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//===- subzero/src/IceUtils.h - Utility functions ---------------*- C++ -*-===//
//
// The Subzero Code Generator
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
///
/// \file
/// \brief Defines some utility functions.
///
//===----------------------------------------------------------------------===//
#ifndef SUBZERO_SRC_ICEUTILS_H
#define SUBZERO_SRC_ICEUTILS_H
#include <climits>
#include <cmath> // std::signbit()
namespace Ice {
namespace Utils {
/// Allows copying from types of unrelated sizes. This method was introduced to
/// enable the strict aliasing optimizations of GCC 4.4. Basically, GCC
/// mindlessly relies on obscure details in the C++ standard that make
/// reinterpret_cast virtually useless.
template <typename D, typename S> inline D bitCopy(const S &Source) {
static_assert(sizeof(D) <= sizeof(S),
"bitCopy between incompatible type widths");
static_assert(!std::is_pointer<S>::value, "");
D Destination;
// This use of memcpy is safe: source and destination cannot overlap.
memcpy(&Destination, reinterpret_cast<const void *>(&Source), sizeof(D));
return Destination;
}
/// Check whether an N-bit two's-complement representation can hold value.
template <typename T> inline bool IsInt(int N, T value) {
assert((0 < N) &&
(static_cast<unsigned int>(N) < (CHAR_BIT * sizeof(value))));
T limit = static_cast<T>(1) << (N - 1);
return (-limit <= value) && (value < limit);
}
template <typename T> inline bool IsUint(int N, T value) {
assert((0 < N) &&
(static_cast<unsigned int>(N) < (CHAR_BIT * sizeof(value))));
T limit = static_cast<T>(1) << N;
return (0 <= value) && (value < limit);
}
/// Check whether the magnitude of value fits in N bits, i.e., whether an
/// (N+1)-bit sign-magnitude representation can hold value.
template <typename T> inline bool IsAbsoluteUint(int N, T Value) {
assert((0 < N) &&
(static_cast<unsigned int>(N) < (CHAR_BIT * sizeof(Value))));
if (Value < 0)
Value = -Value;
return IsUint(N, Value);
}
/// Return true if the addition X + Y will cause integer overflow for integers
/// of type T.
template <typename T> inline bool WouldOverflowAdd(T X, T Y) {
return ((X > 0 && Y > 0 && (X > std::numeric_limits<T>::max() - Y)) ||
(X < 0 && Y < 0 && (X < std::numeric_limits<T>::min() - Y)));
}
/// Adds x to y and stores the result in sum. Returns true if the addition
/// overflowed.
inline bool add_overflow(uint32_t x, uint32_t y, uint32_t *sum) {
static_assert(std::is_same<uint32_t, unsigned>::value, "Must match type");
#if __has_builtin(__builtin_uadd_overflow)
return __builtin_uadd_overflow(x, y, sum);
#else
*sum = x + y;
return WouldOverflowAdd(x, y);
#endif
}
/// Return true if X is already aligned by N, where N is a power of 2.
template <typename T> inline bool IsAligned(T X, intptr_t N) {
assert(llvm::isPowerOf2_64(N));
return (X & (N - 1)) == 0;
}
/// Return Value adjusted to the next highest multiple of Alignment.
inline uint32_t applyAlignment(uint32_t Value, uint32_t Alignment) {
assert(llvm::isPowerOf2_32(Alignment));
return (Value + Alignment - 1) & -Alignment;
}
/// Return amount which must be added to adjust Pos to the next highest
/// multiple of Align.
inline uint64_t OffsetToAlignment(uint64_t Pos, uint64_t Align) {
assert(llvm::isPowerOf2_64(Align));
uint64_t Mod = Pos & (Align - 1);
if (Mod == 0)
return 0;
return Align - Mod;
}
/// Rotate the value bit pattern to the left by shift bits.
/// Precondition: 0 <= shift < 32
inline uint32_t rotateLeft32(uint32_t value, uint32_t shift) {
if (shift == 0)
return value;
return (value << shift) | (value >> (32 - shift));
}
/// Rotate the value bit pattern to the right by shift bits.
inline uint32_t rotateRight32(uint32_t value, uint32_t shift) {
if (shift == 0)
return value;
return (value >> shift) | (value << (32 - shift));
}
/// Returns true if Val is +0.0. It requires T to be a floating point type.
template <typename T> bool isPositiveZero(T Val) {
static_assert(std::is_floating_point<T>::value,
"Input type must be floating point");
return Val == 0 && !std::signbit(Val);
}
/// Resize a vector (or other suitable container) to a particular size, and also
/// reserve possibly a larger size to avoid repeatedly recopying as the
/// container grows. It uses a strategy of doubling capacity up to a certain
/// point, after which it bumps the capacity by a fixed amount.
template <typename Container>
inline void reserveAndResize(Container &V, uint32_t Size,
uint32_t ChunkSizeBits = 10) {
#if __has_builtin(__builtin_clz)
// Don't call reserve() if Size==0.
if (Size > 0) {
uint32_t Mask;
if (Size <= (1u << ChunkSizeBits)) {
// For smaller sizes, reserve the smallest power of 2 greater than or
// equal to Size.
Mask =
((1 << (CHAR_BIT * sizeof(uint32_t) - __builtin_clz(Size))) - 1) - 1;
} else {
// For larger sizes, round up to the smallest multiple of 1<<ChunkSizeBits
// greater than or equal to Size.
Mask = (1 << ChunkSizeBits) - 1;
}
V.reserve((Size + Mask) & ~Mask);
}
#endif
V.resize(Size);
}
/// An RAII class to ensure that a boolean flag is restored to its previous
/// value upon function exit.
///
/// Used in places like RandomizationPoolingPause and generating target helper
/// calls.
class BoolFlagSaver {
BoolFlagSaver() = delete;
BoolFlagSaver(const BoolFlagSaver &) = delete;
BoolFlagSaver &operator=(const BoolFlagSaver &) = delete;
public:
BoolFlagSaver(bool &F, bool NewValue) : OldValue(F), Flag(F) { F = NewValue; }
~BoolFlagSaver() { Flag = OldValue; }
private:
const bool OldValue;
bool &Flag;
};
} // end of namespace Utils
} // end of namespace Ice
#endif // SUBZERO_SRC_ICEUTILS_H