Replaces ceil_log2 by std::bit_width

Also removes unused floor_log2.

source/lib/bits.cpp

@@ -1,47 +0,0 @@
-/* Copyright (C) 2025 Wildfire Games.
- *
- * Permission is hereby granted, free of charge, to any person obtaining
- * a copy of this software and associated documentation files (the
- * "Software"), to deal in the Software without restriction, including
- * without limitation the rights to use, copy, modify, merge, publish,
- * distribute, sublicense, and/or sell copies of the Software, and to
- * permit persons to whom the Software is furnished to do so, subject to
- * the following conditions:
- *
- * The above copyright notice and this permission notice shall be included
- * in all copies or substantial portions of the Software.
- *
- * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
- * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
- * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
- * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
- * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
- * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
- * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
- */
-
-/*
- * bit-twiddling.
- */
-
-#include "precompiled.h"
-
-#include "bits.h"
-
-#include "lib/types.h"
-
-#include <cstring>
-
-static inline u32 get_float_bits(const float x)
-{
-	u32 ret;
-	memcpy(&ret, &x, 4);
-	return ret;
-}
-
-int floor_log2(const float x)
-{
-	const u32 i = get_float_bits(x);
-	const u32 biased_exp = (i >> 23) & 0xFF;
-	return (int)biased_exp - 127;
-}

source/lib/bits.h

@@ -143,58 +143,6 @@ inline T ClearLeastSignificantBit(T x)
 	return x & (x-1);
 }
 
-
-/**
- * ceil(log2(x))
- *
- * @param x (unsigned integer)
- * @return ceiling of the base-2 logarithm (i.e. rounded up) or
- * zero if the input is zero.
- **/
-template<typename T>
-inline size_t ceil_log2(T x)
-{
-	T bit = 1;
-	size_t log = 0;
-	while(bit < x && bit != 0)	// must detect overflow
-	{
-		log++;
-		bit *= 2;
-	}
-
-	return log;
-}
-
-// compile-time variant of the above
-template<size_t N>
-struct CeilLog2
-{
-	enum { value = 1 + CeilLog2<(N+1)/2>::value };
-};
-
-template<>
-struct CeilLog2<1>
-{
-	enum { value = 0 };
-};
-
-template<>
-struct CeilLog2<0>
-{
-	enum { value = 0 };
-};
-
-
-
-/**
- * floor(log2(f))
- * fast, uses the FPU normalization hardware.
- *
- * @param x (float) input; MUST be > 0, else results are undefined.
- * @return floor of the base-2 logarithm (i.e. rounded down).
- **/
-extern int floor_log2(const float x);
-
 /**
  * round number up/down to the next given multiple.
  *

source/lib/tests/test_bits.h

@@ -85,22 +85,6 @@ public:
 		EQUALS(bits<u64>(0xA5A5A5A5A5A5A5A5ull, 32, 63), 0xA5A5A5A5ull);
 	}
 
-	void test_ceil_log2()
-	{
-		EQUALS(ceil_log2(3u), 2u);
-		EQUALS(ceil_log2(0xffffffffu), 32u);
-		EQUALS(ceil_log2(1u), 0u);
-		EQUALS(ceil_log2(256u), 8u);
-		EQUALS(ceil_log2(0x80000000u), 31u);
-	}
-
-	void test_floor_log2()
-	{
-		EQUALS(floor_log2(1.f), 0);
-		EQUALS(floor_log2(3.f), 1);
-		EQUALS(floor_log2(256.f), 8);
-	}
-
 	void test_round_up()
 	{
 		EQUALS(round_up( 0u, 16u), 0u);

source/lib/tex/tex.cpp

@@ -777,8 +777,9 @@ void Tex::UpdateMIPLevels()
 
 	if (m_Flags & TEX_MIPMAPS)
 	{
-		// We add one because we need to account the smallest 1x1 level.
-		m_MIPLevels.reserve(ceil_log2(std::max(m_Width, m_Height)) + 1);
+		// We need to account the smallest 1x1 level.
+		const size_t maxSide{std::max(m_Width, m_Height)};
+		m_MIPLevels.reserve(std::bit_width(maxSide) + !std::has_single_bit(maxSide));
 	}
 
 	u8* levelData = m_Data.get();

source/lib/tex/tex_dds.cpp

@@ -43,6 +43,7 @@
 #include "lib/types.h"
 
 #include <algorithm>
+#include <bit>
 #include <cstdlib>
 #include <memory>
 
@@ -570,8 +571,9 @@ static Status decode_sd(const DDS_HEADER* sd, size_t& w, size_t& h, size_t& bpp,
 		if(mipmap_count)
 		{
 			// mipmap chain is incomplete
-			// note: DDS includes the base level in its count, hence +1.
-			if(mipmap_count != ceil_log2(std::max(w,h))+1)
+			// note: we need to account the DDS base level (1x1).
+			const size_t maxSide{std::max(w, h)};
+			if(mipmap_count != static_cast<size_t>(std::bit_width(maxSide) + !std::has_single_bit(maxSide)))
 				return ERR::TEX_FMT_INVALID;
 			flags |= TEX_MIPMAPS;
 		}

source/simulation2/helpers/LongPathfinder.cpp

@@ -20,7 +20,6 @@
 #include "LongPathfinder.h"
 
 #include "graphics/SColor.h"
-#include "lib/bits.h"
 #include "maths/Fixed.h"
 #include "maths/FixedVector2D.h"
 #include "ps/CLogger.h"
@@ -30,6 +29,7 @@
 #include "simulation2/helpers/Pathfinding.h"
 
 #include <algorithm>
+#include <bit>
 #include <cmath>
 #include <cstddef>
 #include <mutex>
@@ -249,7 +249,7 @@ class JumpPointCache
 
 			if (!data.empty())
 			{
-				size_t depth = ceil_log2(data.size() + 1);
+				size_t depth = std::bit_width(data.size());
 				tree.resize((1 << depth) - 1);
 				ConstructTree(tree, 0, data.size() / 2, data.size(), 0);
 			}