runtime/stack.cc - platform/art - Gitiles

 /*
  * Copyright (C) 2011 The Android Open Source Project
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *
  *      http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */

 #include "stack.h"

 #include "mirror/art_method-inl.h"
 #include "mirror/class-inl.h"
 #include "mirror/object.h"
 #include "mirror/object-inl.h"
 #include "mirror/object_array-inl.h"
 #include "object_utils.h"
 #include "runtime.h"
 #include "thread_list.h"
 #include "throw_location.h"
 #include "vmap_table.h"

 namespace art {

 bool ShadowFrame::VerifyReference(const mirror::Object* val) const {
   return !Runtime::Current()->GetHeap()->IsInTempSpace(val);
 }

 mirror::Object* ShadowFrame::GetThisObject() const {
   mirror::ArtMethod* m = GetMethod();
   if (m->IsStatic()) {
     return NULL;
   } else if (m->IsNative()) {
     return GetVRegReference(0);
   } else {
     const DexFile::CodeItem* code_item = MethodHelper(m).GetCodeItem();
     CHECK(code_item != NULL) << PrettyMethod(m);
     uint16_t reg = code_item->registers_size_ - code_item->ins_size_;
     return GetVRegReference(reg);
   }
 }

 mirror::Object* ShadowFrame::GetThisObject(uint16_t num_ins) const {
   mirror::ArtMethod* m = GetMethod();
   if (m->IsStatic()) {
     return NULL;
   } else {
     return GetVRegReference(NumberOfVRegs() - num_ins);
   }
 }

 ThrowLocation ShadowFrame::GetCurrentLocationForThrow() const {
   return ThrowLocation(GetThisObject(), GetMethod(), GetDexPC());
 }

 size_t ManagedStack::NumJniShadowFrameReferences() const {
   size_t count = 0;
   for (const ManagedStack* current_fragment = this; current_fragment != NULL;
        current_fragment = current_fragment->GetLink()) {
     for (ShadowFrame* current_frame = current_fragment->top_shadow_frame_; current_frame != NULL;
          current_frame = current_frame->GetLink()) {
       if (current_frame->GetMethod()->IsNative()) {
         // The JNI ShadowFrame only contains references. (For indirect reference.)
         count += current_frame->NumberOfVRegs();
       }
     }
   }
   return count;
 }

 bool ManagedStack::ShadowFramesContain(mirror::Object** shadow_frame_entry) const {
   for (const ManagedStack* current_fragment = this; current_fragment != NULL;
        current_fragment = current_fragment->GetLink()) {
     for (ShadowFrame* current_frame = current_fragment->top_shadow_frame_; current_frame != NULL;
          current_frame = current_frame->GetLink()) {
       if (current_frame->Contains(shadow_frame_entry)) {
         return true;
       }
     }
   }
   return false;
 }

 StackVisitor::StackVisitor(Thread* thread, Context* context)
     : thread_(thread), cur_shadow_frame_(NULL),
       cur_quick_frame_(NULL), cur_quick_frame_pc_(0), num_frames_(0), cur_depth_(0),
       context_(context) {
   DCHECK(thread == Thread::Current() || thread->IsSuspended()) << *thread;
 }

 uint32_t StackVisitor::GetDexPc() const {
   if (cur_shadow_frame_ != NULL) {
     return cur_shadow_frame_->GetDexPC();
   } else if (cur_quick_frame_ != NULL) {
     return GetMethod()->ToDexPc(cur_quick_frame_pc_);
   } else {
     return 0;
   }
 }

 mirror::Object* StackVisitor::GetThisObject() const {
   mirror::ArtMethod* m = GetMethod();
   if (m->IsStatic()) {
     return NULL;
   } else if (m->IsNative()) {
     if (cur_quick_frame_ != NULL) {
       StackIndirectReferenceTable* sirt =
           reinterpret_cast<StackIndirectReferenceTable*>(
               reinterpret_cast<char*>(cur_quick_frame_) +
               m->GetSirtOffsetInBytes());
       return sirt->GetReference(0);
     } else {
       return cur_shadow_frame_->GetVRegReference(0);
     }
   } else {
     const DexFile::CodeItem* code_item = MethodHelper(m).GetCodeItem();
     if (code_item == NULL) {
       UNIMPLEMENTED(ERROR) << "Failed to determine this object of abstract or proxy method"
           << PrettyMethod(m);
       return NULL;
     } else {
       uint16_t reg = code_item->registers_size_ - code_item->ins_size_;
       return reinterpret_cast<mirror::Object*>(GetVReg(m, reg, kReferenceVReg));
     }
   }
 }

 size_t StackVisitor::GetNativePcOffset() const {
   DCHECK(!IsShadowFrame());
   return GetMethod()->NativePcOffset(cur_quick_frame_pc_);
 }

 uint32_t StackVisitor::GetVReg(mirror::ArtMethod* m, uint16_t vreg, VRegKind kind) const {
   if (cur_quick_frame_ != NULL) {
     DCHECK(context_ != NULL);  // You can't reliably read registers without a context.
     DCHECK(m == GetMethod());
     const VmapTable vmap_table(m->GetVmapTable());
     uint32_t vmap_offset;
     // TODO: IsInContext stops before spotting floating point registers.
     if (vmap_table.IsInContext(vreg, kind, &vmap_offset)) {
       bool is_float = (kind == kFloatVReg) || (kind == kDoubleLoVReg) || (kind == kDoubleHiVReg);
       uint32_t spill_mask = is_float ? m->GetFpSpillMask()
                                      : m->GetCoreSpillMask();
       return GetGPR(vmap_table.ComputeRegister(spill_mask, vmap_offset, kind));
     } else {
       const DexFile::CodeItem* code_item = MethodHelper(m).GetCodeItem();
       DCHECK(code_item != NULL) << PrettyMethod(m);  // Can't be NULL or how would we compile its instructions?
       size_t frame_size = m->GetFrameSizeInBytes();
       return *GetVRegAddr(cur_quick_frame_, code_item, m->GetCoreSpillMask(), m->GetFpSpillMask(),
                           frame_size, vreg);
     }
   } else {
     return cur_shadow_frame_->GetVReg(vreg);
   }
 }

 void StackVisitor::SetVReg(mirror::ArtMethod* m, uint16_t vreg, uint32_t new_value,
                            VRegKind kind) {
   if (cur_quick_frame_ != NULL) {
     DCHECK(context_ != NULL);  // You can't reliably write registers without a context.
     DCHECK(m == GetMethod());
     const VmapTable vmap_table(m->GetVmapTable());
     uint32_t vmap_offset;
     // TODO: IsInContext stops before spotting floating point registers.
     if (vmap_table.IsInContext(vreg, kind, &vmap_offset)) {
       bool is_float = (kind == kFloatVReg) || (kind == kDoubleLoVReg) || (kind == kDoubleHiVReg);
       uint32_t spill_mask = is_float ? m->GetFpSpillMask() : m->GetCoreSpillMask();
       const uint32_t reg = vmap_table.ComputeRegister(spill_mask, vmap_offset, kReferenceVReg);
       SetGPR(reg, new_value);
     } else {
       const DexFile::CodeItem* code_item = MethodHelper(m).GetCodeItem();
       DCHECK(code_item != NULL) << PrettyMethod(m);  // Can't be NULL or how would we compile its instructions?
       uint32_t core_spills = m->GetCoreSpillMask();
       uint32_t fp_spills = m->GetFpSpillMask();
       size_t frame_size = m->GetFrameSizeInBytes();
       int offset = GetVRegOffset(code_item, core_spills, fp_spills, frame_size, vreg);
       byte* vreg_addr = reinterpret_cast<byte*>(GetCurrentQuickFrame()) + offset;
       *reinterpret_cast<uint32_t*>(vreg_addr) = new_value;
     }
   } else {
     return cur_shadow_frame_->SetVReg(vreg, new_value);
   }
 }

 uintptr_t StackVisitor::GetGPR(uint32_t reg) const {
   DCHECK(cur_quick_frame_ != NULL) << "This is a quick frame routine";
   return context_->GetGPR(reg);
 }

 void StackVisitor::SetGPR(uint32_t reg, uintptr_t value) {
   DCHECK(cur_quick_frame_ != NULL) << "This is a quick frame routine";
   context_->SetGPR(reg, value);
 }

 uintptr_t StackVisitor::GetReturnPc() const {
   mirror::ArtMethod** sp = GetCurrentQuickFrame();
   DCHECK(sp != NULL);
   byte* pc_addr = reinterpret_cast<byte*>(sp) + GetMethod()->GetReturnPcOffsetInBytes();
   return *reinterpret_cast<uintptr_t*>(pc_addr);
 }

 void StackVisitor::SetReturnPc(uintptr_t new_ret_pc) {
   mirror::ArtMethod** sp = GetCurrentQuickFrame();
   CHECK(sp != NULL);
   byte* pc_addr = reinterpret_cast<byte*>(sp) + GetMethod()->GetReturnPcOffsetInBytes();
   *reinterpret_cast<uintptr_t*>(pc_addr) = new_ret_pc;
 }

 size_t StackVisitor::ComputeNumFrames(Thread* thread) {
   struct NumFramesVisitor : public StackVisitor {
     explicit NumFramesVisitor(Thread* thread)
         : StackVisitor(thread, NULL), frames(0) {}

     virtual bool VisitFrame() {
       frames++;
       return true;
     }

     size_t frames;
   };
   NumFramesVisitor visitor(thread);
   visitor.WalkStack(true);
   return visitor.frames;
 }

 void StackVisitor::DescribeStack(Thread* thread) {
   struct DescribeStackVisitor : public StackVisitor {
     explicit DescribeStackVisitor(Thread* thread)
         : StackVisitor(thread, NULL) {}

     virtual bool VisitFrame() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
       LOG(INFO) << "Frame Id=" << GetFrameId() << " " << DescribeLocation();
       return true;
     }
   };
   DescribeStackVisitor visitor(thread);
   visitor.WalkStack(true);
 }

 std::string StackVisitor::DescribeLocation() const {
   std::string result("Visiting method '");
   mirror::ArtMethod* m = GetMethod();
   if (m == NULL) {
     return "upcall";
   }
   result += PrettyMethod(m);
   result += StringPrintf("' at dex PC 0x%04zx", GetDexPc());
   if (!IsShadowFrame()) {
     result += StringPrintf(" (native PC %p)", reinterpret_cast<void*>(GetCurrentQuickFramePc()));
   }
   return result;
 }

 instrumentation::InstrumentationStackFrame& StackVisitor::GetInstrumentationStackFrame(uint32_t depth) const {
   CHECK_LT(depth, thread_->GetInstrumentationStack()->size());
   return thread_->GetInstrumentationStack()->at(depth);
 }

 void StackVisitor::SanityCheckFrame() const {
 #ifndef NDEBUG
   mirror::ArtMethod* method = GetMethod();
   CHECK(method->GetClass() == mirror::ArtMethod::GetJavaLangReflectArtMethod());
   if (cur_quick_frame_ != NULL) {
     method->AssertPcIsWithinCode(cur_quick_frame_pc_);
     // Frame sanity.
     size_t frame_size = method->GetFrameSizeInBytes();
     CHECK_NE(frame_size, 0u);
     // A rough guess at an upper size we expect to see for a frame. The 256 is
     // a dex register limit. The 16 incorporates callee save spills and
     // outgoing argument set up.
     const size_t kMaxExpectedFrameSize = 256 * sizeof(word) + 16;
     CHECK_LE(frame_size, kMaxExpectedFrameSize);
     size_t return_pc_offset = method->GetReturnPcOffsetInBytes();
     CHECK_LT(return_pc_offset, frame_size);
   }
 #endif
 }

 void StackVisitor::WalkStack(bool include_transitions) {
   DCHECK(thread_ == Thread::Current() || thread_->IsSuspended());
   CHECK_EQ(cur_depth_, 0U);
   bool exit_stubs_installed = Runtime::Current()->GetInstrumentation()->AreExitStubsInstalled();
   uint32_t instrumentation_stack_depth = 0;
   for (const ManagedStack* current_fragment = thread_->GetManagedStack(); current_fragment != NULL;
        current_fragment = current_fragment->GetLink()) {
     cur_shadow_frame_ = current_fragment->GetTopShadowFrame();
     cur_quick_frame_ = current_fragment->GetTopQuickFrame();
     cur_quick_frame_pc_ = current_fragment->GetTopQuickFramePc();
     if (cur_quick_frame_ != NULL) {  // Handle quick stack frames.
       // Can't be both a shadow and a quick fragment.
       DCHECK(current_fragment->GetTopShadowFrame() == NULL);
       mirror::ArtMethod* method = *cur_quick_frame_;
       while (method != NULL) {
         SanityCheckFrame();
         bool should_continue = VisitFrame();
         if (UNLIKELY(!should_continue)) {
           return;
         }
         if (context_ != NULL) {
           context_->FillCalleeSaves(*this);
         }
         size_t frame_size = method->GetFrameSizeInBytes();
         // Compute PC for next stack frame from return PC.
         size_t return_pc_offset = method->GetReturnPcOffsetInBytes();
         byte* return_pc_addr = reinterpret_cast<byte*>(cur_quick_frame_) + return_pc_offset;
         uintptr_t return_pc = *reinterpret_cast<uintptr_t*>(return_pc_addr);
         if (UNLIKELY(exit_stubs_installed)) {
           // While profiling, the return pc is restored from the side stack, except when walking
           // the stack for an exception where the side stack will be unwound in VisitFrame.
           if (GetQuickInstrumentationExitPc() == return_pc) {
             const instrumentation::InstrumentationStackFrame& instrumentation_frame =
                 GetInstrumentationStackFrame(instrumentation_stack_depth);
             instrumentation_stack_depth++;
             if (GetMethod() == Runtime::Current()->GetCalleeSaveMethod(Runtime::kSaveAll)) {
               // Skip runtime save all callee frames which are used to deliver exceptions.
             } else if (instrumentation_frame.interpreter_entry_) {
               mirror::ArtMethod* callee = Runtime::Current()->GetCalleeSaveMethod(Runtime::kRefsAndArgs);
               CHECK_EQ(GetMethod(), callee) << "Expected: " << PrettyMethod(callee) << " Found: "
                   << PrettyMethod(GetMethod());
             } else if (instrumentation_frame.method_ != GetMethod()) {
               LOG(FATAL)  << "Expected: " << PrettyMethod(instrumentation_frame.method_)
                 << " Found: " << PrettyMethod(GetMethod());
             }
             if (num_frames_ != 0) {
               // Check agreement of frame Ids only if num_frames_ is computed to avoid infinite
               // recursion.
               CHECK(instrumentation_frame.frame_id_ == GetFrameId())
                     << "Expected: " << instrumentation_frame.frame_id_
                     << " Found: " << GetFrameId();
             }
             return_pc = instrumentation_frame.return_pc_;
           }
         }
         cur_quick_frame_pc_ = return_pc;
         byte* next_frame = reinterpret_cast<byte*>(cur_quick_frame_) + frame_size;
         cur_quick_frame_ = reinterpret_cast<mirror::ArtMethod**>(next_frame);
         cur_depth_++;
         method = *cur_quick_frame_;
       }
     } else if (cur_shadow_frame_ != NULL) {
       do {
         SanityCheckFrame();
         bool should_continue = VisitFrame();
         if (UNLIKELY(!should_continue)) {
           return;
         }
         cur_depth_++;
         cur_shadow_frame_ = cur_shadow_frame_->GetLink();
       } while (cur_shadow_frame_ != NULL);
     }
     if (include_transitions) {
       bool should_continue = VisitFrame();
       if (!should_continue) {
         return;
       }
     }
     cur_depth_++;
   }
   if (num_frames_ != 0) {
     CHECK_EQ(cur_depth_, num_frames_);
   }
 }

 }  // namespace art
	/*
	* Copyright (C) 2011 The Android Open Source Project
	*
	* Licensed under the Apache License, Version 2.0 (the "License");
	* you may not use this file except in compliance with the License.
	* You may obtain a copy of the License at
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing, software
	* distributed under the License is distributed on an "AS IS" BASIS,
	* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	* See the License for the specific language governing permissions and
	* limitations under the License.
	*/

	#include "stack.h"

	#include "mirror/art_method-inl.h"
	#include "mirror/class-inl.h"
	#include "mirror/object.h"
	#include "mirror/object-inl.h"
	#include "mirror/object_array-inl.h"
	#include "object_utils.h"
	#include "runtime.h"
	#include "thread_list.h"
	#include "throw_location.h"
	#include "vmap_table.h"

	namespace art {

	bool ShadowFrame::VerifyReference(const mirror::Object* val) const {
	return !Runtime::Current()->GetHeap()->IsInTempSpace(val);
	}

	mirror::Object* ShadowFrame::GetThisObject() const {
	mirror::ArtMethod* m = GetMethod();
	if (m->IsStatic()) {
	return NULL;
	} else if (m->IsNative()) {
	return GetVRegReference(0);
	} else {
	const DexFile::CodeItem* code_item = MethodHelper(m).GetCodeItem();
	CHECK(code_item != NULL) << PrettyMethod(m);
	uint16_t reg = code_item->registers_size_ - code_item->ins_size_;
	return GetVRegReference(reg);
	}
	}

	mirror::Object* ShadowFrame::GetThisObject(uint16_t num_ins) const {
	mirror::ArtMethod* m = GetMethod();
	if (m->IsStatic()) {
	return NULL;
	} else {
	return GetVRegReference(NumberOfVRegs() - num_ins);
	}
	}

	ThrowLocation ShadowFrame::GetCurrentLocationForThrow() const {
	return ThrowLocation(GetThisObject(), GetMethod(), GetDexPC());
	}

	size_t ManagedStack::NumJniShadowFrameReferences() const {
	size_t count = 0;
	for (const ManagedStack* current_fragment = this; current_fragment != NULL;
	current_fragment = current_fragment->GetLink()) {
	for (ShadowFrame* current_frame = current_fragment->top_shadow_frame_; current_frame != NULL;
	current_frame = current_frame->GetLink()) {
	if (current_frame->GetMethod()->IsNative()) {
	// The JNI ShadowFrame only contains references. (For indirect reference.)
	count += current_frame->NumberOfVRegs();
	}
	}
	}
	return count;
	}

	bool ManagedStack::ShadowFramesContain(mirror::Object** shadow_frame_entry) const {
	for (const ManagedStack* current_fragment = this; current_fragment != NULL;
	current_fragment = current_fragment->GetLink()) {
	for (ShadowFrame* current_frame = current_fragment->top_shadow_frame_; current_frame != NULL;
	current_frame = current_frame->GetLink()) {
	if (current_frame->Contains(shadow_frame_entry)) {
	return true;
	}
	}
	}
	return false;
	}

	StackVisitor::StackVisitor(Thread* thread, Context* context)
	: thread_(thread), cur_shadow_frame_(NULL),
	cur_quick_frame_(NULL), cur_quick_frame_pc_(0), num_frames_(0), cur_depth_(0),
	context_(context) {
	DCHECK(thread == Thread::Current() \|\| thread->IsSuspended()) << *thread;
	}

	uint32_t StackVisitor::GetDexPc() const {
	if (cur_shadow_frame_ != NULL) {
	return cur_shadow_frame_->GetDexPC();
	} else if (cur_quick_frame_ != NULL) {
	return GetMethod()->ToDexPc(cur_quick_frame_pc_);
	} else {
	return 0;
	}
	}

	mirror::Object* StackVisitor::GetThisObject() const {
	mirror::ArtMethod* m = GetMethod();
	if (m->IsStatic()) {
	return NULL;
	} else if (m->IsNative()) {
	if (cur_quick_frame_ != NULL) {
	StackIndirectReferenceTable* sirt =
	reinterpret_cast<StackIndirectReferenceTable*>(
	reinterpret_cast<char*>(cur_quick_frame_) +
	m->GetSirtOffsetInBytes());
	return sirt->GetReference(0);
	} else {
	return cur_shadow_frame_->GetVRegReference(0);
	}
	} else {
	const DexFile::CodeItem* code_item = MethodHelper(m).GetCodeItem();
	if (code_item == NULL) {
	UNIMPLEMENTED(ERROR) << "Failed to determine this object of abstract or proxy method"
	<< PrettyMethod(m);
	return NULL;
	} else {
	uint16_t reg = code_item->registers_size_ - code_item->ins_size_;
	return reinterpret_cast<mirror::Object*>(GetVReg(m, reg, kReferenceVReg));
	}
	}
	}

	size_t StackVisitor::GetNativePcOffset() const {
	DCHECK(!IsShadowFrame());
	return GetMethod()->NativePcOffset(cur_quick_frame_pc_);
	}

	uint32_t StackVisitor::GetVReg(mirror::ArtMethod* m, uint16_t vreg, VRegKind kind) const {
	if (cur_quick_frame_ != NULL) {
	DCHECK(context_ != NULL); // You can't reliably read registers without a context.
	DCHECK(m == GetMethod());
	const VmapTable vmap_table(m->GetVmapTable());
	uint32_t vmap_offset;
	// TODO: IsInContext stops before spotting floating point registers.
	if (vmap_table.IsInContext(vreg, kind, &vmap_offset)) {
	bool is_float = (kind == kFloatVReg) \|\| (kind == kDoubleLoVReg) \|\| (kind == kDoubleHiVReg);
	uint32_t spill_mask = is_float ? m->GetFpSpillMask()
	: m->GetCoreSpillMask();
	return GetGPR(vmap_table.ComputeRegister(spill_mask, vmap_offset, kind));
	} else {
	const DexFile::CodeItem* code_item = MethodHelper(m).GetCodeItem();
	DCHECK(code_item != NULL) << PrettyMethod(m); // Can't be NULL or how would we compile its instructions?
	size_t frame_size = m->GetFrameSizeInBytes();
	return *GetVRegAddr(cur_quick_frame_, code_item, m->GetCoreSpillMask(), m->GetFpSpillMask(),
	frame_size, vreg);
	}
	} else {
	return cur_shadow_frame_->GetVReg(vreg);
	}
	}

	void StackVisitor::SetVReg(mirror::ArtMethod* m, uint16_t vreg, uint32_t new_value,
	VRegKind kind) {
	if (cur_quick_frame_ != NULL) {
	DCHECK(context_ != NULL); // You can't reliably write registers without a context.
	DCHECK(m == GetMethod());
	const VmapTable vmap_table(m->GetVmapTable());
	uint32_t vmap_offset;
	// TODO: IsInContext stops before spotting floating point registers.
	if (vmap_table.IsInContext(vreg, kind, &vmap_offset)) {
	bool is_float = (kind == kFloatVReg) \|\| (kind == kDoubleLoVReg) \|\| (kind == kDoubleHiVReg);
	uint32_t spill_mask = is_float ? m->GetFpSpillMask() : m->GetCoreSpillMask();
	const uint32_t reg = vmap_table.ComputeRegister(spill_mask, vmap_offset, kReferenceVReg);
	SetGPR(reg, new_value);
	} else {
	const DexFile::CodeItem* code_item = MethodHelper(m).GetCodeItem();
	DCHECK(code_item != NULL) << PrettyMethod(m); // Can't be NULL or how would we compile its instructions?
	uint32_t core_spills = m->GetCoreSpillMask();
	uint32_t fp_spills = m->GetFpSpillMask();
	size_t frame_size = m->GetFrameSizeInBytes();
	int offset = GetVRegOffset(code_item, core_spills, fp_spills, frame_size, vreg);
	byte* vreg_addr = reinterpret_cast<byte*>(GetCurrentQuickFrame()) + offset;
	reinterpret_cast<uint32_t>(vreg_addr) = new_value;
	}
	} else {
	return cur_shadow_frame_->SetVReg(vreg, new_value);
	}
	}

	uintptr_t StackVisitor::GetGPR(uint32_t reg) const {
	DCHECK(cur_quick_frame_ != NULL) << "This is a quick frame routine";
	return context_->GetGPR(reg);
	}

	void StackVisitor::SetGPR(uint32_t reg, uintptr_t value) {
	DCHECK(cur_quick_frame_ != NULL) << "This is a quick frame routine";
	context_->SetGPR(reg, value);
	}

	uintptr_t StackVisitor::GetReturnPc() const {
	mirror::ArtMethod** sp = GetCurrentQuickFrame();
	DCHECK(sp != NULL);
	byte* pc_addr = reinterpret_cast<byte*>(sp) + GetMethod()->GetReturnPcOffsetInBytes();
	return reinterpret_cast<uintptr_t>(pc_addr);
	}

	void StackVisitor::SetReturnPc(uintptr_t new_ret_pc) {
	mirror::ArtMethod** sp = GetCurrentQuickFrame();
	CHECK(sp != NULL);
	byte* pc_addr = reinterpret_cast<byte*>(sp) + GetMethod()->GetReturnPcOffsetInBytes();
	reinterpret_cast<uintptr_t>(pc_addr) = new_ret_pc;
	}

	size_t StackVisitor::ComputeNumFrames(Thread* thread) {
	struct NumFramesVisitor : public StackVisitor {
	explicit NumFramesVisitor(Thread* thread)
	: StackVisitor(thread, NULL), frames(0) {}

	virtual bool VisitFrame() {
	frames++;
	return true;
	}

	size_t frames;
	};
	NumFramesVisitor visitor(thread);
	visitor.WalkStack(true);
	return visitor.frames;
	}

	void StackVisitor::DescribeStack(Thread* thread) {
	struct DescribeStackVisitor : public StackVisitor {
	explicit DescribeStackVisitor(Thread* thread)
	: StackVisitor(thread, NULL) {}

	virtual bool VisitFrame() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
	LOG(INFO) << "Frame Id=" << GetFrameId() << " " << DescribeLocation();
	return true;
	}
	};
	DescribeStackVisitor visitor(thread);
	visitor.WalkStack(true);
	}

	std::string StackVisitor::DescribeLocation() const {
	std::string result("Visiting method '");
	mirror::ArtMethod* m = GetMethod();
	if (m == NULL) {
	return "upcall";
	}
	result += PrettyMethod(m);
	result += StringPrintf("' at dex PC 0x%04zx", GetDexPc());
	if (!IsShadowFrame()) {
	result += StringPrintf(" (native PC %p)", reinterpret_cast<void*>(GetCurrentQuickFramePc()));
	}
	return result;
	}

	instrumentation::InstrumentationStackFrame& StackVisitor::GetInstrumentationStackFrame(uint32_t depth) const {
	CHECK_LT(depth, thread_->GetInstrumentationStack()->size());
	return thread_->GetInstrumentationStack()->at(depth);
	}

	void StackVisitor::SanityCheckFrame() const {
	#ifndef NDEBUG
	mirror::ArtMethod* method = GetMethod();
	CHECK(method->GetClass() == mirror::ArtMethod::GetJavaLangReflectArtMethod());
	if (cur_quick_frame_ != NULL) {
	method->AssertPcIsWithinCode(cur_quick_frame_pc_);
	// Frame sanity.
	size_t frame_size = method->GetFrameSizeInBytes();
	CHECK_NE(frame_size, 0u);
	// A rough guess at an upper size we expect to see for a frame. The 256 is
	// a dex register limit. The 16 incorporates callee save spills and
	// outgoing argument set up.
	const size_t kMaxExpectedFrameSize = 256 * sizeof(word) + 16;
	CHECK_LE(frame_size, kMaxExpectedFrameSize);
	size_t return_pc_offset = method->GetReturnPcOffsetInBytes();
	CHECK_LT(return_pc_offset, frame_size);
	}
	#endif
	}

	void StackVisitor::WalkStack(bool include_transitions) {
	DCHECK(thread_ == Thread::Current() \|\| thread_->IsSuspended());
	CHECK_EQ(cur_depth_, 0U);
	bool exit_stubs_installed = Runtime::Current()->GetInstrumentation()->AreExitStubsInstalled();
	uint32_t instrumentation_stack_depth = 0;
	for (const ManagedStack* current_fragment = thread_->GetManagedStack(); current_fragment != NULL;
	current_fragment = current_fragment->GetLink()) {
	cur_shadow_frame_ = current_fragment->GetTopShadowFrame();
	cur_quick_frame_ = current_fragment->GetTopQuickFrame();
	cur_quick_frame_pc_ = current_fragment->GetTopQuickFramePc();
	if (cur_quick_frame_ != NULL) { // Handle quick stack frames.
	// Can't be both a shadow and a quick fragment.
	DCHECK(current_fragment->GetTopShadowFrame() == NULL);
	mirror::ArtMethod* method = *cur_quick_frame_;
	while (method != NULL) {
	SanityCheckFrame();
	bool should_continue = VisitFrame();
	if (UNLIKELY(!should_continue)) {
	return;
	}
	if (context_ != NULL) {
	context_->FillCalleeSaves(*this);
	}
	size_t frame_size = method->GetFrameSizeInBytes();
	// Compute PC for next stack frame from return PC.
	size_t return_pc_offset = method->GetReturnPcOffsetInBytes();
	byte* return_pc_addr = reinterpret_cast<byte*>(cur_quick_frame_) + return_pc_offset;
	uintptr_t return_pc = reinterpret_cast<uintptr_t>(return_pc_addr);
	if (UNLIKELY(exit_stubs_installed)) {
	// While profiling, the return pc is restored from the side stack, except when walking
	// the stack for an exception where the side stack will be unwound in VisitFrame.
	if (GetQuickInstrumentationExitPc() == return_pc) {
	const instrumentation::InstrumentationStackFrame& instrumentation_frame =
	GetInstrumentationStackFrame(instrumentation_stack_depth);
	instrumentation_stack_depth++;
	if (GetMethod() == Runtime::Current()->GetCalleeSaveMethod(Runtime::kSaveAll)) {
	// Skip runtime save all callee frames which are used to deliver exceptions.
	} else if (instrumentation_frame.interpreter_entry_) {
	mirror::ArtMethod* callee = Runtime::Current()->GetCalleeSaveMethod(Runtime::kRefsAndArgs);
	CHECK_EQ(GetMethod(), callee) << "Expected: " << PrettyMethod(callee) << " Found: "
	<< PrettyMethod(GetMethod());
	} else if (instrumentation_frame.method_ != GetMethod()) {
	LOG(FATAL) << "Expected: " << PrettyMethod(instrumentation_frame.method_)
	<< " Found: " << PrettyMethod(GetMethod());
	}
	if (num_frames_ != 0) {
	// Check agreement of frame Ids only if num_frames_ is computed to avoid infinite
	// recursion.
	CHECK(instrumentation_frame.frame_id_ == GetFrameId())
	<< "Expected: " << instrumentation_frame.frame_id_
	<< " Found: " << GetFrameId();
	}
	return_pc = instrumentation_frame.return_pc_;
	}
	}
	cur_quick_frame_pc_ = return_pc;
	byte* next_frame = reinterpret_cast<byte*>(cur_quick_frame_) + frame_size;
	cur_quick_frame_ = reinterpret_cast<mirror::ArtMethod**>(next_frame);
	cur_depth_++;
	method = *cur_quick_frame_;
	}
	} else if (cur_shadow_frame_ != NULL) {
	do {
	SanityCheckFrame();
	bool should_continue = VisitFrame();
	if (UNLIKELY(!should_continue)) {
	return;
	}
	cur_depth_++;
	cur_shadow_frame_ = cur_shadow_frame_->GetLink();
	} while (cur_shadow_frame_ != NULL);
	}
	if (include_transitions) {
	bool should_continue = VisitFrame();
	if (!should_continue) {
	return;
	}
	}
	cur_depth_++;
	}
	if (num_frames_ != 0) {
	CHECK_EQ(cur_depth_, num_frames_);
	}
	}

	} // namespace art