================
@@ -148,6 +148,29 @@ template <typename T> constexpr T ldexp_impl(T X, T Exp) {
return exp2(Exp) * X;
}
+template <typename T, int BitWidth> constexpr uint firstbithigh_impl(T X) {
+ uint FBH = __builtin_hlsl_elementwise_firstbithigh(X);
+#if defined(__DIRECTX__)
+ // The firstbithigh DXIL ops count bits from the wrong side, so we need to
+ // invert it for DirectX.
+ uint Inversion = (BitWidth - 1) - FBH;
+ FBH = select(FBH == -1, FBH, Inversion);
+#endif
+ return FBH;
+}
+
+template <typename T, int N, int BitWidth>
+constexpr vector<uint, N> firstbithigh_impl(vector<T, N> X) {
----------------
Icohedron wrote:
Perhaps I could do something like this:
```hlsl
template <typename K, typename T, int BitWidth> constexpr uint
firstbithigh_impl(T X) {
K FBH = __builtin_hlsl_elementwise_firstbithigh(X);
#if defined(__DIRECTX__)
// The firstbithigh DXIL ops count bits from the wrong side, so we need to
// invert it for DirectX.
K Inversion = (BitWidth - 1) - FBH;
FBH = select(FBH == -1, FBH, Inversion);
#endif
return FBH;
}
```
and call it like so:
```hlsl
template <typename T, int N>
const inline __detail::enable_if_t<__detail::is_same<int64_t, T>::value ||
__detail::is_same<uint64_t, T>::value,
vector<uint, N>>
firstbithigh(vector<T, N> X) {
return __detail::firstbithigh_impl<vector<uint, N>, vector<T, N>, 64>(X);
}
```
https://github.com/llvm/llvm-project/pull/166419
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