llvm-6502/include/llvm/MC/MCELFStreamer.h
Reed Kotler 2c3a4641a7 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 



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@170279 91177308-0d34-0410-b5e6-96231b3b80d8
2012-12-16 04:00:45 +00:00

109 lines
3.4 KiB
C++

//===- MCELFStreamer.h - MCStreamer ELF Object File Interface ---*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_MC_MCELFSTREAMER_H
#define LLVM_MC_MCELFSTREAMER_H
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/MC/MCDirectives.h"
#include "llvm/MC/MCObjectStreamer.h"
#include "llvm/MC/SectionKind.h"
#include "llvm/Support/DataTypes.h"
#include <vector>
namespace llvm {
class MCAsmBackend;
class MCAssembler;
class MCCodeEmitter;
class MCExpr;
class MCInst;
class MCSymbol;
class MCSymbolData;
class raw_ostream;
class MCELFStreamer : public MCObjectStreamer {
public:
MCELFStreamer(MCContext &Context, MCAsmBackend &TAB,
raw_ostream &OS, MCCodeEmitter *Emitter)
: MCObjectStreamer(Context, TAB, OS, Emitter) {}
MCELFStreamer(MCContext &Context, MCAsmBackend &TAB,
raw_ostream &OS, MCCodeEmitter *Emitter,
MCAssembler *Assembler)
: MCObjectStreamer(Context, TAB, OS, Emitter, Assembler) {}
virtual ~MCELFStreamer();
/// @name MCStreamer Interface
/// @{
virtual void InitSections();
virtual void ChangeSection(const MCSection *Section);
virtual void EmitLabel(MCSymbol *Symbol);
virtual void EmitDebugLabel(MCSymbol *Symbol);
virtual void EmitAssemblerFlag(MCAssemblerFlag Flag);
virtual void EmitThumbFunc(MCSymbol *Func);
virtual void EmitWeakReference(MCSymbol *Alias, const MCSymbol *Symbol);
virtual void EmitSymbolAttribute(MCSymbol *Symbol, MCSymbolAttr Attribute);
virtual void EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue);
virtual void EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
unsigned ByteAlignment);
virtual void BeginCOFFSymbolDef(const MCSymbol *Symbol);
virtual void EmitCOFFSymbolStorageClass(int StorageClass);
virtual void EmitCOFFSymbolType(int Type);
virtual void EndCOFFSymbolDef();
virtual void EmitELFSize(MCSymbol *Symbol, const MCExpr *Value);
virtual void EmitLocalCommonSymbol(MCSymbol *Symbol, uint64_t Size,
unsigned ByteAlignment);
virtual void EmitZerofill(const MCSection *Section, MCSymbol *Symbol = 0,
uint64_t Size = 0, unsigned ByteAlignment = 0);
virtual void EmitTBSSSymbol(const MCSection *Section, MCSymbol *Symbol,
uint64_t Size, unsigned ByteAlignment = 0);
virtual void EmitValueImpl(const MCExpr *Value, unsigned Size,
unsigned AddrSpace);
virtual void EmitFileDirective(StringRef Filename);
virtual void EmitTCEntry(const MCSymbol &S);
virtual void FinishImpl();
/// @}
private:
virtual void EmitInstToFragment(const MCInst &Inst);
virtual void EmitInstToData(const MCInst &Inst);
void fixSymbolsInTLSFixups(const MCExpr *expr);
struct LocalCommon {
MCSymbolData *SD;
uint64_t Size;
unsigned ByteAlignment;
};
std::vector<LocalCommon> LocalCommons;
SmallPtrSet<MCSymbol *, 16> BindingExplicitlySet;
void SetSection(StringRef Section, unsigned Type, unsigned Flags,
SectionKind Kind);
void SetSectionData();
void SetSectionText();
void SetSectionBss();
};
} // end namespace llvm
#endif