[Nouveau] [PATCH v2] nv50/ir: Handle OP_CVT when folding constant expressions

[Tobias Klausmann]

On 11.01.2015 20:19, Ilia Mirkin wrote:
> On Sun, Jan 11, 2015 at 12:27 PM, Tobias Klausmann
> <tobias.johannes.klausmann at mni.thm.de> wrote:
>>
>> On 11.01.2015 01:58, Ilia Mirkin wrote:
>>> On Fri, Jan 9, 2015 at 8:24 PM, Tobias Klausmann
>>> <tobias.johannes.klausmann at mni.thm.de> wrote:
>>>> Folding for conversions: F32->(U{16/32}, S{16/32}) and (U{16/32},
>>>> {S16/32})->F32
>>>>
>>>> Signed-off-by: Tobias Klausmann <tobias.johannes.klausmann at mni.thm.de>
>>>> ---
>>>> V2: beat me, whip me, split out F64
>>>>
>>>>    .../drivers/nouveau/codegen/nv50_ir_peephole.cpp   | 81
>>>> ++++++++++++++++++++++
>>>>    1 file changed, 81 insertions(+)
>>>>
>>>> diff --git a/src/gallium/drivers/nouveau/codegen/nv50_ir_peephole.cpp
>>>> b/src/gallium/drivers/nouveau/codegen/nv50_ir_peephole.cpp
>>>> index 9a0bb60..741c74f 100644
>>>> --- a/src/gallium/drivers/nouveau/codegen/nv50_ir_peephole.cpp
>>>> +++ b/src/gallium/drivers/nouveau/codegen/nv50_ir_peephole.cpp
>>>> @@ -997,6 +997,87 @@ ConstantFolding::opnd(Instruction *i, ImmediateValue
>>>> &imm0, int s)
>>>>          i->op = OP_MOV;
>>>>          break;
>>>>       }
>>>> +   case OP_CVT: {
>>>> +      Storage res;
>>>> +      bld.setPosition(i, true); /* make sure bld is init'ed */
>>>> +      switch(i->dType) {
>>>> +      case TYPE_U16:
>>>> +         switch (i->sType) {
>>>> +         case TYPE_F32:
>>>> +            if (i->saturate)
>>>> +               res.data.u16 = util_iround(CLAMP(imm0.reg.data.f32, 0,
>>>> +                                                UINT16_MAX));
>>> Where did this saturate stuff come from? It doesn't make sense to
>>> saturate to a non-float dtype. I'd go ahead and just
>>> assert(!i->saturate) in the int dtype cases.
>>>
>>> One does wonder what the hw does if the float doesn't fit in the
>>> destination... whether it saturates or not. I don't hugely care
>>> though.
>> Actually i can't remember why that was added in the first place, i'll go
>> ahead and follow your advice here.
> Oh wait... this was to support saturating an array access into a u16...
>
>           const int sat = (i->op == OP_TXF) ? 1 : 0;
>           DataType sTy = (i->op == OP_TXF) ? TYPE_U32 : TYPE_F32;
>           bld.mkCvt(OP_CVT, TYPE_U16, layer, sTy, src)->saturate = sat;
>
> So... basically if the source is a U32 and the dest is a U16, we want
> to saturate there? IMO this is such a minor use-case that it doesn't
> really matter. However I guess you can keep the saturate bits around
> if you like.
We can do it with or without the saturate if we rely on the test, 
assert(!i->saturate)'ing is the only thing that breaks the test you sure 
meant:

glsl-resource-not-bound 1DArray
glsl-resource-not-bound 2DArray
glsl-resource-not-bound 2DMSArray

>
>    -ilia