llvm dev - Jun 2018 - Matching ConstantFPSDNode tablegen

I'm trying to match a ConstantFPSDNode == 0 in dag pattern for tablegen but
am having some issues.

So LLVM doesn't seem to accept a floating point constant literal match like:

%v = call <4 x float> @foo(i32 15, float %s, float 0.0, <8 x i32>
%rsrc, <4
x i32> %samp, i1 0, i32 0, i32 0)
  ret <4 x float> %v

def : XXXPat<(v4f32 (int_foo i32:$mask, f32:$s, 0, v8i32:$rsrc,
v4i32:$sampler, i1:$unorm, 0, i32:$cachepolicy)), (FOO_MI (COPY_TO_REGCLASS
?:$s, 32RegClass), ?:$rsrc, ?:$sampler, (as_i32imm ?:$mask), (as_i1imm
?:$unorm), (as_i1imm ?:$cachepolicy), (as_i1imm ?:$cachepolicy), 0, 0, 0, {
0 })>;

which would be ideal. This seems to be because OPC_CheckInteger only checks
for ConstantSDNode and not ConstantFPSDNode. So it was suggested to use
ComplexPattern, so given:

bool XXXDAGToDAGISel::SelectConstantFPSDNodeImmZero(SDValue In, SDValue
&Src) const {
  if (ConstantFPSDNode *C = dyn_cast<ConstantFPSDNode>(In))
    return C->isZero();
  return false;
}

def ConstantFPSDNodeImmZero : ComplexPattern<f32, 0,
"SelectConstantFPSDNodeImmZero">;

def : XXXPat<(v4f32 (int_foo i32:$dmask, f32:$s, (f32
(ConstantFPSDNodeImmZero f32:$lod)), v8i32:$rsrc, v4i32:$sampler,
i1:$unorm, 0, i32:$cachepolicy)), (FOO_MI (COPY_TO_REGCLASS ?:$s,
32RegClass), ?:$rsrc, ?:$sampler, (as_i32imm ?:$dmask), (as_i1imm
?:$unorm), (as_i1imm ?:$cachepolicy), (as_i1imm ?:$cachepolicy), 0, 0, 0, {
0 })>;


The problem here is that lod is that 'pattern has dead named input lod'.
I
removed the 'lod' but then I get:

error: no matching function for call to
‘{anonymous}::XXXDAGToDAGISel::SelectConstantFPSDNodeImmZero(llvm::SDValue&)’
   return SelectConstantFPSDNodeImmZero(N);

which makes sense, the Select function needs an input to check, which I
believe I was calling 'lod' and sending as the input param. It seems
like
LLVM doesn't llke a variable used in the pattern to match that isn't
then
also used in the output MI, which sort of seems quite limiting honestly but
I suppose this wouldn't be seen if 'lod' was an int and not a float.
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On 6/7/2018 10:45 AM, Ryan Taylor via llvm-dev wrote:
> I'm trying to match a ConstantFPSDNode == 0 in dag pattern for 
> tablegen but am having some issues.
>
> So LLVM doesn't seem to accept a floating point constant literal match 
> like:
>
> %v = call <4 x float> @foo(i32 15, float %s, float 0.0, <8 x
i32>
> %rsrc, <4 x i32> %samp, i1 0, i32 0, i32 0)
>   ret <4 x float> %v
>
> def : XXXPat<(v4f32 (int_foo i32:$mask, f32:$s, 0, v8i32:$rsrc, 
> v4i32:$sampler, i1:$unorm, 0, i32:$cachepolicy)), (FOO_MI 
> (COPY_TO_REGCLASS ?:$s, 32RegClass), ?:$rsrc, ?:$sampler, (as_i32imm 
> ?:$mask), (as_i1imm ?:$unorm), (as_i1imm ?:$cachepolicy), (as_i1imm 
> ?:$cachepolicy), 0, 0, 0, { 0 })>;
>
> which would be ideal. This seems to be because OPC_CheckInteger only 
> checks for ConstantSDNode and not ConstantFPSDNode. So it was 
> suggested to use ComplexPattern, so given:
>
> bool XXXDAGToDAGISel::SelectConstantFPSDNodeImmZero(SDValue In, 
> SDValue &Src) const {
>   if (ConstantFPSDNode *C = dyn_cast<ConstantFPSDNode>(In))
>     return C->isZero();
>   return false;
> }
>
> def ConstantFPSDNodeImmZero : ComplexPattern<f32, 0, 
> "SelectConstantFPSDNodeImmZero">;
>
> def : XXXPat<(v4f32 (int_foo i32:$dmask, f32:$s, (f32 
> (ConstantFPSDNodeImmZero f32:$lod)), v8i32:$rsrc, v4i32:$sampler, 
> i1:$unorm, 0, i32:$cachepolicy)), (FOO_MI (COPY_TO_REGCLASS ?:$s, 
> 32RegClass), ?:$rsrc, ?:$sampler, (as_i32imm ?:$dmask), (as_i1imm 
> ?:$unorm), (as_i1imm ?:$cachepolicy), (as_i1imm ?:$cachepolicy), 0, 0, 
> 0, { 0 })>;
This isn't right; an floating-point immediate doesn't have any inputs.

A bunch of backends have a pattern like this; grep for fpimm0.

-Eli

-- 
Employee of Qualcomm Innovation Center, Inc.
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux
Foundation Collaborative Project

Eli,

 Ok, thanks, this makes more sense.



On Thu, Jun 7, 2018 at 2:17 PM, Friedman, Eli <efriedma at codeaurora.org>
wrote:
> On 6/7/2018 10:45 AM, Ryan Taylor via llvm-dev wrote:
>
>> I'm trying to match a ConstantFPSDNode == 0 in dag pattern for
tablegen
>> but am having some issues.
>>
>> So LLVM doesn't seem to accept a floating point constant literal
match
>> like:
>>
>> %v = call <4 x float> @foo(i32 15, float %s, float 0.0, <8 x
i32> %rsrc,
>> <4 x i32> %samp, i1 0, i32 0, i32 0)
>>   ret <4 x float> %v
>>
>> def : XXXPat<(v4f32 (int_foo i32:$mask, f32:$s, 0, v8i32:$rsrc,
>> v4i32:$sampler, i1:$unorm, 0, i32:$cachepolicy)), (FOO_MI
(COPY_TO_REGCLASS
>> ?:$s, 32RegClass), ?:$rsrc, ?:$sampler, (as_i32imm ?:$mask), (as_i1imm
>> ?:$unorm), (as_i1imm ?:$cachepolicy), (as_i1imm ?:$cachepolicy), 0, 0,
0, {
>> 0 })>;
>>
>> which would be ideal. This seems to be because OPC_CheckInteger only
>> checks for ConstantSDNode and not ConstantFPSDNode. So it was suggested
to
>> use ComplexPattern, so given:
>>
>> bool XXXDAGToDAGISel::SelectConstantFPSDNodeImmZero(SDValue In, SDValue
>> &Src) const {
>>   if (ConstantFPSDNode *C = dyn_cast<ConstantFPSDNode>(In))
>>     return C->isZero();
>>   return false;
>> }
>>
>> def ConstantFPSDNodeImmZero : ComplexPattern<f32, 0,
>> "SelectConstantFPSDNodeImmZero">;
>>
>> def : XXXPat<(v4f32 (int_foo i32:$dmask, f32:$s, (f32
>> (ConstantFPSDNodeImmZero f32:$lod)), v8i32:$rsrc, v4i32:$sampler,
>> i1:$unorm, 0, i32:$cachepolicy)), (FOO_MI (COPY_TO_REGCLASS ?:$s,
>> 32RegClass), ?:$rsrc, ?:$sampler, (as_i32imm ?:$dmask), (as_i1imm
>> ?:$unorm), (as_i1imm ?:$cachepolicy), (as_i1imm ?:$cachepolicy), 0, 0,
0, {
>> 0 })>;
>>
>
> This isn't right; an floating-point immediate doesn't have any
inputs.
>
> A bunch of backends have a pattern like this; grep for fpimm0.
>
> -Eli
>
> --
> Employee of Qualcomm Innovation Center, Inc.
> Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux
> Foundation Collaborative Project
>
>
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