[Mesa-dev] [PATCH] nouveau: codegen: Take src swizzle into account on loads

[Ilia Mirkin]

Ah, I may have read over your commit too hastily. Will have another look.
On Apr 8, 2016 5:27 AM, "Hans de Goede" <hdegoede at redhat.com> wrote:

> Hi,
>
> On 07-04-16 15:58, Ilia Mirkin wrote:
>
>> That's wrong.
>>
>
> It used to work with the old RES[] code and if one cannot specify
> a source swizzle, then how can I do something like
>
> LOAD TEMP[0].y, MEMORY[0], address
>
> And get the data at absolute global memory address "address" into
> TEMP[0].y ?
>
> This is a must-have for llvm to be able to generate working TGSI code,
> I do not see any way around this.
>
> AFAIK this is exactly what src-swizzling is for. Also note that
> this commit does not change anything if no src-swizzling is specified,
> in that case things work exactly as before.
>
> > The spec for the instruction needs to be clarified...
>
>> The current nouveau impl is correct - only the .x of the address
>> should be loaded, with up to 16 bytes read into the destination.
>>
>
> Ah note this is not about swizzling on the address, that indeed
> makes no sense given how the addressing works for BUFFERS / MEMORY,
> no this is about adding a swizlling postfix to the buffer / memory
> resource specification, for example:
>
> LOAD TEMP[0].y, MEMORY[0].xxxx, TEMP[0]
>
> See the swizzling is done on the resource, not on the address, so
> the swizzling specifies swizzling of the up to 16 bytes read from
> address, it does not influence the address handling at all.
>
> I now see I made an error in my commit msg, it gives the following
> example:
>
> LOAD TEMP[0].y, MEMORY[0].xxxx, TEMP[0].x
>
> This clearly is wrong, the last TEMP[0].x is not even valid TGSI,
> the correct example would be:
>
> LOAD TEMP[0].y, MEMORY[0].xxxx, TEMP[0]
>
> Regards,
>
> Hans
>
>
> On Thu, Apr 7, 2016 at 9:27 AM, Hans de Goede <hdegoede at redhat.com> wrote:
>>
>>> The llvm TGSI backend does things like:
>>>
>>>
>>>
>>> Expecting the data at address TEMP[0].x to get loaded to
>>> TEMP[0].y. Before this commit the data at TEMP[0].x + 4 would be
>>> loaded instead. This commit fixes this.
>>>
>>> Signed-off-by: Hans de Goede <hdegoede at redhat.com>
>>> ---
>>>   src/gallium/drivers/nouveau/codegen/nv50_ir_from_tgsi.cpp | 8 ++++++--
>>>   1 file changed, 6 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/src/gallium/drivers/nouveau/codegen/nv50_ir_from_tgsi.cpp
>>> b/src/gallium/drivers/nouveau/codegen/nv50_ir_from_tgsi.cpp
>>> index 557608e..cc51f5a 100644
>>> --- a/src/gallium/drivers/nouveau/codegen/nv50_ir_from_tgsi.cpp
>>> +++ b/src/gallium/drivers/nouveau/codegen/nv50_ir_from_tgsi.cpp
>>> @@ -2279,12 +2279,16 @@ Converter::handleLOAD(Value *dst0[4])
>>>
>>>            Value *off = fetchSrc(1, c);
>>>            Symbol *sym;
>>> +         uint32_t src0_component_offset = tgsi.getSrc(0).getSwizzle(c)
>>> * 4;
>>> +
>>>            if (tgsi.getSrc(1).getFile() == TGSI_FILE_IMMEDIATE) {
>>>               off = NULL;
>>>               sym = makeSym(tgsi.getSrc(0).getFile(), r, -1, c,
>>> -                          tgsi.getSrc(1).getValueU32(0, info) + 4 * c);
>>> +                          tgsi.getSrc(1).getValueU32(0, info) +
>>> +                          src0_component_offset);
>>>            } else {
>>> -            sym = makeSym(tgsi.getSrc(0).getFile(), r, -1, c, 4 * c);
>>> +            sym = makeSym(tgsi.getSrc(0).getFile(), r, -1, c,
>>> +                          src0_component_offset);
>>>            }
>>>
>>>            Instruction *ld = mkLoad(TYPE_U32, dst0[c], sym, off);
>>> --
>>> 2.7.3
>>>
>>>
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