1 //===-- lib/CodeGen/ELFCodeEmitter.cpp ------------------------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 #define DEBUG_TYPE "elfce"
13 #include "ELFWriter.h"
14 #include "ELFCodeEmitter.h"
15 #include "llvm/Constants.h"
16 #include "llvm/DerivedTypes.h"
17 #include "llvm/Function.h"
18 #include "llvm/CodeGen/BinaryObject.h"
19 #include "llvm/CodeGen/MachineConstantPool.h"
20 #include "llvm/CodeGen/MachineJumpTableInfo.h"
21 #include "llvm/CodeGen/MachineRelocation.h"
22 #include "llvm/Target/TargetData.h"
23 #include "llvm/Target/TargetMachine.h"
24 #include "llvm/Target/TargetAsmInfo.h"
25 #include "llvm/Support/Debug.h"
26 #include "llvm/Support/ErrorHandling.h"
28 //===----------------------------------------------------------------------===//
29 // ELFCodeEmitter Implementation
30 //===----------------------------------------------------------------------===//
34 /// startFunction - This callback is invoked when a new machine function is
35 /// about to be emitted.
36 void ELFCodeEmitter::startFunction(MachineFunction &MF) {
37 DOUT << "processing function: " << MF.getFunction()->getName() << "\n";
39 // Get the ELF Section that this function belongs in.
40 ES = &EW.getTextSection();
42 // Set the desired binary object to be used by the code emitters
45 // Get the function alignment in bytes
46 unsigned Align = (1 << MF.getAlignment());
48 // The function must start on its required alignment
49 ES->emitAlignment(Align);
51 // Update the section alignment if needed.
52 if (ES->Align < Align) ES->Align = Align;
54 // Record the function start offset
55 FnStartOff = ES->getCurrentPCOffset();
58 /// finishFunction - This callback is invoked after the function is completely
60 bool ELFCodeEmitter::finishFunction(MachineFunction &MF) {
61 // Add a symbol to represent the function.
62 const Function *F = MF.getFunction();
64 FnSym.setType(ELFSym::STT_FUNC);
65 FnSym.setBind(EW.getGlobalELFBinding(F));
66 FnSym.setVisibility(EW.getGlobalELFVisibility(F));
67 FnSym.SectionIdx = ES->SectionIdx;
68 FnSym.Size = ES->getCurrentPCOffset()-FnStartOff;
70 // Offset from start of Section
71 FnSym.Value = FnStartOff;
73 // Locals should go on the symbol list front
74 if (!F->hasPrivateLinkage()) {
75 if (FnSym.getBind() == ELFSym::STB_LOCAL)
76 EW.SymbolList.push_front(FnSym);
78 EW.SymbolList.push_back(FnSym);
81 // Emit constant pool to appropriate section(s)
82 emitConstantPool(MF.getConstantPool());
84 // Emit jump tables to appropriate section
85 emitJumpTables(MF.getJumpTableInfo());
89 // If we have emitted any relocations to function-specific objects such as
90 // basic blocks, constant pools entries, or jump tables, record their
91 // addresses now so that we can rewrite them with the correct addresses
93 for (unsigned i = 0, e = Relocations.size(); i != e; ++i) {
94 MachineRelocation &MR = Relocations[i];
96 if (MR.isGlobalValue()) {
97 EW.PendingGlobals.insert(MR.getGlobalValue());
98 } else if (MR.isBasicBlock()) {
99 Addr = getMachineBasicBlockAddress(MR.getBasicBlock());
100 MR.setConstantVal(ES->SectionIdx);
101 MR.setResultPointer((void*)Addr);
102 } else if (MR.isConstantPoolIndex()) {
103 Addr = getConstantPoolEntryAddress(MR.getConstantPoolIndex());
104 MR.setConstantVal(CPSections[MR.getConstantPoolIndex()]);
105 MR.setResultPointer((void*)Addr);
106 } else if (MR.isJumpTableIndex()) {
107 Addr = getJumpTableEntryAddress(MR.getJumpTableIndex());
108 MR.setResultPointer((void*)Addr);
109 MR.setConstantVal(JumpTableSectionIdx);
111 LLVM_UNREACHABLE("Unhandled relocation type");
113 ES->addRelocation(MR);
116 // Clear per-function data structures.
121 MBBLocations.clear();
125 /// emitConstantPool - For each constant pool entry, figure out which section
126 /// the constant should live in and emit the constant
127 void ELFCodeEmitter::emitConstantPool(MachineConstantPool *MCP) {
128 const std::vector<MachineConstantPoolEntry> &CP = MCP->getConstants();
129 if (CP.empty()) return;
131 // TODO: handle PIC codegen
132 assert(TM.getRelocationModel() != Reloc::PIC_ &&
133 "PIC codegen not yet handled for elf constant pools!");
135 const TargetAsmInfo *TAI = TM.getTargetAsmInfo();
136 for (unsigned i = 0, e = CP.size(); i != e; ++i) {
137 MachineConstantPoolEntry CPE = CP[i];
139 // Get the right ELF Section for this constant pool entry
140 std::string CstPoolName =
141 TAI->SelectSectionForMachineConst(CPE.getType())->getName();
142 ELFSection &CstPoolSection =
143 EW.getConstantPoolSection(CstPoolName, CPE.getAlignment());
145 // Record the constant pool location and the section index
146 CPLocations.push_back(CstPoolSection.size());
147 CPSections.push_back(CstPoolSection.SectionIdx);
149 if (CPE.isMachineConstantPoolEntry())
150 assert("CPE.isMachineConstantPoolEntry not supported yet");
152 // Emit the constant to constant pool section
153 EW.EmitGlobalConstant(CPE.Val.ConstVal, CstPoolSection);
157 /// emitJumpTables - Emit all the jump tables for a given jump table info
158 /// record to the appropriate section.
159 void ELFCodeEmitter::emitJumpTables(MachineJumpTableInfo *MJTI) {
160 const std::vector<MachineJumpTableEntry> &JT = MJTI->getJumpTables();
161 if (JT.empty()) return;
163 // FIXME: handle PIC codegen
164 assert(TM.getRelocationModel() != Reloc::PIC_ &&
165 "PIC codegen not yet handled for elf jump tables!");
167 const TargetAsmInfo *TAI = TM.getTargetAsmInfo();
169 // Get the ELF Section to emit the jump table
170 unsigned Align = TM.getTargetData()->getPointerABIAlignment();
171 std::string JTName(TAI->getJumpTableDataSection());
172 ELFSection &JTSection = EW.getJumpTableSection(JTName, Align);
173 JumpTableSectionIdx = JTSection.SectionIdx;
175 // Entries in the JT Section are relocated against the text section
176 ELFSection &TextSection = EW.getTextSection();
178 // For each JT, record its offset from the start of the section
179 for (unsigned i = 0, e = JT.size(); i != e; ++i) {
180 const std::vector<MachineBasicBlock*> &MBBs = JT[i].MBBs;
182 DOUT << "JTSection.size(): " << JTSection.size() << "\n";
183 DOUT << "JTLocations.size: " << JTLocations.size() << "\n";
185 // Record JT 'i' offset in the JT section
186 JTLocations.push_back(JTSection.size());
188 // Each MBB entry in the Jump table section has a relocation entry
189 // against the current text section.
190 for (unsigned mi = 0, me = MBBs.size(); mi != me; ++mi) {
191 MachineRelocation MR =
192 MachineRelocation::getBB(JTSection.size(),
193 MachineRelocation::VANILLA,
196 // Offset of JT 'i' in JT section
197 MR.setResultPointer((void*)getMachineBasicBlockAddress(MBBs[mi]));
198 MR.setConstantVal(TextSection.SectionIdx);
200 // Add the relocation to the Jump Table section
201 JTSection.addRelocation(MR);
203 // Output placeholder for MBB in the JT section
204 JTSection.emitWord(0);
209 } // end namespace llvm