From 4bcb2c4fb394da03858fa78d1a36ae3fbc169bb2 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=D0=91=D1=80=D0=B0=D0=BD=D0=B8=D0=BC=D0=B8=D1=80=20=D0=9A?=
 =?UTF-8?q?=D0=B0=D1=80=D0=B0=D1=9F=D0=B8=D1=9B?=
 <branimirkaradzic@gmail.com>
Date: Tue, 22 Oct 2019 19:29:51 -0700
Subject: [PATCH] Added integer version of log2.

---
 include/bx/inline/math.inl |  8 ++++++++
 include/bx/math.h          |  3 ++-
 tests/math_test.cpp        | 27 +++++++++++++++++++++++++++
 3 files changed, 37 insertions(+), 1 deletion(-)

diff --git a/include/bx/inline/math.inl b/include/bx/inline/math.inl
index 81ce759..72e4ef2 100644
--- a/include/bx/inline/math.inl
+++ b/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);
diff --git a/include/bx/math.h b/include/bx/math.h
index 6e28839..a46ab0d 100644
--- a/include/bx/math.h
+++ b/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.
 	///
diff --git a/tests/math_test.cpp b/tests/math_test.cpp
index 84bec2c..00a73b2 100644
--- a/tests/math_test.cpp
+++ b/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", "")