X87: Use Variable::binding_needs_init() to determine hole initialization.

  port 6768456d (r38395)

  original commit message:
  The old code was using VariableMode, but that signal is both
  over-pessimistic (some CONST and LET variables need no hole-initialization)
  and inconsistent with other uses of the InitializationFlag enum (such
  as %LoadLookupSlot).

  This changes no observable behavior, but removes unnecessary hole
  initialization and hole checks in a few places, including
  block-scoped function declarations, super property lookups,
  and new.target.

BUG=

Review-Url: https://codereview.chromium.org/2223803002
Cr-Commit-Position: refs/heads/master@{#38468}

src/full-codegen/x87/full-codegen-x87.cc

@@ -706,13 +706,8 @@ void FullCodeGenerator::EmitDebugCheckDeclarationContext(Variable* variable) {
 
 void FullCodeGenerator::VisitVariableDeclaration(
     VariableDeclaration* declaration) {
-  // If it was not possible to allocate the variable at compile time, we
-  // need to "declare" it at runtime to make sure it actually exists in the
-  // local context.
   VariableProxy* proxy = declaration->proxy();
-  VariableMode mode = declaration->mode();
   Variable* variable = proxy->var();
-  bool hole_init = mode == LET || mode == CONST;
   switch (variable->location()) {
     case VariableLocation::GLOBAL:
     case VariableLocation::UNALLOCATED: {
@@ -725,7 +720,7 @@ void FullCodeGenerator::VisitVariableDeclaration(
     }
     case VariableLocation::PARAMETER:
     case VariableLocation::LOCAL:
-      if (hole_init) {
+      if (variable->binding_needs_init()) {
         Comment cmnt(masm_, "[ VariableDeclaration");
         __ mov(StackOperand(variable),
                Immediate(isolate()->factory()->the_hole_value()));
@@ -733,7 +728,7 @@ void FullCodeGenerator::VisitVariableDeclaration(
       break;
 
     case VariableLocation::CONTEXT:
-      if (hole_init) {
+      if (variable->binding_needs_init()) {
         Comment cmnt(masm_, "[ VariableDeclaration");
         EmitDebugCheckDeclarationContext(variable);
         __ mov(ContextOperand(esi, variable->index()),
@@ -745,8 +740,8 @@ void FullCodeGenerator::VisitVariableDeclaration(
 
     case VariableLocation::LOOKUP: {
       Comment cmnt(masm_, "[ VariableDeclaration");
-      DCHECK_EQ(VAR, mode);
-      DCHECK(!hole_init);
+      DCHECK_EQ(VAR, variable->mode());
+      DCHECK(!variable->binding_needs_init());
       __ push(Immediate(variable->name()));
       __ CallRuntime(Runtime::kDeclareEvalVar);
       PrepareForBailoutForId(proxy->id(), BailoutState::NO_REGISTERS);
@@ -1195,13 +1190,14 @@ void FullCodeGenerator::EmitDynamicLookupFastCase(VariableProxy* proxy,
   } else if (var->mode() == DYNAMIC_LOCAL) {
     Variable* local = var->local_if_not_shadowed();
     __ mov(eax, ContextSlotOperandCheckExtensions(local, slow));
-    if (local->mode() == LET || local->mode() == CONST) {
+    if (local->binding_needs_init()) {
       __ cmp(eax, isolate()->factory()->the_hole_value());
       __ j(not_equal, done);
       __ push(Immediate(var->name()));
       __ CallRuntime(Runtime::kThrowReferenceError);
+    } else {
+      __ jmp(done);
     }
-    __ jmp(done);
   }
 }
 
@@ -1244,17 +1240,14 @@ void FullCodeGenerator::EmitVariableLoad(VariableProxy* proxy,
                                                : "[ Stack variable");
 
       if (NeedsHoleCheckForLoad(proxy)) {
-        // Let and const need a read barrier.
+        // Throw a reference error when using an uninitialized let/const
+        // binding in harmony mode.
         Label done;
         GetVar(eax, var);
         __ cmp(eax, isolate()->factory()->the_hole_value());
         __ j(not_equal, &done, Label::kNear);
-        if (var->mode() == LET || var->mode() == CONST) {
-          // Throw a reference error when using an uninitialized let/const
-          // binding in harmony mode.
-          __ push(Immediate(var->name()));
-          __ CallRuntime(Runtime::kThrowReferenceError);
-        }
+        __ push(Immediate(var->name()));
+        __ CallRuntime(Runtime::kThrowReferenceError);
         __ bind(&done);
         context()->Plug(eax);
         break;
@@ -2082,34 +2075,25 @@ void FullCodeGenerator::EmitVariableAssignment(Variable* var, Token::Value op,
     EmitLoadStoreICSlot(slot);
     CallStoreIC();
 
-  } else if (var->mode() == LET && op != Token::INIT) {
-    // Non-initializing assignment to let variable needs a write barrier.
-    DCHECK(!var->IsLookupSlot());
-    DCHECK(var->IsStackAllocated() || var->IsContextSlot());
-    Label assign;
-    MemOperand location = VarOperand(var, ecx);
-    __ mov(edx, location);
-    __ cmp(edx, isolate()->factory()->the_hole_value());
-    __ j(not_equal, &assign, Label::kNear);
-    __ push(Immediate(var->name()));
-    __ CallRuntime(Runtime::kThrowReferenceError);
-    __ bind(&assign);
-    EmitStoreToStackLocalOrContextSlot(var, location);
-
-  } else if (var->mode() == CONST && op != Token::INIT) {
-    // Assignment to const variable needs a write barrier.
+  } else if (IsLexicalVariableMode(var->mode()) && op != Token::INIT) {
     DCHECK(!var->IsLookupSlot());
     DCHECK(var->IsStackAllocated() || var->IsContextSlot());
-    Label const_error;
     MemOperand location = VarOperand(var, ecx);
-    __ mov(edx, location);
-    __ cmp(edx, isolate()->factory()->the_hole_value());
-    __ j(not_equal, &const_error, Label::kNear);
-    __ push(Immediate(var->name()));
-    __ CallRuntime(Runtime::kThrowReferenceError);
-    __ bind(&const_error);
-    __ CallRuntime(Runtime::kThrowConstAssignError);
-
+    // Perform an initialization check for lexically declared variables.
+    if (var->binding_needs_init()) {
+      Label assign;
+      __ mov(edx, location);
+      __ cmp(edx, isolate()->factory()->the_hole_value());
+      __ j(not_equal, &assign, Label::kNear);
+      __ push(Immediate(var->name()));
+      __ CallRuntime(Runtime::kThrowReferenceError);
+      __ bind(&assign);
+    }
+    if (var->mode() == CONST) {
+      __ CallRuntime(Runtime::kThrowConstAssignError);
+    } else {
+      EmitStoreToStackLocalOrContextSlot(var, location);
+    }
   } 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());