refactoring ConstantTensorDescriptor

[ROCm/composable_kernel commit: a0584426ff]

src/include/functional.hip.hpp

@@ -0,0 +1,49 @@
+#pragma once
+#include "constant_integral.hip.hpp"
+
+template <unsigned NLoop>
+struct static_loop_n
+{
+    template <class F>
+    __host__ __device__ void operator()(F f) const
+    {
+        static_assert(NLoop > 1, "out-of-range");
+
+        f(Number<NLoop - 1>{});
+        static_loop_n<NLoop - 1>{}(f);
+    }
+};
+
+template <>
+struct static_loop_n<1>
+{
+    template <class F>
+    __host__ __device__ void operator()(F f) const
+    {
+        f(Number<0>{});
+    }
+};
+
+template <unsigned NLoop>
+struct static_const_reduce_n
+{
+    template <class F, class Reduce>
+    __host__ __device__ constexpr auto operator()(F f, Reduce r) const
+    {
+        static_assert(NLoop > 1, "out-of-range");
+
+        constexpr auto a = f(Number<NLoop - 1>{});
+        auto b = static_const_reduce_n<NLoop - 1>{}(f, r); // cannot use constexpr here, weird
+        return r(a, b);
+    }
+};
+
+template <>
+struct static_const_reduce_n<1>
+{
+    template <class F, class Reduce>
+    __host__ __device__ constexpr auto operator()(F f, Reduce) const
+    {
+        return f(Number<0>{});
+    }
+};