[clang] [HLSL] Implement the `lit` intrinsic (PR #134171)

[Farzon Lotfi via cfe-commits]

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@@ -280,6 +280,22 @@ constexpr bool4 isinf(double4 V) { return isinf((float4)V); }
 _DXC_COMPAT_TERNARY_DOUBLE_OVERLOADS(lerp)
 _DXC_COMPAT_TERNARY_INTEGER_OVERLOADS(lerp)
 
+//===----------------------------------------------------------------------===//
+// lit builtins overloads
+//===----------------------------------------------------------------------===//
+
+template <typename T>
+constexpr __detail::enable_if_t<__detail::is_arithmetic<T>::Value &&
+                                    (__detail::is_same<double, T>::value ||
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farzonl wrote:

> If we have to do templates can we instead do template type specializations. That should be more exclusive and then your catch all template would be the cast to float case.

Hmm on second thought maybe that prevents the is arithmetic stuff.

https://github.com/llvm/llvm-project/pull/134171