[llvm-dev] creating Intrinsic DAG Node
Ryan Taylor via llvm-dev
llvm-dev at lists.llvm.org
Tue Feb 2 09:44:21 PST 2016
Thanks for the response. Is there an example in the code somewhere of
doing the intrinsic ID method? I don't need to put it a lot of places so
I'm not sure it warrants adding a node.
On Tue, Feb 2, 2016 at 12:35 PM, Matt Arsenault <arsenm2 at gmail.com> wrote:
> > On Feb 2, 2016, at 09:29, Ryan Taylor via llvm-dev <
> llvm-dev at lists.llvm.org> wrote:
> > I'm trying to 'lower' an operation that needs to create a node in the SD
> that is an intrinsic call.... what is the best way to do this?
> > I see in the DAGBuilder it calls 'setValue' which adds to the map
> NodeMap[V] where V is the key and the passed in SDValue is the value but
> I'm not sure this is a good way to do it since these are local to
> SelectionDAGBuilder and the lowering needs to happen in XXXISelLowering.cpp.
> > Thanks.
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> SelectionDAGBuilder creates INTRINSIC_W_CHAIN, INTRINSIC_WO_CHAIN, or
> INTRINSIC_VOID nodes. You want to emit those with the intrinsic ID as a
> TargetConstant the first operand (or second with chains). I would recommend
> though for these cases, if you want to emit emit them in the backend, it’s
> a bit nicer to lower these to a custom node, and select on that. It’s a bit
> nicer than having to add the intrinsic ID everywhere. Most of the AMDGPU
> intrinsics are handled this way.
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