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

[Finn Plummer via cfe-commits]

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@@ -87,6 +87,7 @@ class CGHLSLRuntime {
   GENERATE_HLSL_INTRINSIC_FUNCTION(SDot, sdot)
   GENERATE_HLSL_INTRINSIC_FUNCTION(UDot, udot)
   GENERATE_HLSL_INTRINSIC_FUNCTION(WaveIsFirstLane, wave_is_first_lane)
+  GENERATE_HLSL_INTRINSIC_FUNCTION(WaveReadLaneAt, waveReadLaneAt)
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inbelic wrote:

If we use `_` separated then the generated names will use `.` to separate them. So eg `wave_read_lane_at` becomes `llvm.dx.wave.read.lane.at`. Which we decided was quite confusing due to the confusion with a namespace. I will clean up the other intrinsic to cohere to this in a follow up pr.

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