VM: Optimized code for all of [External]{One|Two}ByteString::codeUnitAt.

runtime/vm/intermediate_language_arm.cc

Index: runtime/vm/intermediate_language_arm.cc
diff --git a/runtime/vm/intermediate_language_arm.cc b/runtime/vm/intermediate_language_arm.cc
index 2c7d44ed9e6a507333572190d03199173b24b63e..4123a2a2a46e066e31baa91e8fa0a1c83f55c318 100644
--- a/runtime/vm/intermediate_language_arm.cc
+++ b/runtime/vm/intermediate_language_arm.cc
@@ -968,8 +968,8 @@ void NativeCallInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
 }
 
 
-LocationSummary* StringFromCharCodeInstr::MakeLocationSummary(Zone* zone,
-                                                              bool opt) const {
+LocationSummary* OneByteStringFromCharCodeInstr::MakeLocationSummary(
+    Zone* zone, bool opt) const {
   const intptr_t kNumInputs = 1;
   // TODO(fschneider): Allow immediate operands for the char code.
   return LocationSummary::Make(zone,
@@ -979,7 +979,8 @@ LocationSummary* StringFromCharCodeInstr::MakeLocationSummary(Zone* zone,
 }
 
 
-void StringFromCharCodeInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
+void OneByteStringFromCharCodeInstr::EmitNativeCode(
+    FlowGraphCompiler* compiler) {
   ASSERT(compiler->is_optimizing());
   const Register char_code = locs()->in(0).reg();
   const Register result = locs()->out(0).reg();
@@ -1111,6 +1112,8 @@ CompileType LoadIndexedInstr::ComputeType() const {
     case kTypedDataUint16ArrayCid:
     case kOneByteStringCid:
     case kTwoByteStringCid:
+    case kExternalOneByteStringCid:
+    case kExternalTwoByteStringCid:
       return CompileType::FromCid(kSmiCid);
 
     case kTypedDataInt32ArrayCid:
@@ -1137,6 +1140,8 @@ Representation LoadIndexedInstr::representation() const {
     case kTypedDataUint16ArrayCid:
     case kOneByteStringCid:
     case kTwoByteStringCid:
+    case kExternalOneByteStringCid:
+    case kExternalTwoByteStringCid:
       return kTagged;
     case kTypedDataInt32ArrayCid:
       return kUnboxedInt32;
@@ -1314,6 +1319,7 @@ void LoadIndexedInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
     case kExternalTypedDataUint8ArrayCid:
     case kExternalTypedDataUint8ClampedArrayCid:
     case kOneByteStringCid:
+    case kExternalOneByteStringCid:
       ASSERT(index_scale() == 1);
       __ ldrb(result, element_address);
       __ SmiTag(result);
@@ -1324,6 +1330,7 @@ void LoadIndexedInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
       break;
     case kTypedDataUint16ArrayCid:
     case kTwoByteStringCid:
+    case kExternalTwoByteStringCid:
       __ ldrh(result, element_address);
       __ SmiTag(result);
       break;