hphp/runtime/vm/jit/align-arm.cpp

   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 #include "hphp/runtime/vm/jit/align-arm.h"
  18
  19 #include "hphp/runtime/vm/jit/align-internal.h"
  20 #include "hphp/runtime/vm/jit/smashable-instr-arm.h"
  21
  22 #include "hphp/util/data-block.h"
  23 #include "hphp/vixl/a64/macro-assembler-a64.h"
  24
  25 #include <folly/Bits.h>
  26
  27 #include <utility>
  28
  29 namespace HPHP { namespace jit { namespace arm {
  30
  31 ///////////////////////////////////////////////////////////////////////////////
  32
  33 namespace {
  34
  35 /*
  36  * Targets of jmps on arm must be aligned to instruction size
  37  */
  38 constexpr size_t kJmpTargetAlign = vixl::kInstructionSize;
  39
  40 struct AlignImpl {
  41   static DECLARE_ALIGN_TABLE(s_table);
  42
  43   static void pad(CodeBlock& cb, AlignContext context, size_t bytes) {
  44     vixl::MacroAssembler a { cb };
  45     auto const begin = cb.frontier();
  46
  47     switch (context) {
  48       case AlignContext::Live: {
  49         assertx(((bytes & 3) == 0) && "alignment must be multiple of 4");
  50         for (; bytes > 0; bytes -= 4) {
  51           a.Nop();
  52         }
  53         cb.sync(begin);
  54         return;
  55       }
  56       case AlignContext::Dead: {
  57         if (bytes > 4) {
  58           a.Brk();
  59           bytes -= 4;
  60         }
  61         cb.sync(begin);
  62         if (bytes > 0) pad(cb, AlignContext::Live, bytes);
  63         return;
  64       }
  65     }
  66     not_reached();
  67   }
  68 };
  69
  70 DEFINE_ALIGN_TABLE(AlignImpl::s_table);
  71
  72 }
  73
  74 ///////////////////////////////////////////////////////////////////////////////
  75
  76 bool is_aligned(TCA frontier, Alignment alignment) {
  77   return jit::is_aligned<AlignImpl>(frontier, alignment);
  78 }
  79
  80 void align(CodeBlock& cb, CGMeta* meta,
  81            Alignment alignment, AlignContext context) {
  82   return jit::align<AlignImpl>(cb, meta, alignment, context);
  83 }
  84
  85 ///////////////////////////////////////////////////////////////////////////////
  86
  87 }}}