fix a few more codegen issues:

test/codegen/language/optimized_string_charcodeat_test.dart

+// Copyright (c) 2012, 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.
+// VMOptions=--optimization-counter-threshold=10 --no-use-osr
+
+// Test optimized CodeUnitAt and array access.
+
+import "package:expect/expect.dart";
+
+
+String one_byte = "hest";
+String two_byte = "h\u{2029}ns";
+
+int testOneByteCodeUnitAt(String x, int j) {
+  int test() {
+    return x.codeUnitAt(j);
+  }
+  for (int i = 0; i < 20; i++) test();
+  return test();
+}
+
+
+int testTwoByteCodeUnitAt(String x, int j) {
+  int test() {
+    return x.codeUnitAt(j);
+  }
+  for (int i = 0; i < 20; i++) test();
+  return test();
+}
+
+
+int testConstantStringCodeUnitAt(int j) {
+  int test() {
+    return "høns".codeUnitAt(j);
+  }
+  for (int i = 0; i < 20; i++) test();
+  return test();
+}
+
+
+int testConstantIndexCodeUnitAt(String x) {
+  int test() {
+    return x.codeUnitAt(1);
+  }
+  for (int i = 0; i < 20; i++) test();
+  return test();
+}
+
+
+int testOneByteCodeUnitAtInLoop(var x) {
+  var result = 0;
+  for (int i = 0; i < x.length; i++) {
+    result += x.codeUnitAt(i);
+  }
+  return result;
+}
+
+
+int testTwoByteCodeUnitAtInLoop(var x) {
+  var result = 0;
+  for (int i = 0; i < x.length; i++) {
+    result += x.codeUnitAt(i);
+  }
+  return result;
+}
+
+
+main() {
+  for (int j = 0; j < 10; j++) {
+    Expect.equals(101, testOneByteCodeUnitAt(one_byte, 1));
+    Expect.equals(8233, testTwoByteCodeUnitAt(two_byte, 1));
+    Expect.equals(248, testConstantStringCodeUnitAt(1));
+    Expect.equals(101, testConstantIndexCodeUnitAt(one_byte));
+  }
+  for (int j = 0; j < 20; j++) {
+    Expect.equals(436, testOneByteCodeUnitAtInLoop(one_byte));
+    Expect.equals(8562, testTwoByteCodeUnitAtInLoop(two_byte));
+  }
+  Expect.throws(() => testOneByteCodeUnitAtInLoop(123));
+  Expect.throws(() => testTwoByteCodeUnitAtInLoop(123));
+}