llvm/lib/VMCore/Value.cpp
Bob Wilson 032742972f Change Value::getUnderlyingObject to have the MaxLookup value specified as a
parameter with a default value, instead of just hardcoding it in the
implementation.  The limit of MaxLookup = 6 was introduced in r69151 to fix
a performance problem with O(n^2) behavior in instcombine, but the scalarrepl
pass is relying on getUnderlyingObject to go all the way back to an AllocaInst.
Making the limit part of the method signature makes it clear that by default
the result is limited and should help avoid similar problems in the future.
This fixes pr6126.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@94433 91177308-0d34-0410-b5e6-96231b3b80d8
2010-01-25 18:26:54 +00:00

599 lines
20 KiB
C++

//===-- 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/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 const Type *checkType(const Type *Ty) {
assert(Ty && "Value defined with a null type: Error!");
return Ty;
}
Value::Value(const Type *ty, unsigned scid)
: SubclassID(scid), HasValueHandle(0),
SubclassOptionalData(0), SubclassData(0), VTy(checkType(ty)),
UseList(0), Name(0) {
if (isa<CallInst>(this) || isa<InvokeInst>(this))
assert((VTy->isFirstClassType() || VTy->isVoidTy() ||
isa<OpaqueType>(ty) || VTy->getTypeID() == Type::StructTyID) &&
"invalid CallInst type!");
else if (!isa<Constant>(this) && !isa<BasicBlock>(this))
assert((VTy->isFirstClassType() || VTy->isVoidTy() ||
isa<OpaqueType>(ty)) &&
"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 << " %" << getNameStr() << "\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)
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 {
use_const_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 {
use_const_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 {
for (use_const_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 (NamedMDNode *N = dyn_cast<NamedMDNode>(V)) {
if (Module *P = N->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();
}
std::string Value::getNameStr() const {
return getName().str();
}
void Value::setName(const Twine &NewName) {
// 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) {
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!"); Failure=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);
}
// uncheckedReplaceAllUsesWith - This is exactly the same as replaceAllUsesWith,
// except that it doesn't have all of the asserts. The asserts fail because we
// are half-way done resolving types, which causes some types to exist as two
// different Type*'s at the same time. This is a sledgehammer to work around
// this problem.
//
void Value::uncheckedReplaceAllUsesWith(Value *New) {
// 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);
}
}
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!");
uncheckedReplaceAllUsesWith(New);
}
Value *Value::stripPointerCasts() {
if (!isa<PointerType>(getType()))
return this;
Value *V = this;
do {
if (GEPOperator *GEP = dyn_cast<GEPOperator>(V)) {
if (!GEP->hasAllZeroIndices())
return V;
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(isa<PointerType>(V->getType()) && "Unexpected operand type!");
} while (1);
}
Value *Value::getUnderlyingObject(unsigned MaxLookup) {
if (!isa<PointerType>(getType()))
return this;
Value *V = this;
for (unsigned Count = 0; MaxLookup == 0 || Count < MaxLookup; ++Count) {
if (GEPOperator *GEP = dyn_cast<GEPOperator>(V)) {
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(isa<PointerType>(V->getType()) && "Unexpected operand type!");
}
return V;
}
/// 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 == Next->VP && "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 && "Null pointer doesn't have a use list!");
LLVMContextImpl *pImpl = VP->getContext().pImpl;
if (VP->HasValueHandle) {
// If this value already has a ValueHandle, then it must be in the
// ValueHandles map already.
ValueHandleBase *&Entry = pImpl->ValueHandles[VP];
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];
assert(Entry == 0 && "Value really did already have handles?");
AddToExistingUseList(&Entry);
VP->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 && "List invariant broken!");
I->second->setPrevPtr(&I->second);
}
}
/// RemoveFromUseList - Remove this ValueHandle from its current use list.
void ValueHandleBase::RemoveFromUseList() {
assert(VP && VP->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->getContext().pImpl;
DenseMap<Value*, ValueHandleBase*> &Handles = pImpl->ValueHandles;
if (Handles.isPointerIntoBucketsArray(PrevPtr)) {
Handles.erase(VP);
VP->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 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:
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->getNameStr()
<< "\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;
}
}
}
/// ~CallbackVH. Empty, but defined here to avoid emitting the vtable
/// more than once.
CallbackVH::~CallbackVH() {}
//===----------------------------------------------------------------------===//
// User Class
//===----------------------------------------------------------------------===//
// replaceUsesOfWith - Replaces all references to the "From" definition with
// references to the "To" definition.
//
void User::replaceUsesOfWith(Value *From, Value *To) {
if (From == To) return; // Duh what?
assert((!isa<Constant>(this) || isa<GlobalValue>(this)) &&
"Cannot call User::replaceUsesOfWith on a constant!");
for (unsigned i = 0, E = getNumOperands(); i != E; ++i)
if (getOperand(i) == From) { // Is This operand is pointing to oldval?
// The side effects of this setOperand call include linking to
// "To", adding "this" to the uses list of To, and
// most importantly, removing "this" from the use list of "From".
setOperand(i, To); // Fix it now...
}
}