Revert remove dead hole check logic

src/full-codegen/s390/full-codegen-s390.cc

 // Copyright 2015 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_S390
 
 #include "src/ast/compile-time-value.h"
 #include "src/ast/scopes.h"
 #include "src/builtins/builtins-constructor.h"
 #include "src/code-factory.h"
@@ skipping 676 matching lines @@
     __ Check(ne, kDeclarationInWithContext);
     __ CompareRoot(r3, 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(ip, Heap::kTheHoleValueRootIndex);
+        __ StoreP(ip, StackOperand(variable));
+      }
+      break;
+
     case VariableLocation::CONTEXT:
+      if (variable->binding_needs_init()) {
+        Comment cmnt(masm_, "[ VariableDeclaration");
+        EmitDebugCheckDeclarationContext(variable);
+        __ LoadRoot(ip, Heap::kTheHoleValueRootIndex);
+        __ StoreP(ip, 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(
     FunctionDeclaration* declaration) {
@@ skipping 355 matching lines @@
       context()->Plug(r2);
       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(r2, var);
+        __ CompareRoot(r2, Heap::kTheHoleValueRootIndex);
+        __ bne(&done);
+        __ mov(r2, Operand(var->name()));
+        __ push(r2);
+        __ CallRuntime(Runtime::kThrowReferenceError);
+        __ bind(&done);
+        context()->Plug(r2);
+        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());
+      EmitVariableAssignment(proxy->var(), expr->op(), expr->AssignmentSlot(),
+                             proxy->hole_check_mode());
       PrepareForBailoutForId(expr->AssignmentId(), BailoutState::TOS_REGISTER);
       context()->Plug(r2);
       break;
     }
     case NAMED_PROPERTY:
       EmitNamedPropertyAssignment(expr);
       break;
     case KEYED_PROPERTY:
       EmitKeyedPropertyAssignment(expr);
       break;
@@ skipping 205 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(r2);  // Preserve value.
       VisitForAccumulatorValue(prop->obj());
       __ Move(StoreDescriptor::ReceiverRegister(), r2);
       PopOperand(StoreDescriptor::ValueRegister());  // Restore value.
       CallStoreIC(slot, prop->key()->AsLiteral()->value());
       break;
     }
@@ skipping 21 matching lines @@
   if (var->IsContextSlot()) {
     // RecordWrite may destroy all its register arguments.
     __ LoadRR(r5, result_register());
     int offset = Context::SlotOffset(var->index());
     __ RecordWriteContextSlot(r3, offset, r5, r4, kLRHasBeenSaved,
                               kDontSaveFPRegs);
   }
 }
 
 void FullCodeGenerator::EmitVariableAssignment(Variable* var, Token::Value op,
-                                               FeedbackVectorSlot slot) {
-  DCHECK(!var->binding_needs_init());
+                                               FeedbackVectorSlot slot,
+                                               HoleCheckMode hole_check_mode) {
   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) {
+    // Non-initializing assignment to let variable needs a write barrier.
+    DCHECK(!var->IsLookupSlot());
+    DCHECK(var->IsStackAllocated() || var->IsContextSlot());
+    MemOperand location = VarOperand(var, r3);
+    // Perform an initialization check for lexically declared variables.
+    if (hole_check_mode == HoleCheckMode::kRequired) {
+      Label assign;
+      __ LoadP(r5, location);
+      __ CompareRoot(r5, Heap::kTheHoleValueRootIndex);
+      __ bne(&assign);
+      __ mov(r5, Operand(var->name()));
+      __ push(r5);
+      __ 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, r3);
+    __ LoadP(r5, location);
+    __ CompareRoot(r5, Heap::kTheHoleValueRootIndex);
+    __ beq(&uninitialized_this);
+    __ mov(r3, Operand(var->name()));
+    __ push(r3);
+    __ 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, r3);
+    if (FLAG_debug_code && var->mode() == LET && op == Token::INIT) {
+      // Check for an uninitialized let binding.
+      __ LoadP(r4, location);
+      __ CompareRoot(r4, Heap::kTheHoleValueRootIndex);
+      __ Check(eq, 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 671 matching lines @@
   patch_site.EmitPatchInfo();
   __ bind(&done);
 
   // Store the value returned in r2.
   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(r2);
         }
         // 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(r2);
       }
       break;
     }
     case NAMED_PROPERTY: {
       PopOperand(StoreDescriptor::ReceiverRegister());
       CallStoreIC(expr->CountSlot(), prop->key()->AsLiteral()->value());
       PrepareForBailoutForId(expr->AssignmentId(), BailoutState::TOS_REGISTER);
@@ skipping 314 matching lines @@
   USE(kOSRBranchInstruction);
   DCHECK(kOSRBranchInstruction == br_instr);
 
   DCHECK(interrupt_address ==
          isolate->builtins()->OnStackReplacement()->entry());
   return ON_STACK_REPLACEMENT;
 }
 }  // namespace internal
 }  // namespace v8
 #endif  // V8_TARGET_ARCH_S390