Use Variable::binding_needs_init() to determine hole initialization

src/full-codegen/arm64/full-codegen-arm64.cc

 // Copyright 2013 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_ARM64
 
 #include "src/ast/scopes.h"
 #include "src/code-factory.h"
 #include "src/code-stubs.h"
 #include "src/codegen.h"
@@ skipping 738 matching lines @@
     __ CompareRoot(x1, Heap::kWithContextMapRootIndex);
     __ Check(ne, kDeclarationInWithContext);
     __ CompareRoot(x1, Heap::kCatchContextMapRootIndex);
     __ Check(ne, 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(x10, Heap::kTheHoleValueRootIndex);
         __ Str(x10, StackOperand(variable));
       }
       break;
 
     case VariableLocation::CONTEXT:
-      if (hole_init) {
+      if (variable->binding_needs_init()) {
         Comment cmnt(masm_, "[ VariableDeclaration");
         EmitDebugCheckDeclarationContext(variable);
         __ LoadRoot(x10, Heap::kTheHoleValueRootIndex);
         __ Str(x10, ContextMemOperand(cp, variable->index()));
         // 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());
       __ Mov(x2, Operand(variable->name()));
       __ Push(x2);
       __ CallRuntime(Runtime::kDeclareEvalVar);
       PrepareForBailoutForId(proxy->id(), BailoutState::NO_REGISTERS);
       break;
     }
   }
 }
 
 
@@ skipping 439 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);
     __ B(done);
   } else if (var->mode() == DYNAMIC_LOCAL) {
     Variable* local = var->local_if_not_shadowed();
     __ Ldr(x0, ContextSlotOperandCheckExtensions(local, slow));
-    if (local->mode() == LET || local->mode() == CONST) {
+    if (local->binding_needs_init()) {
       __ JumpIfNotRoot(x0, Heap::kTheHoleValueRootIndex, done);
       __ Mov(x0, Operand(var->name()));
       __ Push(x0);
       __ CallRuntime(Runtime::kThrowReferenceError);
+    } else {
+      __ B(done);
     }
-    __ B(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 23 matching lines @@
     }
 
     case VariableLocation::PARAMETER:
     case VariableLocation::LOCAL:
     case VariableLocation::CONTEXT: {
       DCHECK_EQ(NOT_INSIDE_TYPEOF, typeof_mode);
       Comment cmnt(masm_, var->IsContextSlot()
                               ? "Context variable"
                               : "Stack variable");
       if (NeedsHoleCheckForLoad(proxy)) {
-        // Let and const need a read barrier.
+        // Throw a reference error when using an uninitialized let/const
+        // binding in harmony mode.
+        Label done;
         GetVar(x0, var);
-        Label done;
         __ JumpIfNotRoot(x0, Heap::kTheHoleValueRootIndex, &done);
-        if (var->mode() == LET || var->mode() == CONST) {
-          // Throw a reference error when using an uninitialized let/const
-          // binding in harmony mode.
-          __ Mov(x0, Operand(var->name()));
-          __ Push(x0);
-          __ CallRuntime(Runtime::kThrowReferenceError);
-          __ Bind(&done);
-        }
+        __ Mov(x0, Operand(var->name()));
+        __ Push(x0);
+        __ CallRuntime(Runtime::kThrowReferenceError);
+        __ Bind(&done);
         context()->Plug(x0);
         break;
       }
       context()->Plug(var);
       break;
     }
 
     case VariableLocation::LOOKUP: {
       Label done, slow;
       // Generate code for loading from variables potentially shadowed by
@@ skipping 719 matching lines @@
 void FullCodeGenerator::EmitVariableAssignment(Variable* var, Token::Value op,
                                                FeedbackVectorSlot slot) {
   ASM_LOCATION("FullCodeGenerator::EmitVariableAssignment");
   if (var->IsUnallocated()) {
     // Global var, const, or let.
     __ Mov(StoreDescriptor::NameRegister(), Operand(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, x1);
-    __ Ldr(x10, location);
-    __ JumpIfNotRoot(x10, Heap::kTheHoleValueRootIndex, &assign);
-    __ Mov(x10, Operand(var->name()));
-    __ Push(x10);
-    __ CallRuntime(Runtime::kThrowReferenceError);
-    // Perform the assignment.
-    __ 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, x1);
-    __ Ldr(x10, location);
-    __ JumpIfNotRoot(x10, Heap::kTheHoleValueRootIndex, &const_error);
-    __ Mov(x10, Operand(var->name()));
-    __ Push(x10);
-    __ CallRuntime(Runtime::kThrowReferenceError);
-    __ Bind(&const_error);
-    __ CallRuntime(Runtime::kThrowConstAssignError);
-
+    // Perform an initialization check for lexically declared variables.
+    if (var->binding_needs_init()) {
+      Label assign;
+      __ Ldr(x10, location);
+      __ JumpIfNotRoot(x10, Heap::kTheHoleValueRootIndex, &assign);
+      __ Mov(x10, Operand(var->name()));
+      __ Push(x10);
+      __ 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, x1);
     __ Ldr(x10, location);
     __ JumpIfRoot(x10, Heap::kTheHoleValueRootIndex, &uninitialized_this);
     __ Mov(x0, Operand(var->name()));
     __ Push(x0);
     __ CallRuntime(Runtime::kThrowReferenceError);
@@ skipping 1748 matching lines @@
   }
 
   return INTERRUPT;
 }
 
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_ARM64