Clean up handling of global cell stores in the optimizing compiler.

src/arm/lithium-codegen-arm.cc

Index: src/arm/lithium-codegen-arm.cc
diff --git a/src/arm/lithium-codegen-arm.cc b/src/arm/lithium-codegen-arm.cc
index cdc464c32226e3ee2ebd40147b32c0ef953be8b7..4b68438300e32f8da20f84b9bb001ae7ba203c2b 100644
--- a/src/arm/lithium-codegen-arm.cc
+++ b/src/arm/lithium-codegen-arm.cc
@@ -2262,27 +2262,26 @@ void LCodeGen::DoLoadGlobalGeneric(LLoadGlobalGeneric* instr) {
 
 
 void LCodeGen::DoStoreGlobalCell(LStoreGlobalCell* instr) {
-  Register value = ToRegister(instr->InputAt(0));
-  Register scratch = scratch0();
-  Register scratch2 = ToRegister(instr->TempAt(0));
+  Register value = ToRegister(instr->value());
+  Register cell = scratch0();
 
   // Load the cell.
-  __ mov(scratch, Operand(Handle<Object>(instr->hydrogen()->cell())));
+  __ mov(cell, Operand(instr->hydrogen()->cell()));
 
   // If the cell we are storing to contains the hole it could have
   // been deleted from the property dictionary. In that case, we need
   // to update the property details in the property dictionary to mark
   // it as no longer deleted.
   if (instr->hydrogen()->RequiresHoleCheck()) {
-    __ ldr(scratch2,
-           FieldMemOperand(scratch, JSGlobalPropertyCell::kValueOffset));
-    __ LoadRoot(ip, Heap::kTheHoleValueRootIndex);
-    __ cmp(scratch2, ip);
+    // We use a temp to check the payload (CompareRoot might clobber ip).
+    Register payload = ToRegister(instr->TempAt(0));
+    __ ldr(payload, FieldMemOperand(cell, JSGlobalPropertyCell::kValueOffset));
+    __ CompareRoot(payload, Heap::kTheHoleValueRootIndex);
     DeoptimizeIf(eq, instr->environment());
   }
 
   // Store the value.
-  __ str(value, FieldMemOperand(scratch, JSGlobalPropertyCell::kValueOffset));
+  __ str(value, FieldMemOperand(cell, JSGlobalPropertyCell::kValueOffset));
   // Cells are always rescanned, so no write barrier here.
 }