Initial checkin of the Mach-O emitter. There's plenty of fixmes, but it

does emit linkable .o files in very simple cases.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@29850 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 428 insertions, 0 deletions

diff --git a/lib/CodeGen/MachOWriter.cpp b/lib/CodeGen/MachOWriter.cpp
new file mode 100644
index 0000000000..e3228cb5c7
--- /dev/null
+++ b/lib/CodeGen/MachOWriter.cpp
@@ -0,0 +1,428 @@
+//===-- MachOWriter.cpp - Target-independent Mach-O Writer code -----------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file was developed by Nate Begeman and 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 "llvm/Module.h"
+#include "llvm/CodeGen/MachineCodeEmitter.h"
+#include "llvm/CodeGen/MachineConstantPool.h"
+#include "llvm/CodeGen/MachineRelocation.h"
+#include "llvm/CodeGen/MachOWriter.h"
+#include "llvm/Target/TargetData.h"
+#include "llvm/Target/TargetJITInfo.h"
+#include "llvm/Target/TargetMachine.h"
+#include "llvm/Support/Mangler.h"
+#include <iostream>
+using namespace llvm;
+
+//===----------------------------------------------------------------------===//
+//                       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;
+    
+    /// MOS - The current section we're writing to
+    MachOWriter::MachOSection *MOS;
+
+    /// Relocations - These are the relocations that the function needs, as
+    /// emitted.
+    std::vector<MachineRelocation> Relocations;
+
+    /// 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) {}
+
+    void startFunction(MachineFunction &F);
+    bool finishFunction(MachineFunction &F);
+
+    void addRelocation(const MachineRelocation &MR) {
+      Relocations.push_back(MR);
+    }
+    
+    virtual void StartMachineBasicBlock(MachineBasicBlock *MBB) {
+      if (MBBLocations.size() <= (unsigned)MBB->getNumber())
+        MBBLocations.resize((MBB->getNumber()+1)*2);
+      MBBLocations[MBB->getNumber()] = getCurrentPCValue();
+    }
+
+    virtual intptr_t getConstantPoolEntryAddress(unsigned Index) const {
+      assert(0 && "CP not implementated yet!");
+      return 0;
+    }
+    virtual intptr_t getJumpTableEntryAddress(unsigned Index) const {
+      assert(0 && "JT not implementated yet!");
+      return 0;
+    }
+
+    virtual intptr_t getMachineBasicBlockAddress(MachineBasicBlock *MBB) const {
+      assert(MBBLocations.size() > (unsigned)MBB->getNumber() && 
+             MBBLocations[MBB->getNumber()] && "MBB not emitted!");
+      return MBBLocations[MBB->getNumber()];
+    }
+
+    /// JIT SPECIFIC FUNCTIONS - DO NOT IMPLEMENT THESE HERE!
+    void startFunctionStub(unsigned StubSize) {
+      assert(0 && "JIT specific function called!");
+      abort();
+    }
+    void *finishFunctionStub(const Function *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 &F) {
+  // Align the output buffer to the appropriate alignment, power of 2.
+  // FIXME: GENERICIZE!!
+  unsigned Align = 4;
+
+  // Get the Mach-O Section that this function belongs in.
+  MOS = &MOW.getTextSection();
+  
+   // FIXME: better memory management
+  MOS->SectionData.reserve(4096);
+  BufferBegin = &(MOS->SectionData[0]);
+  BufferEnd = BufferBegin + MOS->SectionData.capacity();
+  CurBufferPtr = BufferBegin + MOS->size;
+
+  // Upgrade the section alignment if required.
+  if (MOS->align < Align) MOS->align = Align;
+
+  // Make sure we only relocate to this function's MBBs.
+  MBBLocations.clear();
+}
+
+/// finishFunction - This callback is invoked after the function is completely
+/// finished.
+bool MachOCodeEmitter::finishFunction(MachineFunction &F) {
+  MOS->size += CurBufferPtr - BufferBegin;
+  
+  // Get a symbol for the function to add to the symbol table
+  MachOWriter::MachOSym FnSym(F.getFunction(), MOS->Index);
+  
+  // Figure out the binding (linkage) of the symbol.
+  switch (F.getFunction()->getLinkage()) {
+  default:
+    // appending linkage is illegal for functions.
+    assert(0 && "Unknown linkage type!");
+  case GlobalValue::ExternalLinkage:
+    FnSym.n_type = MachOWriter::MachOSym::N_SECT | MachOWriter::MachOSym::N_EXT;
+    break;
+  case GlobalValue::InternalLinkage:
+    FnSym.n_type = MachOWriter::MachOSym::N_SECT;
+    break;
+  }
+  
+  // Resolve the function's relocations either to concrete pointers in the case
+  // of branches from one block to another, or to target relocation entries.
+  for (unsigned i = 0, e = Relocations.size(); i != e; ++i) {
+    MachineRelocation &MR = Relocations[i];
+    if (MR.isBasicBlock()) {
+      void *MBBAddr = (void *)getMachineBasicBlockAddress(MR.getBasicBlock());
+      MR.setResultPointer(MBBAddr);
+      MOW.TM.getJITInfo()->relocate(BufferBegin, &MR, 1, 0);
+      // FIXME: we basically want the JITInfo relocate() function to rewrite
+      //        this guy right now, so we just write the correct displacement
+      //        to the file.
+    } else {
+      // isString | isGV | isCPI | isJTI
+      // FIXME: do something smart here.  We won't be able to relocate these
+      //        until the sections are all layed out, but we still need to
+      //        record them.  Maybe emit TargetRelocations and then resolve
+      //        those at file writing time?
+      std::cerr << "whee!\n";
+    }
+  }
+  Relocations.clear();
+  
+  // Finally, add it to the symtab.
+  MOW.SymbolTable.push_back(FnSym);
+  return false;
+}
+
+//===----------------------------------------------------------------------===//
+//                          MachOWriter Implementation
+//===----------------------------------------------------------------------===//
+
+MachOWriter::MachOWriter(std::ostream &o, TargetMachine &tm) : O(o), TM(tm) {
+  // FIXME: set cpu type and cpu subtype somehow from 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::EmitGlobal(GlobalVariable *GV) {
+  // FIXME: do something smart here.
+}
+
+
+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) {
+  // 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 text and data sections.
+  EmitSections();
+
+  // Emit the relocation entry data for each section.
+  // FIXME: presumably this should be a virtual method, since different targets
+  //        have different relocation types.
+  EmitRelocations();
+
+  // Emit the symbol table.
+  // FIXME: we don't handle debug info yet, we should probably do that.
+  EmitSymbolTable();
+
+  // Emit the string table for the sections we have.
+  EmitStringTable();
+
+  // 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.begin()->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;
+  outword(FH, Header.magic);
+  outword(FH, Header.cputype);
+  outword(FH, Header.cpusubtype);
+  outword(FH, Header.filetype);
+  outword(FH, Header.ncmds);
+  outword(FH, Header.sizeofcmds);
+  outword(FH, Header.flags);
+  if (is64Bit)
+    outword(FH, Header.reserved);
+  
+  // Step #4: Finish filling in the segment load command and write it out
+  for (std::list<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;
+  
+  outword(FH, SEG.cmd);
+  outword(FH, SEG.cmdsize);
+  outstring(FH, SEG.segname, 16);
+  outaddr(FH, SEG.vmaddr);
+  outaddr(FH, SEG.vmsize);
+  outaddr(FH, SEG.fileoff);
+  outaddr(FH, SEG.filesize);
+  outword(FH, SEG.maxprot);
+  outword(FH, SEG.initprot);
+  outword(FH, SEG.nsects);
+  outword(FH, SEG.flags);
+  
+  // Step #5: Write out the section commands for each section
+  for (std::list<MachOSection>::iterator I = SectionList.begin(),
+         E = SectionList.end(); I != E; ++I) {
+    I->offset = SEG.fileoff;  // FIXME: separate offset
+    outstring(FH, I->sectname, 16);
+    outstring(FH, I->segname, 16);
+    outaddr(FH, I->addr);
+    outaddr(FH, I->size);
+    outword(FH, I->offset);
+    outword(FH, I->align);
+    outword(FH, I->reloff);
+    outword(FH, I->nreloc);
+    outword(FH, I->flags);
+    outword(FH, I->reserved1);
+    outword(FH, I->reserved2);
+    if (is64Bit)
+      outword(FH, I->reserved3);
+  }
+  
+  // Step #6: Emit LC_SYMTAB/LC_DYSYMTAB load commands
+  // FIXME: We'll need to scan over the symbol table and possibly do the sort
+  // here so that we can set the proper indices in the dysymtab load command for
+  // the index and number of external symbols defined in this module.
+  // FIXME: We'll also need to scan over all the symbols so that we can 
+  // calculate the size of the string table.
+  // FIXME: add size of relocs
+  SymTab.symoff  = SEG.fileoff + SEG.filesize;
+  SymTab.nsyms   = SymbolTable.size();
+  SymTab.stroff  = SymTab.symoff + SymTab.nsyms * MachOSym::entrySize();
+  SymTab.strsize = 10;
+  outword(FH, SymTab.cmd);
+  outword(FH, SymTab.cmdsize);
+  outword(FH, SymTab.symoff);
+  outword(FH, SymTab.nsyms);
+  outword(FH, SymTab.stroff);
+  outword(FH, SymTab.strsize);
+
+  // FIXME: set DySymTab fields appropriately
+  outword(FH, DySymTab.cmd);
+  outword(FH, DySymTab.cmdsize);
+  outword(FH, DySymTab.ilocalsym);
+  outword(FH, DySymTab.nlocalsym);
+  outword(FH, DySymTab.iextdefsym);
+  outword(FH, DySymTab.nextdefsym);
+  outword(FH, DySymTab.iundefsym);
+  outword(FH, DySymTab.nundefsym);
+  outword(FH, DySymTab.tocoff);
+  outword(FH, DySymTab.ntoc);
+  outword(FH, DySymTab.modtaboff);
+  outword(FH, DySymTab.nmodtab);
+  outword(FH, DySymTab.extrefsymoff);
+  outword(FH, DySymTab.nextrefsyms);
+  outword(FH, DySymTab.indirectsymoff);
+  outword(FH, DySymTab.nindirectsyms);
+  outword(FH, DySymTab.extreloff);
+  outword(FH, DySymTab.nextrel);
+  outword(FH, DySymTab.locreloff);
+  outword(FH, 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::list<MachOSection>::iterator I = SectionList.begin(),
+         E = SectionList.end(); I != E; ++I) {
+    O.write((char*)&I->SectionData[0], I->size);
+  }
+}
+
+void MachOWriter::EmitRelocations() {
+  // FIXME: this should probably be a pure virtual function, since the
+  // relocation types and layout of the relocations themselves are target
+  // specific.
+}
+
+/// EmitSymbolTable - 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::EmitSymbolTable() {
+  // The order of the symbol table is:
+  // local symbols
+  // defined external symbols (sorted by name)
+  // undefined external symbols (sorted by name)
+  DataBuffer ST;
+  
+  // FIXME: enforce the above ordering, presumably by sorting by name, 
+  // then partitioning twice.
+  unsigned stringIndex;
+  for (std::vector<MachOSym>::iterator I = SymbolTable.begin(),
+         E = SymbolTable.end(); I != E; ++I) {
+    // FIXME: remove when we actually calculate these correctly
+    I->n_strx = 1;
+    StringTable.push_back(Mang->getValueName(I->GV));
+    // Emit nlist to buffer
+    outword(ST, I->n_strx);
+    outbyte(ST, I->n_type);
+    outbyte(ST, I->n_sect);
+    outhalf(ST, I->n_desc);
+    outaddr(ST, I->n_value);
+  }
+  
+  O.write((char*)&ST[0], ST.size());
+}
+
+/// EmitStringTable - This method adds and emits a section for the Mach-O 
+/// string table.
+void MachOWriter::EmitStringTable() {
+  // The order of the string table is:
+  // strings for external symbols
+  // strings for local symbols
+  // This is the symbol table, but backwards.  This allows us to avoid a sorting
+  // the symbol table again; all we have to do is use a reverse iterator.
+  DataBuffer ST;
+
+  // Write out a leading zero byte when emitting string table, for n_strx == 0
+  // which means an empty string.
+  outbyte(ST, 0);
+
+  for (std::vector<std::string>::iterator I = StringTable.begin(),
+         E = StringTable.end(); I != E; ++I) {
+    // FIXME: do not arbitrarily cap symbols to 16 characters
+    // FIXME: do something more efficient than outstring
+    outstring(ST, *I, 16);
+  }
+  O.write((char*)&ST[0], ST.size());
+}