Clean up code to clarify we are only tracking the condition flags of APSR.

src/trusted/validator_arm/model.h

 /*
  * Copyright (c) 2012 The Native Client Authors. All rights reserved.
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef NATIVE_CLIENT_SRC_TRUSTED_VALIDATOR_ARM_V2_MODEL_H
 #define NATIVE_CLIENT_SRC_TRUSTED_VALIDATOR_ARM_V2_MODEL_H
 
 /*
@@ skipping 62 matching lines @@
 /*
  * A special value used in some cases to indicate that a register field
  * is not used.  This is specially chosen to ensure that bitmask() == 0, so
  * it can be added to any RegisterList with no effect.
  *
  * Note that -1 or 32 can't be used here because C++ doesn't define a portable
  * meaning for such shift distances.
  */
 const Register kRegisterNone(31);
 
-// The APSR (flags register) is modeled as r16.
-const Register kRegisterFlags(16);
+// The conditions (i.e. APSR N, Z, C, and V) are collectively modeled as r16.
+// These bits of the APSR register are separately tracked, so we can
+// test when any of the 4 bits (and hence conditional execution) is
+// affected. If you need to track other bits in the APSR, add them as
+// a separate register.
+const Register kConditions(16);
 
 // Registers with special meaning in our model:
 const Register kRegisterPc(15);
 const Register kRegisterLink(14);
 const Register kRegisterStack(13);
 
-
 /*
  * A collection of Registers.  Used to describe the side effects of operations.
  *
  * Note that this is technically a set, not a list -- but RegisterSet is a
  * well-known term that means something else.
  */
 class RegisterList {
  public:
   /*
    * Produces a RegisterList that contains the registers specified in the
@@ skipping 212 matching lines @@
  private:
   uint32_t bits_;
 };
 
 }  // namespace
 
 // Definitions for our inlined functions.
 #include "native_client/src/trusted/validator_arm/model-inl.h"
 
 #endif  // NATIVE_CLIENT_SRC_TRUSTED_VALIDATOR_ARM_V2_MODEL_H