Add a value range analysis phase to remove bounds checks.

lib/compiler/implementation/ssa/codegen.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.
 
 class SsaCodeGeneratorTask extends CompilerTask {
 
   final JavaScriptBackend backend;
 
   SsaCodeGeneratorTask(JavaScriptBackend backend)
       : this.backend = backend,
@@ skipping 1898 matching lines @@
 
   visitThrow(HThrow node) {
     if (node.isRethrow) {
       use(node.inputs[0]);
       pushStatement(new js.Throw(pop()), node);
     } else {
       generateThrowWithHelper(r'$throw', node.inputs[0]);
     }
   }
 
+  visitRangeConversion(HRangeConversion node) {
+    // Range conversion instructions are removed by the value range
+    // analyzer.
+    assert(false);
+  }
+
   visitBoundsCheck(HBoundsCheck node) {
     // TODO(ngeoffray): Separate the two checks of the bounds check, so,
     // e.g., the zero checks can be shared if possible.
 
     // If the checks always succeeds, we would have removed the bounds check
     // completely.
     assert(node.staticChecks != HBoundsCheck.ALWAYS_TRUE);
     if (node.staticChecks != HBoundsCheck.ALWAYS_FALSE) {
-      js.Binary under;
+      js.Expression under;
+      js.Expression over;
       if (node.staticChecks != HBoundsCheck.ALWAYS_ABOVE_ZERO) {
-        assert(node.staticChecks == HBoundsCheck.FULL_CHECK);
         use(node.index);
         under = new js.Binary("<", pop(), new js.LiteralNumber("0"));
       }
-      use(node.index);
-      js.Expression index = pop();
-      use(node.length);
-      js.Binary over = new js.Binary(">=", index, pop());
-      js.Binary underOver =
-          under == null ? over : new js.Binary("||", under, over);
+      if (node.staticChecks != HBoundsCheck.ALWAYS_BELOW_LENGTH) {
+        var index = node.index;
+        use(index);
+        js.Expression jsIndex = pop();
+        use(node.length);
+        over = new js.Binary(">=", jsIndex, pop());
+      }
+      assert(over != null || under != null);
+      js.Expression underOver = under == null
+          ? over
+          : over == null
+              ? under
+              : new js.Binary("||", under, over);
       js.Statement thenBody = new js.Block.empty();
       js.Block oldContainer = currentContainer;
       currentContainer = thenBody;
       generateThrowWithHelper('ioore', node.index);
       currentContainer = oldContainer;
       thenBody = unwrapStatement(thenBody);
       pushStatement(new js.If.noElse(underOver, thenBody), node);
     } else {
       generateThrowWithHelper('ioore', node.index);
     }
@@ skipping 1046 matching lines @@
   if (leftType.canBeNull() && rightType.canBeNull()) {
     if (left.isConstantNull() || right.isConstantNull() ||
         (leftType.isPrimitive() && leftType == rightType)) {
       return '==';
     }
     return null;
   } else {
     return '===';
   }
 }