[Mesa-dev] [PATCH 1/2] gm107/ir: make use of FADD32I for all immediates

[Samuel Pitoiset]

On 06/28/2016 04:00 PM, Ilia Mirkin wrote:
> On Tue, Jun 28, 2016 at 4:33 AM, Samuel Pitoiset
> <samuel.pitoiset at gmail.com> wrote:
>>
>>
>> On 06/28/2016 05:10 AM, Ilia Mirkin wrote:
>>>
>>> On Mon, Jun 27, 2016 at 6:08 PM, Samuel Pitoiset
>>> <samuel.pitoiset at gmail.com> wrote:
>>>>
>>>>
>>>>
>>>> On 06/28/2016 12:06 AM, Ilia Mirkin wrote:
>>>>>
>>>>>
>>>>> On Mon, Jun 27, 2016 at 6:05 PM, Ilia Mirkin <imirkin at alum.mit.edu>
>>>>> wrote:
>>>>>>
>>>>>>
>>>>>> On Mon, Jun 27, 2016 at 6:04 PM, Samuel Pitoiset
>>>>>> <samuel.pitoiset at gmail.com> wrote:
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> On 06/28/2016 12:02 AM, Ilia Mirkin wrote:
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>> This loses you saturation. Does the target account for this?
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> No saturate flag for FADD32I.
>>>>>>
>>>>>>
>>>>>>
>>>>>> That's not what I asked.
>>>>>
>>>>>
>>>>>
>>>>> Specifically look at this code:
>>>>>
>>>>> bool
>>>>> TargetNVC0::isSatSupported(const Instruction *insn) const
>>>>> {
>>>>>    if (insn->op == OP_CVT)
>>>>>       return true;
>>>>>    if (!(opInfo[insn->op].dstMods & NV50_IR_MOD_SAT))
>>>>>       return false;
>>>>>
>>>>>    if (insn->dType == TYPE_U32)
>>>>>       return (insn->op == OP_ADD) || (insn->op == OP_MAD);
>>>>>
>>>>>    // add f32 LIMM cannot saturate
>>>>>    if (insn->op == OP_ADD && insn->sType == TYPE_F32) {
>>>>>       if (insn->getSrc(1)->asImm() &&
>>>>>           insn->getSrc(1)->reg.data.u32 & 0xfff)
>>>>>          return false;
>>>>>    }
>>>>>
>>>>> Note how it will say that sat is supported for SIMMs with FADD? So the
>>>>> compiler will generate those ops, but then the emitter won't be able
>>>>> to handle it.
>>>>>
>>>>
>>>> Okay, I get it.
>>>
>>>
>>> By the way, instead of trying to fight the longIMMD, you should just fix
>>> it -
>>>
>>>         /*0008*/               @P0 FADD R0, R0, 1.NEG;      /*
>>> 0x3858203f80000000 */
>>>
>>> which corresponds nicely to
>>>
>>>       emitNEG(0x2d, insn->src(1));
>>>
>>> The issue is that emitIMMD does
>>>
>>>    if (len == 19) {
>>> ...
>>>       emitField( 56,   1, (val & 0x80000) >> 19);
>>>       emitField(pos, len, (val & 0x7ffff));
>>>
>>> So the problem is that the 56 isn't as fixed as the emission code had
>>> hoped. I suspect that adjusting it will fix all these silly cases.
>>>
>>>   -ilia
>>>
>>
>>         /*0010*/               @P0 FADD R0, R0, 0.NEG;      /*
>> 0x3858200000000000 */
>>         /*0010*/               @P0 FADD R0, R0, -0;      /*
>> 0x3958000000000000 */
>>
>> urgh?
>
> So ... what problem were you having again?

The thing is: why those 2 instructions use a different position for the 
neg flag?

An by the way, the bit 56 is fixed for all short immediates.

>
>   -ilia
>

-- 
-Samuel