Improve register usage for StoreInstanceField.

runtime/vm/intermediate_language_x64.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/globals.h"  // Needed here to get TARGET_ARCH_X64.
 #if defined(TARGET_ARCH_X64)
 
 #include "vm/intermediate_language.h"
 
 #include "lib/error.h"
@@ skipping 954 matching lines @@
   }
 }
 
 
 LocationSummary* StoreInstanceFieldInstr::MakeLocationSummary() const {
   const intptr_t kNumInputs = 2;
   const intptr_t num_temps = 0;
   LocationSummary* summary =
       new LocationSummary(kNumInputs, num_temps, LocationSummary::kNoCall);
   summary->set_in(0, Location::RequiresRegister());
-  summary->set_in(1,
-      value()->NeedsStoreBuffer() ? Location::WritableRegister()
-                                  : Location::RequiresRegister());
+  summary->set_in(1, (value()->NeedsStoreBuffer() && emit_store_barrier())
+                       ? Location::WritableRegister()
+                       : Location::RegisterOrConstant(value()));
   return summary;
 }
 
 
 void StoreInstanceFieldInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
   Register instance_reg = locs()->in(0).reg();
-  Register value_reg = locs()->in(1).reg();
   if (this->value()->NeedsStoreBuffer() && emit_store_barrier()) {
+    Register value_reg = locs()->in(1).reg();
     __ StoreIntoObject(instance_reg,
         FieldAddress(instance_reg, field().Offset()), value_reg);
   } else {
-    __ StoreIntoObjectNoBarrier(instance_reg,
-        FieldAddress(instance_reg, field().Offset()), value_reg);
+    if (locs()->in(1).IsConstant()) {
+      __ StoreObject(FieldAddress(instance_reg, field().Offset()),
+                     locs()->in(1).constant());
+    } else {
+      Register value_reg = locs()->in(1).reg();
+      __ StoreIntoObjectNoBarrier(instance_reg,
+          FieldAddress(instance_reg, field().Offset()), value_reg);
+    }
   }
 }
 
 
 LocationSummary* LoadStaticFieldInstr::MakeLocationSummary() const {
   return LocationSummary::Make(0,
                                Location::RequiresRegister(),
                                LocationSummary::kNoCall);
 }
 
@@ skipping 1286 matching lines @@
     __ j(ABOVE_EQUAL, deopt);
   }
 }
 
 
 }  // namespace dart
 
 #undef __
 
 #endif  // defined TARGET_ARCH_X64