ChangeLog

2013-09-18 Chinyen Chou <petechou@gmail.com>
	* Executive Summary:
	1. Support more linker script commands for linking FreeBSD and Linux kernel.
	2. Add a smaller new linker tool: ld.lite.
	3. Initiate MIPS64 ABI support.
	4. Migrate to LLVM r187732.

	* Command Line Options and Building System:
	1. Support -T option.
	2. Support -z combreloc/nocombreloc.
	3. Initiate CMake support.

	* SectionMap:
	1. Support construct SectionMap from SECTIONS command in a linker script file.

	* Target Backends:
	1. GNULDBackend: use SectionMap to do layout.
	2. GNULDBackend: add readRelocation() and emitRelocation functions.
	3. MIPS: add 32/64 GNULDBackend, GOT, and Relocator classes.
	4. MIPS: support more relocations. (R_MIPS_GPREL16, R_MIPS_64, R_MIPS_GOT_DISP,
	   R_MIPS_GOT_PAGE, R_MIPS_GOT_OFST, and R_MIPS_SUB)
	5. Target: refine target registry, lookup, and creation.

	* Linker Script:
	1. Support SECTIONS, SEARCH_DIR, ASSERT commands.
	2. Support orphan sections placement.
	3. Support location counter processing.
	4. Support operators and many builtin functions in an expression.
	5. Change to use Bison GLR skeleton.

	* Architectural Changes:
	1. Deprecate FragmentLinker: move the functions into ObjectLinker instead.

2013-06-03 Chinyen Chou <petechou@gmail.com>
	* Executive Summary:
	1. Add linker script framework and some script commands support.
	2. Add MIPS executable linking support.

	* Command Line Options and Building System:
	1. Require flex 2.5.35 and bison 2.4.3, or later.

	* New Features:
	1. Support processing simple linker script files like libc.so in linux.

	* Target Backends:
	1. MIPS: Add PLT and GOTPLT support.
	2. MIPS: Add LA25 stub for a non-PIC interface to a PIC function.
	3. MIPS: Support more relocations. (R_MIPS_26, R_MIPS_JALR,
	   R_MIPS_LA25_LUI, R_MIPS_LA25_J, R_MIPS_LA25_ADD, and R_MIPS_PC32)

	* Linker Script:
	1. Support ENTRY command.
	2. Support file commands like GROUP, AS_NEEDED and SEARCH_DIR.
	3. Support basic assignments.

	* Architectural Changes:
	1. Parse an unformatted input as a linker script file in
	   ObjectLinker::normalize().
	2. Deprecate DefSymParser: separate parsing and evaluation to different
	   classes, then we can handle --defsym option and ldscript assignments
	   in the same way.

2013-04-29 Luba Tang <lubatang@gmail.com>
	* Executive Summary:
	1. Add three new backends - x86_64, x32 and Hexagon.
	2. Support MinGW platform
	3. Support Mips multiple global offset tables.
	4. Support variant-length relocation entry. (Mips/x32/x86_64)
	5. Export libmcld library
	6. Migrate to LLVM r176038

	* Command Line Options and Building System:
	1. Support -m <emulation> option.
	2. Support --defsym option.
	3. ./configure script supports --target options. (Conform to binutils)

	* New Features:
	1. Support weak alias symbols in shared libraries.
	2. Support 64-bit architecture.
	3. Support GNU linkonce sections.
	4. Support GNU excluded sections.
	5. Able to link ELF objects with GNU LTO sections.
	6. Support empty eh_frame section.

	* Target Backends:
	1. ARM backend supports more relocations. (R_ARM_PC24, R_ARM_THM_*)
	2. ARM backend defines __exidx_start/_end symbols for .ARM.exidx section.
	3. Mature x86_64 backend. Support variant-length relocation entries.
	4. Mature x32 backend.
	5. x86 backend supports more relocations.
	6. Mips backend supports multiple GOT.
	7. Mips backend supports variant-length relocation entries.
	8. Hexagon backend supports partial linking.
	9. Hexagon backend can emit dynamic linked libraries.

	* Architectural Change:
	1. Move LinkerScript from LinkerConfig to Module.
	2. Add Relocator::initializeScan() and finalizeScan(). Backends can know the
	   the timing of input file change during relocation scanning.
	3. Add 64-bit reader and writer.
	4. class Path is stick on UTF-8 locale.
	5. rename Linker::config() -> Linker::emulate().
	6. extract Linker::normalize() form Linker::resolve().

2013-01-31 Diana Chen <mysekki@gmail.com>
	* Executive Summary:
	1. IRBuilder supports define Symbols
	2. Remove memory leakage
	3. Enhance GNU ld compatibility for FreeBSD and NetBSD
	4. Support part of X86 TLS optimization
	5. Migrate to LLVM r171906

	* Command Line Options and Building System:
	1. Support -x, -X and -s options
	2. Support -rpath option
	3. Set default search path
	4. Support -enable-new-dtags option
	5. Support --hash-style option and GNU style hash table
	6. Support --nmagic and --omagic options
	7. Support -nostdlib option

	* New Features:
	1. Add IRBuilder::AddSymbol. Replace functions in FragmentLinker to
	   IRBuilder
	2. Introduce to CodePosition concept

	* Target Backends:
	1. Move backend flag and page size to GNUInfo
	2. Mips backend: Handle XGOT types of relocation
	3. Support part of X86 TLS optimizations
	4. Add the prototype of Hexagon backend support

	* Readers and writers:
	1. Merge writers for Binary/Executable/Object/Dynamic Object to
	   ELFObjectWriter
	2. Remove ARMELFArchiveReader

	* Linking process:
	1. Separate the linking program process into two steps - resolve and layout
	2. Initial relaxation stuff after normalization
	3. Do allocateCommonSymbols immediately after mergeSection

2012-12-18 Luba Tang <lubatang@gmail.com>
	* Executive Summary:
	1. IRBuilder supports adding symbols and relocations.
	2. Reduce memory usage of relocation.
	3. Enhance GNU ld compatibility for FreeBSD and NetBSD.
	4. Migrate to LLVM r168413

	* Command Line Options and Building System:
	1. Support --oformat, --format options
	2. Support --fatal-warnings
	3. Add --enable-werror in `./configure' script

	* Readers, writers and IRBuilder:
	1. Add IRBuilder::AddSymbol() and IRBuilder::AddRelocation() APIs.
	2. ELFObjectReader, ELFDynObjReader and ELFReader use IRBuilder instead of
	   FragmentLinker.

	* Relocations:
	1. Provide Relocation factory method.
	2. Derive Relocation directly from ilist_node<> for saving memory usage.
	3. Isolate relocation applying functions. Collect them in Relocator.

	* LinkerConfig and GNULDBackend's Configuration:
	1. Move bitclass and endian configuration out of GNULDBackend. Collect them
	   in TargetOptions. This can break the dependency between GNULDBackend and
	   Relocation.
	2. Move triple from LinkerConfig to TargetOptions.
	3. Merge Layout into GNULDBackend.
	4. Refactor GOT and PLT.
	5. Move GNU related options into GNUInfo.

2012-11-20 Luba Tang <lubatang@gmail.com>
	* Executive Summary:
	1. Improve linking speed about x30 via new algorithm and architecture.
	2. Enhance GNU ld compatibility. MCLinker is able to link all libraries
	   and programs of Android. (Few libraries have to revise their linking options)
	3. Enhance GNU ld compatibility. MCLinker is able to link all libraries
	   and programs of BSD base system 4.3. (Some options that needed by 4.4
	   are unsupported yet).
	4. Support ARM EH ABI.
	5. Provide IRBuilder. Users can customize the content of input file and
	   make their customized linker by IRBuilder.
	6. Add basic elements for support partial linking in the future.

	* Command Line Options:
	1. Support --strip-debug/-S
	2. Add --relocatable/-r option. MCLinker does not fully support -r yet.
	3. Add some fake options to compatible with GNU ld.

	* Target/TargetMachine, LD/ELFObjectFileFormat, LD/ELFObjectWriter,
	Target/GNULDBackend, CodeGen/MCLDTargetMachine:
	1. Add CGFT_PARTIAL code generation type.
	2. Add ELFObjectFileFormat to initialize the output format of -r.
	3. Add ELFObjectWriter to write the output of partial linking.
	4. Add GNULDBackend::createObjectWriter().
	5. rename CodeGen/LLVMTargetMachine as CodeGen/MCLDTargetMachine.
	6. Support R_386_TLS_GOTIE relocation
	7. Define __exidx_start and __exidx_end ARM standard symbols
	8. Define __DYNAMIC symbol
	9. For GNU ld compatibility, check if a symbol is a C identifier in GNULDBackend.

	* New Architecture:
	1.  Add FragmentRef::Create/Destroy. Use factory method instead of simple factory.
	2.  Add LDSymbol::Create/Destroy and ResolveInfo::Create/Destroy
	3.  Add LDSection::Create/Restroy
	4.  Reduce the functionalities of Layout. Let layout to focus on section order.
	5.  Calculate Fragments' offset when appending them into section data.
	6.  Remove SectionMerger.
	7.  Move SectionMap to LinkerConfig
	8.  Rewrite EhFrame. Separate origin EhFrame into EhFrameReader and EhFrame data.
	9.  Let ObjectReader controls EhFrame::treatAsRegularSection() flag.
	10. Add Null objects for ResolveInfo, FragmentRef, and LDSymbol.
	11. Add RelocData to store relocation entries.
	12. LDSection can point to either a SectionData, a RelocData or a EhFrame.
	13. Add ObjectLinker and ObjectBuilder. ObjectBuilder is used to build target and
	    format independent data structure. ObjectLinker is used to link object with
	    target and format dependent behaviors.
	14. Remove section-related methods in FragmentLinker. Move them into builders.
	15. Separate the `read relocation' stage into `read' and `scan' stages.
	16. Add Environment.h. Provide Initialize() and Finalize() to simplify the
	    initiliazation of MCLinker.
	17. Add Linker.h. A modular linker. The core of MCLinker.

2012-10-04 Chinyen Chou <petechou@gmail.com>
	* Executive Summary:
	1. Add TLS support and X86 implementation.
	2. Enhance GNU ld compatibility.
	3. Add instruction relaxation pass and ARM implementation.

	* MC/SymbolCategory, Target/GNULDBackend, Target/ARMLDBackend,
	Target/X86LDBackend, Target/MipsLDBackend, Target/TargetLDBackend,
	Target/ELFDynamic:
	1. Handle tdata and tbss sections and symbols.
	2. Setup dynamic flags such as DF_TEXTREL and DF_STATIC_TLS.

	* Target/X86/X86LDBackend, Target/X86/X86RelocationFactory:
	1. Add X86 relocation support for R_386_TLS_GD, R_386_TLS_LE, and
	R_386_TLS_IE.

	* LD/GroupReader, Object/ObjectLinker, LD/GNUArchiveReader:
	1. Support archives group. (i.e., --start-group ARCHIVES --end-group)

	* Target/GNULDBackend, Target/GNULDBackend, Fragment/Fragment,
	Fragment/Stub, Fragment/FragmentRef, LD/StubFactory, LD/BranchIsland,
	LD/BranchIslandFactory,	LD/ELFWriter, Object/ObjectLinker:
	1. Add relaxation interface.

	* Target/ARMLDBackend, Target/ARMToARMStub, Target/ARMToTHMStub,
	Target/THMToTHMStub, Target/THMToTHMStub, Target/ARMRelocationFactory:
	1. Add ARM relaxation implementation and ARM stubs.

	* Fragment/Fragment, Fragment/NullFragment, LD/Layout, LD/ELFWriter,
	Target/ARMLDBackend:
	1. Add NullFragment for some special symbols (e.g., dvmCompilerTemplateEnd)
	that refer to an "end" fragment.

	* mcld/GeneralOptions, mcld/ScriptOptions, tools/llvm-mcld, Target/GNULDBackend:
	1. Support -Ttext, -Tdata, and -Tbss options.
	2. Support --section-start SECTION=ADDRESS option.

2012-09-10 Luba Tang <luba.tang@mediatek.com>
	* Executive Summary:
	1. Migrate on LLVM r162314
	2. Large scale architecture refactoring.
	3. No new features; No functional changes.
	4. Remove two architecture weaknesses in alone::Linker.

	* Separate MCLinker into three layers:
	1. MCLinker - handle with input files. The adapter to LLVM.
	2. ObjectLinker - handle with object file format.
	3. FragmentLinker - handle with piece of code or data.

	* Provide mcld::Module as the intermediate representation:
	1. Remove mcld::Output. Move all fields of mcld::Output into mcld::Module.
	2. Move NamePool from FragmentLinker to Module.
	3. Move Relocation Table from FragmentLinker to Module.
	4. Move SymbolCategory from FragmentLinker to Module.
	5. Move InputTree from MCLinker to Module.

	* Separate MCLDInfo into LinkerConfig and InputBuilder:
	1. All fields in MCLDInfo that can be constant are moved into LinkerConfig.
	2. MemoryAreaFactory, ContextFactory and InputFactory are moved into LinkerConfig.

	* Action-based linkers:
	1. MCLinker uses FileActions and CommandActions to build up the input tree.
	2. Remove SectLinkerOption, PositionDependentOption and DerivedPositionDependentOption.
	3. Remove ugly type castings.

	* Add new file stream and file utilies:
	1. raw_mem_ostream - an MemoryArea adapter to llvm::raw_ostream.
	2. ToolOutputFile - an raw_mem_ostream adapter to llvm::tool_output_file.

	* Hide less-frequently-used classes:
	1. Hide RegionFactory. MemoryArea becomes a wrapper of RegionFactory.
	2. Hide ContextFactory and MemoryAreaFactory. Move them into InputBuilder.

2012-08-01 Chinyen Chou <petechou@gmail.com>
	* Executive Summary:
	1. Get rid of LLVM MC layer and reduce the dependency to LLVM.
	2. Support GNU variant archive file format.

	* llvm-mcld/llvm-mcld, CodeGen/LLVMTargetMachine:
	Sync up LLVM api changes with LLVM upstream @160668.

	* Support/Path:
	Add parent_path() api.

	* LD/EFLReader, LD/ELFObjectReader, LD/ELFDynObjReader, LD/EhFrame,
	MC/MCLDInput, MC/MCLinker, Targer/ARMLDBackend:
	Read Inputs from the specific file offset.

	* LD/ArchiveReader, LD/BSDArchiveReader, LD/GNUArchiveReader,
	LD/Archive, MC/MCLDDriver:
	Support GNU variant archive file format.

	* CodeGen/SectLinker, LD/AlignFragment, LD/CIE, LD/ELFReader,
	LD/ELFWriter, LD/EhFrame, LD/FDE, LD/FillFragment, LD/Fragment,
	LD/FragmentRef, LD/LDSection, LD/LDSectionFactory, LD/LDSymbol,
	LD/Layout, LD/NamePool, LD/RegionFragment, LD/Relocation,
	LD/RelocationFactory, LD/SectionData, LD/SectionMerger,
	LD/TargetFragment, MC/MCLinker, Target/GOT, Target/PLT,
	Target/OutputRelocSection:
	Get rid of LLVM MC layer.

	* alone/Support/LinkerConfig, alone/Core/Linker, tools/mcld/main:
	Add --shared, --Bsymbolic, --portable support in alone linker.

	* test/Archive, test/Android:
	1. Add regression test for ArchiveReader.
	2. Add regression test of Android examples for alone linker.
	3. Add regression test for no option.

	* unittests/Linker:
	1. Add unittest to test different linking stages.

2012-07-04 Luba Tang <lubatang@gmail.com>
	* Executive Summary:
	1. Support itanium exception handling
	2. New MemoryArea sub-system. Speed up linking.
	3. Add experimental facade (standard alone linker) to eliminate
	the dependency to LLVM

	* MC/MCLinker, LD/Layout, LD/EhFrame, LD/LDFileFormat:
	1. Support command line option --eh-frame-hdr
	2. Arrange the order of eh_frame and eh_frame_hdr section. Add
	SHO_EXCEPTION in Layout.
	3. Add LDFileFormat::Exception section kind.
	4. Add PT_GNU_EH_FRAME segment.
	5. Separate .gotplt from .got in x86.

	* Target/ARMLDBackend, Target/X86LDBackend, Target/MipsLDBackend,
	Target/TargetLDBackend, Target/GNULDBackend, LD/ELFFileFormat:
	1. Factor getOutputFormat() from concrete backend to abstract one.
	2. Support copy relocation.
	3. Support GNU indirect function. (STT_GNU_IFUNC)
	4. Support .stack section.

	* test/Exception, test/lib/X86/Linux, test/Symbols:
	1. Add regression tests for exception handling.
	2. Add regression tests for .init_array section.

	* Support/MemoryArea, Support/FileHandle, Support/Space, ADT/Flags,
	Support/SystemUtils, Support/FileSystem:
	1. Enhance performance. Eliminate the need of msync.
	2. Separate utility functions from FileSystem.h. Move them to
	SystemUtils.h

	* alone/Linker, alone/Core/LinkerConfig, alone/Core/TargetLinkerConfig,
	alone/Initialize:
	1. Add stand alone linker facade. Eliminate the dependency to LLVM.

2012-05-23 Diana Chen <mysekki@gmail.com>
	* Executive Summary:
	1. Support static link of Itanium exception handling (examined on X86
	Android).
	2. Enhance GNU ld compatibility.
	3. Support special option --portable.
	4. Successfully examine executable files emission for X86 machine.

	* LD/ELFDynObjWriter, ELFExecWriter, MC/MCLinker:
	Support static link of Itanium exception handling.

	* MC/MCLDOptions, MC/MCLDInfo, MC/MCLinker.tcc, llvm-mcld.cpp:
	1. Support command line option --wrap
	2. Support command line option --portable
	3. Support command line options --allow-multiple-definition and
	--no-undefined

	* Target/X86LDBackend, Target/X86RelocationFactory, Target/X86PLT:
	Executable files generagtion for X86
	1. Enhance the relocation function for R_386_PC32.
	2. Add function to apply PLT for emitting executable files.

	* test/Symbols, test/Commands, test/Exceptions:
	1. Add regression tests for new supported command line options.
	2. Add regression tests for exception handling support.

	* LD/TextDiagnosticPrinter, Support/FileSystem, Support/MsgHandling,
	mcld/LD/MsgHandler, llvm-mcld.cpp, Support/raw_ostream:
	Implement the expressive Diagnostic System.
	1. Implement beginInput/endInput of TextDiagnosticPrinter
	2. Add new expressive diagnostic output: unreachable
	3. Use llvm approach instead of mcld::isatty()
	4. Add mcld::raw_fd_ostream for better color-control.

	* LD/Layout, Target/ARMRelocationFactory, Target/X86RelocationFactory,
	Target/MipsRelocationFactory, Target/ARMGOT, Target/X86GOT, Target/MipsGOT,
	Target/ARMPLT, Target/X86PLT, Target/X86GOTPLT, LD/ELFObjectReader
	LD/ELFReader, LD/GNUArchiveReader, MC/MCLDAttribute, MC/MCLDDriver:
	Use the expressive Diagnostic System to report the error message.

2012-05-11 Chinyen Chou <petechou@gmail.com>
	* Executive Summary:
	In this version: flames, we add the following new features in MCLinker:
	1. -z options support (except for -z combreloc)
	2. Thumb/Thumb2 mode support.
	3. DWARF debugging support.
	4. Introduce an expressive Diagnostic system to print out linking error message.
	5. Executable files generation (examined on ARM/MIPS Android).

	* patch/LLVM.Patch:
	Complement llvm/Support/ELF.h for ELF segments and .dynamic sections.

	* Target/ARMLDBackend, Target/ARM/Relocation:
	Add thumb/thumb2 mode support.

	* MC/MCLDOptions, MC/ZOption, Support/CommandLine, llvm-mcld.cpp:
	1. Add -z options, -Bgroup, --dynamic-linker= and -shared
	2. Add --verbose[=0,1,2], --error-limit[=N], --warning-limit[=N],
	   --color[=never, always, auto] and --no-undefined

	* Target/ELFDynamic:
	Set DT_FLAGS and DT_FLAGS_1 based on the given -z option.

	* LD/Layout, Target/GNULDBackend, Target/TargetLDBackend,
	  Target/ARMLDBackend, Target/X86LDBackend, Target/MipsLDBackend,
	  MC/MCLinker:
	Support -z relro for PT_GNU_RELRO segment.

	* docs/llvm-mcld.pod:
	Add perldoc for man page.

	* Target/GNULDBackend:
	Support -z execstack/noexecstack for PT_GNU_STACK segment.

	* Target/ARMLDBackend:
	Support -z copyreloc in ARMLDBackend.

	* LD/ELFExecWriter, LD/ExecWriter, LD/ELFExecFileFormat, LD/Layout,
	Target/GNULDBackend, Target/TargetLDBackend, MC/MCLDDriver, llvm-mcld.cpp:
	Support executable generation.
	1. "Hello World" is examined successfully on ARM/MIPS Android.
	2. Some SPECCPU examples are also examined on ARM Android.

	* Target/MipsLDBackend:
	Android Quake2 JNI example is examined successfully.

	* LD/ELFReader, MC/MCLinker, Target/TargetLDBackend, LD/ELFDynObjWriter,
	  LD/ELFExecWriter, LD/Layout, Target/ARMLDBackend, Target/X86LDBackend,
	  Target/MipsLDBackend:
	Support DWARF debug sections linking.
	1. GDB can debug the MCLinker output object. e.g., ndk-gdb in Android.

	* LD/DiagnosticInfos, LD/Diagnostic, LD/MsgHandler, LD/DiagnosticPrinter,
	  LD/TextDiagnosticPrinter, LD/DiagnosticEngine, Support/MsgHandling:
	Introduce an expressive Diagnostic system.

	* LD/Resolver, LD/StaticResolver, LD/NamePool:
	Changed to use new Diagnostic System.

2012-03-14 Luba Tang <lubatang@gmail.com>
	* Migrate on LLVM@r152063
	* Migrate on clang@r152062

	* LD/LDSection, LD/ELFFileFormat, LD/ELFDynObjFileFormat,
	  LD/ELFExecFileFormat:
	Support setting alignment constraint in section header.
	* LD/Layout:
	Update sections' alignment constraints during section merging.

	* Support/MemoryArea, Support/MemoryRegion:
	Enhance memory utilities.

	* Target/ARMLDBackend:
	1. work around ARM.exidx and ARM.extab.
	2. add relocation supports - R_ARM_TARGET1, R_ARM_TARGET2, R_ARM_ABS32,
	R_ARM_BASE_PREL, and R_ARM_GOT_PREL

	* Target/MipsLDBackend:
	1. Android bitmap, native Plasma and Quake1 is examined successfully.

	* Target/GNULDBackend, LD/ELFSegmentFactory:
	Move segment-related implemenation out of GNULDBackend.

	* Support/ScopedWriter:
	Obsolete, removed.

	* MC/SymbolCategory:
	add random accessing functions

2012-03-01 Luba Tang <lubatang@gmail.com>
	* add test/ARM/Relocation:
	* add test/ARM/GOTPLT:
	Simple regression testcases. Each case is used for testing a single
	relocation or GOTPLT entry.

	* add test/Android/Plasma/ARM, X86, MIPS:
	* add test/Android/Quake/ARM, X86:
	* add test/Android/Quake2/ARM, X86:
	Basic regression testcases for Android platform. The system libraries
	for each platform are under test/libs/ARM, X86, MIPS.

	* Target/TargetLDBackend:
	separate readSections() into readRegularSection() and
	readTargetSection().

	* Target/GNULDBackend:
	Move hash_bucket_count() and isDynamicSymbol() on successors.

	* Target/MipsLDBackend: Eable to link trivial cases and Android Plasma.
	* Target/X86LDBackend: Eable to link all Android JNI cases with CRT.

	* CodeGen/SectLinkerOption, llvm-mcld.cpp:
	get rid of -dB option. MCLinker does not need to ask users for -dB
	option.

	* MC/MCLinker, LD/ELFObjectReader, LD/ELFObjectWriter:
	Support symbol visibility.

	* LD/LDSection: Separate LinkInfo into Link and Info.

	* LD/Relocation:
	In order to enhance memory footprints:
	1. Remove Relocation::m_Parent.
	2. Let target data be a copy, not a pointer.

	* LD/ELFReader, LD/ObjectReader, LD/ELFObjectReader, LD/Layout:
	Support GROUPT section.

	* LD/LDFileFormat:
	Support all special sections listed in Linux Standard Base
	(ISO/IEC 23360).

	* Support/GCFactoryListTraits:
	Provides GCFactory's trait for llvm::iplist.

	* Support/LEB128: Add LEB128 utilities.

	* Support/HashTable:
	Identify ambiguous constructors by adding an anonyous parameter.

	* Suppot/MemoryRegion, Support/MemoryArea:
	1. remove pIsWrite parameter in MemoryArea::request(). MemoryArea knows
	the file is readable or writable when map() the file.
	2. MemoryArea allows to request a zero size MemoryRegion.

	* patch/LLVM.patch: complement llvm/Support/ELF.h.
	Add SHT_GNU_ATTRIBUTES, SHT_GNU_HASH, SHT_GNU_verdef, SHT_GNU_verneed,
	and SHT_GNU_versym.

	* LD/Layout:
	1. Work around LDFileFormat::Exception and LDFileFormat::Version.
	2. appendFragment(): Support merging sections with different alignment
	constraints.

2012-02-03 Luba Tang <lubatang@gmail.com>
	* allocate common symbols in BSS section
	* add ThreadLocal type in ResolveInfo::Type
	* Quake2 can be linked on ARM Android.

2012-02-02 Luba Tang <lubatang@gmail.com>
	* Quake can be linked on x86 Android.

2012-01-17 Luba Tang <lubatang@gmail.com>
	* Quake can be linked on ARM Android.
	* All APIs for backends is ready.

2012-01-12 Jush Lu <Jush.Lu@mediatek.com>
	* Trivial cases have worked on ARM.

2011-05-23 Luba Tang <lubatang@gmail.com>
	* create all basic files and directories.