// 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;
-
+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
/// a User changes.
static void zap(Use *Start, const Use *Stop, bool del = false);
+ /// getPrefix - Return deletable pointer if appropriate
+ Use *getPrefix();
private:
const Use* getImpliedUser() const;
static Use *initTags(Use *Start, Use *Stop, ptrdiff_t Done = 0);
Value *Val;
Use *Next;
- PointerIntPair<Use**, 2, PrevPtrTag> Prev;
+ PointerIntPair<Use**, 2, PrevPtrTag> Prev;
void setPrev(Use **NewPrev) {
Prev.setPointer(NewPrev);
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;
template<> struct simplify_type<const value_use_iterator<const User> >
: public simplify_type<value_use_iterator<const User> > {};
-
+
} // End llvm namespace
#endif