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/*
* Copyright (C) 2013-2018 Apple Inc. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
* OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#pragma once
#if ENABLE(DFG_JIT)
#include "DFGGraph.h"
namespace JSC { namespace DFG {
// This phase is used to determine if a node can safely run at a new location.
// It is important to note that returning false does not mean it's definitely
// wrong to run the node at the new location. In other words, returning false
// does not imply moving the node would be invalid only that this phase could
// not prove it is valid. Thus, it is always ok to return false.
template<typename AbstractStateType>
class SafeToExecuteEdge {
public:
SafeToExecuteEdge(AbstractStateType& state)
: m_state(state)
{
}
void operator()(Node*, Edge edge)
{
m_maySeeEmptyChild |= !!(m_state.forNode(edge).m_type & SpecEmpty);
switch (edge.useKind()) {
case UntypedUse:
case Int32Use:
case DoubleRepUse:
case DoubleRepRealUse:
case Int52RepUse:
case NumberUse:
case RealNumberUse:
case BooleanUse:
case CellUse:
case CellOrOtherUse:
case ObjectUse:
case ArrayUse:
case FunctionUse:
case FinalObjectUse:
case RegExpObjectUse:
case PromiseObjectUse:
case ProxyObjectUse:
case DerivedArrayUse:
case DateObjectUse:
case MapObjectUse:
case SetObjectUse:
case WeakMapObjectUse:
case WeakSetObjectUse:
case DataViewObjectUse:
case ObjectOrOtherUse:
case StringIdentUse:
case StringUse:
case StringOrOtherUse:
case SymbolUse:
case BigIntUse:
case StringObjectUse:
case StringOrStringObjectUse:
case NotStringVarUse:
case NotSymbolUse:
case NotCellUse:
case OtherUse:
case MiscUse:
case AnyIntUse:
case DoubleRepAnyIntUse:
return;
case KnownInt32Use:
if (m_state.forNode(edge).m_type & ~SpecInt32Only)
m_result = false;
return;
case KnownBooleanUse:
if (m_state.forNode(edge).m_type & ~SpecBoolean)
m_result = false;
return;
case KnownCellUse:
if (m_state.forNode(edge).m_type & ~SpecCell)
m_result = false;
return;
case KnownStringUse:
if (m_state.forNode(edge).m_type & ~SpecString)
m_result = false;
return;
case KnownPrimitiveUse:
if (m_state.forNode(edge).m_type & ~(SpecHeapTop & ~SpecObject))
m_result = false;
return;
case KnownOtherUse:
if (m_state.forNode(edge).m_type & ~SpecOther)
m_result = false;
return;
case LastUseKind:
RELEASE_ASSERT_NOT_REACHED();
break;
}
RELEASE_ASSERT_NOT_REACHED();
}
bool result() const { return m_result; }
bool maySeeEmptyChild() const { return m_maySeeEmptyChild; }
private:
AbstractStateType& m_state;
bool m_result { true };
bool m_maySeeEmptyChild { false };
};
// Determines if it's safe to execute a node within the given abstract state. This may
// return false conservatively. If it returns true, then you can hoist the given node
// up to the given point and expect that it will not crash. It also guarantees that the
// node will not produce a malformed JSValue or object pointer when executed in the
// given state. But this doesn't guarantee that the node will produce the result you
// wanted. For example, you may have a GetByOffset from a prototype that only makes
// semantic sense if you've also checked that some nearer prototype doesn't also have
// a property of the same name. This could still return true even if that check hadn't
// been performed in the given abstract state. That's fine though: the load can still
// safely execute before that check, so long as that check continues to guard any
// user-observable things done to the loaded value.
template<typename AbstractStateType>
bool safeToExecute(AbstractStateType& state, Graph& graph, Node* node, bool ignoreEmptyChildren = false)
{
SafeToExecuteEdge<AbstractStateType> safeToExecuteEdge(state);
DFG_NODE_DO_TO_CHILDREN(graph, node, safeToExecuteEdge);
if (!safeToExecuteEdge.result())
return false;
if (!ignoreEmptyChildren && safeToExecuteEdge.maySeeEmptyChild()) {
// We conservatively assume if the empty value flows into a node,
// it might not be able to handle it (e.g, crash). In general, the bytecode generator
// emits code in such a way that most node types don't need to worry about the empty value
// because they will never see it. However, code motion has to consider the empty
// value so it does not insert/move nodes to a place where they will crash. E.g, the
// type check hoisting phase needs to insert CheckStructureOrEmpty instead of CheckStructure
// for hoisted structure checks because it can not guarantee that a particular local is not
// the empty value.
switch (node->op()) {
case CheckNotEmpty:
case CheckStructureOrEmpty:
case CheckArrayOrEmpty:
break;
default:
return false;
}
}
// NOTE: This can lie when it comes to effectful nodes, because it knows that they aren't going to
// get hoisted anyway. Sometimes this is convenient so we can avoid branching on some internal
// state of the node (like what some child's UseKind might be). However, nodes that are obviously
// always effectful, we return false for, to make auditing the "return true" cases easier.
switch (node->op()) {
// FIXME: Audit these:
// https://bugs.webkit.org/show_bug.cgi?id=207075
case JSConstant:
case DoubleConstant:
case Int52Constant:
case LazyJSConstant:
case Identity:
case IdentityWithProfile:
case GetCallee:
case GetArgumentCountIncludingThis:
case GetRestLength:
case GetLocal:
case GetStack:
case ExitOK:
case Phantom:
case ArithBitNot:
case ArithBitAnd:
case ArithBitOr:
case ArithBitXor:
case ArithBitLShift:
case ArithBitRShift:
case BitURShift:
case ValueToInt32:
case UInt32ToNumber:
case DoubleAsInt32:
case ArithAdd:
case ArithClz32:
case ArithSub:
case ArithNegate:
case ArithMul:
case ArithIMul:
case ArithDiv:
case ArithMod:
case ArithAbs:
case ArithMin:
case ArithMax:
case ArithPow:
case ArithRandom:
case ArithSqrt:
case ArithFRound:
case ArithRound:
case ArithFloor:
case ArithCeil:
case ArithTrunc:
case ArithUnary:
case TryGetById: // FIXME: Audit this: https://bugs.webkit.org/show_bug.cgi?id=163834
case CheckStructure:
case CheckStructureOrEmpty:
case GetExecutable:
case CallDOMGetter:
case CallDOM:
case CheckSubClass:
case CheckArray:
case CheckArrayOrEmpty:
case GetScope:
case SkipScope:
case GetGlobalObject:
case GetGlobalThis:
case GetClosureVar:
case GetGlobalVar:
case GetGlobalLexicalVariable:
case CheckCell:
case CheckNotEmpty:
case AssertNotEmpty:
case CheckIdent:
case CompareLess:
case CompareLessEq:
case CompareGreater:
case CompareGreaterEq:
case CompareBelow:
case CompareBelowEq:
case CompareEq:
case CompareStrictEq:
case CompareEqPtr:
case SameValue:
case CheckTypeInfoFlags:
case ParseInt:
case OverridesHasInstance:
case IsEmpty:
case IsUndefined:
case IsUndefinedOrNull:
case IsBoolean:
case IsNumber:
case NumberIsInteger:
case IsObject:
case IsObjectOrNull:
case IsFunction:
case IsCellWithType:
case IsTypedArrayView:
case TypeOf:
case LogicalNot:
case ToString:
case NumberToStringWithValidRadixConstant:
case StrCat:
case CallStringConstructor:
case MakeRope:
case GetFromArguments:
case GetArgument:
case StringFromCharCode:
case ExtractOSREntryLocal:
case ExtractCatchLocal:
case CheckInBounds:
case ConstantStoragePointer:
case Check:
case CheckVarargs:
case ValueRep:
case DoubleRep:
case Int52Rep:
case BooleanToNumber:
case FiatInt52:
case HasIndexedProperty:
case GetEnumeratorStructurePname:
case GetEnumeratorGenericPname:
case ToIndexString:
case CheckStructureImmediate:
case GetMyArgumentByVal:
case GetMyArgumentByValOutOfBounds:
case GetPrototypeOf:
case StringReplace:
case StringReplaceRegExp:
case GetRegExpObjectLastIndex:
case MapHash:
case NormalizeMapKey:
case StringSlice:
case ToLowerCase:
case GetMapBucket:
case GetMapBucketHead:
case GetMapBucketNext:
case LoadKeyFromMapBucket:
case LoadValueFromMapBucket:
case ExtractValueFromWeakMapGet:
case WeakMapGet:
case AtomicsIsLockFree:
case MatchStructure:
case DateGetInt32OrNaN:
case DateGetTime:
case DataViewGetInt:
case DataViewGetFloat:
return true;
case GetButterfly:
return state.forNode(node->child1()).isType(SpecObject);
case ArraySlice:
case ArrayIndexOf: {
// You could plausibly move this code around as long as you proved the
// incoming array base structure is an original array at the hoisted location.
// Instead of doing that extra work, we just conservatively return false.
return false;
}
case GetGetter:
case GetSetter: {
if (!state.forNode(node->child1()).isType(SpecCell))
return false;
StructureAbstractValue& value = state.forNode(node->child1()).m_structure;
if (value.isInfinite() || value.size() != 1)
return false;
return value[0].get() == graph.m_vm.getterSetterStructure;
}
case BottomValue:
// If in doubt, assume that this isn't safe to execute, just because we have no way of
// compiling this node.
return false;
case StoreBarrier:
case FencedStoreBarrier:
case PutStructure:
case NukeStructureAndSetButterfly:
// We conservatively assume that these cannot be put anywhere, which forces the compiler to
// keep them exactly where they were. This is sort of overkill since the clobberize effects
// already force these things to be ordered precisely. I'm just not confident enough in my
// effect based memory model to rely solely on that right now.
return false;
case FilterCallLinkStatus:
case FilterGetByStatus:
case FilterPutByIdStatus:
case FilterInByIdStatus:
// We don't want these to be moved anywhere other than where we put them, since we want them
// to capture "profiling" at the point in control flow here the user put them.
return false;
case GetByVal:
case GetIndexedPropertyStorage:
case GetArrayLength:
case GetVectorLength:
case ArrayPop:
case StringCharAt:
case StringCharCodeAt:
case StringCodePointAt:
return node->arrayMode().alreadyChecked(graph, node, state.forNode(graph.child(node, 0)));
case ArrayPush:
return node->arrayMode().alreadyChecked(graph, node, state.forNode(graph.varArgChild(node, 1)));
case CheckNeutered:
case GetTypedArrayByteOffset:
return !(state.forNode(node->child1()).m_type & ~(SpecTypedArrayView));
case PutByValDirect:
case PutByVal:
case PutByValAlias:
return node->arrayMode().modeForPut().alreadyChecked(
graph, node, state.forNode(graph.varArgChild(node, 0)));
case AllocatePropertyStorage:
case ReallocatePropertyStorage:
return state.forNode(node->child1()).m_structure.isSubsetOf(
RegisteredStructureSet(node->transition()->previous));
case GetGetterSetterByOffset: {
// If it's an inline property, we need to make sure it's a cell before trusting what the structure set tells us.
if (node->child1().node() == node->child2().node() && !state.forNode(node->child2()).isType(SpecCell))
return false;
StorageAccessData& data = node->storageAccessData();
auto* uid = graph.identifiers()[data.identifierNumber];
PropertyOffset desiredOffset = data.offset;
StructureAbstractValue& value = state.forNode(node->child2()).m_structure;
if (value.isInfinite())
return false;
for (unsigned i = value.size(); i--;) {
Structure* thisStructure = value[i].get();
if (thisStructure->isUncacheableDictionary())
return false;
unsigned attributes = 0;
PropertyOffset checkOffset = thisStructure->getConcurrently(uid, attributes);
if (checkOffset != desiredOffset || !(attributes & PropertyAttribute::Accessor))
return false;
}
return true;
}
case GetByOffset:
case PutByOffset: {
// If it's an inline property, we need to make sure it's a cell before trusting what the structure set tells us.
if (node->child1().node() == node->child2().node() && !state.forNode(node->child2()).isType(SpecCell))
return false;
StorageAccessData& data = node->storageAccessData();
PropertyOffset offset = data.offset;
// Graph::isSafeToLoad() is all about proofs derived from PropertyConditions. Those don't
// know anything about inferred types. But if we have a proof derived from watching a
// structure that has a type proof, then the next case below will deal with it.
if (state.structureClobberState() == StructuresAreWatched) {
if (JSObject* knownBase = node->child2()->dynamicCastConstant<JSObject*>(graph.m_vm)) {
if (graph.isSafeToLoad(knownBase, offset))
return true;
}
}
StructureAbstractValue& value = state.forNode(node->child2()).m_structure;
if (value.isInfinite())
return false;
for (unsigned i = value.size(); i--;) {
Structure* thisStructure = value[i].get();
if (thisStructure->isUncacheableDictionary())
return false;
if (!thisStructure->isValidOffset(offset))
return false;
}
return true;
}
case MultiGetByOffset: {
// We can't always guarantee that the MultiGetByOffset is safe to execute if it
// contains loads from prototypes. If the load requires a check in IR, which is rare, then
// we currently claim that we don't know if it's safe to execute because finding that
// check in the abstract state would be hard. If the load requires watchpoints, we just
// check if we're not in a clobbered state (i.e. in between a side effect and an
// invalidation point).
for (const MultiGetByOffsetCase& getCase : node->multiGetByOffsetData().cases) {
GetByOffsetMethod method = getCase.method();
switch (method.kind()) {
case GetByOffsetMethod::Invalid:
RELEASE_ASSERT_NOT_REACHED();
break;
case GetByOffsetMethod::Constant: // OK because constants are always safe to execute.
case GetByOffsetMethod::Load: // OK because the MultiGetByOffset has its own checks for loading from self.
break;
case GetByOffsetMethod::LoadFromPrototype:
// Only OK if the state isn't clobbered. That's almost always the case.
if (state.structureClobberState() != StructuresAreWatched)
return false;
if (!graph.isSafeToLoad(method.prototype()->cast<JSObject*>(), method.offset()))
return false;
break;
}
}
return true;
}
case ToThis:
case CreateThis:
case CreatePromise:
case CreateGenerator:
case CreateAsyncGenerator:
case ObjectCreate:
case ObjectKeys:
case SetLocal:
case SetCallee:
case PutStack:
case KillStack:
case MovHint:
case ZombieHint:
case Upsilon:
case Phi:
case Flush:
case SetArgumentDefinitely:
case SetArgumentMaybe:
case SetArgumentCountIncludingThis:
case PhantomLocal:
case DeleteById:
case DeleteByVal:
case GetById:
case GetByIdWithThis:
case GetByValWithThis:
case GetByIdFlush:
case GetByIdDirect:
case GetByIdDirectFlush:
case PutById:
case PutByIdFlush:
case PutByIdWithThis:
case PutByValWithThis:
case PutByIdDirect:
case PutGetterById:
case PutSetterById:
case PutGetterSetterById:
case PutGetterByVal:
case PutSetterByVal:
case DefineDataProperty:
case DefineAccessorProperty:
case Arrayify:
case ArrayifyToStructure:
case PutClosureVar:
case PutGlobalVariable:
case CheckBadCell:
case RegExpExec:
case RegExpExecNonGlobalOrSticky:
case RegExpTest:
case RegExpMatchFast:
case RegExpMatchFastGlobal:
case Call:
case DirectCall:
case TailCallInlinedCaller:
case DirectTailCallInlinedCaller:
case Construct:
case DirectConstruct:
case CallVarargs:
case CallEval:
case TailCallVarargsInlinedCaller:
case TailCallForwardVarargsInlinedCaller:
case ConstructVarargs:
case VarargsLength:
case LoadVarargs:
case CallForwardVarargs:
case ConstructForwardVarargs:
case NewObject:
case NewPromise:
case NewGenerator:
case NewAsyncGenerator:
case NewArray:
case NewArrayWithSize:
case NewArrayBuffer:
case NewArrayWithSpread:
case NewArrayIterator:
case Spread:
case NewRegexp:
case NewSymbol:
case ProfileType:
case ProfileControlFlow:
case InstanceOf:
case InstanceOfCustom:
case CallObjectConstructor:
case ToPrimitive:
case ToPropertyKey:
case ToNumber:
case ToNumeric:
case ToObject:
case NumberToStringWithRadix:
case SetFunctionName:
case NewStringObject:
case InByVal:
case InById:
case HasOwnProperty:
case PushWithScope:
case CreateActivation:
case CreateDirectArguments:
case CreateScopedArguments:
case CreateClonedArguments:
case CreateArgumentsButterfly:
case PutToArguments:
case NewFunction:
case NewGeneratorFunction:
case NewAsyncGeneratorFunction:
case NewAsyncFunction:
case Jump:
case Branch:
case Switch:
case EntrySwitch:
case Return:
case TailCall:
case DirectTailCall:
case TailCallVarargs:
case TailCallForwardVarargs:
case Throw:
case ThrowStaticError:
case CountExecution:
case SuperSamplerBegin:
case SuperSamplerEnd:
case ForceOSRExit:
case CPUIntrinsic:
case CheckTraps:
case LogShadowChickenPrologue:
case LogShadowChickenTail:
case NewTypedArray:
case Unreachable:
case ClearCatchLocals:
case CheckTierUpInLoop:
case CheckTierUpAtReturn:
case CheckTierUpAndOSREnter:
case LoopHint:
case InvalidationPoint:
case NotifyWrite:
case MultiPutByOffset:
case GetEnumerableLength:
case HasGenericProperty:
case HasStructureProperty:
case GetDirectPname:
case GetPropertyEnumerator:
case PhantomNewObject:
case PhantomNewFunction:
case PhantomNewGeneratorFunction:
case PhantomNewAsyncGeneratorFunction:
case PhantomNewAsyncFunction:
case PhantomNewArrayIterator:
case PhantomCreateActivation:
case PhantomNewRegexp:
case PutHint:
case MaterializeNewObject:
case MaterializeCreateActivation:
case MaterializeNewInternalFieldObject:
case PhantomDirectArguments:
case PhantomCreateRest:
case PhantomSpread:
case PhantomNewArrayWithSpread:
case PhantomNewArrayBuffer:
case PhantomClonedArguments:
case ForwardVarargs:
case CreateRest:
case SetRegExpObjectLastIndex:
case RecordRegExpCachedResult:
case GetDynamicVar:
case PutDynamicVar:
case ResolveScopeForHoistingFuncDeclInEval:
case ResolveScope:
case StringValueOf:
case WeakSetAdd:
case WeakMapSet:
case AtomicsAdd:
case AtomicsAnd:
case AtomicsCompareExchange:
case AtomicsExchange:
case AtomicsLoad:
case AtomicsOr:
case AtomicsStore:
case AtomicsSub:
case AtomicsXor:
case InitializeEntrypointArguments:
case ValueNegate:
case GetInternalField:
case PutInternalField:
case DataViewSet:
case SetAdd:
case MapSet:
return false;
case Inc:
case Dec:
return node->child1().useKind() != UntypedUse;
case ValueBitAnd:
case ValueBitXor:
case ValueBitOr:
case ValueBitLShift:
case ValueBitRShift:
case ValueAdd:
case ValueSub:
case ValueMul:
case ValueDiv:
case ValueMod:
case ValuePow:
return node->isBinaryUseKind(BigIntUse);
case ValueBitNot:
return node->child1().useKind() == BigIntUse;
case LastNodeType:
RELEASE_ASSERT_NOT_REACHED();
return false;
}
RELEASE_ASSERT_NOT_REACHED();
return false;
}
} } // namespace JSC::DFG
#endif // ENABLE(DFG_JIT)