[fullcodegen] Remove dead hole check logic

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/compile-time-value.h"
 #include "src/ast/scopes.h"
 #include "src/builtins/builtins-constructor.h"
 #include "src/code-factory.h"
@@ skipping 699 matching lines @@
     __ CompareRoot(rbx, Heap::kCatchContextMapRootIndex);
     __ Check(not_equal, 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(kScratchRegister, Heap::kTheHoleValueRootIndex);
-        __ movp(StackOperand(variable), kScratchRegister);
-      }
-      break;
-
     case VariableLocation::CONTEXT:
-      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:
     case VariableLocation::MODULE:
       UNREACHABLE();
   }
 }
 
 
 void FullCodeGenerator::VisitFunctionDeclaration(
@@ skipping 339 matching lines @@
           Operand(rsp, 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 variable, and all other types of variables.
   switch (var->location()) {
     case VariableLocation::UNALLOCATED: {
       Comment cmnt(masm_, "[ Global variable");
       EmitGlobalVariableLoad(proxy, typeof_mode);
       context()->Plug(rax);
       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 (proxy->hole_check_mode() == HoleCheckMode::kRequired) {
-        // 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);
-        __ Push(var->name());
-        __ CallRuntime(Runtime::kThrowReferenceError);
-        __ bind(&done);
-        context()->Plug(rax);
-        break;
-      }
       context()->Plug(var);
       break;
     }
 
     case VariableLocation::LOOKUP:
     case VariableLocation::MODULE:
       UNREACHABLE();
   }
 }
 
@@ skipping 291 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(),
-                             proxy->hole_check_mode());
+      EmitVariableAssignment(proxy->var(), expr->op(), expr->AssignmentSlot());
       PrepareForBailoutForId(expr->AssignmentId(), BailoutState::TOS_REGISTER);
       context()->Plug(rax);
       break;
     }
     case NAMED_PROPERTY:
       EmitNamedPropertyAssignment(expr);
       break;
     case KEYED_PROPERTY:
       EmitKeyedPropertyAssignment(expr);
       break;
@@ skipping 125 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,
-                             proxy->hole_check_mode());
+      EmitVariableAssignment(proxy->var(), Token::ASSIGN, slot);
       break;
     }
     case NAMED_PROPERTY: {
       PushOperand(rax);  // Preserve value.
       VisitForAccumulatorValue(prop->obj());
       __ Move(StoreDescriptor::ReceiverRegister(), rax);
       PopOperand(StoreDescriptor::ValueRegister());  // Restore value.
       CallStoreIC(slot, prop->key()->AsLiteral()->value());
       break;
     }
@@ skipping 20 matching lines @@
     Variable* var, MemOperand location) {
   __ movp(location, rax);
   if (var->IsContextSlot()) {
     __ movp(rdx, rax);
     __ RecordWriteContextSlot(
         rcx, Context::SlotOffset(var->index()), rdx, rbx, kDontSaveFPRegs);
   }
 }
 
 void FullCodeGenerator::EmitVariableAssignment(Variable* var, Token::Value op,
-                                               FeedbackVectorSlot slot,
-                                               HoleCheckMode hole_check_mode) {
+                                               FeedbackVectorSlot slot) {
+  DCHECK(!var->binding_needs_init());
   if (var->IsUnallocated()) {
     // Global var, const, or let.
     __ LoadGlobalObject(StoreDescriptor::ReceiverRegister());
     CallStoreIC(slot, var->name());
 
-  } else if (IsLexicalVariableMode(var->mode()) && op != Token::INIT) {
-    DCHECK(!var->IsLookupSlot());
-    DCHECK(var->IsStackAllocated() || var->IsContextSlot());
-    MemOperand location = VarOperand(var, rcx);
-    // Perform an initialization check for lexically declared variables.
-    if (hole_check_mode == HoleCheckMode::kRequired) {
-      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) {
-      EmitStoreToStackLocalOrContextSlot(var, location);
-    } else if (var->throw_on_const_assignment(language_mode())) {
+  } else if (var->mode() == CONST && op != Token::INIT) {
+    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, rcx);
-    __ movp(rdx, location);
-    __ CompareRoot(rdx, Heap::kTheHoleValueRootIndex);
-    __ j(equal, &uninitialized_this);
-    __ Push(var->name());
-    __ CallRuntime(Runtime::kThrowReferenceError);
-    __ bind(&uninitialized_this);
-    EmitStoreToStackLocalOrContextSlot(var, location);
-
   } else {
-    DCHECK(var->mode() != CONST || op == Token::INIT);
+    DCHECK(!var->is_this());
     DCHECK(var->IsStackAllocated() || var->IsContextSlot());
     DCHECK(!var->IsLookupSlot());
-    // Assignment to var or initializing assignment to let/const in harmony
-    // mode.
     MemOperand location = VarOperand(var, rcx);
-    if (FLAG_debug_code && var->mode() == LET && op == Token::INIT) {
-      // Check for an uninitialized let binding.
-      __ movp(rdx, location);
-      __ CompareRoot(rdx, Heap::kTheHoleValueRootIndex);
-      __ Check(equal, kLetBindingReInitialization);
-    }
     EmitStoreToStackLocalOrContextSlot(var, location);
   }
 }
 
 
 void FullCodeGenerator::EmitNamedPropertyAssignment(Assignment* expr) {
   // Assignment to a property, using a named store IC.
   Property* prop = expr->target()->AsProperty();
   DCHECK(prop != NULL);
   DCHECK(prop->key()->IsLiteral());
@@ skipping 716 matching lines @@
   patch_site.EmitPatchInfo();
   __ bind(&done);
 
   // Store the value returned in rax.
   switch (assign_type) {
     case VARIABLE: {
       VariableProxy* proxy = expr->expression()->AsVariableProxy();
       if (expr->is_postfix()) {
         // Perform the assignment as if via '='.
         { EffectContext context(this);
-          EmitVariableAssignment(proxy->var(), Token::ASSIGN, expr->CountSlot(),
-                                 proxy->hole_check_mode());
+          EmitVariableAssignment(proxy->var(), Token::ASSIGN,
+                                 expr->CountSlot());
           PrepareForBailoutForId(expr->AssignmentId(),
                                  BailoutState::TOS_REGISTER);
           context.Plug(rax);
         }
         // For all contexts except kEffect: We have the result on
         // top of the stack.
         if (!context()->IsEffect()) {
           context()->PlugTOS();
         }
       } else {
         // Perform the assignment as if via '='.
-        EmitVariableAssignment(proxy->var(), Token::ASSIGN, expr->CountSlot(),
-                               proxy->hole_check_mode());
+        EmitVariableAssignment(proxy->var(), Token::ASSIGN, expr->CountSlot());
         PrepareForBailoutForId(expr->AssignmentId(),
                                BailoutState::TOS_REGISTER);
         context()->Plug(rax);
       }
       break;
     }
     case NAMED_PROPERTY: {
       PopOperand(StoreDescriptor::ReceiverRegister());
       CallStoreIC(expr->CountSlot(), prop->key()->AsLiteral()->value());
       PrepareForBailoutForId(expr->AssignmentId(), BailoutState::TOS_REGISTER);
@@ skipping 325 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