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llvm-6502/include/llvm/IR/Use.h
2013-01-10 00:45:19 +00:00

221 lines
6.1 KiB
C++

//===-- llvm/Use.h - Definition of the Use class ----------------*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This defines the Use class. The Use class represents the operand of an
// instruction or some other User instance which refers to a Value. The Use
// class keeps the "use list" of the referenced value up to date.
//
// Pointer tagging is used to efficiently find the User corresponding
// to a Use without having to store a User pointer in every Use. A
// User is preceded in memory by all the Uses corresponding to its
// operands, and the low bits of one of the fields (Prev) of the Use
// class are used to encode offsets to be able to find that User given
// a pointer to any Use. For details, see:
//
// http://www.llvm.org/docs/ProgrammersManual.html#UserLayout
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_IR_USE_H
#define LLVM_IR_USE_H
#include "llvm/ADT/PointerIntPair.h"
#include "llvm/Support/Compiler.h"
#include <cstddef>
#include <iterator>
namespace llvm {
class Value;
class User;
class Use;
template<typename>
struct simplify_type;
// Use** is only 4-byte aligned.
template<>
class PointerLikeTypeTraits<Use**> {
public:
static inline void *getAsVoidPointer(Use** P) { return P; }
static inline Use **getFromVoidPointer(void *P) {
return static_cast<Use**>(P);
}
enum { NumLowBitsAvailable = 2 };
};
//===----------------------------------------------------------------------===//
// Use Class
//===----------------------------------------------------------------------===//
/// Use is here to make keeping the "use" list of a Value up-to-date really
/// easy.
class Use {
public:
/// swap - provide a fast substitute to std::swap<Use>
/// that also works with less standard-compliant compilers
void swap(Use &RHS);
// A type for the word following an array of hung-off Uses in memory, which is
// a pointer back to their User with the bottom bit set.
typedef PointerIntPair<User*, 1, unsigned> UserRef;
private:
/// Copy ctor - do not implement
Use(const Use &U) LLVM_DELETED_FUNCTION;
/// Destructor - Only for zap()
~Use() {
if (Val) removeFromList();
}
enum PrevPtrTag { zeroDigitTag
, oneDigitTag
, stopTag
, fullStopTag };
/// Constructor
Use(PrevPtrTag tag) : Val(0) {
Prev.setInt(tag);
}
public:
/// Normally Use will just implicitly convert to a Value* that it holds.
operator Value*() const { return Val; }
/// If implicit conversion to Value* doesn't work, the get() method returns
/// the Value*.
Value *get() const { return Val; }
/// getUser - This returns the User that contains this Use. For an
/// instruction operand, for example, this will return the instruction.
User *getUser() const;
inline void set(Value *Val);
Value *operator=(Value *RHS) {
set(RHS);
return RHS;
}
const Use &operator=(const Use &RHS) {
set(RHS.Val);
return *this;
}
Value *operator->() { return Val; }
const Value *operator->() const { return Val; }
Use *getNext() const { return Next; }
/// initTags - initialize the waymarking tags on an array of Uses, so that
/// getUser() can find the User from any of those Uses.
static Use *initTags(Use *Start, Use *Stop);
/// zap - This is used to destroy Use operands when the number of operands of
/// a User changes.
static void zap(Use *Start, const Use *Stop, bool del = false);
private:
const Use* getImpliedUser() const;
Value *Val;
Use *Next;
PointerIntPair<Use**, 2, PrevPtrTag> Prev;
void setPrev(Use **NewPrev) {
Prev.setPointer(NewPrev);
}
void addToList(Use **List) {
Next = *List;
if (Next) Next->setPrev(&Next);
setPrev(List);
*List = this;
}
void removeFromList() {
Use **StrippedPrev = Prev.getPointer();
*StrippedPrev = Next;
if (Next) Next->setPrev(StrippedPrev);
}
friend class Value;
};
// simplify_type - Allow clients to treat uses just like values when using
// casting operators.
template<> struct simplify_type<Use> {
typedef Value* SimpleType;
static SimpleType getSimplifiedValue(const Use &Val) {
return static_cast<SimpleType>(Val.get());
}
};
template<> struct simplify_type<const Use> {
typedef Value* SimpleType;
static SimpleType getSimplifiedValue(const Use &Val) {
return static_cast<SimpleType>(Val.get());
}
};
template<typename UserTy> // UserTy == 'User' or 'const User'
class value_use_iterator : public std::iterator<std::forward_iterator_tag,
UserTy*, ptrdiff_t> {
typedef std::iterator<std::forward_iterator_tag, UserTy*, ptrdiff_t> super;
typedef value_use_iterator<UserTy> _Self;
Use *U;
explicit value_use_iterator(Use *u) : U(u) {}
friend class Value;
public:
typedef typename super::reference reference;
typedef typename super::pointer pointer;
value_use_iterator(const _Self &I) : U(I.U) {}
value_use_iterator() {}
bool operator==(const _Self &x) const {
return U == x.U;
}
bool operator!=(const _Self &x) const {
return !operator==(x);
}
/// atEnd - return true if this iterator is equal to use_end() on the value.
bool atEnd() const { return U == 0; }
// Iterator traversal: forward iteration only
_Self &operator++() { // Preincrement
assert(U && "Cannot increment end iterator!");
U = U->getNext();
return *this;
}
_Self operator++(int) { // Postincrement
_Self tmp = *this; ++*this; return tmp;
}
// Retrieve a pointer to the current User.
UserTy *operator*() const {
assert(U && "Cannot dereference end iterator!");
return U->getUser();
}
UserTy *operator->() const { return operator*(); }
Use &getUse() const { return *U; }
/// getOperandNo - Return the operand # of this use in its User. Defined in
/// User.h
///
unsigned getOperandNo() const;
};
} // End llvm namespace
#endif