[fullcodegen] Implement control flow across do-expressions.

src/full-codegen/full-codegen.cc

 // Copyright 2012 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/full-codegen/full-codegen.h"
 
 #include "src/ast/ast.h"
 #include "src/ast/ast-numbering.h"
 #include "src/ast/prettyprinter.h"
 #include "src/ast/scopeinfo.h"
@@ skipping 895 matching lines @@
     Visit(stmt->then_statement());
 
     PrepareForBailoutForId(stmt->ElseId(), NO_REGISTERS);
   }
   __ bind(&done);
   PrepareForBailoutForId(stmt->IfId(), NO_REGISTERS);
 }
 
 void FullCodeGenerator::EmitContinue(Statement* target) {
   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(target)) {
     if (current->IsTryFinally()) {
       Comment cmnt(masm(), "[ Deferred continue through finally");
-      current->Exit(&stack_depth, &context_length);
-      DCHECK_EQ(0, stack_depth);
-      DCHECK_EQ(0, context_length);
+      current->Exit(&context_length);
+      DCHECK_EQ(-1, context_length);
       current->AsTryFinally()->deferred_commands()->RecordContinue(target);
       return;
     }
-    current = current->Exit(&stack_depth, &context_length);
+    current = current->Exit(&context_length);
   }
-  __ Drop(stack_depth);
+  int stack_depth = current->GetStackDepthAtTarget();
+  int stack_drop = operand_stack_depth_ - stack_depth;
+  DCHECK_GE(stack_drop, 0);
+  __ Drop(stack_drop);
   if (context_length > 0) {
     while (context_length > 0) {
       LoadContextField(context_register(), Context::PREVIOUS_INDEX);
       --context_length;
     }
     StoreToFrameField(StandardFrameConstants::kContextOffset,
                       context_register());
   }
 
   __ jmp(current->AsIteration()->continue_label());
 }
 
 void FullCodeGenerator::VisitContinueStatement(ContinueStatement* stmt) {
   Comment cmnt(masm_, "[ ContinueStatement");
   SetStatementPosition(stmt);
   EmitContinue(stmt->target());
 }
 
 void FullCodeGenerator::EmitBreak(Statement* target) {
   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(target)) {
     if (current->IsTryFinally()) {
       Comment cmnt(masm(), "[ Deferred break through finally");
-      current->Exit(&stack_depth, &context_length);
-      DCHECK_EQ(0, stack_depth);
-      DCHECK_EQ(0, context_length);
+      current->Exit(&context_length);
+      DCHECK_EQ(-1, context_length);
       current->AsTryFinally()->deferred_commands()->RecordBreak(target);
       return;
     }
-    current = current->Exit(&stack_depth, &context_length);
+    current = current->Exit(&context_length);
   }
-  __ Drop(stack_depth);
+  int stack_depth = current->GetStackDepthAtTarget();
+  int stack_drop = operand_stack_depth_ - stack_depth;
+  DCHECK_GE(stack_drop, 0);
+  __ Drop(stack_drop);
   if (context_length > 0) {
     while (context_length > 0) {
       LoadContextField(context_register(), Context::PREVIOUS_INDEX);
       --context_length;
     }
     StoreToFrameField(StandardFrameConstants::kContextOffset,
                       context_register());
   }
 
   __ jmp(current->AsBreakable()->break_label());
 }
 
 void FullCodeGenerator::VisitBreakStatement(BreakStatement* stmt) {
   Comment cmnt(masm_, "[ BreakStatement");
   SetStatementPosition(stmt);
   EmitBreak(stmt->target());
 }
 
 void FullCodeGenerator::EmitUnwindAndReturn() {
   NestedStatement* current = nesting_stack_;
-  int stack_depth = 0;
   int context_length = 0;
   while (current != NULL) {
     if (current->IsTryFinally()) {
       Comment cmnt(masm(), "[ Deferred return through finally");
-      current->Exit(&stack_depth, &context_length);
-      DCHECK_EQ(0, stack_depth);
-      DCHECK_EQ(0, context_length);
+      current->Exit(&context_length);
+      DCHECK_EQ(-1, context_length);
       current->AsTryFinally()->deferred_commands()->RecordReturn();
       return;
     }
-    current = current->Exit(&stack_depth, &context_length);
+    current = current->Exit(&context_length);
   }
-  __ Drop(stack_depth);
   EmitReturnSequence();
 }
 
 void FullCodeGenerator::EmitNamedSuperPropertyLoad(Property* prop) {
   // Stack: receiver, home_object
   SetExpressionPosition(prop);
   Literal* key = prop->key()->AsLiteral();
   DCHECK(!key->value()->IsSmi());
   DCHECK(prop->IsSuperAccess());
 
@@ skipping 256 matching lines @@
   StoreToFrameField(StandardFrameConstants::kContextOffset, context_register());
   scope_ = saved_scope;
   __ jmp(&exit);
 
   // Try block code. Sets up the exception handler chain.
   __ bind(&try_entry);
 
   try_catch_depth_++;
   int handler_index = NewHandlerTableEntry();
   EnterTryBlock(handler_index, &handler_entry);
-  { TryCatch try_body(this);
+  {
+    Comment cmnt_try(masm(), "[ Try block");
     Visit(stmt->try_block());
   }
   ExitTryBlock(handler_index);
   try_catch_depth_--;
   __ bind(&exit);
 }
 
 
 void FullCodeGenerator::VisitTryFinallyStatement(TryFinallyStatement* stmt) {
   Comment cmnt(masm_, "[ TryFinallyStatement");
@@ skipping 20 matching lines @@
   Label try_entry, handler_entry, finally_entry;
   DeferredCommands deferred(this, &finally_entry);
 
   // Jump to try-handler setup and try-block code.
   __ jmp(&try_entry);
   __ bind(&handler_entry);
 
   // Exception handler code.  This code is only executed when an exception
   // is thrown.  Record the continuation and jump to the finally block.
   {
-    Comment cmt_handler(masm(), "[ Finally handler");
+    Comment cmnt_handler(masm(), "[ Finally handler");
     deferred.RecordThrow();
   }
 
   // Set up try handler.
   __ bind(&try_entry);
   int handler_index = NewHandlerTableEntry();
   EnterTryBlock(handler_index, &handler_entry);
   {
+    Comment cmnt_try(masm(), "[ Try block");
     TryFinally try_body(this, &deferred);
     Visit(stmt->try_block());
   }
   ExitTryBlock(handler_index);
   // Execute the finally block on the way out.  Clobber the unpredictable
   // value in the result register with one that's safe for GC because the
   // finally block will unconditionally preserve the result register on the
   // stack.
   ClearAccumulator();
   deferred.EmitFallThrough();
   // Fall through to the finally block.
 
   // Finally block implementation.
   __ bind(&finally_entry);
-  Comment cmnt_finally(masm(), "[ Finally block");
-  OperandStackDepthIncrement(2);  // Token and accumulator are on stack.
-  EnterFinallyBlock();
   {
-    Finally finally_body(this);
+    Comment cmnt_finally(masm(), "[ Finally block");
+    OperandStackDepthIncrement(2);  // Token and accumulator are on stack.
+    EnterFinallyBlock();
     Visit(stmt->finally_block());
+    ExitFinallyBlock();
+    OperandStackDepthDecrement(2);  // Token and accumulator were on stack.
   }
-  ExitFinallyBlock();
-  OperandStackDepthDecrement(2);  // Token and accumulator were on stack.
 
   {
     Comment cmnt_deferred(masm(), "[ Post-finally dispatch");
     deferred.EmitCommands();  // Return to the calling code.
   }
 }
 
 
 void FullCodeGenerator::VisitDebuggerStatement(DebuggerStatement* stmt) {
   Comment cmnt(masm_, "[ DebuggerStatement");
@@ skipping 225 matching lines @@
 
 void FullCodeGenerator::VisitEmptyParentheses(EmptyParentheses* expr) {
   UNREACHABLE();
 }
 
 
 void FullCodeGenerator::VisitRewritableExpression(RewritableExpression* expr) {
   Visit(expr->expression());
 }
 
+FullCodeGenerator::NestedStatement* FullCodeGenerator::TryFinally::Exit(
+    int* context_length) {
+  // The macros used here must preserve the result register.
 
-FullCodeGenerator::NestedStatement* FullCodeGenerator::TryFinally::Exit(
-    int* stack_depth, int* context_length) {
-  // The macros used here must preserve the result register.
+  // Calculate how many operands to drop to get down to handler block.
+  int stack_drop = codegen_->operand_stack_depth_ - GetStackDepthAtTarget();
+  DCHECK_GE(stack_drop, 0);
 
   // Because the handler block contains the context of the finally
   // code, we can restore it directly from there for the finally code
   // rather than iteratively unwinding contexts via their previous
   // links.
   if (*context_length > 0) {
-    __ Drop(*stack_depth);  // Down to the handler block.
+    __ Drop(stack_drop);  // Down to the handler block.
     // Restore the context to its dedicated register and the stack.
-    STATIC_ASSERT(TryFinally::kElementCount == 1);
+    STATIC_ASSERT(TryBlockConstant::kElementCount == 1);
     __ Pop(codegen_->context_register());
     codegen_->StoreToFrameField(StandardFrameConstants::kContextOffset,
                                 codegen_->context_register());
   } else {
     // Down to the handler block and also drop context.
-    __ Drop(*stack_depth + kElementCount);
+    __ Drop(stack_drop + TryBlockConstant::kElementCount);
   }
-  *stack_depth = 0;
-  *context_length = 0;
+
+  // The caller will ignore outputs.
+  *context_length = -1;
   return previous_;
 }
 
 void FullCodeGenerator::DeferredCommands::RecordBreak(Statement* target) {
   TokenId token = dispenser_.GetBreakContinueToken();
   commands_.push_back({kBreak, token, target});
   EmitJumpToFinally(token);
 }
 
 void FullCodeGenerator::DeferredCommands::RecordContinue(Statement* target) {
@@ skipping 245 matching lines @@
   return var->mode() == CONST_LEGACY || var->scope()->is_nonlinear() ||
          var->initializer_position() >= proxy->position();
 }
 
 
 #undef __
 
 
 }  // namespace internal
 }  // namespace v8