[stubs] Use a single slot for context globals.

src/full-codegen/ppc/full-codegen-ppc.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/v8.h"
 
 #if V8_TARGET_ARCH_PPC
 
 #include "src/code-factory.h"
 #include "src/code-stubs.h"
@@ skipping 1359 matching lines @@
 
 
 void FullCodeGenerator::EmitGlobalVariableLoad(VariableProxy* proxy,
                                                TypeofMode typeof_mode) {
   Variable* var = proxy->var();
   DCHECK(var->IsUnallocatedOrGlobalSlot() ||
          (var->IsLookupSlot() && var->mode() == DYNAMIC_GLOBAL));
   if (var->IsGlobalSlot()) {
     DCHECK(var->index() > 0);
     DCHECK(var->IsStaticGlobalObjectProperty());
-    // Each var occupies two slots in the context: for reads and writes.
     const int slot = var->index();
     const int depth = scope()->ContextChainLength(var->scope());
     if (depth <= LoadGlobalViaContextStub::kMaximumDepth) {
       __ mov(LoadGlobalViaContextDescriptor::SlotRegister(), Operand(slot));
       __ mov(LoadGlobalViaContextDescriptor::NameRegister(),
              Operand(var->name()));
       LoadGlobalViaContextStub stub(isolate(), depth);
       __ CallStub(&stub);
     } else {
       __ Push(Smi::FromInt(slot));
@@ skipping 1317 matching lines @@
     // Global var, const, or let.
     __ mov(StoreDescriptor::NameRegister(), Operand(var->name()));
     __ LoadP(StoreDescriptor::ReceiverRegister(), GlobalObjectOperand());
     if (FLAG_vector_stores) EmitLoadStoreICSlot(slot);
     CallStoreIC();
 
   } else if (var->IsGlobalSlot()) {
     // Global var, const, or let.
     DCHECK(var->index() > 0);
     DCHECK(var->IsStaticGlobalObjectProperty());
-    // Each var occupies two slots in the context: for reads and writes.
-    const int slot = var->index() + 1;
+    const int slot = var->index();
     const int depth = scope()->ContextChainLength(var->scope());
     if (depth <= StoreGlobalViaContextStub::kMaximumDepth) {
       __ mov(StoreGlobalViaContextDescriptor::SlotRegister(), Operand(slot));
       __ mov(StoreGlobalViaContextDescriptor::NameRegister(),
              Operand(var->name()));
       DCHECK(StoreGlobalViaContextDescriptor::ValueRegister().is(r3));
       StoreGlobalViaContextStub stub(isolate(), depth, language_mode());
       __ CallStub(&stub);
     } else {
       __ Push(Smi::FromInt(slot));
@@ skipping 2695 matching lines @@
     return ON_STACK_REPLACEMENT;
   }
 
   DCHECK(interrupt_address ==
          isolate->builtins()->OsrAfterStackCheck()->entry());
   return OSR_AFTER_STACK_CHECK;
 }
 }  // namespace internal
 }  // namespace v8
 #endif  // V8_TARGET_ARCH_PPC