[full-codegen] Eliminate unnecessary hole checks for stores

src/full-codegen/mips/full-codegen-mips.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_MIPS
 
 // Note on Mips implementation:
 //
 // The result_register() for mips is the 'v0' register, which is defined
 // by the ABI to contain function return values. However, the first
@@ skipping 1269 matching lines @@
       context()->Plug(v0);
       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->needs_hole_check()) {
+      if (proxy->hole_check_mode() == HoleCheckMode::kRequired) {
         // Throw a reference error when using an uninitialized let/const
         // binding in harmony mode.
         Label done;
         GetVar(v0, var);
         __ LoadRoot(at, Heap::kTheHoleValueRootIndex);
         __ subu(at, v0, at);  // Sub as compare: at == 0 on eq.
         __ Branch(&done, ne, at, Operand(zero_reg));
         __ li(a0, Operand(var->name()));
         __ push(a0);
         __ CallRuntime(Runtime::kThrowReferenceError);
@@ skipping 423 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(v0);
       break;
+    }
     case NAMED_PROPERTY:
       EmitNamedPropertyAssignment(expr);
       break;
     case NAMED_SUPER_PROPERTY:
       EmitNamedSuperPropertyStore(property);
       context()->Plug(v0);
       break;
     case KEYED_SUPER_PROPERTY:
       EmitKeyedSuperPropertyStore(property);
       context()->Plug(v0);
@@ skipping 268 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(result_register());  // Preserve value.
       VisitForAccumulatorValue(prop->obj());
       __ mov(StoreDescriptor::ReceiverRegister(), result_register());
       PopOperand(StoreDescriptor::ValueRegister());  // Restore value.
       CallStoreIC(slot, prop->key()->AsLiteral()->value());
       break;
     }
@@ skipping 54 matching lines @@
   __ sw(result_register(), location);
   if (var->IsContextSlot()) {
     // RecordWrite may destroy all its register arguments.
     __ Move(a3, result_register());
     int offset = Context::SlotOffset(var->index());
     __ RecordWriteContextSlot(
         a1, offset, a3, a2, kRAHasBeenSaved, 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.
     __ mov(StoreDescriptor::ValueRegister(), result_register());
     __ 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, a1);
     // Perform an initialization check for lexically declared variables.
-    if (var->binding_needs_init()) {
+    if (hole_check_mode == HoleCheckMode::kRequired) {
       Label assign;
       __ lw(a3, location);
       __ LoadRoot(t0, Heap::kTheHoleValueRootIndex);
       __ Branch(&assign, ne, a3, Operand(t0));
       __ li(a3, Operand(var->name()));
       __ push(a3);
       __ CallRuntime(Runtime::kThrowReferenceError);
       __ bind(&assign);
     }
     if (var->mode() != CONST) {
@@ skipping 1058 matching lines @@
 
   SetExpressionPosition(expr);
 
   Handle<Code> code = CodeFactory::BinaryOpIC(isolate(), Token::ADD).code();
   CallIC(code, expr->CountBinOpFeedbackId());
   patch_site.EmitPatchInfo();
   __ bind(&done);
 
   // Store the value returned in v0.
   switch (assign_type) {
-    case VARIABLE:
+    case VARIABLE: {
+      VariableProxy* proxy = expr->expression()->AsVariableProxy();
       if (expr->is_postfix()) {
         { 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(v0);
         }
         // For all contexts except EffectConstant we have the result on
         // top of the stack.
         if (!context()->IsEffect()) {
           context()->PlugTOS();
         }
       } else {
-        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(v0);
       }
       break;
+    }
     case NAMED_PROPERTY: {
       __ mov(StoreDescriptor::ValueRegister(), result_register());
       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 {
@@ skipping 406 matching lines @@
          reinterpret_cast<uint32_t>(
              isolate->builtins()->OnStackReplacement()->entry()));
   return ON_STACK_REPLACEMENT;
 }
 
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_MIPS