LCOV - code coverage report
Current view: top level - src/ast - variables.h (source / functions) Hit Total Coverage
Test: app.info Lines: 37 37 100.0 %
Date: 2019-02-19 Functions: 14 15 93.3 %

          Line data    Source code
       1             : // Copyright 2011 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.
       4             : 
       5             : #ifndef V8_AST_VARIABLES_H_
       6             : #define V8_AST_VARIABLES_H_
       7             : 
       8             : #include "src/ast/ast-value-factory.h"
       9             : #include "src/globals.h"
      10             : #include "src/zone/zone.h"
      11             : 
      12             : namespace v8 {
      13             : namespace internal {
      14             : 
      15             : // The AST refers to variables via VariableProxies - placeholders for the actual
      16             : // variables. Variables themselves are never directly referred to from the AST,
      17             : // they are maintained by scopes, and referred to from VariableProxies and Slots
      18             : // after binding and variable allocation.
      19             : class Variable final : public ZoneObject {
      20             :  public:
      21             :   Variable(Scope* scope, const AstRawString* name, VariableMode mode,
      22             :            VariableKind kind, InitializationFlag initialization_flag,
      23             :            MaybeAssignedFlag maybe_assigned_flag = kNotAssigned)
      24             :       : scope_(scope),
      25             :         name_(name),
      26             :         local_if_not_shadowed_(nullptr),
      27             :         next_(nullptr),
      28             :         index_(-1),
      29             :         initializer_position_(kNoSourcePosition),
      30             :         bit_field_(MaybeAssignedFlagField::encode(maybe_assigned_flag) |
      31             :                    InitializationFlagField::encode(initialization_flag) |
      32             :                    VariableModeField::encode(mode) |
      33             :                    IsUsedField::encode(false) |
      34             :                    ForceContextAllocationField::encode(false) |
      35             :                    ForceHoleInitializationField::encode(false) |
      36             :                    LocationField::encode(VariableLocation::UNALLOCATED) |
      37   168519151 :                    VariableKindField::encode(kind)) {
      38             :     // Var declared variables never need initialization.
      39             :     DCHECK(!(mode == VariableMode::kVar &&
      40             :              initialization_flag == kNeedsInitialization));
      41             :   }
      42             : 
      43             :   explicit Variable(Variable* other);
      44             : 
      45             :   // The source code for an eval() call may refer to a variable that is
      46             :   // in an outer scope about which we don't know anything (it may not
      47             :   // be the script scope). scope() is nullptr in that case. Currently the
      48             :   // scope is only used to follow the context chain length.
      49             :   Scope* scope() const { return scope_; }
      50             : 
      51             :   // This is for adjusting the scope of temporaries used when desugaring
      52             :   // parameter initializers.
      53          12 :   void set_scope(Scope* scope) { scope_ = scope; }
      54             : 
      55    12504946 :   Handle<String> name() const { return name_->string(); }
      56        1120 :   const AstRawString* raw_name() const { return name_; }
      57             :   VariableMode mode() const { return VariableModeField::decode(bit_field_); }
      58             :   bool has_forced_context_allocation() const {
      59             :     return ForceContextAllocationField::decode(bit_field_);
      60             :   }
      61      145723 :   void ForceContextAllocation() {
      62             :     DCHECK(IsUnallocated() || IsContextSlot() || IsLookupSlot() ||
      63             :            location() == VariableLocation::MODULE);
      64     7902723 :     bit_field_ = ForceContextAllocationField::update(bit_field_, true);
      65      145723 :   }
      66             :   bool is_used() { return IsUsedField::decode(bit_field_); }
      67   175033673 :   void set_is_used() { bit_field_ = IsUsedField::update(bit_field_, true); }
      68             :   MaybeAssignedFlag maybe_assigned() const {
      69             :     return MaybeAssignedFlagField::decode(bit_field_);
      70             :   }
      71       18108 :   void set_maybe_assigned() {
      72    26051046 :     bit_field_ = MaybeAssignedFlagField::update(bit_field_, kMaybeAssigned);
      73       18108 :   }
      74             : 
      75             :   int initializer_position() { return initializer_position_; }
      76    17013646 :   void set_initializer_position(int pos) { initializer_position_ = pos; }
      77             : 
      78    22824817 :   bool IsUnallocated() const {
      79     2664858 :     return location() == VariableLocation::UNALLOCATED;
      80             :   }
      81             :   bool IsParameter() const { return location() == VariableLocation::PARAMETER; }
      82          35 :   bool IsStackLocal() const { return location() == VariableLocation::LOCAL; }
      83     4736297 :   bool IsStackAllocated() const { return IsParameter() || IsStackLocal(); }
      84      201303 :   bool IsContextSlot() const { return location() == VariableLocation::CONTEXT; }
      85             :   bool IsLookupSlot() const { return location() == VariableLocation::LOOKUP; }
      86             :   bool IsGlobalObjectProperty() const;
      87             : 
      88     7293587 :   bool is_dynamic() const { return IsDynamicVariableMode(mode()); }
      89             : 
      90             :   // Returns the InitializationFlag this Variable was created with.
      91             :   // Scope analysis may allow us to relax this initialization
      92             :   // requirement, which will be reflected in the return value of
      93             :   // binding_needs_init().
      94             :   InitializationFlag initialization_flag() const {
      95             :     return InitializationFlagField::decode(bit_field_);
      96             :   }
      97             : 
      98             :   // Whether this variable needs to be initialized with the hole at
      99             :   // declaration time. Only returns valid results after scope analysis.
     100     4779727 :   bool binding_needs_init() const {
     101             :     DCHECK_IMPLIES(initialization_flag() == kNeedsInitialization,
     102             :                    IsLexicalVariableMode(mode()));
     103             :     DCHECK_IMPLIES(ForceHoleInitializationField::decode(bit_field_),
     104             :                    initialization_flag() == kNeedsInitialization);
     105             : 
     106             :     // Always initialize if hole initialization was forced during
     107             :     // scope analysis.
     108     9559454 :     if (ForceHoleInitializationField::decode(bit_field_)) return true;
     109             : 
     110             :     // If initialization was not forced, no need for initialization
     111             :     // for stack allocated variables, since UpdateNeedsHoleCheck()
     112             :     // in scopes.cc has proven that no VariableProxy refers to
     113             :     // this variable in such a way that a runtime hole check
     114             :     // would be generated.
     115     4736297 :     if (IsStackAllocated()) return false;
     116             : 
     117             :     // Otherwise, defer to the flag set when this Variable was constructed.
     118     1421931 :     return initialization_flag() == kNeedsInitialization;
     119             :   }
     120             : 
     121             :   // Called during scope analysis when a VariableProxy is found to
     122             :   // reference this Variable in such a way that a hole check will
     123             :   // be required at runtime.
     124             :   void ForceHoleInitialization() {
     125             :     DCHECK_EQ(kNeedsInitialization, initialization_flag());
     126             :     DCHECK(IsLexicalVariableMode(mode()));
     127     1186444 :     bit_field_ = ForceHoleInitializationField::update(bit_field_, true);
     128             :   }
     129             : 
     130       32932 :   bool throw_on_const_assignment(LanguageMode language_mode) const {
     131       32932 :     return kind() != SLOPPY_FUNCTION_NAME_VARIABLE || is_strict(language_mode);
     132             :   }
     133             : 
     134     2508976 :   bool is_this() const { return kind() == THIS_VARIABLE; }
     135             :   bool is_sloppy_function_name() const {
     136             :     return kind() == SLOPPY_FUNCTION_NAME_VARIABLE;
     137             :   }
     138             : 
     139      131554 :   bool is_parameter() const { return kind() == PARAMETER_VARIABLE; }
     140         712 :   bool is_sloppy_block_function() {
     141             :     return kind() == SLOPPY_BLOCK_FUNCTION_VARIABLE;
     142             :   }
     143             : 
     144             :   Variable* local_if_not_shadowed() const {
     145             :     DCHECK(mode() == VariableMode::kDynamicLocal &&
     146             :            local_if_not_shadowed_ != nullptr);
     147             :     return local_if_not_shadowed_;
     148             :   }
     149             : 
     150             :   void set_local_if_not_shadowed(Variable* local) {
     151        4426 :     local_if_not_shadowed_ = local;
     152             :   }
     153             : 
     154             :   VariableLocation location() const {
     155             :     return LocationField::decode(bit_field_);
     156             :   }
     157             :   VariableKind kind() const { return VariableKindField::decode(bit_field_); }
     158             : 
     159             :   int index() const { return index_; }
     160             : 
     161             :   bool IsReceiver() const {
     162             :     DCHECK(IsParameter());
     163             : 
     164             :     return index_ == -1;
     165             :   }
     166             : 
     167       19830 :   bool IsExport() const {
     168             :     DCHECK_EQ(location(), VariableLocation::MODULE);
     169             :     DCHECK_NE(index(), 0);
     170             :     return index() > 0;
     171             :   }
     172             : 
     173     4758092 :   void AllocateTo(VariableLocation location, int index) {
     174             :     DCHECK(IsUnallocated() ||
     175             :            (this->location() == location && this->index() == index));
     176             :     DCHECK_IMPLIES(location == VariableLocation::MODULE, index != 0);
     177    25894868 :     bit_field_ = LocationField::update(bit_field_, location);
     178             :     DCHECK_EQ(location, this->location());
     179    12947434 :     index_ = index;
     180     4758092 :   }
     181             : 
     182             :   void MakeParameterNonSimple() {
     183             :     DCHECK(is_parameter());
     184       81026 :     bit_field_ = VariableModeField::update(bit_field_, VariableMode::kLet);
     185             :     bit_field_ =
     186       81026 :         InitializationFlagField::update(bit_field_, kNeedsInitialization);
     187             :   }
     188             : 
     189             :   static InitializationFlag DefaultInitializationFlag(VariableMode mode) {
     190             :     DCHECK(IsDeclaredVariableMode(mode));
     191             :     return mode == VariableMode::kVar ? kCreatedInitialized
     192    10377861 :                                       : kNeedsInitialization;
     193             :   }
     194             : 
     195             :   typedef base::ThreadedList<Variable> List;
     196             : 
     197             :  private:
     198             :   Scope* scope_;
     199             :   const AstRawString* name_;
     200             : 
     201             :   // If this field is set, this variable references the stored locally bound
     202             :   // variable, but it might be shadowed by variable bindings introduced by
     203             :   // sloppy 'eval' calls between the reference scope (inclusive) and the
     204             :   // binding scope (exclusive).
     205             :   Variable* local_if_not_shadowed_;
     206             :   Variable* next_;
     207             :   int index_;
     208             :   int initializer_position_;
     209             :   uint16_t bit_field_;
     210             : 
     211             :   class VariableModeField : public BitField16<VariableMode, 0, 3> {};
     212             :   class VariableKindField
     213             :       : public BitField16<VariableKind, VariableModeField::kNext, 3> {};
     214             :   class LocationField
     215             :       : public BitField16<VariableLocation, VariableKindField::kNext, 3> {};
     216             :   class ForceContextAllocationField
     217             :       : public BitField16<bool, LocationField::kNext, 1> {};
     218             :   class IsUsedField
     219             :       : public BitField16<bool, ForceContextAllocationField::kNext, 1> {};
     220             :   class InitializationFlagField
     221             :       : public BitField16<InitializationFlag, IsUsedField::kNext, 1> {};
     222             :   class ForceHoleInitializationField
     223             :       : public BitField16<bool, InitializationFlagField::kNext, 1> {};
     224             :   class MaybeAssignedFlagField
     225             :       : public BitField16<MaybeAssignedFlag,
     226             :                           ForceHoleInitializationField::kNext, 1> {};
     227             :   Variable** next() { return &next_; }
     228             :   friend List;
     229             :   friend base::ThreadedListTraits<Variable>;
     230             : };
     231             : }  // namespace internal
     232             : }  // namespace v8
     233             : 
     234             : #endif  // V8_AST_VARIABLES_H_

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