// 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_USE_H
#define LLVM_USE_H
#include "llvm/Support/Casting.h"
-#include "llvm/ADT/iterator.h"
+#include "llvm/ADT/PointerIntPair.h"
+#include <iterator>
namespace llvm {
class Value;
class User;
-
-
-//===----------------------------------------------------------------------===//
-// Generic Tagging Functions
-//===----------------------------------------------------------------------===//
+class Use;
/// Tag - generic tag type for (at least 32 bit) pointers
enum Tag { noTag, tagOne, tagTwo, tagThree };
-/// addTag - insert tag bits into an (untagged) pointer
-template <typename T, typename TAG>
-inline T *addTag(const T *P, TAG Tag) {
- return reinterpret_cast<T*>(ptrdiff_t(P) | Tag);
-}
-
-/// stripTag - remove tag bits from a pointer,
-/// making it dereferencable
-template <ptrdiff_t MASK, typename T>
-inline T *stripTag(const T *P) {
- return reinterpret_cast<T*>(ptrdiff_t(P) & ~MASK);
-}
-
-/// extractTag - extract tag bits from a pointer
-template <typename TAG, TAG MASK, typename T>
-inline TAG extractTag(const T *P) {
- return TAG(ptrdiff_t(P) & MASK);
-}
-
-/// transferTag - transfer tag bits from a pointer,
-/// to an untagged pointer
-template <ptrdiff_t MASK, typename T>
-inline T *transferTag(const T *From, const T *To) {
- return reinterpret_cast<T*>((ptrdiff_t(From) & MASK) | ptrdiff_t(To));
-}
-
+// 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.
-//
+/// Use is here to make keeping the "use" list of a Value up-to-date really
+/// easy.
class Use {
- class UseWaymark;
- friend class UseWaymark;
- Value *getValue() const;
- /// nilUse - returns a 'token' that marks the end of the def/use chain
- static Use *nilUse(const Value *V) {
- return addTag((Use*)V, fullStopTagN);
- }
- static bool isNil(Use *U) { return extractTag<NextPtrTag, tagMaskN>(U) == fullStopTagN; }
- void showWaymarks() const;
- static bool isStop(Use *U) {
- return isStopTag(extractTag<NextPtrTag, tagMaskN>(U));
- }
public:
- /// init - specify Value and User
- /// @deprecated in 2.4, will be removed soon
- inline void init(Value *V, User *U);
/// swap - provide a fast substitute to std::swap<Use>
/// that also works with less standard-compliant compilers
void swap(Use &RHS);
/// Destructor - Only for zap()
inline ~Use() {
- if (Val1) removeFromList();
+ if (Val) removeFromList();
}
- /// Default ctor - This leaves the Use completely uninitialized. The only thing
- /// that is valid to do with this use is to call the "init" method.
-
+ /// Default ctor - This leaves the Use completely uninitialized. The only
+ /// thing that is valid to do with this use is to call the "init" method.
inline Use() {}
enum PrevPtrTag { zeroDigitTag = noTag
, oneDigitTag = tagOne
, stopTag = tagTwo
- , fullStopTag = tagThree
- , tagMask = tagThree };
-
- enum NextPtrTag { zeroDigitTagN = tagTwo
- , oneDigitTagN = tagOne
- , stopTagN = noTag
- , fullStopTagN = tagThree
- , tagMaskN = tagThree };
-
- static bool isStopTag(NextPtrTag T) {
- bool P[] = { true, false, false, true };
- return P[T];
- }
+ , fullStopTag = tagThree };
+
public:
- operator Value*() const { return get(); }
- inline Value *get() const;
+ /// 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;
- const Use* getImpliedUser() const;
- static Use *initTags(Use *Start, Use *Stop, ptrdiff_t Done = 0);
- static void zap(Use *Start, const Use *Stop, bool del = false);
inline void set(Value *Val);
return RHS;
}
const Use &operator=(const Use &RHS) {
- set(RHS.Val1);
+ set(RHS.Val);
return *this;
}
- Value *operator->() { return get(); }
- const Value *operator->() const { return get(); }
+ Value *operator->() { return Val; }
+ const Value *operator->() const { return Val; }
+
+ Use *getNext() const { return Next; }
- Use *getNext() const { return extractTag<NextPtrTag, tagMaskN>(Next) == fullStopTagN
- ? 0
- : stripTag<tagMaskN>(Next); }
+
+ /// 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);
+
+ /// getPrefix - Return deletable pointer if appropriate
+ Use *getPrefix();
private:
- Value *Val1;
- Use *Next, **Prev;
+ const Use* getImpliedUser() const;
+ static Use *initTags(Use *Start, Use *Stop, ptrdiff_t Done = 0);
+
+ Value *Val;
+ Use *Next;
+ PointerIntPair<Use**, 2, PrevPtrTag> Prev;
void setPrev(Use **NewPrev) {
- Prev = transferTag<tagMask>(Prev, NewPrev);
+ Prev.setPointer(NewPrev);
}
void addToList(Use **List) {
Next = *List;
- Use *StrippedNext(getNext());
- if (StrippedNext) StrippedNext->setPrev(&Next);
+ if (Next) Next->setPrev(&Next);
setPrev(List);
*List = this;
}
void removeFromList() {
- // __builtin_prefetch(Next);
- Use **StrippedPrev = stripTag<tagMask>(Prev);
- Use *StrippedNext(getNext());
- if (isStop(Next))
- assert((isStop(*StrippedPrev) || (StrippedNext ? isStop(StrippedNext->Next) : true)) && "joining digits?");
+ Use **StrippedPrev = Prev.getPointer();
*StrippedPrev = Next;
- if (StrippedNext) StrippedNext->setPrev(StrippedPrev);
+ if (Next) Next->setPrev(StrippedPrev);
}
friend class Value;
+ friend class User;
};
// simplify_type - Allow clients to treat uses just like values when using
template<typename UserTy> // UserTy == 'User' or 'const User'
-class value_use_iterator : public forward_iterator<UserTy*, ptrdiff_t> {
- typedef forward_iterator<UserTy*, ptrdiff_t> super;
+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(extractTag<Use::NextPtrTag, Use::tagMaskN>(u)
- == Use::fullStopTagN
- ? 0
- : stripTag<Use::tagMaskN>(u)) {}
+ explicit value_use_iterator(Use *u) : U(u) {}
friend class Value;
public:
typedef typename super::reference reference;
}
/// atEnd - return true if this iterator is equal to use_end() on the value.
- bool atEnd() const { return !U; }
+ bool atEnd() const { return U == 0; }
// Iterator traversal: forward iteration only
_Self &operator++() { // Preincrement
- assert(!atEnd() && "Cannot increment end iterator!");
+ assert(U && "Cannot increment end iterator!");
U = U->getNext();
return *this;
}
_Self tmp = *this; ++*this; return tmp;
}
- // Retrieve a reference to the current User
+ // Retrieve a pointer to the current User.
UserTy *operator*() const {
- assert(!atEnd() && "Cannot dereference end iterator!");
+ assert(U && "Cannot dereference end iterator!");
return U->getUser();
}
unsigned getOperandNo() const;
};
-Value *Use::get() const {
- return fullStopTagN == extractTag<NextPtrTag, tagMaskN>(Next)
- ? reinterpret_cast<Value*>(stripTag<tagMaskN>(Next))
- : (Val1 == getValue() ? Val1 : 0); // should crash if not equal!
-}
template<> struct simplify_type<value_use_iterator<User> > {
typedef User* SimpleType;
template<> struct simplify_type<const value_use_iterator<const User> >
: public simplify_type<value_use_iterator<const User> > {};
-
+
} // End llvm namespace
#endif
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