MathExtras.h

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//===-- llvm/Support/MathExtras.h - Useful math functions -------*- C++ -*-===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file contains some functions that are useful for math stuff.
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_SUPPORT_MATHEXTRAS_H
#define LLVM_SUPPORT_MATHEXTRAS_H

#include "llvm/Support/DataTypes.h"

namespace llvm {

// NOTE: The following support functions use the _32/_64 extensions instead of  
// type overloading so that signed and unsigned integers can be used without
// ambiguity.

/// Hi_32 - This function returns the high 32 bits of a 64 bit value.
inline uint32_t Hi_32(uint64_t Value) {
  return static_cast<uint32_t>(Value >> 32);
}

/// Lo_32 - This function returns the low 32 bits of a 64 bit value.
inline uint32_t Lo_32(uint64_t Value) {
  return static_cast<uint32_t>(Value);
}

/// is?Type - these functions produce optimal testing for integer data types.
inline bool isInt8  (int64_t Value) { 
  return static_cast<int8_t>(Value) == Value; 
}
inline bool isUInt8 (int64_t Value) { 
  return static_cast<uint8_t>(Value) == Value; 
}
inline bool isInt16 (int64_t Value) { 
  return static_cast<int16_t>(Value) == Value; 
}
inline bool isUInt16(int64_t Value) { 
  return static_cast<uint16_t>(Value) == Value; 
}
inline bool isInt32 (int64_t Value) { 
  return static_cast<int32_t>(Value) == Value; 
}
inline bool isUInt32(int64_t Value) { 
  return static_cast<uint32_t>(Value) == Value; 
}

/// isMask_32 - This function returns true if the argument is a sequence of ones
/// starting at the least significant bit with the remainder zero (32 bit
/// version).   Ex. isMask_32(0x0000FFFFU) == true.
inline bool isMask_32(uint32_t Value) {
  return Value && ((Value + 1) & Value) == 0;
}

/// isMask_64 - This function returns true if the argument is a sequence of ones
/// starting at the least significant bit with the remainder zero (64 bit
/// version).
inline bool isMask_64(uint64_t Value) {
  return Value && ((Value + 1) & Value) == 0;
}

/// isShiftedMask_32 - This function returns true if the argument contains a  
/// sequence of ones with the remainder zero (32 bit version.)
/// Ex. isShiftedMask_32(0x0000FF00U) == true.
inline bool isShiftedMask_32(uint32_t Value) {
  return isMask_32((Value - 1) | Value);
}

/// isShiftedMask_64 - This function returns true if the argument contains a  
/// sequence of ones with the remainder zero (64 bit version.)
inline bool isShiftedMask_64(uint64_t Value) {
  return isMask_64((Value - 1) | Value);
}

/// isPowerOf2_32 - This function returns true if the argument is a power of 
/// two > 0. Ex. isPowerOf2_32(0x00100000U) == true (32 bit edition.)
inline bool isPowerOf2_32(uint32_t Value) {
  return Value && !(Value & (Value - 1));
}

/// isPowerOf2_64 - This function returns true if the argument is a power of two
/// > 0 (64 bit edition.)
inline bool isPowerOf2_64(uint64_t Value) {
  return Value && !(Value & (Value - int64_t(1L)));
}

/// ByteSwap_16 - This function returns a byte-swapped representation of the
/// 16-bit argument, Value.
inline uint16_t ByteSwap_16(uint16_t Value) {
#if defined(_MSC_VER) && !defined(_DEBUG)
  // The DLL version of the runtime lacks these functions (bug!?), but in a
  // release build they're replaced with BSWAP instructions anyway.
  return _byteswap_ushort(Value);
#else
  uint16_t Hi = Value << 8;
  uint16_t Lo = Value >> 8;
  return Hi | Lo;
#endif
}

/// ByteSwap_32 - This function returns a byte-swapped representation of the
/// 32-bit argument, Value.
inline uint32_t ByteSwap_32(uint32_t Value) {
#if __GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 3)
  return __builtin_bswap32(Value);
#elif defined(_MSC_VER) && !defined(_DEBUG)
  return _byteswap_ulong(Value);
#else
  uint32_t Byte0 = Value & 0x000000FF;
  uint32_t Byte1 = Value & 0x0000FF00;
  uint32_t Byte2 = Value & 0x00FF0000;
  uint32_t Byte3 = Value & 0xFF000000;
  return (Byte0 << 24) | (Byte1 << 8) | (Byte2 >> 8) | (Byte3 >> 24);
#endif
}

/// ByteSwap_64 - This function returns a byte-swapped representation of the
/// 64-bit argument, Value.
inline uint64_t ByteSwap_64(uint64_t Value) {
#if __GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 3)
  return __builtin_bswap64(Value);
#elif defined(_MSC_VER) && !defined(_DEBUG)
  return _byteswap_uint64(Value);
#else
  uint64_t Hi = ByteSwap_32(uint32_t(Value));
  uint32_t Lo = ByteSwap_32(uint32_t(Value >> 32));
  return (Hi << 32) | Lo;
#endif
}

/// CountLeadingZeros_32 - this function performs the platform optimal form of
/// counting the number of zeros from the most significant bit to the first one
/// bit.  Ex. CountLeadingZeros_32(0x00F000FF) == 8.
/// Returns 32 if the word is zero.
inline unsigned CountLeadingZeros_32(uint32_t Value) {
  unsigned Count; // result
#if __GNUC__ >= 4
  // PowerPC is defined for __builtin_clz(0)
#if !defined(__ppc__) && !defined(__ppc64__)
  if (!Value) return 32;
#endif
  Count = __builtin_clz(Value);
#else
  if (!Value) return 32;
  Count = 0;
  // bisecton method for count leading zeros
  for (unsigned Shift = 32 >> 1; Shift; Shift >>= 1) {
    uint32_t Tmp = Value >> Shift;
    if (Tmp) {
      Value = Tmp;
    } else {
      Count |= Shift;
    }
  }
#endif
  return Count;
}

/// CountLeadingOnes_32 - this function performs the operation of
/// counting the number of ones from the most significant bit to the first zero
/// bit.  Ex. CountLeadingOnes_32(0xFF0FFF00) == 8.
/// Returns 32 if the word is all ones.
inline unsigned CountLeadingOnes_32(uint32_t Value) {
  return CountLeadingZeros_32(~Value);
}

/// CountLeadingZeros_64 - This function performs the platform optimal form
/// of counting the number of zeros from the most significant bit to the first 
/// one bit (64 bit edition.)
/// Returns 64 if the word is zero.
inline unsigned CountLeadingZeros_64(uint64_t Value) {
  unsigned Count; // result
#if __GNUC__ >= 4
  // PowerPC is defined for __builtin_clzll(0)
#if !defined(__ppc__) && !defined(__ppc64__)
  if (!Value) return 64;
#endif
  Count = __builtin_clzll(Value);
#else
  if (sizeof(long) == sizeof(int64_t)) {
    if (!Value) return 64;
    Count = 0;
    // bisecton method for count leading zeros
    for (unsigned Shift = 64 >> 1; Shift; Shift >>= 1) {
      uint64_t Tmp = Value >> Shift;
      if (Tmp) {
        Value = Tmp;
      } else {
        Count |= Shift;
      }
    }
  } else {
    // get hi portion
    uint32_t Hi = Hi_32(Value);

    // if some bits in hi portion
    if (Hi) {
        // leading zeros in hi portion plus all bits in lo portion
        Count = CountLeadingZeros_32(Hi);
    } else {
        // get lo portion
        uint32_t Lo = Lo_32(Value);
        // same as 32 bit value
        Count = CountLeadingZeros_32(Lo)+32;
    }
  }
#endif
  return Count;
}

/// CountLeadingOnes_64 - This function performs the operation
/// of counting the number of ones from the most significant bit to the first 
/// zero bit (64 bit edition.)
/// Returns 64 if the word is all ones.
inline unsigned CountLeadingOnes_64(uint64_t Value) {
  return CountLeadingZeros_64(~Value);
}

/// CountTrailingZeros_32 - this function performs the platform optimal form of
/// counting the number of zeros from the least significant bit to the first one
/// bit.  Ex. CountTrailingZeros_32(0xFF00FF00) == 8.
/// Returns 32 if the word is zero.
inline unsigned CountTrailingZeros_32(uint32_t Value) {
#if __GNUC__ >= 4
  return Value ? __builtin_ctz(Value) : 32;
#else
  static const unsigned Mod37BitPosition[] = {
    32, 0, 1, 26, 2, 23, 27, 0, 3, 16, 24, 30, 28, 11, 0, 13,
    4, 7, 17, 0, 25, 22, 31, 15, 29, 10, 12, 6, 0, 21, 14, 9,
    5, 20, 8, 19, 18
  };
  return Mod37BitPosition[(-Value & Value) % 37];
#endif
}

/// CountTrailingOnes_32 - this function performs the operation of
/// counting the number of ones from the least significant bit to the first zero
/// bit.  Ex. CountTrailingOnes_32(0x00FF00FF) == 8.
/// Returns 32 if the word is all ones.
inline unsigned CountTrailingOnes_32(uint32_t Value) {
  return CountTrailingZeros_32(~Value);
}

/// CountTrailingZeros_64 - This function performs the platform optimal form
/// of counting the number of zeros from the least significant bit to the first 
/// one bit (64 bit edition.)
/// Returns 64 if the word is zero.
inline unsigned CountTrailingZeros_64(uint64_t Value) {
#if __GNUC__ >= 4
  return Value ? __builtin_ctzll(Value) : 64;
#else
  static const unsigned Mod67Position[] = {
    64, 0, 1, 39, 2, 15, 40, 23, 3, 12, 16, 59, 41, 19, 24, 54,
    4, 64, 13, 10, 17, 62, 60, 28, 42, 30, 20, 51, 25, 44, 55,
    47, 5, 32, 65, 38, 14, 22, 11, 58, 18, 53, 63, 9, 61, 27,
    29, 50, 43, 46, 31, 37, 21, 57, 52, 8, 26, 49, 45, 36, 56,
    7, 48, 35, 6, 34, 33, 0
  };
  return Mod67Position[(-Value & Value) % 67];
#endif
}

/// CountTrailingOnes_64 - This function performs the operation
/// of counting the number of ones from the least significant bit to the first 
/// zero bit (64 bit edition.)
/// Returns 64 if the word is all ones.
inline unsigned CountTrailingOnes_64(uint64_t Value) {
  return CountTrailingZeros_64(~Value);
}

/// CountPopulation_32 - this function counts the number of set bits in a value.
/// Ex. CountPopulation(0xF000F000) = 8
/// Returns 0 if the word is zero.
inline unsigned CountPopulation_32(uint32_t Value) {
#if __GNUC__ >= 4
  return __builtin_popcount(Value);
#else
  uint32_t v = Value - ((Value >> 1) & 0x55555555);
  v = (v & 0x33333333) + ((v >> 2) & 0x33333333);
  return ((v + (v >> 4) & 0xF0F0F0F) * 0x1010101) >> 24;
#endif
}

/// CountPopulation_64 - this function counts the number of set bits in a value,
/// (64 bit edition.)
inline unsigned CountPopulation_64(uint64_t Value) {
#if __GNUC__ >= 4
  return __builtin_popcountll(Value);
#else
  uint64_t v = Value - ((Value >> 1) & 0x5555555555555555ULL);
  v = (v & 0x3333333333333333ULL) + ((v >> 2) & 0x3333333333333333ULL);
  v = (v + (v >> 4)) & 0x0F0F0F0F0F0F0F0FULL;
  return unsigned((uint64_t)(v * 0x0101010101010101ULL) >> 56);
#endif
}

/// Log2_32 - This function returns the floor log base 2 of the specified value, 
/// -1 if the value is zero. (32 bit edition.)
/// Ex. Log2_32(32) == 5, Log2_32(1) == 0, Log2_32(0) == -1, Log2_32(6) == 2
inline unsigned Log2_32(uint32_t Value) {
  return 31 - CountLeadingZeros_32(Value);
}

/// Log2_64 - This function returns the floor log base 2 of the specified value, 
/// -1 if the value is zero. (64 bit edition.)
inline unsigned Log2_64(uint64_t Value) {
  return 63 - CountLeadingZeros_64(Value);
}

/// Log2_32_Ceil - This function returns the ceil log base 2 of the specified
/// value, 32 if the value is zero. (32 bit edition).
/// Ex. Log2_32_Ceil(32) == 5, Log2_32_Ceil(1) == 0, Log2_32_Ceil(6) == 3
inline unsigned Log2_32_Ceil(uint32_t Value) {
  return 32-CountLeadingZeros_32(Value-1);
}

/// Log2_64 - This function returns the ceil log base 2 of the specified value, 
/// 64 if the value is zero. (64 bit edition.)
inline unsigned Log2_64_Ceil(uint64_t Value) {
  return 64-CountLeadingZeros_64(Value-1);
}

/// GreatestCommonDivisor64 - Return the greatest common divisor of the two
/// values using Euclid's algorithm.
inline uint64_t GreatestCommonDivisor64(uint64_t A, uint64_t B) {
  while (B) {
    uint64_t T = B;
    B = A % B;
    A = T;
  }
  return A;
}
  
/// BitsToDouble - This function takes a 64-bit integer and returns the bit
/// equivalent double.
inline double BitsToDouble(uint64_t Bits) {
  union {
    uint64_t L;
    double D;
  } T;
  T.L = Bits;
  return T.D;
}

/// BitsToFloat - This function takes a 32-bit integer and returns the bit
/// equivalent float.
inline float BitsToFloat(uint32_t Bits) {
  union {
    uint32_t I;
    float F;
  } T;
  T.I = Bits;
  return T.F;
}

/// DoubleToBits - This function takes a double and returns the bit
/// equivalent 64-bit integer.  Note that copying doubles around
/// changes the bits of NaNs on some hosts, notably x86, so this
/// routine cannot be used if these bits are needed.
inline uint64_t DoubleToBits(double Double) {
  union {
    uint64_t L;
    double D;
  } T;
  T.D = Double;
  return T.L;
}

/// FloatToBits - This function takes a float and returns the bit
/// equivalent 32-bit integer.  Note that copying floats around
/// changes the bits of NaNs on some hosts, notably x86, so this
/// routine cannot be used if these bits are needed.
inline uint32_t FloatToBits(float Float) {
  union {
    uint32_t I;
    float F;
  } T;
  T.F = Float;
  return T.I;
}

/// Platform-independent wrappers for the C99 isnan() function.
int IsNAN(float f);
int IsNAN(double d);

/// Platform-independent wrappers for the C99 isinf() function.
int IsInf(float f);
int IsInf(double d);

/// MinAlign - A and B are either alignments or offsets.  Return the minimum
/// alignment that may be assumed after adding the two together.
static inline uint64_t MinAlign(uint64_t A, uint64_t B) {
  // The largest power of 2 that divides both A and B.
  return (A | B) & -(A | B);
}

/// NextPowerOf2 - Returns the next power of two (in 64-bits)
/// that is strictly greater than A.  Returns zero on overflow.
static inline uint64_t NextPowerOf2(uint64_t A) {
  A |= (A >> 1);
  A |= (A >> 2);
  A |= (A >> 4);
  A |= (A >> 8);
  A |= (A >> 16);
  A |= (A >> 32);
  return A + 1;
}
  
} // End llvm namespace

#endif