Inline _OneByteString._setAt. The key knowledge is that _setAt is an internal method that has to be…

runtime/vm/flow_graph_optimizer.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/flow_graph_optimizer.h"
 
 #include "vm/bit_vector.h"
 #include "vm/cha.h"
 #include "vm/flow_graph_builder.h"
 #include "vm/flow_graph_compiler.h"
@@ skipping 1575 matching lines @@
       MethodRecognizer::RecognizeKind(target);
 
   if ((recognized_kind == MethodRecognizer::kStringBaseCodeUnitAt) &&
       (ic_data.NumberOfChecks() == 1) &&
       ((class_ids[0] == kOneByteStringCid) ||
        (class_ids[0] == kTwoByteStringCid))) {
     LoadIndexedInstr* instr = BuildStringCodeUnitAt(call, class_ids[0]);
     ReplaceCall(call, instr);
     return true;
   }
-  if ((recognized_kind == MethodRecognizer::kStringBaseCharAt) &&
-      (ic_data.NumberOfChecks() == 1) &&
-      (class_ids[0] == kOneByteStringCid)) {
-    // TODO(fschneider): Handle TwoByteString.
-    LoadIndexedInstr* load_char_code =
-        BuildStringCodeUnitAt(call, class_ids[0]);
-    InsertBefore(call, load_char_code, NULL, Definition::kValue);
-    StringFromCharCodeInstr* char_at =
-        new StringFromCharCodeInstr(new Value(load_char_code),
-                                    kOneByteStringCid);
-    ReplaceCall(call, char_at);
-    return true;
+  if ((class_ids[0] == kOneByteStringCid) && (ic_data.NumberOfChecks() == 1)) {
+    if (recognized_kind == MethodRecognizer::kStringBaseCharAt) {
+      // TODO(fschneider): Handle TwoByteString.
+      LoadIndexedInstr* load_char_code =
+          BuildStringCodeUnitAt(call, class_ids[0]);
+      InsertBefore(call, load_char_code, NULL, Definition::kValue);
+      StringFromCharCodeInstr* char_at =
+          new StringFromCharCodeInstr(new Value(load_char_code),
+                                      kOneByteStringCid);
+      ReplaceCall(call, char_at);
+      return true;
+    }
+    if (recognized_kind == MethodRecognizer::kOneByteStringSetAt) {
+      // This is an internal method, no need to check argument types nor
+      // range.
+      Definition* str = call->ArgumentAt(0);
+      Definition* index = call->ArgumentAt(1);
+      Definition* value = call->ArgumentAt(2);
+      StoreIndexedInstr* store_op = new StoreIndexedInstr(
+          new Value(str),
+          new Value(index),
+          new Value(value),
+          kNoStoreBarrier,
+          1,  // Index scale
+          kOneByteStringCid,
+          call->deopt_id());
+      ReplaceCall(call, store_op);
+      return true;
+    }
+    return false;
   }
 
   if ((recognized_kind == MethodRecognizer::kIntegerToDouble) &&
       (ic_data.NumberOfChecks() == 1) &&
       (class_ids[0] == kSmiCid)) {
     AddReceiverCheck(call);
     ReplaceCall(call, new SmiToDoubleInstr(new Value(call->ArgumentAt(0))));
     return true;
   }
 
@@ skipping 4509 matching lines @@
 
   // Insert materializations at environment uses.
   const Class& cls = Class::Handle(alloc->constructor().Owner());
   for (intptr_t i = 0; i < exits.length(); i++) {
     CreateMaterializationAt(exits[i], alloc, cls, *fields);
   }
 }
 
 
 }  // namespace dart