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();
63 ELFSym *FnSym = new ELFSym(F);
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 if (!F->hasPrivateLinkage())
74 EW.SymbolList.push_back(FnSym);
76 // Emit constant pool to appropriate section(s)
77 emitConstantPool(MF.getConstantPool());
79 // Emit jump tables to appropriate section
80 emitJumpTables(MF.getJumpTableInfo());
84 // If we have emitted any relocations to function-specific objects such as
85 // basic blocks, constant pools entries, or jump tables, record their
86 // addresses now so that we can rewrite them with the correct addresses
88 for (unsigned i = 0, e = Relocations.size(); i != e; ++i) {
89 MachineRelocation &MR = Relocations[i];
91 if (MR.isGlobalValue()) {
92 EW.PendingGlobals.insert(MR.getGlobalValue());
93 } else if (MR.isBasicBlock()) {
94 Addr = getMachineBasicBlockAddress(MR.getBasicBlock());
95 MR.setConstantVal(ES->SectionIdx);
96 MR.setResultPointer((void*)Addr);
97 } else if (MR.isConstantPoolIndex()) {
98 Addr = getConstantPoolEntryAddress(MR.getConstantPoolIndex());
99 MR.setConstantVal(CPSections[MR.getConstantPoolIndex()]);
100 MR.setResultPointer((void*)Addr);
101 } else if (MR.isJumpTableIndex()) {
102 Addr = getJumpTableEntryAddress(MR.getJumpTableIndex());
103 MR.setResultPointer((void*)Addr);
104 MR.setConstantVal(JumpTableSectionIdx);
106 llvm_unreachable("Unhandled relocation type");
108 ES->addRelocation(MR);
111 // Clear per-function data structures.
116 MBBLocations.clear();
120 /// emitConstantPool - For each constant pool entry, figure out which section
121 /// the constant should live in and emit the constant
122 void ELFCodeEmitter::emitConstantPool(MachineConstantPool *MCP) {
123 const std::vector<MachineConstantPoolEntry> &CP = MCP->getConstants();
124 if (CP.empty()) return;
126 // TODO: handle PIC codegen
127 assert(TM.getRelocationModel() != Reloc::PIC_ &&
128 "PIC codegen not yet handled for elf constant pools!");
130 const TargetAsmInfo *TAI = TM.getTargetAsmInfo();
131 for (unsigned i = 0, e = CP.size(); i != e; ++i) {
132 MachineConstantPoolEntry CPE = CP[i];
134 // Get the right ELF Section for this constant pool entry
135 std::string CstPoolName =
136 TAI->SelectSectionForMachineConst(CPE.getType())->getName();
137 ELFSection &CstPoolSection =
138 EW.getConstantPoolSection(CstPoolName, CPE.getAlignment());
140 // Record the constant pool location and the section index
141 CPLocations.push_back(CstPoolSection.size());
142 CPSections.push_back(CstPoolSection.SectionIdx);
144 if (CPE.isMachineConstantPoolEntry())
145 assert("CPE.isMachineConstantPoolEntry not supported yet");
147 // Emit the constant to constant pool section
148 EW.EmitGlobalConstant(CPE.Val.ConstVal, CstPoolSection);
152 /// emitJumpTables - Emit all the jump tables for a given jump table info
153 /// record to the appropriate section.
154 void ELFCodeEmitter::emitJumpTables(MachineJumpTableInfo *MJTI) {
155 const std::vector<MachineJumpTableEntry> &JT = MJTI->getJumpTables();
156 if (JT.empty()) return;
158 // FIXME: handle PIC codegen
159 assert(TM.getRelocationModel() != Reloc::PIC_ &&
160 "PIC codegen not yet handled for elf jump tables!");
162 const TargetAsmInfo *TAI = TM.getTargetAsmInfo();
164 // Get the ELF Section to emit the jump table
165 unsigned Align = TM.getTargetData()->getPointerABIAlignment();
166 std::string JTName(TAI->getJumpTableDataSection());
167 ELFSection &JTSection = EW.getJumpTableSection(JTName, Align);
168 JumpTableSectionIdx = JTSection.SectionIdx;
170 // Entries in the JT Section are relocated against the text section
171 ELFSection &TextSection = EW.getTextSection();
173 // For each JT, record its offset from the start of the section
174 for (unsigned i = 0, e = JT.size(); i != e; ++i) {
175 const std::vector<MachineBasicBlock*> &MBBs = JT[i].MBBs;
177 DOUT << "JTSection.size(): " << JTSection.size() << "\n";
178 DOUT << "JTLocations.size: " << JTLocations.size() << "\n";
180 // Record JT 'i' offset in the JT section
181 JTLocations.push_back(JTSection.size());
183 // Each MBB entry in the Jump table section has a relocation entry
184 // against the current text section.
185 for (unsigned mi = 0, me = MBBs.size(); mi != me; ++mi) {
186 MachineRelocation MR =
187 MachineRelocation::getBB(JTSection.size(),
188 MachineRelocation::VANILLA,
191 // Offset of JT 'i' in JT section
192 MR.setResultPointer((void*)getMachineBasicBlockAddress(MBBs[mi]));
193 MR.setConstantVal(TextSection.SectionIdx);
195 // Add the relocation to the Jump Table section
196 JTSection.addRelocation(MR);
198 // Output placeholder for MBB in the JT section
199 JTSection.emitWord(0);
204 } // end namespace llvm