Use Variable::binding_needs_init() to determine hole initialization

src/compiler/ast-graph-builder.cc

 // Copyright 2014 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.
 
 #include "src/compiler/ast-graph-builder.h"
 
 #include "src/ast/scopes.h"
 #include "src/compiler.h"
 #include "src/compiler/ast-loop-assignment-analyzer.h"
 #include "src/compiler/control-builders.h"
@@ skipping 1068 matching lines @@
   if (!CheckStackOverflow()) {
     AstVisitor<AstGraphBuilder>::Visit(expr);
   } else {
     ast_context()->ProduceValue(expr, jsgraph()->UndefinedConstant());
   }
 }
 
 
 void AstGraphBuilder::VisitVariableDeclaration(VariableDeclaration* decl) {
   Variable* variable = decl->proxy()->var();
-  VariableMode mode = decl->mode();
-  bool hole_init = mode == CONST || mode == LET;
   switch (variable->location()) {
     case VariableLocation::GLOBAL:
     case VariableLocation::UNALLOCATED: {
       DCHECK(!variable->binding_needs_init());
       FeedbackVectorSlot slot = decl->proxy()->VariableFeedbackSlot();
       DCHECK(!slot.IsInvalid());
       globals()->push_back(handle(Smi::FromInt(slot.ToInt()), isolate()));
       globals()->push_back(isolate()->factory()->undefined_value());
       break;
     }
     case VariableLocation::PARAMETER:
     case VariableLocation::LOCAL:
-      if (hole_init) {
+      if (variable->binding_needs_init()) {
         Node* value = jsgraph()->TheHoleConstant();
         environment()->Bind(variable, value);
       }
       break;
     case VariableLocation::CONTEXT:
-      if (hole_init) {
+      if (variable->binding_needs_init()) {
         Node* value = jsgraph()->TheHoleConstant();
         const Operator* op = javascript()->StoreContext(0, variable->index());
         NewNode(op, current_context(), value);
       }
       break;
     case VariableLocation::LOOKUP: {
-      DCHECK(!hole_init);
+      DCHECK(!variable->binding_needs_init());
       Node* name = jsgraph()->Constant(variable->name());
       const Operator* op = javascript()->CallRuntime(Runtime::kDeclareEvalVar);
       Node* store = NewNode(op, name);
       PrepareFrameState(store, decl->proxy()->id());
       break;
     }
   }
 }
 
 
@@ skipping 2189 matching lines @@
   return environment()->Pop();
 }
 
 
 Node* AstGraphBuilder::BuildVariableLoad(Variable* variable,
                                          BailoutId bailout_id,
                                          const VectorSlotPair& feedback,
                                          OutputFrameStateCombine combine,
                                          TypeofMode typeof_mode) {
   Node* the_hole = jsgraph()->TheHoleConstant();
-  VariableMode mode = variable->mode();
   switch (variable->location()) {
     case VariableLocation::GLOBAL:
     case VariableLocation::UNALLOCATED: {
       // Global var, const, or let variable.
       Handle<Name> name = variable->name();
       if (Node* node = TryLoadGlobalConstant(name)) return node;
       Node* value = BuildGlobalLoad(name, feedback, typeof_mode);
       PrepareFrameState(value, bailout_id, combine);
       return value;
     }
     case VariableLocation::PARAMETER:
     case VariableLocation::LOCAL: {
       // Local var, const, or let variable.
       Node* value = environment()->Lookup(variable);
-      if (mode == LET || mode == CONST) {
+      if (variable->binding_needs_init()) {
         // Perform check for uninitialized let/const variables.
         if (value->op() == the_hole->op()) {
           value = BuildThrowReferenceError(variable, bailout_id);
         } else if (value->opcode() == IrOpcode::kPhi) {
           value = BuildHoleCheckThenThrow(value, variable, value, bailout_id);
         }
       }
       return value;
     }
     case VariableLocation::CONTEXT: {
       // Context variable (potentially up the context chain).
       int depth = current_scope()->ContextChainLength(variable->scope());
       bool immutable = variable->maybe_assigned() == kNotAssigned;
       const Operator* op =
           javascript()->LoadContext(depth, variable->index(), immutable);
       Node* value = NewNode(op, current_context());
       // TODO(titzer): initialization checks are redundant for already
       // initialized immutable context loads, but only specialization knows.
       // Maybe specializer should be a parameter to the graph builder?
-      if (mode == LET || mode == CONST) {
+      if (variable->binding_needs_init()) {
         // Perform check for uninitialized let/const variables.
         value = BuildHoleCheckThenThrow(value, variable, value, bailout_id);
       }
       return value;
     }
     case VariableLocation::LOOKUP: {
       // Dynamic lookup of context variable (anywhere in the chain).
       Handle<String> name = variable->name();
       if (Node* node = TryLoadDynamicVariable(variable, name, bailout_id,
                                               feedback, combine, typeof_mode)) {
@@ skipping 68 matching lines @@
         if (is_strict(language_mode())) {
           return BuildThrowConstAssignError(bailout_id);
         }
         return value;
       } else if (mode == LET && op == Token::INIT) {
         // No initialization check needed because scoping guarantees it. Note
         // that we still perform a lookup to keep the variable live, because
         // baseline code might contain debug code that inspects the variable.
         Node* current = environment()->Lookup(variable);
         CHECK_NOT_NULL(current);
-      } else if (mode == LET && op != Token::INIT) {
-        // Perform an initialization check for let declared variables.
-        Node* current = environment()->Lookup(variable);
-        if (current->op() == the_hole->op()) {
-          return BuildThrowReferenceError(variable, bailout_id);
-        } else if (current->opcode() == IrOpcode::kPhi) {
-          BuildHoleCheckThenThrow(current, variable, value, bailout_id);
-        }
       } else if (mode == CONST && op == Token::INIT) {
         // Perform an initialization check for const {this} variables.
         // Note that the {this} variable is the only const variable being able
         // to trigger bind operations outside the TDZ, via {super} calls.
         Node* current = environment()->Lookup(variable);
         if (current->op() != the_hole->op() && variable->is_this()) {
           value = BuildHoleCheckElseThrow(current, variable, value, bailout_id);
         }
-      } else if (mode == CONST && op != Token::INIT) {
-        // Assignment to const is exception in all modes.
+      } else if (IsLexicalVariableMode(mode) && op != Token::INIT) {
+        // Perform an initialization check for lexically declared variables.
         Node* current = environment()->Lookup(variable);
-        if (current->op() == the_hole->op()) {
-          return BuildThrowReferenceError(variable, bailout_id);
-        } else if (current->opcode() == IrOpcode::kPhi) {
-          BuildHoleCheckThenThrow(current, variable, value, bailout_id);
+        if (variable->binding_needs_init()) {
+          if (current->op() == the_hole->op()) {
+            return BuildThrowReferenceError(variable, bailout_id);
+          } else if (current->opcode() == IrOpcode::kPhi) {
+            BuildHoleCheckThenThrow(current, variable, value, bailout_id);
+          }
         }
-        return BuildThrowConstAssignError(bailout_id);
+        if (mode == CONST) {
+          return BuildThrowConstAssignError(bailout_id);
+        }
       }
       environment()->Bind(variable, value);
       return value;
     case VariableLocation::CONTEXT: {
       // Context variable (potentially up the context chain).
       int depth = current_scope()->ContextChainLength(variable->scope());
       if (mode == CONST_LEGACY && op != Token::INIT) {
         // Non-initializing assignment to legacy const is
         // - exception in strict mode.
         // - ignored in sloppy mode.
         if (is_strict(language_mode())) {
           return BuildThrowConstAssignError(bailout_id);
         }
         return value;
-      } else if (mode == LET && op != Token::INIT) {
-        // Perform an initialization check for let declared variables.
-        const Operator* op =
-            javascript()->LoadContext(depth, variable->index(), false);
-        Node* current = NewNode(op, current_context());
-        value = BuildHoleCheckThenThrow(current, variable, value, bailout_id);
       } else if (mode == CONST && op == Token::INIT) {
         // Perform an initialization check for const {this} variables.
         // Note that the {this} variable is the only const variable being able
         // to trigger bind operations outside the TDZ, via {super} calls.
         if (variable->is_this()) {
           const Operator* op =
               javascript()->LoadContext(depth, variable->index(), false);
           Node* current = NewNode(op, current_context());
           value = BuildHoleCheckElseThrow(current, variable, value, bailout_id);
         }
-      } else if (mode == CONST && op != Token::INIT) {
-        // Assignment to const is exception in all modes.
-        const Operator* op =
-            javascript()->LoadContext(depth, variable->index(), false);
-        Node* current = NewNode(op, current_context());
-        BuildHoleCheckThenThrow(current, variable, value, bailout_id);
-        return BuildThrowConstAssignError(bailout_id);
+      } else if (IsLexicalVariableMode(mode) && op != Token::INIT) {
+        // Perform an initialization check for lexically declared variables.
+        if (variable->binding_needs_init()) {
+          const Operator* op =
+              javascript()->LoadContext(depth, variable->index(), false);
+          Node* current = NewNode(op, current_context());
+          value = BuildHoleCheckThenThrow(current, variable, value, bailout_id);
+        }
+        if (mode == CONST) {
+          // Assignment to const is exception in all modes.
+          return BuildThrowConstAssignError(bailout_id);
+        }
       }
       const Operator* op = javascript()->StoreContext(depth, variable->index());
       return NewNode(op, current_context(), value);
     }
     case VariableLocation::LOOKUP: {
       // Dynamic lookup of context variable (anywhere in the chain).
       Handle<Name> name = variable->name();
       Node* store = BuildDynamicStore(name, value);
       PrepareFrameState(store, bailout_id, combine);
       return store;
@@ skipping 795 matching lines @@
     // Phi does not exist yet, introduce one.
     value = NewPhi(inputs, value, control);
     value->ReplaceInput(inputs - 1, other);
   }
   return value;
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8