Support use of external strings as inputs to LoadCodeUnitsInstr.

runtime/vm/intermediate_language_arm64.cc

 // Copyright (c) 2014, 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_ARM64.
 #if defined(TARGET_ARCH_ARM64)
 
 #include "vm/intermediate_language.h"
 
 #include "vm/dart_entry.h"
@@ skipping 885 matching lines @@
                                                         bool opt) const {
   const intptr_t kNumInputs = 1;
   return LocationSummary::Make(isolate,
                                kNumInputs,
                                Location::RequiresRegister(),
                                LocationSummary::kNoCall);
 }
 
 
 void LoadUntaggedInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
-  const Register object = locs()->in(0).reg();
+  const Register obj = locs()->in(0).reg();
   const Register result = locs()->out(0).reg();
-  __ LoadFieldFromOffset(result, object, offset(), PP);
+  if (object()->definition()->representation() == kUntagged) {
+    __ LoadFromOffset(result, obj, offset(), PP);
+  } else {
+    ASSERT(object()->definition()->representation() == kTagged);
+    __ LoadFieldFromOffset(result, obj, offset(), PP);
+  }
 }
 
 
 LocationSummary* LoadClassIdInstr::MakeLocationSummary(Isolate* isolate,
                                                        bool opt) const {
   const intptr_t kNumInputs = 1;
   return LocationSummary::Make(isolate,
                                kNumInputs,
                                Location::RequiresRegister(),
                                LocationSummary::kNoCall);
@@ skipping 223 matching lines @@
   LocationSummary* summary = new(isolate) LocationSummary(
       isolate, kNumInputs, kNumTemps, LocationSummary::kNoCall);
   summary->set_in(0, Location::RequiresRegister());
   summary->set_in(1, Location::RequiresRegister());
   summary->set_out(0, Location::RequiresRegister());
   return summary;
 }
 
 
 void LoadCodeUnitsInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
-  const Register array = locs()->in(0).reg();
+  // The string register points to the backing store for external strings.
+  const Register str = locs()->in(0).reg();
   const Location index = locs()->in(1);
 
   Address element_address = __ ElementAddressForRegIndex(
-        true,  IsExternal(), class_id(), index_scale(), array, index.reg());
+        true,  IsExternal(), class_id(), index_scale(), str, index.reg());
   // Warning: element_address may use register TMP as base.
 
   Register result = locs()->out(0).reg();
   switch (class_id()) {
     case kOneByteStringCid:
     case kExternalOneByteStringCid:
       switch (element_count()) {
         case 1: __ ldr(result, element_address, kUnsignedByte); break;
         case 2: __ ldr(result, element_address, kUnsignedHalfword); break;
         case 4: __ ldr(result, element_address, kUnsignedWord); break;
@@ skipping 4418 matching lines @@
   compiler->GenerateCall(token_pos(), &label, stub_kind_, locs());
 #if defined(DEBUG)
   __ LoadImmediate(R4, kInvalidObjectPointer, kNoPP);
   __ LoadImmediate(R5, kInvalidObjectPointer, kNoPP);
 #endif
 }
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_ARM64