1//===- subzero/src/IceUtils.h - Utility functions ---------------*- C++ -*-===// 2// 3// The Subzero Code Generator 4// 5// This file is distributed under the University of Illinois Open Source 6// License. See LICENSE.TXT for details. 7// 8//===----------------------------------------------------------------------===// 9/// 10/// \file 11/// \brief Defines some utility functions. 12/// 13//===----------------------------------------------------------------------===// 14 15#ifndef SUBZERO_SRC_ICEUTILS_H 16#define SUBZERO_SRC_ICEUTILS_H 17 18#include <climits> 19#include <cmath> // std::signbit() 20 21namespace Ice { 22namespace Utils { 23 24/// Allows copying from types of unrelated sizes. This method was introduced to 25/// enable the strict aliasing optimizations of GCC 4.4. Basically, GCC 26/// mindlessly relies on obscure details in the C++ standard that make 27/// reinterpret_cast virtually useless. 28template <typename D, typename S> inline D bitCopy(const S &Source) { 29 static_assert(sizeof(D) <= sizeof(S), 30 "bitCopy between incompatible type widths"); 31 static_assert(!std::is_pointer<S>::value, ""); 32 D Destination; 33 // This use of memcpy is safe: source and destination cannot overlap. 34 memcpy(&Destination, reinterpret_cast<const void *>(&Source), sizeof(D)); 35 return Destination; 36} 37 38/// Check whether an N-bit two's-complement representation can hold value. 39template <typename T> inline bool IsInt(int N, T value) { 40 assert((0 < N) && 41 (static_cast<unsigned int>(N) < (CHAR_BIT * sizeof(value)))); 42 T limit = static_cast<T>(1) << (N - 1); 43 return (-limit <= value) && (value < limit); 44} 45 46template <typename T> inline bool IsUint(int N, T value) { 47 assert((0 < N) && 48 (static_cast<unsigned int>(N) < (CHAR_BIT * sizeof(value)))); 49 T limit = static_cast<T>(1) << N; 50 return (0 <= value) && (value < limit); 51} 52 53/// Check whether the magnitude of value fits in N bits, i.e., whether an 54/// (N+1)-bit sign-magnitude representation can hold value. 55template <typename T> inline bool IsAbsoluteUint(int N, T Value) { 56 assert((0 < N) && 57 (static_cast<unsigned int>(N) < (CHAR_BIT * sizeof(Value)))); 58 if (Value < 0) 59 Value = -Value; 60 return IsUint(N, Value); 61} 62 63/// Return true if the addition X + Y will cause integer overflow for integers 64/// of type T. 65template <typename T> inline bool WouldOverflowAdd(T X, T Y) { 66 return ((X > 0 && Y > 0 && (X > std::numeric_limits<T>::max() - Y)) || 67 (X < 0 && Y < 0 && (X < std::numeric_limits<T>::min() - Y))); 68} 69 70/// Adds x to y and stores the result in sum. Returns true if the addition 71/// overflowed. 72inline bool add_overflow(uint32_t x, uint32_t y, uint32_t *sum) { 73 static_assert(std::is_same<uint32_t, unsigned>::value, "Must match type"); 74#if __has_builtin(__builtin_uadd_overflow) 75 return __builtin_uadd_overflow(x, y, sum); 76#else 77 *sum = x + y; 78 return WouldOverflowAdd(x, y); 79#endif 80} 81 82/// Return true if X is already aligned by N, where N is a power of 2. 83template <typename T> inline bool IsAligned(T X, intptr_t N) { 84 assert(llvm::isPowerOf2_64(N)); 85 return (X & (N - 1)) == 0; 86} 87 88/// Return Value adjusted to the next highest multiple of Alignment. 89inline uint32_t applyAlignment(uint32_t Value, uint32_t Alignment) { 90 assert(llvm::isPowerOf2_32(Alignment)); 91 return (Value + Alignment - 1) & -Alignment; 92} 93 94/// Return amount which must be added to adjust Pos to the next highest 95/// multiple of Align. 96inline uint64_t OffsetToAlignment(uint64_t Pos, uint64_t Align) { 97 assert(llvm::isPowerOf2_64(Align)); 98 uint64_t Mod = Pos & (Align - 1); 99 if (Mod == 0) 100 return 0; 101 return Align - Mod; 102} 103 104/// Rotate the value bit pattern to the left by shift bits. 105/// Precondition: 0 <= shift < 32 106inline uint32_t rotateLeft32(uint32_t value, uint32_t shift) { 107 if (shift == 0) 108 return value; 109 return (value << shift) | (value >> (32 - shift)); 110} 111 112/// Rotate the value bit pattern to the right by shift bits. 113inline uint32_t rotateRight32(uint32_t value, uint32_t shift) { 114 if (shift == 0) 115 return value; 116 return (value >> shift) | (value << (32 - shift)); 117} 118 119/// Returns true if Val is +0.0. It requires T to be a floating point type. 120template <typename T> bool isPositiveZero(T Val) { 121 static_assert(std::is_floating_point<T>::value, 122 "Input type must be floating point"); 123 return Val == 0 && !std::signbit(Val); 124} 125 126/// Resize a vector (or other suitable container) to a particular size, and also 127/// reserve possibly a larger size to avoid repeatedly recopying as the 128/// container grows. It uses a strategy of doubling capacity up to a certain 129/// point, after which it bumps the capacity by a fixed amount. 130template <typename Container> 131inline void reserveAndResize(Container &V, uint32_t Size, 132 uint32_t ChunkSizeBits = 10) { 133#if __has_builtin(__builtin_clz) 134 // Don't call reserve() if Size==0. 135 if (Size > 0) { 136 uint32_t Mask; 137 if (Size <= (1 << ChunkSizeBits)) { 138 // For smaller sizes, reserve the smallest power of 2 greater than or 139 // equal to Size. 140 Mask = 141 ((1 << (CHAR_BIT * sizeof(uint32_t) - __builtin_clz(Size))) - 1) - 1; 142 } else { 143 // For larger sizes, round up to the smallest multiple of 1<<ChunkSizeBits 144 // greater than or equal to Size. 145 Mask = (1 << ChunkSizeBits) - 1; 146 } 147 V.reserve((Size + Mask) & ~Mask); 148 } 149#endif 150 V.resize(Size); 151} 152 153/// An RAII class to ensure that a boolean flag is restored to its previous 154/// value upon function exit. 155/// 156/// Used in places like RandomizationPoolingPause and generating target helper 157/// calls. 158class BoolFlagSaver { 159 BoolFlagSaver() = delete; 160 BoolFlagSaver(const BoolFlagSaver &) = delete; 161 BoolFlagSaver &operator=(const BoolFlagSaver &) = delete; 162 163public: 164 BoolFlagSaver(bool &F, bool NewValue) : OldValue(F), Flag(F) { F = NewValue; } 165 ~BoolFlagSaver() { Flag = OldValue; } 166 167private: 168 const bool OldValue; 169 bool &Flag; 170}; 171 172} // end of namespace Utils 173} // end of namespace Ice 174 175#endif // SUBZERO_SRC_ICEUTILS_H 176