[clang] [llvm] [HLSL] Handle WaveActiveBallot struct return type appropriately (PR #175105)

[Finn Plummer via cfe-commits]

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@@ -5058,7 +5058,7 @@ def HLSLWaveActiveAnyTrue : LangBuiltin<"HLSL_LANG"> {
 def HLSLWaveActiveBallot : LangBuiltin<"HLSL_LANG"> {
   let Spellings = ["__builtin_hlsl_wave_active_ballot"];
   let Attributes = [NoThrow, Const];
-  let Prototype = "_ExtVector<4, unsigned int>(bool)";
+  let Prototype = "void(bool)";
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inbelic wrote:

https://learn.microsoft.com/en-us/windows/win32/direct3dhlsl/waveballot seems to indicate that the built-in should be a uint4.

Should it instead be a uint4 and only change to the custom type during lowering to the dxil ops?

https://github.com/llvm/llvm-project/pull/175105