Create algorithm.hlsl

Author: devshgraphicsprogramming

include/nbl/builtin/hlsl/algorithm.hlsl

@@ -0,0 +1,153 @@
+// Copyright (C) 2022 - DevSH Graphics Programming Sp. z O.O.
+// This file is part of the "Nabla Engine".
+// For conditions of distribution and use, see copyright notice in nabla.h
+#ifndef _NBL_BUILTIN_HLSL_ALGORITHM_INCLUDED_
+#define _NBL_BUILTIN_HLSL_ALGORITHM_INCLUDED_
+
+namespace nbl
+{
+namespace hlsl
+{
+
+
+namespace impl
+{
+
+// TODO: move this to some other header
+bool isNPoT(const uint x)
+{
+    return x&(x-1);
+}
+
+template<class Accessor, class Comparator>
+struct bound_t
+{
+    static bound_t<Accessor,Comparator> setup(uint begin, const uint end, const typename Accessor::value_type _value, const Comparator _comp)
+    {
+        bound_t<Accessor,Comparator> retval;
+        retval.comp = _comp;
+        retval.value = _value;
+        retval.it = begin;
+        retval.len = end-begin;
+        return retval;
+    }
+
+
+    uint operator()(inout Accessor accessor)
+    {
+        if (isNPoT(len))
+        {
+            const uint newLen = 0x1u<<firstbithigh(len);
+            const uint testPoint = it+(len-newLen);
+            len = newLen;
+            comp_step(accessor,testPoint);
+        }
+        while (len)
+        {
+            // could unroll 3 times or more
+            iteration(accessor);
+            iteration(accessor);
+        }
+        comp_step(accessor,it,it+1u);
+        return it;
+    }
+
+    void iteration(inout Accessor accessor)
+    {
+        len >>= 1;
+        const uint mid = it+len;
+        comp_step(accessor,mid);
+    }
+
+    void comp_step(inout Accessor accessor, const uint testPoint, const uint rightBegin)
+    {
+        if (comp(accessor[testPoint],value))
+            it = rightBegin;
+    }
+    void comp_step(inout Accessor accessor, const uint testPoint)
+    {
+        comp_step(accessor,testPoint,testPoint);
+    }
+
+    Comparator comp;
+    typename Accessor::value_type value;
+    uint it;
+    uint len;
+};
+
+template<class Accessor, class Comparator>
+struct lower_to_upper_comparator_transform_t
+{
+    bool operator()(const typename Accessor::value_type lhs, const typename Accessor::value_type rhs)
+    {
+        return !comp(rhs,lhs);
+    }
+
+    Comparator comp;
+};
+
+}
+
+
+template<class Accessor, class Comparator>
+uint lower_bound(inout Accessor accessor, const uint begin, const uint end, const typename Accessor::value_type value, const Comparator comp)
+{
+    impl::bound_t<Accessor,Comparator> implementation = impl::bound_t<Accessor,Comparator>::setup(begin,end,value,comp);
+    return implementation(accessor);
+}
+
+template<class Accessor, class Comparator>
+uint upper_bound(inout Accessor accessor, const uint begin, const uint end, const typename Accessor::value_type value, const Comparator comp)
+{
+    using TransformedComparator = impl::lower_to_upper_comparator_transform_t<Accessor,Comparator>;
+    TransformedComparator transformedComparator;
+    transformedComparator.comp = comp;
+    return lower_bound<Accessor,TransformedComparator>(accessor,begin,end,value,transformedComparator);
+}
+
+
+namespace impl
+{
+
+template<typename T>
+struct comparator_lt_t
+{
+    bool operator()(const T lhs, const T rhs)
+    {
+        return lhs<rhs;
+    }
+};
+
+// extra indirection due to https://github.com/microsoft/DirectXShaderCompiler/issues/4771
+template<class Accessor, typename T>
+uint lower_bound(inout Accessor accessor, const uint begin, const uint end, const T value)
+{
+    using Comparator = impl::comparator_lt_t<T>;
+    Comparator comp;
+    return nbl::hlsl::lower_bound<Accessor,Comparator>(accessor,begin,end,value,comp);
+}
+template<class Accessor, typename T>
+uint upper_bound(inout Accessor accessor, const uint begin, const uint end, const T value)
+{
+    using Comparator = impl::comparator_lt_t<T>;
+    Comparator comp;
+    return nbl::hlsl::upper_bound<Accessor,Comparator>(accessor,begin,end,value,comp);
+}
+
+}
+
+template<class Accessor>
+uint lower_bound(inout Accessor accessor, const uint begin, const uint end, const typename Accessor::value_type value)
+{
+    return impl::lower_bound<Accessor,typename Accessor::value_type>(accessor,begin,end,value);
+}
+template<class Accessor>
+uint upper_bound(inout Accessor accessor, const uint begin, const uint end, const typename Accessor::value_type value)
+{
+    return impl::upper_bound<Accessor,typename Accessor::value_type>(accessor,begin,end,value);
+}
+
+}
+}
+
+#endif