[llvm-dev] creating Intrinsic DAG Node

[Ryan Taylor via llvm-dev]

given the following C code:

float b=16, a=0;
int main() {
   float a = sqrt(b);
   return0;
}

I'm trying to lower FSQRT down, but getting a casting issue, my code is:

SDValue XXXLowering::LowerFSQRT(SDValue Op, SelectionDAG &DAG) const {
   SDLoc DL(Op);
   EVT VT = Op.getValueType();
   SDValue LHS = Op.getOperand(0);

   SDValue newNode = DAG.getNode(ISD::INTRINSIC_WO_CHAIN, DL, VT,
DAG.getTargetConstantFP(Intrinsic::my_intrinsic, DL, VT), LHS);
   return newNode;
}

The error I'm getting is: Assertion 'isa<X>(Val) && "cast<Ty>() argument of
incompatible type!"

Is this the correct way to add intrinsic dag node?

Thanks.


On Tue, Feb 2, 2016 at 5:10 PM, Ryan Taylor <ryta1203 at gmail.com> wrote:

> Matt,
>
>   The added intrinsic in DAG looks like:
>
> 0xbedb698: i32 = llvm.MyIntrinsic 0xbedb200, 0xbedac18 [ORD=4]
>
>   The builtin in DAG looks like:
>
> 0xbedb2a8: i32,ch = llvm 0xbedb158:1, 0xbedb200, 0xbedb158 [ORD=7] [ID=16]
>
>    The only difference I'm seeing is the extra operand, which is a 'ch'
> from a load.
>
> On Tue, Feb 2, 2016 at 3:55 PM, Matt Arsenault <arsenm2 at gmail.com> wrote:
>
>>
>> > On Feb 2, 2016, at 12:43, Ryan Taylor <ryta1203 at gmail.com> wrote:
>> >
>> > Matt,
>> >
>> >   This seems to generate llvm.my_intrinsic just fine in the DAG, so no
>> DAG errors; however, it won't match. For example, if I call the intrinsic
>> from C, the DAG node looks to be named the same in dotty file but it won't
>> match... am I missing something?
>> >
>> >   I've done it exactly the way it was done above. The DAG looks great
>> but it won't match. Did I miss something?
>> >
>> > Thanks.
>> >
>>
>> Are you using the right intrinsic type? Does it have a chain or result?
>>
>> How are you calling it from C? Are you declaring the intrinsic? This can
>> fail if you mismatched the readnone or readonly to the actual intrinsic
>> definition
>>
>>
>
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