[clang] [llvm] [HLSL] Implement `WaveReadLaneAt` intrinsic (PR #111010)

[Farzon Lotfi via cfe-commits]

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@@ -83,6 +83,7 @@ def int_dx_umad : DefaultAttrsIntrinsic<[llvm_anyint_ty], [LLVMMatchType<0>, LLV
 def int_dx_normalize : DefaultAttrsIntrinsic<[LLVMMatchType<0>], [llvm_anyfloat_ty], [IntrNoMem]>;
 def int_dx_rsqrt  : DefaultAttrsIntrinsic<[llvm_anyfloat_ty], [LLVMMatchType<0>], [IntrNoMem]>;
 def int_dx_wave_is_first_lane : DefaultAttrsIntrinsic<[llvm_i1_ty], [], [IntrConvergent]>;
+def int_dx_wave_read_lane_at : DefaultAttrsIntrinsic<[llvm_any_ty], [LLVMMatchType<0>, llvm_i32_ty], [IntrConvergent]>;
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farzonl wrote:

I see `int_dx_wave_is_first_lane` doesn't have `IntrNoMem` either but I know `IntrNoMem` was required to scalarize other intrinsics and this is an intrinsic we want to scalarize. Is the `IntrConvergent` attribute sufficient?

https://github.com/llvm/llvm-project/pull/111010