[llvm-branch-commits] [DirectX] Lower `@llvm.dx.typedBufferLoad` to DXIL ops (PR #104252)

[Justin Bogner via llvm-branch-commits]

https://github.com/bogner created https://github.com/llvm/llvm-project/pull/104252

The `@llvm.dx.typedBufferLoad` intrinsic is lowered to `@dx.op.bufferLoad`.
There's some complexity here due to translating from a vector return type to a
named struct and trying to avoid excessive IR coming out of that.

Note that this change includes a bit of a hack in how it deals with
`getOverloadKind` for the `dx.ResRet` types - we need to adjust how we deal
with operation overloads to generate a table directly rather than proxy through
the OverloadKind enum, but that's left for a later change here.