[Mesa-dev] [PATCH v2] nvc0/ir: be more careful about preserving modifiers in SHLADD creation

[Ilia Mirkin]

On Thu, Oct 13, 2016 at 9:53 AM, Samuel Pitoiset
<samuel.pitoiset at gmail.com> wrote:
>
>
> On 10/12/2016 08:42 PM, Ilia Mirkin wrote:
>>
>> src2 was being given the wrong modifier, and we were not properly
>> managing the modifier on the SHL source either.
>>
>> Signed-off-by: Ilia Mirkin <imirkin at alum.mit.edu>
>> ---
>>  src/gallium/drivers/nouveau/codegen/nv50_ir_peephole.cpp | 12
>> +++++-------
>>  1 file changed, 5 insertions(+), 7 deletions(-)
>>
>> diff --git a/src/gallium/drivers/nouveau/codegen/nv50_ir_peephole.cpp
>> b/src/gallium/drivers/nouveau/codegen/nv50_ir_peephole.cpp
>> index d88bb34..737bda3 100644
>> --- a/src/gallium/drivers/nouveau/codegen/nv50_ir_peephole.cpp
>> +++ b/src/gallium/drivers/nouveau/codegen/nv50_ir_peephole.cpp
>> @@ -2163,7 +2163,6 @@ LateAlgebraicOpt::tryADDToSHLADD(Instruction *add)
>>     Value *src1 = add->getSrc(1);
>>     ImmediateValue imm;
>>     Instruction *shl;
>> -   Modifier mod[2];
>>     Value *src;
>>     int s;
>>
>> @@ -2182,20 +2181,19 @@ LateAlgebraicOpt::tryADDToSHLADD(Instruction *add)
>>     src = add->getSrc(s);
>>     shl = src->getUniqueInsn();
>>
>> -   if (shl->bb != add->bb || shl->usesFlags() || shl->subOp)
>> +   if (shl->bb != add->bb || shl->usesFlags() || shl->subOp ||
>> shl->src(0).mod)
>
>
> SHL can't have any modifiers, why do you check it here? I would say it's
> just for safety, but if the compiler adds modifiers to SHL something is
> really wrong...

That's a target-specific property. There could be some future
hypothetical target that allows modifiers on shl. The check is cheap,
so may as well :) If it were a more expensive check, I'd do it in a
#if debug thing maybe.

>
> Looks good now.
>
> Reviewed-by: Samuel Pitoiset <samuel.pitoiset at gmail.com>

Thanks!

>
>
>>        return false;
>>
>>     if (!shl->src(1).getImmediate(imm))
>>        return false;
>>
>> -   mod[0] = add->src(0).mod;
>> -   mod[1] = add->src(1).mod;
>> -
>>     add->op = OP_SHLADD;
>>     add->setSrc(2, add->src(!s));
>> -   add->src(2).mod = mod[s];
>> -
>> +   // SHL can't have any modifiers, but the ADD source may have had
>> +   // one. Preserve it.
>>     add->setSrc(0, shl->getSrc(0));
>> +   if (s == 1)
>> +      add->src(0).mod = add->src(1).mod;
>>     add->setSrc(1, new_ImmediateValue(shl->bb->getProgram(),
>> imm.reg.data.u32));
>>     add->src(1).mod = Modifier(0);
>>
>>
>
> --
> -Samuel