Use Variable::binding_needs_init() to determine hole initialization

src/full-codegen/x64/full-codegen-x64.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.
 
 #if V8_TARGET_ARCH_X64
 
 #include "src/ast/scopes.h"
 #include "src/code-factory.h"
 #include "src/code-stubs.h"
 #include "src/codegen.h"
@@ skipping 701 matching lines @@
     __ CompareRoot(rbx, Heap::kWithContextMapRootIndex);
     __ Check(not_equal, kDeclarationInWithContext);
     __ CompareRoot(rbx, Heap::kCatchContextMapRootIndex);
     __ Check(not_equal, kDeclarationInCatchContext);
   }
 }
 
 
 void FullCodeGenerator::VisitVariableDeclaration(
     VariableDeclaration* declaration) {
-  // If it was not possible to allocate the variable at compile time, we
-  // need to "declare" it at runtime to make sure it actually exists in the
-  // local context.
   VariableProxy* proxy = declaration->proxy();
-  VariableMode mode = declaration->mode();
   Variable* variable = proxy->var();
-  bool hole_init = mode == LET || mode == CONST;
   switch (variable->location()) {
     case VariableLocation::GLOBAL:
     case VariableLocation::UNALLOCATED: {
       DCHECK(!variable->binding_needs_init());
       FeedbackVectorSlot slot = proxy->VariableFeedbackSlot();
       DCHECK(!slot.IsInvalid());
       globals_->Add(handle(Smi::FromInt(slot.ToInt()), isolate()), zone());
       globals_->Add(isolate()->factory()->undefined_value(), zone());
       break;
     }
     case VariableLocation::PARAMETER:
     case VariableLocation::LOCAL:
-      if (hole_init) {
+      if (variable->binding_needs_init()) {
         Comment cmnt(masm_, "[ VariableDeclaration");
         __ LoadRoot(kScratchRegister, Heap::kTheHoleValueRootIndex);
         __ movp(StackOperand(variable), kScratchRegister);
       }
       break;
 
     case VariableLocation::CONTEXT:
-      if (hole_init) {
+      if (variable->binding_needs_init()) {
         Comment cmnt(masm_, "[ VariableDeclaration");
         EmitDebugCheckDeclarationContext(variable);
         __ LoadRoot(kScratchRegister, Heap::kTheHoleValueRootIndex);
         __ movp(ContextOperand(rsi, variable->index()), kScratchRegister);
         // No write barrier since the hole value is in old space.
         PrepareForBailoutForId(proxy->id(), BailoutState::NO_REGISTERS);
       }
       break;
 
     case VariableLocation::LOOKUP: {
       Comment cmnt(masm_, "[ VariableDeclaration");
-      DCHECK_EQ(VAR, mode);
-      DCHECK(!hole_init);
+      DCHECK_EQ(VAR, variable->mode());
+      DCHECK(!variable->binding_needs_init());
       __ Push(variable->name());
       __ CallRuntime(Runtime::kDeclareEvalVar);
       PrepareForBailoutForId(proxy->id(), BailoutState::NO_REGISTERS);
       break;
     }
   }
 }
 
 
 void FullCodeGenerator::VisitFunctionDeclaration(
@@ skipping 443 matching lines @@
   // introducing variables.  In those cases, we do not want to
   // perform a runtime call for all variables in the scope
   // containing the eval.
   Variable* var = proxy->var();
   if (var->mode() == DYNAMIC_GLOBAL) {
     EmitLoadGlobalCheckExtensions(proxy, typeof_mode, slow);
     __ jmp(done);
   } else if (var->mode() == DYNAMIC_LOCAL) {
     Variable* local = var->local_if_not_shadowed();
     __ movp(rax, ContextSlotOperandCheckExtensions(local, slow));
-    if (local->mode() == LET || local->mode() == CONST) {
+    if (local->binding_needs_init()) {
       __ CompareRoot(rax, Heap::kTheHoleValueRootIndex);
       __ j(not_equal, done);
       __ Push(var->name());
       __ CallRuntime(Runtime::kThrowReferenceError);
+    } else {
+      __ jmp(done);
     }
-    __ jmp(done);
   }
 }
 
 
 void FullCodeGenerator::EmitGlobalVariableLoad(VariableProxy* proxy,
                                                TypeofMode typeof_mode) {
 #ifdef DEBUG
   Variable* var = proxy->var();
   DCHECK(var->IsUnallocatedOrGlobalSlot() ||
          (var->IsLookupSlot() && var->mode() == DYNAMIC_GLOBAL));
@@ skipping 22 matching lines @@
       break;
     }
 
     case VariableLocation::PARAMETER:
     case VariableLocation::LOCAL:
     case VariableLocation::CONTEXT: {
       DCHECK_EQ(NOT_INSIDE_TYPEOF, typeof_mode);
       Comment cmnt(masm_, var->IsContextSlot() ? "[ Context slot"
                                                : "[ Stack slot");
       if (NeedsHoleCheckForLoad(proxy)) {
-        // Let and const need a read barrier.
+        // Throw a reference error when using an uninitialized let/const
+        // binding in harmony mode.
+        DCHECK(IsLexicalVariableMode(var->mode()));
         Label done;
         GetVar(rax, var);
         __ CompareRoot(rax, Heap::kTheHoleValueRootIndex);
         __ j(not_equal, &done, Label::kNear);
-        if (var->mode() == LET || var->mode() == CONST) {
-          // Throw a reference error when using an uninitialized let/const
-          // binding in harmony mode.
-          __ Push(var->name());
-          __ CallRuntime(Runtime::kThrowReferenceError);
-        }
+        __ Push(var->name());
+        __ CallRuntime(Runtime::kThrowReferenceError);
         __ bind(&done);
         context()->Plug(rax);
         break;
       }
       context()->Plug(var);
       break;
     }
 
     case VariableLocation::LOOKUP: {
       Comment cmnt(masm_, "[ Lookup slot");
@@ skipping 761 matching lines @@
 
 void FullCodeGenerator::EmitVariableAssignment(Variable* var, Token::Value op,
                                                FeedbackVectorSlot slot) {
   if (var->IsUnallocated()) {
     // Global var, const, or let.
     __ Move(StoreDescriptor::NameRegister(), var->name());
     __ LoadGlobalObject(StoreDescriptor::ReceiverRegister());
     EmitLoadStoreICSlot(slot);
     CallStoreIC();
 
-  } else if (var->mode() == LET && op != Token::INIT) {
-    // Non-initializing assignment to let variable needs a write barrier.
+  } else if (IsLexicalVariableMode(var->mode()) && op != Token::INIT) {
     DCHECK(!var->IsLookupSlot());
     DCHECK(var->IsStackAllocated() || var->IsContextSlot());
-    Label assign;
     MemOperand location = VarOperand(var, rcx);
-    __ movp(rdx, location);
-    __ CompareRoot(rdx, Heap::kTheHoleValueRootIndex);
-    __ j(not_equal, &assign, Label::kNear);
-    __ Push(var->name());
-    __ CallRuntime(Runtime::kThrowReferenceError);
-    __ bind(&assign);
-    EmitStoreToStackLocalOrContextSlot(var, location);
-
-  } else if (var->mode() == CONST && op != Token::INIT) {
-    // Assignment to const variable needs a write barrier.
-    DCHECK(!var->IsLookupSlot());
-    DCHECK(var->IsStackAllocated() || var->IsContextSlot());
-    Label const_error;
-    MemOperand location = VarOperand(var, rcx);
-    __ movp(rdx, location);
-    __ CompareRoot(rdx, Heap::kTheHoleValueRootIndex);
-    __ j(not_equal, &const_error, Label::kNear);
-    __ Push(var->name());
-    __ CallRuntime(Runtime::kThrowReferenceError);
-    __ bind(&const_error);
-    __ CallRuntime(Runtime::kThrowConstAssignError);
+    // Perform an initialization check for lexically declared variables.
+    if (var->binding_needs_init()) {
+      Label assign;
+      __ movp(rdx, location);
+      __ CompareRoot(rdx, Heap::kTheHoleValueRootIndex);
+      __ j(not_equal, &assign, Label::kNear);
+      __ Push(var->name());
+      __ CallRuntime(Runtime::kThrowReferenceError);
+      __ bind(&assign);
+    }
+    if (var->mode() == CONST) {
+      __ CallRuntime(Runtime::kThrowConstAssignError);
+    } else {
+      EmitStoreToStackLocalOrContextSlot(var, location);
+    }
 
   } else if (var->is_this() && var->mode() == CONST && op == Token::INIT) {
     // Initializing assignment to const {this} needs a write barrier.
     DCHECK(var->IsStackAllocated() || var->IsContextSlot());
     Label uninitialized_this;
     MemOperand location = VarOperand(var, rcx);
     __ movp(rdx, location);
     __ CompareRoot(rdx, Heap::kTheHoleValueRootIndex);
     __ j(equal, &uninitialized_this);
     __ Push(var->name());
@@ skipping 1554 matching lines @@
   DCHECK_EQ(
       isolate->builtins()->OnStackReplacement()->entry(),
       Assembler::target_address_at(call_target_address, unoptimized_code));
   return ON_STACK_REPLACEMENT;
 }
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_X64