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

runtime/vm/intermediate_language_ia32.cc

Index: runtime/vm/intermediate_language_ia32.cc
diff --git a/runtime/vm/intermediate_language_ia32.cc b/runtime/vm/intermediate_language_ia32.cc
index 44d16ed42221b4b70bd647b0788d551903f50d81..5a7d5ce849d43839e38041ff43be8403df119670 100644
--- a/runtime/vm/intermediate_language_ia32.cc
+++ b/runtime/vm/intermediate_language_ia32.cc
@@ -840,8 +840,8 @@ static bool CanBeImmediateIndex(Value* value, 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,
@@ -851,7 +851,8 @@ LocationSummary* StringFromCharCodeInstr::MakeLocationSummary(Zone* zone,
 }
 
 
-void StringFromCharCodeInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
+void OneByteStringFromCharCodeInstr::EmitNativeCode(
+    FlowGraphCompiler* compiler) {
   Register char_code = locs()->in(0).reg();
   Register result = locs()->out(0).reg();
   __ movl(result,
@@ -1000,6 +1001,8 @@ CompileType LoadIndexedInstr::ComputeType() const {
     case kTypedDataUint16ArrayCid:
     case kOneByteStringCid:
     case kTwoByteStringCid:
+    case kExternalOneByteStringCid:
+    case kExternalTwoByteStringCid:
       return CompileType::FromCid(kSmiCid);
 
     case kTypedDataInt32ArrayCid:
@@ -1026,6 +1029,8 @@ Representation LoadIndexedInstr::representation() const {
     case kTypedDataUint16ArrayCid:
     case kOneByteStringCid:
     case kTwoByteStringCid:
+    case kExternalOneByteStringCid:
+    case kExternalTwoByteStringCid:
       return kTagged;
     case kTypedDataInt32ArrayCid:
       return kUnboxedInt32;
@@ -1159,6 +1164,7 @@ void LoadIndexedInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
     case kExternalTypedDataUint8ArrayCid:
     case kExternalTypedDataUint8ClampedArrayCid:
     case kOneByteStringCid:
+    case kExternalOneByteStringCid:
       ASSERT(index_scale() == 1);
       __ movzxb(result, element_address);
       __ SmiTag(result);
@@ -1169,6 +1175,7 @@ void LoadIndexedInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
       break;
     case kTypedDataUint16ArrayCid:
     case kTwoByteStringCid:
+    case kExternalTwoByteStringCid:
       __ movzxw(result, element_address);
       __ SmiTag(result);
       break;