Re: [Qemu-devel] [PATCH] target-i386: Fix aflag logic for CODE64 and the 0x67 prefix

[Paolo Bonzini <pbonzini@redhat.com>]

Il 31/05/2013 17:03, Richard Henderson ha scritto:
> Ping.
> 
> On 05/29/2013 12:30 PM, Richard Henderson wrote:
>> The code reorganization in commit 4a6fd938 broke handling of PREFIX_ADR.
>> While fixing this, tidy and comment the code so that it's more obvious
>> what's going on in setting both aflag and dflag.
>>
>> The TARGET_X86_64 ifdef can be eliminated because CODE64 expands to the
>> constant zero when TARGET_X86_64 is undefined.
>>
>> Cc: Paolo Bonzini <pbonzini@redhat.com>
>> Reported-by: Laszlo Ersek <lersek@redhat.com>
>> Signed-off-by: Richard Henderson <rth@twiddle.net>
>> ---
>>  target-i386/translate.c | 30 +++++++++++++++---------------
>>  1 file changed, 15 insertions(+), 15 deletions(-)
>>
>> diff --git a/target-i386/translate.c b/target-i386/translate.c
>> index 0aeccdb..14b0298 100644
>> --- a/target-i386/translate.c
>> +++ b/target-i386/translate.c
>> @@ -4677,8 +4677,6 @@ static target_ulong disas_insn(CPUX86State *env, DisasContext *s,
>>      }
>>      s->pc = pc_start;
>>      prefixes = 0;
>> -    aflag = s->code32;
>> -    dflag = s->code32;
>>      s->override = -1;
>>      rex_w = -1;
>>      rex_r = 0;
>> @@ -4801,23 +4799,25 @@ static target_ulong disas_insn(CPUX86State *env, DisasContext *s,
>>      }
>>  
>>      /* Post-process prefixes.  */
>> -    if (prefixes & PREFIX_DATA) {
>> -        dflag ^= 1;
>> -    }
>> -    if (prefixes & PREFIX_ADR) {
>> -        aflag ^= 1;
>> -    }
>> -#ifdef TARGET_X86_64
>>      if (CODE64(s)) {
>> -        if (rex_w == 1) {
>> -            /* 0x66 is ignored if rex.w is set */
>> -            dflag = 2;
>> +        /* In 64-bit mode, the default data size is 32-bit.  Select 64-bit
>> +           data with rex_w, and 16-bit data with 0x66; rex_w takes precedence
>> +           over 0x66 if both are present.  */
>> +        dflag = (rex_w > 0 ? 2 : prefixes & PREFIX_DATA ? 0 : 1);
>> +        /* In 64-bit mode, 0x67 selects 32-bit addressing.  */
>> +        aflag = (prefixes & PREFIX_ADR ? 1 : 2);
>> +    } else {
>> +        /* In 16/32-bit mode, 0x66 selects the opposite data size.  */
>> +        dflag = s->code32;
>> +        if (prefixes & PREFIX_DATA) {
>> +            dflag ^= 1;
>>          }
>> -        if (!(prefixes & PREFIX_ADR)) {
>> -            aflag = 2;
>> +        /* In 16/32-bit mode, 0x67 selects the opposite addressing.  */
>> +        aflag = s->code32;
>> +        if (prefixes & PREFIX_ADR) {
>> +            aflag ^= 1;
>>          }

Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Cc: qemu-stable@nongnu.org

>>      }
>> -#endif
>>  
>>      s->prefix = prefixes;
>>      s->aflag = aflag;
>>
>