Re: [PATCH] Support APX NF

[Jan Beulich <jbeulich@suse.com>]

On 29.02.2024 13:41, Cui, Lili wrote:
> 
> 
>> -----Original Message-----
>> From: Jan Beulich <jbeulich@suse.com>
>> Sent: Thursday, February 29, 2024 8:04 PM
>> To: Cui, Lili <lili.cui@intel.com>
>> Cc: Lu, Hongjiu <hongjiu.lu@intel.com>; binutils@sourceware.org
>> Subject: Re: [PATCH] Support APX NF
>>
>> On 29.02.2024 13:00, Cui, Lili wrote:
>>>> On 27.02.2024 10:01, Cui, Lili wrote:
>>>>> @@ -8860,6 +8880,9 @@ match_template (char mnem_suffix)
>>>>>  		  goto check_operands_345;
>>>>>  		}
>>>>>  	      else if (t->opcode_space != SPACE_BASE
>>>>> +		       /* Map0 and map1 are promoted to MAP4 when NF is
>>>> enabled.
>>>>> +			*/
>>>>> +		       && !t->opcode_modifier.nf
>>>>>  		       && (t->opcode_space != SPACE_0F
>>>>>  			   /* MOV to/from CR/DR/TR, as an exception, follow
>>>>>  			      the base opcode space encoding model.  */
>>>>
>>>> I don't understand this: How does a template permitting NF matter here?
>>>> I could see the immediately preceding "else if" become something
>>>> along the lines of
>>>>
>>>> 	      else if (is_cpu (t, CpuAPX_F) && (i.operands == 3 ||
>>>> i.has_nf))
>>>>
>>>> But I admit I didn't fully think this through. It's just that the
>>>> change as is looks wrong to me.
>>>>
>>>
>>> I was also dissatisfied with this place yesterday and then modified it to:
>>>
>>>               else if (t->opcode_space != SPACE_BASE
>>>                        /* For EVEX-promoted instructions, opcode_space is
>>>                           promoted to MAP4.  */
>>>                        && (t->opcode_space != SPACE_EVEXMAP4
>>>                            || t->mnem_off == MN_movbe)
>>>                        && (t->opcode_space != SPACE_0F
>>>                            /* MOV to/from CR/DR/TR, as an exception, follow
>>>                               the base opcode space encoding model.  */
>>>                            || (t->base_opcode | 7) != 0x27))
>>>
>>> For EVEX-promoted instructions, opcode_space is promoted to MAP4. The
>> old judgment no longer fit for EVEX promoted instructions. However, the logic
>> of this place is still not good.
>>
>> So what about my suggestion?
> 
> Your suggestion is better, but we need to replace i.has_nf with new judgment, i.has_nf cannot cover instructions like adc, the testcase will be added by another patch.
> 
> +             else if (is_cpu (t, CpuAPX_F)
> +                      && (i.operands == 3 || (t->opcode_space == SPACE_EVEXMAP4
> +                                              && t->mnem_off != MN_movbe)))

Ah yes, to cover the non-NF 2-operand forms. But then is the "i.operands == 3"
part actually still needed?

Jan