First stab at try-catch and try-finally in TurboFan.

src/compiler/ast-graph-builder.cc

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/compiler/ast-graph-builder.h"
 
 #include "src/compiler.h"
 #include "src/compiler/ast-loop-assignment-analyzer.h"
 #include "src/compiler/control-builders.h"
 #include "src/compiler/machine-operator.h"
 #include "src/compiler/node-matchers.h"
 #include "src/compiler/node-properties.h"
 #include "src/compiler/operator-properties.h"
 #include "src/full-codegen.h"
 #include "src/parser.h"
 #include "src/scopes.h"
 
 namespace v8 {
 namespace internal {
 namespace compiler {
 
 AstGraphBuilder::AstGraphBuilder(Zone* local_zone, CompilationInfo* info,
                                  JSGraph* jsgraph, LoopAssignmentAnalysis* loop)
     : StructuredGraphBuilder(jsgraph->isolate(), local_zone, jsgraph->graph(),
                              jsgraph->common()),
       info_(info),
       jsgraph_(jsgraph),
       globals_(0, local_zone),
-      breakable_(NULL),
+      execution_control_(NULL),
       execution_context_(NULL),
       loop_assignment_analysis_(loop) {
   InitializeAstVisitor(info->isolate(), local_zone);
 }
 
 
 Node* AstGraphBuilder::GetFunctionClosure() {
   if (!function_closure_.is_set()) {
     // Parameter -1 is special for the function closure
     const Operator* op = common()->Parameter(-1);
@@ skipping 16 matching lines @@
 
 
 bool AstGraphBuilder::CreateGraph() {
   Scope* scope = info()->scope();
   DCHECK(graph() != NULL);
 
   // Set up the basic structure of the graph.
   int parameter_count = info()->num_parameters();
   graph()->SetStart(graph()->NewNode(common()->Start(parameter_count)));
 
-  Node* start = graph()->start();
+  // Initialize control scope.
+  ControlScope control(this, 0);
+
   // Initialize the top-level environment.
-  Environment env(this, scope, start);
+  Environment env(this, scope, graph()->start());
   set_environment(&env);
 
   if (info()->is_osr()) {
     // Use OSR normal entry as the start of the top-level environment.
     // It will be replaced with {Dead} after typing and optimizations.
     NewNode(common()->OsrNormalEntry());
   }
 
   // Initialize the incoming context.
   Node* outer_context = GetFunctionContext();
@@ skipping 37 matching lines @@
   if (HasStackOverflow()) return false;
 
   // Emit tracing call if requested to do so.
   if (FLAG_trace) {
     // TODO(mstarzinger): Only traces implicit return.
     Node* return_value = jsgraph()->UndefinedConstant();
     NewNode(javascript()->CallRuntime(Runtime::kTraceExit, 1), return_value);
   }
 
   // Return 'undefined' in case we can fall off the end.
-  Node* control = NewNode(common()->Return(), jsgraph()->UndefinedConstant());
-  UpdateControlDependencyToLeaveFunction(control);
+  BuildReturn(jsgraph()->UndefinedConstant());
 
   // Finish the basic structure of the graph.
   environment()->UpdateControlDependency(exit_control());
   graph()->SetEnd(NewNode(common()->End()));
 
   return true;
 }
 
 
 // Left-hand side can only be a property, a global or a variable slot.
@@ skipping 146 matching lines @@
 Node* AstGraphBuilder::AstValueContext::ConsumeValue() {
   return environment()->Pop();
 }
 
 
 Node* AstGraphBuilder::AstTestContext::ConsumeValue() {
   return environment()->Pop();
 }
 
 
-AstGraphBuilder::BreakableScope* AstGraphBuilder::BreakableScope::FindBreakable(
-    BreakableStatement* target) {
-  BreakableScope* current = this;
-  while (current != NULL && current->target_ != target) {
-    owner_->environment()->Drop(current->drop_extra_);
-    current = current->next_;
+// Helper class for a try-finally control scope. It can record intercepted
+// control-flow commands that cause entry into a finally-block, and re-apply
+// them after again leaving that block. Special tokens are used to identify
+// paths going through the finally-block to dispatch after leaving the block.
+class AstGraphBuilder::ControlScope::DeferredCommands : public ZoneObject {
+ public:
+  explicit DeferredCommands(AstGraphBuilder* owner)
+      : owner_(owner), deferred_(owner->zone()) {}
+
+  // One recorded control-flow command.
+  struct Entry {
+    Command command;       // The command type being applied on this path.
+    Statement* statement;  // The target statement for the command or {NULL}.
+    Node* value;           // The passed value node for the command or {NULL}.
+    Node* token;           // A token identifying this particular path.
+  };
+
+  // Records a control-flow command while entering the finally-block. This also
+  // generates a new dispatch token that identifies one particular path.
+  Node* RecordCommand(Command cmd, Statement* stmt, Node* value) {
+    Node* token = NewPathTokenForDeferredCommand();
+    deferred_.push_back({cmd, stmt, value, token});
+    return token;
   }
-  DCHECK(current != NULL);  // Always found (unless stack is malformed).
-  return current;
+
+  // Returns the dispatch token to be used to identify the implicit fall-through
+  // path at the end of a try-block into the corresponding finally-block.
+  Node* GetFallThroughToken() { return NewPathTokenForImplicitFallThrough(); }
+
+  // Applies all recorded control-flow commands after the finally-block again.
+  // This generates a dynamic dispatch on the token from the entry point.
+  void ApplyDeferredCommands(Node* token) {
+    SwitchBuilder dispatch(owner_, static_cast<int>(deferred_.size()));
+    dispatch.BeginSwitch();
+    for (size_t i = 0; i < deferred_.size(); ++i) {
+      Node* condition = NewPathDispatchCondition(token, deferred_[i].token);
+      dispatch.BeginLabel(static_cast<int>(i), condition);
+      dispatch.EndLabel();
+    }
+    for (size_t i = 0; i < deferred_.size(); ++i) {
+      dispatch.BeginCase(static_cast<int>(i));
+      owner_->execution_control()->PerformCommand(
+          deferred_[i].command, deferred_[i].statement, deferred_[i].value);
+      dispatch.EndCase();
+    }
+    dispatch.EndSwitch();
+  }
+
+ protected:
+  Node* NewPathTokenForDeferredCommand() {
+    return owner_->jsgraph()->Constant(static_cast<int>(deferred_.size()));
+  }
+  Node* NewPathTokenForImplicitFallThrough() {
+    return owner_->jsgraph()->Constant(-1);
+  }
+  Node* NewPathDispatchCondition(Node* t1, Node* t2) {
+    // TODO(mstarzinger): This should be machine()->WordEqual(), but our Phi
+    // nodes all have kRepTagged|kTypeAny, which causes representation mismatch.
+    return owner_->NewNode(owner_->javascript()->StrictEqual(), t1, t2);
+  }
+
+ private:
+  AstGraphBuilder* owner_;
+  ZoneVector<Entry> deferred_;
+};
+
+
+bool AstGraphBuilder::ControlScope::Execute(Command command, Statement* target,
+                                            Node* value) {
+  // For function-level control.
+  switch (command) {
+    case CMD_THROW:
+      builder()->BuildThrow(value);
+      return true;
+    case CMD_RETURN:
+      builder()->BuildReturn(value);
+      return true;
+    case CMD_BREAK:
+    case CMD_CONTINUE:
+      break;
+  }
+  return false;
 }
 
 
-void AstGraphBuilder::BreakableScope::BreakTarget(BreakableStatement* stmt) {
-  FindBreakable(stmt)->control_->Break();
+bool AstGraphBuilder::ControlScopeForBreakable::Execute(Command command,
+                                                        Statement* target,
+                                                        Node* value) {
+  if (target != target_) return false;  // We are not the command target.
+  switch (command) {
+    case CMD_BREAK:
+      control_->Break();
+      return true;
+    case CMD_CONTINUE:
+    case CMD_THROW:
+    case CMD_RETURN:
+      break;
+  }
+  return false;
 }
 
 
-void AstGraphBuilder::BreakableScope::ContinueTarget(BreakableStatement* stmt) {
-  FindBreakable(stmt)->control_->Continue();
+bool AstGraphBuilder::ControlScopeForIteration::Execute(Command command,
+                                                        Statement* target,
+                                                        Node* value) {
+  if (target != target_) return false;  // We are not the command target.
+  switch (command) {
+    case CMD_BREAK:
+      control_->Break();
+      return true;
+    case CMD_CONTINUE:
+      control_->Continue();
+      return true;
+    case CMD_THROW:
+    case CMD_RETURN:
+      break;
+  }
+  return false;
 }
 
 
+bool AstGraphBuilder::ControlScopeForCatch::Execute(Command command,
+                                                    Statement* target,
+                                                    Node* value) {
+  switch (command) {
+    case CMD_THROW:
+      control_->Throw(value);
+      return true;
+    case CMD_BREAK:
+    case CMD_CONTINUE:
+    case CMD_RETURN:
+      break;
+  }
+  return false;
+}
+
+
+bool AstGraphBuilder::ControlScopeForFinally::Execute(Command cmd,
+                                                      Statement* target,
+                                                      Node* value) {
+  Node* token = commands_->RecordCommand(cmd, target, value);
+  control_->LeaveTry(token);
+  return true;
+}
+
+
+void AstGraphBuilder::ControlScope::PerformCommand(Command command,
+                                                   Statement* target,
+                                                   Node* value) {
+  StructuredGraphBuilder::Environment* env = environment()->CopyAsUnreachable();
+  ControlScope* current = this;
+  while (current != NULL) {
+    if (current->Execute(command, target, value)) break;
+    environment()->Drop(current->stack_delta());
+    current = current->next_;
+  }
+  // TODO(mstarzinger): Unconditionally kill environment once throw is control.
+  if (command != CMD_THROW) builder()->set_environment(env);
+  DCHECK(current != NULL);  // Always handled (unless stack is malformed).
+}
+
+
+void AstGraphBuilder::ControlScope::BreakTarget(BreakableStatement* stmt) {

[titzer, 2015/02/03 09:01:22]

The names {BreakTarget} and {ContinueTarget} have always been a little confusing
to me. Maybe {BreakTo} and {ContinueTo} would be clearer? Then it would read:

execution_control()->ContinueTo(stmt->target())

[Michael Starzinger, 2015/02/03 09:18:53]

Done.

+  PerformCommand(CMD_BREAK, stmt, nullptr);
+}
+
+
+void AstGraphBuilder::ControlScope::ContinueTarget(BreakableStatement* stmt) {
+  PerformCommand(CMD_CONTINUE, stmt, nullptr);
+}
+
+
+void AstGraphBuilder::ControlScope::ReturnValue(Node* return_value) {
+  PerformCommand(CMD_RETURN, nullptr, return_value);
+}
+
+
+void AstGraphBuilder::ControlScope::ThrowValue(Node* exception_value) {
+  PerformCommand(CMD_THROW, nullptr, exception_value);
+}
+
+
 void AstGraphBuilder::VisitForValueOrNull(Expression* expr) {
   if (expr == NULL) {
     return environment()->Push(jsgraph()->NullConstant());
   }
   VisitForValue(expr);
 }
 
 
 void AstGraphBuilder::VisitForValueOrTheHole(Expression* expr) {
   if (expr == NULL) {
@@ skipping 139 matching lines @@
 
 
 void AstGraphBuilder::VisitModulePath(ModulePath* modl) { UNREACHABLE(); }
 
 
 void AstGraphBuilder::VisitModuleUrl(ModuleUrl* modl) { UNREACHABLE(); }
 
 
 void AstGraphBuilder::VisitBlock(Block* stmt) {
   BlockBuilder block(this);
-  BreakableScope scope(this, stmt, &block, 0);
+  ControlScopeForBreakable scope(this, stmt, &block);
   if (stmt->labels() != NULL) block.BeginBlock();
   if (stmt->scope() == NULL) {
     // Visit statements in the same scope, no declarations.
     VisitStatements(stmt->statements());
   } else {
     // Visit declarations and statements in a block scope.
     Node* context = BuildLocalBlockContext(stmt->scope());
     ContextScope scope(this, stmt->scope(), context);
     VisitDeclarations(stmt->scope()->declarations());
     VisitStatements(stmt->statements());
@@ skipping 24 matching lines @@
   compare_if.If(condition);
   compare_if.Then();
   Visit(stmt->then_statement());
   compare_if.Else();
   Visit(stmt->else_statement());
   compare_if.End();
 }
 
 
 void AstGraphBuilder::VisitContinueStatement(ContinueStatement* stmt) {
-  StructuredGraphBuilder::Environment* env = environment()->CopyAsUnreachable();
-  breakable()->ContinueTarget(stmt->target());
-  set_environment(env);
+  execution_control()->ContinueTarget(stmt->target());
 }
 
 
 void AstGraphBuilder::VisitBreakStatement(BreakStatement* stmt) {
-  StructuredGraphBuilder::Environment* env = environment()->CopyAsUnreachable();
-  breakable()->BreakTarget(stmt->target());
-  set_environment(env);
+  execution_control()->BreakTarget(stmt->target());
 }
 
 
 void AstGraphBuilder::VisitReturnStatement(ReturnStatement* stmt) {
   VisitForValue(stmt->expression());
   Node* result = environment()->Pop();
-  Node* control = NewNode(common()->Return(), result);
-  UpdateControlDependencyToLeaveFunction(control);
+  execution_control()->ReturnValue(result);
 }
 
 
 void AstGraphBuilder::VisitWithStatement(WithStatement* stmt) {
   VisitForValue(stmt->expression());
   Node* value = environment()->Pop();
   const Operator* op = javascript()->CreateWithContext();
   Node* context = NewNode(op, value, GetFunctionClosure());
   PrepareFrameState(context, stmt->EntryId());
   ContextScope scope(this, stmt->scope(), context);
   Visit(stmt->statement());
 }
 
 
 void AstGraphBuilder::VisitSwitchStatement(SwitchStatement* stmt) {
   ZoneList<CaseClause*>* clauses = stmt->cases();
   SwitchBuilder compare_switch(this, clauses->length());
-  BreakableScope scope(this, stmt, &compare_switch, 0);
+  ControlScopeForBreakable scope(this, stmt, &compare_switch);
   compare_switch.BeginSwitch();
   int default_index = -1;
 
   // Keep the switch value on the stack until a case matches.
   VisitForValue(stmt->tag());
   Node* tag = environment()->Top();
 
   // Iterate over all cases and create nodes for label comparison.
   for (int i = 0; i < clauses->length(); i++) {
     CaseClause* clause = clauses->at(i);
@@ skipping 232 matching lines @@
   Node* condition = environment()->Pop();
   for_loop.BreakWhen(condition);
   VisitForEffect(stmt->assign_each());
   VisitIterationBody(stmt, &for_loop, 0);
   for_loop.EndBody();
   for_loop.EndLoop();
 }
 
 
 void AstGraphBuilder::VisitTryCatchStatement(TryCatchStatement* stmt) {
-  // TODO(turbofan): Implement try-catch here.
-  SetStackOverflow();
+  TryCatchBuilder try_control(this);
+
+  // Evaluate the try-block inside a control scope. This simulates a handler
+  // that is intercepting 'throw' control commands.
+  try_control.BeginTry();
+  {
+    ControlScopeForCatch scope(this, &try_control);
+    Visit(stmt->try_block());
+  }
+  try_control.EndTry();
+
+  // Create a catch scope that binds the exception.
+  Node* exception = try_control.GetExceptionNode();
+  if (exception == NULL) exception = jsgraph()->NullConstant();
+  Unique<String> name = MakeUnique(stmt->variable()->name());
+  const Operator* op = javascript()->CreateCatchContext(name);
+  Node* context = NewNode(op, exception, GetFunctionClosure());
+  PrepareFrameState(context, BailoutId::None());
+  ContextScope scope(this, stmt->scope(), context);
+  DCHECK(stmt->scope()->declarations()->is_empty());
+
+  // Evaluate the catch-block.
+  Visit(stmt->catch_block());
+  try_control.EndCatch();
+
+  // TODO(mstarzinger): Remove bailout once everything works.
+  if (!FLAG_turbo_exceptions) SetStackOverflow();
 }
 
 
 void AstGraphBuilder::VisitTryFinallyStatement(TryFinallyStatement* stmt) {
-  // TODO(turbofan): Implement try-catch here.
-  SetStackOverflow();
+  TryFinallyBuilder try_control(this);
+
+  // We keep a record of all paths that enter the finally-block to be able to
+  // dispatch to the correct continuation point after the statements in the
+  // finally-block have been evaluated.
+  //
+  // The try-finally construct can enter the finally-block in three ways:
+  // 1. By exiting the try-block normally, falling through at the end.
+  // 2. By exiting the try-block with a function-local control flow transfer
+  //    (i.e. through break/continue/return statements).
+  // 3. By exiting the try-block with a thrown exception.
+  ControlScope::DeferredCommands* commands =
+      new (zone()) ControlScope::DeferredCommands(this);
+
+  // Evaluate the try-block inside a control scope. This simulates a handler
+  // that is intercepting all control commands.
+  try_control.BeginTry();
+  {
+    ControlScopeForFinally scope(this, commands, &try_control);
+    Visit(stmt->try_block());
+  }
+  try_control.EndTry(commands->GetFallThroughToken());
+
+  // Evaluate the finally-block.
+  Visit(stmt->finally_block());
+  try_control.EndFinally();
+
+  // Dynamic dispatch after the finally-block.
+  Node* token = try_control.GetDispatchTokenNode();
+  commands->ApplyDeferredCommands(token);
+
+  // TODO(mstarzinger): Remove bailout once everything works.
+  if (!FLAG_turbo_exceptions) SetStackOverflow();
 }
 
 
 void AstGraphBuilder::VisitDebuggerStatement(DebuggerStatement* stmt) {
   // TODO(turbofan): Do we really need a separate reloc-info for this?
   Node* node = NewNode(javascript()->CallRuntime(Runtime::kDebugBreak, 0));
   PrepareFrameState(node, stmt->DebugBreakId());
 }
 
 
@@ skipping 543 matching lines @@
 void AstGraphBuilder::VisitYield(Yield* expr) {
   // TODO(turbofan): Implement yield here.
   SetStackOverflow();
   ast_context()->ProduceValue(jsgraph()->UndefinedConstant());
 }
 
 
 void AstGraphBuilder::VisitThrow(Throw* expr) {
   VisitForValue(expr->exception());
   Node* exception = environment()->Pop();
-  const Operator* op = javascript()->CallRuntime(Runtime::kThrow, 1);
-  Node* value = NewNode(op, exception);
-  PrepareFrameState(value, expr->id(), ast_context()->GetStateCombine());
-  ast_context()->ProduceValue(value);
+  if (FLAG_turbo_exceptions) {
+    execution_control()->ThrowValue(exception);
+    ast_context()->ProduceValue(exception);
+  } else {
+    // TODO(mstarzinger): Temporary workaround for bailout-id for debugger.
+    const Operator* op = javascript()->CallRuntime(Runtime::kThrow, 1);
+    Node* value = NewNode(op, exception);
+    PrepareFrameState(value, expr->id(), ast_context()->GetStateCombine());
+    ast_context()->ProduceValue(value);
+  }
 }
 
 
 void AstGraphBuilder::VisitProperty(Property* expr) {
   Node* value;
   VectorSlotPair pair = CreateVectorSlotPair(expr->PropertyFeedbackSlot());
   if (expr->key()->IsPropertyName()) {
     VisitForValue(expr->obj());
     Node* object = environment()->Pop();
     Unique<Name> name = MakeUnique(expr->key()->AsLiteral()->AsPropertyName());
@@ skipping 421 matching lines @@
 }
 
 
 void AstGraphBuilder::VisitIfNotNull(Statement* stmt) {
   if (stmt == NULL) return;
   Visit(stmt);
 }
 
 
 void AstGraphBuilder::VisitIterationBody(IterationStatement* stmt,
-                                         LoopBuilder* loop, int drop_extra) {
-  BreakableScope scope(this, stmt, loop, drop_extra);
+                                         LoopBuilder* loop, int stack_delta) {
+  ControlScopeForIteration scope(this, stmt, loop, stack_delta);
   Visit(stmt->body());
 }
 
 
 void AstGraphBuilder::VisitDelete(UnaryOperation* expr) {
   Node* value;
   if (expr->expression()->IsVariableProxy()) {
     // Delete of an unqualified identifier is only allowed in classic mode but
     // deleting "this" is allowed in all language modes.
     Variable* variable = expr->expression()->AsVariableProxy()->var();
@@ skipping 506 matching lines @@
 Node* AstGraphBuilder::BuildThrowConstAssignError(BailoutId bailout_id) {
   // TODO(mstarzinger): Should be unified with the VisitThrow implementation.
   const Operator* op =
       javascript()->CallRuntime(Runtime::kThrowConstAssignError, 0);
   Node* call = NewNode(op);
   PrepareFrameState(call, bailout_id);
   return call;
 }
 
 
+Node* AstGraphBuilder::BuildReturn(Node* return_value) {
+  Node* control = NewNode(common()->Return(), return_value);
+  UpdateControlDependencyToLeaveFunction(control);
+  return control;
+}
+
+
+Node* AstGraphBuilder::BuildThrow(Node* exception_value) {
+  const Operator* op = javascript()->CallRuntime(Runtime::kThrow, 1);
+  Node* control = NewNode(op, exception_value);
+  // TODO(mstarzinger): Thread through the correct bailout id to this point.
+  // PrepareFrameState(value, expr->id(), ast_context()->GetStateCombine());
+  PrepareFrameState(control, BailoutId::None());
+  return control;
+}
+
+
 Node* AstGraphBuilder::BuildBinaryOp(Node* left, Node* right, Token::Value op) {
   const Operator* js_op;
   switch (op) {
     case Token::BIT_OR:
       js_op = javascript()->BitwiseOr();
       break;
     case Token::BIT_AND:
       js_op = javascript()->BitwiseAnd();
       break;
     case Token::BIT_XOR:
@@ skipping 67 matching lines @@
 
 BitVector* AstGraphBuilder::GetVariablesAssignedInLoop(
     IterationStatement* stmt) {
   if (loop_assignment_analysis_ == NULL) return NULL;
   return loop_assignment_analysis_->GetVariablesAssignedInLoop(stmt);
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8