VM: Fix double comparisons using != and NaN in optimized code.

runtime/vm/flow_graph_compiler_arm.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_ARM.
 #if defined(TARGET_ARCH_ARM)
 
 #include "vm/flow_graph_compiler.h"
 
 #include "vm/ast_printer.h"
@@ skipping 1607 matching lines @@
 void FlowGraphCompiler::EmitDoubleCompareBool(Condition true_condition,
                                               FpuRegister left,
                                               FpuRegister right,
                                               Register result) {
   DRegister dleft = EvenDRegisterOf(left);
   DRegister dright = EvenDRegisterOf(right);
   assembler()->vcmpd(dleft, dright);
   assembler()->vmstat();
   assembler()->LoadObject(result, Bool::False());
   Label done;
-  assembler()->b(&done, VS);  // NaN -> false.
+  if (true_condition != NE) {
+    assembler()->b(&done, VS);  // x == NaN -> false, x != NaN -> true.
+  }
   assembler()->LoadObject(result, Bool::True(), true_condition);
   assembler()->Bind(&done);
 }
 
 
 // Do not implement or use this function.
 FieldAddress FlowGraphCompiler::ElementAddressForIntIndex(intptr_t cid,
                                                           intptr_t index_scale,
                                                           Register array,
                                                           intptr_t index) {
@@ skipping 266 matching lines @@
   DRegister dreg = EvenDRegisterOf(reg);
   __ vldrd(dreg, Address(SP, kDoubleSize, Address::PostIndex));
 }
 
 
 #undef __
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_ARM