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//===-- Use.cpp - Implement the Use class ---------------------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#include "llvm/IR/Use.h"
#include "llvm/IR/User.h"
#include "llvm/IR/Value.h"
#include <new>
namespace llvm {
void Use::swap(Use &RHS) {
if (Val == RHS.Val)
return;
if (Val)
removeFromList();
Value *OldVal = Val;
if (RHS.Val) {
RHS.removeFromList();
Val = RHS.Val;
Val->addUse(*this);
} else {
Val = nullptr;
}
if (OldVal) {
RHS.Val = OldVal;
RHS.Val->addUse(RHS);
} else {
RHS.Val = nullptr;
}
}
User *Use::getUser() const {
const Use *End = getImpliedUser();
const UserRef *ref = reinterpret_cast<const UserRef *>(End);
return ref->getInt() ? ref->getPointer()
: reinterpret_cast<User *>(const_cast<Use *>(End));
}
unsigned Use::getOperandNo() const {
return this - getUser()->op_begin();
}
// Sets up the waymarking algorithm's tags for a series of Uses. See the
// algorithm details here:
//
// http://www.llvm.org/docs/ProgrammersManual.html#the-waymarking-algorithm
//
Use *Use::initTags(Use *const Start, Use *Stop) {
ptrdiff_t Done = 0;
while (Done < 20) {
if (Start == Stop--)
return Start;
static const PrevPtrTag tags[20] = {
fullStopTag, oneDigitTag, stopTag, oneDigitTag, oneDigitTag,
stopTag, zeroDigitTag, oneDigitTag, oneDigitTag, stopTag,
zeroDigitTag, oneDigitTag, zeroDigitTag, oneDigitTag, stopTag,
oneDigitTag, oneDigitTag, oneDigitTag, oneDigitTag, stopTag};
new (Stop) Use(tags[Done++]);
}
ptrdiff_t Count = Done;
while (Start != Stop) {
--Stop;
if (!Count) {
new (Stop) Use(stopTag);
++Done;
Count = Done;
} else {
new (Stop) Use(PrevPtrTag(Count & 1));
Count >>= 1;
++Done;
}
}
return Start;
}
void Use::zap(Use *Start, const Use *Stop, bool del) {
while (Start != Stop)
(--Stop)->~Use();
if (del)
::operator delete(Start);
}
const Use *Use::getImpliedUser() const {
const Use *Current = this;
while (true) {
unsigned Tag = (Current++)->Prev.getInt();
switch (Tag) {
case zeroDigitTag:
case oneDigitTag:
continue;
case stopTag: {
++Current;
ptrdiff_t Offset = 1;
while (true) {
unsigned Tag = Current->Prev.getInt();
switch (Tag) {
case zeroDigitTag:
case oneDigitTag:
++Current;
Offset = (Offset << 1) + Tag;
continue;
default:
return Current + Offset;
}
}
}
case fullStopTag:
return Current;
}
}
}
} // End llvm namespace
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