PPC/s390: Use Variable::binding_needs_init() to determine hole initialization

Port 6768456d

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.

R=adamk@chromium.org, joransiu@ca.ibm.com, jyan@ca.ibm.com, michael_dawson@ca.ibm.com, mbrandy@us.ibm.com

BUG=
LOG=N

Review-Url: https://codereview.chromium.org/2229383004
Cr-Commit-Position: refs/heads/master@{#38551}

src/full-codegen/ppc/full-codegen-ppc.cc

@@ -723,13 +723,8 @@ 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: {
@@ -742,7 +737,7 @@ void FullCodeGenerator::VisitVariableDeclaration(
     }
     case VariableLocation::PARAMETER:
     case VariableLocation::LOCAL:
-      if (hole_init) {
+      if (variable->binding_needs_init()) {
         Comment cmnt(masm_, "[ VariableDeclaration");
         __ LoadRoot(ip, Heap::kTheHoleValueRootIndex);
         __ StoreP(ip, StackOperand(variable));
@@ -750,7 +745,7 @@ void FullCodeGenerator::VisitVariableDeclaration(
       break;
 
     case VariableLocation::CONTEXT:
-      if (hole_init) {
+      if (variable->binding_needs_init()) {
         Comment cmnt(masm_, "[ VariableDeclaration");
         EmitDebugCheckDeclarationContext(variable);
         __ LoadRoot(ip, Heap::kTheHoleValueRootIndex);
@@ -762,8 +757,8 @@ 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());
       __ mov(r5, Operand(variable->name()));
       __ Push(r5);
       __ CallRuntime(Runtime::kDeclareEvalVar);
@@ -1243,15 +1238,16 @@ void FullCodeGenerator::EmitDynamicLookupFastCase(VariableProxy* proxy,
   } else if (var->mode() == DYNAMIC_LOCAL) {
     Variable* local = var->local_if_not_shadowed();
     __ LoadP(r3, ContextSlotOperandCheckExtensions(local, slow));
-    if (local->mode() == LET || local->mode() == CONST) {
+    if (local->binding_needs_init()) {
       __ CompareRoot(r3, Heap::kTheHoleValueRootIndex);
       __ bne(done);
       __ mov(r3, Operand(var->name()));
       __ push(r3);
       __ CallRuntime(Runtime::kThrowReferenceError);
-    }
+    } else {
       __ b(done);
     }
+  }
 }
 
 
@@ -1293,18 +1289,15 @@ void FullCodeGenerator::EmitVariableLoad(VariableProxy* proxy,
       Comment cmnt(masm_, var->IsContextSlot() ? "[ Context variable"
                                                : "[ Stack variable");
       if (NeedsHoleCheckForLoad(proxy)) {
+        // Throw a reference error when using an uninitialized let/const
+        // binding in harmony mode.
         Label done;
-        // Let and const need a read barrier.
         GetVar(r3, var);
         __ CompareRoot(r3, Heap::kTheHoleValueRootIndex);
         __ bne(&done);
-        if (var->mode() == LET || var->mode() == CONST) {
-          // Throw a reference error when using an uninitialized let/const
-          // binding in harmony mode.
         __ mov(r3, Operand(var->name()));
         __ push(r3);
         __ CallRuntime(Runtime::kThrowReferenceError);
-        }
         __ bind(&done);
         context()->Plug(r3);
         break;
@@ -2187,37 +2180,26 @@ 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.
+  } else if (IsLexicalVariableMode(var->mode()) && op != Token::INIT) {
     DCHECK(!var->IsLookupSlot());
     DCHECK(var->IsStackAllocated() || var->IsContextSlot());
-    Label assign;
     MemOperand location = VarOperand(var, r4);
+    // Perform an initialization check for lexically declared variables.
+    if (var->binding_needs_init()) {
+      Label assign;
       __ LoadP(r6, location);
       __ CompareRoot(r6, Heap::kTheHoleValueRootIndex);
       __ bne(&assign);
       __ mov(r6, Operand(var->name()));
       __ push(r6);
       __ CallRuntime(Runtime::kThrowReferenceError);
-    // Perform the assignment.
       __ bind(&assign);
-    EmitStoreToStackLocalOrContextSlot(var, location);
-
-  } else if (var->mode() == CONST && op != Token::INIT) {
-    // Assignment to const variable needs a write barrier.
-    DCHECK(!var->IsLookupSlot());
-    DCHECK(var->IsStackAllocated() || var->IsContextSlot());
-    Label const_error;
-    MemOperand location = VarOperand(var, r4);
-    __ LoadP(r6, location);
-    __ CompareRoot(r6, Heap::kTheHoleValueRootIndex);
-    __ bne(&const_error);
-    __ mov(r6, Operand(var->name()));
-    __ push(r6);
-    __ CallRuntime(Runtime::kThrowReferenceError);
-    __ bind(&const_error);
+    }
+    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());

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

@@ -699,13 +699,8 @@ 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: {
@@ -718,7 +713,7 @@ void FullCodeGenerator::VisitVariableDeclaration(
     }
     case VariableLocation::PARAMETER:
     case VariableLocation::LOCAL:
-      if (hole_init) {
+      if (variable->binding_needs_init()) {
         Comment cmnt(masm_, "[ VariableDeclaration");
         __ LoadRoot(ip, Heap::kTheHoleValueRootIndex);
         __ StoreP(ip, StackOperand(variable));
@@ -726,7 +721,7 @@ void FullCodeGenerator::VisitVariableDeclaration(
       break;
 
     case VariableLocation::CONTEXT:
-      if (hole_init) {
+      if (variable->binding_needs_init()) {
         Comment cmnt(masm_, "[ VariableDeclaration");
         EmitDebugCheckDeclarationContext(variable);
         __ LoadRoot(ip, Heap::kTheHoleValueRootIndex);
@@ -738,8 +733,8 @@ 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());
       __ mov(r4, Operand(variable->name()));
       __ Push(r4);
       __ CallRuntime(Runtime::kDeclareEvalVar);
@@ -1207,15 +1202,16 @@ void FullCodeGenerator::EmitDynamicLookupFastCase(VariableProxy* proxy,
   } else if (var->mode() == DYNAMIC_LOCAL) {
     Variable* local = var->local_if_not_shadowed();
     __ LoadP(r2, ContextSlotOperandCheckExtensions(local, slow));
-    if (local->mode() == LET || local->mode() == CONST) {
+    if (local->binding_needs_init()) {
       __ CompareRoot(r2, Heap::kTheHoleValueRootIndex);
       __ bne(done);
       __ mov(r2, Operand(var->name()));
       __ push(r2);
       __ CallRuntime(Runtime::kThrowReferenceError);
-    }
+    } else {
       __ b(done);
     }
+  }
 }
 
 void FullCodeGenerator::EmitGlobalVariableLoad(VariableProxy* proxy,
@@ -1255,18 +1251,15 @@ void FullCodeGenerator::EmitVariableLoad(VariableProxy* proxy,
       Comment cmnt(masm_, var->IsContextSlot() ? "[ Context variable"
                                                : "[ Stack variable");
       if (NeedsHoleCheckForLoad(proxy)) {
+        // Throw a reference error when using an uninitialized let/const
+        // binding in harmony mode.
         Label done;
-        // Let and const need a read barrier.
         GetVar(r2, var);
         __ CompareRoot(r2, Heap::kTheHoleValueRootIndex);
         __ bne(&done);
-        if (var->mode() == LET || var->mode() == CONST) {
-          // Throw a reference error when using an uninitialized let/const
-          // binding in harmony mode.
         __ mov(r2, Operand(var->name()));
         __ push(r2);
         __ CallRuntime(Runtime::kThrowReferenceError);
-        }
         __ bind(&done);
         context()->Plug(r2);
         break;
@@ -2141,37 +2134,27 @@ void FullCodeGenerator::EmitVariableAssignment(Variable* var, Token::Value op,
     EmitLoadStoreICSlot(slot);
     CallStoreIC();
 
-  } else if (var->mode() == LET && op != Token::INIT) {
+  } 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());
-    Label assign;
     MemOperand location = VarOperand(var, r3);
+    // Perform an initialization check for lexically declared variables.
+    if (var->binding_needs_init()) {
+      Label assign;
       __ LoadP(r5, location);
       __ CompareRoot(r5, Heap::kTheHoleValueRootIndex);
       __ bne(&assign);
       __ mov(r5, Operand(var->name()));
       __ push(r5);
       __ CallRuntime(Runtime::kThrowReferenceError);
-    // Perform the assignment.
       __ bind(&assign);
-    EmitStoreToStackLocalOrContextSlot(var, location);
-
-  } else if (var->mode() == CONST && op != Token::INIT) {
-    // Assignment to const variable needs a write barrier.
-    DCHECK(!var->IsLookupSlot());
-    DCHECK(var->IsStackAllocated() || var->IsContextSlot());
-    Label const_error;
-    MemOperand location = VarOperand(var, r3);
-    __ LoadP(r5, location);
-    __ CompareRoot(r5, Heap::kTheHoleValueRootIndex);
-    __ bne(&const_error, Label::kNear);
-    __ mov(r5, Operand(var->name()));
-    __ push(r5);
-    __ CallRuntime(Runtime::kThrowReferenceError);
-    __ bind(&const_error);
+    }
+    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());