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llvm-project/llvm/lib/CodeGen/MachOWriter.cpp

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//===-- MachOWriter.cpp - Target-independent Mach-O Writer code -----------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements the target-independent Mach-O writer. This file writes
// out the Mach-O file in the following order:
//
// #1 FatHeader (universal-only)
// #2 FatArch (universal-only, 1 per universal arch)
// Per arch:
// #3 Header
// #4 Load Commands
// #5 Sections
// #6 Relocations
// #7 Symbols
// #8 Strings
//
//===----------------------------------------------------------------------===//
#include "MachOWriter.h"
#include "llvm/Constants.h"
#include "llvm/DerivedTypes.h"
#include "llvm/Module.h"
#include "llvm/PassManager.h"
#include "llvm/CodeGen/FileWriters.h"
#include "llvm/CodeGen/MachineCodeEmitter.h"
#include "llvm/CodeGen/MachineConstantPool.h"
#include "llvm/CodeGen/MachineJumpTableInfo.h"
#include "llvm/Target/TargetAsmInfo.h"
#include "llvm/Target/TargetJITInfo.h"
#include "llvm/Support/Mangler.h"
#include "llvm/Support/MathExtras.h"
#include "llvm/Support/OutputBuffer.h"
#include "llvm/Support/Streams.h"
#include "llvm/Support/raw_ostream.h"
#include <algorithm>
#include <cstring>
using namespace llvm;
/// AddMachOWriter - Concrete function to add the Mach-O writer to the function
/// pass manager.
MachineCodeEmitter *llvm::AddMachOWriter(PassManagerBase &PM,
raw_ostream &O,
TargetMachine &TM) {
MachOWriter *MOW = new MachOWriter(O, TM);
PM.add(MOW);
return &MOW->getMachineCodeEmitter();
}
//===----------------------------------------------------------------------===//
// MachOCodeEmitter Implementation
//===----------------------------------------------------------------------===//
namespace llvm {
/// MachOCodeEmitter - This class is used by the MachOWriter to emit the code
/// for functions to the Mach-O file.
class MachOCodeEmitter : public MachineCodeEmitter {
MachOWriter &MOW;
/// Target machine description.
TargetMachine &TM;
/// is64Bit/isLittleEndian - This information is inferred from the target
/// machine directly, indicating what header values and flags to set.
bool is64Bit, isLittleEndian;
/// Relocations - These are the relocations that the function needs, as
/// emitted.
std::vector<MachineRelocation> Relocations;
/// CPLocations - This is a map of constant pool indices to offsets from the
/// start of the section for that constant pool index.
std::vector<intptr_t> CPLocations;
/// CPSections - This is a map of constant pool indices to the MachOSection
/// containing the constant pool entry for that index.
std::vector<unsigned> CPSections;
/// JTLocations - This is a map of jump table indices to offsets from the
/// start of the section for that jump table index.
std::vector<intptr_t> JTLocations;
/// MBBLocations - This vector is a mapping from MBB ID's to their address.
/// It is filled in by the StartMachineBasicBlock callback and queried by
/// the getMachineBasicBlockAddress callback.
std::vector<intptr_t> MBBLocations;
public:
MachOCodeEmitter(MachOWriter &mow) : MOW(mow), TM(MOW.TM) {
is64Bit = TM.getTargetData()->getPointerSizeInBits() == 64;
isLittleEndian = TM.getTargetData()->isLittleEndian();
}
virtual void startFunction(MachineFunction &MF);
virtual bool finishFunction(MachineFunction &MF);
virtual void addRelocation(const MachineRelocation &MR) {
Relocations.push_back(MR);
}
void emitConstantPool(MachineConstantPool *MCP);
void emitJumpTables(MachineJumpTableInfo *MJTI);
virtual intptr_t getConstantPoolEntryAddress(unsigned Index) const {
assert(CPLocations.size() > Index && "CP not emitted!");
return CPLocations[Index];
}
virtual intptr_t getJumpTableEntryAddress(unsigned Index) const {
assert(JTLocations.size() > Index && "JT not emitted!");
return JTLocations[Index];
}
virtual void StartMachineBasicBlock(MachineBasicBlock *MBB) {
if (MBBLocations.size() <= (unsigned)MBB->getNumber())
MBBLocations.resize((MBB->getNumber()+1)*2);
MBBLocations[MBB->getNumber()] = getCurrentPCOffset();
}
virtual intptr_t getMachineBasicBlockAddress(MachineBasicBlock *MBB) const {
assert(MBBLocations.size() > (unsigned)MBB->getNumber() &&
MBBLocations[MBB->getNumber()] && "MBB not emitted!");
return MBBLocations[MBB->getNumber()];
}
virtual intptr_t getLabelAddress(uint64_t Label) const {
assert(0 && "get Label not implemented");
abort();
return 0;
}
virtual void emitLabel(uint64_t LabelID) {
assert(0 && "emit Label not implemented");
abort();
}
virtual void setModuleInfo(llvm::MachineModuleInfo* MMI) { }
/// JIT SPECIFIC FUNCTIONS - DO NOT IMPLEMENT THESE HERE!
virtual void startGVStub(const GlobalValue* F, unsigned StubSize,
unsigned Alignment = 1) {
assert(0 && "JIT specific function called!");
abort();
}
virtual void *finishGVStub(const GlobalValue* F) {
assert(0 && "JIT specific function called!");
abort();
return 0;
}
};
}
/// startFunction - This callback is invoked when a new machine function is
/// about to be emitted.
void MachOCodeEmitter::startFunction(MachineFunction &MF) {
const TargetData *TD = TM.getTargetData();
const Function *F = MF.getFunction();
// Align the output buffer to the appropriate alignment, power of 2.
unsigned FnAlign = F->getAlignment();
unsigned TDAlign = TD->getPrefTypeAlignment(F->getType());
unsigned Align = Log2_32(std::max(FnAlign, TDAlign));
assert(!(Align & (Align-1)) && "Alignment is not a power of two!");
// Get the Mach-O Section that this function belongs in.
MachOWriter::MachOSection *MOS = MOW.getTextSection();
// FIXME: better memory management
MOS->SectionData.reserve(4096);
BufferBegin = &MOS->SectionData[0];
BufferEnd = BufferBegin + MOS->SectionData.capacity();
// Upgrade the section alignment if required.
if (MOS->align < Align) MOS->align = Align;
// Round the size up to the correct alignment for starting the new function.
if ((MOS->size & ((1 << Align) - 1)) != 0) {
MOS->size += (1 << Align);
MOS->size &= ~((1 << Align) - 1);
}
// FIXME: Using MOS->size directly here instead of calculating it from the
// output buffer size (impossible because the code emitter deals only in raw
// bytes) forces us to manually synchronize size and write padding zero bytes
// to the output buffer for all non-text sections. For text sections, we do
// not synchonize the output buffer, and we just blow up if anyone tries to
// write non-code to it. An assert should probably be added to
// AddSymbolToSection to prevent calling it on the text section.
CurBufferPtr = BufferBegin + MOS->size;
// Clear per-function data structures.
CPLocations.clear();
CPSections.clear();
JTLocations.clear();
MBBLocations.clear();
}
/// finishFunction - This callback is invoked after the function is completely
/// finished.
bool MachOCodeEmitter::finishFunction(MachineFunction &MF) {
// Get the Mach-O Section that this function belongs in.
MachOWriter::MachOSection *MOS = MOW.getTextSection();
// Get a symbol for the function to add to the symbol table
// FIXME: it seems like we should call something like AddSymbolToSection
// in startFunction rather than changing the section size and symbol n_value
// here.
const GlobalValue *FuncV = MF.getFunction();
MachOSym FnSym(FuncV, MOW.Mang->getValueName(FuncV), MOS->Index, TM);
FnSym.n_value = MOS->size;
MOS->size = CurBufferPtr - BufferBegin;
// Emit constant pool to appropriate section(s)
emitConstantPool(MF.getConstantPool());
// Emit jump tables to appropriate section
emitJumpTables(MF.getJumpTableInfo());
// If we have emitted any relocations to function-specific objects such as
// basic blocks, constant pools entries, or jump tables, record their
// addresses now so that we can rewrite them with the correct addresses
// later.
for (unsigned i = 0, e = Relocations.size(); i != e; ++i) {
MachineRelocation &MR = Relocations[i];
intptr_t Addr;
if (MR.isBasicBlock()) {
Addr = getMachineBasicBlockAddress(MR.getBasicBlock());
MR.setConstantVal(MOS->Index);
MR.setResultPointer((void*)Addr);
} else if (MR.isJumpTableIndex()) {
Addr = getJumpTableEntryAddress(MR.getJumpTableIndex());
MR.setConstantVal(MOW.getJumpTableSection()->Index);
MR.setResultPointer((void*)Addr);
} else if (MR.isConstantPoolIndex()) {
Addr = getConstantPoolEntryAddress(MR.getConstantPoolIndex());
MR.setConstantVal(CPSections[MR.getConstantPoolIndex()]);
MR.setResultPointer((void*)Addr);
} else if (MR.isGlobalValue()) {
// FIXME: This should be a set or something that uniques
MOW.PendingGlobals.push_back(MR.getGlobalValue());
} else {
assert(0 && "Unhandled relocation type");
}
MOS->Relocations.push_back(MR);
}
Relocations.clear();
// Finally, add it to the symtab.
MOW.SymbolTable.push_back(FnSym);
return false;
}
/// emitConstantPool - For each constant pool entry, figure out which section
/// the constant should live in, allocate space for it, and emit it to the
/// Section data buffer.
void MachOCodeEmitter::emitConstantPool(MachineConstantPool *MCP) {
const std::vector<MachineConstantPoolEntry> &CP = MCP->getConstants();
if (CP.empty()) return;
// FIXME: handle PIC codegen
bool isPIC = TM.getRelocationModel() == Reloc::PIC_;
assert(!isPIC && "PIC codegen not yet handled for mach-o jump tables!");
// Although there is no strict necessity that I am aware of, we will do what
// gcc for OS X does and put each constant pool entry in a section of constant
// objects of a certain size. That means that float constants go in the
// literal4 section, and double objects go in literal8, etc.
//
// FIXME: revisit this decision if we ever do the "stick everything into one
// "giant object for PIC" optimization.
for (unsigned i = 0, e = CP.size(); i != e; ++i) {
const Type *Ty = CP[i].getType();
unsigned Size = TM.getTargetData()->getABITypeSize(Ty);
MachOWriter::MachOSection *Sec = MOW.getConstSection(CP[i].Val.ConstVal);
OutputBuffer SecDataOut(Sec->SectionData, is64Bit, isLittleEndian);
CPLocations.push_back(Sec->SectionData.size());
CPSections.push_back(Sec->Index);
// FIXME: remove when we have unified size + output buffer
Sec->size += Size;
// Allocate space in the section for the global.
// FIXME: need alignment?
// FIXME: share between here and AddSymbolToSection?
for (unsigned j = 0; j < Size; ++j)
SecDataOut.outbyte(0);
MOW.InitMem(CP[i].Val.ConstVal, &Sec->SectionData[0], CPLocations[i],
TM.getTargetData(), Sec->Relocations);
}
}
/// emitJumpTables - Emit all the jump tables for a given jump table info
/// record to the appropriate section.
void MachOCodeEmitter::emitJumpTables(MachineJumpTableInfo *MJTI) {
const std::vector<MachineJumpTableEntry> &JT = MJTI->getJumpTables();
if (JT.empty()) return;
// FIXME: handle PIC codegen
bool isPIC = TM.getRelocationModel() == Reloc::PIC_;
assert(!isPIC && "PIC codegen not yet handled for mach-o jump tables!");
MachOWriter::MachOSection *Sec = MOW.getJumpTableSection();
unsigned TextSecIndex = MOW.getTextSection()->Index;
OutputBuffer SecDataOut(Sec->SectionData, is64Bit, isLittleEndian);
for (unsigned i = 0, e = JT.size(); i != e; ++i) {
// For each jump table, record its offset from the start of the section,
// reserve space for the relocations to the MBBs, and add the relocations.
const std::vector<MachineBasicBlock*> &MBBs = JT[i].MBBs;
JTLocations.push_back(Sec->SectionData.size());
for (unsigned mi = 0, me = MBBs.size(); mi != me; ++mi) {
MachineRelocation MR(MOW.GetJTRelocation(Sec->SectionData.size(),
MBBs[mi]));
MR.setResultPointer((void *)JTLocations[i]);
MR.setConstantVal(TextSecIndex);
Sec->Relocations.push_back(MR);
SecDataOut.outaddr(0);
}
}
// FIXME: remove when we have unified size + output buffer
Sec->size = Sec->SectionData.size();
}
//===----------------------------------------------------------------------===//
// MachOWriter Implementation
//===----------------------------------------------------------------------===//
char MachOWriter::ID = 0;
MachOWriter::MachOWriter(raw_ostream &o, TargetMachine &tm)
: MachineFunctionPass(&ID), O(o), TM(tm) {
is64Bit = TM.getTargetData()->getPointerSizeInBits() == 64;
isLittleEndian = TM.getTargetData()->isLittleEndian();
// Create the machine code emitter object for this target.
MCE = new MachOCodeEmitter(*this);
}
MachOWriter::~MachOWriter() {
delete MCE;
}
void MachOWriter::AddSymbolToSection(MachOSection *Sec, GlobalVariable *GV) {
const Type *Ty = GV->getType()->getElementType();
unsigned Size = TM.getTargetData()->getABITypeSize(Ty);
unsigned Align = TM.getTargetData()->getPreferredAlignment(GV);
// Reserve space in the .bss section for this symbol while maintaining the
// desired section alignment, which must be at least as much as required by
// this symbol.
OutputBuffer SecDataOut(Sec->SectionData, is64Bit, isLittleEndian);
if (Align) {
uint64_t OrigSize = Sec->size;
Align = Log2_32(Align);
Sec->align = std::max(unsigned(Sec->align), Align);
Sec->size = (Sec->size + Align - 1) & ~(Align-1);
// Add alignment padding to buffer as well.
// FIXME: remove when we have unified size + output buffer
unsigned AlignedSize = Sec->size - OrigSize;
for (unsigned i = 0; i < AlignedSize; ++i)
SecDataOut.outbyte(0);
}
// Globals without external linkage apparently do not go in the symbol table.
if (GV->getLinkage() != GlobalValue::InternalLinkage) {
MachOSym Sym(GV, Mang->getValueName(GV), Sec->Index, TM);
Sym.n_value = Sec->size;
SymbolTable.push_back(Sym);
}
// Record the offset of the symbol, and then allocate space for it.
// FIXME: remove when we have unified size + output buffer
Sec->size += Size;
// Now that we know what section the GlovalVariable is going to be emitted
// into, update our mappings.
// FIXME: We may also need to update this when outputting non-GlobalVariable
// GlobalValues such as functions.
GVSection[GV] = Sec;
GVOffset[GV] = Sec->SectionData.size();
// Allocate space in the section for the global.
for (unsigned i = 0; i < Size; ++i)
SecDataOut.outbyte(0);
}
void MachOWriter::EmitGlobal(GlobalVariable *GV) {
const Type *Ty = GV->getType()->getElementType();
unsigned Size = TM.getTargetData()->getABITypeSize(Ty);
bool NoInit = !GV->hasInitializer();
// If this global has a zero initializer, it is part of the .bss or common
// section.
if (NoInit || GV->getInitializer()->isNullValue()) {
// If this global is part of the common block, add it now. Variables are
// part of the common block if they are zero initialized and allowed to be
// merged with other symbols.
if (NoInit || GV->hasLinkOnceLinkage() || GV->hasWeakLinkage() ||
GV->hasCommonLinkage()) {
MachOSym ExtOrCommonSym(GV, Mang->getValueName(GV), MachOSym::NO_SECT,TM);
// For undefined (N_UNDF) external (N_EXT) types, n_value is the size in
// bytes of the symbol.
ExtOrCommonSym.n_value = Size;
SymbolTable.push_back(ExtOrCommonSym);
// Remember that we've seen this symbol
GVOffset[GV] = Size;
return;
}
// Otherwise, this symbol is part of the .bss section.
MachOSection *BSS = getBSSSection();
AddSymbolToSection(BSS, GV);
return;
}
// Scalar read-only data goes in a literal section if the scalar is 4, 8, or
// 16 bytes, or a cstring. Other read only data goes into a regular const
// section. Read-write data goes in the data section.
MachOSection *Sec = GV->isConstant() ? getConstSection(GV->getInitializer()) :
getDataSection();
AddSymbolToSection(Sec, GV);
InitMem(GV->getInitializer(), &Sec->SectionData[0], GVOffset[GV],
TM.getTargetData(), Sec->Relocations);
}
bool MachOWriter::runOnMachineFunction(MachineFunction &MF) {
// Nothing to do here, this is all done through the MCE object.
return false;
}
bool MachOWriter::doInitialization(Module &M) {
// Set the magic value, now that we know the pointer size and endianness
Header.setMagic(isLittleEndian, is64Bit);
// Set the file type
// FIXME: this only works for object files, we do not support the creation
// of dynamic libraries or executables at this time.
Header.filetype = MachOHeader::MH_OBJECT;
Mang = new Mangler(M);
return false;
}
/// doFinalization - Now that the module has been completely processed, emit
/// the Mach-O file to 'O'.
bool MachOWriter::doFinalization(Module &M) {
// FIXME: we don't handle debug info yet, we should probably do that.
// Okay, the.text section has been completed, build the .data, .bss, and
// "common" sections next.
for (Module::global_iterator I = M.global_begin(), E = M.global_end();
I != E; ++I)
EmitGlobal(I);
// Emit the header and load commands.
EmitHeaderAndLoadCommands();
// Emit the various sections and their relocation info.
EmitSections();
// Write the symbol table and the string table to the end of the file.
O.write((char*)&SymT[0], SymT.size());
O.write((char*)&StrT[0], StrT.size());
// We are done with the abstract symbols.
SectionList.clear();
SymbolTable.clear();
DynamicSymbolTable.clear();
// Release the name mangler object.
delete Mang; Mang = 0;
return false;
}
void MachOWriter::EmitHeaderAndLoadCommands() {
// Step #0: Fill in the segment load command size, since we need it to figure
// out the rest of the header fields
MachOSegment SEG("", is64Bit);
SEG.nsects = SectionList.size();
SEG.cmdsize = SEG.cmdSize(is64Bit) +
SEG.nsects * SectionList[0]->cmdSize(is64Bit);
// Step #1: calculate the number of load commands. We always have at least
// one, for the LC_SEGMENT load command, plus two for the normal
// and dynamic symbol tables, if there are any symbols.
Header.ncmds = SymbolTable.empty() ? 1 : 3;
// Step #2: calculate the size of the load commands
Header.sizeofcmds = SEG.cmdsize;
if (!SymbolTable.empty())
Header.sizeofcmds += SymTab.cmdsize + DySymTab.cmdsize;
// Step #3: write the header to the file
// Local alias to shortenify coming code.
DataBuffer &FH = Header.HeaderData;
OutputBuffer FHOut(FH, is64Bit, isLittleEndian);
FHOut.outword(Header.magic);
FHOut.outword(TM.getMachOWriterInfo()->getCPUType());
FHOut.outword(TM.getMachOWriterInfo()->getCPUSubType());
FHOut.outword(Header.filetype);
FHOut.outword(Header.ncmds);
FHOut.outword(Header.sizeofcmds);
FHOut.outword(Header.flags);
if (is64Bit)
FHOut.outword(Header.reserved);
// Step #4: Finish filling in the segment load command and write it out
for (std::vector<MachOSection*>::iterator I = SectionList.begin(),
E = SectionList.end(); I != E; ++I)
SEG.filesize += (*I)->size;
SEG.vmsize = SEG.filesize;
SEG.fileoff = Header.cmdSize(is64Bit) + Header.sizeofcmds;
FHOut.outword(SEG.cmd);
FHOut.outword(SEG.cmdsize);
FHOut.outstring(SEG.segname, 16);
FHOut.outaddr(SEG.vmaddr);
FHOut.outaddr(SEG.vmsize);
FHOut.outaddr(SEG.fileoff);
FHOut.outaddr(SEG.filesize);
FHOut.outword(SEG.maxprot);
FHOut.outword(SEG.initprot);
FHOut.outword(SEG.nsects);
FHOut.outword(SEG.flags);
// Step #5: Finish filling in the fields of the MachOSections
uint64_t currentAddr = 0;
for (std::vector<MachOSection*>::iterator I = SectionList.begin(),
E = SectionList.end(); I != E; ++I) {
MachOSection *MOS = *I;
MOS->addr = currentAddr;
MOS->offset = currentAddr + SEG.fileoff;
// FIXME: do we need to do something with alignment here?
currentAddr += MOS->size;
}
// Step #6: Emit the symbol table to temporary buffers, so that we know the
// size of the string table when we write the next load command. This also
// sorts and assigns indices to each of the symbols, which is necessary for
// emitting relocations to externally-defined objects.
BufferSymbolAndStringTable();
// Step #7: Calculate the number of relocations for each section and write out
// the section commands for each section
currentAddr += SEG.fileoff;
for (std::vector<MachOSection*>::iterator I = SectionList.begin(),
E = SectionList.end(); I != E; ++I) {
MachOSection *MOS = *I;
// Convert the relocations to target-specific relocations, and fill in the
// relocation offset for this section.
CalculateRelocations(*MOS);
MOS->reloff = MOS->nreloc ? currentAddr : 0;
currentAddr += MOS->nreloc * 8;
// write the finalized section command to the output buffer
FHOut.outstring(MOS->sectname, 16);
FHOut.outstring(MOS->segname, 16);
FHOut.outaddr(MOS->addr);
FHOut.outaddr(MOS->size);
FHOut.outword(MOS->offset);
FHOut.outword(MOS->align);
FHOut.outword(MOS->reloff);
FHOut.outword(MOS->nreloc);
FHOut.outword(MOS->flags);
FHOut.outword(MOS->reserved1);
FHOut.outword(MOS->reserved2);
if (is64Bit)
FHOut.outword(MOS->reserved3);
}
// Step #8: Emit LC_SYMTAB/LC_DYSYMTAB load commands
SymTab.symoff = currentAddr;
SymTab.nsyms = SymbolTable.size();
SymTab.stroff = SymTab.symoff + SymT.size();
SymTab.strsize = StrT.size();
FHOut.outword(SymTab.cmd);
FHOut.outword(SymTab.cmdsize);
FHOut.outword(SymTab.symoff);
FHOut.outword(SymTab.nsyms);
FHOut.outword(SymTab.stroff);
FHOut.outword(SymTab.strsize);
// FIXME: set DySymTab fields appropriately
// We should probably just update these in BufferSymbolAndStringTable since
// thats where we're partitioning up the different kinds of symbols.
FHOut.outword(DySymTab.cmd);
FHOut.outword(DySymTab.cmdsize);
FHOut.outword(DySymTab.ilocalsym);
FHOut.outword(DySymTab.nlocalsym);
FHOut.outword(DySymTab.iextdefsym);
FHOut.outword(DySymTab.nextdefsym);
FHOut.outword(DySymTab.iundefsym);
FHOut.outword(DySymTab.nundefsym);
FHOut.outword(DySymTab.tocoff);
FHOut.outword(DySymTab.ntoc);
FHOut.outword(DySymTab.modtaboff);
FHOut.outword(DySymTab.nmodtab);
FHOut.outword(DySymTab.extrefsymoff);
FHOut.outword(DySymTab.nextrefsyms);
FHOut.outword(DySymTab.indirectsymoff);
FHOut.outword(DySymTab.nindirectsyms);
FHOut.outword(DySymTab.extreloff);
FHOut.outword(DySymTab.nextrel);
FHOut.outword(DySymTab.locreloff);
FHOut.outword(DySymTab.nlocrel);
O.write((char*)&FH[0], FH.size());
}
/// EmitSections - Now that we have constructed the file header and load
/// commands, emit the data for each section to the file.
void MachOWriter::EmitSections() {
for (std::vector<MachOSection*>::iterator I = SectionList.begin(),
E = SectionList.end(); I != E; ++I)
// Emit the contents of each section
O.write((char*)&(*I)->SectionData[0], (*I)->size);
for (std::vector<MachOSection*>::iterator I = SectionList.begin(),
E = SectionList.end(); I != E; ++I)
// Emit the relocation entry data for each section.
O.write((char*)&(*I)->RelocBuffer[0], (*I)->RelocBuffer.size());
}
/// PartitionByLocal - Simple boolean predicate that returns true if Sym is
/// a local symbol rather than an external symbol.
bool MachOWriter::PartitionByLocal(const MachOSym &Sym) {
return (Sym.n_type & (MachOSym::N_EXT | MachOSym::N_PEXT)) == 0;
}
/// PartitionByDefined - Simple boolean predicate that returns true if Sym is
/// defined in this module.
bool MachOWriter::PartitionByDefined(const MachOSym &Sym) {
// FIXME: Do N_ABS or N_INDR count as defined?
return (Sym.n_type & MachOSym::N_SECT) == MachOSym::N_SECT;
}
/// BufferSymbolAndStringTable - Sort the symbols we encountered and assign them
/// each a string table index so that they appear in the correct order in the
/// output file.
void MachOWriter::BufferSymbolAndStringTable() {
// The order of the symbol table is:
// 1. local symbols
// 2. defined external symbols (sorted by name)
// 3. undefined external symbols (sorted by name)
// Before sorting the symbols, check the PendingGlobals for any undefined
// globals that need to be put in the symbol table.
for (std::vector<GlobalValue*>::iterator I = PendingGlobals.begin(),
E = PendingGlobals.end(); I != E; ++I) {
if (GVOffset[*I] == 0 && GVSection[*I] == 0) {
MachOSym UndfSym(*I, Mang->getValueName(*I), MachOSym::NO_SECT, TM);
SymbolTable.push_back(UndfSym);
GVOffset[*I] = -1;
}
}
// Sort the symbols by name, so that when we partition the symbols by scope
// of definition, we won't have to sort by name within each partition.
std::sort(SymbolTable.begin(), SymbolTable.end(), MachOSymCmp());
// Parition the symbol table entries so that all local symbols come before
// all symbols with external linkage. { 1 | 2 3 }
std::partition(SymbolTable.begin(), SymbolTable.end(), PartitionByLocal);
// Advance iterator to beginning of external symbols and partition so that
// all external symbols defined in this module come before all external
// symbols defined elsewhere. { 1 | 2 | 3 }
for (std::vector<MachOSym>::iterator I = SymbolTable.begin(),
E = SymbolTable.end(); I != E; ++I) {
if (!PartitionByLocal(*I)) {
std::partition(I, E, PartitionByDefined);
break;
}
}
// Calculate the starting index for each of the local, extern defined, and
// undefined symbols, as well as the number of each to put in the LC_DYSYMTAB
// load command.
for (std::vector<MachOSym>::iterator I = SymbolTable.begin(),
E = SymbolTable.end(); I != E; ++I) {
if (PartitionByLocal(*I)) {
++DySymTab.nlocalsym;
++DySymTab.iextdefsym;
++DySymTab.iundefsym;
} else if (PartitionByDefined(*I)) {
++DySymTab.nextdefsym;
++DySymTab.iundefsym;
} else {
++DySymTab.nundefsym;
}
}
// Write out a leading zero byte when emitting string table, for n_strx == 0
// which means an empty string.
OutputBuffer StrTOut(StrT, is64Bit, isLittleEndian);
StrTOut.outbyte(0);
// The order of the string table is:
// 1. strings for external symbols
// 2. strings for local symbols
// Since this is the opposite order from the symbol table, which we have just
// sorted, we can walk the symbol table backwards to output the string table.
for (std::vector<MachOSym>::reverse_iterator I = SymbolTable.rbegin(),
E = SymbolTable.rend(); I != E; ++I) {
if (I->GVName == "") {
I->n_strx = 0;
} else {
I->n_strx = StrT.size();
StrTOut.outstring(I->GVName, I->GVName.length()+1);
}
}
OutputBuffer SymTOut(SymT, is64Bit, isLittleEndian);
unsigned index = 0;
for (std::vector<MachOSym>::iterator I = SymbolTable.begin(),
E = SymbolTable.end(); I != E; ++I, ++index) {
// Add the section base address to the section offset in the n_value field
// to calculate the full address.
// FIXME: handle symbols where the n_value field is not the address
GlobalValue *GV = const_cast<GlobalValue*>(I->GV);
if (GV && GVSection[GV])
I->n_value += GVSection[GV]->addr;
if (GV && (GVOffset[GV] == -1))
GVOffset[GV] = index;
// Emit nlist to buffer
SymTOut.outword(I->n_strx);
SymTOut.outbyte(I->n_type);
SymTOut.outbyte(I->n_sect);
SymTOut.outhalf(I->n_desc);
SymTOut.outaddr(I->n_value);
}
}
/// CalculateRelocations - For each MachineRelocation in the current section,
/// calculate the index of the section containing the object to be relocated,
/// and the offset into that section. From this information, create the
/// appropriate target-specific MachORelocation type and add buffer it to be
/// written out after we are finished writing out sections.
void MachOWriter::CalculateRelocations(MachOSection &MOS) {
for (unsigned i = 0, e = MOS.Relocations.size(); i != e; ++i) {
MachineRelocation &MR = MOS.Relocations[i];
unsigned TargetSection = MR.getConstantVal();
unsigned TargetAddr = 0;
unsigned TargetIndex = 0;
// This is a scattered relocation entry if it points to a global value with
// a non-zero offset.
bool Scattered = false;
bool Extern = false;
// Since we may not have seen the GlobalValue we were interested in yet at
// the time we emitted the relocation for it, fix it up now so that it
// points to the offset into the correct section.
if (MR.isGlobalValue()) {
GlobalValue *GV = MR.getGlobalValue();
MachOSection *MOSPtr = GVSection[GV];
intptr_t Offset = GVOffset[GV];
// If we have never seen the global before, it must be to a symbol
// defined in another module (N_UNDF).
if (!MOSPtr) {
// FIXME: need to append stub suffix
Extern = true;
TargetAddr = 0;
TargetIndex = GVOffset[GV];
} else {
Scattered = TargetSection != 0;
TargetSection = MOSPtr->Index;
}
MR.setResultPointer((void*)Offset);
}
// If the symbol is locally defined, pass in the address of the section and
// the section index to the code which will generate the target relocation.
if (!Extern) {
MachOSection &To = *SectionList[TargetSection - 1];
TargetAddr = To.addr;
TargetIndex = To.Index;
}
OutputBuffer RelocOut(MOS.RelocBuffer, is64Bit, isLittleEndian);
OutputBuffer SecOut(MOS.SectionData, is64Bit, isLittleEndian);
MOS.nreloc += GetTargetRelocation(MR, MOS.Index, TargetAddr, TargetIndex,
RelocOut, SecOut, Scattered, Extern);
}
}
// InitMem - Write the value of a Constant to the specified memory location,
// converting it into bytes and relocations.
void MachOWriter::InitMem(const Constant *C, void *Addr, intptr_t Offset,
const TargetData *TD,
std::vector<MachineRelocation> &MRs) {
typedef std::pair<const Constant*, intptr_t> CPair;
std::vector<CPair> WorkList;
WorkList.push_back(CPair(C,(intptr_t)Addr + Offset));
intptr_t ScatteredOffset = 0;
while (!WorkList.empty()) {
const Constant *PC = WorkList.back().first;
intptr_t PA = WorkList.back().second;
WorkList.pop_back();
if (isa<UndefValue>(PC)) {
continue;
} else if (const ConstantVector *CP = dyn_cast<ConstantVector>(PC)) {
unsigned ElementSize =
TD->getABITypeSize(CP->getType()->getElementType());
for (unsigned i = 0, e = CP->getNumOperands(); i != e; ++i)
WorkList.push_back(CPair(CP->getOperand(i), PA+i*ElementSize));
} else if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(PC)) {
//
// FIXME: Handle ConstantExpression. See EE::getConstantValue()
//
switch (CE->getOpcode()) {
case Instruction::GetElementPtr: {
SmallVector<Value*, 8> Indices(CE->op_begin()+1, CE->op_end());
ScatteredOffset = TD->getIndexedOffset(CE->getOperand(0)->getType(),
&Indices[0], Indices.size());
WorkList.push_back(CPair(CE->getOperand(0), PA));
break;
}
case Instruction::Add:
default:
cerr << "ConstantExpr not handled as global var init: " << *CE << "\n";
abort();
break;
}
} else if (PC->getType()->isSingleValueType()) {
unsigned char *ptr = (unsigned char *)PA;
switch (PC->getType()->getTypeID()) {
case Type::IntegerTyID: {
unsigned NumBits = cast<IntegerType>(PC->getType())->getBitWidth();
uint64_t val = cast<ConstantInt>(PC)->getZExtValue();
if (NumBits <= 8)
ptr[0] = val;
else if (NumBits <= 16) {
if (TD->isBigEndian())
val = ByteSwap_16(val);
ptr[0] = val;
ptr[1] = val >> 8;
} else if (NumBits <= 32) {
if (TD->isBigEndian())
val = ByteSwap_32(val);
ptr[0] = val;
ptr[1] = val >> 8;
ptr[2] = val >> 16;
ptr[3] = val >> 24;
} else if (NumBits <= 64) {
if (TD->isBigEndian())
val = ByteSwap_64(val);
ptr[0] = val;
ptr[1] = val >> 8;
ptr[2] = val >> 16;
ptr[3] = val >> 24;
ptr[4] = val >> 32;
ptr[5] = val >> 40;
ptr[6] = val >> 48;
ptr[7] = val >> 56;
} else {
assert(0 && "Not implemented: bit widths > 64");
}
break;
}
case Type::FloatTyID: {
uint32_t val = cast<ConstantFP>(PC)->getValueAPF().bitcastToAPInt().
getZExtValue();
if (TD->isBigEndian())
val = ByteSwap_32(val);
ptr[0] = val;
ptr[1] = val >> 8;
ptr[2] = val >> 16;
ptr[3] = val >> 24;
break;
}
case Type::DoubleTyID: {
uint64_t val = cast<ConstantFP>(PC)->getValueAPF().bitcastToAPInt().
getZExtValue();
if (TD->isBigEndian())
val = ByteSwap_64(val);
ptr[0] = val;
ptr[1] = val >> 8;
ptr[2] = val >> 16;
ptr[3] = val >> 24;
ptr[4] = val >> 32;
ptr[5] = val >> 40;
ptr[6] = val >> 48;
ptr[7] = val >> 56;
break;
}
case Type::PointerTyID:
if (isa<ConstantPointerNull>(PC))
memset(ptr, 0, TD->getPointerSize());
else if (const GlobalValue* GV = dyn_cast<GlobalValue>(PC)) {
// FIXME: what about function stubs?
MRs.push_back(MachineRelocation::getGV(PA-(intptr_t)Addr,
MachineRelocation::VANILLA,
const_cast<GlobalValue*>(GV),
ScatteredOffset));
ScatteredOffset = 0;
} else
assert(0 && "Unknown constant pointer type!");
break;
default:
cerr << "ERROR: Constant unimp for type: " << *PC->getType() << "\n";
abort();
}
} else if (isa<ConstantAggregateZero>(PC)) {
memset((void*)PA, 0, (size_t)TD->getABITypeSize(PC->getType()));
} else if (const ConstantArray *CPA = dyn_cast<ConstantArray>(PC)) {
unsigned ElementSize =
TD->getABITypeSize(CPA->getType()->getElementType());
for (unsigned i = 0, e = CPA->getNumOperands(); i != e; ++i)
WorkList.push_back(CPair(CPA->getOperand(i), PA+i*ElementSize));
} else if (const ConstantStruct *CPS = dyn_cast<ConstantStruct>(PC)) {
const StructLayout *SL =
TD->getStructLayout(cast<StructType>(CPS->getType()));
for (unsigned i = 0, e = CPS->getNumOperands(); i != e; ++i)
WorkList.push_back(CPair(CPS->getOperand(i),
PA+SL->getElementOffset(i)));
} else {
cerr << "Bad Type: " << *PC->getType() << "\n";
assert(0 && "Unknown constant type to initialize memory with!");
}
}
}
MachOSym::MachOSym(const GlobalValue *gv, std::string name, uint8_t sect,
TargetMachine &TM) :
GV(gv), n_strx(0), n_type(sect == NO_SECT ? N_UNDF : N_SECT), n_sect(sect),
n_desc(0), n_value(0) {
const TargetAsmInfo *TAI = TM.getTargetAsmInfo();
switch (GV->getLinkage()) {
default:
assert(0 && "Unexpected linkage type!");
break;
case GlobalValue::WeakLinkage:
case GlobalValue::LinkOnceLinkage:
case GlobalValue::CommonLinkage:
assert(!isa<Function>(gv) && "Unexpected linkage type for Function!");
case GlobalValue::ExternalLinkage:
GVName = TAI->getGlobalPrefix() + name;
n_type |= GV->hasHiddenVisibility() ? N_PEXT : N_EXT;
break;
case GlobalValue::InternalLinkage:
GVName = TAI->getGlobalPrefix() + name;
break;
}
}
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