Stack allocating block scoped variables.

src/full-codegen.cc

Index: src/full-codegen.cc
diff --git a/src/full-codegen.cc b/src/full-codegen.cc
index 960700b9e65ea41ff2cdef46ba8a0b0a84327dc3..f4aa1f3e823e74c0a6891c9c150b229cc0608757 100644
--- a/src/full-codegen.cc
+++ b/src/full-codegen.cc
@@ -795,12 +795,29 @@ void FullCodeGenerator::VisitBlock(Block* stmt) {
   SetStatementPosition(stmt);
 
   Scope* saved_scope = scope();
-  // Push a block context when entering a block with block scoped variables.
   if (stmt->block_scope() != NULL) {
-    { Comment cmnt(masm_, "[ Extend block context");
-      scope_ = stmt->block_scope();
+    scope_ = stmt->block_scope();
+    int num_stack_slots = scope_->num_stack_slots();
+
+    // Allocate stack locals.
+    if (num_stack_slots > 0) {
+      Comment cmnt(masm_, "[ Allocate block stack locals");
+      if (num_stack_slots == 1) {
+        __ Push(isolate()->factory()->the_hole_value());
+      } else {
+        __ Move(result_register(), isolate()->factory()->the_hole_value());
+        for (int i = 0; i < num_stack_slots; i++) {
+          __ push(result_register());
+        }
+      }
+    }
+
+    // Allocate context locals.
+    if (scope_->num_heap_slots() > 0) {
+      Comment cmnt(masm_, "[ Extend block context");
       Handle<ScopeInfo> scope_info = scope_->GetScopeInfo();
-      int heap_slots = scope_info->ContextLength() - Context::MIN_CONTEXT_SLOTS;
+      int heap_slots =
+          scope_info->ContextLength() - Context::MIN_CONTEXT_SLOTS;
       __ Push(scope_info);
       PushFunctionArgumentForContextAllocation();
       if (heap_slots <= FastNewBlockContextStub::kMaximumSlots) {
@@ -824,12 +841,22 @@ void FullCodeGenerator::VisitBlock(Block* stmt) {
   __ bind(nested_block.break_label());
   PrepareForBailoutForId(stmt->ExitId(), NO_REGISTERS);
 
-  // Pop block context if necessary.
   if (stmt->block_scope() != NULL) {
-    LoadContextField(context_register(), Context::PREVIOUS_INDEX);
-    // Update local stack frame context field.
-    StoreToFrameField(StandardFrameConstants::kContextOffset,
-                      context_register());
+    Scope* scope = stmt->block_scope();
+    int num_stack_slots = scope->num_stack_slots();
+
+    // Pop block context if necessary.
+    if (scope->num_heap_slots() > 0) {
+      LoadContextField(context_register(), Context::PREVIOUS_INDEX);
+      // Update local stack frame context field.
+      StoreToFrameField(StandardFrameConstants::kContextOffset,
+                        context_register());
+    }
+
+    // Deallocate stack locals.
+    if (num_stack_slots > 0) {
+      __ Drop(num_stack_slots);
+    }
   }
 }
 
@@ -1271,6 +1298,46 @@ void FullCodeGenerator::VisitThrow(Throw* expr) {
 }
 
 
+FullCodeGenerator::NestedStatement::NestedStatement(
+    FullCodeGenerator* codegen, int stack_delta)
+    : codegen_(codegen), stack_delta_(stack_delta) {
+  // Link into codegen's nesting stack.
+  previous_ = codegen->nesting_stack_;
+  codegen->nesting_stack_ = this;
+  stack_depth_ = stack_delta_;
+  if (previous_ != NULL) {
+    stack_depth_ += previous_->StackDepth();
+  } else {
+    stack_depth_ += codegen->function()->scope()->num_stack_slots();
+  }
+}
+
+
+FullCodeGenerator::NestedBlock::NestedBlock(
+    FullCodeGenerator* codegen, Block* block)
+  : Breakable(codegen,
+              block,
+              block->block_scope() == NULL ? 0
+              : block->block_scope()->num_stack_slots()) {
+  Scope* scope = block->block_scope();
+  if (scope != NULL) {
+    scope->set_stack_slots_depth(StackDepthBase());
+  }
+}
+
+
+FullCodeGenerator::NestedStatement* FullCodeGenerator::NestedBlock::Exit(
+    int* stack_depth,
+    int* context_length) {
+  Scope* scope = statement()->AsBlock()->block_scope();
+  if (scope != NULL) {
+    if (scope->num_heap_slots() > 0) ++(*context_length);
+    *stack_depth += scope->num_stack_slots();
+  }
+  return previous_;
+}
+
+
 FullCodeGenerator::NestedStatement* FullCodeGenerator::TryCatch::Exit(
     int* stack_depth,
     int* context_length) {