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

runtime/vm/intermediate_language_mips.cc

Index: runtime/vm/intermediate_language_mips.cc
diff --git a/runtime/vm/intermediate_language_mips.cc b/runtime/vm/intermediate_language_mips.cc
index 7bbfb552f7563eb588d89a8ba90245d71e9cb535..b1b078fe991af39f8067f7353af9214aa33abdbc 100644
--- a/runtime/vm/intermediate_language_mips.cc
+++ b/runtime/vm/intermediate_language_mips.cc
@@ -1019,8 +1019,8 @@ 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,
@@ -1030,13 +1030,12 @@ 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();
 
-  __ Comment("StringFromCharCodeInstr");
-
   __ lw(result, Address(THR, Thread::predefined_symbols_address_offset()));
   __ AddImmediate(result, Symbols::kNullCharCodeSymbolOffset * kWordSize);
   __ sll(TMP, char_code, 1);  // Char code is a smi.
@@ -1169,6 +1168,8 @@ CompileType LoadIndexedInstr::ComputeType() const {
     case kTypedDataUint16ArrayCid:
     case kOneByteStringCid:
     case kTwoByteStringCid:
+    case kExternalOneByteStringCid:
+    case kExternalTwoByteStringCid:
       return CompileType::FromCid(kSmiCid);
 
     case kTypedDataInt32ArrayCid:
@@ -1195,6 +1196,8 @@ Representation LoadIndexedInstr::representation() const {
     case kTypedDataUint16ArrayCid:
     case kOneByteStringCid:
     case kTwoByteStringCid:
+    case kExternalOneByteStringCid:
+    case kExternalTwoByteStringCid:
       return kTagged;
     case kTypedDataInt32ArrayCid:
       return kUnboxedInt32;
@@ -1321,6 +1324,7 @@ void LoadIndexedInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
     case kExternalTypedDataUint8ArrayCid:
     case kExternalTypedDataUint8ClampedArrayCid:
     case kOneByteStringCid:
+    case kExternalOneByteStringCid:
       ASSERT(index_scale() == 1);
       __ lbu(result, element_address);
       __ SmiTag(result);
@@ -1331,6 +1335,7 @@ void LoadIndexedInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
       break;
     case kTypedDataUint16ArrayCid:
     case kTwoByteStringCid:
+    case kExternalTwoByteStringCid:
       __ lhu(result, element_address);
       __ SmiTag(result);
       break;