[full-codegen] Eliminate unnecessary hole checks for stores

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/full-codegen/full-codegen.h"
 #include "src/ast/compile-time-value.h"
 #include "src/ast/scopes.h"
 #include "src/code-factory.h"
@@ skipping 1221 matching lines @@
       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->needs_hole_check()) {
+      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);
@@ skipping 410 matching lines @@
     // Deoptimization point in case the binary operation may have side effects.
     PrepareForBailout(expr->binary_operation(), BailoutState::TOS_REGISTER);
   } else {
     VisitForAccumulatorValue(expr->value());
   }
 
   SetExpressionPosition(expr);
 
   // Store the value.
   switch (assign_type) {
-    case VARIABLE:
-      EmitVariableAssignment(expr->target()->AsVariableProxy()->var(),
-                             expr->op(), expr->AssignmentSlot());
+    case VARIABLE: {
+      VariableProxy* proxy = expr->target()->AsVariableProxy();
+      EmitVariableAssignment(proxy->var(), expr->op(), expr->AssignmentSlot(),
+                             proxy->hole_check_mode());
       PrepareForBailoutForId(expr->AssignmentId(), BailoutState::TOS_REGISTER);
       context()->Plug(rax);
       break;
+    }
     case NAMED_PROPERTY:
       EmitNamedPropertyAssignment(expr);
       break;
     case NAMED_SUPER_PROPERTY:
       EmitNamedSuperPropertyStore(property);
       context()->Plug(rax);
       break;
     case KEYED_SUPER_PROPERTY:
       EmitKeyedSuperPropertyStore(property);
       context()->Plug(rax);
@@ skipping 223 matching lines @@
 
 void FullCodeGenerator::EmitAssignment(Expression* expr,
                                        FeedbackVectorSlot slot) {
   DCHECK(expr->IsValidReferenceExpressionOrThis());
 
   Property* prop = expr->AsProperty();
   LhsKind assign_type = Property::GetAssignType(prop);
 
   switch (assign_type) {
     case VARIABLE: {
-      Variable* var = expr->AsVariableProxy()->var();
+      VariableProxy* proxy = expr->AsVariableProxy();
       EffectContext context(this);
-      EmitVariableAssignment(var, Token::ASSIGN, slot);
+      EmitVariableAssignment(proxy->var(), Token::ASSIGN, slot,
+                             proxy->hole_check_mode());
       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 52 matching lines @@
 void FullCodeGenerator::EmitStoreToStackLocalOrContextSlot(
     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) {
+                                               FeedbackVectorSlot slot,
+                                               HoleCheckMode hole_check_mode) {
   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 (var->binding_needs_init()) {
+    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);
@@ skipping 1045 matching lines @@
   __ movp(rdx, rax);
   __ Move(rax, Smi::FromInt(1));
   Handle<Code> code =
       CodeFactory::BinaryOpIC(isolate(), expr->binary_op()).code();
   CallIC(code, expr->CountBinOpFeedbackId());
   patch_site.EmitPatchInfo();
   __ bind(&done);
 
   // Store the value returned in rax.
   switch (assign_type) {
-    case VARIABLE:
+    case VARIABLE: {
+      VariableProxy* proxy = expr->expression()->AsVariableProxy();
       if (expr->is_postfix()) {
         // Perform the assignment as if via '='.
         { EffectContext context(this);
-          EmitVariableAssignment(expr->expression()->AsVariableProxy()->var(),
-                                 Token::ASSIGN, expr->CountSlot());
+          EmitVariableAssignment(proxy->var(), Token::ASSIGN, expr->CountSlot(),
+                                 proxy->hole_check_mode());
           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(expr->expression()->AsVariableProxy()->var(),
-                               Token::ASSIGN, expr->CountSlot());
+        EmitVariableAssignment(proxy->var(), Token::ASSIGN, expr->CountSlot(),
+                               proxy->hole_check_mode());
         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);
       if (expr->is_postfix()) {
         if (!context()->IsEffect()) {
           context()->PlugTOS();
         }
       } else {
         context()->Plug(rax);
@@ skipping 401 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