llvm-6502/lib/CodeGen/MachOCodeEmitter.cpp

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//===-- MachOEmitter.cpp - Target-independent Mach-O Emitter code --------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#include "MachOCodeEmitter.h"
#include "llvm/Constants.h"
#include "llvm/DerivedTypes.h"
#include "llvm/Function.h"
#include "llvm/CodeGen/MachineConstantPool.h"
#include "llvm/CodeGen/MachineJumpTableInfo.h"
#include "llvm/Target/TargetAsmInfo.h"
#include "llvm/Support/Mangler.h"
#include "llvm/Support/OutputBuffer.h"
//===----------------------------------------------------------------------===//
// MachOCodeEmitter Implementation
//===----------------------------------------------------------------------===//
namespace llvm {
/// startFunction - This callback is invoked when a new machine function is
/// about to be emitted.
void MachOCodeEmitter::startFunction(MachineFunction &MF) {
const TargetData *TD = TM.getTargetData();
const Function *F = MF.getFunction();
// Align the output buffer to the appropriate alignment, power of 2.
unsigned FnAlign = F->getAlignment();
unsigned TDAlign = TD->getPrefTypeAlignment(F->getType());
unsigned Align = Log2_32(std::max(FnAlign, TDAlign));
assert(!(Align & (Align-1)) && "Alignment is not a power of two!");
// Get the Mach-O Section that this function belongs in.
MachOSection *MOS = MOW.getTextSection();
// FIXME: better memory management
MOS->SectionData.reserve(4096);
BufferBegin = &MOS->SectionData[0];
BufferEnd = BufferBegin + MOS->SectionData.capacity();
// Upgrade the section alignment if required.
if (MOS->align < Align) MOS->align = Align;
// Round the size up to the correct alignment for starting the new function.
if ((MOS->size & ((1 << Align) - 1)) != 0) {
MOS->size += (1 << Align);
MOS->size &= ~((1 << Align) - 1);
}
// FIXME: Using MOS->size directly here instead of calculating it from the
// output buffer size (impossible because the code emitter deals only in raw
// bytes) forces us to manually synchronize size and write padding zero bytes
// to the output buffer for all non-text sections. For text sections, we do
// not synchonize the output buffer, and we just blow up if anyone tries to
// write non-code to it. An assert should probably be added to
// AddSymbolToSection to prevent calling it on the text section.
CurBufferPtr = BufferBegin + MOS->size;
}
/// finishFunction - This callback is invoked after the function is completely
/// finished.
bool MachOCodeEmitter::finishFunction(MachineFunction &MF) {
// Get the Mach-O Section that this function belongs in.
MachOSection *MOS = MOW.getTextSection();
// Get a symbol for the function to add to the symbol table
// FIXME: it seems like we should call something like AddSymbolToSection
// in startFunction rather than changing the section size and symbol n_value
// here.
const GlobalValue *FuncV = MF.getFunction();
MachOSym FnSym(FuncV, MOW.Mang->getValueName(FuncV), MOS->Index, TAI);
FnSym.n_value = MOS->size;
MOS->size = CurBufferPtr - BufferBegin;
// Emit constant pool to appropriate section(s)
emitConstantPool(MF.getConstantPool());
// Emit jump tables to appropriate section
emitJumpTables(MF.getJumpTableInfo());
// 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.isBasicBlock()) {
Addr = getMachineBasicBlockAddress(MR.getBasicBlock());
MR.setConstantVal(MOS->Index);
MR.setResultPointer((void*)Addr);
} else if (MR.isJumpTableIndex()) {
Addr = getJumpTableEntryAddress(MR.getJumpTableIndex());
MR.setConstantVal(MOW.getJumpTableSection()->Index);
MR.setResultPointer((void*)Addr);
} else if (MR.isConstantPoolIndex()) {
Addr = getConstantPoolEntryAddress(MR.getConstantPoolIndex());
MR.setConstantVal(CPSections[MR.getConstantPoolIndex()]);
MR.setResultPointer((void*)Addr);
} else if (MR.isGlobalValue()) {
// FIXME: This should be a set or something that uniques
MOW.PendingGlobals.push_back(MR.getGlobalValue());
} else {
assert(0 && "Unhandled relocation type");
}
MOS->Relocations.push_back(MR);
}
Relocations.clear();
// Finally, add it to the symtab.
MOW.SymbolTable.push_back(FnSym);
// Clear per-function data structures.
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, allocate space for it, and emit it to the
/// Section data buffer.
void MachOCodeEmitter::emitConstantPool(MachineConstantPool *MCP) {
const std::vector<MachineConstantPoolEntry> &CP = MCP->getConstants();
if (CP.empty()) return;
// FIXME: handle PIC codegen
assert(TM.getRelocationModel() != Reloc::PIC_ &&
"PIC codegen not yet handled for mach-o jump tables!");
// Although there is no strict necessity that I am aware of, we will do what
// gcc for OS X does and put each constant pool entry in a section of constant
// objects of a certain size. That means that float constants go in the
// literal4 section, and double objects go in literal8, etc.
//
// FIXME: revisit this decision if we ever do the "stick everything into one
// "giant object for PIC" optimization.
for (unsigned i = 0, e = CP.size(); i != e; ++i) {
const Type *Ty = CP[i].getType();
unsigned Size = TM.getTargetData()->getTypeAllocSize(Ty);
MachOSection *Sec = MOW.getConstSection(CP[i].Val.ConstVal);
OutputBuffer SecDataOut(Sec->SectionData, is64Bit, isLittleEndian);
CPLocations.push_back(Sec->SectionData.size());
CPSections.push_back(Sec->Index);
// FIXME: remove when we have unified size + output buffer
Sec->size += Size;
// Allocate space in the section for the global.
// FIXME: need alignment?
// FIXME: share between here and AddSymbolToSection?
for (unsigned j = 0; j < Size; ++j)
SecDataOut.outbyte(0);
MOW.InitMem(CP[i].Val.ConstVal, &Sec->SectionData[0], CPLocations[i],
TM.getTargetData(), Sec->Relocations);
}
}
/// emitJumpTables - Emit all the jump tables for a given jump table info
/// record to the appropriate section.
void MachOCodeEmitter::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 mach-o jump tables!");
MachOSection *Sec = MOW.getJumpTableSection();
unsigned TextSecIndex = MOW.getTextSection()->Index;
OutputBuffer SecDataOut(Sec->SectionData, is64Bit, isLittleEndian);
for (unsigned i = 0, e = JT.size(); i != e; ++i) {
// For each jump table, record its offset from the start of the section,
// reserve space for the relocations to the MBBs, and add the relocations.
const std::vector<MachineBasicBlock*> &MBBs = JT[i].MBBs;
JTLocations.push_back(Sec->SectionData.size());
for (unsigned mi = 0, me = MBBs.size(); mi != me; ++mi) {
MachineRelocation MR(MOW.GetJTRelocation(Sec->SectionData.size(),
MBBs[mi]));
MR.setResultPointer((void *)JTLocations[i]);
MR.setConstantVal(TextSecIndex);
Sec->Relocations.push_back(MR);
SecDataOut.outaddr(0);
}
}
// FIXME: remove when we have unified size + output buffer
Sec->size = Sec->SectionData.size();
}
} // end namespace llvm