Elide unnecessary context reload in generated stubs.

src/ia32/lithium-ia32.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 1037 matching lines @@
 
 
 LInstruction* LChunkBuilder::DoThisFunction(HThisFunction* instr) {
   return instr->HasNoUses()
       ? NULL
       : DefineAsRegister(new(zone()) LThisFunction);
 }
 
 
 LInstruction* LChunkBuilder::DoContext(HContext* instr) {
-  return instr->HasNoUses() ? NULL : DefineAsRegister(new(zone()) LContext);
+  if (instr->HasNoUses()) return NULL;
+
+  if (info()->IsStub()) {
+    return DefineFixed(new(zone()) LContext, esi);
+  }
+
+  return DefineAsRegister(new(zone()) LContext);
 }
 
 
 LInstruction* LChunkBuilder::DoOuterContext(HOuterContext* instr) {
   LOperand* context = UseRegisterAtStart(instr->value());
   return DefineAsRegister(new(zone()) LOuterContext(context));
 }
 
 
 LInstruction* LChunkBuilder::DoDeclareGlobals(HDeclareGlobals* instr) {
@@ skipping 789 matching lines @@
     // Register allocator doesn't (yet) support allocation of double
     // temps. Reserve xmm1 explicitly.
     LOperand* temp = FixedTemp(xmm1);
     LClampTToUint8* result = new(zone()) LClampTToUint8(reg, temp);
     return AssignEnvironment(DefineFixed(result, eax));
   }
 }
 
 
 LInstruction* LChunkBuilder::DoReturn(HReturn* instr) {
-  return new(zone()) LReturn(UseFixed(instr->value(), eax));
+  LOperand* context = info()->IsStub()
+      ? UseFixed(instr->context(), esi)
+      : NULL;
+  return new(zone()) LReturn(UseFixed(instr->value(), eax), context);
 }
 
 
 LInstruction* LChunkBuilder::DoConstant(HConstant* instr) {
   Representation r = instr->representation();
   if (r.IsInteger32()) {
     return DefineAsRegister(new(zone()) LConstantI);
   } else if (r.IsDouble()) {
     double value = instr->DoubleValue();
     LOperand* temp = (BitCast<uint64_t, double>(value) != 0)
@@ skipping 599 matching lines @@
 LInstruction* LChunkBuilder::DoLoadFieldByIndex(HLoadFieldByIndex* instr) {
   LOperand* object = UseRegister(instr->object());
   LOperand* index = UseTempRegister(instr->index());
   return DefineSameAsFirst(new(zone()) LLoadFieldByIndex(object, index));
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_IA32