compiler/dex/verified_method.cc - platform/art - Gitiles

 /*
  * Copyright (C) 2014 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 "verified_method.h"

 #include <algorithm>
 #include <memory>
 #include <vector>

 #include "base/logging.h"
 #include "base/stl_util.h"
 #include "dex_file.h"
 #include "dex_instruction.h"
 #include "dex_instruction-inl.h"
 #include "base/mutex.h"
 #include "base/mutex-inl.h"
 #include "mirror/art_method.h"
 #include "mirror/art_method-inl.h"
 #include "mirror/class.h"
 #include "mirror/class-inl.h"
 #include "mirror/dex_cache.h"
 #include "mirror/dex_cache-inl.h"
 #include "mirror/object.h"
 #include "mirror/object-inl.h"
 #include "verifier/dex_gc_map.h"
 #include "verifier/method_verifier.h"
 #include "verifier/method_verifier-inl.h"
 #include "verifier/reg_type-inl.h"
 #include "verifier/register_line-inl.h"

 namespace art {

 const VerifiedMethod* VerifiedMethod::Create(verifier::MethodVerifier* method_verifier,
                                              bool compile) {
   std::unique_ptr<VerifiedMethod> verified_method(new VerifiedMethod);
   if (compile) {
     /* Generate a register map. */
     if (!verified_method->GenerateGcMap(method_verifier)) {
       CHECK(method_verifier->HasFailures());
       return nullptr;  // Not a real failure, but a failure to encode.
     }
     if (kIsDebugBuild) {
       VerifyGcMap(method_verifier, verified_method->dex_gc_map_);
     }

     // TODO: move this out when DEX-to-DEX supports devirtualization.
     if (method_verifier->HasVirtualOrInterfaceInvokes()) {
       verified_method->GenerateDevirtMap(method_verifier);
     }
   }

   if (method_verifier->HasCheckCasts()) {
     verified_method->GenerateSafeCastSet(method_verifier);
   }
   return verified_method.release();
 }

 const MethodReference* VerifiedMethod::GetDevirtTarget(uint32_t dex_pc) const {
   auto it = devirt_map_.find(dex_pc);
   return (it != devirt_map_.end()) ? &it->second : nullptr;
 }

 bool VerifiedMethod::IsSafeCast(uint32_t pc) const {
   return std::binary_search(safe_cast_set_.begin(), safe_cast_set_.end(), pc);
 }

 bool VerifiedMethod::GenerateGcMap(verifier::MethodVerifier* method_verifier) {
   DCHECK(dex_gc_map_.empty());
   size_t num_entries, ref_bitmap_bits, pc_bits;
   ComputeGcMapSizes(method_verifier, &num_entries, &ref_bitmap_bits, &pc_bits);
   // There's a single byte to encode the size of each bitmap.
   if (ref_bitmap_bits >= (8 /* bits per byte */ * 8192 /* 13-bit size */ )) {
     // TODO: either a better GC map format or per method failures
     method_verifier->Fail(verifier::VERIFY_ERROR_BAD_CLASS_HARD)
         << "Cannot encode GC map for method with " << ref_bitmap_bits << " registers";
     return false;
   }
   size_t ref_bitmap_bytes = (ref_bitmap_bits + 7) / 8;
   // There are 2 bytes to encode the number of entries.
   if (num_entries >= 65536) {
     // TODO: Either a better GC map format or per method failures.
     method_verifier->Fail(verifier::VERIFY_ERROR_BAD_CLASS_HARD)
         << "Cannot encode GC map for method with " << num_entries << " entries";
     return false;
   }
   size_t pc_bytes;
   verifier::RegisterMapFormat format;
   if (pc_bits <= 8) {
     format = verifier::kRegMapFormatCompact8;
     pc_bytes = 1;
   } else if (pc_bits <= 16) {
     format = verifier::kRegMapFormatCompact16;
     pc_bytes = 2;
   } else {
     // TODO: Either a better GC map format or per method failures.
     method_verifier->Fail(verifier::VERIFY_ERROR_BAD_CLASS_HARD)
         << "Cannot encode GC map for method with "
         << (1 << pc_bits) << " instructions (number is rounded up to nearest power of 2)";
     return false;
   }
   size_t table_size = ((pc_bytes + ref_bitmap_bytes) * num_entries) + 4;
   dex_gc_map_.reserve(table_size);
   // Write table header.
   dex_gc_map_.push_back(format | ((ref_bitmap_bytes & ~0xFF) >> 5));
   dex_gc_map_.push_back(ref_bitmap_bytes & 0xFF);
   dex_gc_map_.push_back(num_entries & 0xFF);
   dex_gc_map_.push_back((num_entries >> 8) & 0xFF);
   // Write table data.
   const DexFile::CodeItem* code_item = method_verifier->CodeItem();
   for (size_t i = 0; i < code_item->insns_size_in_code_units_; i++) {
     if (method_verifier->GetInstructionFlags(i).IsCompileTimeInfoPoint()) {
       dex_gc_map_.push_back(i & 0xFF);
       if (pc_bytes == 2) {
         dex_gc_map_.push_back((i >> 8) & 0xFF);
       }
       verifier::RegisterLine* line = method_verifier->GetRegLine(i);
       line->WriteReferenceBitMap(method_verifier, &dex_gc_map_, ref_bitmap_bytes);
     }
   }
   DCHECK_EQ(dex_gc_map_.size(), table_size);
   return true;
 }

 void VerifiedMethod::VerifyGcMap(verifier::MethodVerifier* method_verifier,
                                  const std::vector<uint8_t>& data) {
   // Check that for every GC point there is a map entry, there aren't entries for non-GC points,
   // that the table data is well formed and all references are marked (or not) in the bitmap.
   verifier::DexPcToReferenceMap map(&data[0]);
   DCHECK_EQ(data.size(), map.RawSize());
   size_t map_index = 0;
   const DexFile::CodeItem* code_item = method_verifier->CodeItem();
   for (size_t i = 0; i < code_item->insns_size_in_code_units_; i++) {
     const uint8_t* reg_bitmap = map.FindBitMap(i, false);
     if (method_verifier->GetInstructionFlags(i).IsCompileTimeInfoPoint()) {
       DCHECK_LT(map_index, map.NumEntries());
       DCHECK_EQ(map.GetDexPc(map_index), i);
       DCHECK_EQ(map.GetBitMap(map_index), reg_bitmap);
       map_index++;
       verifier::RegisterLine* line = method_verifier->GetRegLine(i);
       for (size_t j = 0; j < code_item->registers_size_; j++) {
         if (line->GetRegisterType(method_verifier, j).IsNonZeroReferenceTypes()) {
           DCHECK_LT(j / 8, map.RegWidth());
           DCHECK_EQ((reg_bitmap[j / 8] >> (j % 8)) & 1, 1);
         } else if ((j / 8) < map.RegWidth()) {
           DCHECK_EQ((reg_bitmap[j / 8] >> (j % 8)) & 1, 0);
         } else {
           // If a register doesn't contain a reference then the bitmap may be shorter than the line.
         }
       }
     } else {
       DCHECK(reg_bitmap == NULL);
     }
   }
 }

 void VerifiedMethod::ComputeGcMapSizes(verifier::MethodVerifier* method_verifier,
                                        size_t* gc_points, size_t* ref_bitmap_bits,
                                        size_t* log2_max_gc_pc) {
   size_t local_gc_points = 0;
   size_t max_insn = 0;
   size_t max_ref_reg = -1;
   const DexFile::CodeItem* code_item = method_verifier->CodeItem();
   for (size_t i = 0; i < code_item->insns_size_in_code_units_; i++) {
     if (method_verifier->GetInstructionFlags(i).IsCompileTimeInfoPoint()) {
       local_gc_points++;
       max_insn = i;
       verifier::RegisterLine* line = method_verifier->GetRegLine(i);
       max_ref_reg = line->GetMaxNonZeroReferenceReg(method_verifier, max_ref_reg);
     }
   }
   *gc_points = local_gc_points;
   *ref_bitmap_bits = max_ref_reg + 1;  // If max register is 0 we need 1 bit to encode (ie +1).
   size_t i = 0;
   while ((1U << i) <= max_insn) {
     i++;
   }
   *log2_max_gc_pc = i;
 }

 void VerifiedMethod::GenerateDevirtMap(verifier::MethodVerifier* method_verifier) {
   // It is risky to rely on reg_types for sharpening in cases of soft
   // verification, we might end up sharpening to a wrong implementation. Just abort.
   if (method_verifier->HasFailures()) {
     return;
   }

   const DexFile::CodeItem* code_item = method_verifier->CodeItem();
   const uint16_t* insns = code_item->insns_;
   const Instruction* inst = Instruction::At(insns);
   const Instruction* end = Instruction::At(insns + code_item->insns_size_in_code_units_);

   for (; inst < end; inst = inst->Next()) {
     bool is_virtual   = (inst->Opcode() == Instruction::INVOKE_VIRTUAL) ||
         (inst->Opcode() ==  Instruction::INVOKE_VIRTUAL_RANGE);
     bool is_interface = (inst->Opcode() == Instruction::INVOKE_INTERFACE) ||
         (inst->Opcode() == Instruction::INVOKE_INTERFACE_RANGE);

     if (!is_interface && !is_virtual) {
       continue;
     }
     // Get reg type for register holding the reference to the object that will be dispatched upon.
     uint32_t dex_pc = inst->GetDexPc(insns);
     verifier::RegisterLine* line = method_verifier->GetRegLine(dex_pc);
     bool is_range = (inst->Opcode() ==  Instruction::INVOKE_VIRTUAL_RANGE) ||
         (inst->Opcode() ==  Instruction::INVOKE_INTERFACE_RANGE);
     const verifier::RegType&
         reg_type(line->GetRegisterType(method_verifier,
                                        is_range ? inst->VRegC_3rc() : inst->VRegC_35c()));

     if (!reg_type.HasClass()) {
       // We will compute devirtualization information only when we know the Class of the reg type.
       continue;
     }
     mirror::Class* reg_class = reg_type.GetClass();
     if (reg_class->IsInterface()) {
       // We can't devirtualize when the known type of the register is an interface.
       continue;
     }
     if (reg_class->IsAbstract() && !reg_class->IsArrayClass()) {
       // We can't devirtualize abstract classes except on arrays of abstract classes.
       continue;
     }
     mirror::ArtMethod* abstract_method = method_verifier->GetDexCache()->GetResolvedMethod(
         is_range ? inst->VRegB_3rc() : inst->VRegB_35c());
     if (abstract_method == NULL) {
       // If the method is not found in the cache this means that it was never found
       // by ResolveMethodAndCheckAccess() called when verifying invoke_*.
       continue;
     }
     // Find the concrete method.
     mirror::ArtMethod* concrete_method = NULL;
     if (is_interface) {
       concrete_method = reg_type.GetClass()->FindVirtualMethodForInterface(abstract_method);
     }
     if (is_virtual) {
       concrete_method = reg_type.GetClass()->FindVirtualMethodForVirtual(abstract_method);
     }
     if (concrete_method == NULL || concrete_method->IsAbstract()) {
       // In cases where concrete_method is not found, or is abstract, continue to the next invoke.
       continue;
     }
     if (reg_type.IsPreciseReference() || concrete_method->IsFinal() ||
         concrete_method->GetDeclaringClass()->IsFinal()) {
       // If we knew exactly the class being dispatched upon, or if the target method cannot be
       // overridden record the target to be used in the compiler driver.
       MethodReference concrete_ref(
           concrete_method->GetDeclaringClass()->GetDexCache()->GetDexFile(),
           concrete_method->GetDexMethodIndex());
       devirt_map_.Put(dex_pc, concrete_ref);
     }
   }
 }

 void VerifiedMethod::GenerateSafeCastSet(verifier::MethodVerifier* method_verifier) {
   /*
    * Walks over the method code and adds any cast instructions in which
    * the type cast is implicit to a set, which is used in the code generation
    * to elide these casts.
    */
   if (method_verifier->HasFailures()) {
     return;
   }
   const DexFile::CodeItem* code_item = method_verifier->CodeItem();
   const Instruction* inst = Instruction::At(code_item->insns_);
   const Instruction* end = Instruction::At(code_item->insns_ +
                                            code_item->insns_size_in_code_units_);

   for (; inst < end; inst = inst->Next()) {
     Instruction::Code code = inst->Opcode();
     if ((code == Instruction::CHECK_CAST) || (code == Instruction::APUT_OBJECT)) {
       uint32_t dex_pc = inst->GetDexPc(code_item->insns_);
       const verifier::RegisterLine* line = method_verifier->GetRegLine(dex_pc);
       bool is_safe_cast = false;
       if (code == Instruction::CHECK_CAST) {
         const verifier::RegType& reg_type(line->GetRegisterType(method_verifier,
                                                                 inst->VRegA_21c()));
         const verifier::RegType& cast_type =
             method_verifier->ResolveCheckedClass(inst->VRegB_21c());
         is_safe_cast = cast_type.IsStrictlyAssignableFrom(reg_type);
       } else {
         const verifier::RegType& array_type(line->GetRegisterType(method_verifier,
                                                                   inst->VRegB_23x()));
         // We only know its safe to assign to an array if the array type is precise. For example,
         // an Object[] can have any type of object stored in it, but it may also be assigned a
         // String[] in which case the stores need to be of Strings.
         if (array_type.IsPreciseReference()) {
           const verifier::RegType& value_type(line->GetRegisterType(method_verifier,
                                                                     inst->VRegA_23x()));
           const verifier::RegType& component_type = method_verifier->GetRegTypeCache()
               ->GetComponentType(array_type, method_verifier->GetClassLoader());
           is_safe_cast = component_type.IsStrictlyAssignableFrom(value_type);
         }
       }
       if (is_safe_cast) {
         // Verify ordering for push_back() to the sorted vector.
         DCHECK(safe_cast_set_.empty() || safe_cast_set_.back() < dex_pc);
         safe_cast_set_.push_back(dex_pc);
       }
     }
   }
 }

 }  // namespace art
	/*
	* Copyright (C) 2014 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 "verified_method.h"

	#include <algorithm>
	#include <memory>
	#include <vector>

	#include "base/logging.h"
	#include "base/stl_util.h"
	#include "dex_file.h"
	#include "dex_instruction.h"
	#include "dex_instruction-inl.h"
	#include "base/mutex.h"
	#include "base/mutex-inl.h"
	#include "mirror/art_method.h"
	#include "mirror/art_method-inl.h"
	#include "mirror/class.h"
	#include "mirror/class-inl.h"
	#include "mirror/dex_cache.h"
	#include "mirror/dex_cache-inl.h"
	#include "mirror/object.h"
	#include "mirror/object-inl.h"
	#include "verifier/dex_gc_map.h"
	#include "verifier/method_verifier.h"
	#include "verifier/method_verifier-inl.h"
	#include "verifier/reg_type-inl.h"
	#include "verifier/register_line-inl.h"

	namespace art {

	const VerifiedMethod* VerifiedMethod::Create(verifier::MethodVerifier* method_verifier,
	bool compile) {
	std::unique_ptr<VerifiedMethod> verified_method(new VerifiedMethod);
	if (compile) {
	/* Generate a register map. */
	if (!verified_method->GenerateGcMap(method_verifier)) {
	CHECK(method_verifier->HasFailures());
	return nullptr; // Not a real failure, but a failure to encode.
	}
	if (kIsDebugBuild) {
	VerifyGcMap(method_verifier, verified_method->dex_gc_map_);
	}

	// TODO: move this out when DEX-to-DEX supports devirtualization.
	if (method_verifier->HasVirtualOrInterfaceInvokes()) {
	verified_method->GenerateDevirtMap(method_verifier);
	}
	}

	if (method_verifier->HasCheckCasts()) {
	verified_method->GenerateSafeCastSet(method_verifier);
	}
	return verified_method.release();
	}

	const MethodReference* VerifiedMethod::GetDevirtTarget(uint32_t dex_pc) const {
	auto it = devirt_map_.find(dex_pc);
	return (it != devirt_map_.end()) ? &it->second : nullptr;
	}

	bool VerifiedMethod::IsSafeCast(uint32_t pc) const {
	return std::binary_search(safe_cast_set_.begin(), safe_cast_set_.end(), pc);
	}

	bool VerifiedMethod::GenerateGcMap(verifier::MethodVerifier* method_verifier) {
	DCHECK(dex_gc_map_.empty());
	size_t num_entries, ref_bitmap_bits, pc_bits;
	ComputeGcMapSizes(method_verifier, &num_entries, &ref_bitmap_bits, &pc_bits);
	// There's a single byte to encode the size of each bitmap.
	if (ref_bitmap_bits >= (8 /* bits per byte / 8192 /* 13-bit size */ )) {
	// TODO: either a better GC map format or per method failures
	method_verifier->Fail(verifier::VERIFY_ERROR_BAD_CLASS_HARD)
	<< "Cannot encode GC map for method with " << ref_bitmap_bits << " registers";
	return false;
	}
	size_t ref_bitmap_bytes = (ref_bitmap_bits + 7) / 8;
	// There are 2 bytes to encode the number of entries.
	if (num_entries >= 65536) {
	// TODO: Either a better GC map format or per method failures.
	method_verifier->Fail(verifier::VERIFY_ERROR_BAD_CLASS_HARD)
	<< "Cannot encode GC map for method with " << num_entries << " entries";
	return false;
	}
	size_t pc_bytes;
	verifier::RegisterMapFormat format;
	if (pc_bits <= 8) {
	format = verifier::kRegMapFormatCompact8;
	pc_bytes = 1;
	} else if (pc_bits <= 16) {
	format = verifier::kRegMapFormatCompact16;
	pc_bytes = 2;
	} else {
	// TODO: Either a better GC map format or per method failures.
	method_verifier->Fail(verifier::VERIFY_ERROR_BAD_CLASS_HARD)
	<< "Cannot encode GC map for method with "
	<< (1 << pc_bits) << " instructions (number is rounded up to nearest power of 2)";
	return false;
	}
	size_t table_size = ((pc_bytes + ref_bitmap_bytes) * num_entries) + 4;
	dex_gc_map_.reserve(table_size);
	// Write table header.
	dex_gc_map_.push_back(format \| ((ref_bitmap_bytes & ~0xFF) >> 5));
	dex_gc_map_.push_back(ref_bitmap_bytes & 0xFF);
	dex_gc_map_.push_back(num_entries & 0xFF);
	dex_gc_map_.push_back((num_entries >> 8) & 0xFF);
	// Write table data.
	const DexFile::CodeItem* code_item = method_verifier->CodeItem();
	for (size_t i = 0; i < code_item->insns_size_in_code_units_; i++) {
	if (method_verifier->GetInstructionFlags(i).IsCompileTimeInfoPoint()) {
	dex_gc_map_.push_back(i & 0xFF);
	if (pc_bytes == 2) {
	dex_gc_map_.push_back((i >> 8) & 0xFF);
	}
	verifier::RegisterLine* line = method_verifier->GetRegLine(i);
	line->WriteReferenceBitMap(method_verifier, &dex_gc_map_, ref_bitmap_bytes);
	}
	}
	DCHECK_EQ(dex_gc_map_.size(), table_size);
	return true;
	}

	void VerifiedMethod::VerifyGcMap(verifier::MethodVerifier* method_verifier,
	const std::vector<uint8_t>& data) {
	// Check that for every GC point there is a map entry, there aren't entries for non-GC points,
	// that the table data is well formed and all references are marked (or not) in the bitmap.
	verifier::DexPcToReferenceMap map(&data[0]);
	DCHECK_EQ(data.size(), map.RawSize());
	size_t map_index = 0;
	const DexFile::CodeItem* code_item = method_verifier->CodeItem();
	for (size_t i = 0; i < code_item->insns_size_in_code_units_; i++) {
	const uint8_t* reg_bitmap = map.FindBitMap(i, false);
	if (method_verifier->GetInstructionFlags(i).IsCompileTimeInfoPoint()) {
	DCHECK_LT(map_index, map.NumEntries());
	DCHECK_EQ(map.GetDexPc(map_index), i);
	DCHECK_EQ(map.GetBitMap(map_index), reg_bitmap);
	map_index++;
	verifier::RegisterLine* line = method_verifier->GetRegLine(i);
	for (size_t j = 0; j < code_item->registers_size_; j++) {
	if (line->GetRegisterType(method_verifier, j).IsNonZeroReferenceTypes()) {
	DCHECK_LT(j / 8, map.RegWidth());
	DCHECK_EQ((reg_bitmap[j / 8] >> (j % 8)) & 1, 1);
	} else if ((j / 8) < map.RegWidth()) {
	DCHECK_EQ((reg_bitmap[j / 8] >> (j % 8)) & 1, 0);
	} else {
	// If a register doesn't contain a reference then the bitmap may be shorter than the line.
	}
	}
	} else {
	DCHECK(reg_bitmap == NULL);
	}
	}
	}

	void VerifiedMethod::ComputeGcMapSizes(verifier::MethodVerifier* method_verifier,
	size_t* gc_points, size_t* ref_bitmap_bits,
	size_t* log2_max_gc_pc) {
	size_t local_gc_points = 0;
	size_t max_insn = 0;
	size_t max_ref_reg = -1;
	const DexFile::CodeItem* code_item = method_verifier->CodeItem();
	for (size_t i = 0; i < code_item->insns_size_in_code_units_; i++) {
	if (method_verifier->GetInstructionFlags(i).IsCompileTimeInfoPoint()) {
	local_gc_points++;
	max_insn = i;
	verifier::RegisterLine* line = method_verifier->GetRegLine(i);
	max_ref_reg = line->GetMaxNonZeroReferenceReg(method_verifier, max_ref_reg);
	}
	}
	*gc_points = local_gc_points;
	*ref_bitmap_bits = max_ref_reg + 1; // If max register is 0 we need 1 bit to encode (ie +1).
	size_t i = 0;
	while ((1U << i) <= max_insn) {
	i++;
	}
	*log2_max_gc_pc = i;
	}

	void VerifiedMethod::GenerateDevirtMap(verifier::MethodVerifier* method_verifier) {
	// It is risky to rely on reg_types for sharpening in cases of soft
	// verification, we might end up sharpening to a wrong implementation. Just abort.
	if (method_verifier->HasFailures()) {
	return;
	}

	const DexFile::CodeItem* code_item = method_verifier->CodeItem();
	const uint16_t* insns = code_item->insns_;
	const Instruction* inst = Instruction::At(insns);
	const Instruction* end = Instruction::At(insns + code_item->insns_size_in_code_units_);

	for (; inst < end; inst = inst->Next()) {
	bool is_virtual = (inst->Opcode() == Instruction::INVOKE_VIRTUAL) \|\|
	(inst->Opcode() == Instruction::INVOKE_VIRTUAL_RANGE);
	bool is_interface = (inst->Opcode() == Instruction::INVOKE_INTERFACE) \|\|
	(inst->Opcode() == Instruction::INVOKE_INTERFACE_RANGE);

	if (!is_interface && !is_virtual) {
	continue;
	}
	// Get reg type for register holding the reference to the object that will be dispatched upon.
	uint32_t dex_pc = inst->GetDexPc(insns);
	verifier::RegisterLine* line = method_verifier->GetRegLine(dex_pc);
	bool is_range = (inst->Opcode() == Instruction::INVOKE_VIRTUAL_RANGE) \|\|
	(inst->Opcode() == Instruction::INVOKE_INTERFACE_RANGE);
	const verifier::RegType&
	reg_type(line->GetRegisterType(method_verifier,
	is_range ? inst->VRegC_3rc() : inst->VRegC_35c()));

	if (!reg_type.HasClass()) {
	// We will compute devirtualization information only when we know the Class of the reg type.
	continue;
	}
	mirror::Class* reg_class = reg_type.GetClass();
	if (reg_class->IsInterface()) {
	// We can't devirtualize when the known type of the register is an interface.
	continue;
	}
	if (reg_class->IsAbstract() && !reg_class->IsArrayClass()) {
	// We can't devirtualize abstract classes except on arrays of abstract classes.
	continue;
	}
	mirror::ArtMethod* abstract_method = method_verifier->GetDexCache()->GetResolvedMethod(
	is_range ? inst->VRegB_3rc() : inst->VRegB_35c());
	if (abstract_method == NULL) {
	// If the method is not found in the cache this means that it was never found
	// by ResolveMethodAndCheckAccess() called when verifying invoke_*.
	continue;
	}
	// Find the concrete method.
	mirror::ArtMethod* concrete_method = NULL;
	if (is_interface) {
	concrete_method = reg_type.GetClass()->FindVirtualMethodForInterface(abstract_method);
	}
	if (is_virtual) {
	concrete_method = reg_type.GetClass()->FindVirtualMethodForVirtual(abstract_method);
	}
	if (concrete_method == NULL \|\| concrete_method->IsAbstract()) {
	// In cases where concrete_method is not found, or is abstract, continue to the next invoke.
	continue;
	}
	if (reg_type.IsPreciseReference() \|\| concrete_method->IsFinal() \|\|
	concrete_method->GetDeclaringClass()->IsFinal()) {
	// If we knew exactly the class being dispatched upon, or if the target method cannot be
	// overridden record the target to be used in the compiler driver.
	MethodReference concrete_ref(
	concrete_method->GetDeclaringClass()->GetDexCache()->GetDexFile(),
	concrete_method->GetDexMethodIndex());
	devirt_map_.Put(dex_pc, concrete_ref);
	}
	}
	}

	void VerifiedMethod::GenerateSafeCastSet(verifier::MethodVerifier* method_verifier) {
	/*
	* Walks over the method code and adds any cast instructions in which
	* the type cast is implicit to a set, which is used in the code generation
	* to elide these casts.
	*/
	if (method_verifier->HasFailures()) {
	return;
	}
	const DexFile::CodeItem* code_item = method_verifier->CodeItem();
	const Instruction* inst = Instruction::At(code_item->insns_);
	const Instruction* end = Instruction::At(code_item->insns_ +
	code_item->insns_size_in_code_units_);

	for (; inst < end; inst = inst->Next()) {
	Instruction::Code code = inst->Opcode();
	if ((code == Instruction::CHECK_CAST) \|\| (code == Instruction::APUT_OBJECT)) {
	uint32_t dex_pc = inst->GetDexPc(code_item->insns_);
	const verifier::RegisterLine* line = method_verifier->GetRegLine(dex_pc);
	bool is_safe_cast = false;
	if (code == Instruction::CHECK_CAST) {
	const verifier::RegType& reg_type(line->GetRegisterType(method_verifier,
	inst->VRegA_21c()));
	const verifier::RegType& cast_type =
	method_verifier->ResolveCheckedClass(inst->VRegB_21c());
	is_safe_cast = cast_type.IsStrictlyAssignableFrom(reg_type);
	} else {
	const verifier::RegType& array_type(line->GetRegisterType(method_verifier,
	inst->VRegB_23x()));
	// We only know its safe to assign to an array if the array type is precise. For example,
	// an Object[] can have any type of object stored in it, but it may also be assigned a
	// String[] in which case the stores need to be of Strings.
	if (array_type.IsPreciseReference()) {
	const verifier::RegType& value_type(line->GetRegisterType(method_verifier,
	inst->VRegA_23x()));
	const verifier::RegType& component_type = method_verifier->GetRegTypeCache()
	->GetComponentType(array_type, method_verifier->GetClassLoader());
	is_safe_cast = component_type.IsStrictlyAssignableFrom(value_type);
	}
	}
	if (is_safe_cast) {
	// Verify ordering for push_back() to the sorted vector.
	DCHECK(safe_cast_set_.empty() \|\| safe_cast_set_.back() < dex_pc);
	safe_cast_set_.push_back(dex_pc);
	}
	}
	}
	}

	} // namespace art