Convert some compiler passes to preserve valid def-use chains.

runtime/vm/intermediate_language_ia32.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/globals.h"  // Needed here to get TARGET_ARCH_IA32.
 #if defined(TARGET_ARCH_IA32)
 
 #include "vm/intermediate_language.h"
 
 #include "lib/error.h"
@@ skipping 778 matching lines @@
     compiler->EmitDoubleCompareBool(
         true_condition, left, right, locs.out().reg());
   }
 }
 
 
 void EqualityCompareInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
   ASSERT((kind() == Token::kNE) || (kind() == Token::kEQ));
   BranchInstr* kNoBranch = NULL;
   if (receiver_class_id() == kSmiCid) {
-    // Deoptimizes if both arguments not Smi.
     EmitSmiComparisonOp(compiler, *locs(), kind(), kNoBranch);
     return;
   }
   if (receiver_class_id() == kMintCid) {
     EmitUnboxedMintEqualityOp(compiler, *locs(), kind(), kNoBranch);
     return;
   }
   if (receiver_class_id() == kDoubleCid) {
     EmitDoubleComparisonOp(compiler, *locs(), kind(), kNoBranch);
     return;
@@ skipping 2684 matching lines @@
                          PcDescriptors::kOther,
                          locs());
   __ Drop(2);  // Discard type arguments and receiver.
 }
 
 }  // namespace dart
 
 #undef __
 
 #endif  // defined TARGET_ARCH_IA32