[clang] [llvm] [HLSL] [DXIL] Implement the `AddUint64` HLSL function and the `UAddc` DXIL op (PR #125319)

[Finn Plummer via llvm-commits]

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+; RUN: not opt -S -dxil-op-lower -mtriple=dxil-pc-shadermodel6.3-library %s 2>&1 | FileCheck %s
+
+; DXIL operation UAddc only supports i32. Other integer types are unsupported.
+; CHECK: in function uaddc_i16
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inbelic wrote:

nit: I think LLVM ERROR will also be output here which we can use to be more explicit that this is an error

https://github.com/llvm/llvm-project/pull/125319