Support use of external strings as inputs to LoadCodeUnitsInstr.

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 871 matching lines @@
                                                         bool opt) const {
   const intptr_t kNumInputs = 1;
   return LocationSummary::Make(isolate,
                                kNumInputs,
                                Location::RequiresRegister(),
                                LocationSummary::kNoCall);
 }
 
 
 void LoadUntaggedInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
-  Register object = locs()->in(0).reg();
+  Register obj = locs()->in(0).reg();
   Register result = locs()->out(0).reg();
-  __ movq(result, FieldAddress(object, offset()));
+  if (object()->definition()->representation() == kUntagged) {
+    __ movq(result, Address(obj, offset()));
+  } else {
+    ASSERT(object()->definition()->representation() == kTagged);
+    __ movq(result, FieldAddress(obj, offset()));
+  }
 }
 
 
 LocationSummary* LoadClassIdInstr::MakeLocationSummary(Isolate* isolate,
                                                        bool opt) const {
   const intptr_t kNumInputs = 1;
   return LocationSummary::Make(isolate,
                                kNumInputs,
                                Location::RequiresRegister(),
                                LocationSummary::kNoCall);
@@ skipping 236 matching lines @@
   // The smi index is either untagged (element size == 1), or it is left smi
   // tagged (for all element sizes > 1).
   summary->set_in(1, index_scale() == 1 ? Location::WritableRegister()
                                         : 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 = Assembler::ElementAddressForRegIndex(
-        IsExternal(), class_id(), index_scale(), array, index.reg());
+        IsExternal(), class_id(), index_scale(), str, index.reg());
 
   if ((index_scale() == 1)) {
     __ SmiUntag(index.reg());
   }
   Register result = locs()->out(0).reg();
   switch (class_id()) {
     case kOneByteStringCid:
     case kExternalOneByteStringCid:
       switch (element_count()) {
         case 1: __ movzxb(result, element_address); break;
@@ skipping 5218 matching lines @@
   __ movq(R10, Immediate(kInvalidObjectPointer));
   __ movq(RBX, Immediate(kInvalidObjectPointer));
 #endif
 }
 
 }  // namespace dart
 
 #undef __
 
 #endif  // defined TARGET_ARCH_X64