hphp/runtime/vm/jit/alignment.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_JIT_ALIGNMENT_H_
  18 #define incl_HPHP_JIT_ALIGNMENT_H_
  19
  20 #include <cstdint>
  21 #include <string>
  22
  23 namespace HPHP { namespace jit {
  24
  25 ///////////////////////////////////////////////////////////////////////////////
  26
  27 /*
  28  * Whether we're aligning at a live or a dead code point.
  29  *
  30  * Live alignments must use nop gaps; alignment requests in dead contexts are
  31  * allowed to use various trap instructions.
  32  */
  33 enum class AlignContext : uint32_t { Live, Dead };
  34
  35 /*
  36  * What to align to.
  37  *
  38  * Not all of these will actually require alignment on all targets.
  39  */
  40 enum class Alignment : uint32_t {
  41   /*
  42    * Align to the start of the next cache line unconditionally (unless we are
  43    * already aligned to one).
  44    */
  45   CacheLine = 0,
  46
  47   /*
  48    * If we are in the second half of a cache line, align to the next one.
  49    */
  50   CacheLineRoundUp,
  51
  52   /*
  53    * Align to the nearest valid jmp target.
  54    */
  55   JmpTarget,
  56
  57   /*
  58    * Alignments needed by smashable instructions.
  59    */
  60   SmashMovq,
  61   SmashCmpq,
  62   SmashCall,
  63   SmashJmp,
  64   SmashJcc,
  65 };
  66
  67 constexpr auto kNumAlignments =
  68   static_cast<size_t>(Alignment::SmashJcc) + 1;
  69
  70 /*
  71  * Under most architectures, the Alignments can be expressed by stipulating
  72  * that the code region given by
  73  *
  74  *    [frontier + offset, nbytes)
  75  *
  76  * fits into the nearest `align'-aligned and -sized line.
  77  */
  78 struct AlignInfo {
  79   size_t align;
  80   size_t nbytes;
  81   size_t offset;
  82 };
  83
  84 ///////////////////////////////////////////////////////////////////////////////
  85
  86 }}
  87
  88 #endif