//===-- Value.cpp - Implement the Value 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 Value, ValueHandle, and User classes.
//
//===----------------------------------------------------------------------===//
#include "LLVMContextImpl.h"
#include "llvm/Constant.h"
#include "llvm/Constants.h"
#include "llvm/DerivedTypes.h"
#include "llvm/InstrTypes.h"
#include "llvm/Instructions.h"
#include "llvm/Operator.h"
#include "llvm/Module.h"
#include "llvm/ValueSymbolTable.h"
#include "llvm/ADT/SmallString.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/GetElementPtrTypeIterator.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/LeakDetector.h"
#include "llvm/Support/ManagedStatic.h"
#include "llvm/Support/ValueHandle.h"
#include "llvm/ADT/DenseMap.h"
#include <algorithm>
using namespace llvm;
//===----------------------------------------------------------------------===//
// Value Class
//===----------------------------------------------------------------------===//
static inline Type *checkType(Type *Ty) {
assert(Ty && "Value defined with a null type: Error!");
return const_cast<Type*>(Ty);
}
Value::Value(Type *ty, unsigned scid)
: SubclassID(scid), HasValueHandle(0),
SubclassOptionalData(0), SubclassData(0), VTy((Type*)checkType(ty)),
UseList(0), Name(0) {
// FIXME: Why isn't this in the subclass gunk??
if (isa<CallInst>(this) || isa<InvokeInst>(this))
assert((VTy->isFirstClassType() || VTy->isVoidTy() || VTy->isStructTy()) &&
"invalid CallInst type!");
else if (!isa<Constant>(this) && !isa<BasicBlock>(this))
assert((VTy->isFirstClassType() || VTy->isVoidTy()) &&
"Cannot create non-first-class values except for constants!");
}
Value::~Value() {
// Notify all ValueHandles (if present) that this value is going away.
if (HasValueHandle)
ValueHandleBase::ValueIsDeleted(this);
#ifndef NDEBUG // Only in -g mode...
// Check to make sure that there are no uses of this value that are still
// around when the value is destroyed. If there are, then we have a dangling
// reference and something is wrong. This code is here to print out what is
// still being referenced. The value in question should be printed as
// a <badref>
//
if (!use_empty()) {
dbgs() << "While deleting: " << *VTy << " %" << getName() << "\n";
for (use_iterator I = use_begin(), E = use_end(); I != E; ++I)
dbgs() << "Use still stuck around after Def is destroyed:"
<< **I << "\n";
}
#endif
assert(use_empty() && "Uses remain when a value is destroyed!");
// If this value is named, destroy the name. This should not be in a symtab
// at this point.
if (Name && SubclassID != MDStringVal)
Name->Destroy();
// There should be no uses of this object anymore, remove it.
LeakDetector::removeGarbageObject(this);
}
/// hasNUses - Return true if this Value has exactly N users.
///
bool Value::hasNUses(unsigned N) const {
const_use_iterator UI = use_begin(), E = use_end();
for (; N; --N, ++UI)
if (UI == E) return false; // Too few.
return UI == E;
}
/// hasNUsesOrMore - Return true if this value has N users or more. This is
/// logically equivalent to getNumUses() >= N.
///
bool Value::hasNUsesOrMore(unsigned N) const {
const_use_iterator UI = use_begin(), E = use_end();
for (; N; --N, ++UI)
if (UI == E) return false; // Too few.
return true;
}
/// isUsedInBasicBlock - Return true if this value is used in the specified
/// basic block.
bool Value::isUsedInBasicBlock(const BasicBlock *BB) const {
// Start by scanning over the instructions looking for a use before we start
// the expensive use iteration.
unsigned MaxBlockSize = 3;
for (BasicBlock::const_iterator I = BB->begin(), E = BB->end(); I != E; ++I) {
if (std::find(I->op_begin(), I->op_end(), this) != I->op_end())
return true;
if (MaxBlockSize-- == 0) // If the block is larger fall back to use_iterator
break;
}
if (MaxBlockSize != 0) // We scanned the entire block and found no use.
return false;
for (const_use_iterator I = use_begin(), E = use_end(); I != E; ++I) {
const Instruction *User = dyn_cast<Instruction>(*I);
if (User && User->getParent() == BB)
return true;
}
return false;
}
/// getNumUses - This method computes the number of uses of this Value. This
/// is a linear time operation. Use hasOneUse or hasNUses to check for specific
/// values.
unsigned Value::getNumUses() const {
return (unsigned)std::distance(use_begin(), use_end());
}
static bool getSymTab(Value *V, ValueSymbolTable *&ST) {
ST = 0;
if (Instruction *I = dyn_cast<Instruction>(V)) {
if (BasicBlock *P = I->getParent())
if (Function *PP = P->getParent())
ST = &PP->getValueSymbolTable();
} else if (BasicBlock *BB = dyn_cast<BasicBlock>(V)) {
if (Function *P = BB->getParent())
ST = &P->getValueSymbolTable();
} else if (GlobalValue *GV = dyn_cast<GlobalValue>(V)) {
if (Module *P = GV->getParent())
ST = &P->getValueSymbolTable();
} else if (Argument *A = dyn_cast<Argument>(V)) {
if (Function *P = A->getParent())
ST = &P->getValueSymbolTable();
} else if (isa<MDString>(V))
return true;
else {
assert(isa<Constant>(V) && "Unknown value type!");
return true; // no name is setable for this.
}
return false;
}
StringRef Value::getName() const {
// Make sure the empty string is still a C string. For historical reasons,
// some clients want to call .data() on the result and expect it to be null
// terminated.
if (!Name) return StringRef("", 0);
return Name->getKey();
}
void Value::setName(const Twine &NewName) {
assert(SubclassID != MDStringVal &&
"Cannot set the name of MDString with this method!");
// Fast path for common IRBuilder case of setName("") when there is no name.
if (NewName.isTriviallyEmpty() && !hasName())
return;
SmallString<256> NameData;
StringRef NameRef = NewName.toStringRef(NameData);
// Name isn't changing?
if (getName() == NameRef)
return;
assert(!getType()->isVoidTy() && "Cannot assign a name to void values!");
// Get the symbol table to update for this object.
ValueSymbolTable *ST;
if (getSymTab(this, ST))
return; // Cannot set a name on this value (e.g. constant).
if (!ST) { // No symbol table to update? Just do the change.
if (NameRef.empty()) {
// Free the name for this value.
Name->Destroy();
Name = 0;
return;
}
if (Name)
Name->Destroy();
// NOTE: Could optimize for the case the name is shrinking to not deallocate
// then reallocated.
// Create the new name.
Name = ValueName::Create(NameRef.begin(), NameRef.end());
Name->setValue(this);
return;
}
// NOTE: Could optimize for the case the name is shrinking to not deallocate
// then reallocated.
if (hasName()) {
// Remove old name.
ST->removeValueName(Name);
Name->Destroy();
Name = 0;
if (NameRef.empty())
return;
}
// Name is changing to something new.
Name = ST->createValueName(NameRef, this);
}
/// takeName - transfer the name from V to this value, setting V's name to
/// empty. It is an error to call V->takeName(V).
void Value::takeName(Value *V) {
assert(SubclassID != MDStringVal && "Cannot take the name of an MDString!");
ValueSymbolTable *ST = 0;
// If this value has a name, drop it.
if (hasName()) {
// Get the symtab this is in.
if (getSymTab(this, ST)) {
// We can't set a name on this value, but we need to clear V's name if
// it has one.
if (V->hasName()) V->setName("");
return; // Cannot set a name on this value (e.g. constant).
}
// Remove old name.
if (ST)
ST->removeValueName(Name);
Name->Destroy();
Name = 0;
}
// Now we know that this has no name.
// If V has no name either, we're done.
if (!V->hasName()) return;
// Get this's symtab if we didn't before.
if (!ST) {
if (getSymTab(this, ST)) {
// Clear V's name.
V->setName("");
return; // Cannot set a name on this value (e.g. constant).
}
}
// Get V's ST, this should always succed, because V has a name.
ValueSymbolTable *VST;
bool Failure = getSymTab(V, VST);
assert(!Failure && "V has a name, so it should have a ST!"); (void)Failure;
// If these values are both in the same symtab, we can do this very fast.
// This works even if both values have no symtab yet.
if (ST == VST) {
// Take the name!
Name = V->Name;
V->Name = 0;
Name->setValue(this);
return;
}
// Otherwise, things are slightly more complex. Remove V's name from VST and
// then reinsert it into ST.
if (VST)
VST->removeValueName(V->Name);
Name = V->Name;
V->Name = 0;
Name->setValue(this);
if (ST)
ST->reinsertValue(this);
}
void Value::replaceAllUsesWith(Value *New) {
assert(New && "Value::replaceAllUsesWith(<null>) is invalid!");
assert(New != this && "this->replaceAllUsesWith(this) is NOT valid!");
assert(New->getType() == getType() &&
"replaceAllUses of value with new value of different type!");
// Notify all ValueHandles (if present) that this value is going away.
if (HasValueHandle)
ValueHandleBase::ValueIsRAUWd(this, New);
while (!use_empty()) {
Use &U = *UseList;
// Must handle Constants specially, we cannot call replaceUsesOfWith on a
// constant because they are uniqued.
if (Constant *C = dyn_cast<Constant>(U.getUser())) {
if (!isa<GlobalValue>(C)) {
C->replaceUsesOfWithOnConstant(this, New, &U);
continue;
}
}
U.set(New);
}
if (BasicBlock *BB = dyn_cast<BasicBlock>(this))
BB->replaceSuccessorsPhiUsesWith(cast<BasicBlock>(New));
}
namespace {
// Various metrics for how much to strip off of pointers.
enum PointerStripKind {
PSK_ZeroIndices,
PSK_InBoundsConstantIndices,
PSK_InBounds
};
template <PointerStripKind StripKind>
static Value *stripPointerCastsAndOffsets(Value *V) {
if (!V->getType()->isPointerTy())
return V;
// Even though we don't look through PHI nodes, we could be called on an
// instruction in an unreachable block, which may be on a cycle.
SmallPtrSet<Value *, 4> Visited;
Visited.insert(V);
do {
if (GEPOperator *GEP = dyn_cast<GEPOperator>(V)) {
switch (StripKind) {
case PSK_ZeroIndices:
if (!GEP->hasAllZeroIndices())
return V;
break;
case PSK_InBoundsConstantIndices:
if (!GEP->hasAllConstantIndices())
return V;
// fallthrough
case PSK_InBounds:
if (!GEP->isInBounds())
return V;
break;
}
V = GEP->getPointerOperand();
} else if (Operator::getOpcode(V) == Instruction::BitCast) {
V = cast<Operator>(V)->getOperand(0);
} else if (GlobalAlias *GA = dyn_cast<GlobalAlias>(V)) {
if (GA->mayBeOverridden())
return V;
V = GA->getAliasee();
} else {
return V;
}
assert(V->getType()->isPointerTy() && "Unexpected operand type!");
} while (Visited.insert(V));
return V;
}
} // namespace
Value *Value::stripPointerCasts() {
return stripPointerCastsAndOffsets<PSK_ZeroIndices>(this);
}
Value *Value::stripInBoundsConstantOffsets() {
return stripPointerCastsAndOffsets<PSK_InBoundsConstantIndices>(this);
}
Value *Value::stripInBoundsOffsets() {
return stripPointerCastsAndOffsets<PSK_InBounds>(this);
}
/// isDereferenceablePointer - Test if this value is always a pointer to
/// allocated and suitably aligned memory for a simple load or store.
static bool isDereferenceablePointer(const Value *V,
SmallPtrSet<const Value *, 32> &Visited) {
// Note that it is not safe to speculate into a malloc'd region because
// malloc may return null.
// It's also not always safe to follow a bitcast, for example:
// bitcast i8* (alloca i8) to i32*
// would result in a 4-byte load from a 1-byte alloca. Some cases could
// be handled using TargetData to check sizes and alignments though.
// These are obviously ok.
if (isa<AllocaInst>(V)) return true;
// Global variables which can't collapse to null are ok.
if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(V))
return !GV->hasExternalWeakLinkage();
// byval arguments are ok.
if (const Argument *A = dyn_cast<Argument>(V))
return A->hasByValAttr();
// For GEPs, determine if the indexing lands within the allocated object.
if (const GEPOperator *GEP = dyn_cast<GEPOperator>(V)) {
// Conservatively require that the base pointer be fully dereferenceable.
if (!Visited.insert(GEP->getOperand(0)))
return false;
if (!isDereferenceablePointer(GEP->getOperand(0), Visited))
return false;
// Check the indices.
gep_type_iterator GTI = gep_type_begin(GEP);
for (User::const_op_iterator I = GEP->op_begin()+1,
E = GEP->op_end(); I != E; ++I) {
Value *Index = *I;
Type *Ty = *GTI++;
// Struct indices can't be out of bounds.
if (isa<StructType>(Ty))
continue;
ConstantInt *CI = dyn_cast<ConstantInt>(Index);
if (!CI)
return false;
// Zero is always ok.
if (CI->isZero())
continue;
// Check to see that it's within the bounds of an array.
ArrayType *ATy = dyn_cast<ArrayType>(Ty);
if (!ATy)
return false;
if (CI->getValue().getActiveBits() > 64)
return false;
if (CI->getZExtValue() >= ATy->getNumElements())
return false;
}
// Indices check out; this is dereferenceable.
return true;
}
// If we don't know, assume the worst.
return false;
}
/// isDereferenceablePointer - Test if this value is always a pointer to
/// allocated and suitably aligned memory for a simple load or store.
bool Value::isDereferenceablePointer() const {
SmallPtrSet<const Value *, 32> Visited;
return ::isDereferenceablePointer(this, Visited);
}
/// DoPHITranslation - If this value is a PHI node with CurBB as its parent,
/// return the value in the PHI node corresponding to PredBB. If not, return
/// ourself. This is useful if you want to know the value something has in a
/// predecessor block.
Value *Value::DoPHITranslation(const BasicBlock *CurBB,
const BasicBlock *PredBB) {
PHINode *PN = dyn_cast<PHINode>(this);
if (PN && PN->getParent() == CurBB)
return PN->getIncomingValueForBlock(PredBB);
return this;
}
LLVMContext &Value::getContext() const { return VTy->getContext(); }
//===----------------------------------------------------------------------===//
// ValueHandleBase Class
//===----------------------------------------------------------------------===//
/// AddToExistingUseList - Add this ValueHandle to the use list for VP, where
/// List is known to point into the existing use list.
void ValueHandleBase::AddToExistingUseList(ValueHandleBase **List) {
assert(List && "Handle list is null?");
// Splice ourselves into the list.
Next = *List;
*List = this;
setPrevPtr(List);
if (Next) {
Next->setPrevPtr(&Next);
assert(VP.getPointer() == Next->VP.getPointer() && "Added to wrong list?");
}
}
void ValueHandleBase::AddToExistingUseListAfter(ValueHandleBase *List) {
assert(List && "Must insert after existing node");
Next = List->Next;
setPrevPtr(&List->Next);
List->Next = this;
if (Next)
Next->setPrevPtr(&Next);
}
/// AddToUseList - Add this ValueHandle to the use list for VP.
void ValueHandleBase::AddToUseList() {
assert(VP.getPointer() && "Null pointer doesn't have a use list!");
LLVMContextImpl *pImpl = VP.getPointer()->getContext().pImpl;
if (VP.getPointer()->HasValueHandle) {
// If this value already has a ValueHandle, then it must be in the
// ValueHandles map already.
ValueHandleBase *&Entry = pImpl->ValueHandles[VP.getPointer()];
assert(Entry != 0 && "Value doesn't have any handles?");
AddToExistingUseList(&Entry);
return;
}
// Ok, it doesn't have any handles yet, so we must insert it into the
// DenseMap. However, doing this insertion could cause the DenseMap to
// reallocate itself, which would invalidate all of the PrevP pointers that
// point into the old table. Handle this by checking for reallocation and
// updating the stale pointers only if needed.
DenseMap<Value*, ValueHandleBase*> &Handles = pImpl->ValueHandles;
const void *OldBucketPtr = Handles.getPointerIntoBucketsArray();
ValueHandleBase *&Entry = Handles[VP.getPointer()];
assert(Entry == 0 && "Value really did already have handles?");
AddToExistingUseList(&Entry);
VP.getPointer()->HasValueHandle = true;
// If reallocation didn't happen or if this was the first insertion, don't
// walk the table.
if (Handles.isPointerIntoBucketsArray(OldBucketPtr) ||
Handles.size() == 1) {
return;
}
// Okay, reallocation did happen. Fix the Prev Pointers.
for (DenseMap<Value*, ValueHandleBase*>::iterator I = Handles.begin(),
E = Handles.end(); I != E; ++I) {
assert(I->second && I->first == I->second->VP.getPointer() &&
"List invariant broken!");
I->second->setPrevPtr(&I->second);
}
}
/// RemoveFromUseList - Remove this ValueHandle from its current use list.
void ValueHandleBase::RemoveFromUseList() {
assert(VP.getPointer() && VP.getPointer()->HasValueHandle &&
"Pointer doesn't have a use list!");
// Unlink this from its use list.
ValueHandleBase **PrevPtr = getPrevPtr();
assert(*PrevPtr == this && "List invariant broken");
*PrevPtr = Next;
if (Next) {
assert(Next->getPrevPtr() == &Next && "List invariant broken");
Next->setPrevPtr(PrevPtr);
return;
}
// If the Next pointer was null, then it is possible that this was the last
// ValueHandle watching VP. If so, delete its entry from the ValueHandles
// map.
LLVMContextImpl *pImpl = VP.getPointer()->getContext().pImpl;
DenseMap<Value*, ValueHandleBase*> &Handles = pImpl->ValueHandles;
if (Handles.isPointerIntoBucketsArray(PrevPtr)) {
Handles.erase(VP.getPointer());
VP.getPointer()->HasValueHandle = false;
}
}
void ValueHandleBase::ValueIsDeleted(Value *V) {
assert(V->HasValueHandle && "Should only be called if ValueHandles present");
// Get the linked list base, which is guaranteed to exist since the
// HasValueHandle flag is set.
LLVMContextImpl *pImpl = V->getContext().pImpl;
ValueHandleBase *Entry = pImpl->ValueHandles[V];
assert(Entry && "Value bit set but no entries exist");
// We use a local ValueHandleBase as an iterator so that ValueHandles can add
// and remove themselves from the list without breaking our iteration. This
// is not really an AssertingVH; we just have to give ValueHandleBase a kind.
// Note that we deliberately do not the support the case when dropping a value
// handle results in a new value handle being permanently added to the list
// (as might occur in theory for CallbackVH's): the new value handle will not
// be processed and the checking code will mete out righteous punishment if
// the handle is still present once we have finished processing all the other
// value handles (it is fine to momentarily add then remove a value handle).
for (ValueHandleBase Iterator(Assert, *Entry); Entry; Entry = Iterator.Next) {
Iterator.RemoveFromUseList();
Iterator.AddToExistingUseListAfter(Entry);
assert(Entry->Next == &Iterator && "Loop invariant broken.");
switch (Entry->getKind()) {
case Assert:
break;
case Tracking:
// Mark that this value has been deleted by setting it to an invalid Value
// pointer.
Entry->operator=(DenseMapInfo<Value *>::getTombstoneKey());
break;
case Weak:
// Weak just goes to null, which will unlink it from the list.
Entry->operator=(0);
break;
case Callback:
// Forward to the subclass's implementation.
static_cast<CallbackVH*>(Entry)->deleted();
break;
}
}
// All callbacks, weak references, and assertingVHs should be dropped by now.
if (V->HasValueHandle) {
#ifndef NDEBUG // Only in +Asserts mode...
dbgs() << "While deleting: " << *V->getType() << " %" << V->getName()
<< "\n";
if (pImpl->ValueHandles[V]->getKind() == Assert)
llvm_unreachable("An asserting value handle still pointed to this"
" value!");
#endif
llvm_unreachable("All references to V were not removed?");
}
}
void ValueHandleBase::ValueIsRAUWd(Value *Old, Value *New) {
assert(Old->HasValueHandle &&"Should only be called if ValueHandles present");
assert(Old != New && "Changing value into itself!");
// Get the linked list base, which is guaranteed to exist since the
// HasValueHandle flag is set.
LLVMContextImpl *pImpl = Old->getContext().pImpl;
ValueHandleBase *Entry = pImpl->ValueHandles[Old];
assert(Entry && "Value bit set but no entries exist");
// We use a local ValueHandleBase as an iterator so that
// ValueHandles can add and remove themselves from the list without
// breaking our iteration. This is not really an AssertingVH; we
// just have to give ValueHandleBase some kind.
for (ValueHandleBase Iterator(Assert, *Entry); Entry; Entry = Iterator.Next) {
Iterator.RemoveFromUseList();
Iterator.AddToExistingUseListAfter(Entry);
assert(Entry->Next == &Iterator && "Loop invariant broken.");
switch (Entry->getKind()) {
case Assert:
// Asserting handle does not follow RAUW implicitly.
break;
case Tracking:
// Tracking goes to new value like a WeakVH. Note that this may make it
// something incompatible with its templated type. We don't want to have a
// virtual (or inline) interface to handle this though, so instead we make
// the TrackingVH accessors guarantee that a client never sees this value.
// FALLTHROUGH
case Weak:
// Weak goes to the new value, which will unlink it from Old's list.
Entry->operator=(New);
break;
case Callback:
// Forward to the subclass's implementation.
static_cast<CallbackVH*>(Entry)->allUsesReplacedWith(New);
break;
}
}
#ifndef NDEBUG
// If any new tracking or weak value handles were added while processing the
// list, then complain about it now.
if (Old->HasValueHandle)
for (Entry = pImpl->ValueHandles[Old]; Entry; Entry = Entry->Next)
switch (Entry->getKind()) {
case Tracking:
case Weak:
dbgs() << "After RAUW from " << *Old->getType() << " %"
<< Old->getName() << " to " << *New->getType() << " %"
<< New->getName() << "\n";
llvm_unreachable("A tracking or weak value handle still pointed to the"
" old value!\n");
default:
break;
}
#endif
}
// Default implementation for CallbackVH.
void CallbackVH::allUsesReplacedWith(Value *) {}
void CallbackVH::deleted() {
setValPtr(NULL);
}