Revert remove dead hole check logic

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/compile-time-value.h"
 #include "src/ast/scopes.h"
 #include "src/builtins/builtins-constructor.h"
 #include "src/code-factory.h"
@@ skipping 730 matching lines @@
     __ CompareRoot(x1, Heap::kCatchContextMapRootIndex);
     __ Check(ne, kDeclarationInCatchContext);
   }
 }
 
 
 void FullCodeGenerator::VisitVariableDeclaration(
     VariableDeclaration* declaration) {
   VariableProxy* proxy = declaration->proxy();
   Variable* variable = proxy->var();
-  DCHECK(!variable->binding_needs_init());
   switch (variable->location()) {
     case VariableLocation::UNALLOCATED: {
+      DCHECK(!variable->binding_needs_init());
       globals_->Add(variable->name(), zone());
       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 (variable->binding_needs_init()) {
+        Comment cmnt(masm_, "[ VariableDeclaration");
+        __ LoadRoot(x10, Heap::kTheHoleValueRootIndex);
+        __ Str(x10, StackOperand(variable));
+      }
+      break;
+
     case VariableLocation::CONTEXT:
+      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:
     case VariableLocation::MODULE:
       UNREACHABLE();
   }
 }
 
 
 void FullCodeGenerator::VisitFunctionDeclaration(
@@ skipping 336 matching lines @@
   __ Peek(StoreDescriptor::ValueRegister(), offset * kPointerSize);
   CallStoreIC(slot, isolate()->factory()->home_object_symbol());
 }
 
 void FullCodeGenerator::EmitVariableLoad(VariableProxy* proxy,
                                          TypeofMode typeof_mode) {
   // Record position before possible IC call.
   SetExpressionPosition(proxy);
   PrepareForBailoutForId(proxy->BeforeId(), BailoutState::NO_REGISTERS);
   Variable* var = proxy->var();
-  DCHECK(!var->binding_needs_init());
 
   // Two cases: global variables and all other types of variables.
   switch (var->location()) {
     case VariableLocation::UNALLOCATED: {
       Comment cmnt(masm_, "Global variable");
       EmitGlobalVariableLoad(proxy, typeof_mode);
       context()->Plug(x0);
       break;
     }
 
     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 (proxy->hole_check_mode() == HoleCheckMode::kRequired) {
+        // Throw a reference error when using an uninitialized let/const
+        // binding in harmony mode.
+        Label done;
+        GetVar(x0, var);
+        __ JumpIfNotRoot(x0, Heap::kTheHoleValueRootIndex, &done);
+        __ Mov(x0, Operand(var->name()));
+        __ Push(x0);
+        __ CallRuntime(Runtime::kThrowReferenceError);
+        __ Bind(&done);
+        context()->Plug(x0);
+        break;
+      }
       context()->Plug(var);
       break;
     }
 
     case VariableLocation::LOOKUP:
     case VariableLocation::MODULE:
       UNREACHABLE();
   }
 }
 
@@ skipping 295 matching lines @@
   } else {
     VisitForAccumulatorValue(expr->value());
   }
 
   SetExpressionPosition(expr);
 
   // Store the value.
   switch (assign_type) {
     case VARIABLE: {
       VariableProxy* proxy = expr->target()->AsVariableProxy();
-      EmitVariableAssignment(proxy->var(), expr->op(), expr->AssignmentSlot());
+      EmitVariableAssignment(proxy->var(), expr->op(), expr->AssignmentSlot(),
+                             proxy->hole_check_mode());
       PrepareForBailoutForId(expr->AssignmentId(), BailoutState::TOS_REGISTER);
       context()->Plug(x0);
       break;
     }
     case NAMED_PROPERTY:
       EmitNamedPropertyAssignment(expr);
       break;
     case KEYED_PROPERTY:
       EmitKeyedPropertyAssignment(expr);
       break;
@@ skipping 120 matching lines @@
                                        FeedbackVectorSlot slot) {
   DCHECK(expr->IsValidReferenceExpressionOrThis());
 
   Property* prop = expr->AsProperty();
   LhsKind assign_type = Property::GetAssignType(prop);
 
   switch (assign_type) {
     case VARIABLE: {
       VariableProxy* proxy = expr->AsVariableProxy();
       EffectContext context(this);
-      EmitVariableAssignment(proxy->var(), Token::ASSIGN, slot);
+      EmitVariableAssignment(proxy->var(), Token::ASSIGN, slot,
+                             proxy->hole_check_mode());
       break;
     }
     case NAMED_PROPERTY: {
       PushOperand(x0);  // Preserve value.
       VisitForAccumulatorValue(prop->obj());
       // TODO(all): We could introduce a VisitForRegValue(reg, expr) to avoid
       // this copy.
       __ Mov(StoreDescriptor::ReceiverRegister(), x0);
       PopOperand(StoreDescriptor::ValueRegister());  // Restore value.
       CallStoreIC(slot, prop->key()->AsLiteral()->value());
@@ skipping 24 matching lines @@
   if (var->IsContextSlot()) {
     // RecordWrite may destroy all its register arguments.
     __ Mov(x10, result_register());
     int offset = Context::SlotOffset(var->index());
     __ RecordWriteContextSlot(
         x1, offset, x10, x11, kLRHasBeenSaved, kDontSaveFPRegs);
   }
 }
 
 void FullCodeGenerator::EmitVariableAssignment(Variable* var, Token::Value op,
-                                               FeedbackVectorSlot slot) {
+                                               FeedbackVectorSlot slot,
+                                               HoleCheckMode hole_check_mode) {
   ASM_LOCATION("FullCodeGenerator::EmitVariableAssignment");
-  DCHECK(!var->binding_needs_init());
   if (var->IsUnallocated()) {
     // Global var, const, or let.
     __ LoadGlobalObject(StoreDescriptor::ReceiverRegister());
     CallStoreIC(slot, var->name());
 
-  } else if (var->mode() == CONST && op != Token::INIT) {
-    if (var->throw_on_const_assignment(language_mode())) {
+  } else if (IsLexicalVariableMode(var->mode()) && op != Token::INIT) {
+    DCHECK(!var->IsLookupSlot());
+    DCHECK(var->IsStackAllocated() || var->IsContextSlot());
+    MemOperand location = VarOperand(var, x1);
+    // 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) {
+      EmitStoreToStackLocalOrContextSlot(var, location);
+    } else if (var->throw_on_const_assignment(language_mode())) {
       __ CallRuntime(Runtime::kThrowConstAssignError);
     }
+  } 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);
+    __ bind(&uninitialized_this);
+    EmitStoreToStackLocalOrContextSlot(var, location);
+
   } else {
-    DCHECK(!var->is_this());
+    DCHECK(var->mode() != CONST || op == Token::INIT);
     DCHECK(var->IsStackAllocated() || var->IsContextSlot());
     DCHECK(!var->IsLookupSlot());
+    // Assignment to var or initializing assignment to let/const in harmony
+    // mode.
     MemOperand location = VarOperand(var, x1);
+    if (FLAG_debug_code && var->mode() == LET && op == Token::INIT) {
+      __ Ldr(x10, location);
+      __ CompareRoot(x10, Heap::kTheHoleValueRootIndex);
+      __ Check(eq, kLetBindingReInitialization);
+    }
     EmitStoreToStackLocalOrContextSlot(var, location);
   }
 }
 
 
 void FullCodeGenerator::EmitNamedPropertyAssignment(Assignment* expr) {
   ASM_LOCATION("FullCodeGenerator::EmitNamedPropertyAssignment");
   // Assignment to a property, using a named store IC.
   Property* prop = expr->target()->AsProperty();
   DCHECK(prop != NULL);
@@ skipping 712 matching lines @@
     patch_site.EmitPatchInfo();
   }
   __ Bind(&done);
 
   // Store the value returned in x0.
   switch (assign_type) {
     case VARIABLE: {
       VariableProxy* proxy = expr->expression()->AsVariableProxy();
       if (expr->is_postfix()) {
         { EffectContext context(this);
-          EmitVariableAssignment(proxy->var(), Token::ASSIGN,
-                                 expr->CountSlot());
+          EmitVariableAssignment(proxy->var(), Token::ASSIGN, expr->CountSlot(),
+                                 proxy->hole_check_mode());
           PrepareForBailoutForId(expr->AssignmentId(),
                                  BailoutState::TOS_REGISTER);
           context.Plug(x0);
         }
         // For all contexts except EffectConstant We have the result on
         // top of the stack.
         if (!context()->IsEffect()) {
           context()->PlugTOS();
         }
       } else {
-        EmitVariableAssignment(proxy->var(), Token::ASSIGN, expr->CountSlot());
+        EmitVariableAssignment(proxy->var(), Token::ASSIGN, expr->CountSlot(),
+                               proxy->hole_check_mode());
         PrepareForBailoutForId(expr->AssignmentId(),
                                BailoutState::TOS_REGISTER);
         context()->Plug(x0);
       }
       break;
     }
     case NAMED_PROPERTY: {
       PopOperand(StoreDescriptor::ReceiverRegister());
       CallStoreIC(expr->CountSlot(), prop->key()->AsLiteral()->value());
       PrepareForBailoutForId(expr->AssignmentId(), BailoutState::TOS_REGISTER);
@@ skipping 427 matching lines @@
   }
 
   return INTERRUPT;
 }
 
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_ARM64