llvm-6502/lib/VMCore/Use.cpp
Gabor Greif 023f84ecaf Introduce a typing refinenement on tagged data
using the 'volatile' qualifier. This should not have any operational consequences
on code, because tags should always be stripped off (giving a non-volatile pointer)
before dereferencing. The new qualification is there to catch some attempts to use
tagged pointers in a context where an untagged pointer is appropriate.

Notably this approach does not catch dereferencing of tagged pointers, but helps
in separating the two concepts a bit.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@57641 91177308-0d34-0410-b5e6-96231b3b80d8
2008-10-16 15:33:02 +00:00

161 lines
4.5 KiB
C++

//===-- 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.
//
//===----------------------------------------------------------------------===//
//
// This file implements the algorithm for finding the User of a Use.
//
//===----------------------------------------------------------------------===//
#include "llvm/User.h"
namespace llvm {
//===----------------------------------------------------------------------===//
// Use swap Implementation
//===----------------------------------------------------------------------===//
void Use::swap(Use &RHS) {
Value *V1(Val);
Value *V2(RHS.Val);
if (V1 != V2) {
if (V1) {
removeFromList();
}
if (V2) {
RHS.removeFromList();
Val = V2;
V2->addUse(*this);
} else {
Val = 0;
}
if (V1) {
RHS.Val = V1;
V1->addUse(RHS);
} else {
RHS.Val = 0;
}
}
}
//===----------------------------------------------------------------------===//
// Use getImpliedUser Implementation
//===----------------------------------------------------------------------===//
const Use *Use::getImpliedUser() const {
const Use *Current = this;
while (true) {
unsigned Tag = extractTag<PrevPtrTag, fullStopTag>((Current++)->Prev);
switch (Tag) {
case zeroDigitTag:
case oneDigitTag:
continue;
case stopTag: {
++Current;
ptrdiff_t Offset = 1;
while (true) {
unsigned Tag = extractTag<PrevPtrTag, fullStopTag>(Current->Prev);
switch (Tag) {
case zeroDigitTag:
case oneDigitTag:
++Current;
Offset = (Offset << 1) + Tag;
continue;
default:
return Current + Offset;
}
}
}
case fullStopTag:
return Current;
}
}
}
//===----------------------------------------------------------------------===//
// Use initTags Implementation
//===----------------------------------------------------------------------===//
Use *Use::initTags(Use * const Start, Use *Stop, ptrdiff_t Done) {
ptrdiff_t Count = Done;
while (Start != Stop) {
--Stop;
Stop->Val = 0;
if (!Count) {
Stop->Prev = reinterpret_cast<Use**>(Done == 0 ? fullStopTag : stopTag);
++Done;
Count = Done;
} else {
Stop->Prev = reinterpret_cast<Use**>(Count & 1);
Count >>= 1;
++Done;
}
}
return Start;
}
//===----------------------------------------------------------------------===//
// Use zap Implementation
//===----------------------------------------------------------------------===//
void Use::zap(Use *Start, const Use *Stop, bool del) {
if (del) {
while (Start != Stop) {
(--Stop)->~Use();
}
::operator delete(Start);
return;
}
while (Start != Stop) {
(Start++)->set(0);
}
}
//===----------------------------------------------------------------------===//
// AugmentedUse layout struct
//===----------------------------------------------------------------------===//
struct AugmentedUse : Use {
volatile User *ref;
AugmentedUse(); // not implemented
};
//===----------------------------------------------------------------------===//
// Use getUser Implementation
//===----------------------------------------------------------------------===//
User *Use::getUser() const {
const Use *End = getImpliedUser();
volatile User *She = static_cast<const AugmentedUse*>(End - 1)->ref;
return extractTag<Tag, tagOne>(She)
? llvm::stripTag<tagOne>(She)
: reinterpret_cast<User*>(const_cast<Use*>(End));
}
//===----------------------------------------------------------------------===//
// User allocHungoffUses Implementation
//===----------------------------------------------------------------------===//
Use *User::allocHungoffUses(unsigned N) const {
Use *Begin = static_cast<Use*>(::operator new(sizeof(Use) * N
+ sizeof(AugmentedUse)
- sizeof(Use)));
Use *End = Begin + N;
static_cast<AugmentedUse&>(End[-1]).ref = addTag(this, tagOne);
return Use::initTags(Begin, End);
}
} // End llvm namespace