Duplicate symbols - getGenOpMix<ONNXRoundOp> - on Windows builds

[mschofie]

I'm trying to get onnx-mlir building on Windows, using Visual Studio 2022. I've worked through a few issues - see PR3253 - but this issue is something that I'd need guidance on, since I'm not familiar with the code.

getGenOpMix<> is a function template declared in src/Conversion/ONNXToKrnl/ONNXToKrnlCommon.hpp. src/Conversion/ONNXToKrnl/Quantization/QuantizeLinear.cpp calls the getGenOpMix<ONNXRoundOp> which will instantiate the template. src\Conversion\ONNXToKrnl\Math\Elementwise.cpp provides an explicit specialization of getGenOpMix<ONNXRoundOp> (here), and MSVC logs a warning:

warning LNK4006: "class llvm::SmallDenseMap<enum onnx_mlir::GenericOps,__int64,8,struct llvm::DenseMapInfo<enum onnx_mlir::GenericOps,void>,struct llvm::detail::DenseMapPair<enum onnx_mlir::GenericOps,__int64> > __cdecl onnx_mlir::getGenOpMix<class mlir::ONNXRoundOp>(class mlir::Type,class mlir::Operation *)" (??$getGenOpMix@VONNXRoundOp@mlir@@@onnx_mlir@@YA?AV?$SmallDenseMap@W4GenericOps@onnx_mlir@@_J$07U?$DenseMapInfo@W4GenericOps@onnx_mlir@@X@llvm@@U?$DenseMapPair@W4GenericOps@onnx_mlir@@_J@detail@4@@llvm@@VType@mlir@@PEAVOperation@4@@Z) already defined in QuantizeLinear.cpp.obj; second definition ignored

So MSVC is dropping one of the definitions on the floor - which one it picks is not defined. Any guidance as to whether both consumers should use the explicit specialization, or should only Elementwise.cpp use the explicit specialization?