ARM: Optimize WrapReceiver

Optimize register constraints and code generated for WrapReceiver Lithium
instruction.

TEST=none
BUG=
R=ulan@chromium.org

Review URL: https://codereview.chromium.org/96993002

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@18180 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/arm/lithium-arm.cc

@@ -1084,7 +1084,7 @@ LInstruction* LChunkBuilder::DoWrapReceiver(HWrapReceiver* instr) {
   LOperand* receiver = UseRegisterAtStart(instr->receiver());
   LOperand* function = UseRegisterAtStart(instr->function());
   LWrapReceiver* result = new(zone()) LWrapReceiver(receiver, function);
-  return AssignEnvironment(DefineSameAsFirst(result));
+  return AssignEnvironment(DefineAsRegister(result));
 }
 
 

src/arm/lithium-codegen-arm.cc

@@ -3496,12 +3496,13 @@ void LCodeGen::DoArgumentsLength(LArgumentsLength* instr) {
 void LCodeGen::DoWrapReceiver(LWrapReceiver* instr) {
   Register receiver = ToRegister(instr->receiver());
   Register function = ToRegister(instr->function());
+  Register result = ToRegister(instr->result());
   Register scratch = scratch0();
 
   // If the receiver is null or undefined, we have to pass the global
   // object as a receiver to normal functions. Values have to be
   // passed unchanged to builtins and strict-mode functions.
-  Label global_object, receiver_ok;
+  Label global_object, result_in_receiver;
 
   // Do not transform the receiver to object for strict mode
   // functions.
@@ -3511,11 +3512,11 @@ void LCodeGen::DoWrapReceiver(LWrapReceiver* instr) {
          FieldMemOperand(scratch, SharedFunctionInfo::kCompilerHintsOffset));
   __ tst(scratch,
          Operand(1 << (SharedFunctionInfo::kStrictModeFunction + kSmiTagSize)));
-  __ b(ne, &receiver_ok);
+  __ b(ne, &result_in_receiver);
 
   // Do not transform the receiver to object for builtins.
   __ tst(scratch, Operand(1 << (SharedFunctionInfo::kNative + kSmiTagSize)));
-  __ b(ne, &receiver_ok);
+  __ b(ne, &result_in_receiver);
 
   // Normal function. Replace undefined or null with global receiver.
   __ LoadRoot(scratch, Heap::kNullValueRootIndex);
@@ -3530,13 +3531,21 @@ void LCodeGen::DoWrapReceiver(LWrapReceiver* instr) {
   DeoptimizeIf(eq, instr->environment());
   __ CompareObjectType(receiver, scratch, scratch, FIRST_SPEC_OBJECT_TYPE);
   DeoptimizeIf(lt, instr->environment());
-  __ jmp(&receiver_ok);
+  __ b(&result_in_receiver);
 
   __ bind(&global_object);
-  __ ldr(receiver, GlobalObjectOperand());
-  __ ldr(receiver,
-         FieldMemOperand(receiver, JSGlobalObject::kGlobalReceiverOffset));
-  __ bind(&receiver_ok);
+  __ ldr(result, GlobalObjectOperand());
+  __ ldr(result,
+         FieldMemOperand(result, JSGlobalObject::kGlobalReceiverOffset));
+  if (result.is(receiver)) {
+    __ bind(&result_in_receiver);
+  } else {
+    Label result_ok;
+    __ b(&result_ok);
+    __ bind(&result_in_receiver);
+    __ mov(result, receiver);
+    __ bind(&result_ok);
+  }
 }