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"
27 //===----------------------------------------------------------------------===//
28 // ELFCodeEmitter Implementation
29 //===----------------------------------------------------------------------===//
33 /// startFunction - This callback is invoked when a new machine function is
34 /// about to be emitted.
35 void ELFCodeEmitter::startFunction(MachineFunction &MF) {
36 // Get the ELF Section that this function belongs in.
37 ES = &EW.getTextSection();
39 DOUT << "processing function: " << MF.getFunction()->getName() << "\n";
41 // FIXME: better memory management, this will be replaced by BinaryObjects
42 BinaryData &BD = ES->getData();
45 BufferEnd = BufferBegin + BD.capacity();
47 // Get the function alignment in bytes
48 unsigned Align = (1 << MF.getAlignment());
50 // Align the section size with the function alignment, so the function can
51 // start in a aligned offset, also update the section alignment if needed.
52 if (ES->Align < Align) ES->Align = Align;
53 ES->Size = (ES->Size + (Align-1)) & (-Align);
55 // Snaity check on allocated space for text section
56 assert( ES->Size < 4096 && "no more space in TextSection" );
58 // FIXME: Using ES->Size directly here instead of calculating it from the
59 // output buffer size (impossible because the code emitter deals only in raw
60 // bytes) forces us to manually synchronize size and write padding zero bytes
61 // to the output buffer for all non-text sections. For text sections, we do
62 // not synchonize the output buffer, and we just blow up if anyone tries to
63 // write non-code to it. An assert should probably be added to
64 // AddSymbolToSection to prevent calling it on the text section.
65 CurBufferPtr = BufferBegin + ES->Size;
67 // Record function start address relative to BufferBegin
68 FnStartPtr = CurBufferPtr;
71 /// finishFunction - This callback is invoked after the function is completely
73 bool ELFCodeEmitter::finishFunction(MachineFunction &MF) {
74 // Update Section Size
75 ES->Size = CurBufferPtr - BufferBegin;
77 // Add a symbol to represent the function.
78 const Function *F = MF.getFunction();
80 FnSym.setType(ELFSym::STT_FUNC);
81 FnSym.setBind(EW.getGlobalELFLinkage(F));
82 FnSym.setVisibility(EW.getGlobalELFVisibility(F));
83 FnSym.SectionIdx = ES->SectionIdx;
84 FnSym.Size = CurBufferPtr-FnStartPtr;
86 // Offset from start of Section
87 FnSym.Value = FnStartPtr-BufferBegin;
89 // Locals should go on the symbol list front
90 if (!F->hasPrivateLinkage()) {
91 if (FnSym.getBind() == ELFSym::STB_LOCAL)
92 EW.SymbolList.push_front(FnSym);
94 EW.SymbolList.push_back(FnSym);
97 // Emit constant pool to appropriate section(s)
98 emitConstantPool(MF.getConstantPool());
102 // If we have emitted any relocations to function-specific objects such as
103 // basic blocks, constant pools entries, or jump tables, record their
104 // addresses now so that we can rewrite them with the correct addresses
106 for (unsigned i = 0, e = Relocations.size(); i != e; ++i) {
107 MachineRelocation &MR = Relocations[i];
109 if (MR.isGlobalValue()) {
110 EW.PendingGlobals.insert(MR.getGlobalValue());
111 } else if (MR.isBasicBlock()) {
112 Addr = getMachineBasicBlockAddress(MR.getBasicBlock());
113 MR.setConstantVal(ES->SectionIdx);
114 MR.setResultPointer((void*)Addr);
115 } else if (MR.isConstantPoolIndex()) {
116 Addr = getConstantPoolEntryAddress(MR.getConstantPoolIndex());
117 MR.setConstantVal(CPSections[MR.getConstantPoolIndex()]);
118 MR.setResultPointer((void*)Addr);
120 assert(0 && "Unhandled relocation type");
122 ES->addRelocation(MR);
129 /// emitConstantPool - For each constant pool entry, figure out which section
130 /// the constant should live in and emit the constant
131 void ELFCodeEmitter::emitConstantPool(MachineConstantPool *MCP) {
132 const std::vector<MachineConstantPoolEntry> &CP = MCP->getConstants();
133 if (CP.empty()) return;
135 // TODO: handle PIC codegen
136 assert(TM.getRelocationModel() != Reloc::PIC_ &&
137 "PIC codegen not yet handled for elf constant pools!");
139 const TargetAsmInfo *TAI = TM.getTargetAsmInfo();
140 for (unsigned i = 0, e = CP.size(); i != e; ++i) {
141 MachineConstantPoolEntry CPE = CP[i];
143 // Get the right ELF Section for this constant pool entry
144 std::string CstPoolName =
145 TAI->SelectSectionForMachineConst(CPE.getType())->getName();
146 ELFSection &CstPoolSection =
147 EW.getConstantPoolSection(CstPoolName, CPE.getAlignment());
149 // Record the constant pool location and the section index
150 CPLocations.push_back(CstPoolSection.size());
151 CPSections.push_back(CstPoolSection.SectionIdx);
153 if (CPE.isMachineConstantPoolEntry())
154 assert("CPE.isMachineConstantPoolEntry not supported yet");
156 // Emit the constant to constant pool section
157 EW.EmitGlobalConstant(CPE.Val.ConstVal, CstPoolSection);
161 } // end namespace llvm