[MIPS] Make validator allow only two load patterns via $t8

src/trusted/validator_mips/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_MIPS_MODEL_H
 #define NATIVE_CLIENT_SRC_TRUSTED_VALIDATOR_MIPS_MODEL_H
 
 /*
@@ skipping 24 matching lines @@
 
   /*
    * Produces the bitmask used to represent this register.
    */
   inline uint32_t Bitmask() const;
 
   inline bool Equals(const Register &) const;
 
   static const Number kJumpMask       = 14;  // $t6 = holds mask for jr.
   static const Number kLoadStoreMask  = 15;  // $t7 = holds mask for load/store.
-  static const Number kTls            = 24;  // $t8 = holds tls index.
+  static const Number kTls            = 24;  // $t8 = holds pointer to tp index.

[Mark Seaborn, 2015/12/27 03:46:35]

"tp index" isn't quite right, is it?  Is it an index now?  At least it won't be
when these changes are finished.  Should this be something like "points into
NaClThreadContext"?

[petarj, 2015/12/28 14:07:00]

I have modified it to "holds address of tls_value1 in NaClThreadContext".

[Mark Seaborn, 2015/12/30 02:12:40]

Well, it doesn't hold that address, at least not until your other change,
https://codereview.chromium.org/1536713003/, is committed.

You didn't make it clear what order you want to commit the changes in.  I assume
this change should be committed first -- I think it should work given that you
committed the LLVM-side change (but you still need to run pnacl/deps_update.py
to update pnacl/COMPONENT_REVISIONS).  And then you would commit
https://codereview.chromium.org/1536713003/ after (committing that first
wouldn't be safe, I think).  Have I got that right?

   static const Number kSp             = 29;  // Stack pointer.
 
   static const Number kNone           = 32;
 
   /*
    * A special value used 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.
    */
   static Register None() { return Register(kNone); }
@@ skipping 111 matching lines @@
   uint32_t _bits;
 };
 
 uint32_t const kInstrSize   = 4;
 uint32_t const kInstrAlign  = 0xFFFFFFFC;
 uint32_t const kBundleAlign = 0xFFFFFFF0;
 
 // Opcode for nop instruction.
 uint32_t const kNop = 0x0;
 
-}  // namespace
+}  // namespace nacl_mips_dec
 
 // Definitions for our inlined functions.
 #include "native_client/src/trusted/validator_mips/model-inl.h"
 
 #endif  // NATIVE_CLIENT_SRC_TRUSTED_VALIDATOR_MIPS_MODEL_H