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

src/compiler/ast-graph-builder.cc

Index: src/compiler/ast-graph-builder.cc
diff --git a/src/compiler/ast-graph-builder.cc b/src/compiler/ast-graph-builder.cc
index 9e8b951b04f36eb0bf1fbe981f92661f8ecaead0..1943f74a7c176ea95b50f815b859d825c5f52003 100644
--- a/src/compiler/ast-graph-builder.cc
+++ b/src/compiler/ast-graph-builder.cc
@@ -26,7 +26,7 @@ AstGraphBuilder::AstGraphBuilder(Zone* local_zone, CompilationInfo* info,
       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);
@@ -63,9 +63,11 @@ bool AstGraphBuilder::CreateGraph() {
   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()) {
@@ -123,8 +125,7 @@ bool AstGraphBuilder::CreateGraph() {
   }
 
   // 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());
@@ -291,25 +292,183 @@ Node* AstGraphBuilder::AstTestContext::ConsumeValue() {
 }
 
 
-AstGraphBuilder::BreakableScope* AstGraphBuilder::BreakableScope::FindBreakable(
-    BreakableStatement* target) {
-  BreakableScope* current = this;
-  while (current != NULL && current->target_ != target) {
-    owner_->environment()->Drop(current->drop_extra_);
+// 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;
+  }
+
+  // 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()->IntPtrConstant(deferred_.size());
+  }
+  Node* NewPathTokenForImplicitFallThrough() {
+    return owner_->jsgraph()->IntPtrConstant(-1);
+  }
+  Node* NewPathDispatchCondition(Node* t1, Node* t2) {
+    return owner_->NewNode(owner_->javascript()->StrictEqual(), t1, t2);

[titzer, 2015/02/02 09:47:29]

I think you want pointer/integer equality here. JS operators are for expressing
source program computations, not internal computations.

[Michael Starzinger, 2015/02/02 14:47:41]

Done.

[Michael Starzinger, 2015/02/02 17:08:41]

Yeah, well, ain't gonna happen as long as our Phi's have a machine
representation and are all marked as tagged. I left a TODO and verified, we
correctly lower to Word32Equal in the pipeline, so the code at the end should be
"optimal" already.

+  }
+
+ 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:
+      owner()->BuildThrow(value);
+      return true;
+    case CMD_RETURN:
+      owner()->BuildReturn(value);
+      return true;
+    case CMD_BREAK:
+    case CMD_CONTINUE:
+      break;
+  }
+  return false;
+}
+
+
+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;
+}
+
+
+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->drop_extra());
     current = current->next_;
   }
-  DCHECK(current != NULL);  // Always found (unless stack is malformed).
-  return current;
+  // TODO(mstarzinger): Unconditionally kill environment once throw is control.
+  if (command != CMD_THROW) owner()->set_environment(env);
+  DCHECK(current != NULL);  // Always handled (unless stack is malformed).
 }
 
 
-void AstGraphBuilder::BreakableScope::BreakTarget(BreakableStatement* stmt) {
-  FindBreakable(stmt)->control_->Break();
+void AstGraphBuilder::ControlScope::BreakTarget(BreakableStatement* stmt) {
+  PerformCommand(CMD_BREAK, stmt, nullptr);
 }
 
 
-void AstGraphBuilder::BreakableScope::ContinueTarget(BreakableStatement* stmt) {
-  FindBreakable(stmt)->control_->Continue();
+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);
 }
 
 
@@ -472,7 +631,7 @@ 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.
@@ -517,24 +676,19 @@ void AstGraphBuilder::VisitIfStatement(IfStatement* stmt) {
 
 
 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);
 }
 
 
@@ -552,7 +706,7 @@ void AstGraphBuilder::VisitWithStatement(WithStatement* stmt) {
 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;
 
@@ -805,14 +959,70 @@ void AstGraphBuilder::VisitForOfStatement(ForOfStatement* stmt) {
 
 
 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();
 }
 
 
@@ -1376,10 +1586,8 @@ void AstGraphBuilder::VisitYield(Yield* expr) {
 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);
+  execution_control()->ThrowValue(exception);
+  ast_context()->ProduceValue(exception);
 }
 
 
@@ -1822,7 +2030,7 @@ void AstGraphBuilder::VisitIfNotNull(Statement* stmt) {
 
 void AstGraphBuilder::VisitIterationBody(IterationStatement* stmt,
                                          LoopBuilder* loop, int drop_extra) {
-  BreakableScope scope(this, stmt, loop, drop_extra);
+  ControlScopeForIteration scope(this, stmt, loop, drop_extra);
   Visit(stmt->body());
 }
 
@@ -2349,6 +2557,23 @@ Node* AstGraphBuilder::BuildThrowConstAssignError(BailoutId bailout_id) {
 }
 
 
+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.

[Michael Starzinger, 2015/01/30 14:30:27]

This is the TODO I still need to address.

[Michael Starzinger, 2015/02/02 15:08:02]

I added a workaround that only uses the ControlScope to throw when
--turbo-exceptions is passed. This way I can solve the bailout-id separately,
because this one needs more thought than just threading through the ID.

+  // 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) {