From c004d95bdf123e38d22f4a47690ac050f6925a03 Mon Sep 17 00:00:00 2001
From: Christophe Riccio <mail@g-truc.net>
Date: Thu, 13 Oct 2011 18:59:25 +0100
Subject: [PATCH 1/2] Added log2 meta programming implementation

---
 glm/core/func_exponential.inl | 28 +++++++++++++++++++++++++---
 1 file changed, 25 insertions(+), 3 deletions(-)

diff --git a/glm/core/func_exponential.inl b/glm/core/func_exponential.inl
index c8c385f7..c1ffee92 100644
--- a/glm/core/func_exponential.inl
+++ b/glm/core/func_exponential.inl
@@ -224,6 +224,30 @@ namespace glm
             exp2(x.w));
     }
 
+namespace detail
+{
+	template <int PATH = float_or_int_value::ERROR>
+	struct compute_log2
+	{
+		template <typename T>
+		T operator() (T const & Value) const
+		{
+			static_assert(0, "'log2' parameter has an invalid template parameter type");
+			return Value;
+		}
+	};
+
+	template <>
+	struct compute_log2<float_or_int_value::FLOAT>
+	{
+		template <typename T>
+		T operator() (T const & Value) const
+		{
+			return ::std::log(Value) / T(0.69314718055994530941723212145818);
+		}
+	};
+}//namespace detail
+
     // log2, ln2 = 0.69314718055994530941723212145818f
     template <typename genType>
     GLM_FUNC_QUALIFIER genType log2
@@ -231,9 +255,7 @@ namespace glm
 		genType const & x
 	)
     {
-		GLM_STATIC_ASSERT(detail::type<genType>::is_float, "'log2' only accept floating-point input");
-
-        return ::std::log(x) / genType(0.69314718055994530941723212145818);
+		return detail::compute_log2<detail::float_or_int_trait<genType>::ID>()(x);
     }
 
     template <typename T>

From 742013f6d3ad8ad0af80d4e7ca49274a465b5517 Mon Sep 17 00:00:00 2001
From: Christophe Riccio <mail@g-truc.net>
Date: Thu, 13 Oct 2011 19:07:54 +0100
Subject: [PATCH 2/2] Added integer log2 implementation with compute_log2 class

---
 glm/gtx/integer.hpp |  3 ++-
 glm/gtx/integer.inl | 24 +++++++++++-------------
 2 files changed, 13 insertions(+), 14 deletions(-)

diff --git a/glm/gtx/integer.hpp b/glm/gtx/integer.hpp
index b33d7ea6..e0f10dcf 100644
--- a/glm/gtx/integer.hpp
+++ b/glm/gtx/integer.hpp
@@ -60,7 +60,8 @@ namespace glm
 
 	//! Returns the log2 of x. Can be reliably using to compute mipmap count from the texture size.
 	//! From GLM_GTX_integer extension.
-	unsigned int log2(unsigned int x);
+	template <typename genType>
+	genType log2(genType const & x);
 
 	//! Returns the floor log2 of x.
 	//! From GLM_GTX_integer extension.
diff --git a/glm/gtx/integer.inl b/glm/gtx/integer.inl
index e8be0e41..ecb4ac9c 100644
--- a/glm/gtx/integer.inl
+++ b/glm/gtx/integer.inl
@@ -53,23 +53,21 @@ namespace detail
 		x += (x >> 16);
 		return(x & 0x0000003f);
 	}
-}//namespace detail
 
+	template <>
+	struct compute_log2<float_or_int_value::INT>
+	{
+		template <typename T>
+		T operator() (T const & Value) const
+		{
 #if(GLM_COMPILER & (GLM_COMPILER_VC | GLM_COMPILER_GCC))
-
-GLM_FUNC_QUALIFIER unsigned int log2(unsigned int x)
-{
-	return x <= 1 ? 0 : unsigned(32) - nlz(x - 1u);
-}
-
+			return Value <= T(1) ? T(0) : T(32) - nlz(Value - T(1));
 #else
-
-GLM_FUNC_QUALIFIER unsigned int log2(unsigned int x)
-{
-	return unsigned(32) - nlz(x - 1u);
-}
-
+			return T(32) - nlz(Value - T(1));
 #endif
+		}
+	};
+}//namespace detail
 
 // Henry Gordon Dietz: http://aggregate.org/MAGIC/
 unsigned int floor_log2(unsigned int x)