hphp/runtime/vm/instance-bits.h

   1 /*
   2    +----------------------------------------------------------------------+
   3    | HipHop for PHP                                                       |
   4    +----------------------------------------------------------------------+
   5    | Copyright (c) 2010-2014 Facebook, Inc. (http://www.facebook.com)     |
   6    +----------------------------------------------------------------------+
   7    | This source file is subject to version 3.01 of the PHP license,      |
   8    | that is bundled with this package in the file LICENSE, and is        |
   9    | available through the world-wide-web at the following url:           |
  10    | http://www.php.net/license/3_01.txt                                  |
  11    | If you did not receive a copy of the PHP license and are unable to   |
  12    | obtain it through the world-wide-web, please send a note to          |
  13    | license@php.net so we can mail you a copy immediately.               |
  14    +----------------------------------------------------------------------+
  15 */
  16 #ifndef incl_HPHP_RUNTIME_VM_INSTANCE_BITS_H_
  17 #define incl_HPHP_RUNTIME_VM_INSTANCE_BITS_H_
  18
  19 #include <bitset>
  20 #include <atomic>
  21 #include <cinttypes>
  22
  23 #include "hphp/util/mutex.h"
  24
  25 namespace HPHP { struct StringData; }
  26
  27 //////////////////////////////////////////////////////////////////////
  28
  29 /*
  30  * During warmup, we profile the most common classes or interfaces
  31  * involved in instanceof checks in order to set up a bitmask for each
  32  * class to allow these checks to be performed quickly by the JIT.
  33  */
  34 namespace HPHP { namespace InstanceBits {
  35
  36 //////////////////////////////////////////////////////////////////////
  37
  38 typedef std::bitset<128> BitSet;
  39
  40 /*
  41  * The initFlag tracks whether init() has finished yet.
  42  *
  43  * The lock is used to protect access to the instance bits on
  44  * individual classes to ensure that after the initFlag -> true
  45  * transition, all loaded classes will properly have instance bits
  46  * populated.
  47  *
  48  * See Unit::defClass for some details.
  49  */
  50 extern ReadWriteMutex lock;
  51 extern std::atomic<bool> initFlag;
  52
  53 /*
  54  * Called to record an instanceof check for `name', during the warmup
  55  * phase.
  56  */
  57 void profile(const StringData* name);
  58
  59 /*
  60  * InstanceBits::init() must be called by the first translation which
  61  * uses instance bits, while holding the write lease.
  62  */
  63 void init();
  64
  65 /*
  66  * Returns: the instance bit for the class or interface `name', or
  67  * zero if there is no allocated bit.
  68  *
  69  * This function may be called by the thread doing init(), or
  70  * otherwise only after init() is finished (i.e. initFlag == true).
  71  */
  72 unsigned lookup(const StringData* name);
  73
  74 /*
  75  * Populate a mask and offset for checking instance bits from JIT
  76  * compiled code.  The offset is the offset of the byte that should be
  77  * tested with mask, relative to a Class*.
  78  *
  79  * Returns false if `name' has no instance bit.
  80  *
  81  * Pre: initFlag == true.
  82  */
  83 bool getMask(const StringData* name, int& offset, uint8_t& mask);
  84
  85 //////////////////////////////////////////////////////////////////////
  86
  87 }}
  88
  89 #endif