hphp/runtime/vm/minstr-state.h

   1 /*
   2    +----------------------------------------------------------------------+
   3    | HipHop for PHP                                                       |
   4    +----------------------------------------------------------------------+
   5    | Copyright (c) 2010-present 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
  17 #ifndef incl_HPHP_RUNTIME_VM_MINSTR_STATE_H_
  18 #define incl_HPHP_RUNTIME_VM_MINSTR_STATE_H_
  19
  20 #include "hphp/runtime/base/tv-val.h"
  21 #include "hphp/runtime/base/typed-value.h"
  22
  23 namespace HPHP {
  24
  25 /*
  26  * Member instruction property state. If we're checking property type-hints,
  27  * this indicates whether the current base is a property. This is needed so we
  28  * can forbid the base promoting to a type which isn't allowed by the
  29  * type-hint. This state is only live in situations where we have not proven
  30  * that promotion cannot happen.
  31  *
  32  * We use the lower bit of the Class* to store whether this property is static
  33  * or not. Furthermore, in LOWPTR builds we can pack everything into 64-bits,
  34  * which allows for efficient initialization from the TC.
  35  */
  36 struct MInstrPropState {
  37   MInstrPropState(): m_cls{0} {}
  38   MInstrPropState(const Class* cls, Slot slot, bool isStatic)
  39     : m_cls{
  40        static_cast<decltype(m_cls)>(
  41          reinterpret_cast<uintptr_t>(cls) | (isStatic ? 0x1 : 0x0)
  42        )
  43       }
  44     , m_slot{slot}
  45     {}
  46
  47   const Class* getClass() const {
  48     return reinterpret_cast<const Class*>(
  49       m_cls & ~static_cast<decltype(m_cls)>(0x1)
  50     );
  51   }
  52   Slot getSlot() const { return m_slot; }
  53   bool isStatic() const { return m_cls & 0x1; }
  54
  55   static constexpr ptrdiff_t slotOff() {
  56     return offsetof(MInstrPropState, m_slot);
  57   }
  58   static constexpr ptrdiff_t clsOff() {
  59     return offsetof(MInstrPropState, m_cls);
  60   }
  61
  62   static constexpr size_t slotSize() {
  63     return sizeof(m_slot);
  64   }
  65   static constexpr size_t clsSize() {
  66     return sizeof(m_cls);
  67   }
  68 private:
  69   LowPtr<const Class>::storage_type m_cls;
  70   Slot m_slot;
  71 };
  72
  73 /*
  74  * MInstrState contains VM registers used while executing member instructions.
  75  * It lives with the other VM registers in the RDS header, and is also saved and
  76  * restored with them when we reenter the VM.
  77  */
  78 struct MInstrState {
  79
  80   /*
  81    * This space is used for the return value of builtin functions that return by
  82    * reference, and for storing $this as the base for the BaseH bytecode,
  83    * without needing to acquire a reference to it.  Since we don't ever use the
  84    * two at the same time, it is okay to use a union.
  85    */
  86   union {
  87     TypedValue tvBuiltinReturn;
  88     TypedValue tvTempBase;
  89   };
  90
  91   // The JIT passes &tvBuiltinReturn::m_data to builtins returning
  92   // Array/Object/String, which perform RVO in C++, thus writing valid
  93   // pointers without updating m_type, preventing the GC from scanning
  94   // the pointer. But conservative scanning doesn't really hurt here
  95   // (given that the pointer is also passed into a C++ function), and
  96   // it allows us to keep rds::Header below 128 bytes.
  97   TYPE_SCAN_CONSERVATIVE_FIELD(tvBuiltinReturn);
  98
  99   TypedValue tvRef;
 100   TypedValue tvRef2;
 101   tv_lval base;
 102
 103   // type-scan driven scanner
 104   TYPE_SCAN_IGNORE_FIELD(base);
 105
 106   MInstrPropState propState;
 107 };
 108
 109 }
 110
 111 #endif