Generate better ARM64 code for indexed loads and stores.

runtime/vm/intermediate_language_arm.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_ARM.
 #if defined(TARGET_ARCH_ARM)
 
 #include "vm/intermediate_language.h"
 
 #include "vm/cpu.h"
@@ skipping 1249 matching lines @@
                                                 offset,
                                                 &offset_mask))) {
     assembler->AddImmediate(base, offset & ~offset_mask);
     offset = offset & offset_mask;
   }
   return Address(base, offset);
 }
 
 
 void LoadIndexedInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
+  // 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(compiler->assembler(),
                                   true,  // Load.
                                   IsExternal(), class_id(), index_scale(),
                                   array, index.reg())
       : ElementAddressForIntIndex(IsExternal(), class_id(), index_scale(),
                                   array, Smi::Cast(index.constant()).Value());
   // Warning: element_address may use register IP as base.
 
   if ((representation() == kUnboxedDouble)    ||
       (representation() == kUnboxedFloat32x4) ||
@@ skipping 43 matching lines @@
         break;
       default:
         UNREACHABLE();
         break;
     }
     return;
   }
 
   ASSERT(representation() == kTagged);
 
-  Register result = locs()->out(0).reg();
+  const Register result = locs()->out(0).reg();
   switch (class_id()) {
     case kTypedDataInt8ArrayCid:
       ASSERT(index_scale() == 1);
       __ ldrsb(result, element_address);
       __ SmiTag(result);
       break;
     case kTypedDataUint8ArrayCid:
     case kTypedDataUint8ClampedArrayCid:
     case kExternalTypedDataUint8ArrayCid:
     case kExternalTypedDataUint8ClampedArrayCid:
@@ skipping 129 matching lines @@
       break;
     default:
       UNREACHABLE();
       return NULL;
   }
   return locs;
 }
 
 
 void StoreIndexedInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
+  // The array register points to the backing store for external arrays.
   const Register array = locs()->in(0).reg();
-  Location index = locs()->in(1);
+  const Location index = locs()->in(1);
 
-  Address element_address(kNoRegister, 0);
-  element_address = index.IsRegister()
-  ? ElementAddressForRegIndex(compiler->assembler(),
-                              false,  // Store.
-                              IsExternal(), class_id(), index_scale(),
-                              array, index.reg())
-  : ElementAddressForIntIndex(IsExternal(), class_id(), index_scale(),
-                              array, Smi::Cast(index.constant()).Value());
+  Address element_address = index.IsRegister()
+      ? ElementAddressForRegIndex(compiler->assembler(),
+                                  false,  // Store.
+                                  IsExternal(), class_id(), index_scale(),
+                                  array, index.reg())
+      : ElementAddressForIntIndex(IsExternal(), class_id(), index_scale(),
+                                  array, Smi::Cast(index.constant()).Value());
 
   switch (class_id()) {
     case kArrayCid:
       if (ShouldEmitStoreBarrier()) {
         const Register value = locs()->in(2).reg();
         __ StoreIntoObject(array, element_address, value);
       } else if (locs()->in(2).IsConstant()) {
         const Object& constant = locs()->in(2).constant();
         __ StoreIntoObjectNoBarrier(array, element_address, constant);
       } else {
@@ skipping 4896 matching lines @@
   compiler->GenerateCall(token_pos(),
                          &label,
                          PcDescriptors::kOther,
                          locs());
   __ Drop(ArgumentCount());  // Discard arguments.
 }
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_ARM