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/MachineFunction.h"
21
#include "llvm/CodeGen/MachineJumpTableInfo.h"
22
#include "llvm/CodeGen/MachineRelocation.h"
23
#include "llvm/Target/TargetData.h"
24
#include "llvm/Target/TargetELFWriterInfo.h"
25
#include "llvm/Target/TargetMachine.h"
26
#include "llvm/MC/MCAsmInfo.h"
27
#include "llvm/Support/Debug.h"
28
#include "llvm/Support/ErrorHandling.h"
29
#include "llvm/Support/raw_ostream.h"
31
//===----------------------------------------------------------------------===//
32
// ELFCodeEmitter Implementation
33
//===----------------------------------------------------------------------===//
37
/// startFunction - This callback is invoked when a new machine function is
38
/// about to be emitted.
39
void ELFCodeEmitter::startFunction(MachineFunction &MF) {
40
DEBUG(dbgs() << "processing function: "
41
<< MF.getFunction()->getName() << "\n");
43
// Get the ELF Section that this function belongs in.
44
ES = &EW.getTextSection(MF.getFunction());
46
// Set the desired binary object to be used by the code emitters
49
// Get the function alignment in bytes
50
unsigned Align = (1 << MF.getAlignment());
52
// The function must start on its required alignment
53
ES->emitAlignment(Align);
55
// Update the section alignment if needed.
56
ES->Align = std::max(ES->Align, Align);
58
// Record the function start offset
59
FnStartOff = ES->getCurrentPCOffset();
61
// Emit constant pool and jump tables to their appropriate sections.
62
// They need to be emitted before the function because in some targets
63
// the later may reference JT or CP entry address.
64
emitConstantPool(MF.getConstantPool());
65
if (MF.getJumpTableInfo())
66
emitJumpTables(MF.getJumpTableInfo());
69
/// finishFunction - This callback is invoked after the function is completely
71
bool ELFCodeEmitter::finishFunction(MachineFunction &MF) {
72
// Add a symbol to represent the function.
73
const Function *F = MF.getFunction();
74
ELFSym *FnSym = ELFSym::getGV(F, EW.getGlobalELFBinding(F), ELFSym::STT_FUNC,
75
EW.getGlobalELFVisibility(F));
76
FnSym->SectionIdx = ES->SectionIdx;
77
FnSym->Size = ES->getCurrentPCOffset()-FnStartOff;
78
EW.AddPendingGlobalSymbol(F, true);
80
// Offset from start of Section
81
FnSym->Value = FnStartOff;
83
if (!F->hasPrivateLinkage())
84
EW.SymbolList.push_back(FnSym);
86
// Patch up Jump Table Section relocations to use the real MBBs offsets
87
// now that the MBB label offsets inside the function are known.
88
if (MF.getJumpTableInfo()) {
89
ELFSection &JTSection = EW.getJumpTableSection();
90
for (std::vector<MachineRelocation>::iterator MRI = JTRelocations.begin(),
91
MRE = JTRelocations.end(); MRI != MRE; ++MRI) {
92
MachineRelocation &MR = *MRI;
93
unsigned MBBOffset = getMachineBasicBlockAddress(MR.getBasicBlock());
94
MR.setResultPointer((void*)MBBOffset);
95
MR.setConstantVal(ES->SectionIdx);
96
JTSection.addRelocation(MR);
100
// If we have emitted any relocations to function-specific objects such as
101
// basic blocks, constant pools entries, or jump tables, record their
102
// addresses now so that we can rewrite them with the correct addresses later
103
for (unsigned i = 0, e = Relocations.size(); i != e; ++i) {
104
MachineRelocation &MR = Relocations[i];
106
if (MR.isGlobalValue()) {
107
EW.AddPendingGlobalSymbol(MR.getGlobalValue());
108
} else if (MR.isExternalSymbol()) {
109
EW.AddPendingExternalSymbol(MR.getExternalSymbol());
110
} else if (MR.isBasicBlock()) {
111
Addr = getMachineBasicBlockAddress(MR.getBasicBlock());
112
MR.setConstantVal(ES->SectionIdx);
113
MR.setResultPointer((void*)Addr);
114
} else if (MR.isConstantPoolIndex()) {
115
Addr = getConstantPoolEntryAddress(MR.getConstantPoolIndex());
116
MR.setConstantVal(CPSections[MR.getConstantPoolIndex()]);
117
MR.setResultPointer((void*)Addr);
118
} else if (MR.isJumpTableIndex()) {
119
ELFSection &JTSection = EW.getJumpTableSection();
120
Addr = getJumpTableEntryAddress(MR.getJumpTableIndex());
121
MR.setConstantVal(JTSection.SectionIdx);
122
MR.setResultPointer((void*)Addr);
124
llvm_unreachable("Unhandled relocation type");
126
ES->addRelocation(MR);
129
// Clear per-function data structures.
130
JTRelocations.clear();
135
MBBLocations.clear();
139
/// emitConstantPool - For each constant pool entry, figure out which section
140
/// the constant should live in and emit the constant
141
void ELFCodeEmitter::emitConstantPool(MachineConstantPool *MCP) {
142
const std::vector<MachineConstantPoolEntry> &CP = MCP->getConstants();
143
if (CP.empty()) return;
145
// TODO: handle PIC codegen
146
assert(TM.getRelocationModel() != Reloc::PIC_ &&
147
"PIC codegen not yet handled for elf constant pools!");
149
for (unsigned i = 0, e = CP.size(); i != e; ++i) {
150
MachineConstantPoolEntry CPE = CP[i];
152
// Record the constant pool location and the section index
153
ELFSection &CstPool = EW.getConstantPoolSection(CPE);
154
CPLocations.push_back(CstPool.size());
155
CPSections.push_back(CstPool.SectionIdx);
157
if (CPE.isMachineConstantPoolEntry())
158
assert("CPE.isMachineConstantPoolEntry not supported yet");
160
// Emit the constant to constant pool section
161
EW.EmitGlobalConstant(CPE.Val.ConstVal, CstPool);
165
/// emitJumpTables - Emit all the jump tables for a given jump table info
166
/// record to the appropriate section.
167
void ELFCodeEmitter::emitJumpTables(MachineJumpTableInfo *MJTI) {
168
const std::vector<MachineJumpTableEntry> &JT = MJTI->getJumpTables();
169
if (JT.empty()) return;
171
// FIXME: handle PIC codegen
172
assert(TM.getRelocationModel() != Reloc::PIC_ &&
173
"PIC codegen not yet handled for elf jump tables!");
175
const TargetELFWriterInfo *TEW = TM.getELFWriterInfo();
176
unsigned EntrySize = 4; //MJTI->getEntrySize();
178
// Get the ELF Section to emit the jump table
179
ELFSection &JTSection = EW.getJumpTableSection();
181
// For each JT, record its offset from the start of the section
182
for (unsigned i = 0, e = JT.size(); i != e; ++i) {
183
const std::vector<MachineBasicBlock*> &MBBs = JT[i].MBBs;
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
unsigned MachineRelTy = TEW->getAbsoluteLabelMachineRelTy();
192
MachineRelocation MR =
193
MachineRelocation::getBB(JTSection.size(), MachineRelTy, MBBs[mi]);
195
// Add the relocation to the Jump Table section
196
JTRelocations.push_back(MR);
198
// Output placeholder for MBB in the JT section
199
for (unsigned s=0; s < EntrySize; ++s)
200
JTSection.emitByte(0);
205
} // end namespace llvm