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Optimizations of log2 for ivec4

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This commit is contained in:
Christophe Riccio
2014-11-24 01:56:36 +01:00
parent 117634c7ea
commit e8fbcf76dd
5 changed files with 171 additions and 40 deletions
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36
glm/gtc/integer.inl
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@@ -29,19 +29,35 @@
namespace glm{
namespace detail
{
GLM_FUNC_QUALIFIER unsigned int nlz(unsigned int x)
template <typename T, precision P, template <class, precision> class vecType>
struct compute_log2<T, P, vecType, false>
{
return 31u - findMSB(x);
}
template <>
struct compute_log2<false>
{
template <typename T>
GLM_FUNC_QUALIFIER T operator() (T const & Value) const
GLM_FUNC_QUALIFIER static vecType<T, P> call(vecType<T, P> const & vec)
{
return Value <= static_cast<T>(1) ? T(0) : T(32) - nlz(Value - T(1));
//Equivalent to return findMSB(vec); but save one function call in ASM with VC
//return findMSB(vec);
return detail::compute_findMSB_vec<T, P, vecType, sizeof(T) * 8>::call(vec);
}
};
# if(GLM_ARCH != GLM_ARCH_PURE) && (GLM_COMPILER & (GLM_COMPILER_VC | GLM_COMPILER_APPLE_CLANG | GLM_COMPILER_LLVM))
template <precision P>
struct compute_log2<int, P, tvec4, false>
{
GLM_FUNC_QUALIFIER static tvec4<int, P> call(tvec4<int, P> const & vec)
{
tvec4<int, P> Result(glm::uninitialize);
_BitScanReverse(reinterpret_cast<unsigned long*>(&Result.x), vec.x);
_BitScanReverse(reinterpret_cast<unsigned long*>(&Result.y), vec.y);
_BitScanReverse(reinterpret_cast<unsigned long*>(&Result.z), vec.z);
_BitScanReverse(reinterpret_cast<unsigned long*>(&Result.w), vec.w);
return Result;
}
};
# endif//GLM_ARCH != GLM_ARCH_PURE
}//namespace detail
}//namespace glm