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      1 /*
      2  * Copyright (C) 2011 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 #ifndef ART_RUNTIME_STACK_H_
     18 #define ART_RUNTIME_STACK_H_
     19 
     20 #include <stdint.h>
     21 #include <string>
     22 
     23 #include "arch/instruction_set.h"
     24 #include "base/bit_utils.h"
     25 #include "dex_file.h"
     26 #include "gc_root.h"
     27 #include "mirror/object_reference.h"
     28 #include "read_barrier.h"
     29 #include "verify_object.h"
     30 
     31 namespace art {
     32 
     33 namespace mirror {
     34   class Object;
     35 }  // namespace mirror
     36 
     37 class ArtMethod;
     38 class Context;
     39 class ShadowFrame;
     40 class HandleScope;
     41 class ScopedObjectAccess;
     42 class StackVisitor;
     43 class Thread;
     44 
     45 // The kind of vreg being accessed in calls to Set/GetVReg.
     46 enum VRegKind {
     47   kReferenceVReg,
     48   kIntVReg,
     49   kFloatVReg,
     50   kLongLoVReg,
     51   kLongHiVReg,
     52   kDoubleLoVReg,
     53   kDoubleHiVReg,
     54   kConstant,
     55   kImpreciseConstant,
     56   kUndefined,
     57 };
     58 std::ostream& operator<<(std::ostream& os, const VRegKind& rhs);
     59 
     60 // A reference from the shadow stack to a MirrorType object within the Java heap.
     61 template<class MirrorType>
     62 class MANAGED StackReference : public mirror::CompressedReference<MirrorType> {
     63 };
     64 
     65 // ShadowFrame has 2 possible layouts:
     66 //  - interpreter - separate VRegs and reference arrays. References are in the reference array.
     67 //  - JNI - just VRegs, but where every VReg holds a reference.
     68 class ShadowFrame {
     69  public:
     70   // Compute size of ShadowFrame in bytes assuming it has a reference array.
     71   static size_t ComputeSize(uint32_t num_vregs) {
     72     return sizeof(ShadowFrame) + (sizeof(uint32_t) * num_vregs) +
     73            (sizeof(StackReference<mirror::Object>) * num_vregs);
     74   }
     75 
     76   // Create ShadowFrame in heap for deoptimization.
     77   static ShadowFrame* CreateDeoptimizedFrame(uint32_t num_vregs, ShadowFrame* link,
     78                                              ArtMethod* method, uint32_t dex_pc) {
     79     uint8_t* memory = new uint8_t[ComputeSize(num_vregs)];
     80     return Create(num_vregs, link, method, dex_pc, memory);
     81   }
     82 
     83   // Delete a ShadowFrame allocated on the heap for deoptimization.
     84   static void DeleteDeoptimizedFrame(ShadowFrame* sf) {
     85     uint8_t* memory = reinterpret_cast<uint8_t*>(sf);
     86     delete[] memory;
     87   }
     88 
     89   // Create ShadowFrame for interpreter using provided memory.
     90   static ShadowFrame* Create(uint32_t num_vregs, ShadowFrame* link,
     91                              ArtMethod* method, uint32_t dex_pc, void* memory) {
     92     ShadowFrame* sf = new (memory) ShadowFrame(num_vregs, link, method, dex_pc, true);
     93     return sf;
     94   }
     95   ~ShadowFrame() {}
     96 
     97   bool HasReferenceArray() const {
     98     return true;
     99   }
    100 
    101   uint32_t NumberOfVRegs() const {
    102     return number_of_vregs_;
    103   }
    104 
    105   uint32_t GetDexPC() const {
    106     return dex_pc_;
    107   }
    108 
    109   void SetDexPC(uint32_t dex_pc) {
    110     dex_pc_ = dex_pc;
    111   }
    112 
    113   ShadowFrame* GetLink() const {
    114     return link_;
    115   }
    116 
    117   void SetLink(ShadowFrame* frame) {
    118     DCHECK_NE(this, frame);
    119     link_ = frame;
    120   }
    121 
    122   int32_t GetVReg(size_t i) const {
    123     DCHECK_LT(i, NumberOfVRegs());
    124     const uint32_t* vreg = &vregs_[i];
    125     return *reinterpret_cast<const int32_t*>(vreg);
    126   }
    127 
    128   float GetVRegFloat(size_t i) const {
    129     DCHECK_LT(i, NumberOfVRegs());
    130     // NOTE: Strict-aliasing?
    131     const uint32_t* vreg = &vregs_[i];
    132     return *reinterpret_cast<const float*>(vreg);
    133   }
    134 
    135   int64_t GetVRegLong(size_t i) const {
    136     DCHECK_LT(i, NumberOfVRegs());
    137     const uint32_t* vreg = &vregs_[i];
    138     // Alignment attribute required for GCC 4.8
    139     typedef const int64_t unaligned_int64 __attribute__ ((aligned (4)));
    140     return *reinterpret_cast<unaligned_int64*>(vreg);
    141   }
    142 
    143   double GetVRegDouble(size_t i) const {
    144     DCHECK_LT(i, NumberOfVRegs());
    145     const uint32_t* vreg = &vregs_[i];
    146     // Alignment attribute required for GCC 4.8
    147     typedef const double unaligned_double __attribute__ ((aligned (4)));
    148     return *reinterpret_cast<unaligned_double*>(vreg);
    149   }
    150 
    151   template<VerifyObjectFlags kVerifyFlags = kDefaultVerifyFlags>
    152   mirror::Object* GetVRegReference(size_t i) const SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
    153     DCHECK_LT(i, NumberOfVRegs());
    154     mirror::Object* ref;
    155     if (HasReferenceArray()) {
    156       ref = References()[i].AsMirrorPtr();
    157     } else {
    158       const uint32_t* vreg_ptr = &vregs_[i];
    159       ref = reinterpret_cast<const StackReference<mirror::Object>*>(vreg_ptr)->AsMirrorPtr();
    160     }
    161     if (kUseReadBarrier) {
    162       ReadBarrier::AssertToSpaceInvariant(ref);
    163     }
    164     if (kVerifyFlags & kVerifyReads) {
    165       VerifyObject(ref);
    166     }
    167     return ref;
    168   }
    169 
    170   // Get view of vregs as range of consecutive arguments starting at i.
    171   uint32_t* GetVRegArgs(size_t i) {
    172     return &vregs_[i];
    173   }
    174 
    175   void SetVReg(size_t i, int32_t val) {
    176     DCHECK_LT(i, NumberOfVRegs());
    177     uint32_t* vreg = &vregs_[i];
    178     *reinterpret_cast<int32_t*>(vreg) = val;
    179     // This is needed for moving collectors since these can update the vreg references if they
    180     // happen to agree with references in the reference array.
    181     if (kMovingCollector && HasReferenceArray()) {
    182       References()[i].Clear();
    183     }
    184   }
    185 
    186   void SetVRegFloat(size_t i, float val) {
    187     DCHECK_LT(i, NumberOfVRegs());
    188     uint32_t* vreg = &vregs_[i];
    189     *reinterpret_cast<float*>(vreg) = val;
    190     // This is needed for moving collectors since these can update the vreg references if they
    191     // happen to agree with references in the reference array.
    192     if (kMovingCollector && HasReferenceArray()) {
    193       References()[i].Clear();
    194     }
    195   }
    196 
    197   void SetVRegLong(size_t i, int64_t val) {
    198     DCHECK_LT(i, NumberOfVRegs());
    199     uint32_t* vreg = &vregs_[i];
    200     // Alignment attribute required for GCC 4.8
    201     typedef int64_t unaligned_int64 __attribute__ ((aligned (4)));
    202     *reinterpret_cast<unaligned_int64*>(vreg) = val;
    203     // This is needed for moving collectors since these can update the vreg references if they
    204     // happen to agree with references in the reference array.
    205     if (kMovingCollector && HasReferenceArray()) {
    206       References()[i].Clear();
    207       References()[i + 1].Clear();
    208     }
    209   }
    210 
    211   void SetVRegDouble(size_t i, double val) {
    212     DCHECK_LT(i, NumberOfVRegs());
    213     uint32_t* vreg = &vregs_[i];
    214     // Alignment attribute required for GCC 4.8
    215     typedef double unaligned_double __attribute__ ((aligned (4)));
    216     *reinterpret_cast<unaligned_double*>(vreg) = val;
    217     // This is needed for moving collectors since these can update the vreg references if they
    218     // happen to agree with references in the reference array.
    219     if (kMovingCollector && HasReferenceArray()) {
    220       References()[i].Clear();
    221       References()[i + 1].Clear();
    222     }
    223   }
    224 
    225   template<VerifyObjectFlags kVerifyFlags = kDefaultVerifyFlags>
    226   void SetVRegReference(size_t i, mirror::Object* val) SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
    227     DCHECK_LT(i, NumberOfVRegs());
    228     if (kVerifyFlags & kVerifyWrites) {
    229       VerifyObject(val);
    230     }
    231     if (kUseReadBarrier) {
    232       ReadBarrier::AssertToSpaceInvariant(val);
    233     }
    234     uint32_t* vreg = &vregs_[i];
    235     reinterpret_cast<StackReference<mirror::Object>*>(vreg)->Assign(val);
    236     if (HasReferenceArray()) {
    237       References()[i].Assign(val);
    238     }
    239   }
    240 
    241   ArtMethod* GetMethod() const SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
    242     DCHECK(method_ != nullptr);
    243     return method_;
    244   }
    245 
    246   mirror::Object* GetThisObject() const SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
    247 
    248   mirror::Object* GetThisObject(uint16_t num_ins) const SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
    249 
    250   bool Contains(StackReference<mirror::Object>* shadow_frame_entry_obj) const {
    251     if (HasReferenceArray()) {
    252       return ((&References()[0] <= shadow_frame_entry_obj) &&
    253               (shadow_frame_entry_obj <= (&References()[NumberOfVRegs() - 1])));
    254     } else {
    255       uint32_t* shadow_frame_entry = reinterpret_cast<uint32_t*>(shadow_frame_entry_obj);
    256       return ((&vregs_[0] <= shadow_frame_entry) &&
    257               (shadow_frame_entry <= (&vregs_[NumberOfVRegs() - 1])));
    258     }
    259   }
    260 
    261   static size_t LinkOffset() {
    262     return OFFSETOF_MEMBER(ShadowFrame, link_);
    263   }
    264 
    265   static size_t MethodOffset() {
    266     return OFFSETOF_MEMBER(ShadowFrame, method_);
    267   }
    268 
    269   static size_t DexPCOffset() {
    270     return OFFSETOF_MEMBER(ShadowFrame, dex_pc_);
    271   }
    272 
    273   static size_t NumberOfVRegsOffset() {
    274     return OFFSETOF_MEMBER(ShadowFrame, number_of_vregs_);
    275   }
    276 
    277   static size_t VRegsOffset() {
    278     return OFFSETOF_MEMBER(ShadowFrame, vregs_);
    279   }
    280 
    281  private:
    282   ShadowFrame(uint32_t num_vregs, ShadowFrame* link, ArtMethod* method,
    283               uint32_t dex_pc, bool has_reference_array)
    284       : number_of_vregs_(num_vregs), link_(link), method_(method), dex_pc_(dex_pc) {
    285     if (has_reference_array) {
    286       memset(vregs_, 0, num_vregs * (sizeof(uint32_t) + sizeof(StackReference<mirror::Object>)));
    287     } else {
    288       memset(vregs_, 0, num_vregs * sizeof(uint32_t));
    289     }
    290   }
    291 
    292   const StackReference<mirror::Object>* References() const {
    293     DCHECK(HasReferenceArray());
    294     const uint32_t* vreg_end = &vregs_[NumberOfVRegs()];
    295     return reinterpret_cast<const StackReference<mirror::Object>*>(vreg_end);
    296   }
    297 
    298   StackReference<mirror::Object>* References() {
    299     return const_cast<StackReference<mirror::Object>*>(
    300         const_cast<const ShadowFrame*>(this)->References());
    301   }
    302 
    303   const uint32_t number_of_vregs_;
    304   // Link to previous shadow frame or null.
    305   ShadowFrame* link_;
    306   ArtMethod* method_;
    307   uint32_t dex_pc_;
    308   uint32_t vregs_[0];
    309 
    310   DISALLOW_IMPLICIT_CONSTRUCTORS(ShadowFrame);
    311 };
    312 
    313 class JavaFrameRootInfo : public RootInfo {
    314  public:
    315   JavaFrameRootInfo(uint32_t thread_id, const StackVisitor* stack_visitor, size_t vreg)
    316      : RootInfo(kRootJavaFrame, thread_id), stack_visitor_(stack_visitor), vreg_(vreg) {
    317   }
    318   virtual void Describe(std::ostream& os) const OVERRIDE
    319       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
    320 
    321  private:
    322   const StackVisitor* const stack_visitor_;
    323   const size_t vreg_;
    324 };
    325 
    326 // The managed stack is used to record fragments of managed code stacks. Managed code stacks
    327 // may either be shadow frames or lists of frames using fixed frame sizes. Transition records are
    328 // necessary for transitions between code using different frame layouts and transitions into native
    329 // code.
    330 class PACKED(4) ManagedStack {
    331  public:
    332   ManagedStack()
    333       : top_quick_frame_(nullptr), link_(nullptr), top_shadow_frame_(nullptr) {}
    334 
    335   void PushManagedStackFragment(ManagedStack* fragment) {
    336     // Copy this top fragment into given fragment.
    337     memcpy(fragment, this, sizeof(ManagedStack));
    338     // Clear this fragment, which has become the top.
    339     memset(this, 0, sizeof(ManagedStack));
    340     // Link our top fragment onto the given fragment.
    341     link_ = fragment;
    342   }
    343 
    344   void PopManagedStackFragment(const ManagedStack& fragment) {
    345     DCHECK(&fragment == link_);
    346     // Copy this given fragment back to the top.
    347     memcpy(this, &fragment, sizeof(ManagedStack));
    348   }
    349 
    350   ManagedStack* GetLink() const {
    351     return link_;
    352   }
    353 
    354   ArtMethod** GetTopQuickFrame() const {
    355     return top_quick_frame_;
    356   }
    357 
    358   void SetTopQuickFrame(ArtMethod** top) {
    359     DCHECK(top_shadow_frame_ == nullptr);
    360     top_quick_frame_ = top;
    361   }
    362 
    363   static size_t TopQuickFrameOffset() {
    364     return OFFSETOF_MEMBER(ManagedStack, top_quick_frame_);
    365   }
    366 
    367   ShadowFrame* PushShadowFrame(ShadowFrame* new_top_frame) {
    368     DCHECK(top_quick_frame_ == nullptr);
    369     ShadowFrame* old_frame = top_shadow_frame_;
    370     top_shadow_frame_ = new_top_frame;
    371     new_top_frame->SetLink(old_frame);
    372     return old_frame;
    373   }
    374 
    375   ShadowFrame* PopShadowFrame() {
    376     DCHECK(top_quick_frame_ == nullptr);
    377     CHECK(top_shadow_frame_ != nullptr);
    378     ShadowFrame* frame = top_shadow_frame_;
    379     top_shadow_frame_ = frame->GetLink();
    380     return frame;
    381   }
    382 
    383   ShadowFrame* GetTopShadowFrame() const {
    384     return top_shadow_frame_;
    385   }
    386 
    387   void SetTopShadowFrame(ShadowFrame* top) {
    388     DCHECK(top_quick_frame_ == nullptr);
    389     top_shadow_frame_ = top;
    390   }
    391 
    392   static size_t TopShadowFrameOffset() {
    393     return OFFSETOF_MEMBER(ManagedStack, top_shadow_frame_);
    394   }
    395 
    396   size_t NumJniShadowFrameReferences() const SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
    397 
    398   bool ShadowFramesContain(StackReference<mirror::Object>* shadow_frame_entry) const;
    399 
    400  private:
    401   ArtMethod** top_quick_frame_;
    402   ManagedStack* link_;
    403   ShadowFrame* top_shadow_frame_;
    404 };
    405 
    406 class StackVisitor {
    407  public:
    408   // This enum defines a flag to control whether inlined frames are included
    409   // when walking the stack.
    410   enum class StackWalkKind {
    411     kIncludeInlinedFrames,
    412     kSkipInlinedFrames,
    413   };
    414 
    415  protected:
    416   StackVisitor(Thread* thread, Context* context, StackWalkKind walk_kind)
    417       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
    418 
    419  public:
    420   virtual ~StackVisitor() {}
    421 
    422   // Return 'true' if we should continue to visit more frames, 'false' to stop.
    423   virtual bool VisitFrame() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) = 0;
    424 
    425   void WalkStack(bool include_transitions = false)
    426       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
    427 
    428   ArtMethod* GetMethod() const SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
    429     if (cur_shadow_frame_ != nullptr) {
    430       return cur_shadow_frame_->GetMethod();
    431     } else if (cur_quick_frame_ != nullptr) {
    432       return *cur_quick_frame_;
    433     } else {
    434       return nullptr;
    435     }
    436   }
    437 
    438   bool IsShadowFrame() const {
    439     return cur_shadow_frame_ != nullptr;
    440   }
    441 
    442   uint32_t GetDexPc(bool abort_on_failure = true) const SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
    443 
    444   mirror::Object* GetThisObject() const SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
    445 
    446   size_t GetNativePcOffset() const SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
    447 
    448   uintptr_t* CalleeSaveAddress(int num, size_t frame_size) const
    449       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
    450     // Callee saves are held at the top of the frame
    451     DCHECK(GetMethod() != nullptr);
    452     uint8_t* save_addr =
    453         reinterpret_cast<uint8_t*>(cur_quick_frame_) + frame_size - ((num + 1) * sizeof(void*));
    454 #if defined(__i386__) || defined(__x86_64__)
    455     save_addr -= sizeof(void*);  // account for return address
    456 #endif
    457     return reinterpret_cast<uintptr_t*>(save_addr);
    458   }
    459 
    460   // Returns the height of the stack in the managed stack frames, including transitions.
    461   size_t GetFrameHeight() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
    462     return GetNumFrames() - cur_depth_ - 1;
    463   }
    464 
    465   // Returns a frame ID for JDWP use, starting from 1.
    466   size_t GetFrameId() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
    467     return GetFrameHeight() + 1;
    468   }
    469 
    470   size_t GetNumFrames() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
    471     if (num_frames_ == 0) {
    472       num_frames_ = ComputeNumFrames(thread_, walk_kind_);
    473     }
    474     return num_frames_;
    475   }
    476 
    477   size_t GetFrameDepth() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
    478     return cur_depth_;
    479   }
    480 
    481   // Get the method and dex pc immediately after the one that's currently being visited.
    482   bool GetNextMethodAndDexPc(ArtMethod** next_method, uint32_t* next_dex_pc)
    483       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
    484 
    485   bool IsReferenceVReg(ArtMethod* m, uint16_t vreg)
    486       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
    487 
    488   bool GetVReg(ArtMethod* m, uint16_t vreg, VRegKind kind, uint32_t* val) const
    489       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
    490 
    491   bool GetVRegPair(ArtMethod* m, uint16_t vreg, VRegKind kind_lo, VRegKind kind_hi,
    492                    uint64_t* val) const
    493       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
    494 
    495   bool SetVReg(ArtMethod* m, uint16_t vreg, uint32_t new_value, VRegKind kind)
    496       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
    497 
    498   bool SetVRegPair(ArtMethod* m, uint16_t vreg, uint64_t new_value,
    499                    VRegKind kind_lo, VRegKind kind_hi)
    500       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
    501 
    502   uintptr_t* GetGPRAddress(uint32_t reg) const;
    503 
    504   // This is a fast-path for getting/setting values in a quick frame.
    505   uint32_t* GetVRegAddrFromQuickCode(ArtMethod** cur_quick_frame,
    506                                      const DexFile::CodeItem* code_item,
    507                                      uint32_t core_spills, uint32_t fp_spills, size_t frame_size,
    508                                      uint16_t vreg) const {
    509     int offset = GetVRegOffsetFromQuickCode(
    510         code_item, core_spills, fp_spills, frame_size, vreg, kRuntimeISA);
    511     DCHECK_EQ(cur_quick_frame, GetCurrentQuickFrame());
    512     uint8_t* vreg_addr = reinterpret_cast<uint8_t*>(cur_quick_frame) + offset;
    513     return reinterpret_cast<uint32_t*>(vreg_addr);
    514   }
    515 
    516   uintptr_t GetReturnPc() const SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
    517 
    518   void SetReturnPc(uintptr_t new_ret_pc) SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
    519 
    520   /*
    521    * Return sp-relative offset for a Dalvik virtual register, compiler
    522    * spill or Method* in bytes using Method*.
    523    * Note that (reg == -1) denotes an invalid Dalvik register. For the
    524    * positive values, the Dalvik registers come first, followed by the
    525    * Method*, followed by other special temporaries if any, followed by
    526    * regular compiler temporary. As of now we only have the Method* as
    527    * as a special compiler temporary.
    528    * A compiler temporary can be thought of as a virtual register that
    529    * does not exist in the dex but holds intermediate values to help
    530    * optimizations and code generation. A special compiler temporary is
    531    * one whose location in frame is well known while non-special ones
    532    * do not have a requirement on location in frame as long as code
    533    * generator itself knows how to access them.
    534    *
    535    *     +-------------------------------+
    536    *     | IN[ins-1]                     |  {Note: resides in caller's frame}
    537    *     |       .                       |
    538    *     | IN[0]                         |
    539    *     | caller's ArtMethod            |  ... ArtMethod*
    540    *     +===============================+  {Note: start of callee's frame}
    541    *     | core callee-save spill        |  {variable sized}
    542    *     +-------------------------------+
    543    *     | fp callee-save spill          |
    544    *     +-------------------------------+
    545    *     | filler word                   |  {For compatibility, if V[locals-1] used as wide
    546    *     +-------------------------------+
    547    *     | V[locals-1]                   |
    548    *     | V[locals-2]                   |
    549    *     |      .                        |
    550    *     |      .                        |  ... (reg == 2)
    551    *     | V[1]                          |  ... (reg == 1)
    552    *     | V[0]                          |  ... (reg == 0) <---- "locals_start"
    553    *     +-------------------------------+
    554    *     | stack alignment padding       |  {0 to (kStackAlignWords-1) of padding}
    555    *     +-------------------------------+
    556    *     | Compiler temp region          |  ... (reg >= max_num_special_temps)
    557    *     |      .                        |
    558    *     |      .                        |
    559    *     | V[max_num_special_temps + 1]  |
    560    *     | V[max_num_special_temps + 0]  |
    561    *     +-------------------------------+
    562    *     | OUT[outs-1]                   |
    563    *     | OUT[outs-2]                   |
    564    *     |       .                       |
    565    *     | OUT[0]                        |
    566    *     | ArtMethod*                    |  ... (reg == num_total_code_regs == special_temp_value) <<== sp, 16-byte aligned
    567    *     +===============================+
    568    */
    569   static int GetVRegOffsetFromQuickCode(const DexFile::CodeItem* code_item,
    570                                         uint32_t core_spills, uint32_t fp_spills,
    571                                         size_t frame_size, int reg, InstructionSet isa);
    572 
    573   static int GetOutVROffset(uint16_t out_num, InstructionSet isa) {
    574     // According to stack model, the first out is above the Method referernce.
    575     return InstructionSetPointerSize(isa) + out_num * sizeof(uint32_t);
    576   }
    577 
    578   bool IsInInlinedFrame() const {
    579     return false;
    580   }
    581 
    582   uintptr_t GetCurrentQuickFramePc() const {
    583     return cur_quick_frame_pc_;
    584   }
    585 
    586   ArtMethod** GetCurrentQuickFrame() const {
    587     return cur_quick_frame_;
    588   }
    589 
    590   ShadowFrame* GetCurrentShadowFrame() const {
    591     return cur_shadow_frame_;
    592   }
    593 
    594   HandleScope* GetCurrentHandleScope(size_t pointer_size) const {
    595     ArtMethod** sp = GetCurrentQuickFrame();
    596     // Skip ArtMethod*; handle scope comes next;
    597     return reinterpret_cast<HandleScope*>(reinterpret_cast<uintptr_t>(sp) + pointer_size);
    598   }
    599 
    600   std::string DescribeLocation() const SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
    601 
    602   static size_t ComputeNumFrames(Thread* thread, StackWalkKind walk_kind)
    603       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
    604 
    605   static void DescribeStack(Thread* thread) SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
    606 
    607  private:
    608   // Private constructor known in the case that num_frames_ has already been computed.
    609   StackVisitor(Thread* thread, Context* context, StackWalkKind walk_kind, size_t num_frames)
    610       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
    611 
    612   bool IsAccessibleRegister(uint32_t reg, bool is_float) const {
    613     return is_float ? IsAccessibleFPR(reg) : IsAccessibleGPR(reg);
    614   }
    615   uintptr_t GetRegister(uint32_t reg, bool is_float) const {
    616     DCHECK(IsAccessibleRegister(reg, is_float));
    617     return is_float ? GetFPR(reg) : GetGPR(reg);
    618   }
    619   void SetRegister(uint32_t reg, uintptr_t value, bool is_float) {
    620     DCHECK(IsAccessibleRegister(reg, is_float));
    621     if (is_float) {
    622       SetFPR(reg, value);
    623     } else {
    624       SetGPR(reg, value);
    625     }
    626   }
    627 
    628   bool IsAccessibleGPR(uint32_t reg) const;
    629   uintptr_t GetGPR(uint32_t reg) const;
    630   void SetGPR(uint32_t reg, uintptr_t value);
    631 
    632   bool IsAccessibleFPR(uint32_t reg) const;
    633   uintptr_t GetFPR(uint32_t reg) const;
    634   void SetFPR(uint32_t reg, uintptr_t value);
    635 
    636   bool GetVRegFromQuickCode(ArtMethod* m, uint16_t vreg, VRegKind kind,
    637                             uint32_t* val) const
    638       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
    639   bool GetVRegFromOptimizedCode(ArtMethod* m, uint16_t vreg, VRegKind kind,
    640                                 uint32_t* val) const
    641       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
    642   bool GetRegisterIfAccessible(uint32_t reg, VRegKind kind, uint32_t* val) const
    643       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
    644 
    645   bool GetVRegPairFromQuickCode(ArtMethod* m, uint16_t vreg, VRegKind kind_lo,
    646                                 VRegKind kind_hi, uint64_t* val) const
    647       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
    648   bool GetVRegPairFromOptimizedCode(ArtMethod* m, uint16_t vreg,
    649                                     VRegKind kind_lo, VRegKind kind_hi,
    650                                     uint64_t* val) const
    651       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
    652   bool GetRegisterPairIfAccessible(uint32_t reg_lo, uint32_t reg_hi, VRegKind kind_lo,
    653                                    uint64_t* val) const
    654       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
    655 
    656   bool SetVRegFromQuickCode(ArtMethod* m, uint16_t vreg, uint32_t new_value,
    657                             VRegKind kind)
    658       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
    659   bool SetRegisterIfAccessible(uint32_t reg, uint32_t new_value, VRegKind kind)
    660       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
    661 
    662   bool SetVRegPairFromQuickCode(ArtMethod* m, uint16_t vreg, uint64_t new_value,
    663                                 VRegKind kind_lo, VRegKind kind_hi)
    664       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
    665   bool SetRegisterPairIfAccessible(uint32_t reg_lo, uint32_t reg_hi, uint64_t new_value,
    666                                    bool is_float)
    667       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
    668 
    669   void SanityCheckFrame() const SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
    670 
    671   Thread* const thread_;
    672   const StackWalkKind walk_kind_;
    673   ShadowFrame* cur_shadow_frame_;
    674   ArtMethod** cur_quick_frame_;
    675   uintptr_t cur_quick_frame_pc_;
    676   // Lazily computed, number of frames in the stack.
    677   size_t num_frames_;
    678   // Depth of the frame we're currently at.
    679   size_t cur_depth_;
    680 
    681  protected:
    682   Context* const context_;
    683 };
    684 
    685 }  // namespace art
    686 
    687 #endif  // ART_RUNTIME_STACK_H_
    688