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// Copyright (c) 2012, the Dart project authors. Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.
#include <limits>
#include "platform/assert.h"
#include "platform/globals.h"
#include "vm/allocation.h"
#include "vm/growable_array.h"
#include "vm/object.h"
#include "vm/raw_object.h"
#include "vm/symbols.h"
#include "vm/token.h"
namespace dart {
class CompileType;
class LocalScope;
// Indices of [LocalVariable]s are abstract and have little todo with the
// actual frame layout!
// There are generally 4 different kinds of [LocalVariable]s:
// a) [LocalVariable]s refering to a parameter: The indices for those
// variables are assigned by the flow graph builder. Parameter n gets
// assigned the index (function.num_parameters - n - 1). I.e. the last
// parameter has index 1.
// b) [LocalVariable]s referring to actual variables in the body of a
// function (either from Dart code or specially injected ones. The
// indices of those variables are assigned by the scope builder
// from 0, -1, ... -(M-1) for M local variables.
// -> These variables participate in full SSA renaming and can therefore
// be used with [StoreLocalInstr]s (in addition to [LoadLocal]s).
// c) [LocalVariable]s referring to values on the expression stack. Those are
// assigned by the flow graph builder. The indices of those variables are
// assigned by the flow graph builder (it simulates the expression stack
// height), they go from -NumVariabables - ExpressionHeight.
// -> These variables participate only partially in SSA renaming and can
// therefore only be used with [LoadLocalInstr]s and with
// [StoreLocalInstr]s **where no phis are necessary**.
// b) [LocalVariable]s referring to captured variables. Those are never
// loaded/stored directly. Their only purpose is to tell the flow graph
// builder how many parent links to follow and into which context index to
// store. The indices of those variables are assigned by the scope
// builder and they refer to indices into context objects.
class VariableIndex {
static const int kInvalidIndex = std::numeric_limits<int>::min();
explicit VariableIndex(int value = kInvalidIndex) : value_(value) {}
int operator==(const VariableIndex& other) { return value_ == other.value_; }
bool IsValid() const { return value_ != kInvalidIndex; }
int value() const { return value_; }
int value_;
class LocalVariable : public ZoneAllocated {
LocalVariable(TokenPosition declaration_pos,
TokenPosition token_pos,
const String& name,
const AbstractType& type,
CompileType* parameter_type = NULL)
: declaration_pos_(declaration_pos),
index_() {
ASSERT(type.IsZoneHandle() || type.IsReadOnlyHandle());
TokenPosition token_pos() const { return token_pos_; }
TokenPosition declaration_token_pos() const { return declaration_pos_; }
const String& name() const { return name_; }
LocalScope* owner() const { return owner_; }
void set_owner(LocalScope* owner) {
ASSERT(owner_ == NULL);
owner_ = owner;
const AbstractType& type() const { return type_; }
CompileType* parameter_type() const { return parameter_type_; }
bool is_final() const { return is_final_; }
void set_is_final() { is_final_ = true; }
bool is_captured() const { return is_captured_; }
void set_is_captured() { is_captured_ = true; }
// Variables marked as forced to stack are skipped and not captured by
// CaptureLocalVariables - which iterates scope chain between two scopes
// and indiscriminately marks all variables as captured.
// TODO(27590) remove the hardcoded blacklist from CaptureLocalVariables
bool is_forced_stack() const { return is_forced_stack_; }
void set_is_forced_stack() { is_forced_stack_ = true; }
enum TypeCheckMode {
// Returns true if this local variable represents a parameter that needs type
// check when we enter the function.
bool needs_type_check() const {
return (type_check_mode_ == kDoTypeCheck) && !FLAG_omit_strong_type_checks;
// Returns true if this local variable represents a parameter which type is
// guaranteed by the caller.
bool was_type_checked_by_caller() const {
return type_check_mode_ == kTypeCheckedByCaller;
void set_type_check_mode(TypeCheckMode mode) { type_check_mode_ = mode; }
bool HasIndex() const { return index_.IsValid(); }
VariableIndex index() const {
return index_;
// Assign an index to a local.
void set_index(VariableIndex index) {
index_ = index;
void set_invisible(bool value) { is_invisible_ = value; }
bool is_invisible() const { return is_invisible_; }
bool is_captured_parameter() const { return is_captured_parameter_; }
void set_is_captured_parameter(bool value) { is_captured_parameter_ = value; }
// By convention, internal variables start with a colon.
bool IsInternal() const { return name_.CharAt(0) == ':'; }
bool IsConst() const { return const_value_ != NULL; }
void SetConstValue(const Instance& value) {
ASSERT(value.IsZoneHandle() || value.IsReadOnlyHandle());
const_value_ = &value;
const Instance* ConstValue() const {
return const_value_;
bool Equals(const LocalVariable& other) const;
static const int kUninitializedIndex = INT_MIN;
const TokenPosition declaration_pos_;
const TokenPosition token_pos_;
const String& name_;
LocalScope* owner_; // Local scope declaring this variable.
const AbstractType& type_; // Declaration type of local variable.
CompileType* const parameter_type_; // NULL or incoming parameter type.
const Instance* const_value_; // NULL or compile-time const value.
bool is_final_; // If true, this variable is readonly.
bool is_captured_; // If true, this variable lives in the context, otherwise
// in the stack frame.
bool is_invisible_;
bool is_captured_parameter_;
bool is_forced_stack_;
TypeCheckMode type_check_mode_;
VariableIndex index_;
friend class LocalScope;
class NameReference : public ZoneAllocated {
NameReference(TokenPosition token_pos, const String& name)
: token_pos_(token_pos), name_(name) {
const String& name() const { return name_; }
TokenPosition token_pos() const { return token_pos_; }
void set_token_pos(TokenPosition value) { token_pos_ = value; }
TokenPosition token_pos_;
const String& name_;
class SourceLabel : public ZoneAllocated {
enum Kind {
kStatement // Any statement other than the above
SourceLabel(TokenPosition token_pos, const String& name, Kind kind)
: token_pos_(token_pos), name_(name), owner_(NULL), kind_(kind) {
static SourceLabel* New(TokenPosition token_pos, String* name, Kind kind) {
if (name != NULL) {
return new SourceLabel(token_pos, *name, kind);
} else {
return new SourceLabel(token_pos, Symbols::DefaultLabel(), kind);
TokenPosition token_pos() const { return token_pos_; }
const String& name() const { return name_; }
LocalScope* owner() const { return owner_; }
void set_owner(LocalScope* owner) { owner_ = owner; }
Kind kind() const { return kind_; }
// Returns the function level of the scope in which the label is defined.
int FunctionLevel() const;
bool IsUnresolved() { return kind_ == kForward; }
void ResolveForwardReference() { kind_ = kCase; }
const TokenPosition token_pos_;
const String& name_;
LocalScope* owner_; // Local scope declaring this label.
Kind kind_;
class LocalScope : public ZoneAllocated {
LocalScope(LocalScope* parent, int function_level, int loop_level);
LocalScope* parent() const { return parent_; }
LocalScope* child() const { return child_; }
LocalScope* sibling() const { return sibling_; }
int function_level() const { return function_level_; }
int loop_level() const { return loop_level_; }
// Check if this scope is nested within the passed in scope.
bool IsNestedWithin(LocalScope* scope) const;
// The context level is only set in a scope that is either the owner scope of
// a captured variable or that is the owner scope of a context.
bool HasContextLevel() const {
return context_level_ != kUnitializedContextLevel;
int context_level() const {
return context_level_;
void set_context_level(int context_level) {
ASSERT(context_level != kUnitializedContextLevel);
context_level_ = context_level;
TokenPosition begin_token_pos() const { return begin_token_pos_; }
void set_begin_token_pos(TokenPosition value) { begin_token_pos_ = value; }
TokenPosition end_token_pos() const { return end_token_pos_; }
void set_end_token_pos(TokenPosition value) { end_token_pos_ = value; }
// The number of variables allocated in the context and belonging to this
// scope and to its children at the same loop level.
int num_context_variables() const { return num_context_variables_; }
// Add a variable to the scope. Returns false if a variable with the
// same name is already present.
bool AddVariable(LocalVariable* variable);
// Insert a formal parameter variable to the scope at the given position,
// possibly in front of aliases already added with AddVariable.
// Returns false if a variable with the same name is already present.
bool InsertParameterAt(intptr_t pos, LocalVariable* parameter);
// Add a label to the scope. Returns false if a label with the same name
// is already present.
bool AddLabel(SourceLabel* label);
// Move an unresolved label of a switch case label to an outer switch.
void MoveLabel(SourceLabel* label);
// Lookup a variable in this scope only.
LocalVariable* LocalLookupVariable(const String& name) const;
// Lookup a label in this scope only.
SourceLabel* LocalLookupLabel(const String& name) const;
// Lookup a variable in this scope and its parents. If the variable
// is found in a parent scope and 'test_only' is not true, we insert
// aliases of the variable in the current and intermediate scopes up to
// the declaration scope in order to detect "used before declared" errors.
// We mark a variable as 'captured' when applicable.
LocalVariable* LookupVariable(const String& name, bool test_only);
// Lookup a label in this scope and its parents.
SourceLabel* LookupLabel(const String& name);
// Lookup the "innermost" label that labels a for, while, do, or switch
// statement.
SourceLabel* LookupInnermostLabel(Token::Kind jump_kind);
// Lookup scope of outer switch statement at same function level.
// Returns NULL if this scope is not embedded in a switch.
LocalScope* LookupSwitchScope();
// Mark this variable as captured by this scope.
void CaptureVariable(LocalVariable* variable);
// Look for unresolved forward references to labels in this scope.
// If there are any, propagate the forward reference to the next
// outer scope of a switch statement. If there is no outer switch
// statement, return the first unresolved label found.
SourceLabel* CheckUnresolvedLabels();
// Accessing the variables in the scope.
intptr_t num_variables() const { return variables_.length(); }
LocalVariable* VariableAt(intptr_t index) const {
ASSERT((index >= 0) && (index < variables_.length()));
return variables_[index];
// Count the captured variables belonging to outer scopes and referenced in
// this local scope.
int NumCapturedVariables() const;
// Add a reference to the given name into this scope and the enclosing
// scopes that do not have a local variable declaration for this name
// already.
void AddReferencedName(TokenPosition token_pos, const String& name);
TokenPosition PreviousReferencePos(const String& name) const;
// Allocate both captured and non-captured variables declared in this scope
// and in its children scopes of the same function level. Allocating means
// assigning a frame slot index or a context slot index.
// Parameters to be allocated in the frame must all appear in the top scope
// and not in its children (we do not yet handle register parameters).
// Locals must be listed after parameters in top scope and in its children.
// Two locals in different sibling scopes may share the same frame slot.
// Return the index of the next available frame slot.
VariableIndex AllocateVariables(VariableIndex first_parameter_index,
int num_parameters,
VariableIndex first_local_index,
LocalScope* context_owner,
bool* found_captured_variables);
// Creates variable info for the scope and all its nested scopes.
// Must be called after AllocateVariables() has been called.
RawLocalVarDescriptors* GetVarDescriptors(
const Function& func,
ZoneGrowableArray<intptr_t>* context_level_array);
// Create a ContextScope object describing all captured variables referenced
// from this scope and belonging to outer scopes.
RawContextScope* PreserveOuterScope(int current_context_level) const;
// Mark all local variables that are accessible from this scope up to
// top_scope (included) as captured unless they are marked as forced to stack.
void CaptureLocalVariables(LocalScope* top_scope);
// Creates a LocalScope representing the outer scope of a local function to be
// compiled. This outer scope contains the variables captured by the function
// as specified by the given ContextScope, which was created during the
// compilation of the enclosing function.
static LocalScope* RestoreOuterScope(const ContextScope& context_scope);
// Create a ContextScope object which will capture "this" for an implicit
// closure object.
static RawContextScope* CreateImplicitClosureScope(const Function& func);
struct VarDesc {
const String* name;
RawLocalVarDescriptors::VarInfo info;
// Allocate the variable in the current context, possibly updating the current
// context owner scope, if the variable is the first one to be allocated at
// this loop level.
// The variable may belong to this scope or to any of its children, but at the
// same loop level.
void AllocateContextVariable(LocalVariable* variable,
LocalScope** context_owner);
void CollectLocalVariables(GrowableArray<VarDesc>* vars, int16_t* scope_id);
NameReference* FindReference(const String& name) const;
static const int kUnitializedContextLevel = INT_MIN;
LocalScope* parent_;
LocalScope* child_;
LocalScope* sibling_;
int function_level_; // Reflects the nesting level of local functions.
int loop_level_; // Reflects the loop nesting level.
int context_level_; // Reflects the level of the runtime context.
int num_context_variables_; // Only set if this scope is a context owner.
TokenPosition begin_token_pos_; // Token index of beginning of scope.
TokenPosition end_token_pos_; // Token index of end of scope.
GrowableArray<LocalVariable*> variables_;
GrowableArray<SourceLabel*> labels_;
// List of names referenced in this scope and its children that
// are not resolved to local variables.
GrowableArray<NameReference*> referenced_;
} // namespace dart