llvm-6502/lib/IR/Value.cpp
Philip Reames 1aa9710c60 Move Value.isDereferenceablePointer to ValueTracking [NFC]
Move isDereferenceablePointer function to Analysis. This function recursively tracks dereferencability over a chain of values like other functions in ValueTracking.

This refactoring is motivated by further changes to support dereferenceable_or_null attribute (http://reviews.llvm.org/D8650). isDereferenceablePointer will be extended to perform context-sensitive analysis and IR is not a good place to have such functionality.

Patch by: Artur Pilipenko <apilipenko@azulsystems.com>
Differential Revision: reviews.llvm.org/D9075




git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@235611 91177308-0d34-0410-b5e6-96231b3b80d8
2015-04-23 17:36:48 +00:00

728 lines
23 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 "llvm/IR/Value.h"
#include "LLVMContextImpl.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/SmallString.h"
#include "llvm/IR/CallSite.h"
#include "llvm/IR/Constant.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/DerivedTypes.h"
#include "llvm/IR/GetElementPtrTypeIterator.h"
#include "llvm/IR/InstrTypes.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/Operator.h"
#include "llvm/IR/Statepoint.h"
#include "llvm/IR/ValueHandle.h"
#include "llvm/IR/ValueSymbolTable.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/ManagedStatic.h"
#include "llvm/Support/raw_ostream.h"
#include <algorithm>
using namespace llvm;
//===----------------------------------------------------------------------===//
// Value Class
//===----------------------------------------------------------------------===//
static inline Type *checkType(Type *Ty) {
assert(Ty && "Value defined with a null type: Error!");
return Ty;
}
Value::Value(Type *ty, unsigned scid)
: VTy(checkType(ty)), UseList(nullptr), SubclassID(scid), HasValueHandle(0),
SubclassOptionalData(0), SubclassData(0), NumOperands(0) {
// FIXME: Why isn't this in the subclass gunk??
// Note, we cannot call isa<CallInst> before the CallInst has been
// constructed.
if (SubclassID == Instruction::Call || SubclassID == Instruction::Invoke)
assert((VTy->isFirstClassType() || VTy->isVoidTy() || VTy->isStructTy()) &&
"invalid CallInst type!");
else if (SubclassID != BasicBlockVal &&
(SubclassID < ConstantFirstVal || SubclassID > ConstantLastVal))
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);
if (isUsedByMetadata())
ValueAsMetadata::handleDeletion(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 where
// the value is still being referenced.
//
if (!use_empty()) {
dbgs() << "While deleting: " << *VTy << " %" << getName() << "\n";
for (auto *U : users())
dbgs() << "Use still stuck around after Def is destroyed:" << *U << "\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.
destroyValueName();
}
void Value::destroyValueName() {
ValueName *Name = getValueName();
if (Name)
Name->Destroy();
setValueName(nullptr);
}
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;
}
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;
}
bool Value::isUsedInBasicBlock(const BasicBlock *BB) const {
// This can be computed either by scanning the instructions in BB, or by
// scanning the use list of this Value. Both lists can be very long, but
// usually one is quite short.
//
// Scan both lists simultaneously until one is exhausted. This limits the
// search to the shorter list.
BasicBlock::const_iterator BI = BB->begin(), BE = BB->end();
const_user_iterator UI = user_begin(), UE = user_end();
for (; BI != BE && UI != UE; ++BI, ++UI) {
// Scan basic block: Check if this Value is used by the instruction at BI.
if (std::find(BI->op_begin(), BI->op_end(), this) != BI->op_end())
return true;
// Scan use list: Check if the use at UI is in BB.
const Instruction *User = dyn_cast<Instruction>(*UI);
if (User && User->getParent() == BB)
return true;
}
return false;
}
unsigned Value::getNumUses() const {
return (unsigned)std::distance(use_begin(), use_end());
}
static bool getSymTab(Value *V, ValueSymbolTable *&ST) {
ST = nullptr;
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 {
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 (!getValueName())
return StringRef("", 0);
return getValueName()->getKey();
}
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);
assert(NameRef.find_first_of(0) == StringRef::npos &&
"Null bytes are not allowed in names");
// 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 (Function *F = dyn_cast<Function>(this))
getContext().pImpl->IntrinsicIDCache.erase(F);
if (!ST) { // No symbol table to update? Just do the change.
if (NameRef.empty()) {
// Free the name for this value.
destroyValueName();
return;
}
// NOTE: Could optimize for the case the name is shrinking to not deallocate
// then reallocated.
destroyValueName();
// Create the new name.
setValueName(ValueName::Create(NameRef));
getValueName()->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(getValueName());
destroyValueName();
if (NameRef.empty())
return;
}
// Name is changing to something new.
setValueName(ST->createValueName(NameRef, this));
}
void Value::takeName(Value *V) {
ValueSymbolTable *ST = nullptr;
// 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(getValueName());
destroyValueName();
}
// 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!
setValueName(V->getValueName());
V->setValueName(nullptr);
getValueName()->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->getValueName());
setValueName(V->getValueName());
V->setValueName(nullptr);
getValueName()->setValue(this);
if (ST)
ST->reinsertValue(this);
}
#ifndef NDEBUG
static bool contains(SmallPtrSetImpl<ConstantExpr *> &Cache, ConstantExpr *Expr,
Constant *C) {
if (!Cache.insert(Expr).second)
return false;
for (auto &O : Expr->operands()) {
if (O == C)
return true;
auto *CE = dyn_cast<ConstantExpr>(O);
if (!CE)
continue;
if (contains(Cache, CE, C))
return true;
}
return false;
}
static bool contains(Value *Expr, Value *V) {
if (Expr == V)
return true;
auto *C = dyn_cast<Constant>(V);
if (!C)
return false;
auto *CE = dyn_cast<ConstantExpr>(Expr);
if (!CE)
return false;
SmallPtrSet<ConstantExpr *, 4> Cache;
return contains(Cache, CE, C);
}
#endif
void Value::replaceAllUsesWith(Value *New) {
assert(New && "Value::replaceAllUsesWith(<null>) is invalid!");
assert(!contains(New, this) &&
"this->replaceAllUsesWith(expr(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);
if (isUsedByMetadata())
ValueAsMetadata::handleRAUW(this, New);
while (!use_empty()) {
Use &U = *UseList;
// Must handle Constants specially, we cannot call replaceUsesOfWith on a
// constant because they are uniqued.
if (auto *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));
}
// Like replaceAllUsesWith except it does not handle constants or basic blocks.
// This routine leaves uses within BB.
void Value::replaceUsesOutsideBlock(Value *New, BasicBlock *BB) {
assert(New && "Value::replaceUsesOutsideBlock(<null>, BB) is invalid!");
assert(!contains(New, this) &&
"this->replaceUsesOutsideBlock(expr(this), BB) is NOT valid!");
assert(New->getType() == getType() &&
"replaceUses of value with new value of different type!");
assert(BB && "Basic block that may contain a use of 'New' must be defined\n");
use_iterator UI = use_begin(), E = use_end();
for (; UI != E;) {
Use &U = *UI;
++UI;
auto *Usr = dyn_cast<Instruction>(U.getUser());
if (Usr && Usr->getParent() == BB)
continue;
U.set(New);
}
return;
}
namespace {
// Various metrics for how much to strip off of pointers.
enum PointerStripKind {
PSK_ZeroIndices,
PSK_ZeroIndicesAndAliases,
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_ZeroIndicesAndAliases:
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 ||
Operator::getOpcode(V) == Instruction::AddrSpaceCast) {
V = cast<Operator>(V)->getOperand(0);
} else if (GlobalAlias *GA = dyn_cast<GlobalAlias>(V)) {
if (StripKind == PSK_ZeroIndices || GA->mayBeOverridden())
return V;
V = GA->getAliasee();
} else {
return V;
}
assert(V->getType()->isPointerTy() && "Unexpected operand type!");
} while (Visited.insert(V).second);
return V;
}
} // namespace
Value *Value::stripPointerCasts() {
return stripPointerCastsAndOffsets<PSK_ZeroIndicesAndAliases>(this);
}
Value *Value::stripPointerCastsNoFollowAliases() {
return stripPointerCastsAndOffsets<PSK_ZeroIndices>(this);
}
Value *Value::stripInBoundsConstantOffsets() {
return stripPointerCastsAndOffsets<PSK_InBoundsConstantIndices>(this);
}
Value *Value::stripAndAccumulateInBoundsConstantOffsets(const DataLayout &DL,
APInt &Offset) {
if (!getType()->isPointerTy())
return this;
assert(Offset.getBitWidth() == DL.getPointerSizeInBits(cast<PointerType>(
getType())->getAddressSpace()) &&
"The offset must have exactly as many bits as our pointer.");
// 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(this);
Value *V = this;
do {
if (GEPOperator *GEP = dyn_cast<GEPOperator>(V)) {
if (!GEP->isInBounds())
return V;
APInt GEPOffset(Offset);
if (!GEP->accumulateConstantOffset(DL, GEPOffset))
return V;
Offset = GEPOffset;
V = GEP->getPointerOperand();
} else if (Operator::getOpcode(V) == Instruction::BitCast ||
Operator::getOpcode(V) == Instruction::AddrSpaceCast) {
V = cast<Operator>(V)->getOperand(0);
} else if (GlobalAlias *GA = dyn_cast<GlobalAlias>(V)) {
V = GA->getAliasee();
} else {
return V;
}
assert(V->getType()->isPointerTy() && "Unexpected operand type!");
} while (Visited.insert(V).second);
return V;
}
Value *Value::stripInBoundsOffsets() {
return stripPointerCastsAndOffsets<PSK_InBounds>(this);
}
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(); }
void Value::reverseUseList() {
if (!UseList || !UseList->Next)
// No need to reverse 0 or 1 uses.
return;
Use *Head = UseList;
Use *Current = UseList->Next;
Head->Next = nullptr;
while (Current) {
Use *Next = Current->Next;
Current->Next = Head;
Head->setPrev(&Current->Next);
Head = Current;
Current = Next;
}
UseList = Head;
Head->setPrev(&UseList);
}
//===----------------------------------------------------------------------===//
// ValueHandleBase Class
//===----------------------------------------------------------------------===//
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(V == Next->V && "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);
}
void ValueHandleBase::AddToUseList() {
assert(V && "Null pointer doesn't have a use list!");
LLVMContextImpl *pImpl = V->getContext().pImpl;
if (V->HasValueHandle) {
// If this value already has a ValueHandle, then it must be in the
// ValueHandles map already.
ValueHandleBase *&Entry = pImpl->ValueHandles[V];
assert(Entry && "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[V];
assert(!Entry && "Value really did already have handles?");
AddToExistingUseList(&Entry);
V->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->V &&
"List invariant broken!");
I->second->setPrevPtr(&I->second);
}
}
void ValueHandleBase::RemoveFromUseList() {
assert(V && V->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 = V->getContext().pImpl;
DenseMap<Value*, ValueHandleBase*> &Handles = pImpl->ValueHandles;
if (Handles.isPointerIntoBucketsArray(PrevPtr)) {
Handles.erase(V);
V->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=(nullptr);
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!");
assert(Old->getType() == New->getType() &&
"replaceAllUses of value with new value of different type!");
// 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
}
// Pin the vtable to this file.
void CallbackVH::anchor() {}