 
>> used
>> +                       always except single step mode. And this setting
>> +                       disables jumps optimization and control paths become
>> +                       equivalent in run and single step modes.
>> +                       Now there will be no jump optimization for repz in
>> +                       trace and replay modes and there will always be an
>> +                       additional step for ecx=0.
>> +                     */
>> +                   || use_icount;
> 
> My aesthetics are offended by the placement of this comment.  Please write
> 
>   /* Comment */
>   dc->repz_opt = x || y;
> 
> That said, surely that test should be !use_icount.

And "&& !use_icount", even (it becomes "|| use_icount" in the ifs)?

Paolo



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