dart-sdk/runtime/vm/scopes.cc
Martin Kustermann 587e6308bf [vm] Fix expression evaluation in context of closures
When evaluating an expressino at a breakpoint that's inside a closure,
the closure may refer to anything it closes over. That includes the
`this` from an enclosing method.

So depending on whether a closure's parent chain is an instance method
or a static method, the expression evaluation function is going to be an
instance method or a static method.

=> We walk up the parent chain to determine the correct enclosing class.
=> This avoids making a Type object with a cid from a top-level class (see [0])

Handling this correctly will now try to get the `this` when invoking an
eval function that has an enclosing instance method. Though we may often
have "<optimized out>" the `this` (e.g. due to not capturing it in
closure context chain).

=> We still allow running the expression evaluation function in this
case, but only if the expression being evaluated doesn't access `this`.

A similar issue occurs when trying to use variables in the eval
expression that the closure didn't capture. This results in a confusing
CFE compile-time error. This is a separate issue and tracked in [1].

=> We update the test to distinuish the cases that this CL makes passing
and those that are failing due to [1].

Fixes [0] https://github.com/dart-lang/sdk/issues/53061
See also [1] https://github.com/dart-lang/sdk/issues/53087

TEST=Fixes part of service/evaluate_activation_test failures

Change-Id: I3bb24e7338c7b2f12d5340311d944cb59a455641
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/317540
Reviewed-by: Alexander Markov <alexmarkov@google.com>
Reviewed-by: Slava Egorov <vegorov@google.com>
Commit-Queue: Martin Kustermann <kustermann@google.com>
2023-08-04 11:07:46 +00:00

686 lines
26 KiB
C++

// 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.
#if !defined(DART_PRECOMPILED_RUNTIME)
#include "vm/scopes.h"
#include "vm/compiler/backend/slot.h"
#include "vm/kernel.h"
#include "vm/object.h"
#include "vm/object_store.h"
#include "vm/stack_frame.h"
#include "vm/symbols.h"
namespace dart {
DEFINE_FLAG(bool,
share_enclosing_context,
true,
"Allocate captured variables in the existing context of an "
"enclosing scope (up to innermost loop) and spare the allocation "
"of a local context.");
LocalScope::LocalScope(LocalScope* parent, int function_level, int loop_level)
: parent_(parent),
child_(nullptr),
sibling_(nullptr),
function_level_(function_level),
loop_level_(loop_level),
context_level_(LocalScope::kUninitializedContextLevel),
begin_token_pos_(TokenPosition::kNoSource),
end_token_pos_(TokenPosition::kNoSource),
variables_(),
context_variables_(),
context_slots_(new(Thread::Current()->zone())
ZoneGrowableArray<const Slot*>()) {
// Hook this node into the children of the parent, unless the parent has a
// different function_level, since the local scope of a nested function can
// be discarded after it has been parsed.
if ((parent != nullptr) && (parent->function_level() == function_level)) {
sibling_ = parent->child_;
parent->child_ = this;
}
}
bool LocalScope::IsNestedWithin(LocalScope* scope) const {
const LocalScope* current_scope = this;
while (current_scope != nullptr) {
if (current_scope == scope) {
return true;
}
current_scope = current_scope->parent();
}
return false;
}
bool LocalScope::AddVariable(LocalVariable* variable) {
ASSERT(variable != nullptr);
if (LocalLookupVariable(variable->name(), variable->kernel_offset()) !=
nullptr) {
return false;
}
variables_.Add(variable);
if (variable->owner() == nullptr) {
// Variables must be added to their owner scope first. Subsequent calls
// to 'add' treat the variable as an alias.
variable->set_owner(this);
}
return true;
}
bool LocalScope::InsertParameterAt(intptr_t pos, LocalVariable* parameter) {
ASSERT(parameter != nullptr);
if (LocalLookupVariable(parameter->name(), parameter->kernel_offset()) !=
nullptr) {
return false;
}
variables_.InsertAt(pos, parameter);
// InsertParameterAt is not used to add aliases of parameters.
ASSERT(parameter->owner() == nullptr);
parameter->set_owner(this);
return true;
}
void LocalScope::AllocateContextVariable(LocalVariable* variable,
LocalScope** context_owner) {
ASSERT(variable->is_captured());
ASSERT(variable->owner() == this);
// The context level in the owner scope of a captured variable indicates at
// code generation time how far to walk up the context chain in order to
// access the variable from the current context level.
if ((*context_owner) == nullptr) {
ASSERT(num_context_variables() == 0);
// This scope becomes the current context owner.
set_context_level(1);
*context_owner = this;
} else if (!FLAG_share_enclosing_context && ((*context_owner) != this)) {
// The captured variable is in a child scope of the context owner and we do
// not share contexts.
// This scope will allocate and chain a new context.
ASSERT(num_context_variables() == 0);
// This scope becomes the current context owner.
set_context_level((*context_owner)->context_level() + 1);
*context_owner = this;
} else if ((*context_owner)->loop_level() < loop_level()) {
ASSERT(FLAG_share_enclosing_context);
// The captured variable is at a deeper loop level than the current context.
// This scope will allocate and chain a new context.
ASSERT(num_context_variables() == 0);
// This scope becomes the current context owner.
set_context_level((*context_owner)->context_level() + 1);
*context_owner = this;
} else {
// Allocate the captured variable in the current context.
if (!HasContextLevel()) {
ASSERT(variable->owner() != *context_owner);
set_context_level((*context_owner)->context_level());
} else {
ASSERT(context_level() == (*context_owner)->context_level());
}
}
(*context_owner)->AddContextVariable(variable);
}
void LocalScope::AddContextVariable(LocalVariable* variable) {
variable->set_index(VariableIndex(context_variables_.length()));
context_variables_.Add(variable);
context_slots_->Add(
&Slot::GetContextVariableSlotFor(Thread::Current(), *variable));
}
VariableIndex LocalScope::AllocateVariables(const Function& function,
VariableIndex first_parameter_index,
int num_parameters,
VariableIndex first_local_index,
LocalScope* context_owner,
bool* found_captured_variables) {
// We should not allocate variables of nested functions while compiling an
// enclosing function.
ASSERT(function_level() == 0);
ASSERT(num_parameters >= 0);
// Parameters must be listed first and must all appear in the top scope.
ASSERT(num_parameters <= num_variables());
int pos = 0; // Current variable position.
VariableIndex next_index =
first_parameter_index; // Current free frame index.
LocalVariable* suspend_state_var = nullptr;
for (intptr_t i = 0; i < num_variables(); i++) {
LocalVariable* variable = VariableAt(i);
if (variable->owner() == this &&
variable->name().Equals(Symbols::SuspendStateVar())) {
ASSERT(!variable->is_captured());
suspend_state_var = variable;
}
}
if (suspend_state_var != nullptr) {
suspend_state_var->set_index(
VariableIndex(SuspendState::kSuspendStateVarIndex));
ASSERT(next_index.value() == SuspendState::kSuspendStateVarIndex - 1);
}
while (pos < num_parameters) {
LocalVariable* parameter = VariableAt(pos);
pos++;
// Parsing formal parameter default values may add local variable aliases
// to the local scope before the formal parameters are added. However,
// the parameters get inserted in front of the aliases, therefore, no
// aliases can be encountered among the first num_parameters variables.
ASSERT(parameter->owner() == this);
if (parameter->is_captured()) {
// A captured parameter has a slot allocated in the frame and one in the
// context, where it gets copied to. The parameter index reflects the
// context allocation index.
next_index = VariableIndex(next_index.value() - 1);
AllocateContextVariable(parameter, &context_owner);
*found_captured_variables = true;
} else {
parameter->set_index(next_index);
next_index = VariableIndex(next_index.value() - 1);
}
}
// No overlapping of parameters and locals.
ASSERT(next_index.value() >= first_local_index.value());
next_index = first_local_index;
for (; pos < num_variables(); pos++) {
LocalVariable* variable = VariableAt(pos);
if (variable == suspend_state_var) {
continue;
}
if (variable->owner() == this) {
if (variable->is_captured()) {
AllocateContextVariable(variable, &context_owner);
*found_captured_variables = true;
} else {
variable->set_index(next_index);
next_index = VariableIndex(next_index.value() - 1);
}
}
}
// Allocate variables of all children.
VariableIndex min_index = next_index;
LocalScope* child = this->child();
while (child != nullptr) {
// Ignored, since no parameters.
const VariableIndex dummy_parameter_index(0);
// No parameters in children scopes.
const int num_parameters_in_child = 0;
VariableIndex child_next_index = child->AllocateVariables(
function, dummy_parameter_index, num_parameters_in_child, next_index,
context_owner, found_captured_variables);
if (child_next_index.value() < min_index.value()) {
min_index = child_next_index;
}
child = child->sibling();
}
return min_index;
}
// VM creates internal variables that start with ":"
bool LocalVariable::IsFilteredIdentifier(const String& name) {
ASSERT(name.Length() > 0);
if (name.ptr() == Symbols::FunctionTypeArgumentsVar().ptr()) {
// Keep :function_type_arguments for accessing type variables in debugging.
return false;
}
return name.CharAt(0) == ':';
}
LocalVarDescriptorsPtr LocalScope::GetVarDescriptors(
const Function& func,
ZoneGrowableArray<intptr_t>* context_level_array) {
LocalVarDescriptorsBuilder vars;
vars.AddDeoptIdToContextLevelMappings(context_level_array);
// First enter all variables from scopes of outer functions.
const ContextScope& context_scope =
ContextScope::Handle(func.context_scope());
if (!context_scope.IsNull()) {
ASSERT(func.HasParent());
for (int i = 0; i < context_scope.num_variables(); i++) {
if (context_scope.IsInvisibleAt(i)) {
continue;
}
String& name = String::Handle(context_scope.NameAt(i));
ASSERT(!LocalVariable::IsFilteredIdentifier(name));
LocalVarDescriptorsBuilder::VarDesc desc;
desc.name = &name;
desc.info.set_kind(UntaggedLocalVarDescriptors::kContextVar);
desc.info.scope_id = context_scope.ContextLevelAt(i);
desc.info.declaration_pos = context_scope.DeclarationTokenIndexAt(i);
desc.info.begin_pos = begin_token_pos();
desc.info.end_pos = end_token_pos();
ASSERT((desc.info.begin_pos.IsReal() != desc.info.end_pos.IsReal()) ||
(desc.info.begin_pos <= desc.info.end_pos));
desc.info.set_index(context_scope.ContextIndexAt(i));
vars.Add(desc);
}
}
// Now collect all variables from local scopes.
int16_t scope_id = 0;
CollectLocalVariables(&vars, &scope_id);
return vars.Done();
}
// Add visible variables that are declared in this scope to vars, then
// collect visible variables of children, followed by siblings.
void LocalScope::CollectLocalVariables(LocalVarDescriptorsBuilder* vars,
int16_t* scope_id) {
(*scope_id)++;
for (int i = 0; i < this->variables_.length(); i++) {
LocalVariable* var = variables_[i];
if (var->owner() == this) {
if (var->name().ptr() == Symbols::CurrentContextVar().ptr()) {
// This is the local variable in which the function saves its
// own context before calling a closure function.
LocalVarDescriptorsBuilder::VarDesc desc;
desc.name = &var->name();
desc.info.set_kind(UntaggedLocalVarDescriptors::kSavedCurrentContext);
desc.info.scope_id = 0;
desc.info.declaration_pos = TokenPosition::kMinSource;
desc.info.begin_pos = TokenPosition::kMinSource;
desc.info.end_pos = TokenPosition::kMinSource;
desc.info.set_index(var->index().value());
vars->Add(desc);
} else if (!var->is_invisible()) {
ASSERT(!LocalVariable::IsFilteredIdentifier(var->name()));
// This is a regular Dart variable, either stack-based or captured.
LocalVarDescriptorsBuilder::VarDesc desc;
desc.name = &var->name();
if (var->is_captured()) {
desc.info.set_kind(UntaggedLocalVarDescriptors::kContextVar);
ASSERT(var->owner() != nullptr);
ASSERT(var->owner()->context_level() >= 0);
desc.info.scope_id = var->owner()->context_level();
} else {
desc.info.set_kind(UntaggedLocalVarDescriptors::kStackVar);
desc.info.scope_id = *scope_id;
}
desc.info.set_index(var->index().value());
desc.info.declaration_pos = var->declaration_token_pos();
desc.info.begin_pos = var->token_pos();
desc.info.end_pos = var->owner()->end_token_pos();
vars->Add(desc);
}
}
}
LocalScope* child = this->child();
while (child != nullptr) {
child->CollectLocalVariables(vars, scope_id);
child = child->sibling();
}
}
LocalVariable* LocalScope::LocalLookupVariable(const String& name,
intptr_t kernel_offset) const {
ASSERT(name.IsSymbol());
for (intptr_t i = 0; i < variables_.length(); i++) {
LocalVariable* var = variables_[i];
ASSERT(var->name().IsSymbol());
if ((var->name().ptr() == name.ptr()) &&
(var->kernel_offset() == kernel_offset)) {
return var;
}
}
return nullptr;
}
LocalVariable* LocalScope::LookupVariable(const String& name,
intptr_t kernel_offset,
bool test_only) {
LocalScope* current_scope = this;
while (current_scope != nullptr) {
LocalVariable* var =
current_scope->LocalLookupVariable(name, kernel_offset);
// If testing only, return the variable even if invisible.
if ((var != nullptr) && (!var->is_invisible() || test_only)) {
if (!test_only && (var->owner()->function_level() != function_level())) {
CaptureVariable(var);
}
return var;
}
current_scope = current_scope->parent();
}
return nullptr;
}
LocalVariable* LocalScope::LookupVariableByName(const String& name) {
ASSERT(name.IsSymbol());
for (LocalScope* scope = this; scope != nullptr; scope = scope->parent()) {
for (intptr_t i = 0, n = scope->variables_.length(); i < n; ++i) {
LocalVariable* var = scope->variables_[i];
ASSERT(var->name().IsSymbol());
if (var->name().ptr() == name.ptr()) {
return var;
}
}
}
return nullptr;
}
void LocalScope::CaptureVariable(LocalVariable* variable) {
ASSERT(variable != nullptr);
// The variable must exist in an enclosing scope, not necessarily in this one.
variable->set_is_captured();
const int variable_function_level = variable->owner()->function_level();
LocalScope* scope = this;
while (scope->function_level() != variable_function_level) {
// Insert an alias of the variable in the top scope of each function
// level so that the variable is found in the context.
LocalScope* parent_scope = scope->parent();
while ((parent_scope != nullptr) &&
(parent_scope->function_level() == scope->function_level())) {
scope = parent_scope;
parent_scope = scope->parent();
}
// An alias may already have been added in this scope, and in that case,
// in parent scopes as needed. If so, we are done.
if (!scope->AddVariable(variable)) {
return;
}
ASSERT(variable->owner() != scope); // Item is an alias.
scope = parent_scope;
}
}
int LocalScope::NumCapturedVariables() const {
// It is not necessary to traverse parent scopes, since we are only interested
// in the captured variables referenced in this scope. If this scope is the
// top scope at function level 1 and it (or its children scopes) references a
// captured variable declared in a parent scope at function level 0, it will
// contain an alias for that variable.
// Since code generation for nested functions is postponed until first
// invocation, the function level of the closure scope can only be 1.
ASSERT(function_level() == 1);
int num_captured = 0;
for (int i = 0; i < num_variables(); i++) {
LocalVariable* variable = VariableAt(i);
// Count the aliases of captured variables belonging to outer scopes.
if (variable->owner()->function_level() != 1) {
ASSERT(variable->is_captured());
ASSERT(variable->owner()->function_level() == 0);
num_captured++;
}
}
return num_captured;
}
ContextScopePtr LocalScope::PreserveOuterScope(
const Function& function,
intptr_t current_context_level) const {
Zone* zone = Thread::Current()->zone();
auto& library = Library::Handle(
zone, function.IsNull()
? Library::null()
: Class::Handle(zone, function.Owner()).library());
// Since code generation for nested functions is postponed until first
// invocation, the function level of the closure scope can only be 1.
ASSERT(function_level() == 1);
// Count the number of referenced captured variables.
intptr_t num_captured_vars = NumCapturedVariables();
// Create a ContextScope with space for num_captured_vars descriptors.
const ContextScope& context_scope =
ContextScope::Handle(ContextScope::New(num_captured_vars, false));
LocalVariable* awaiter_link = nullptr;
// Create a descriptor for each referenced captured variable of enclosing
// functions to preserve its name and its context allocation information.
int captured_idx = 0;
for (int i = 0; i < num_variables(); i++) {
LocalVariable* variable = VariableAt(i);
// Preserve the aliases of captured variables belonging to outer scopes.
if (variable->owner()->function_level() != 1) {
context_scope.SetTokenIndexAt(captured_idx, variable->token_pos());
context_scope.SetDeclarationTokenIndexAt(
captured_idx, variable->declaration_token_pos());
context_scope.SetNameAt(captured_idx, variable->name());
context_scope.ClearFlagsAt(captured_idx);
context_scope.SetIsFinalAt(captured_idx, variable->is_final());
context_scope.SetIsLateAt(captured_idx, variable->is_late());
if (variable->is_late()) {
context_scope.SetLateInitOffsetAt(captured_idx,
variable->late_init_offset());
}
context_scope.SetIsConstAt(captured_idx, variable->IsConst());
if (variable->IsConst()) {
context_scope.SetConstValueAt(captured_idx, *variable->ConstValue());
} else {
context_scope.SetTypeAt(captured_idx, variable->type());
}
context_scope.SetIsInvisibleAt(captured_idx, variable->is_invisible());
context_scope.SetContextIndexAt(captured_idx, variable->index().value());
// Adjust the context level relative to the current context level,
// since the context of the current scope will be at level 0 when
// compiling the nested function.
intptr_t adjusted_context_level =
variable->owner()->context_level() - current_context_level;
context_scope.SetContextLevelAt(captured_idx, adjusted_context_level);
context_scope.SetKernelOffsetAt(captured_idx, variable->kernel_offset());
// Handle async frame link.
const bool is_awaiter_link = variable->ComputeIfIsAwaiterLink(library);
context_scope.SetIsAwaiterLinkAt(captured_idx, is_awaiter_link);
if (is_awaiter_link) {
awaiter_link = variable;
}
captured_idx++;
}
}
ASSERT(context_scope.num_variables() == captured_idx); // Verify count.
if (awaiter_link != nullptr) {
const intptr_t depth =
current_context_level - awaiter_link->owner()->context_level();
const intptr_t index = awaiter_link->index().value();
if (Utils::IsUint(8, depth) && Utils::IsUint(8, index)) {
function.set_awaiter_link(
{static_cast<uint8_t>(depth), static_cast<uint8_t>(index)});
} else if (FLAG_precompiled_mode) {
OS::PrintErr(
"Warning: @pragma('vm:awaiter-link') marked variable %s is visible "
"from the function %s but the link {%" Pd ", %" Pd
"} can't be encoded\n",
awaiter_link->name().ToCString(),
function.IsNull() ? "<?>" : function.ToFullyQualifiedCString(), depth,
index);
}
}
return context_scope.ptr();
}
LocalScope* LocalScope::RestoreOuterScope(const ContextScope& context_scope) {
// The function level of the outer scope is one less than the function level
// of the current function, which is 0.
LocalScope* outer_scope = new LocalScope(nullptr, -1, 0);
// Add all variables as aliases to the outer scope.
for (int i = 0; i < context_scope.num_variables(); i++) {
LocalVariable* variable;
if (context_scope.IsConstAt(i)) {
variable = new LocalVariable(context_scope.DeclarationTokenIndexAt(i),
context_scope.TokenIndexAt(i),
String::ZoneHandle(context_scope.NameAt(i)),
Object::dynamic_type(),
context_scope.KernelOffsetAt(i));
variable->SetConstValue(
Instance::ZoneHandle(context_scope.ConstValueAt(i)));
} else {
variable =
new LocalVariable(context_scope.DeclarationTokenIndexAt(i),
context_scope.TokenIndexAt(i),
String::ZoneHandle(context_scope.NameAt(i)),
AbstractType::ZoneHandle(context_scope.TypeAt(i)),
context_scope.KernelOffsetAt(i));
}
variable->set_is_awaiter_link(context_scope.IsAwaiterLinkAt(i));
variable->set_is_captured();
variable->set_index(VariableIndex(context_scope.ContextIndexAt(i)));
if (context_scope.IsFinalAt(i)) {
variable->set_is_final();
}
if (context_scope.IsLateAt(i)) {
variable->set_is_late();
variable->set_late_init_offset(context_scope.LateInitOffsetAt(i));
}
if (context_scope.IsInvisibleAt(i)) {
variable->set_invisible(true);
}
// Create a fake owner scope describing the index and context level of the
// variable. Function level and loop level are unused (set to 0), since
// context level has already been assigned.
LocalScope* owner_scope = new LocalScope(nullptr, 0, 0);
owner_scope->set_context_level(context_scope.ContextLevelAt(i));
owner_scope->AddVariable(variable);
outer_scope->AddVariable(variable); // As alias.
ASSERT(variable->owner() == owner_scope);
}
return outer_scope;
}
void LocalScope::CaptureLocalVariables(LocalScope* top_scope) {
ASSERT(top_scope->function_level() == function_level());
LocalScope* scope = this;
while (scope != top_scope->parent()) {
for (intptr_t i = 0; i < scope->num_variables(); i++) {
LocalVariable* variable = scope->VariableAt(i);
if (variable->is_forced_stack() ||
(variable->name().ptr() == Symbols::ExceptionVar().ptr()) ||
(variable->name().ptr() == Symbols::SavedTryContextVar().ptr()) ||
(variable->name().ptr() == Symbols::ArgDescVar().ptr()) ||
(variable->name().ptr() ==
Symbols::FunctionTypeArgumentsVar().ptr())) {
// Don't capture those variables because the VM expects them to be on
// the stack.
continue;
}
scope->CaptureVariable(variable);
}
scope = scope->parent();
}
}
ContextScopePtr LocalScope::CreateImplicitClosureScope(const Function& func) {
const intptr_t kNumCapturedVars = 1;
// Create a ContextScope with space for kNumCapturedVars descriptors.
const ContextScope& context_scope =
ContextScope::Handle(ContextScope::New(kNumCapturedVars, true));
// Create a descriptor for 'this' variable.
context_scope.SetTokenIndexAt(0, func.token_pos());
context_scope.SetDeclarationTokenIndexAt(0, func.token_pos());
context_scope.SetNameAt(0, Symbols::This());
context_scope.ClearFlagsAt(0);
context_scope.SetIsFinalAt(0, true);
context_scope.SetIsConstAt(0, false);
const AbstractType& type = AbstractType::Handle(func.ParameterTypeAt(0));
context_scope.SetTypeAt(0, type);
context_scope.SetContextIndexAt(0, 0);
context_scope.SetContextLevelAt(0, 0);
context_scope.SetKernelOffsetAt(0, LocalVariable::kNoKernelOffset);
ASSERT(context_scope.num_variables() == kNumCapturedVars); // Verify count.
return context_scope.ptr();
}
bool LocalVariable::ComputeIfIsAwaiterLink(const Library& library) {
if (is_awaiter_link_ == IsAwaiterLink::kUnknown) {
RELEASE_ASSERT(annotations_offset_ != kNoKernelOffset);
Thread* T = Thread::Current();
Zone* Z = T->zone();
const auto& metadata = Object::Handle(
Z, kernel::EvaluateMetadata(library, annotations_offset_,
/* is_annotations_offset = */ true));
set_is_awaiter_link(
FindPragmaInMetadata(T, metadata, Symbols::vm_awaiter_link()));
}
return is_awaiter_link_ == IsAwaiterLink::kLink;
}
bool LocalVariable::Equals(const LocalVariable& other) const {
if (HasIndex() && other.HasIndex() && (index() == other.index())) {
if (is_captured() == other.is_captured()) {
if (!is_captured()) {
return true;
}
if (owner()->context_level() == other.owner()->context_level()) {
return true;
}
}
}
return false;
}
void LocalVarDescriptorsBuilder::AddAll(Zone* zone,
const LocalVarDescriptors& var_descs) {
for (intptr_t i = 0, n = var_descs.Length(); i < n; ++i) {
VarDesc desc;
desc.name = &String::Handle(zone, var_descs.GetName(i));
var_descs.GetInfo(i, &desc.info);
Add(desc);
}
}
void LocalVarDescriptorsBuilder::AddDeoptIdToContextLevelMappings(
ZoneGrowableArray<intptr_t>* context_level_array) {
// Record deopt-id -> context-level mappings, using ranges of deopt-ids with
// the same context-level. [context_level_array] contains (deopt_id,
// context_level) tuples.
for (intptr_t start = 0; start < context_level_array->length();) {
intptr_t start_deopt_id = (*context_level_array)[start];
intptr_t start_context_level = (*context_level_array)[start + 1];
intptr_t end = start;
intptr_t end_deopt_id = start_deopt_id;
for (intptr_t peek = start + 2; peek < context_level_array->length();
peek += 2) {
intptr_t peek_deopt_id = (*context_level_array)[peek];
intptr_t peek_context_level = (*context_level_array)[peek + 1];
// The range encoding assumes the tuples have ascending deopt_ids.
ASSERT(peek_deopt_id > end_deopt_id);
if (peek_context_level != start_context_level) break;
end = peek;
end_deopt_id = peek_deopt_id;
}
VarDesc desc;
desc.name = &Symbols::Empty(); // No name.
desc.info.set_kind(UntaggedLocalVarDescriptors::kContextLevel);
desc.info.scope_id = 0;
// We repurpose the token position fields to store deopt IDs in this case.
desc.info.begin_pos = TokenPosition::Deserialize(start_deopt_id);
desc.info.end_pos = TokenPosition::Deserialize(end_deopt_id);
desc.info.set_index(start_context_level);
Add(desc);
start = end + 2;
}
}
LocalVarDescriptorsPtr LocalVarDescriptorsBuilder::Done() {
if (vars_.is_empty()) {
return Object::empty_var_descriptors().ptr();
}
const LocalVarDescriptors& var_desc =
LocalVarDescriptors::Handle(LocalVarDescriptors::New(vars_.length()));
for (int i = 0; i < vars_.length(); i++) {
var_desc.SetVar(i, *(vars_[i].name), &vars_[i].info);
}
return var_desc.ptr();
}
} // namespace dart
#endif // !defined(DART_PRECOMPILED_RUNTIME)