Lithium: avoid registers for constants when possible.

src/arm/lithium-arm.cc

Index: src/arm/lithium-arm.cc
diff --git a/src/arm/lithium-arm.cc b/src/arm/lithium-arm.cc
index 66c108d4fea7b70969aaa736178c184d7c7a1371..913957e806bef9fa9ea661b078ab07a2300416b7 100644
--- a/src/arm/lithium-arm.cc
+++ b/src/arm/lithium-arm.cc
@@ -552,6 +552,11 @@ LOperand* LChunkBuilder::UseRegisterOrConstantAtStart(HValue* value) {
 }
 
 
+LOperand* LChunkBuilder::UseConstant(HValue* value) {
+  return chunk_->DefineConstantOperand(HConstant::cast(value));
+}
+
+
 LOperand* LChunkBuilder::UseAny(HValue* value) {
   return value->IsConstant()
       ? chunk_->DefineConstantOperand(HConstant::cast(value))
@@ -2378,7 +2383,9 @@ LInstruction* LChunkBuilder::DoAllocateObject(HAllocateObject* instr) {
 
 LInstruction* LChunkBuilder::DoAllocate(HAllocate* instr) {
   info()->MarkAsDeferredCalling();
-  LOperand* size = UseTempRegister(instr->size());
+  LOperand* size = instr->size()->IsConstant()
+      ? UseConstant(instr->size())
+      : UseTempRegister(instr->size());
   LOperand* temp1 = TempRegister();
   LOperand* temp2 = TempRegister();
   LAllocate* result = new(zone()) LAllocate(size, temp1, temp2);