llvm-6502/include/llvm/ADT/PointerIntPair.h
Benjamin Kramer 80d3b1e708 PointerIntPair: Avoid an (academic) case of undefined behavior in the DenseMapInfo specialization.
If we use a pair with an enum type this could create values outside
of the enum range. Avoid it by creating the bit pattern directly.
While there turn a dynamic assert into a static one. No functionality
change.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@204010 91177308-0d34-0410-b5e6-96231b3b80d8
2014-03-15 18:10:49 +00:00

205 lines
7.8 KiB
C++

//===- llvm/ADT/PointerIntPair.h - Pair for pointer and int -----*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file defines the PointerIntPair class.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_ADT_POINTERINTPAIR_H
#define LLVM_ADT_POINTERINTPAIR_H
#include "llvm/Support/Compiler.h"
#include "llvm/Support/PointerLikeTypeTraits.h"
#include <cassert>
#include <limits>
namespace llvm {
template<typename T>
struct DenseMapInfo;
/// PointerIntPair - This class implements a pair of a pointer and small
/// integer. It is designed to represent this in the space required by one
/// pointer by bitmangling the integer into the low part of the pointer. This
/// can only be done for small integers: typically up to 3 bits, but it depends
/// on the number of bits available according to PointerLikeTypeTraits for the
/// type.
///
/// Note that PointerIntPair always puts the IntVal part in the highest bits
/// possible. For example, PointerIntPair<void*, 1, bool> will put the bit for
/// the bool into bit #2, not bit #0, which allows the low two bits to be used
/// for something else. For example, this allows:
/// PointerIntPair<PointerIntPair<void*, 1, bool>, 1, bool>
/// ... and the two bools will land in different bits.
///
template <typename PointerTy, unsigned IntBits, typename IntType=unsigned,
typename PtrTraits = PointerLikeTypeTraits<PointerTy> >
class PointerIntPair {
intptr_t Value;
static_assert(PtrTraits::NumLowBitsAvailable <
std::numeric_limits<uintptr_t>::digits,
"cannot use a pointer type that has all bits free");
static_assert(IntBits <= PtrTraits::NumLowBitsAvailable,
"PointerIntPair with integer size too large for pointer");
enum : uintptr_t {
/// PointerBitMask - The bits that come from the pointer.
PointerBitMask =
~(uintptr_t)(((intptr_t)1 << PtrTraits::NumLowBitsAvailable)-1),
/// IntShift - The number of low bits that we reserve for other uses, and
/// keep zero.
IntShift = (uintptr_t)PtrTraits::NumLowBitsAvailable-IntBits,
/// IntMask - This is the unshifted mask for valid bits of the int type.
IntMask = (uintptr_t)(((intptr_t)1 << IntBits)-1),
// ShiftedIntMask - This is the bits for the integer shifted in place.
ShiftedIntMask = (uintptr_t)(IntMask << IntShift)
};
public:
PointerIntPair() : Value(0) {}
PointerIntPair(PointerTy PtrVal, IntType IntVal) {
setPointerAndInt(PtrVal, IntVal);
}
explicit PointerIntPair(PointerTy PtrVal) {
initWithPointer(PtrVal);
}
PointerTy getPointer() const {
return PtrTraits::getFromVoidPointer(
reinterpret_cast<void*>(Value & PointerBitMask));
}
IntType getInt() const {
return (IntType)((Value >> IntShift) & IntMask);
}
void setPointer(PointerTy PtrVal) {
intptr_t PtrWord
= reinterpret_cast<intptr_t>(PtrTraits::getAsVoidPointer(PtrVal));
assert((PtrWord & ~PointerBitMask) == 0 &&
"Pointer is not sufficiently aligned");
// Preserve all low bits, just update the pointer.
Value = PtrWord | (Value & ~PointerBitMask);
}
void setInt(IntType IntVal) {
intptr_t IntWord = static_cast<intptr_t>(IntVal);
assert((IntWord & ~IntMask) == 0 && "Integer too large for field");
// Preserve all bits other than the ones we are updating.
Value &= ~ShiftedIntMask; // Remove integer field.
Value |= IntWord << IntShift; // Set new integer.
}
void initWithPointer(PointerTy PtrVal) {
intptr_t PtrWord
= reinterpret_cast<intptr_t>(PtrTraits::getAsVoidPointer(PtrVal));
assert((PtrWord & ~PointerBitMask) == 0 &&
"Pointer is not sufficiently aligned");
Value = PtrWord;
}
void setPointerAndInt(PointerTy PtrVal, IntType IntVal) {
intptr_t PtrWord
= reinterpret_cast<intptr_t>(PtrTraits::getAsVoidPointer(PtrVal));
assert((PtrWord & ~PointerBitMask) == 0 &&
"Pointer is not sufficiently aligned");
intptr_t IntWord = static_cast<intptr_t>(IntVal);
assert((IntWord & ~IntMask) == 0 && "Integer too large for field");
Value = PtrWord | (IntWord << IntShift);
}
PointerTy const *getAddrOfPointer() const {
return const_cast<PointerIntPair *>(this)->getAddrOfPointer();
}
PointerTy *getAddrOfPointer() {
assert(Value == reinterpret_cast<intptr_t>(getPointer()) &&
"Can only return the address if IntBits is cleared and "
"PtrTraits doesn't change the pointer");
return reinterpret_cast<PointerTy *>(&Value);
}
void *getOpaqueValue() const { return reinterpret_cast<void*>(Value); }
void setFromOpaqueValue(void *Val) { Value = reinterpret_cast<intptr_t>(Val);}
static PointerIntPair getFromOpaqueValue(void *V) {
PointerIntPair P; P.setFromOpaqueValue(V); return P;
}
// Allow PointerIntPairs to be created from const void * if and only if the
// pointer type could be created from a const void *.
static PointerIntPair getFromOpaqueValue(const void *V) {
(void)PtrTraits::getFromVoidPointer(V);
return getFromOpaqueValue(const_cast<void *>(V));
}
bool operator==(const PointerIntPair &RHS) const {return Value == RHS.Value;}
bool operator!=(const PointerIntPair &RHS) const {return Value != RHS.Value;}
bool operator<(const PointerIntPair &RHS) const {return Value < RHS.Value;}
bool operator>(const PointerIntPair &RHS) const {return Value > RHS.Value;}
bool operator<=(const PointerIntPair &RHS) const {return Value <= RHS.Value;}
bool operator>=(const PointerIntPair &RHS) const {return Value >= RHS.Value;}
};
template <typename T> struct isPodLike;
template<typename PointerTy, unsigned IntBits, typename IntType>
struct isPodLike<PointerIntPair<PointerTy, IntBits, IntType> > {
static const bool value = true;
};
// Provide specialization of DenseMapInfo for PointerIntPair.
template<typename PointerTy, unsigned IntBits, typename IntType>
struct DenseMapInfo<PointerIntPair<PointerTy, IntBits, IntType> > {
typedef PointerIntPair<PointerTy, IntBits, IntType> Ty;
static Ty getEmptyKey() {
uintptr_t Val = static_cast<uintptr_t>(-1);
Val <<= PointerLikeTypeTraits<Ty>::NumLowBitsAvailable;
return Ty::getFromOpaqueValue(reinterpret_cast<void *>(Val));
}
static Ty getTombstoneKey() {
uintptr_t Val = static_cast<uintptr_t>(-2);
Val <<= PointerLikeTypeTraits<PointerTy>::NumLowBitsAvailable;
return Ty::getFromOpaqueValue(reinterpret_cast<void *>(Val));
}
static unsigned getHashValue(Ty V) {
uintptr_t IV = reinterpret_cast<uintptr_t>(V.getOpaqueValue());
return unsigned(IV) ^ unsigned(IV >> 9);
}
static bool isEqual(const Ty &LHS, const Ty &RHS) { return LHS == RHS; }
};
// Teach SmallPtrSet that PointerIntPair is "basically a pointer".
template<typename PointerTy, unsigned IntBits, typename IntType,
typename PtrTraits>
class PointerLikeTypeTraits<PointerIntPair<PointerTy, IntBits, IntType,
PtrTraits> > {
public:
static inline void *
getAsVoidPointer(const PointerIntPair<PointerTy, IntBits, IntType> &P) {
return P.getOpaqueValue();
}
static inline PointerIntPair<PointerTy, IntBits, IntType>
getFromVoidPointer(void *P) {
return PointerIntPair<PointerTy, IntBits, IntType>::getFromOpaqueValue(P);
}
static inline PointerIntPair<PointerTy, IntBits, IntType>
getFromVoidPointer(const void *P) {
return PointerIntPair<PointerTy, IntBits, IntType>::getFromOpaqueValue(P);
}
enum {
NumLowBitsAvailable = PtrTraits::NumLowBitsAvailable - IntBits
};
};
} // end namespace llvm
#endif