Stack-allocate block variables

src/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/v8.h"
 
 #include "src/ast.h"
 #include "src/ast-numbering.h"
 #include "src/code-factory.h"
 #include "src/codegen.h"
@@ skipping 1764 matching lines @@
                               back_edges.pc(i)) != INTERRUPT);
   }
   return true;
 }
 #endif  // DEBUG
 
 
 FullCodeGenerator::EnterBlockScopeIfNeeded::EnterBlockScopeIfNeeded(
     FullCodeGenerator* codegen, Scope* scope, BailoutId entry_id,
     BailoutId declarations_id, BailoutId exit_id)
-    : codegen_(codegen), scope_(scope), exit_id_(exit_id) {
+    : codegen_(codegen), exit_id_(exit_id) {
   saved_scope_ = codegen_->scope();
 
   if (scope == NULL) {
     codegen_->PrepareForBailoutForId(entry_id, NO_REGISTERS);
+    needs_block_context_ = false;
+    num_stack_slots_ = 0;
   } else {
+    needs_block_context_ = scope->ContextLocalCount() > 0;
     codegen_->scope_ = scope;
     {
       Comment cmnt(masm(), "[ Extend block context");
-      __ Push(scope->GetScopeInfo());
-      codegen_->PushFunctionArgumentForContextAllocation();
-      __ CallRuntime(Runtime::kPushBlockContext, 2);
 
-      // Replace the context stored in the frame.
-      codegen_->StoreToFrameField(StandardFrameConstants::kContextOffset,
-                                  codegen_->context_register());
+      if (needs_block_context_) {
+        DCHECK(scope->GetScopeInfo()->ContextLength() > 0);
+        __ Push(scope->GetScopeInfo());
+        codegen_->PushFunctionArgumentForContextAllocation();
+        __ CallRuntime(Runtime::kPushBlockContext, 2);
+
+        // Replace the context stored in the frame.
+        codegen_->StoreToFrameField(StandardFrameConstants::kContextOffset,
+                                    codegen_->context_register());
+      }
+      num_stack_slots_ = scope->num_stack_slots();
+      codegen_->AllocateLocals(scope->num_stack_slots());
       codegen_->PrepareForBailoutForId(entry_id, NO_REGISTERS);
     }
     {
       Comment cmnt(masm(), "[ Declarations");
       codegen_->VisitDeclarations(scope->declarations());
       codegen_->PrepareForBailoutForId(declarations_id, NO_REGISTERS);
     }
   }
 }
 
 
 FullCodeGenerator::EnterBlockScopeIfNeeded::~EnterBlockScopeIfNeeded() {
-  if (scope_ != NULL) {
+  if (needs_block_context_) {
     codegen_->LoadContextField(codegen_->context_register(),
                                Context::PREVIOUS_INDEX);
     // Update local stack frame context field.
     codegen_->StoreToFrameField(StandardFrameConstants::kContextOffset,
                                 codegen_->context_register());
   }
   codegen_->PrepareForBailoutForId(exit_id_, NO_REGISTERS);
+  codegen_->DeallocateLocals(num_stack_slots_);
   codegen_->scope_ = saved_scope_;
 }
 
 
 #undef __
 
 
 } }  // namespace v8::internal