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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
112 lines
4.3 KiB
C++
112 lines
4.3 KiB
C++
//===- lib/MC/MCNullStreamer.cpp - Dummy Streamer Implementation ----------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/MC/MCStreamer.h"
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#include "llvm/MC/MCContext.h"
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#include "llvm/MC/MCInst.h"
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#include "llvm/MC/MCSectionMachO.h"
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#include "llvm/MC/MCSymbol.h"
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using namespace llvm;
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namespace {
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class MCNullStreamer : public MCStreamer {
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public:
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MCNullStreamer(MCContext &Context) : MCStreamer(Context) {}
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/// @name MCStreamer Interface
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/// @{
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virtual void InitSections() {
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}
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virtual void ChangeSection(const MCSection *Section) {
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}
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virtual void EmitLabel(MCSymbol *Symbol) {
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assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
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assert(getCurrentSection() && "Cannot emit before setting section!");
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Symbol->setSection(*getCurrentSection());
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}
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virtual void EmitDebugLabel(MCSymbol *Symbol) {
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EmitLabel(Symbol);
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}
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virtual void EmitAssemblerFlag(MCAssemblerFlag Flag) {}
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virtual void EmitThumbFunc(MCSymbol *Func) {}
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virtual void EmitAssignment(MCSymbol *Symbol, const MCExpr *Value) {}
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virtual void EmitWeakReference(MCSymbol *Alias, const MCSymbol *Symbol){}
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virtual void EmitDwarfAdvanceLineAddr(int64_t LineDelta,
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const MCSymbol *LastLabel,
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const MCSymbol *Label,
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unsigned PointerSize) {}
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virtual void EmitSymbolAttribute(MCSymbol *Symbol, MCSymbolAttr Attribute){}
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virtual void EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) {}
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virtual void BeginCOFFSymbolDef(const MCSymbol *Symbol) {}
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virtual void EmitCOFFSymbolStorageClass(int StorageClass) {}
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virtual void EmitCOFFSymbolType(int Type) {}
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virtual void EndCOFFSymbolDef() {}
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virtual void EmitCOFFSecRel32(MCSymbol const *Symbol) {}
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virtual void EmitELFSize(MCSymbol *Symbol, const MCExpr *Value) {}
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virtual void EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
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unsigned ByteAlignment) {}
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virtual void EmitLocalCommonSymbol(MCSymbol *Symbol, uint64_t Size,
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unsigned ByteAlignment) {}
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virtual void EmitZerofill(const MCSection *Section, MCSymbol *Symbol = 0,
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uint64_t Size = 0, unsigned ByteAlignment = 0) {}
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virtual void EmitTBSSSymbol(const MCSection *Section, MCSymbol *Symbol,
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uint64_t Size, unsigned ByteAlignment) {}
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virtual void EmitBytes(StringRef Data, unsigned AddrSpace) {}
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virtual void EmitValueImpl(const MCExpr *Value, unsigned Size,
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unsigned AddrSpace) {}
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virtual void EmitULEB128Value(const MCExpr *Value) {}
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virtual void EmitSLEB128Value(const MCExpr *Value) {}
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virtual void EmitGPRel32Value(const MCExpr *Value) {}
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virtual void EmitValueToAlignment(unsigned ByteAlignment, int64_t Value = 0,
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unsigned ValueSize = 1,
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unsigned MaxBytesToEmit = 0) {}
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virtual void EmitCodeAlignment(unsigned ByteAlignment,
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unsigned MaxBytesToEmit = 0) {}
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virtual bool EmitValueToOffset(const MCExpr *Offset,
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unsigned char Value = 0) { return false; }
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virtual void EmitFileDirective(StringRef Filename) {}
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virtual bool EmitDwarfFileDirective(unsigned FileNo, StringRef Directory,
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StringRef Filename) {
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return false;
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}
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virtual void EmitDwarfLocDirective(unsigned FileNo, unsigned Line,
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unsigned Column, unsigned Flags,
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unsigned Isa, unsigned Discriminator,
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StringRef FileName) {}
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virtual void EmitInstruction(const MCInst &Inst) {}
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virtual void FinishImpl() {}
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virtual void EmitCFIEndProcImpl(MCDwarfFrameInfo &Frame) {
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RecordProcEnd(Frame);
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}
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/// @}
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};
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}
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MCStreamer *llvm::createNullStreamer(MCContext &Context) {
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return new MCNullStreamer(Context);
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}
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