[Mesa-dev] [PATCH 1/2] nvc0/ir: avoid generating illegal instructions for compute constbuf loads

[Hans de Goede]

Hi,

On 26-05-16 14:43, Ilia Mirkin wrote:
> On Thu, May 26, 2016 at 8:41 AM, Hans de Goede <hdegoede at redhat.com> wrote:
>> Hi,
>>
>>
>> On 26-05-16 04:44, Ilia Mirkin wrote:
>>>
>>> For user-supplied constbufs, fileIndex is 0. In that case, when we
>>> subtract 1, we'll end up loading from constbuf offset -16. This is
>>> illegal, and there are asserts to avoid it. Normally we'd just DCE it,
>>> but no point in generating the instructions if they're not going to be
>>> used.
>>>
>>> Signed-off-by: Ilia Mirkin <imirkin at alum.mit.edu>
>>> ---
>>>  src/gallium/drivers/nouveau/codegen/nv50_ir_lowering_nvc0.cpp | 3 ++-
>>>  1 file changed, 2 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/src/gallium/drivers/nouveau/codegen/nv50_ir_lowering_nvc0.cpp
>>> b/src/gallium/drivers/nouveau/codegen/nv50_ir_lowering_nvc0.cpp
>>> index 869040c..da2fa4b 100644
>>> --- a/src/gallium/drivers/nouveau/codegen/nv50_ir_lowering_nvc0.cpp
>>> +++ b/src/gallium/drivers/nouveau/codegen/nv50_ir_lowering_nvc0.cpp
>>> @@ -2180,11 +2180,11 @@ NVC0LoweringPass::handleLDST(Instruction *i)
>>>           // memory.
>>>           int8_t fileIndex = i->getSrc(0)->reg.fileIndex - 1;
>>>           Value *ind = i->getIndirect(0, 1);
>>> -         Value *ptr = loadUboInfo64(ind, fileIndex * 16);
>>>
>>>           // TODO: clamp the offset to the maximum number of const buf.
>>>           if (i->src(0).isIndirect(1)) {
>>>              Value *offset = bld.loadImm(NULL,
>>> i->getSrc(0)->reg.data.offset + typeSizeof(i->sType));
>>> +            Value *ptr = loadUboInfo64(ind, fileIndex * 16);
>>>              Value *length = loadUboLength32(ind, fileIndex * 16);
>>>              Value *pred = new_LValue(func, FILE_PREDICATE);
>>>              if (i->src(0).isIndirect(0)) {
>>> @@ -2200,6 +2200,7 @@ NVC0LoweringPass::handleLDST(Instruction *i)
>>>                 bld.mkMov(i->getDef(0), bld.mkImm(0));
>>>              }
>>>           } else if (fileIndex >= 0) {
>>> +            Value *ptr = loadUboInfo64(ind, fileIndex * 16);
>>>              if (i->src(0).isIndirect(0)) {
>>>                 bld.mkOp2(OP_ADD, TYPE_U64, ptr, ptr, i->getIndirect(0,
>>> 0));
>>>              }
>>>
>>
>> This patch does not seem to actually change anything, you've just moved the
>> exact
>> same declaration to 2 places ... ?
>
> If loadUboInfo64 had no side-effects you'd be right. However it
> inserts instructions into the current (builder's) bb.

Ah, ok I see, fwiw this patch looks good to me then:

Acked-by: Hans de Goede <hdegoede at redhat.com>

Regards,

Hans



>
>   -ilia
>