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llvm-mirror/lib/MC/MCAssembler.cpp
Chris Lattner d786e8929e tweak #includes 
llvm-svn: 79744
2009-08-22 19:19:12 +00:00

707 lines
21 KiB
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//===- lib/MC/MCAssembler.cpp - Assembler Backend Implementation ----------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#include "llvm/MC/MCAssembler.h"
#include "llvm/MC/MCSectionMachO.h"
#include "llvm/Target/TargetMachOWriterInfo.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/SmallString.h"
#include "llvm/ADT/StringMap.h"
#include "llvm/ADT/Twine.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/raw_ostream.h"
using namespace llvm;
class MachObjectWriter;
static void WriteFileData(raw_ostream &OS, const MCSectionData &SD,
MachObjectWriter &MOW);
class MachObjectWriter {
// See <mach-o/loader.h>.
enum {
Header_Magic32 = 0xFEEDFACE,
Header_Magic64 = 0xFEEDFACF
};
static const unsigned Header32Size = 28;
static const unsigned Header64Size = 32;
static const unsigned SegmentLoadCommand32Size = 56;
static const unsigned Section32Size = 68;
static const unsigned SymtabLoadCommandSize = 24;
static const unsigned DysymtabLoadCommandSize = 80;
static const unsigned Nlist32Size = 12;
enum HeaderFileType {
HFT_Object = 0x1
};
enum LoadCommandType {
LCT_Segment = 0x1,
LCT_Symtab = 0x2,
LCT_Dysymtab = 0xb
};
// See <mach-o/nlist.h>.
enum SymbolTypeType {
STT_Undefined = 0x00,
STT_Absolute = 0x02,
STT_Section = 0x0e
};
enum SymbolTypeFlags {
// If any of these bits are set, then the entry is a stab entry number (see
// <mach-o/stab.h>. Otherwise the other masks apply.
STF_StabsEntryMask = 0xe0,
STF_TypeMask = 0x0e,
STF_External = 0x01,
STF_PrivateExtern = 0x10
};
/// MachSymbolData - Helper struct for containing some precomputed information
/// on symbols.
struct MachSymbolData {
MCSymbolData *SymbolData;
uint64_t StringIndex;
uint8_t SectionIndex;
// Support lexicographic sorting.
bool operator<(const MachSymbolData &RHS) const {
const std::string &Name = SymbolData->getSymbol().getName();
return Name < RHS.SymbolData->getSymbol().getName();
}
};
raw_ostream &OS;
bool IsLSB;
public:
MachObjectWriter(raw_ostream &_OS, bool _IsLSB = true)
: OS(_OS), IsLSB(_IsLSB) {
}
/// @name Helper Methods
/// @{
void Write8(uint8_t Value) {
OS << char(Value);
}
void Write16(uint16_t Value) {
if (IsLSB) {
Write8(uint8_t(Value >> 0));
Write8(uint8_t(Value >> 8));
} else {
Write8(uint8_t(Value >> 8));
Write8(uint8_t(Value >> 0));
}
}
void Write32(uint32_t Value) {
if (IsLSB) {
Write16(uint16_t(Value >> 0));
Write16(uint16_t(Value >> 16));
} else {
Write16(uint16_t(Value >> 16));
Write16(uint16_t(Value >> 0));
}
}
void Write64(uint64_t Value) {
if (IsLSB) {
Write32(uint32_t(Value >> 0));
Write32(uint32_t(Value >> 32));
} else {
Write32(uint32_t(Value >> 32));
Write32(uint32_t(Value >> 0));
}
}
void WriteZeros(unsigned N) {
const char Zeros[16] = { 0 };
for (unsigned i = 0, e = N / 16; i != e; ++i)
OS << StringRef(Zeros, 16);
OS << StringRef(Zeros, N % 16);
}
void WriteString(const StringRef &Str, unsigned ZeroFillSize = 0) {
OS << Str;
if (ZeroFillSize)
WriteZeros(ZeroFillSize - Str.size());
}
/// @}
void WriteHeader32(unsigned NumLoadCommands, unsigned LoadCommandsSize) {
// struct mach_header (28 bytes)
uint64_t Start = OS.tell();
(void) Start;
Write32(Header_Magic32);
// FIXME: Support cputype.
Write32(TargetMachOWriterInfo::HDR_CPU_TYPE_I386);
// FIXME: Support cpusubtype.
Write32(TargetMachOWriterInfo::HDR_CPU_SUBTYPE_I386_ALL);
Write32(HFT_Object);
// Object files have a single load command, the segment.
Write32(NumLoadCommands);
Write32(LoadCommandsSize);
Write32(0); // Flags
assert(OS.tell() - Start == Header32Size);
}
/// WriteSegmentLoadCommand32 - Write a 32-bit segment load command.
///
/// \arg NumSections - The number of sections in this segment.
/// \arg SectionDataSize - The total size of the sections.
void WriteSegmentLoadCommand32(unsigned NumSections,
uint64_t SectionDataStartOffset,
uint64_t SectionDataSize) {
// struct segment_command (56 bytes)
uint64_t Start = OS.tell();
(void) Start;
Write32(LCT_Segment);
Write32(SegmentLoadCommand32Size + NumSections * Section32Size);
WriteString("", 16);
Write32(0); // vmaddr
Write32(SectionDataSize); // vmsize
Write32(SectionDataStartOffset); // file offset
Write32(SectionDataSize); // file size
Write32(0x7); // maxprot
Write32(0x7); // initprot
Write32(NumSections);
Write32(0); // flags
assert(OS.tell() - Start == SegmentLoadCommand32Size);
}
void WriteSection32(const MCSectionData &SD, uint64_t FileOffset) {
// struct section (68 bytes)
uint64_t Start = OS.tell();
(void) Start;
// FIXME: cast<> support!
const MCSectionMachO &Section =
static_cast<const MCSectionMachO&>(SD.getSection());
WriteString(Section.getSectionName(), 16);
WriteString(Section.getSegmentName(), 16);
Write32(0); // address
Write32(SD.getFileSize()); // size
Write32(FileOffset);
assert(isPowerOf2_32(SD.getAlignment()) && "Invalid alignment!");
Write32(Log2_32(SD.getAlignment()));
Write32(0); // file offset of relocation entries
Write32(0); // number of relocation entrions
Write32(Section.getTypeAndAttributes());
Write32(0); // reserved1
Write32(Section.getStubSize()); // reserved2
assert(OS.tell() - Start == Section32Size);
}
void WriteSymtabLoadCommand(uint32_t SymbolOffset, uint32_t NumSymbols,
uint32_t StringTableOffset,
uint32_t StringTableSize) {
// struct symtab_command (24 bytes)
uint64_t Start = OS.tell();
(void) Start;
Write32(LCT_Symtab);
Write32(SymtabLoadCommandSize);
Write32(SymbolOffset);
Write32(NumSymbols);
Write32(StringTableOffset);
Write32(StringTableSize);
assert(OS.tell() - Start == SymtabLoadCommandSize);
}
void WriteDysymtabLoadCommand(uint32_t FirstLocalSymbol,
uint32_t NumLocalSymbols,
uint32_t FirstExternalSymbol,
uint32_t NumExternalSymbols,
uint32_t FirstUndefinedSymbol,
uint32_t NumUndefinedSymbols,
uint32_t IndirectSymbolOffset,
uint32_t NumIndirectSymbols) {
// struct dysymtab_command (80 bytes)
uint64_t Start = OS.tell();
(void) Start;
Write32(LCT_Dysymtab);
Write32(DysymtabLoadCommandSize);
Write32(FirstLocalSymbol);
Write32(NumLocalSymbols);
Write32(FirstExternalSymbol);
Write32(NumExternalSymbols);
Write32(FirstUndefinedSymbol);
Write32(NumUndefinedSymbols);
Write32(0); // tocoff
Write32(0); // ntoc
Write32(0); // modtaboff
Write32(0); // nmodtab
Write32(0); // extrefsymoff
Write32(0); // nextrefsyms
Write32(IndirectSymbolOffset);
Write32(NumIndirectSymbols);
Write32(0); // extreloff
Write32(0); // nextrel
Write32(0); // locreloff
Write32(0); // nlocrel
assert(OS.tell() - Start == DysymtabLoadCommandSize);
}
void WriteNlist32(MachSymbolData &MSD) {
MCSymbol &Symbol = MSD.SymbolData->getSymbol();
uint8_t Type = 0;
// Set the N_TYPE bits. See <mach-o/nlist.h>.
//
// FIXME: Are the prebound or indirect fields possible here?
if (Symbol.isUndefined())
Type = STT_Undefined;
else if (Symbol.isAbsolute())
Type = STT_Absolute;
else
Type = STT_Section;
// FIXME: Set STAB bits.
// FIXME: Set private external bit.
// Set external bit.
if (MSD.SymbolData->isExternal())
Type |= STF_External;
// struct nlist (12 bytes)
Write32(MSD.StringIndex);
Write8(Type);
Write8(MSD.SectionIndex);
Write16(0); // FIXME: Desc
Write32(0); // FIXME: Value
}
/// ComputeSymbolTable - Compute the symbol table data
///
/// \param StringTable [out] - The string table data.
/// \param StringIndexMap [out] - Map from symbol names to offsets in the
/// string table.
void ComputeSymbolTable(MCAssembler &Asm, SmallString<256> &StringTable,
std::vector<MachSymbolData> &LocalSymbolData,
std::vector<MachSymbolData> &ExternalSymbolData,
std::vector<MachSymbolData> &UndefinedSymbolData) {
// Build section lookup table.
DenseMap<const MCSection*, uint8_t> SectionIndexMap;
unsigned Index = 1;
for (MCAssembler::iterator it = Asm.begin(),
ie = Asm.end(); it != ie; ++it, ++Index)
SectionIndexMap[&it->getSection()] = Index;
assert(Index <= 256 && "Too many sections!");
// Index 0 is always the empty string.
StringMap<uint64_t> StringIndexMap;
StringTable += '\x00';
// Build the symbol arrays and the string table, but only for non-local
// symbols.
//
// The particular order that we collect the symbols and create the string
// table, then sort the symbols is chosen to match 'as'. Even though it
// doesn't matter for correctness, this is important for letting us diff .o
// files.
for (MCAssembler::symbol_iterator it = Asm.symbol_begin(),
ie = Asm.symbol_end(); it != ie; ++it) {
MCSymbol &Symbol = it->getSymbol();
if (!it->isExternal())
continue;
uint64_t &Entry = StringIndexMap[Symbol.getName()];
if (!Entry) {
Entry = StringTable.size();
StringTable += Symbol.getName();
StringTable += '\x00';
}
MachSymbolData MSD;
MSD.SymbolData = it;
MSD.StringIndex = Entry;
if (Symbol.isUndefined()) {
MSD.SectionIndex = 0;
UndefinedSymbolData.push_back(MSD);
} else if (Symbol.isAbsolute()) {
MSD.SectionIndex = 0;
ExternalSymbolData.push_back(MSD);
} else {
MSD.SectionIndex = SectionIndexMap.lookup(&Symbol.getSection());
assert(MSD.SectionIndex && "Invalid section index!");
ExternalSymbolData.push_back(MSD);
}
}
// Now add the data for local symbols.
for (MCAssembler::symbol_iterator it = Asm.symbol_begin(),
ie = Asm.symbol_end(); it != ie; ++it) {
MCSymbol &Symbol = it->getSymbol();
if (it->isExternal())
continue;
uint64_t &Entry = StringIndexMap[Symbol.getName()];
if (!Entry) {
Entry = StringTable.size();
StringTable += Symbol.getName();
StringTable += '\x00';
}
MachSymbolData MSD;
MSD.SymbolData = it;
MSD.StringIndex = Entry;
assert(!Symbol.isUndefined() && "Local symbol can not be undefined!");
if (Symbol.isAbsolute()) {
MSD.SectionIndex = 0;
LocalSymbolData.push_back(MSD);
} else {
MSD.SectionIndex = SectionIndexMap.lookup(&Symbol.getSection());
assert(MSD.SectionIndex && "Invalid section index!");
LocalSymbolData.push_back(MSD);
}
}
// External and undefined symbols are required to be in lexicographic order.
std::sort(ExternalSymbolData.begin(), ExternalSymbolData.end());
std::sort(UndefinedSymbolData.begin(), UndefinedSymbolData.end());
// The string table is padded to a multiple of 4.
//
// FIXME: Check to see if this varies per arch.
while (StringTable.size() % 4)
StringTable += '\x00';
}
void WriteObject(MCAssembler &Asm) {
unsigned NumSections = Asm.size();
// Compute symbol table information.
SmallString<256> StringTable;
std::vector<MachSymbolData> LocalSymbolData;
std::vector<MachSymbolData> ExternalSymbolData;
std::vector<MachSymbolData> UndefinedSymbolData;
unsigned NumSymbols = Asm.symbol_size();
// No symbol table command is written if there are no symbols.
if (NumSymbols)
ComputeSymbolTable(Asm, StringTable, LocalSymbolData, ExternalSymbolData,
UndefinedSymbolData);
// Compute the file offsets for all the sections in advance, so that we can
// write things out in order.
SmallVector<uint64_t, 16> SectionFileOffsets;
SectionFileOffsets.resize(NumSections);
// The section data starts after the header, the segment load command (and
// section headers) and the symbol table.
unsigned NumLoadCommands = 1;
uint64_t LoadCommandsSize =
SegmentLoadCommand32Size + NumSections * Section32Size;
// Add the symbol table load command sizes, if used.
if (NumSymbols) {
NumLoadCommands += 2;
LoadCommandsSize += SymtabLoadCommandSize + DysymtabLoadCommandSize;
}
uint64_t FileOffset = Header32Size + LoadCommandsSize;
uint64_t SectionDataStartOffset = FileOffset;
uint64_t SectionDataSize = 0;
unsigned Index = 0;
for (MCAssembler::iterator it = Asm.begin(),
ie = Asm.end(); it != ie; ++it, ++Index) {
SectionFileOffsets[Index] = FileOffset;
FileOffset += it->getFileSize();
SectionDataSize += it->getFileSize();
}
// Write the prolog, starting with the header and load command...
WriteHeader32(NumLoadCommands, LoadCommandsSize);
WriteSegmentLoadCommand32(NumSections, SectionDataStartOffset,
SectionDataSize);
// ... and then the section headers.
Index = 0;
for (MCAssembler::iterator it = Asm.begin(),
ie = Asm.end(); it != ie; ++it, ++Index)
WriteSection32(*it, SectionFileOffsets[Index]);
// Write the symbol table load command, if used.
if (NumSymbols) {
// The string table is written after all the section data.
uint64_t SymbolTableOffset = SectionDataStartOffset + SectionDataSize;
uint64_t StringTableOffset =
SymbolTableOffset + NumSymbols * Nlist32Size;
WriteSymtabLoadCommand(SymbolTableOffset, NumSymbols,
StringTableOffset, StringTable.size());
unsigned FirstLocalSymbol = 0;
unsigned NumLocalSymbols = LocalSymbolData.size();
unsigned FirstExternalSymbol = FirstLocalSymbol + NumLocalSymbols;
unsigned NumExternalSymbols = ExternalSymbolData.size();
unsigned FirstUndefinedSymbol = FirstExternalSymbol + NumExternalSymbols;
unsigned NumUndefinedSymbols = UndefinedSymbolData.size();
// FIXME: Get correct symbol indices and counts for indirect symbols.
unsigned IndirectSymbolOffset = 0;
unsigned NumIndirectSymbols = 0;
WriteDysymtabLoadCommand(FirstLocalSymbol, NumLocalSymbols,
FirstExternalSymbol, NumExternalSymbols,
FirstUndefinedSymbol, NumUndefinedSymbols,
IndirectSymbolOffset, NumIndirectSymbols);
}
// Write the actual section data.
for (MCAssembler::iterator it = Asm.begin(), ie = Asm.end(); it != ie; ++it)
WriteFileData(OS, *it, *this);
// Write the symbol table data, if used.
if (NumSymbols) {
// FIXME: Check that offsets match computed ones.
// FIXME: Some of these are ordered by name to help the linker.
// Write the symbol table entries.
for (unsigned i = 0, e = LocalSymbolData.size(); i != e; ++i)
WriteNlist32(LocalSymbolData[i]);
for (unsigned i = 0, e = ExternalSymbolData.size(); i != e; ++i)
WriteNlist32(ExternalSymbolData[i]);
for (unsigned i = 0, e = UndefinedSymbolData.size(); i != e; ++i)
WriteNlist32(UndefinedSymbolData[i]);
// Write the string table.
OS << StringTable.str();
}
}
};
/* *** */
MCFragment::MCFragment() : Kind(FragmentType(~0)) {
}
MCFragment::MCFragment(FragmentType _Kind, MCSectionData *SD)
: Kind(_Kind),
FileSize(~UINT64_C(0))
{
if (SD)
SD->getFragmentList().push_back(this);
}
MCFragment::~MCFragment() {
}
/* *** */
MCSectionData::MCSectionData() : Section(*(MCSection*)0) {}
MCSectionData::MCSectionData(const MCSection &_Section, MCAssembler *A)
: Section(_Section),
Alignment(1),
FileSize(~UINT64_C(0))
{
if (A)
A->getSectionList().push_back(this);
}
/* *** */
MCSymbolData::MCSymbolData() : Symbol(*(MCSymbol*)0) {}
MCSymbolData::MCSymbolData(MCSymbol &_Symbol, MCFragment *_Fragment,
uint64_t _Offset, MCAssembler *A)
: Symbol(_Symbol), Fragment(_Fragment), Offset(_Offset),
IsExternal(false)
{
if (A)
A->getSymbolList().push_back(this);
}
/* *** */
MCAssembler::MCAssembler(raw_ostream &_OS) : OS(_OS) {}
MCAssembler::~MCAssembler() {
}
void MCAssembler::LayoutSection(MCSectionData &SD) {
uint64_t Offset = 0;
for (MCSectionData::iterator it = SD.begin(), ie = SD.end(); it != ie; ++it) {
MCFragment &F = *it;
F.setOffset(Offset);
// Evaluate fragment size.
switch (F.getKind()) {
case MCFragment::FT_Align: {
MCAlignFragment &AF = cast<MCAlignFragment>(F);
uint64_t AlignedOffset = RoundUpToAlignment(Offset, AF.getAlignment());
uint64_t PaddingBytes = AlignedOffset - Offset;
if (PaddingBytes > AF.getMaxBytesToEmit())
AF.setFileSize(0);
else
AF.setFileSize(PaddingBytes);
break;
}
case MCFragment::FT_Data:
case MCFragment::FT_Fill:
F.setFileSize(F.getMaxFileSize());
break;
case MCFragment::FT_Org: {
MCOrgFragment &OF = cast<MCOrgFragment>(F);
if (!OF.getOffset().isAbsolute())
llvm_unreachable("FIXME: Not yet implemented!");
uint64_t OrgOffset = OF.getOffset().getConstant();
// FIXME: We need a way to communicate this error.
if (OrgOffset < Offset)
llvm_report_error("invalid .org offset '" + Twine(OrgOffset) +
"' (section offset '" + Twine(Offset) + "'");
F.setFileSize(OrgOffset - Offset);
break;
}
}
Offset += F.getFileSize();
}
// FIXME: Pad section?
SD.setFileSize(Offset);
}
/// WriteFileData - Write the \arg F data to the output file.
static void WriteFileData(raw_ostream &OS, const MCFragment &F,
MachObjectWriter &MOW) {
uint64_t Start = OS.tell();
(void) Start;
// FIXME: Embed in fragments instead?
switch (F.getKind()) {
case MCFragment::FT_Align: {
MCAlignFragment &AF = cast<MCAlignFragment>(F);
uint64_t Count = AF.getFileSize() / AF.getValueSize();
// FIXME: This error shouldn't actually occur (the front end should emit
// multiple .align directives to enforce the semantics it wants), but is
// severe enough that we want to report it. How to handle this?
if (Count * AF.getValueSize() != AF.getFileSize())
llvm_report_error("undefined .align directive, value size '" +
Twine(AF.getValueSize()) +
"' is not a divisor of padding size '" +
Twine(AF.getFileSize()) + "'");
for (uint64_t i = 0; i != Count; ++i) {
switch (AF.getValueSize()) {
default:
assert(0 && "Invalid size!");
case 1: MOW.Write8 (uint8_t (AF.getValue())); break;
case 2: MOW.Write16(uint16_t(AF.getValue())); break;
case 4: MOW.Write32(uint32_t(AF.getValue())); break;
case 8: MOW.Write64(uint64_t(AF.getValue())); break;
}
}
break;
}
case MCFragment::FT_Data:
OS << cast<MCDataFragment>(F).getContents().str();
break;
case MCFragment::FT_Fill: {
MCFillFragment &FF = cast<MCFillFragment>(F);
if (!FF.getValue().isAbsolute())
llvm_unreachable("FIXME: Not yet implemented!");
int64_t Value = FF.getValue().getConstant();
for (uint64_t i = 0, e = FF.getCount(); i != e; ++i) {
switch (FF.getValueSize()) {
default:
assert(0 && "Invalid size!");
case 1: MOW.Write8 (uint8_t (Value)); break;
case 2: MOW.Write16(uint16_t(Value)); break;
case 4: MOW.Write32(uint32_t(Value)); break;
case 8: MOW.Write64(uint64_t(Value)); break;
}
}
break;
}
case MCFragment::FT_Org: {
MCOrgFragment &OF = cast<MCOrgFragment>(F);
for (uint64_t i = 0, e = OF.getFileSize(); i != e; ++i)
MOW.Write8(uint8_t(OF.getValue()));
break;
}
}
assert(OS.tell() - Start == F.getFileSize());
}
/// WriteFileData - Write the \arg SD data to the output file.
static void WriteFileData(raw_ostream &OS, const MCSectionData &SD,
MachObjectWriter &MOW) {
uint64_t Start = OS.tell();
(void) Start;
for (MCSectionData::const_iterator it = SD.begin(),
ie = SD.end(); it != ie; ++it)
WriteFileData(OS, *it, MOW);
assert(OS.tell() - Start == SD.getFileSize());
}
void MCAssembler::Finish() {
// Layout the sections and fragments.
for (iterator it = begin(), ie = end(); it != ie; ++it)
LayoutSection(*it);
// Write the object file.
MachObjectWriter MOW(OS);
MOW.WriteObject(*this);
OS.flush();
}
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