compiler/elf_writer_debug.cc - platform/art - Gitiles

 /*
  * Copyright (C) 2015 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 "elf_writer_debug.h"

 #include <unordered_set>

 #include "compiled_method.h"
 #include "driver/compiler_driver.h"
 #include "dex_file-inl.h"
 #include "dwarf/headers.h"
 #include "dwarf/register.h"
 #include "oat_writer.h"

 namespace art {
 namespace dwarf {

 static void WriteEhFrameCIE(InstructionSet isa,
                             ExceptionHeaderValueApplication addr_type,
                             std::vector<uint8_t>* eh_frame) {
   // Scratch registers should be marked as undefined.  This tells the
   // debugger that its value in the previous frame is not recoverable.
   bool is64bit = Is64BitInstructionSet(isa);
   switch (isa) {
     case kArm:
     case kThumb2: {
       DebugFrameOpCodeWriter<> opcodes;
       opcodes.DefCFA(Reg::ArmCore(13), 0);  // R13(SP).
       // core registers.
       for (int reg = 0; reg < 13; reg++) {
         if (reg < 4 || reg == 12) {
           opcodes.Undefined(Reg::ArmCore(reg));
         } else {
           opcodes.SameValue(Reg::ArmCore(reg));
         }
       }
       // fp registers.
       for (int reg = 0; reg < 32; reg++) {
         if (reg < 16) {
           opcodes.Undefined(Reg::ArmFp(reg));
         } else {
           opcodes.SameValue(Reg::ArmFp(reg));
         }
       }
       auto return_reg = Reg::ArmCore(14);  // R14(LR).
       WriteEhFrameCIE(is64bit, addr_type, return_reg, opcodes, eh_frame);
       return;
     }
     case kArm64: {
       DebugFrameOpCodeWriter<> opcodes;
       opcodes.DefCFA(Reg::Arm64Core(31), 0);  // R31(SP).
       // core registers.
       for (int reg = 0; reg < 30; reg++) {
         if (reg < 8 || reg == 16 || reg == 17) {
           opcodes.Undefined(Reg::Arm64Core(reg));
         } else {
           opcodes.SameValue(Reg::Arm64Core(reg));
         }
       }
       // fp registers.
       for (int reg = 0; reg < 32; reg++) {
         if (reg < 8 || reg >= 16) {
           opcodes.Undefined(Reg::Arm64Fp(reg));
         } else {
           opcodes.SameValue(Reg::Arm64Fp(reg));
         }
       }
       auto return_reg = Reg::Arm64Core(30);  // R30(LR).
       WriteEhFrameCIE(is64bit, addr_type, return_reg, opcodes, eh_frame);
       return;
     }
     case kMips:
     case kMips64: {
       DebugFrameOpCodeWriter<> opcodes;
       opcodes.DefCFA(Reg::MipsCore(29), 0);  // R29(SP).
       // core registers.
       for (int reg = 1; reg < 26; reg++) {
         if (reg < 16 || reg == 24 || reg == 25) {  // AT, V*, A*, T*.
           opcodes.Undefined(Reg::MipsCore(reg));
         } else {
           opcodes.SameValue(Reg::MipsCore(reg));
         }
       }
       auto return_reg = Reg::MipsCore(31);  // R31(RA).
       WriteEhFrameCIE(is64bit, addr_type, return_reg, opcodes, eh_frame);
       return;
     }
     case kX86: {
       // FIXME: Add fp registers once libunwind adds support for them. Bug: 20491296
       constexpr bool generate_opcodes_for_x86_fp = false;
       DebugFrameOpCodeWriter<> opcodes;
       opcodes.DefCFA(Reg::X86Core(4), 4);   // R4(ESP).
       opcodes.Offset(Reg::X86Core(8), -4);  // R8(EIP).
       // core registers.
       for (int reg = 0; reg < 8; reg++) {
         if (reg <= 3) {
           opcodes.Undefined(Reg::X86Core(reg));
         } else if (reg == 4) {
           // Stack pointer.
         } else {
           opcodes.SameValue(Reg::X86Core(reg));
         }
       }
       // fp registers.
       if (generate_opcodes_for_x86_fp) {
         for (int reg = 0; reg < 8; reg++) {
           opcodes.Undefined(Reg::X86Fp(reg));
         }
       }
       auto return_reg = Reg::X86Core(8);  // R8(EIP).
       WriteEhFrameCIE(is64bit, addr_type, return_reg, opcodes, eh_frame);
       return;
     }
     case kX86_64: {
       DebugFrameOpCodeWriter<> opcodes;
       opcodes.DefCFA(Reg::X86_64Core(4), 8);  // R4(RSP).
       opcodes.Offset(Reg::X86_64Core(16), -8);  // R16(RIP).
       // core registers.
       for (int reg = 0; reg < 16; reg++) {
         if (reg == 4) {
           // Stack pointer.
         } else if (reg < 12 && reg != 3 && reg != 5) {  // except EBX and EBP.
           opcodes.Undefined(Reg::X86_64Core(reg));
         } else {
           opcodes.SameValue(Reg::X86_64Core(reg));
         }
       }
       // fp registers.
       for (int reg = 0; reg < 16; reg++) {
         if (reg < 12) {
           opcodes.Undefined(Reg::X86_64Fp(reg));
         } else {
           opcodes.SameValue(Reg::X86_64Fp(reg));
         }
       }
       auto return_reg = Reg::X86_64Core(16);  // R16(RIP).
       WriteEhFrameCIE(is64bit, addr_type, return_reg, opcodes, eh_frame);
       return;
     }
     case kNone:
       break;
   }
   LOG(FATAL) << "Can not write CIE frame for ISA " << isa;
   UNREACHABLE();
 }

 void WriteEhFrame(const CompilerDriver* compiler,
                   const OatWriter* oat_writer,
                   ExceptionHeaderValueApplication address_type,
                   std::vector<uint8_t>* eh_frame,
                   std::vector<uintptr_t>* eh_frame_patches,
                   std::vector<uint8_t>* eh_frame_hdr) {
   const auto& method_infos = oat_writer->GetMethodDebugInfo();
   const InstructionSet isa = compiler->GetInstructionSet();

   // Write .eh_frame section.
   size_t cie_offset = eh_frame->size();
   WriteEhFrameCIE(isa, address_type, eh_frame);
   for (const OatWriter::DebugInfo& mi : method_infos) {
     const SwapVector<uint8_t>* opcodes = mi.compiled_method_->GetCFIInfo();
     if (opcodes != nullptr) {
       WriteEhFrameFDE(Is64BitInstructionSet(isa), cie_offset,
                       mi.low_pc_, mi.high_pc_ - mi.low_pc_,
                       opcodes, eh_frame, eh_frame_patches);
     }
   }

   // Write .eh_frame_hdr section.
   Writer<> header(eh_frame_hdr);
   header.PushUint8(1);  // Version.
   header.PushUint8(DW_EH_PE_pcrel | DW_EH_PE_sdata4);  // Encoding of .eh_frame pointer.
   header.PushUint8(DW_EH_PE_omit);  // Encoding of binary search table size.
   header.PushUint8(DW_EH_PE_omit);  // Encoding of binary search table addresses.
   // .eh_frame pointer - .eh_frame_hdr section is after .eh_frame section, and need to encode
   // relative to this location as libunwind doesn't honor datarel for eh_frame_hdr correctly.
   header.PushInt32(-static_cast<int32_t>(eh_frame->size() + 4U));
   // Omit binary search table size (number of entries).
   // Omit binary search table.
 }

 /*
  * @brief Generate the DWARF sections.
  * @param oat_writer The Oat file Writer.
  * @param eh_frame Call Frame Information.
  * @param debug_info Compilation unit information.
  * @param debug_info_patches Address locations to be patched.
  * @param debug_abbrev Abbreviations used to generate dbg_info.
  * @param debug_str Debug strings.
  * @param debug_line Line number table.
  * @param debug_line_patches Address locations to be patched.
  */
 void WriteDebugSections(const CompilerDriver* compiler,
                         const OatWriter* oat_writer,
                         std::vector<uint8_t>* debug_info,
                         std::vector<uintptr_t>* debug_info_patches,
                         std::vector<uint8_t>* debug_abbrev,
                         std::vector<uint8_t>* debug_str,
                         std::vector<uint8_t>* debug_line,
                         std::vector<uintptr_t>* debug_line_patches) {
   const std::vector<OatWriter::DebugInfo>& method_infos = oat_writer->GetMethodDebugInfo();
   const InstructionSet isa = compiler->GetInstructionSet();

   // Find all addresses (low_pc) which contain deduped methods.
   // The first instance of method is not marked deduped_, but the rest is.
   std::unordered_set<uint32_t> deduped_addresses;
   for (auto it = method_infos.begin(); it != method_infos.end(); ++it) {
     if (it->deduped_) {
       deduped_addresses.insert(it->low_pc_);
     }
   }

   // Group the methods into compilation units based on source file.
   std::vector<std::vector<const OatWriter::DebugInfo*>> compilation_units;
   const char* last_source_file = nullptr;
   for (const auto& mi : method_infos) {
     // Attribute given instruction range only to single method.
     // Otherwise the debugger might get really confused.
     if (!mi.deduped_) {
       auto& dex_class_def = mi.dex_file_->GetClassDef(mi.class_def_index_);
       const char* source_file = mi.dex_file_->GetSourceFile(dex_class_def);
       if (compilation_units.empty() || source_file != last_source_file) {
         compilation_units.push_back(std::vector<const OatWriter::DebugInfo*>());
       }
       compilation_units.back().push_back(&mi);
       last_source_file = source_file;
     }
   }

   // Write .debug_info section.
   for (const auto& compilation_unit : compilation_units) {
     uint32_t cunit_low_pc = 0xFFFFFFFFU;
     uint32_t cunit_high_pc = 0;
     for (auto method_info : compilation_unit) {
       cunit_low_pc = std::min(cunit_low_pc, method_info->low_pc_);
       cunit_high_pc = std::max(cunit_high_pc, method_info->high_pc_);
     }

     size_t debug_abbrev_offset = debug_abbrev->size();
     DebugInfoEntryWriter<> info(false /* 32 bit */, debug_abbrev);
     info.StartTag(DW_TAG_compile_unit, DW_CHILDREN_yes);
     info.WriteStrp(DW_AT_producer, "Android dex2oat", debug_str);
     info.WriteData1(DW_AT_language, DW_LANG_Java);
     info.WriteAddr(DW_AT_low_pc, cunit_low_pc);
     info.WriteAddr(DW_AT_high_pc, cunit_high_pc);
     info.WriteData4(DW_AT_stmt_list, debug_line->size());
     for (auto method_info : compilation_unit) {
       std::string method_name = PrettyMethod(method_info->dex_method_index_,
                                              *method_info->dex_file_, true);
       if (deduped_addresses.find(method_info->low_pc_) != deduped_addresses.end()) {
         method_name += " [DEDUPED]";
       }
       info.StartTag(DW_TAG_subprogram, DW_CHILDREN_no);
       info.WriteStrp(DW_AT_name, method_name.data(), debug_str);
       info.WriteAddr(DW_AT_low_pc, method_info->low_pc_);
       info.WriteAddr(DW_AT_high_pc, method_info->high_pc_);
       info.EndTag();  // DW_TAG_subprogram
     }
     info.EndTag();  // DW_TAG_compile_unit
     WriteDebugInfoCU(debug_abbrev_offset, info, debug_info, debug_info_patches);

     // Write .debug_line section.
     std::vector<FileEntry> files;
     std::unordered_map<std::string, size_t> files_map;
     std::vector<std::string> directories;
     std::unordered_map<std::string, size_t> directories_map;
     int code_factor_bits_ = 0;
     int dwarf_isa = -1;
     switch (isa) {
       case kArm:  // arm actually means thumb2.
       case kThumb2:
         code_factor_bits_ = 1;  // 16-bit instuctions
         dwarf_isa = 1;  // DW_ISA_ARM_thumb.
         break;
       case kArm64:
       case kMips:
       case kMips64:
         code_factor_bits_ = 2;  // 32-bit instructions
         break;
       case kNone:
       case kX86:
       case kX86_64:
         break;
     }
     DebugLineOpCodeWriter<> opcodes(false /* 32bit */, code_factor_bits_);
     opcodes.SetAddress(cunit_low_pc);
     if (dwarf_isa != -1) {
       opcodes.SetISA(dwarf_isa);
     }
     for (const OatWriter::DebugInfo* mi : compilation_unit) {
       struct DebugInfoCallbacks {
         static bool NewPosition(void* ctx, uint32_t address, uint32_t line) {
           auto* context = reinterpret_cast<DebugInfoCallbacks*>(ctx);
           context->dex2line_.push_back({address, static_cast<int32_t>(line)});
           return false;
         }
         DefaultSrcMap dex2line_;
       } debug_info_callbacks;

       const DexFile* dex = mi->dex_file_;
       if (mi->code_item_ != nullptr) {
         dex->DecodeDebugInfo(mi->code_item_,
                              (mi->access_flags_ & kAccStatic) != 0,
                              mi->dex_method_index_,
                              DebugInfoCallbacks::NewPosition,
                              nullptr,
                              &debug_info_callbacks);
       }

       // Get and deduplicate directory and filename.
       int file_index = 0;  // 0 - primary source file of the compilation.
       auto& dex_class_def = dex->GetClassDef(mi->class_def_index_);
       const char* source_file = dex->GetSourceFile(dex_class_def);
       if (source_file != nullptr) {
         std::string file_name(source_file);
         size_t file_name_slash = file_name.find_last_of('/');
         std::string class_name(dex->GetClassDescriptor(dex_class_def));
         size_t class_name_slash = class_name.find_last_of('/');
         std::string full_path(file_name);

         // Guess directory from package name.
         int directory_index = 0;  // 0 - current directory of the compilation.
         if (file_name_slash == std::string::npos &&  // Just filename.
             class_name.front() == 'L' &&  // Type descriptor for a class.
             class_name_slash != std::string::npos) {  // Has package name.
           std::string package_name = class_name.substr(1, class_name_slash - 1);
           auto it = directories_map.find(package_name);
           if (it == directories_map.end()) {
             directory_index = 1 + directories.size();
             directories_map.emplace(package_name, directory_index);
             directories.push_back(package_name);
           } else {
             directory_index = it->second;
           }
           full_path = package_name + "/" + file_name;
         }

         // Add file entry.
         auto it2 = files_map.find(full_path);
         if (it2 == files_map.end()) {
           file_index = 1 + files.size();
           files_map.emplace(full_path, file_index);
           files.push_back(FileEntry {
             file_name,
             directory_index,
             0,  // Modification time - NA.
             0,  // File size - NA.
           });
         } else {
           file_index = it2->second;
         }
       }
       opcodes.SetFile(file_index);

       // Generate mapping opcodes from PC to Java lines.
       const DefaultSrcMap& dex2line_map = debug_info_callbacks.dex2line_;
       if (file_index != 0 && !dex2line_map.empty()) {
         bool first = true;
         for (SrcMapElem pc2dex : mi->compiled_method_->GetSrcMappingTable()) {
           uint32_t pc = pc2dex.from_;
           int dex_pc = pc2dex.to_;
           auto dex2line = dex2line_map.Find(static_cast<uint32_t>(dex_pc));
           if (dex2line.first) {
             int line = dex2line.second;
             if (first) {
               first = false;
               if (pc > 0) {
                 // Assume that any preceding code is prologue.
                 int first_line = dex2line_map.front().to_;
                 // Prologue is not a sensible place for a breakpoint.
                 opcodes.NegateStmt();
                 opcodes.AddRow(mi->low_pc_, first_line);
                 opcodes.NegateStmt();
                 opcodes.SetPrologueEnd();
               }
               opcodes.AddRow(mi->low_pc_ + pc, line);
             } else if (line != opcodes.CurrentLine()) {
               opcodes.AddRow(mi->low_pc_ + pc, line);
             }
           }
         }
       } else {
         // line 0 - instruction cannot be attributed to any source line.
         opcodes.AddRow(mi->low_pc_, 0);
       }
     }
     opcodes.AdvancePC(cunit_high_pc);
     opcodes.EndSequence();
     WriteDebugLineTable(directories, files, opcodes, debug_line, debug_line_patches);
   }
 }

 }  // namespace dwarf
 }  // namespace art
	/*
	* Copyright (C) 2015 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 "elf_writer_debug.h"

	#include <unordered_set>

	#include "compiled_method.h"
	#include "driver/compiler_driver.h"
	#include "dex_file-inl.h"
	#include "dwarf/headers.h"
	#include "dwarf/register.h"
	#include "oat_writer.h"

	namespace art {
	namespace dwarf {

	static void WriteEhFrameCIE(InstructionSet isa,
	ExceptionHeaderValueApplication addr_type,
	std::vector<uint8_t>* eh_frame) {
	// Scratch registers should be marked as undefined. This tells the
	// debugger that its value in the previous frame is not recoverable.
	bool is64bit = Is64BitInstructionSet(isa);
	switch (isa) {
	case kArm:
	case kThumb2: {
	DebugFrameOpCodeWriter<> opcodes;
	opcodes.DefCFA(Reg::ArmCore(13), 0); // R13(SP).
	// core registers.
	for (int reg = 0; reg < 13; reg++) {
	if (reg < 4 \|\| reg == 12) {
	opcodes.Undefined(Reg::ArmCore(reg));
	} else {
	opcodes.SameValue(Reg::ArmCore(reg));
	}
	}
	// fp registers.
	for (int reg = 0; reg < 32; reg++) {
	if (reg < 16) {
	opcodes.Undefined(Reg::ArmFp(reg));
	} else {
	opcodes.SameValue(Reg::ArmFp(reg));
	}
	}
	auto return_reg = Reg::ArmCore(14); // R14(LR).
	WriteEhFrameCIE(is64bit, addr_type, return_reg, opcodes, eh_frame);
	return;
	}
	case kArm64: {
	DebugFrameOpCodeWriter<> opcodes;
	opcodes.DefCFA(Reg::Arm64Core(31), 0); // R31(SP).
	// core registers.
	for (int reg = 0; reg < 30; reg++) {
	if (reg < 8 \|\| reg == 16 \|\| reg == 17) {
	opcodes.Undefined(Reg::Arm64Core(reg));
	} else {
	opcodes.SameValue(Reg::Arm64Core(reg));
	}
	}
	// fp registers.
	for (int reg = 0; reg < 32; reg++) {
	if (reg < 8 \|\| reg >= 16) {
	opcodes.Undefined(Reg::Arm64Fp(reg));
	} else {
	opcodes.SameValue(Reg::Arm64Fp(reg));
	}
	}
	auto return_reg = Reg::Arm64Core(30); // R30(LR).
	WriteEhFrameCIE(is64bit, addr_type, return_reg, opcodes, eh_frame);
	return;
	}
	case kMips:
	case kMips64: {
	DebugFrameOpCodeWriter<> opcodes;
	opcodes.DefCFA(Reg::MipsCore(29), 0); // R29(SP).
	// core registers.
	for (int reg = 1; reg < 26; reg++) {
	if (reg < 16 \|\| reg == 24 \|\| reg == 25) { // AT, V, A, T*.
	opcodes.Undefined(Reg::MipsCore(reg));
	} else {
	opcodes.SameValue(Reg::MipsCore(reg));
	}
	}
	auto return_reg = Reg::MipsCore(31); // R31(RA).
	WriteEhFrameCIE(is64bit, addr_type, return_reg, opcodes, eh_frame);
	return;
	}
	case kX86: {
	// FIXME: Add fp registers once libunwind adds support for them. Bug: 20491296
	constexpr bool generate_opcodes_for_x86_fp = false;
	DebugFrameOpCodeWriter<> opcodes;
	opcodes.DefCFA(Reg::X86Core(4), 4); // R4(ESP).
	opcodes.Offset(Reg::X86Core(8), -4); // R8(EIP).
	// core registers.
	for (int reg = 0; reg < 8; reg++) {
	if (reg <= 3) {
	opcodes.Undefined(Reg::X86Core(reg));
	} else if (reg == 4) {
	// Stack pointer.
	} else {
	opcodes.SameValue(Reg::X86Core(reg));
	}
	}
	// fp registers.
	if (generate_opcodes_for_x86_fp) {
	for (int reg = 0; reg < 8; reg++) {
	opcodes.Undefined(Reg::X86Fp(reg));
	}
	}
	auto return_reg = Reg::X86Core(8); // R8(EIP).
	WriteEhFrameCIE(is64bit, addr_type, return_reg, opcodes, eh_frame);
	return;
	}
	case kX86_64: {
	DebugFrameOpCodeWriter<> opcodes;
	opcodes.DefCFA(Reg::X86_64Core(4), 8); // R4(RSP).
	opcodes.Offset(Reg::X86_64Core(16), -8); // R16(RIP).
	// core registers.
	for (int reg = 0; reg < 16; reg++) {
	if (reg == 4) {
	// Stack pointer.
	} else if (reg < 12 && reg != 3 && reg != 5) { // except EBX and EBP.
	opcodes.Undefined(Reg::X86_64Core(reg));
	} else {
	opcodes.SameValue(Reg::X86_64Core(reg));
	}
	}
	// fp registers.
	for (int reg = 0; reg < 16; reg++) {
	if (reg < 12) {
	opcodes.Undefined(Reg::X86_64Fp(reg));
	} else {
	opcodes.SameValue(Reg::X86_64Fp(reg));
	}
	}
	auto return_reg = Reg::X86_64Core(16); // R16(RIP).
	WriteEhFrameCIE(is64bit, addr_type, return_reg, opcodes, eh_frame);
	return;
	}
	case kNone:
	break;
	}
	LOG(FATAL) << "Can not write CIE frame for ISA " << isa;
	UNREACHABLE();
	}

	void WriteEhFrame(const CompilerDriver* compiler,
	const OatWriter* oat_writer,
	ExceptionHeaderValueApplication address_type,
	std::vector<uint8_t>* eh_frame,
	std::vector<uintptr_t>* eh_frame_patches,
	std::vector<uint8_t>* eh_frame_hdr) {
	const auto& method_infos = oat_writer->GetMethodDebugInfo();
	const InstructionSet isa = compiler->GetInstructionSet();

	// Write .eh_frame section.
	size_t cie_offset = eh_frame->size();
	WriteEhFrameCIE(isa, address_type, eh_frame);
	for (const OatWriter::DebugInfo& mi : method_infos) {
	const SwapVector<uint8_t>* opcodes = mi.compiled_method_->GetCFIInfo();
	if (opcodes != nullptr) {
	WriteEhFrameFDE(Is64BitInstructionSet(isa), cie_offset,
	mi.low_pc_, mi.high_pc_ - mi.low_pc_,
	opcodes, eh_frame, eh_frame_patches);
	}
	}

	// Write .eh_frame_hdr section.
	Writer<> header(eh_frame_hdr);
	header.PushUint8(1); // Version.
	header.PushUint8(DW_EH_PE_pcrel \| DW_EH_PE_sdata4); // Encoding of .eh_frame pointer.
	header.PushUint8(DW_EH_PE_omit); // Encoding of binary search table size.
	header.PushUint8(DW_EH_PE_omit); // Encoding of binary search table addresses.
	// .eh_frame pointer - .eh_frame_hdr section is after .eh_frame section, and need to encode
	// relative to this location as libunwind doesn't honor datarel for eh_frame_hdr correctly.
	header.PushInt32(-static_cast<int32_t>(eh_frame->size() + 4U));
	// Omit binary search table size (number of entries).
	// Omit binary search table.
	}

	/*
	* @brief Generate the DWARF sections.
	* @param oat_writer The Oat file Writer.
	* @param eh_frame Call Frame Information.
	* @param debug_info Compilation unit information.
	* @param debug_info_patches Address locations to be patched.
	* @param debug_abbrev Abbreviations used to generate dbg_info.
	* @param debug_str Debug strings.
	* @param debug_line Line number table.
	* @param debug_line_patches Address locations to be patched.
	*/
	void WriteDebugSections(const CompilerDriver* compiler,
	const OatWriter* oat_writer,
	std::vector<uint8_t>* debug_info,
	std::vector<uintptr_t>* debug_info_patches,
	std::vector<uint8_t>* debug_abbrev,
	std::vector<uint8_t>* debug_str,
	std::vector<uint8_t>* debug_line,
	std::vector<uintptr_t>* debug_line_patches) {
	const std::vector<OatWriter::DebugInfo>& method_infos = oat_writer->GetMethodDebugInfo();
	const InstructionSet isa = compiler->GetInstructionSet();

	// Find all addresses (low_pc) which contain deduped methods.
	// The first instance of method is not marked deduped_, but the rest is.
	std::unordered_set<uint32_t> deduped_addresses;
	for (auto it = method_infos.begin(); it != method_infos.end(); ++it) {
	if (it->deduped_) {
	deduped_addresses.insert(it->low_pc_);
	}
	}

	// Group the methods into compilation units based on source file.
	std::vector<std::vector<const OatWriter::DebugInfo*>> compilation_units;
	const char* last_source_file = nullptr;
	for (const auto& mi : method_infos) {
	// Attribute given instruction range only to single method.
	// Otherwise the debugger might get really confused.
	if (!mi.deduped_) {
	auto& dex_class_def = mi.dex_file_->GetClassDef(mi.class_def_index_);
	const char* source_file = mi.dex_file_->GetSourceFile(dex_class_def);
	if (compilation_units.empty() \|\| source_file != last_source_file) {
	compilation_units.push_back(std::vector<const OatWriter::DebugInfo*>());
	}
	compilation_units.back().push_back(&mi);
	last_source_file = source_file;
	}
	}

	// Write .debug_info section.
	for (const auto& compilation_unit : compilation_units) {
	uint32_t cunit_low_pc = 0xFFFFFFFFU;
	uint32_t cunit_high_pc = 0;
	for (auto method_info : compilation_unit) {
	cunit_low_pc = std::min(cunit_low_pc, method_info->low_pc_);
	cunit_high_pc = std::max(cunit_high_pc, method_info->high_pc_);
	}

	size_t debug_abbrev_offset = debug_abbrev->size();
	DebugInfoEntryWriter<> info(false /* 32 bit */, debug_abbrev);
	info.StartTag(DW_TAG_compile_unit, DW_CHILDREN_yes);
	info.WriteStrp(DW_AT_producer, "Android dex2oat", debug_str);
	info.WriteData1(DW_AT_language, DW_LANG_Java);
	info.WriteAddr(DW_AT_low_pc, cunit_low_pc);
	info.WriteAddr(DW_AT_high_pc, cunit_high_pc);
	info.WriteData4(DW_AT_stmt_list, debug_line->size());
	for (auto method_info : compilation_unit) {
	std::string method_name = PrettyMethod(method_info->dex_method_index_,
	*method_info->dex_file_, true);
	if (deduped_addresses.find(method_info->low_pc_) != deduped_addresses.end()) {
	method_name += " [DEDUPED]";
	}
	info.StartTag(DW_TAG_subprogram, DW_CHILDREN_no);
	info.WriteStrp(DW_AT_name, method_name.data(), debug_str);
	info.WriteAddr(DW_AT_low_pc, method_info->low_pc_);
	info.WriteAddr(DW_AT_high_pc, method_info->high_pc_);
	info.EndTag(); // DW_TAG_subprogram
	}
	info.EndTag(); // DW_TAG_compile_unit
	WriteDebugInfoCU(debug_abbrev_offset, info, debug_info, debug_info_patches);

	// Write .debug_line section.
	std::vector<FileEntry> files;
	std::unordered_map<std::string, size_t> files_map;
	std::vector<std::string> directories;
	std::unordered_map<std::string, size_t> directories_map;
	int code_factor_bits_ = 0;
	int dwarf_isa = -1;
	switch (isa) {
	case kArm: // arm actually means thumb2.
	case kThumb2:
	code_factor_bits_ = 1; // 16-bit instuctions
	dwarf_isa = 1; // DW_ISA_ARM_thumb.
	break;
	case kArm64:
	case kMips:
	case kMips64:
	code_factor_bits_ = 2; // 32-bit instructions
	break;
	case kNone:
	case kX86:
	case kX86_64:
	break;
	}
	DebugLineOpCodeWriter<> opcodes(false /* 32bit */, code_factor_bits_);
	opcodes.SetAddress(cunit_low_pc);
	if (dwarf_isa != -1) {
	opcodes.SetISA(dwarf_isa);
	}
	for (const OatWriter::DebugInfo* mi : compilation_unit) {
	struct DebugInfoCallbacks {
	static bool NewPosition(void* ctx, uint32_t address, uint32_t line) {
	auto* context = reinterpret_cast<DebugInfoCallbacks*>(ctx);
	context->dex2line_.push_back({address, static_cast<int32_t>(line)});
	return false;
	}
	DefaultSrcMap dex2line_;
	} debug_info_callbacks;

	const DexFile* dex = mi->dex_file_;
	if (mi->code_item_ != nullptr) {
	dex->DecodeDebugInfo(mi->code_item_,
	(mi->access_flags_ & kAccStatic) != 0,
	mi->dex_method_index_,
	DebugInfoCallbacks::NewPosition,
	nullptr,
	&debug_info_callbacks);
	}

	// Get and deduplicate directory and filename.
	int file_index = 0; // 0 - primary source file of the compilation.
	auto& dex_class_def = dex->GetClassDef(mi->class_def_index_);
	const char* source_file = dex->GetSourceFile(dex_class_def);
	if (source_file != nullptr) {
	std::string file_name(source_file);
	size_t file_name_slash = file_name.find_last_of('/');
	std::string class_name(dex->GetClassDescriptor(dex_class_def));
	size_t class_name_slash = class_name.find_last_of('/');
	std::string full_path(file_name);

	// Guess directory from package name.
	int directory_index = 0; // 0 - current directory of the compilation.
	if (file_name_slash == std::string::npos && // Just filename.
	class_name.front() == 'L' && // Type descriptor for a class.
	class_name_slash != std::string::npos) { // Has package name.
	std::string package_name = class_name.substr(1, class_name_slash - 1);
	auto it = directories_map.find(package_name);
	if (it == directories_map.end()) {
	directory_index = 1 + directories.size();
	directories_map.emplace(package_name, directory_index);
	directories.push_back(package_name);
	} else {
	directory_index = it->second;
	}
	full_path = package_name + "/" + file_name;
	}

	// Add file entry.
	auto it2 = files_map.find(full_path);
	if (it2 == files_map.end()) {
	file_index = 1 + files.size();
	files_map.emplace(full_path, file_index);
	files.push_back(FileEntry {
	file_name,
	directory_index,
	0, // Modification time - NA.
	0, // File size - NA.
	});
	} else {
	file_index = it2->second;
	}
	}
	opcodes.SetFile(file_index);

	// Generate mapping opcodes from PC to Java lines.
	const DefaultSrcMap& dex2line_map = debug_info_callbacks.dex2line_;
	if (file_index != 0 && !dex2line_map.empty()) {
	bool first = true;
	for (SrcMapElem pc2dex : mi->compiled_method_->GetSrcMappingTable()) {
	uint32_t pc = pc2dex.from_;
	int dex_pc = pc2dex.to_;
	auto dex2line = dex2line_map.Find(static_cast<uint32_t>(dex_pc));
	if (dex2line.first) {
	int line = dex2line.second;
	if (first) {
	first = false;
	if (pc > 0) {
	// Assume that any preceding code is prologue.
	int first_line = dex2line_map.front().to_;
	// Prologue is not a sensible place for a breakpoint.
	opcodes.NegateStmt();
	opcodes.AddRow(mi->low_pc_, first_line);
	opcodes.NegateStmt();
	opcodes.SetPrologueEnd();
	}
	opcodes.AddRow(mi->low_pc_ + pc, line);
	} else if (line != opcodes.CurrentLine()) {
	opcodes.AddRow(mi->low_pc_ + pc, line);
	}
	}
	}
	} else {
	// line 0 - instruction cannot be attributed to any source line.
	opcodes.AddRow(mi->low_pc_, 0);
	}
	}
	opcodes.AdvancePC(cunit_high_pc);
	opcodes.EndSequence();
	WriteDebugLineTable(directories, files, opcodes, debug_line, debug_line_patches);
	}
	}

	} // namespace dwarf
	} // namespace art