[clang] [SYCL][SPIR-V][Windows] Extend BaseSPIRTargetInfo host-adaptation for Windows support (PR #208196)

[Michele Scandale via cfe-commits]

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michele-scandale wrote:

I did notice the issue on the first command line where `aux-triple` is `x86_64-unknown-linux-gnu`.
In there you can clearly see that there is an issue since `VAListAddr.getElementType()->dump()` at the entry of `emitVoidPtrDirectVAArg ` produces `%struct.__va_list_tag = type { i32, i32, ptr addrspace(4), ptr addrspace(4) }`.

> We could modify SPIRVABIInfo::EmitVAArg() ([here](https://github.com/llvm/llvm-project/blob/6fd0aae1d6f59bf0b0b1fdbdbf217ccb6662d32c/clang/lib/CodeGen/Targets/SPIR.cpp#L204-L210)) to implement target (and auxiliary target) dependent behavior. I think that would be inline with what you are suggesting.

Yes, that's would make sense to me. In this change the SPIRV target properties are adjusted based on the host-target ones, so altering the SPIRV codegen behavior for the `va_arg` case to match the host-target one seems ok

https://github.com/llvm/llvm-project/pull/208196