Let NaN flow as double into HBranch

src/arm/lithium-arm.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 981 matching lines @@
   HValue* value = instr->value();
   if (value->EmitAtUses()) {
     HBasicBlock* successor = HConstant::cast(value)->BooleanValue()
         ? instr->FirstSuccessor()
         : instr->SecondSuccessor();
     return new(zone()) LGoto(successor->block_id());
   }
 
   LBranch* result = new(zone()) LBranch(UseRegister(value));
   // Tagged values that are not known smis or booleans require a
-  // deoptimization environment.
+  // deoptimization environment. Except in the Generic case.

[Toon Verwaest, 2013/06/20 12:45:59]

If the instruction is generic no environment is needed since all cases are
handled.

   Representation rep = value->representation();
   HType type = value->type();
-  if (rep.IsTagged() && !type.IsSmi() && !type.IsBoolean()) {
+  ToBooleanStub::Types expected = instr->expected_input_types();
+  if (rep.IsTagged() && !type.IsSmi() && !type.IsBoolean() &&
+      !expected.IsGeneric()) {
     return AssignEnvironment(result);
   }
   return result;
 }
 
 
 LInstruction* LChunkBuilder::DoDebugBreak(HDebugBreak* instr) {
   return new(zone()) LDebugBreak();
 }
 
@@ skipping 1635 matching lines @@
 
 
 LInstruction* LChunkBuilder::DoLoadFieldByIndex(HLoadFieldByIndex* instr) {
   LOperand* object = UseRegister(instr->object());
   LOperand* index = UseRegister(instr->index());
   return DefineAsRegister(new(zone()) LLoadFieldByIndex(object, index));
 }
 
 
 } }  // namespace v8::internal