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

runtime/vm/intermediate_language_x64.cc

Index: runtime/vm/intermediate_language_x64.cc
diff --git a/runtime/vm/intermediate_language_x64.cc b/runtime/vm/intermediate_language_x64.cc
index 87b1f2e0afad0283a9eebc1747b87cada9cf8356..28159eda0f537d6485092d0c8a9f1a78f87da0ce 100644
--- a/runtime/vm/intermediate_language_x64.cc
+++ b/runtime/vm/intermediate_language_x64.cc
@@ -812,8 +812,8 @@ static bool CanBeImmediateIndex(Value* index, intptr_t cid) {
 }
 
 
-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,
@@ -823,7 +823,8 @@ LocationSummary* StringFromCharCodeInstr::MakeLocationSummary(Zone* zone,
 }
 
 
-void StringFromCharCodeInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
+void OneByteStringFromCharCodeInstr::EmitNativeCode(
+    FlowGraphCompiler* compiler) {
   ASSERT(compiler->is_optimizing());
   Register char_code = locs()->in(0).reg();
   Register result = locs()->out(0).reg();
@@ -973,6 +974,8 @@ CompileType LoadIndexedInstr::ComputeType() const {
     case kTypedDataUint16ArrayCid:
     case kOneByteStringCid:
     case kTwoByteStringCid:
+    case kExternalOneByteStringCid:
+    case kExternalTwoByteStringCid:
     case kTypedDataInt32ArrayCid:
     case kTypedDataUint32ArrayCid:
       return CompileType::FromCid(kSmiCid);
@@ -1000,6 +1003,8 @@ Representation LoadIndexedInstr::representation() const {
     case kTypedDataUint16ArrayCid:
     case kOneByteStringCid:
     case kTwoByteStringCid:
+    case kExternalOneByteStringCid:
+    case kExternalTwoByteStringCid:
       return kTagged;
     case kTypedDataInt32ArrayCid:
       return kUnboxedInt32;
@@ -1135,6 +1140,7 @@ void LoadIndexedInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
     case kExternalTypedDataUint8ArrayCid:
     case kExternalTypedDataUint8ClampedArrayCid:
     case kOneByteStringCid:
+    case kExternalOneByteStringCid:
       __ movzxb(result, element_address);
       __ SmiTag(result);
       break;
@@ -1144,6 +1150,7 @@ void LoadIndexedInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
       break;
     case kTypedDataUint16ArrayCid:
     case kTwoByteStringCid:
+    case kExternalTwoByteStringCid:
       __ movzxw(result, element_address);
       __ SmiTag(result);
       break;