dfg/DFGCorrectableJumpPoint.h

   1 /*
   2  * Copyright (C) 2011 Apple Inc. All rights reserved.
   3  *
   4  * Redistribution and use in source and binary forms, with or without
   5  * modification, are permitted provided that the following conditions
   6  * are met:
   7  * 1. Redistributions of source code must retain the above copyright
   8  *    notice, this list of conditions and the following disclaimer.
   9  * 2. Redistributions in binary form must reproduce the above copyright
  10  *    notice, this list of conditions and the following disclaimer in the
  11  *    documentation and/or other materials provided with the distribution.
  12  *
  13  * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
  14  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  15  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  16  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE INC. OR
  17  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
  18  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
  19  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
  20  * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
  21  * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  22  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  23  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  24  */
  25
  26 #ifndef DFGCorrectableJumpPoint_h
  27 #define DFGCorrectableJumpPoint_h
  28
  29 #if ENABLE(DFG_JIT)
  30
  31 #include "LinkBuffer.h"
  32 #include "MacroAssembler.h"
  33
  34 namespace JSC { namespace DFG {
  35
  36 // This is a type-safe union of MacroAssembler::Jump and CodeLocationJump.
  37 // Furthermore, it supports the notion of branching (possibly conditionally, but
  38 // also possibly jumping unconditionally) to an out-of-line patchable jump.
  39 // Thus it goes through three states:
  40 //
  41 // 1) Label of unpatchable branch or jump (i.e. MacroAssembler::Jump).
  42 // 2) Label of patchable jump (i.e. MacroAssembler::PatchableJump).
  43 // 3) Corrected post-linking label of patchable jump (i.e. CodeLocationJump).
  44 //
  45 // The setting of state (1) corresponds to planting the in-line unpatchable
  46 // branch or jump. The state transition (1)->(2) corresponds to linking the
  47 // in-line branch or jump to the out-of-line patchable jump, and recording
  48 // the latter's label. The state transition (2)->(3) corresponds to recording
  49 // the out-of-line patchable jump's location after branch compaction has
  50 // completed.
  51 //
  52 // You can also go directly from the first state to the third state, if you
  53 // wish to use this class for in-line patchable jumps.
  54
  55 class CorrectableJumpPoint {
  56 public:
  57     CorrectableJumpPoint(MacroAssembler::Jump check)
  58         : m_codeOffset(check.m_label.m_offset)
  59 #ifndef NDEBUG
  60         , m_mode(InitialJump)
  61 #endif
  62     {
  63 #if CPU(ARM_THUMB2)
  64         m_type = check.m_type;
  65         m_condition = check.m_condition;
  66 #endif
  67     }
  68
  69     void switchToLateJump(MacroAssembler::PatchableJump check)
  70     {
  71 #ifndef NDEBUG
  72         ASSERT(m_mode == InitialJump);
  73         m_mode = LateJump;
  74 #endif
  75         // Late jumps should only ever be real jumps.
  76 #if CPU(ARM_THUMB2)
  77         ASSERT(check.m_jump.m_type == ARMv7Assembler::JumpNoConditionFixedSize);
  78         ASSERT(check.m_jump.m_condition == ARMv7Assembler::ConditionInvalid);
  79         m_type = ARMv7Assembler::JumpNoConditionFixedSize;
  80         m_condition = ARMv7Assembler::ConditionInvalid;
  81 #endif
  82         m_codeOffset = check.m_jump.m_label.m_offset;
  83     }
  84
  85     void correctInitialJump(LinkBuffer& linkBuffer)
  86     {
  87         ASSERT(m_mode == InitialJump);
  88 #if CPU(ARM_THUMB2)
  89         ASSERT(m_type == ARMv7Assembler::JumpNoConditionFixedSize);
  90         ASSERT(m_condition == ARMv7Assembler::ConditionInvalid);
  91 #endif
  92         correctJump(linkBuffer);
  93     }
  94
  95     void correctLateJump(LinkBuffer& linkBuffer)
  96     {
  97         ASSERT(m_mode == LateJump);
  98         correctJump(linkBuffer);
  99     }
 100
 101     MacroAssembler::Jump initialJump() const
 102     {
 103         ASSERT(m_mode == InitialJump);
 104         return getJump();
 105     }
 106
 107     MacroAssembler::Jump lateJump() const
 108     {
 109         ASSERT(m_mode == LateJump);
 110         return getJump();
 111     }
 112
 113     CodeLocationJump codeLocationForRepatch(CodeBlock*) const;
 114
 115 private:
 116     void correctJump(LinkBuffer& linkBuffer)
 117     {
 118 #ifndef NDEBUG
 119         m_mode = CorrectedJump;
 120 #endif
 121         MacroAssembler::Label label;
 122         label.m_label.m_offset = m_codeOffset;
 123         m_codeOffset = linkBuffer.offsetOf(label);
 124     }
 125
 126     MacroAssembler::Jump getJump() const
 127     {
 128         MacroAssembler::Jump jump;
 129         jump.m_label.m_offset = m_codeOffset;
 130 #if CPU(ARM_THUMB2)
 131         jump.m_type = m_type;
 132         jump.m_condition = m_condition;
 133 #endif
 134         return jump;
 135     }
 136
 137     unsigned m_codeOffset;
 138
 139 #if CPU(ARM_THUMB2)
 140     ARMv7Assembler::JumpType m_type : 8;
 141     ARMv7Assembler::Condition m_condition : 8;
 142 #endif
 143
 144 #ifndef NDEBUG
 145     enum Mode {
 146         InitialJump,
 147         LateJump,
 148         CorrectedJump
 149     };
 150
 151     Mode m_mode;
 152 #endif
 153 };
 154
 155 } } // namespace JSC::DFG
 156
 157 #endif // ENABLE(DFG_JIT)
 158
 159 #endif // DFGCorrectableJumpPoint_h