// 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"
+#include "llvm/ADT/PointerIntPair.h"
+#include <cstddef>
+#include <iterator>
namespace llvm {
class Value;
class User;
+class Use;
+/// Tag - generic tag type for (at least 32 bit) pointers
+enum Tag { noTag, tagOne, tagTwo, tagThree };
+
+// 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 {
public:
- 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);
- Use(Value *V, User *U) { init(V, U); }
- Use(const Use &U) { init(U.Val, U.U); }
+private:
+ /// Copy ctor - do not implement
+ Use(const Use &U);
+
+ /// Destructor - Only for zap()
inline ~Use() {
if (Val) removeFromList();
}
- /// Default ctor - This leaves the Use completely unitialized. The only thing
- /// that is valid to do with this use is to call the "init" method.
- inline Use() : Val(0) {}
-
+ /// 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 };
+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; }
- User *getUser() const { return U; }
+
+ /// 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);
const Value *operator->() const { return Val; }
Use *getNext() const { return 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:
- Use *Next, **Prev;
+ const Use* getImpliedUser() const;
+ static Use *initTags(Use *Start, Use *Stop, ptrdiff_t Done = 0);
+
Value *Val;
- User *U;
+ Use *Next;
+ PointerIntPair<Use**, 2, PrevPtrTag> Prev;
+ void setPrev(Use **NewPrev) {
+ Prev.setPointer(NewPrev);
+ }
void addToList(Use **List) {
Next = *List;
- if (Next) Next->Prev = &Next;
- Prev = List;
+ if (Next) Next->setPrev(&Next);
+ setPrev(List);
*List = this;
}
void removeFromList() {
- *Prev = Next;
- if (Next) Next->Prev = Prev;
+ Use **StrippedPrev = Prev.getPointer();
+ *StrippedPrev = Next;
+ 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;
_Self tmp = *this; ++*this; return tmp;
}
- // Retrieve a reference to the current SCC
+ // Retrieve a pointer to the current User.
UserTy *operator*() const {
- assert(U && "Cannot increment end iterator!");
+ assert(U && "Cannot dereference end iterator!");
return U->getUser();
}
unsigned getOperandNo() const;
};
-
-template<> struct simplify_type<value_use_iterator<User> > {
- typedef User* SimpleType;
-
- static SimpleType getSimplifiedValue(const value_use_iterator<User> &Val) {
- return *Val;
- }
-};
-
-template<> struct simplify_type<const value_use_iterator<User> >
- : public simplify_type<value_use_iterator<User> > {};
-
-template<> struct simplify_type<value_use_iterator<const User> > {
- typedef const User* SimpleType;
-
- static SimpleType getSimplifiedValue(const
- value_use_iterator<const User> &Val) {
- return *Val;
- }
-};
-
-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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