Re: [PATCH v2] nv50/ir: optimize shl(a, 0) to a

From: Ilia Mirkin <imirkin@alum.mit.edu>
To: Karol Herbst <karolherbst@gmail.com>
Cc: nouveau@lists.freedesktop.org, mesa-dev@lists.freedesktop.org
Subject: Re: [PATCH v2] nv50/ir: optimize shl(a, 0) to a
Date: Sat, 29 Apr 2017 20:28:26 -0400	[thread overview]
Message-ID: <CAKb7UvjfCUF2_WN9FrjoZnpX_2K+YwY9_PhPYjH=fOfM2SRN8A@mail.gmail.com> (raw)
In-Reply-To: <CAKb7Uvg2ZxT4JyfeG24BLDTKHXbFuyx=H2tRnQBM63h1k_kJ8Q@mail.gmail.com>

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Maybe in a separate change. I'd want to double check on all gens. I think
the thing I suggested is sufficient.

On Apr 29, 2017 8:09 PM, "Karol Herbst" <karolherbst@gmail.com> wrote:

2017-04-30 0:28 GMT+02:00 Ilia Mirkin <imirkin@alum.mit.edu>:
> On Sat, Apr 29, 2017 at 6:09 PM, Karol Herbst <karolherbst@gmail.com>
wrote:
>> helps two alien isolation shaders
>>
>> shader-db:
>> total instructions in shared programs : 4251497 -> 4251494 (-0.00%)
>> total gprs used in shared programs    : 513962 -> 513962 (0.00%)
>> total local used in shared programs   : 29797 -> 29797 (0.00%)
>> total bytes used in shared programs   : 38960264 -> 38960232 (-0.00%)
>>
>>                 local        gpr       inst      bytes
>>     helped           0           0           2           2
>>       hurt           0           0           0           0
>>
>> v2: handle potential mods on src0
>>
>> Signed-off-by: Karol Herbst <karolherbst@gmail.com>
>> Reviewed-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
>> Reviewed-by: Ilia Mirkin <imirkin@alum.mit.edu>
>> ---
>>  src/gallium/drivers/nouveau/codegen/nv50_ir_peephole.cpp | 7 +++++++
>>  1 file changed, 7 insertions(+)
>>
>> diff --git a/src/gallium/drivers/nouveau/codegen/nv50_ir_peephole.cpp
b/src/gallium/drivers/nouveau/codegen/nv50_ir_peephole.cpp
>> index 015def0391..82da0d3e48 100644
>> --- a/src/gallium/drivers/nouveau/codegen/nv50_ir_peephole.cpp
>> +++ b/src/gallium/drivers/nouveau/codegen/nv50_ir_peephole.cpp
>> @@ -1284,6 +1284,13 @@ ConstantFolding::opnd(Instruction *i,
ImmediateValue &imm0, int s)
>>
>>     case OP_SHL:
>>     {
>> +      if (s == 1 && imm0.isInteger(0)) {
>> +         i->op = i->src(0).mod.getOp();
>> +         if (i->op != OP_CVT)
>> +            i->src(0).mod = 0;
>
> Is this necessary? Presumably if the op != 0, then op == OP_CVT...
>

yeah, no idea. I just thought I do it right when I actually depend on
the getOp magic. But we can't emit any mods to begin with, so maybe we
should just drop the mod handling and be done with it?

>> +         i->setSrc(1, NULL);
>> +         break;
>> +      }
>>        if (s != 1 || i->src(0).mod != Modifier(0))
>>           break;
>>        // try to concatenate shifts
>> --
>> 2.12.2
>>

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