1 files changed, 147 insertions, 0 deletions
diff --git a/third_party/jpeg-xl/lib/jxl/base/bits.h b/third_party/jpeg-xl/lib/jxl/base/bits.h
new file mode 100644
index 0000000000..9f86118e72
--- /dev/null
+++ b/third_party/jpeg-xl/lib/jxl/base/bits.h
@@ -0,0 +1,147 @@
+// Copyright (c) the JPEG XL Project Authors. All rights reserved.
+//
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+#ifndef LIB_JXL_BASE_BITS_H_
+#define LIB_JXL_BASE_BITS_H_
+
+// Specialized instructions for processing register-sized bit arrays.
+
+#include "lib/jxl/base/compiler_specific.h"
+#include "lib/jxl/base/status.h"
+
+#if JXL_COMPILER_MSVC
+#include <intrin.h>
+#endif
+
+#include <stddef.h>
+#include <stdint.h>
+
+namespace jxl {
+
+// Empty struct used as a size tag type.
+template <size_t N>
+struct SizeTag {};
+
+template <typename T>
+constexpr bool IsSigned() {
+  return T(0) > T(-1);
+}
+
+// Undefined results for x == 0.
+static JXL_INLINE JXL_MAYBE_UNUSED size_t
+Num0BitsAboveMS1Bit_Nonzero(SizeTag<4> /* tag */, const uint32_t x) {
+  JXL_DASSERT(x != 0);
+#if JXL_COMPILER_MSVC
+  unsigned long index;
+  _BitScanReverse(&index, x);
+  return 31 - index;
+#else
+  return static_cast<size_t>(__builtin_clz(x));
+#endif
+}
+static JXL_INLINE JXL_MAYBE_UNUSED size_t
+Num0BitsAboveMS1Bit_Nonzero(SizeTag<8> /* tag */, const uint64_t x) {
+  JXL_DASSERT(x != 0);
+#if JXL_COMPILER_MSVC
+#if JXL_ARCH_X64
+  unsigned long index;
+  _BitScanReverse64(&index, x);
+  return 63 - index;
+#else   // JXL_ARCH_X64
+  // _BitScanReverse64 not available
+  uint32_t msb = static_cast<uint32_t>(x >> 32u);
+  unsigned long index;
+  if (msb == 0) {
+    uint32_t lsb = static_cast<uint32_t>(x & 0xFFFFFFFF);
+    _BitScanReverse(&index, lsb);
+    return 63 - index;
+  } else {
+    _BitScanReverse(&index, msb);
+    return 31 - index;
+  }
+#endif  // JXL_ARCH_X64
+#else
+  return static_cast<size_t>(__builtin_clzll(x));
+#endif
+}
+template <typename T>
+static JXL_INLINE JXL_MAYBE_UNUSED size_t
+Num0BitsAboveMS1Bit_Nonzero(const T x) {
+  static_assert(!IsSigned<T>(), "Num0BitsAboveMS1Bit_Nonzero: use unsigned");
+  return Num0BitsAboveMS1Bit_Nonzero(SizeTag<sizeof(T)>(), x);
+}
+
+// Undefined results for x == 0.
+static JXL_INLINE JXL_MAYBE_UNUSED size_t
+Num0BitsBelowLS1Bit_Nonzero(SizeTag<4> /* tag */, const uint32_t x) {
+  JXL_DASSERT(x != 0);
+#if JXL_COMPILER_MSVC
+  unsigned long index;
+  _BitScanForward(&index, x);
+  return index;
+#else
+  return static_cast<size_t>(__builtin_ctz(x));
+#endif
+}
+static JXL_INLINE JXL_MAYBE_UNUSED size_t
+Num0BitsBelowLS1Bit_Nonzero(SizeTag<8> /* tag */, const uint64_t x) {
+  JXL_DASSERT(x != 0);
+#if JXL_COMPILER_MSVC
+#if JXL_ARCH_X64
+  unsigned long index;
+  _BitScanForward64(&index, x);
+  return index;
+#else   // JXL_ARCH_64
+  // _BitScanForward64 not available
+  uint32_t lsb = static_cast<uint32_t>(x & 0xFFFFFFFF);
+  unsigned long index;
+  if (lsb == 0) {
+    uint32_t msb = static_cast<uint32_t>(x >> 32u);
+    _BitScanForward(&index, msb);
+    return 32 + index;
+  } else {
+    _BitScanForward(&index, lsb);
+    return index;
+  }
+#endif  // JXL_ARCH_X64
+#else
+  return static_cast<size_t>(__builtin_ctzll(x));
+#endif
+}
+template <typename T>
+static JXL_INLINE JXL_MAYBE_UNUSED size_t Num0BitsBelowLS1Bit_Nonzero(T x) {
+  static_assert(!IsSigned<T>(), "Num0BitsBelowLS1Bit_Nonzero: use unsigned");
+  return Num0BitsBelowLS1Bit_Nonzero(SizeTag<sizeof(T)>(), x);
+}
+
+// Returns bit width for x == 0.
+template <typename T>
+static JXL_INLINE JXL_MAYBE_UNUSED size_t Num0BitsAboveMS1Bit(const T x) {
+  return (x == 0) ? sizeof(T) * 8 : Num0BitsAboveMS1Bit_Nonzero(x);
+}
+
+// Returns bit width for x == 0.
+template <typename T>
+static JXL_INLINE JXL_MAYBE_UNUSED size_t Num0BitsBelowLS1Bit(const T x) {
+  return (x == 0) ? sizeof(T) * 8 : Num0BitsBelowLS1Bit_Nonzero(x);
+}
+
+// Returns base-2 logarithm, rounded down.
+template <typename T>
+static JXL_INLINE JXL_MAYBE_UNUSED size_t FloorLog2Nonzero(const T x) {
+  return (sizeof(T) * 8 - 1) ^ Num0BitsAboveMS1Bit_Nonzero(x);
+}
+
+// Returns base-2 logarithm, rounded up.
+template <typename T>
+static JXL_INLINE JXL_MAYBE_UNUSED size_t CeilLog2Nonzero(const T x) {
+  const size_t floor_log2 = FloorLog2Nonzero(x);
+  if ((x & (x - 1)) == 0) return floor_log2;  // power of two
+  return floor_log2 + 1;
+}
+
+}  // namespace jxl
+
+#endif  // LIB_JXL_BASE_BITS_H_