diff options
Diffstat (limited to 'lib/CodeGen/AsmPrinter/DwarfTableException.cpp')
| -rw-r--r-- | lib/CodeGen/AsmPrinter/DwarfTableException.cpp | 349 |
1 files changed, 349 insertions, 0 deletions
diff --git a/lib/CodeGen/AsmPrinter/DwarfTableException.cpp b/lib/CodeGen/AsmPrinter/DwarfTableException.cpp new file mode 100644 index 000000000000..751901183cd0 --- /dev/null +++ b/lib/CodeGen/AsmPrinter/DwarfTableException.cpp @@ -0,0 +1,349 @@ +//===-- CodeGen/AsmPrinter/DwarfTableException.cpp - Dwarf Exception Impl --==// +// +// The LLVM Compiler Infrastructure +// +// This file is distributed under the University of Illinois Open Source +// License. See LICENSE.TXT for details. +// +//===----------------------------------------------------------------------===// +// +// This file contains support for writing DWARF exception info into asm files. +// The implementation emits all the necessary tables "by hands". +// +//===----------------------------------------------------------------------===// + +#include "DwarfException.h" +#include "llvm/Module.h" +#include "llvm/CodeGen/AsmPrinter.h" +#include "llvm/CodeGen/MachineModuleInfo.h" +#include "llvm/CodeGen/MachineFrameInfo.h" +#include "llvm/CodeGen/MachineFunction.h" +#include "llvm/CodeGen/MachineLocation.h" +#include "llvm/MC/MCAsmInfo.h" +#include "llvm/MC/MCContext.h" +#include "llvm/MC/MCExpr.h" +#include "llvm/MC/MCSection.h" +#include "llvm/MC/MCStreamer.h" +#include "llvm/MC/MCSymbol.h" +#include "llvm/Target/Mangler.h" +#include "llvm/Target/TargetData.h" +#include "llvm/Target/TargetFrameLowering.h" +#include "llvm/Target/TargetLoweringObjectFile.h" +#include "llvm/Target/TargetMachine.h" +#include "llvm/Target/TargetOptions.h" +#include "llvm/Target/TargetRegisterInfo.h" +#include "llvm/Support/Dwarf.h" +#include "llvm/Support/FormattedStream.h" +#include "llvm/ADT/SmallString.h" +#include "llvm/ADT/StringExtras.h" +#include "llvm/ADT/Twine.h" +using namespace llvm; + +DwarfTableException::DwarfTableException(AsmPrinter *A) + : DwarfException(A), + shouldEmitTable(false), shouldEmitMoves(false), + shouldEmitTableModule(false), shouldEmitMovesModule(false) {} + +DwarfTableException::~DwarfTableException() {} + +/// EmitCIE - Emit a Common Information Entry (CIE). This holds information that +/// is shared among many Frame Description Entries. There is at least one CIE +/// in every non-empty .debug_frame section. +void DwarfTableException::EmitCIE(const Function *PersonalityFn, unsigned Index) { + // Size and sign of stack growth. + int stackGrowth = Asm->getTargetData().getPointerSize(); + if (Asm->TM.getFrameLowering()->getStackGrowthDirection() == + TargetFrameLowering::StackGrowsDown) + stackGrowth *= -1; + + const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering(); + + // Begin eh frame section. + Asm->OutStreamer.SwitchSection(TLOF.getEHFrameSection()); + + MCSymbol *EHFrameSym; + if (TLOF.isFunctionEHFrameSymbolPrivate()) + EHFrameSym = Asm->GetTempSymbol("EH_frame", Index); + else + EHFrameSym = Asm->OutContext.GetOrCreateSymbol(Twine("EH_frame") + + Twine(Index)); + Asm->OutStreamer.EmitLabel(EHFrameSym); + + Asm->OutStreamer.EmitLabel(Asm->GetTempSymbol("section_eh_frame", Index)); + + // Define base labels. + Asm->OutStreamer.EmitLabel(Asm->GetTempSymbol("eh_frame_common", Index)); + + // Define the eh frame length. + Asm->OutStreamer.AddComment("Length of Common Information Entry"); + Asm->EmitLabelDifference(Asm->GetTempSymbol("eh_frame_common_end", Index), + Asm->GetTempSymbol("eh_frame_common_begin", Index), + 4); + + // EH frame header. + Asm->OutStreamer.EmitLabel(Asm->GetTempSymbol("eh_frame_common_begin",Index)); + Asm->OutStreamer.AddComment("CIE Identifier Tag"); + Asm->OutStreamer.EmitIntValue(0, 4/*size*/, 0/*addrspace*/); + Asm->OutStreamer.AddComment("DW_CIE_VERSION"); + Asm->OutStreamer.EmitIntValue(dwarf::DW_CIE_VERSION, 1/*size*/, 0/*addr*/); + + // The personality presence indicates that language specific information will + // show up in the eh frame. Find out how we are supposed to lower the + // personality function reference: + + unsigned LSDAEncoding = TLOF.getLSDAEncoding(); + unsigned FDEEncoding = TLOF.getFDEEncoding(); + unsigned PerEncoding = TLOF.getPersonalityEncoding(); + + char Augmentation[6] = { 0 }; + unsigned AugmentationSize = 0; + char *APtr = Augmentation + 1; + + if (PersonalityFn) { + // There is a personality function. + *APtr++ = 'P'; + AugmentationSize += 1 + Asm->GetSizeOfEncodedValue(PerEncoding); + } + + if (UsesLSDA[Index]) { + // An LSDA pointer is in the FDE augmentation. + *APtr++ = 'L'; + ++AugmentationSize; + } + + if (FDEEncoding != dwarf::DW_EH_PE_absptr) { + // A non-default pointer encoding for the FDE. + *APtr++ = 'R'; + ++AugmentationSize; + } + + if (APtr != Augmentation + 1) + Augmentation[0] = 'z'; + + Asm->OutStreamer.AddComment("CIE Augmentation"); + Asm->OutStreamer.EmitBytes(StringRef(Augmentation, strlen(Augmentation)+1),0); + + // Round out reader. + Asm->EmitULEB128(1, "CIE Code Alignment Factor"); + Asm->EmitSLEB128(stackGrowth, "CIE Data Alignment Factor"); + Asm->OutStreamer.AddComment("CIE Return Address Column"); + + const TargetRegisterInfo *RI = Asm->TM.getRegisterInfo(); + const TargetFrameLowering *TFI = Asm->TM.getFrameLowering(); + Asm->EmitInt8(RI->getDwarfRegNum(RI->getRARegister(), true)); + + if (Augmentation[0]) { + Asm->EmitULEB128(AugmentationSize, "Augmentation Size"); + + // If there is a personality, we need to indicate the function's location. + if (PersonalityFn) { + Asm->EmitEncodingByte(PerEncoding, "Personality"); + Asm->OutStreamer.AddComment("Personality"); + Asm->EmitReference(PersonalityFn, PerEncoding); + } + if (UsesLSDA[Index]) + Asm->EmitEncodingByte(LSDAEncoding, "LSDA"); + if (FDEEncoding != dwarf::DW_EH_PE_absptr) + Asm->EmitEncodingByte(FDEEncoding, "FDE"); + } + + // Indicate locations of general callee saved registers in frame. + std::vector<MachineMove> Moves; + TFI->getInitialFrameState(Moves); + Asm->EmitFrameMoves(Moves, 0, true); + + // On Darwin the linker honors the alignment of eh_frame, which means it must + // be 8-byte on 64-bit targets to match what gcc does. Otherwise you get + // holes which confuse readers of eh_frame. + Asm->EmitAlignment(Asm->getTargetData().getPointerSize() == 4 ? 2 : 3); + Asm->OutStreamer.EmitLabel(Asm->GetTempSymbol("eh_frame_common_end", Index)); +} + +/// EmitFDE - Emit the Frame Description Entry (FDE) for the function. +void DwarfTableException::EmitFDE(const FunctionEHFrameInfo &EHFrameInfo) { + assert(!EHFrameInfo.function->hasAvailableExternallyLinkage() && + "Should not emit 'available externally' functions at all"); + + const Function *TheFunc = EHFrameInfo.function; + const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering(); + + unsigned LSDAEncoding = TLOF.getLSDAEncoding(); + unsigned FDEEncoding = TLOF.getFDEEncoding(); + + Asm->OutStreamer.SwitchSection(TLOF.getEHFrameSection()); + + // Externally visible entry into the functions eh frame info. If the + // corresponding function is static, this should not be externally visible. + if (!TheFunc->hasLocalLinkage() && TLOF.isFunctionEHSymbolGlobal()) + Asm->OutStreamer.EmitSymbolAttribute(EHFrameInfo.FunctionEHSym,MCSA_Global); + + // If corresponding function is weak definition, this should be too. + if (TheFunc->isWeakForLinker() && Asm->MAI->getWeakDefDirective()) + Asm->OutStreamer.EmitSymbolAttribute(EHFrameInfo.FunctionEHSym, + MCSA_WeakDefinition); + + // If corresponding function is hidden, this should be too. + if (TheFunc->hasHiddenVisibility()) + if (MCSymbolAttr HiddenAttr = Asm->MAI->getHiddenVisibilityAttr()) + Asm->OutStreamer.EmitSymbolAttribute(EHFrameInfo.FunctionEHSym, + HiddenAttr); + + // If there are no calls then you can't unwind. This may mean we can omit the + // EH Frame, but some environments do not handle weak absolute symbols. If + // UnwindTablesMandatory is set we cannot do this optimization; the unwind + // info is to be available for non-EH uses. + if (!EHFrameInfo.adjustsStack && !UnwindTablesMandatory && + (!TheFunc->isWeakForLinker() || + !Asm->MAI->getWeakDefDirective() || + TLOF.getSupportsWeakOmittedEHFrame())) { + Asm->OutStreamer.EmitAssignment(EHFrameInfo.FunctionEHSym, + MCConstantExpr::Create(0, Asm->OutContext)); + // This name has no connection to the function, so it might get + // dead-stripped when the function is not, erroneously. Prohibit + // dead-stripping unconditionally. + if (Asm->MAI->hasNoDeadStrip()) + Asm->OutStreamer.EmitSymbolAttribute(EHFrameInfo.FunctionEHSym, + MCSA_NoDeadStrip); + } else { + Asm->OutStreamer.EmitLabel(EHFrameInfo.FunctionEHSym); + + // EH frame header. + Asm->OutStreamer.AddComment("Length of Frame Information Entry"); + Asm->EmitLabelDifference( + Asm->GetTempSymbol("eh_frame_end", EHFrameInfo.Number), + Asm->GetTempSymbol("eh_frame_begin", EHFrameInfo.Number), 4); + + Asm->OutStreamer.EmitLabel(Asm->GetTempSymbol("eh_frame_begin", + EHFrameInfo.Number)); + + Asm->OutStreamer.AddComment("FDE CIE offset"); + Asm->EmitLabelDifference( + Asm->GetTempSymbol("eh_frame_begin", EHFrameInfo.Number), + Asm->GetTempSymbol("eh_frame_common", + EHFrameInfo.PersonalityIndex), 4); + + MCSymbol *EHFuncBeginSym = + Asm->GetTempSymbol("eh_func_begin", EHFrameInfo.Number); + + Asm->OutStreamer.AddComment("FDE initial location"); + Asm->EmitReference(EHFuncBeginSym, FDEEncoding); + + Asm->OutStreamer.AddComment("FDE address range"); + Asm->EmitLabelDifference(Asm->GetTempSymbol("eh_func_end", + EHFrameInfo.Number), + EHFuncBeginSym, + Asm->GetSizeOfEncodedValue(FDEEncoding)); + + // If there is a personality and landing pads then point to the language + // specific data area in the exception table. + if (MMI->getPersonalities()[0] != NULL) { + unsigned Size = Asm->GetSizeOfEncodedValue(LSDAEncoding); + + Asm->EmitULEB128(Size, "Augmentation size"); + Asm->OutStreamer.AddComment("Language Specific Data Area"); + if (EHFrameInfo.hasLandingPads) + Asm->EmitReference(Asm->GetTempSymbol("exception", EHFrameInfo.Number), + LSDAEncoding); + else + Asm->OutStreamer.EmitIntValue(0, Size/*size*/, 0/*addrspace*/); + + } else { + Asm->EmitULEB128(0, "Augmentation size"); + } + + // Indicate locations of function specific callee saved registers in frame. + Asm->EmitFrameMoves(EHFrameInfo.Moves, EHFuncBeginSym, true); + + // On Darwin the linker honors the alignment of eh_frame, which means it + // must be 8-byte on 64-bit targets to match what gcc does. Otherwise you + // get holes which confuse readers of eh_frame. + Asm->EmitAlignment(Asm->getTargetData().getPointerSize() == 4 ? 2 : 3); + Asm->OutStreamer.EmitLabel(Asm->GetTempSymbol("eh_frame_end", + EHFrameInfo.Number)); + + // If the function is marked used, this table should be also. We cannot + // make the mark unconditional in this case, since retaining the table also + // retains the function in this case, and there is code around that depends + // on unused functions (calling undefined externals) being dead-stripped to + // link correctly. Yes, there really is. + if (MMI->isUsedFunction(EHFrameInfo.function)) + if (Asm->MAI->hasNoDeadStrip()) + Asm->OutStreamer.EmitSymbolAttribute(EHFrameInfo.FunctionEHSym, + MCSA_NoDeadStrip); + } + Asm->OutStreamer.AddBlankLine(); +} + +/// EndModule - Emit all exception information that should come after the +/// content. +void DwarfTableException::EndModule() { + if (!Asm->MAI->isExceptionHandlingDwarf()) + return; + + if (!shouldEmitMovesModule && !shouldEmitTableModule) + return; + + const std::vector<const Function*> &Personalities = MMI->getPersonalities(); + + for (unsigned I = 0, E = Personalities.size(); I < E; ++I) + EmitCIE(Personalities[I], I); + + for (std::vector<FunctionEHFrameInfo>::iterator + I = EHFrames.begin(), E = EHFrames.end(); I != E; ++I) + EmitFDE(*I); +} + +/// BeginFunction - Gather pre-function exception information. Assumes it's +/// being emitted immediately after the function entry point. +void DwarfTableException::BeginFunction(const MachineFunction *MF) { + shouldEmitTable = shouldEmitMoves = false; + + // If any landing pads survive, we need an EH table. + shouldEmitTable = !MMI->getLandingPads().empty(); + + // See if we need frame move info. + shouldEmitMoves = + !Asm->MF->getFunction()->doesNotThrow() || UnwindTablesMandatory; + + if (shouldEmitMoves || shouldEmitTable) + // Assumes in correct section after the entry point. + Asm->OutStreamer.EmitLabel(Asm->GetTempSymbol("eh_func_begin", + Asm->getFunctionNumber())); + + shouldEmitTableModule |= shouldEmitTable; + shouldEmitMovesModule |= shouldEmitMoves; +} + +/// EndFunction - Gather and emit post-function exception information. +/// +void DwarfTableException::EndFunction() { + if (!shouldEmitMoves && !shouldEmitTable) return; + + Asm->OutStreamer.EmitLabel(Asm->GetTempSymbol("eh_func_end", + Asm->getFunctionNumber())); + + // Record if this personality index uses a landing pad. + bool HasLandingPad = !MMI->getLandingPads().empty(); + UsesLSDA[MMI->getPersonalityIndex()] |= HasLandingPad; + + // Map all labels and get rid of any dead landing pads. + MMI->TidyLandingPads(); + + if (HasLandingPad) + EmitExceptionTable(); + + const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering(); + MCSymbol *FunctionEHSym = + Asm->GetSymbolWithGlobalValueBase(Asm->MF->getFunction(), ".eh", + TLOF.isFunctionEHFrameSymbolPrivate()); + + // Save EH frame information + EHFrames. + push_back(FunctionEHFrameInfo(FunctionEHSym, + Asm->getFunctionNumber(), + MMI->getPersonalityIndex(), + Asm->MF->getFrameInfo()->adjustsStack(), + !MMI->getLandingPads().empty(), + MMI->getFrameMoves(), + Asm->MF->getFunction())); +} |