Generate better ARM64 code for indexed loads and stores.

runtime/vm/intermediate_language_x64.cc

 // Copyright (c) 2013, 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 "vm/dart_entry.h"
@@ skipping 1013 matching lines @@
   } else {
     return FieldAddress(array,
                         index,
                         ToScaleFactor(index_scale),
                         Instance::DataOffsetFor(cid));
   }
 }
 
 
 void LoadIndexedInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
-  Register array = locs()->in(0).reg();
-  Location index = locs()->in(1);
+  // The array register points to the backing store for external arrays.
+  const Register array = locs()->in(0).reg();
+  const Location index = locs()->in(1);
 
-  Address element_address(kNoRegister, 0);
-  element_address = index.IsRegister()
+  Address element_address = index.IsRegister()
       ? ElementAddressForRegIndex(IsExternal(), class_id(), index_scale(),
                                   array, index.reg())
       : ElementAddressForIntIndex(IsExternal(), class_id(), index_scale(),
                                   array, Smi::Cast(index.constant()).Value());
 
   if ((representation() == kUnboxedDouble)    ||
       (representation() == kUnboxedFloat32x4) ||
       (representation() == kUnboxedInt32x4)   ||
       (representation() == kUnboxedFloat64x2)) {
     if ((index_scale() == 1) && index.IsRegister()) {
@@ skipping 146 matching lines @@
       break;
     default:
       UNREACHABLE();
       return NULL;
   }
   return locs;
 }
 
 
 void StoreIndexedInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
-  Register array = locs()->in(0).reg();
-  Location index = locs()->in(1);
+  // The array register points to the backing store for external arrays.
+  const Register array = locs()->in(0).reg();
+  const Location index = locs()->in(1);
 
-  Address element_address(kNoRegister, 0);
-  element_address = index.IsRegister()
+  Address element_address = index.IsRegister()
       ? ElementAddressForRegIndex(IsExternal(), class_id(), index_scale(),
                                   array, index.reg())
       : ElementAddressForIntIndex(IsExternal(), class_id(), index_scale(),
                                   array, Smi::Cast(index.constant()).Value());
 
   if ((index_scale() == 1) && index.IsRegister()) {
     __ SmiUntag(index.reg());
   }
   switch (class_id()) {
     case kArrayCid:
@@ skipping 4702 matching lines @@
                          PcDescriptors::kOther,
                          locs());
   __ Drop(ArgumentCount());  // Discard arguments.
 }
 
 }  // namespace dart
 
 #undef __
 
 #endif  // defined TARGET_ARCH_X64