Simplify handling of exits from with and catch.

src/full-codegen.cc

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 72 matching lines @@
 void BreakableStatementChecker::VisitBreakStatement(BreakStatement* stmt) {
 }
 
 
 void BreakableStatementChecker::VisitReturnStatement(ReturnStatement* stmt) {
   // Return is breakable if the expression is.
   Visit(stmt->expression());
 }
 
 
-void BreakableStatementChecker::VisitEnterWithContextStatement(
-    EnterWithContextStatement* stmt) {
+void BreakableStatementChecker::VisitWithStatement(WithStatement* stmt) {
   Visit(stmt->expression());

[Kevin Millikin (Chromium), 2011/08/11 10:37:18]

I'm not sure this is right, I'll check with Soeren.

 }
 
 
 void BreakableStatementChecker::VisitExitContextStatement(
     ExitContextStatement* stmt) {
 }
 
 
 void BreakableStatementChecker::VisitSwitchStatement(SwitchStatement* stmt) {
   // Switch statements breakable if the tag expression is.
@@ skipping 787 matching lines @@
   __ bind(&done);
   PrepareForBailoutForId(stmt->IfId(), NO_REGISTERS);
 }
 
 
 void FullCodeGenerator::VisitContinueStatement(ContinueStatement* stmt) {
   Comment cmnt(masm_,  "[ ContinueStatement");
   SetStatementPosition(stmt);
   NestedStatement* current = nesting_stack_;
   int stack_depth = 0;
+  int context_length = 0;
   // When continuing, we clobber the unpredictable value in the accumulator
   // with one that's safe for GC.  If we hit an exit from the try block of
   // try...finally on our way out, we will unconditionally preserve the
   // accumulator on the stack.
   ClearAccumulator();
   while (!current->IsContinueTarget(stmt->target())) {
-    stack_depth = current->Exit(stack_depth);
-    current = current->outer();
+    current = current->Exit(&stack_depth, &context_length);
   }
   __ Drop(stack_depth);
+  while (context_length > 0) {
+    LoadContextField(context_register(), Context::PREVIOUS_INDEX);
+    --context_length;
+  }
 
   Iteration* loop = current->AsIteration();
   __ jmp(loop->continue_target());
 }
 
 
 void FullCodeGenerator::VisitBreakStatement(BreakStatement* stmt) {
   Comment cmnt(masm_,  "[ BreakStatement");
   SetStatementPosition(stmt);
   NestedStatement* current = nesting_stack_;
   int stack_depth = 0;
+  int context_length = 0;
   // When breaking, we clobber the unpredictable value in the accumulator
   // with one that's safe for GC.  If we hit an exit from the try block of
   // try...finally on our way out, we will unconditionally preserve the
   // accumulator on the stack.
   ClearAccumulator();
   while (!current->IsBreakTarget(stmt->target())) {
-    stack_depth = current->Exit(stack_depth);
-    current = current->outer();
+    current = current->Exit(&stack_depth, &context_length);
   }
   __ Drop(stack_depth);
+  while (context_length > 0) {
+    LoadContextField(context_register(), Context::PREVIOUS_INDEX);
+    --context_length;
+  }

[Vyacheslav Egorov (Chromium), 2011/08/11 11:21:55]

Break should also patch context in the stack slot:

-------------------
var o = { x: function () { }, y: function () { print("bazinga!"); } };

function foo() {
  while (true) {
    with (o) {
      x();
      break;
    }
  }
  baz(); // esi fill be restored from stack after the call
  with ({}) y(); // bazinga
}

function baz() {}

foo();
-------------------

(add this test to mjsunit).

[Kevin Millikin (Chromium), 2011/08/11 11:30:50]

Oops, yes.  Good catch.

 
   Breakable* target = current->AsBreakable();
   __ jmp(target->break_target());
 }
 
 
 void FullCodeGenerator::VisitReturnStatement(ReturnStatement* stmt) {
   Comment cmnt(masm_, "[ ReturnStatement");
   SetStatementPosition(stmt);
   Expression* expr = stmt->expression();
   VisitForAccumulatorValue(expr);
 
   // Exit all nested statements.
   NestedStatement* current = nesting_stack_;
   int stack_depth = 0;
+  int context_length = 0;
   while (current != NULL) {
-    stack_depth = current->Exit(stack_depth);
-    current = current->outer();
+    current = current->Exit(&stack_depth, &context_length);
   }
   __ Drop(stack_depth);
 
   EmitReturnSequence();
 }
 
 
-void FullCodeGenerator::VisitEnterWithContextStatement(
-    EnterWithContextStatement* stmt) {
-  Comment cmnt(masm_, "[ EnterWithContextStatement");
+void FullCodeGenerator::VisitWithStatement(WithStatement* stmt) {
+  Comment cmnt(masm_, "[ WithStatement");
   SetStatementPosition(stmt);
 
   VisitForStackValue(stmt->expression());
   PushFunctionArgumentForContextAllocation();
   __ CallRuntime(Runtime::kPushWithContext, 2);
   decrement_stack_height();
   StoreToFrameField(StandardFrameConstants::kContextOffset, context_register());
+
+  { WithOrCatch body(this);
+    Visit(stmt->statement());
+  }
+
+  // Pop context.
+  LoadContextField(context_register(), Context::PREVIOUS_INDEX);
+  // Update local stack frame context field.
+  StoreToFrameField(StandardFrameConstants::kContextOffset, context_register());
 }
 
 
 void FullCodeGenerator::VisitExitContextStatement(ExitContextStatement* stmt) {
   Comment cmnt(masm_, "[ ExitContextStatement");
   SetStatementPosition(stmt);
 
   // Pop context.
   LoadContextField(context_register(), Context::PREVIOUS_INDEX);
   // Update local stack frame context field.
@@ skipping 138 matching lines @@
     __ push(result_register());
     PushFunctionArgumentForContextAllocation();
     __ CallRuntime(Runtime::kPushCatchContext, 3);
     StoreToFrameField(StandardFrameConstants::kContextOffset,
                       context_register());
   }
 
   Scope* saved_scope = scope();
   scope_ = stmt->scope();
   ASSERT(scope_->declarations()->is_empty());
-  Visit(stmt->catch_block());
+  { WithOrCatch body(this);
+    Visit(stmt->catch_block());
+  }
   scope_ = saved_scope;
   __ jmp(&done);
 
   // Try block code. Sets up the exception handler chain.
   __ bind(&try_handler_setup);
   {
     TryCatch try_block(this, &catch_entry);
     __ PushTryHandler(IN_JAVASCRIPT, TRY_CATCH_HANDLER);
     increment_stack_height(StackHandlerConstants::kSize / kPointerSize);
     Visit(stmt->try_block());
@@ skipping 25 matching lines @@
   //
   // The finally block must assume a return address on top of the stack
   // (or in the link register on ARM chips) and a value (return value or
   // exception) in the result register (rax/eax/r0), both of which must
   // be preserved. The return address isn't GC-safe, so it should be
   // cooked before GC.
   Label finally_entry;
   Label try_handler_setup;
   const int original_stack_height = stack_height();
   const int finally_block_stack_height = original_stack_height + 2;
-  const int try_block_stack_height = original_stack_height + 4;
-  STATIC_ASSERT(StackHandlerConstants::kSize / kPointerSize == 4);
+  const int try_block_stack_height = original_stack_height + 5;
+  STATIC_ASSERT(StackHandlerConstants::kSize == 5 * kPointerSize);
 
   // Setup the try-handler chain. Use a call to
   // Jump to try-handler setup and try-block code. Use call to put try-handler
   // address on stack.
   __ Call(&try_handler_setup);
   // Try handler code. Return address of call is pushed on handler stack.
   {
     // This code is only executed during stack-handler traversal when an
     // exception is thrown. The execption is in the result register, which
     // is retained by the finally block.
@@ skipping 108 matching lines @@
   Comment cmnt(masm_, "[ Throw");
   // Throw has no effect on the stack height or the current expression context.
   // Usually the expression context is null, because throw is a statement.
   VisitForStackValue(expr->exception());
   __ CallRuntime(Runtime::kThrow, 1);
   decrement_stack_height();
   // Never returns here.
 }
 
 
-int FullCodeGenerator::TryFinally::Exit(int stack_depth) {
+FullCodeGenerator::NestedStatement* FullCodeGenerator::TryFinally::Exit(
+    int* stack_depth,
+    int* context_length) {
   // The macros used here must preserve the result register.
-  __ Drop(stack_depth);
+  __ Drop(*stack_depth);
   __ PopTryHandler();
+  *stack_depth = 0;
+
+  Register context = FullCodeGenerator::context_register();
+  while (*context_length > 0) {
+    codegen_->LoadContextField(context, Context::PREVIOUS_INDEX);
+    --(*context_length);
+  }
+
   __ Call(finally_entry_);
-  return 0;
+  return previous_;
 }
 
 
-int FullCodeGenerator::TryCatch::Exit(int stack_depth) {
+FullCodeGenerator::NestedStatement* FullCodeGenerator::TryCatch::Exit(
+    int* stack_depth,
+    int* context_length) {
   // The macros used here must preserve the result register.
-  __ Drop(stack_depth);
+  __ Drop(*stack_depth);
   __ PopTryHandler();
-  return 0;
+  *stack_depth = 0;
+  return previous_;
 }
 
 
 bool FullCodeGenerator::TryLiteralCompare(CompareOperation* compare,
                                           Label* if_true,
                                           Label* if_false,
                                           Label* fall_through) {
   Expression *expr;
   Handle<String> check;
   if (compare->IsLiteralCompareTypeof(&expr, &check)) {
     EmitLiteralCompareTypeof(expr, check, if_true, if_false, fall_through);
     return true;
   }
 
   if (compare->IsLiteralCompareUndefined(&expr)) {
     EmitLiteralCompareUndefined(expr, if_true, if_false, fall_through);
     return true;
   }
 
   return false;
 }
 
 
 #undef __
 
 
 } }  // namespace v8::internal