Added integer version of log2.

include/bx/inline/math.inl

@@ -10,6 +10,7 @@
 #endif // BX_MATH_H_HEADER_GUARD
 
 #include <bx/simd_t.h>
+#include <bx/uint32_t.h>
 
 namespace bx
 {
@@ -191,11 +192,18 @@ namespace bx
 		return pow(2.0f, _a);
 	}
 
+	template<>
 	inline BX_CONST_FUNC float log2(float _a)
 	{
 		return log(_a) * kInvLogNat2;
 	}
 
+	template<>
+	inline BX_CONST_FUNC int32_t log2(int32_t _a)
+	{
+		return 31 - uint32_cntlz(_a);
+	}
+
 	inline BX_CONST_FUNC float rsqrtRef(float _a)
 	{
 		return pow(_a, -0.5f);

include/bx/math.h

@@ -225,7 +225,8 @@ namespace bx
 
 	/// Returns the base 2 logarithm of _a.
 	///
-	BX_CONST_FUNC float log2(float _a);
+	template<typename Ty>
+	BX_CONST_FUNC Ty log2(Ty _a);
 
 	/// Returns the square root of _a.
 	///

tests/math_test.cpp

@@ -31,6 +31,33 @@ TEST_CASE("log2", "")
 {
 	log2_test(0.0f);
 	log2_test(256.0f);
+
+	REQUIRE(0.0f == bx::log2(1.0f) );
+	REQUIRE(0 == bx::log2(1) );
+
+	REQUIRE(1.0f == bx::log2(2.0f) );
+	REQUIRE(1 == bx::log2(2) );
+
+	REQUIRE(2.0f == bx::log2(4.0f) );
+	REQUIRE(2 == bx::log2(4) );
+
+	REQUIRE(3.0f == bx::log2(8.0f) );
+	REQUIRE(3 == bx::log2(8) );
+
+	REQUIRE(4.0f == bx::log2(16.0f) );
+	REQUIRE(4 == bx::log2(16) );
+
+	REQUIRE(5.0f == bx::log2(32.0f) );
+	REQUIRE(5 == bx::log2(32) );
+
+	REQUIRE(6.0f == bx::log2(64.0f) );
+	REQUIRE(6 == bx::log2(64) );
+
+	REQUIRE(7.0f == bx::log2(128.0f) );
+	REQUIRE(7 == bx::log2(128) );
+
+	REQUIRE(8.0f == bx::log2(256.0f) );
+	REQUIRE(8 == bx::log2(256) );
 }
 
 TEST_CASE("libm", "")