//===-- lib/CodeGen/ELFCodeEmitter.cpp ------------------------------------===// // // The LLVM Compiler Infrastructure // // This file is distributed under the University of Illinois Open Source // License. See LICENSE.TXT for details. // //===----------------------------------------------------------------------===// #define DEBUG_TYPE "elfce" #include "ELF.h" #include "ELFWriter.h" #include "ELFCodeEmitter.h" #include "llvm/Constants.h" #include "llvm/DerivedTypes.h" #include "llvm/Function.h" #include "llvm/CodeGen/BinaryObject.h" #include "llvm/CodeGen/MachineConstantPool.h" #include "llvm/CodeGen/MachineFunction.h" #include "llvm/CodeGen/MachineJumpTableInfo.h" #include "llvm/CodeGen/MachineRelocation.h" #include "llvm/Target/TargetData.h" #include "llvm/Target/TargetELFWriterInfo.h" #include "llvm/Target/TargetMachine.h" #include "llvm/MC/MCAsmInfo.h" #include "llvm/Support/Debug.h" #include "llvm/Support/ErrorHandling.h" #include "llvm/Support/raw_ostream.h" //===----------------------------------------------------------------------===// // ELFCodeEmitter Implementation //===----------------------------------------------------------------------===// namespace llvm { /// startFunction - This callback is invoked when a new machine function is /// about to be emitted. void ELFCodeEmitter::startFunction(MachineFunction &MF) { DEBUG(dbgs() << "processing function: " << MF.getFunction()->getName() << "\n"); // Get the ELF Section that this function belongs in. ES = &EW.getTextSection(MF.getFunction()); // Set the desired binary object to be used by the code emitters setBinaryObject(ES); // Get the function alignment in bytes unsigned Align = (1 << MF.getAlignment()); // The function must start on its required alignment ES->emitAlignment(Align); // Update the section alignment if needed. ES->Align = std::max(ES->Align, Align); // Record the function start offset FnStartOff = ES->getCurrentPCOffset(); // Emit constant pool and jump tables to their appropriate sections. // They need to be emitted before the function because in some targets // the later may reference JT or CP entry address. emitConstantPool(MF.getConstantPool()); if (MF.getJumpTableInfo()) emitJumpTables(MF.getJumpTableInfo()); } /// finishFunction - This callback is invoked after the function is completely /// finished. bool ELFCodeEmitter::finishFunction(MachineFunction &MF) { // Add a symbol to represent the function. const Function *F = MF.getFunction(); ELFSym *FnSym = ELFSym::getGV(F, EW.getGlobalELFBinding(F), ELF::STT_FUNC, EW.getGlobalELFVisibility(F)); FnSym->SectionIdx = ES->SectionIdx; FnSym->Size = ES->getCurrentPCOffset()-FnStartOff; EW.AddPendingGlobalSymbol(F, true); // Offset from start of Section FnSym->Value = FnStartOff; if (!F->hasPrivateLinkage()) EW.SymbolList.push_back(FnSym); // Patch up Jump Table Section relocations to use the real MBBs offsets // now that the MBB label offsets inside the function are known. if (MF.getJumpTableInfo()) { ELFSection &JTSection = EW.getJumpTableSection(); for (std::vector<MachineRelocation>::iterator MRI = JTRelocations.begin(), MRE = JTRelocations.end(); MRI != MRE; ++MRI) { MachineRelocation &MR = *MRI; uintptr_t MBBOffset = getMachineBasicBlockAddress(MR.getBasicBlock()); MR.setResultPointer((void*)MBBOffset); MR.setConstantVal(ES->SectionIdx); JTSection.addRelocation(MR); } } // 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.isGlobalValue()) { EW.AddPendingGlobalSymbol(MR.getGlobalValue()); } else if (MR.isExternalSymbol()) { EW.AddPendingExternalSymbol(MR.getExternalSymbol()); } else if (MR.isBasicBlock()) { Addr = getMachineBasicBlockAddress(MR.getBasicBlock()); MR.setConstantVal(ES->SectionIdx); MR.setResultPointer((void*)Addr); } else if (MR.isConstantPoolIndex()) { Addr = getConstantPoolEntryAddress(MR.getConstantPoolIndex()); MR.setConstantVal(CPSections[MR.getConstantPoolIndex()]); MR.setResultPointer((void*)Addr); } else if (MR.isJumpTableIndex()) { ELFSection &JTSection = EW.getJumpTableSection(); Addr = getJumpTableEntryAddress(MR.getJumpTableIndex()); MR.setConstantVal(JTSection.SectionIdx); MR.setResultPointer((void*)Addr); } else { llvm_unreachable("Unhandled relocation type"); } ES->addRelocation(MR); } // Clear per-function data structures. JTRelocations.clear(); Relocations.clear(); CPLocations.clear(); CPSections.clear(); JTLocations.clear(); MBBLocations.clear(); return false; } /// emitConstantPool - For each constant pool entry, figure out which section /// the constant should live in and emit the constant void ELFCodeEmitter::emitConstantPool(MachineConstantPool *MCP) { const std::vector<MachineConstantPoolEntry> &CP = MCP->getConstants(); if (CP.empty()) return; // TODO: handle PIC codegen assert(TM.getRelocationModel() != Reloc::PIC_ && "PIC codegen not yet handled for elf constant pools!"); for (unsigned i = 0, e = CP.size(); i != e; ++i) { MachineConstantPoolEntry CPE = CP[i]; // Record the constant pool location and the section index ELFSection &CstPool = EW.getConstantPoolSection(CPE); CPLocations.push_back(CstPool.size()); CPSections.push_back(CstPool.SectionIdx); if (CPE.isMachineConstantPoolEntry()) assert("CPE.isMachineConstantPoolEntry not supported yet"); // Emit the constant to constant pool section EW.EmitGlobalConstant(CPE.Val.ConstVal, CstPool); } } /// emitJumpTables - Emit all the jump tables for a given jump table info /// record to the appropriate section. void ELFCodeEmitter::emitJumpTables(MachineJumpTableInfo *MJTI) { const std::vector<MachineJumpTableEntry> &JT = MJTI->getJumpTables(); if (JT.empty()) return; // FIXME: handle PIC codegen assert(TM.getRelocationModel() != Reloc::PIC_ && "PIC codegen not yet handled for elf jump tables!"); const TargetELFWriterInfo *TEW = TM.getELFWriterInfo(); unsigned EntrySize = 4; //MJTI->getEntrySize(); // Get the ELF Section to emit the jump table ELFSection &JTSection = EW.getJumpTableSection(); // For each JT, record its offset from the start of the section for (unsigned i = 0, e = JT.size(); i != e; ++i) { const std::vector<MachineBasicBlock*> &MBBs = JT[i].MBBs; // Record JT 'i' offset in the JT section JTLocations.push_back(JTSection.size()); // Each MBB entry in the Jump table section has a relocation entry // against the current text section. for (unsigned mi = 0, me = MBBs.size(); mi != me; ++mi) { unsigned MachineRelTy = TEW->getAbsoluteLabelMachineRelTy(); MachineRelocation MR = MachineRelocation::getBB(JTSection.size(), MachineRelTy, MBBs[mi]); // Add the relocation to the Jump Table section JTRelocations.push_back(MR); // Output placeholder for MBB in the JT section for (unsigned s=0; s < EntrySize; ++s) JTSection.emitByte(0); } } } } // end namespace llvm