Address review comments from https://chromiumcodereview.appspot.com/10454049/.

lib/compiler/implementation/ssa/validate.dart

 // Copyright (c) 2011, 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 HValidator extends HInstructionVisitor {
   bool isValid = true;
   HGraph graph;
 
   void visitGraph(HGraph visitee) {
     graph = visitee;
@@ skipping 65 matching lines @@
       }
       if (dominated.id === null || dominated.id <= lastId) {
         markInvalid("dominated.id === null or dominated has <= id");
       }
       lastId = dominated.id;
     }
 
     if (!isValid) return;
     block.forEachPhi(visitInstruction);
 
-    // Make sure the parameters of a phi are dominating the
-    // corresponding predecessor block.
+    // Make sure the blocks of the parameters of a phi are dominating the

[Lasse Reichstein Nielsen, 2012/05/31 07:11:58]

Pedantry: "Make sure" -> "Check that". If you "make sure", you are willing to
change something to make it so. If you merely check it, the check can fail.
Ditto below.

[ngeoffray, 2012/05/31 08:16:16]

Done.

+    // corresponding predecessor block. Note that block dominates

[Lasse Reichstein Nielsen, 2012/05/31 07:11:58]

"block dominates" -> "blocks dominate" (or "a block dominates itself").

[ngeoffray, 2012/05/31 08:16:16]

Done.

+    // themselves.
     block.forEachPhi((HPhi phi) {
       for (int i = 0; i < phi.inputs.length; i++) {
         HInstruction input = phi.inputs[i];
         if (!input.block.dominates(block.predecessors[i])) {
           markInvalid("Definition does not dominate use");
         }
       }
     });
 
-    // Make sure the inputs of an instruction dominate the
-    // instruction.
+    // Make sure the blocks of the inputs of an instruction dominate the
+    // instruction's block.
     block.forEachInstruction((HInstruction instruction) {
       for (HInstruction input in instruction.inputs) {
         if (!input.block.dominates(block)) {
           markInvalid("Definition does not dominate use");
         }
       }
     });
 
     super.visitBasicBlock(block);
   }
@@ skipping 57 matching lines @@
       markInvalid("Instruction in wrong block");
     }
     if (!hasCorrectInputs()) {
       markInvalid("Incorrect inputs");
     }
     if (!hasCorrectUses()) {
       markInvalid("Incorrect uses");
     }
   }
 }