hphp/runtime/vm/jit/align-internal-inl.h

   1 /*
   2    +----------------------------------------------------------------------+
   3    | HipHop for PHP                                                       |
   4    +----------------------------------------------------------------------+
   5    | Copyright (c) 2010-2016 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 #include "hphp/runtime/vm/jit/mc-generator.h"
  18
  19 #include "hphp/util/data-block.h"
  20
  21 #include <folly/Bits.h>
  22 #include <utility>
  23
  24 namespace HPHP { namespace jit {
  25
  26 ///////////////////////////////////////////////////////////////////////////////
  27
  28 namespace {
  29
  30 ///////////////////////////////////////////////////////////////////////////////
  31
  32 bool is_aligned(TCA frontier, const AlignInfo& a) {
  33   assertx(a.nbytes <= a.align);
  34   assertx(folly::isPowTwo(a.align));
  35
  36   auto const mask = a.align - 1;
  37
  38   auto const ifrontier = reinterpret_cast<size_t>(frontier);
  39   auto const first_byte = ifrontier + a.offset;
  40   auto const last_byte  = ifrontier + a.nbytes - 1;
  41
  42   return (first_byte & ~mask) == (last_byte & ~mask);
  43 }
  44
  45 size_t align_gap(TCA frontier, const AlignInfo& a) {
  46   auto const ifrontier = reinterpret_cast<size_t>(frontier);
  47   auto const gap = a.align - ((a.align - 1) & (ifrontier + a.offset));
  48
  49   return gap == a.align ? 0 : gap;
  50 }
  51
  52 ///////////////////////////////////////////////////////////////////////////////
  53
  54 }
  55
  56 ///////////////////////////////////////////////////////////////////////////////
  57
  58 template <class AImpl>
  59 bool is_aligned(TCA frontier, Alignment alignment) {
  60   auto const idx = static_cast<uint32_t>(alignment);
  61   bool const is_jccandjmp = alignment == Alignment::SmashJccAndJmp;
  62
  63   return is_aligned(frontier, AImpl::s_table[idx]) &&
  64     (!is_jccandjmp || is_aligned(frontier, AImpl::s_table[idx + 1]));
  65 }
  66
  67 template <class AImpl>
  68 void align(CodeBlock& cb, CGMeta* meta,
  69            Alignment alignment, AlignContext context) {
  70   auto const idx = static_cast<uint32_t>(alignment);
  71   bool const is_jccandjmp = alignment == Alignment::SmashJccAndJmp;
  72
  73   auto const pad_for_align = [&] (const AlignInfo& ali) {
  74     if (is_aligned(cb.frontier(), ali)) return;
  75     AImpl::pad(cb, context, align_gap(cb.frontier(), ali));
  76   };
  77
  78   pad_for_align(AImpl::s_table[idx]);
  79   if (is_jccandjmp) {
  80     pad_for_align(AImpl::s_table[idx + 1]);
  81   }
  82
  83   assertx(is_aligned(cb.frontier(), AImpl::s_table[idx]));
  84   assertx(IMPLIES(is_jccandjmp,
  85                   is_aligned(cb.frontier(), AImpl::s_table[idx + 1])));
  86
  87   if (meta) {
  88     meta->alignments.emplace(
  89       cb.frontier(),
  90       std::make_pair(alignment, context)
  91     );
  92   }
  93 }
  94
  95 ///////////////////////////////////////////////////////////////////////////////
  96
  97 }}