1 // Copyright 2014 the V8 project authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
15 // A simple type system for compiler-internal use. It is based entirely on
16 // union types, and all subtyping hence amounts to set inclusion. Besides the
17 // obvious primitive types and some predefined unions, the type language also
18 // can express class types (a.k.a. specific maps) and singleton types (i.e.,
19 // concrete constants).
21 // Types consist of two dimensions: semantic (value range) and representation.
22 // Both are related through subtyping.
26 // The following equations and inequations hold for the semantic axis:
31 // Number = Signed32 \/ Unsigned32 \/ Double
33 // Name = String \/ Symbol
34 // UniqueName = InternalizedString \/ Symbol
35 // InternalizedString < String
37 // Receiver = Object \/ Proxy
41 // Undetectable < Object
42 // Detectable = Receiver \/ Number \/ Name - Undetectable
44 // Class(map) < T iff instance_type(map) < T
45 // Constant(x) < T iff instance_type(map(x)) < T
47 // Function(R, S, T0, T1, ...) < Function
49 // Both structural Array and Function types are invariant in all parameters.
50 // Relaxing this would make Union and Intersect operations more involved.
51 // Note that Constant(x) < Class(map(x)) does _not_ hold, since x's map can
52 // change! (Its instance type cannot, however.)
53 // TODO(rossberg): the latter is not currently true for proxies, because of fix,
54 // but will hold once we implement direct proxies.
55 // However, we also define a 'temporal' variant of the subtyping relation that
56 // considers the _current_ state only, i.e., Constant(x) <_now Class(map(x)).
58 // REPRESENTATIONAL DIMENSION
60 // For the representation axis, the following holds:
65 // UntaggedInt <= UntaggedInt8 \/ UntaggedInt16 \/ UntaggedInt32)
66 // UntaggedFloat <= UntaggedFloat32 \/ UntaggedFloat64
67 // UntaggedNumber <= UntaggedInt \/ UntaggedFloat
68 // Untagged <= UntaggedNumber \/ UntaggedPtr
69 // Tagged <= TaggedInt \/ TaggedPtr
71 // Subtyping relates the two dimensions, for example:
73 // Number <= Tagged \/ UntaggedNumber
74 // Object <= TaggedPtr \/ UntaggedPtr
76 // That holds because the semantic type constructors defined by the API create
77 // types that allow for all possible representations, and dually, the ones for
78 // representation types initially include all semantic ranges. Representations
79 // can then e.g. be narrowed for a given semantic type using intersection:
81 // SignedSmall /\ TaggedInt (a 'smi')
82 // Number /\ TaggedPtr (a heap number)
86 // There are two main functions for testing types:
88 // T1->Is(T2) -- tests whether T1 is included in T2 (i.e., T1 <= T2)
89 // T1->Maybe(T2) -- tests whether T1 and T2 overlap (i.e., T1 /\ T2 =/= 0)
91 // Typically, the former is to be used to select representations (e.g., via
92 // T->Is(SignedSmall())), and the latter to check whether a specific case needs
93 // handling (e.g., via T->Maybe(Number())).
95 // There is no functionality to discover whether a type is a leaf in the
96 // lattice. That is intentional. It should always be possible to refine the
97 // lattice (e.g., splitting up number types further) without invalidating any
98 // existing assumptions or tests.
99 // Consequently, do not normally use Equals for type tests, always use Is!
101 // The NowIs operator implements state-sensitive subtying, as described above.
102 // Any compilation decision based on such temporary properties requires runtime
107 // Various formal properties hold for constructors, operators, and predicates
108 // over types. For example, constructors are injective, subtyping is a complete
109 // partial order, union and intersection satisfy the usual algebraic properties.
111 // See test/cctest/test-types.cc for a comprehensive executable specification,
112 // especially with respect to the properties of the more exotic 'temporal'
113 // constructors and predicates (those prefixed 'Now').
117 // Internally, all 'primitive' types, and their unions, are represented as
118 // bitsets. Class is a heap pointer to the respective map. Only Constant's, or
119 // unions containing Class'es or Constant's, currently require allocation.
120 // Note that the bitset representation is closed under both Union and Intersect.
122 // There are two type representations, using different allocation:
124 // - class Type (zone-allocated, for compiler and concurrent compilation)
125 // - class HeapType (heap-allocated, for persistent types)
127 // Both provide the same API, and the Convert method can be used to interconvert
128 // them. For zone types, no query method touches the heap, only constructors do.
131 #define MASK_BITSET_TYPE_LIST(V) \
132 V(Representation, static_cast<int>(0xff800000)) \
133 V(Semantic, static_cast<int>(0x007fffff))
135 #define REPRESENTATION(k) ((k) & kRepresentation)
136 #define SEMANTIC(k) ((k) & kSemantic)
138 #define REPRESENTATION_BITSET_TYPE_LIST(V) \
140 V(UntaggedInt8, 1 << 23 | kSemantic) \
141 V(UntaggedInt16, 1 << 24 | kSemantic) \
142 V(UntaggedInt32, 1 << 25 | kSemantic) \
143 V(UntaggedFloat32, 1 << 26 | kSemantic) \
144 V(UntaggedFloat64, 1 << 27 | kSemantic) \
145 V(UntaggedPtr, 1 << 28 | kSemantic) \
146 V(TaggedInt, 1 << 29 | kSemantic) \
147 V(TaggedPtr, -1 << 30 | kSemantic) /* MSB has to be sign-extended */ \
149 V(UntaggedInt, kUntaggedInt8 | kUntaggedInt16 | kUntaggedInt32) \
150 V(UntaggedFloat, kUntaggedFloat32 | kUntaggedFloat64) \
151 V(UntaggedNumber, kUntaggedInt | kUntaggedFloat) \
152 V(Untagged, kUntaggedNumber | kUntaggedPtr) \
153 V(Tagged, kTaggedInt | kTaggedPtr)
155 #define SEMANTIC_BITSET_TYPE_LIST(V) \
156 V(Null, 1 << 0 | REPRESENTATION(kTaggedPtr)) \
157 V(Undefined, 1 << 1 | REPRESENTATION(kTaggedPtr)) \
158 V(Boolean, 1 << 2 | REPRESENTATION(kTaggedPtr)) \
159 V(SignedSmall, 1 << 3 | REPRESENTATION(kTagged | kUntaggedNumber)) \
160 V(OtherSigned32, 1 << 4 | REPRESENTATION(kTagged | kUntaggedNumber)) \
161 V(Unsigned32, 1 << 5 | REPRESENTATION(kTagged | kUntaggedNumber)) \
162 V(Float, 1 << 6 | REPRESENTATION(kTagged | kUntaggedNumber)) \
163 V(Float32x4, 1 << 7 | REPRESENTATION(kTaggedPtr)) \
164 V(Float64x2, 1 << 8 | REPRESENTATION(kTaggedPtr)) \
165 V(Int32x4, 1 << 9 | REPRESENTATION(kTaggedPtr)) \
166 V(Symbol, 1 << 10 | REPRESENTATION(kTaggedPtr)) \
167 V(InternalizedString, 1 << 11 | REPRESENTATION(kTaggedPtr)) \
168 V(OtherString, 1 << 12 | REPRESENTATION(kTaggedPtr)) \
169 V(Undetectable, 1 << 13 | REPRESENTATION(kTaggedPtr)) \
170 V(Array, 1 << 14 | REPRESENTATION(kTaggedPtr)) \
171 V(Function, 1 << 15 | REPRESENTATION(kTaggedPtr)) \
172 V(RegExp, 1 << 16 | REPRESENTATION(kTaggedPtr)) \
173 V(OtherObject, 1 << 17 | REPRESENTATION(kTaggedPtr)) \
174 V(Proxy, 1 << 18 | REPRESENTATION(kTaggedPtr)) \
175 V(Internal, 1 << 19 | REPRESENTATION(kTagged | kUntagged)) \
177 V(Signed32, kSignedSmall | kOtherSigned32) \
178 V(Number, kSigned32 | kUnsigned32 | kFloat) \
179 V(String, kInternalizedString | kOtherString) \
180 V(UniqueName, kSymbol | kInternalizedString) \
181 V(Name, kSymbol | kString) \
182 V(NumberOrString, kNumber | kString) \
183 V(DetectableObject, kArray | kFunction | kRegExp | kOtherObject) \
184 V(DetectableReceiver, kDetectableObject | kProxy) \
185 V(Detectable, kDetectableReceiver | kNumber | kName) \
186 V(Object, kDetectableObject | kUndetectable) \
187 V(Receiver, kObject | kProxy) \
188 V(NonNumber, kBoolean | kName | kNull | kReceiver | \
189 kFloat32x4 | kFloat64x2 | kInt32x4 | \
190 kUndefined | kInternal) \
193 #define BITSET_TYPE_LIST(V) \
194 MASK_BITSET_TYPE_LIST(V) \
195 REPRESENTATION_BITSET_TYPE_LIST(V) \
196 SEMANTIC_BITSET_TYPE_LIST(V)
199 // typedef TypeImpl<Config> Type;
203 // template<class> struct Handle { typedef type; } // No template typedefs...
204 // template<class T> static Handle<T>::type handle(T* t); // !is_bitset(t)
205 // template<class T> static Handle<T>::type cast(Handle<Type>::type);
206 // static bool is_bitset(Type*);
207 // static bool is_class(Type*);
208 // static bool is_constant(Type*);
209 // static bool is_struct(Type*, int tag);
210 // static int as_bitset(Type*);
211 // static i::Handle<i::Map> as_class(Type*);
212 // static i::Handle<i::Object> as_constant(Type*);
213 // static Handle<Struct>::type as_struct(Type*);
214 // static Type* from_bitset(int bitset);
215 // static Handle<Type>::type from_bitset(int bitset, Region*);
216 // static Handle<Type>::type from_class(i::Handle<Map>, int lub, Region*);
217 // static Handle<Type>::type from_constant(i::Handle<Object>, int, Region*);
218 // static Handle<Type>::type from_struct(Handle<Struct>::type, int tag);
219 // static Handle<Struct>::type struct_create(int tag, int length, Region*);
220 // static void struct_shrink(Handle<Struct>::type, int length);
221 // static int struct_tag(Handle<Struct>::type);
222 // static int struct_length(Handle<Struct>::type);
223 // static Handle<Type>::type struct_get(Handle<Struct>::type, int);
224 // static void struct_set(Handle<Struct>::type, int, Handle<Type>::type);
225 // static int lub_bitset(Type*);
227 template<class Config>
228 class TypeImpl : public Config::Base {
230 class BitsetType; // Internal
231 class StructuralType; // Internal
232 class UnionType; // Internal
239 typedef typename Config::template Handle<TypeImpl>::type TypeHandle;
240 typedef typename Config::template Handle<ClassType>::type ClassHandle;
241 typedef typename Config::template Handle<ConstantType>::type ConstantHandle;
242 typedef typename Config::template Handle<ArrayType>::type ArrayHandle;
243 typedef typename Config::template Handle<FunctionType>::type FunctionHandle;
244 typedef typename Config::template Handle<UnionType>::type UnionHandle;
245 typedef typename Config::Region Region;
247 #define DEFINE_TYPE_CONSTRUCTOR(type, value) \
248 static TypeImpl* type() { return BitsetType::New(BitsetType::k##type); } \
249 static TypeHandle type(Region* region) { \
250 return BitsetType::New(BitsetType::k##type, region); \
252 BITSET_TYPE_LIST(DEFINE_TYPE_CONSTRUCTOR)
253 #undef DEFINE_TYPE_CONSTRUCTOR
255 static TypeHandle Class(i::Handle<i::Map> map, Region* region) {
256 return ClassType::New(map, region);
258 static TypeHandle Constant(i::Handle<i::Object> value, Region* region) {
259 return ConstantType::New(value, region);
261 static TypeHandle Array(TypeHandle element, Region* region) {
262 return ArrayType::New(element, region);
264 static FunctionHandle Function(
265 TypeHandle result, TypeHandle receiver, int arity, Region* region) {
266 return FunctionType::New(result, receiver, arity, region);
268 static TypeHandle Function(TypeHandle result, Region* region) {
269 return Function(result, Any(region), 0, region);
271 static TypeHandle Function(
272 TypeHandle result, TypeHandle param0, Region* region) {
273 FunctionHandle function = Function(result, Any(region), 1, region);
274 function->InitParameter(0, param0);
277 static TypeHandle Function(
278 TypeHandle result, TypeHandle param0, TypeHandle param1, Region* region) {
279 FunctionHandle function = Function(result, Any(region), 2, region);
280 function->InitParameter(0, param0);
281 function->InitParameter(1, param1);
285 static TypeHandle Union(TypeHandle type1, TypeHandle type2, Region* reg);
286 static TypeHandle Intersect(TypeHandle type1, TypeHandle type2, Region* reg);
288 static TypeHandle Of(i::Object* value, Region* region) {
289 return Config::from_bitset(BitsetType::Lub(value), region);
291 static TypeHandle Of(i::Handle<i::Object> value, Region* region) {
292 return Of(*value, region);
296 return !this->IsBitset() || BitsetType::IsInhabited(this->AsBitset());
299 bool Is(TypeImpl* that) { return this == that || this->SlowIs(that); }
300 template<class TypeHandle>
301 bool Is(TypeHandle that) { return this->Is(*that); }
303 bool Maybe(TypeImpl* that);
304 template<class TypeHandle>
305 bool Maybe(TypeHandle that) { return this->Maybe(*that); }
307 bool Equals(TypeImpl* that) { return this->Is(that) && that->Is(this); }
308 template<class TypeHandle>
309 bool Equals(TypeHandle that) { return this->Equals(*that); }
311 // Equivalent to Constant(value)->Is(this), but avoiding allocation.
312 bool Contains(i::Object* val);
313 bool Contains(i::Handle<i::Object> val) { return this->Contains(*val); }
315 // State-dependent versions of Of and Is that consider subtyping between
316 // a constant and its map class.
317 static TypeHandle NowOf(i::Object* value, Region* region);
318 static TypeHandle NowOf(i::Handle<i::Object> value, Region* region) {
319 return NowOf(*value, region);
321 bool NowIs(TypeImpl* that);
322 template<class TypeHandle>
323 bool NowIs(TypeHandle that) { return this->NowIs(*that); }
324 inline bool NowContains(i::Object* val);
325 bool NowContains(i::Handle<i::Object> val) { return this->NowContains(*val); }
329 bool IsClass() { return Config::is_class(this); }
330 bool IsConstant() { return Config::is_constant(this); }
331 bool IsArray() { return Config::is_struct(this, StructuralType::kArrayTag); }
333 return Config::is_struct(this, StructuralType::kFunctionTag);
336 ClassType* AsClass() { return ClassType::cast(this); }
337 ConstantType* AsConstant() { return ConstantType::cast(this); }
338 ArrayType* AsArray() { return ArrayType::cast(this); }
339 FunctionType* AsFunction() { return FunctionType::cast(this); }
344 template<class T> class Iterator;
345 Iterator<i::Map> Classes() {
346 if (this->IsBitset()) return Iterator<i::Map>();
347 return Iterator<i::Map>(Config::handle(this));
349 Iterator<i::Object> Constants() {
350 if (this->IsBitset()) return Iterator<i::Object>();
351 return Iterator<i::Object>(Config::handle(this));
354 static inline TypeImpl* cast(typename Config::Base* object);
356 template<class OtherTypeImpl>
357 static TypeHandle Convert(
358 typename OtherTypeImpl::TypeHandle type, Region* region);
360 enum PrintDimension { BOTH_DIMS, SEMANTIC_DIM, REPRESENTATION_DIM };
361 void TypePrint(PrintDimension = BOTH_DIMS);
362 void TypePrint(FILE* out, PrintDimension = BOTH_DIMS);
365 template<class> friend class Iterator;
366 template<class> friend class TypeImpl;
369 static typename Config::template Handle<T>::type handle(T* type) {
370 return Config::handle(type);
373 bool IsNone() { return this == None(); }
374 bool IsAny() { return this == Any(); }
375 bool IsBitset() { return Config::is_bitset(this); }
376 bool IsUnion() { return Config::is_struct(this, StructuralType::kUnionTag); }
379 ASSERT(this->IsBitset());
380 return static_cast<BitsetType*>(this)->Bitset();
382 UnionType* AsUnion() { return UnionType::cast(this); }
384 bool SlowIs(TypeImpl* that);
386 bool InUnion(UnionHandle unioned, int current_size);
387 static int ExtendUnion(
388 UnionHandle unioned, TypeHandle t, int current_size);
389 static int ExtendIntersection(
390 UnionHandle unioned, TypeHandle t, TypeHandle other, int current_size);
392 int BitsetGlb() { return BitsetType::Glb(this); }
393 int BitsetLub() { return BitsetType::Lub(this); }
397 template<class Config>
398 class TypeImpl<Config>::BitsetType : public TypeImpl<Config> {
400 friend class TypeImpl<Config>;
403 #define DECLARE_TYPE(type, value) k##type = (value),
404 BITSET_TYPE_LIST(DECLARE_TYPE)
409 int Bitset() { return Config::as_bitset(this); }
411 static BitsetType* New(int bitset) {
412 return static_cast<BitsetType*>(Config::from_bitset(bitset));
414 static TypeHandle New(int bitset, Region* region) {
415 return Config::from_bitset(bitset, region);
418 static bool IsInhabited(int bitset) {
419 return (bitset & kRepresentation) && (bitset & kSemantic);
422 static int Glb(TypeImpl* type); // greatest lower bound that's a bitset
423 static int Lub(TypeImpl* type); // least upper bound that's a bitset
424 static int Lub(i::Object* value);
425 static int Lub(i::Map* map);
427 static const char* Name(int bitset);
428 static void BitsetTypePrint(FILE* out, int bitset);
433 // A structured type contains a tag and a variable number of type fields.
434 template<class Config>
435 class TypeImpl<Config>::StructuralType : public TypeImpl<Config> {
437 template<class> friend class TypeImpl;
438 friend struct ZoneTypeConfig; // For tags.
439 friend struct HeapTypeConfig;
450 return Config::struct_length(Config::as_struct(this));
452 TypeHandle Get(int i) {
453 return Config::struct_get(Config::as_struct(this), i);
455 void Set(int i, TypeHandle type) {
456 Config::struct_set(Config::as_struct(this), i, type);
458 void Shrink(int length) {
459 Config::struct_shrink(Config::as_struct(this), length);
462 static TypeHandle New(Tag tag, int length, Region* region) {
463 return Config::from_struct(Config::struct_create(tag, length, region));
468 template<class Config>
469 class TypeImpl<Config>::ClassType : public TypeImpl<Config> {
471 i::Handle<i::Map> Map() { return Config::as_class(this); }
473 static ClassHandle New(i::Handle<i::Map> map, Region* region) {
474 return Config::template cast<ClassType>(
475 Config::from_class(map, BitsetType::Lub(*map), region));
478 static ClassType* cast(TypeImpl* type) {
479 ASSERT(type->IsClass());
480 return static_cast<ClassType*>(type);
485 template<class Config>
486 class TypeImpl<Config>::ConstantType : public TypeImpl<Config> {
488 i::Handle<i::Object> Value() { return Config::as_constant(this); }
490 static ConstantHandle New(i::Handle<i::Object> value, Region* region) {
491 return Config::template cast<ConstantType>(
492 Config::from_constant(value, BitsetType::Lub(*value), region));
495 static ConstantType* cast(TypeImpl* type) {
496 ASSERT(type->IsConstant());
497 return static_cast<ConstantType*>(type);
503 // A union is a structured type with the following invariants:
504 // - its length is at least 2
505 // - at most one field is a bitset, and it must go into index 0
506 // - no field is a union
507 template<class Config>
508 class TypeImpl<Config>::UnionType : public StructuralType {
510 static UnionHandle New(int length, Region* region) {
511 return Config::template cast<UnionType>(
512 StructuralType::New(StructuralType::kUnionTag, length, region));
515 static UnionType* cast(TypeImpl* type) {
516 ASSERT(type->IsUnion());
517 return static_cast<UnionType*>(type);
522 template<class Config>
523 class TypeImpl<Config>::ArrayType : public StructuralType {
525 TypeHandle Element() { return this->Get(0); }
527 static ArrayHandle New(TypeHandle element, Region* region) {
528 ArrayHandle type = Config::template cast<ArrayType>(
529 StructuralType::New(StructuralType::kArrayTag, 1, region));
530 type->Set(0, element);
534 static ArrayType* cast(TypeImpl* type) {
535 ASSERT(type->IsArray());
536 return static_cast<ArrayType*>(type);
541 template<class Config>
542 class TypeImpl<Config>::FunctionType : public StructuralType {
544 int Arity() { return this->Length() - 2; }
545 TypeHandle Result() { return this->Get(0); }
546 TypeHandle Receiver() { return this->Get(1); }
547 TypeHandle Parameter(int i) { return this->Get(2 + i); }
549 void InitParameter(int i, TypeHandle type) { this->Set(2 + i, type); }
551 static FunctionHandle New(
552 TypeHandle result, TypeHandle receiver, int arity, Region* region) {
553 FunctionHandle type = Config::template cast<FunctionType>(
554 StructuralType::New(StructuralType::kFunctionTag, 2 + arity, region));
555 type->Set(0, result);
556 type->Set(1, receiver);
560 static FunctionType* cast(TypeImpl* type) {
561 ASSERT(type->IsFunction());
562 return static_cast<FunctionType*>(type);
567 template<class Config> template<class T>
568 class TypeImpl<Config>::Iterator {
570 bool Done() const { return index_ < 0; }
571 i::Handle<T> Current();
575 template<class> friend class TypeImpl;
577 Iterator() : index_(-1) {}
578 explicit Iterator(TypeHandle type) : type_(type), index_(-1) {
582 inline bool matches(TypeHandle type);
583 inline TypeHandle get_type();
590 // Zone-allocated types are either (odd) integers to represent bitsets, or
591 // (even) pointers to structures for everything else.
592 struct ZoneTypeConfig {
593 typedef TypeImpl<ZoneTypeConfig> Type;
595 typedef void* Struct;
596 typedef i::Zone Region;
597 template<class T> struct Handle { typedef T* type; };
599 template<class T> static inline T* handle(T* type);
600 template<class T> static inline T* cast(Type* type);
602 static inline bool is_bitset(Type* type);
603 static inline bool is_class(Type* type);
604 static inline bool is_constant(Type* type);
605 static inline bool is_struct(Type* type, int tag);
607 static inline int as_bitset(Type* type);
608 static inline Struct* as_struct(Type* type);
609 static inline i::Handle<i::Map> as_class(Type* type);
610 static inline i::Handle<i::Object> as_constant(Type* type);
612 static inline Type* from_bitset(int bitset);
613 static inline Type* from_bitset(int bitset, Zone* zone);
614 static inline Type* from_struct(Struct* structured);
615 static inline Type* from_class(i::Handle<i::Map> map, int lub, Zone* zone);
616 static inline Type* from_constant(
617 i::Handle<i::Object> value, int lub, Zone* zone);
619 static inline Struct* struct_create(int tag, int length, Zone* zone);
620 static inline void struct_shrink(Struct* structured, int length);
621 static inline int struct_tag(Struct* structured);
622 static inline int struct_length(Struct* structured);
623 static inline Type* struct_get(Struct* structured, int i);
624 static inline void struct_set(Struct* structured, int i, Type* type);
626 static inline int lub_bitset(Type* type);
629 typedef TypeImpl<ZoneTypeConfig> Type;
632 // Heap-allocated types are either smis for bitsets, maps for classes, boxes for
633 // constants, or fixed arrays for unions.
634 struct HeapTypeConfig {
635 typedef TypeImpl<HeapTypeConfig> Type;
636 typedef i::Object Base;
637 typedef i::FixedArray Struct;
638 typedef i::Isolate Region;
639 template<class T> struct Handle { typedef i::Handle<T> type; };
641 template<class T> static inline i::Handle<T> handle(T* type);
642 template<class T> static inline i::Handle<T> cast(i::Handle<Type> type);
644 static inline bool is_bitset(Type* type);
645 static inline bool is_class(Type* type);
646 static inline bool is_constant(Type* type);
647 static inline bool is_struct(Type* type, int tag);
649 static inline int as_bitset(Type* type);
650 static inline i::Handle<i::Map> as_class(Type* type);
651 static inline i::Handle<i::Object> as_constant(Type* type);
652 static inline i::Handle<Struct> as_struct(Type* type);
654 static inline Type* from_bitset(int bitset);
655 static inline i::Handle<Type> from_bitset(int bitset, Isolate* isolate);
656 static inline i::Handle<Type> from_class(
657 i::Handle<i::Map> map, int lub, Isolate* isolate);
658 static inline i::Handle<Type> from_constant(
659 i::Handle<i::Object> value, int lub, Isolate* isolate);
660 static inline i::Handle<Type> from_struct(i::Handle<Struct> structured);
662 static inline i::Handle<Struct> struct_create(
663 int tag, int length, Isolate* isolate);
664 static inline void struct_shrink(i::Handle<Struct> structured, int length);
665 static inline int struct_tag(i::Handle<Struct> structured);
666 static inline int struct_length(i::Handle<Struct> structured);
667 static inline i::Handle<Type> struct_get(i::Handle<Struct> structured, int i);
668 static inline void struct_set(
669 i::Handle<Struct> structured, int i, i::Handle<Type> type);
671 static inline int lub_bitset(Type* type);
674 typedef TypeImpl<HeapTypeConfig> HeapType;
677 // A simple struct to represent a pair of lower/upper type bounds.
678 template<class Config>
680 typedef TypeImpl<Config> Type;
681 typedef typename Type::TypeHandle TypeHandle;
682 typedef typename Type::Region Region;
688 explicit BoundsImpl(TypeHandle t) : lower(t), upper(t) {}
689 BoundsImpl(TypeHandle l, TypeHandle u) : lower(l), upper(u) {
690 ASSERT(lower->Is(upper));
693 // Unrestricted bounds.
694 static BoundsImpl Unbounded(Region* region) {
695 return BoundsImpl(Type::None(region), Type::Any(region));
698 // Meet: both b1 and b2 are known to hold.
699 static BoundsImpl Both(BoundsImpl b1, BoundsImpl b2, Region* region) {
700 TypeHandle lower = Type::Union(b1.lower, b2.lower, region);
701 TypeHandle upper = Type::Intersect(b1.upper, b2.upper, region);
702 // Lower bounds are considered approximate, correct as necessary.
703 lower = Type::Intersect(lower, upper, region);
704 return BoundsImpl(lower, upper);
707 // Join: either b1 or b2 is known to hold.
708 static BoundsImpl Either(BoundsImpl b1, BoundsImpl b2, Region* region) {
709 TypeHandle lower = Type::Intersect(b1.lower, b2.lower, region);
710 TypeHandle upper = Type::Union(b1.upper, b2.upper, region);
711 return BoundsImpl(lower, upper);
714 static BoundsImpl NarrowLower(BoundsImpl b, TypeHandle t, Region* region) {
715 // Lower bounds are considered approximate, correct as necessary.
716 t = Type::Intersect(t, b.upper, region);
717 TypeHandle lower = Type::Union(b.lower, t, region);
718 return BoundsImpl(lower, b.upper);
720 static BoundsImpl NarrowUpper(BoundsImpl b, TypeHandle t, Region* region) {
721 TypeHandle lower = Type::Intersect(b.lower, t, region);
722 TypeHandle upper = Type::Intersect(b.upper, t, region);
723 return BoundsImpl(lower, upper);
726 bool Narrows(BoundsImpl that) {
727 return that.lower->Is(this->lower) && this->upper->Is(that.upper);
731 typedef BoundsImpl<ZoneTypeConfig> Bounds;
733 } } // namespace v8::internal
735 #endif // V8_TYPES_H_