llvm-project/llvm/lib/MC/MCPureStreamer.cpp

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//===- lib/MC/MCPureStreamer.cpp - MC "Pure" Object Output ----------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#include "llvm/MC/MCStreamer.h"
#include "llvm/MC/MCAssembler.h"
#include "llvm/MC/MCCodeEmitter.h"
#include "llvm/MC/MCContext.h"
#include "llvm/MC/MCExpr.h"
#include "llvm/MC/MCObjectStreamer.h"
// FIXME: Remove this.
#include "llvm/MC/MCSectionMachO.h"
#include "llvm/MC/MCSymbol.h"
#include "llvm/Support/ErrorHandling.h"
using namespace llvm;
namespace {
class MCPureStreamer : public MCObjectStreamer {
private:
virtual void EmitInstToFragment(const MCInst &Inst);
virtual void EmitInstToData(const MCInst &Inst);
public:
MCPureStreamer(MCContext &Context, MCAsmBackend &TAB,
raw_ostream &OS, MCCodeEmitter *Emitter)
: MCObjectStreamer(Context, TAB, OS, Emitter) {}
/// @name MCStreamer Interface
/// @{
virtual void InitSections();
virtual void EmitLabel(MCSymbol *Symbol);
virtual void EmitDebugLabel(MCSymbol *Symbol);
virtual void EmitZerofill(const MCSection *Section, MCSymbol *Symbol = 0,
uint64_t Size = 0, unsigned ByteAlignment = 0);
virtual void EmitBytes(StringRef Data, unsigned AddrSpace);
virtual void EmitValueToAlignment(unsigned ByteAlignment, int64_t Value = 0,
unsigned ValueSize = 1,
unsigned MaxBytesToEmit = 0);
virtual void EmitCodeAlignment(unsigned ByteAlignment,
unsigned MaxBytesToEmit = 0);
virtual bool EmitValueToOffset(const MCExpr *Offset,
unsigned char Value = 0);
virtual void FinishImpl();
virtual void EmitSymbolAttribute(MCSymbol *Symbol, MCSymbolAttr Attribute) {
report_fatal_error("unsupported directive in pure streamer");
}
virtual void EmitAssemblerFlag(MCAssemblerFlag Flag) {
report_fatal_error("unsupported directive in pure streamer");
}
virtual void EmitTBSSSymbol(const MCSection *Section, MCSymbol *Symbol,
uint64_t Size, unsigned ByteAlignment = 0) {
report_fatal_error("unsupported directive in pure streamer");
}
virtual void EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) {
report_fatal_error("unsupported directive in pure streamer");
}
virtual void EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
unsigned ByteAlignment) {
report_fatal_error("unsupported directive in pure streamer");
}
virtual void EmitThumbFunc(MCSymbol *Func) {
report_fatal_error("unsupported directive in pure streamer");
}
virtual void BeginCOFFSymbolDef(const MCSymbol *Symbol) {
report_fatal_error("unsupported directive in pure streamer");
}
virtual void EmitCOFFSymbolStorageClass(int StorageClass) {
report_fatal_error("unsupported directive in pure streamer");
}
virtual void EmitCOFFSymbolType(int Type) {
report_fatal_error("unsupported directive in pure streamer");
}
virtual void EndCOFFSymbolDef() {
report_fatal_error("unsupported directive in pure streamer");
}
virtual void EmitELFSize(MCSymbol *Symbol, const MCExpr *Value) {
report_fatal_error("unsupported directive in pure streamer");
}
virtual void EmitLocalCommonSymbol(MCSymbol *Symbol, uint64_t Size,
unsigned ByteAlignment) {
report_fatal_error("unsupported directive in pure streamer");
}
virtual void EmitFileDirective(StringRef Filename) {
report_fatal_error("unsupported directive in pure streamer");
}
virtual bool EmitDwarfFileDirective(unsigned FileNo, StringRef Directory,
StringRef Filename) {
report_fatal_error("unsupported directive in pure streamer");
}
/// @}
};
} // end anonymous namespace.
void MCPureStreamer::InitSections() {
// FIMXE: To what!?
SwitchSection(getContext().getMachOSection("__TEXT", "__text",
MCSectionMachO::S_ATTR_PURE_INSTRUCTIONS,
0, SectionKind::getText()));
}
void MCPureStreamer::EmitLabel(MCSymbol *Symbol) {
assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
assert(!Symbol->isVariable() && "Cannot emit a variable symbol!");
assert(getCurrentSection() && "Cannot emit before setting section!");
Symbol->setSection(*getCurrentSection());
MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
// We have to create a new fragment if this is an atom defining symbol,
// fragments cannot span atoms.
if (getAssembler().isSymbolLinkerVisible(SD.getSymbol()))
new MCDataFragment(getCurrentSectionData());
// FIXME: This is wasteful, we don't necessarily need to create a data
// fragment. Instead, we should mark the symbol as pointing into the data
// fragment if it exists, otherwise we should just queue the label and set its
// fragment pointer when we emit the next fragment.
MCDataFragment *F = getOrCreateDataFragment();
assert(!SD.getFragment() && "Unexpected fragment on symbol data!");
SD.setFragment(F);
SD.setOffset(F->getContents().size());
}
This patch is needed to make c++ exceptions work for mips16. Mips16 is really a processor decoding mode (ala thumb 1) and in the same program, mips16 and mips32 functions can exist and can call each other. If a jal type instruction encounters an address with the lower bit set, then the processor switches to mips16 mode (if it is not already in it). If the lower bit is not set, then it switches to mips32 mode. The linker knows which functions are mips16 and which are mips32. When relocation is performed on code labels, this lower order bit is set if the code label is a mips16 code label. In general this works just fine, however when creating exception handling tables and dwarf, there are cases where you don't want this lower order bit added in. This has been traditionally distinguished in gas assembly source by using a different syntax for the label. lab1: ; this will cause the lower order bit to be added lab2=. ; this will not cause the lower order bit to be added In some cases, it does not matter because in dwarf and debug tables the difference of two labels is used and in that case the lower order bits subtract each other out. To fix this, I have added to mcstreamer the notion of a debuglabel. The default is for label and debug label to be the same. So calling EmitLabel and EmitDebugLabel produce the same result. For various reasons, there is only one set of labels that needs to be modified for the mips exceptions to work. These are the "$eh_func_beginXXX" labels. Mips overrides the debug label suffix from ":" to "=." . This initial patch fixes exceptions. More changes most likely will be needed to DwarfCFException to make all of this work for actual debugging. These changes will be to emit debug labels in some places where a simple label is emitted now. Some historical discussion on this from gcc can be found at: http://gcc.gnu.org/ml/gcc-patches/2008-08/msg00623.html http://gcc.gnu.org/ml/gcc-patches/2008-11/msg01273.html llvm-svn: 170279
2012-12-16 12:00:45 +08:00
void MCPureStreamer::EmitDebugLabel(MCSymbol *Symbol) {
EmitLabel(Symbol);
}
void MCPureStreamer::EmitZerofill(const MCSection *Section, MCSymbol *Symbol,
uint64_t Size, unsigned ByteAlignment) {
report_fatal_error("not yet implemented in pure streamer");
}
void MCPureStreamer::EmitBytes(StringRef Data, unsigned AddrSpace) {
// TODO: This is exactly the same as WinCOFFStreamer. Consider merging into
// MCObjectStreamer.
getOrCreateDataFragment()->getContents().append(Data.begin(), Data.end());
}
void MCPureStreamer::EmitValueToAlignment(unsigned ByteAlignment,
int64_t Value, unsigned ValueSize,
unsigned MaxBytesToEmit) {
// TODO: This is exactly the same as WinCOFFStreamer. Consider merging into
// MCObjectStreamer.
if (MaxBytesToEmit == 0)
MaxBytesToEmit = ByteAlignment;
new MCAlignFragment(ByteAlignment, Value, ValueSize, MaxBytesToEmit,
getCurrentSectionData());
// Update the maximum alignment on the current section if necessary.
if (ByteAlignment > getCurrentSectionData()->getAlignment())
getCurrentSectionData()->setAlignment(ByteAlignment);
}
void MCPureStreamer::EmitCodeAlignment(unsigned ByteAlignment,
unsigned MaxBytesToEmit) {
// TODO: This is exactly the same as WinCOFFStreamer. Consider merging into
// MCObjectStreamer.
if (MaxBytesToEmit == 0)
MaxBytesToEmit = ByteAlignment;
MCAlignFragment *F = new MCAlignFragment(ByteAlignment, 0, 1, MaxBytesToEmit,
getCurrentSectionData());
F->setEmitNops(true);
// Update the maximum alignment on the current section if necessary.
if (ByteAlignment > getCurrentSectionData()->getAlignment())
getCurrentSectionData()->setAlignment(ByteAlignment);
}
bool MCPureStreamer::EmitValueToOffset(const MCExpr *Offset,
unsigned char Value) {
new MCOrgFragment(*Offset, Value, getCurrentSectionData());
return false;
}
void MCPureStreamer::EmitInstToFragment(const MCInst &Inst) {
MCInstFragment *IF = new MCInstFragment(Inst, getCurrentSectionData());
// Add the fixups and data.
//
// FIXME: Revisit this design decision when relaxation is done, we may be
// able to get away with not storing any extra data in the MCInst.
SmallVector<MCFixup, 4> Fixups;
SmallString<256> Code;
raw_svector_ostream VecOS(Code);
getAssembler().getEmitter().EncodeInstruction(Inst, VecOS, Fixups);
VecOS.flush();
IF->getContents() = Code;
IF->getFixups() = Fixups;
}
void MCPureStreamer::EmitInstToData(const MCInst &Inst) {
MCDataFragment *DF = getOrCreateDataFragment();
SmallVector<MCFixup, 4> Fixups;
SmallString<256> Code;
raw_svector_ostream VecOS(Code);
getAssembler().getEmitter().EncodeInstruction(Inst, VecOS, Fixups);
VecOS.flush();
// Add the fixups and data.
for (unsigned i = 0, e = Fixups.size(); i != e; ++i) {
Fixups[i].setOffset(Fixups[i].getOffset() + DF->getContents().size());
DF->getFixups().push_back(Fixups[i]);
}
DF->getContents().append(Code.begin(), Code.end());
}
void MCPureStreamer::FinishImpl() {
// FIXME: Handle DWARF tables?
this->MCObjectStreamer::FinishImpl();
}
MCStreamer *llvm::createPureStreamer(MCContext &Context, MCAsmBackend &MAB,
raw_ostream &OS, MCCodeEmitter *CE) {
return new MCPureStreamer(Context, MAB, OS, CE);
}