| //===-- CodeGen/AsmPrinter/DwarfException.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. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #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/TargetFrameInfo.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; |
| |
| DwarfException::DwarfException(AsmPrinter *A) |
| : Asm(A), MMI(Asm->MMI), shouldEmitTable(false), shouldEmitMoves(false), |
| shouldEmitTableModule(false), shouldEmitMovesModule(false) {} |
| |
| DwarfException::~DwarfException() {} |
| |
| /// 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 DwarfException::EmitCIE(const Function *PersonalityFn, unsigned Index) { |
| // Size and sign of stack growth. |
| int stackGrowth = Asm->getTargetData().getPointerSize(); |
| if (Asm->TM.getFrameInfo()->getStackGrowthDirection() == |
| TargetFrameInfo::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(); |
| 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; |
| RI->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 DwarfException::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(); |
| } |
| |
| /// SharedTypeIds - How many leading type ids two landing pads have in common. |
| unsigned DwarfException::SharedTypeIds(const LandingPadInfo *L, |
| const LandingPadInfo *R) { |
| const std::vector<int> &LIds = L->TypeIds, &RIds = R->TypeIds; |
| unsigned LSize = LIds.size(), RSize = RIds.size(); |
| unsigned MinSize = LSize < RSize ? LSize : RSize; |
| unsigned Count = 0; |
| |
| for (; Count != MinSize; ++Count) |
| if (LIds[Count] != RIds[Count]) |
| return Count; |
| |
| return Count; |
| } |
| |
| /// PadLT - Order landing pads lexicographically by type id. |
| bool DwarfException::PadLT(const LandingPadInfo *L, const LandingPadInfo *R) { |
| const std::vector<int> &LIds = L->TypeIds, &RIds = R->TypeIds; |
| unsigned LSize = LIds.size(), RSize = RIds.size(); |
| unsigned MinSize = LSize < RSize ? LSize : RSize; |
| |
| for (unsigned i = 0; i != MinSize; ++i) |
| if (LIds[i] != RIds[i]) |
| return LIds[i] < RIds[i]; |
| |
| return LSize < RSize; |
| } |
| |
| /// ComputeActionsTable - Compute the actions table and gather the first action |
| /// index for each landing pad site. |
| unsigned DwarfException:: |
| ComputeActionsTable(const SmallVectorImpl<const LandingPadInfo*> &LandingPads, |
| SmallVectorImpl<ActionEntry> &Actions, |
| SmallVectorImpl<unsigned> &FirstActions) { |
| |
| // The action table follows the call-site table in the LSDA. The individual |
| // records are of two types: |
| // |
| // * Catch clause |
| // * Exception specification |
| // |
| // The two record kinds have the same format, with only small differences. |
| // They are distinguished by the "switch value" field: Catch clauses |
| // (TypeInfos) have strictly positive switch values, and exception |
| // specifications (FilterIds) have strictly negative switch values. Value 0 |
| // indicates a catch-all clause. |
| // |
| // Negative type IDs index into FilterIds. Positive type IDs index into |
| // TypeInfos. The value written for a positive type ID is just the type ID |
| // itself. For a negative type ID, however, the value written is the |
| // (negative) byte offset of the corresponding FilterIds entry. The byte |
| // offset is usually equal to the type ID (because the FilterIds entries are |
| // written using a variable width encoding, which outputs one byte per entry |
| // as long as the value written is not too large) but can differ. This kind |
| // of complication does not occur for positive type IDs because type infos are |
| // output using a fixed width encoding. FilterOffsets[i] holds the byte |
| // offset corresponding to FilterIds[i]. |
| |
| const std::vector<unsigned> &FilterIds = MMI->getFilterIds(); |
| SmallVector<int, 16> FilterOffsets; |
| FilterOffsets.reserve(FilterIds.size()); |
| int Offset = -1; |
| |
| for (std::vector<unsigned>::const_iterator |
| I = FilterIds.begin(), E = FilterIds.end(); I != E; ++I) { |
| FilterOffsets.push_back(Offset); |
| Offset -= MCAsmInfo::getULEB128Size(*I); |
| } |
| |
| FirstActions.reserve(LandingPads.size()); |
| |
| int FirstAction = 0; |
| unsigned SizeActions = 0; |
| const LandingPadInfo *PrevLPI = 0; |
| |
| for (SmallVectorImpl<const LandingPadInfo *>::const_iterator |
| I = LandingPads.begin(), E = LandingPads.end(); I != E; ++I) { |
| const LandingPadInfo *LPI = *I; |
| const std::vector<int> &TypeIds = LPI->TypeIds; |
| unsigned NumShared = PrevLPI ? SharedTypeIds(LPI, PrevLPI) : 0; |
| unsigned SizeSiteActions = 0; |
| |
| if (NumShared < TypeIds.size()) { |
| unsigned SizeAction = 0; |
| unsigned PrevAction = (unsigned)-1; |
| |
| if (NumShared) { |
| unsigned SizePrevIds = PrevLPI->TypeIds.size(); |
| assert(Actions.size()); |
| PrevAction = Actions.size() - 1; |
| SizeAction = |
| MCAsmInfo::getSLEB128Size(Actions[PrevAction].NextAction) + |
| MCAsmInfo::getSLEB128Size(Actions[PrevAction].ValueForTypeID); |
| |
| for (unsigned j = NumShared; j != SizePrevIds; ++j) { |
| assert(PrevAction != (unsigned)-1 && "PrevAction is invalid!"); |
| SizeAction -= |
| MCAsmInfo::getSLEB128Size(Actions[PrevAction].ValueForTypeID); |
| SizeAction += -Actions[PrevAction].NextAction; |
| PrevAction = Actions[PrevAction].Previous; |
| } |
| } |
| |
| // Compute the actions. |
| for (unsigned J = NumShared, M = TypeIds.size(); J != M; ++J) { |
| int TypeID = TypeIds[J]; |
| assert(-1 - TypeID < (int)FilterOffsets.size() && "Unknown filter id!"); |
| int ValueForTypeID = TypeID < 0 ? FilterOffsets[-1 - TypeID] : TypeID; |
| unsigned SizeTypeID = MCAsmInfo::getSLEB128Size(ValueForTypeID); |
| |
| int NextAction = SizeAction ? -(SizeAction + SizeTypeID) : 0; |
| SizeAction = SizeTypeID + MCAsmInfo::getSLEB128Size(NextAction); |
| SizeSiteActions += SizeAction; |
| |
| ActionEntry Action = { ValueForTypeID, NextAction, PrevAction }; |
| Actions.push_back(Action); |
| PrevAction = Actions.size() - 1; |
| } |
| |
| // Record the first action of the landing pad site. |
| FirstAction = SizeActions + SizeSiteActions - SizeAction + 1; |
| } // else identical - re-use previous FirstAction |
| |
| // Information used when created the call-site table. The action record |
| // field of the call site record is the offset of the first associated |
| // action record, relative to the start of the actions table. This value is |
| // biased by 1 (1 indicating the start of the actions table), and 0 |
| // indicates that there are no actions. |
| FirstActions.push_back(FirstAction); |
| |
| // Compute this sites contribution to size. |
| SizeActions += SizeSiteActions; |
| |
| PrevLPI = LPI; |
| } |
| |
| return SizeActions; |
| } |
| |
| /// CallToNoUnwindFunction - Return `true' if this is a call to a function |
| /// marked `nounwind'. Return `false' otherwise. |
| bool DwarfException::CallToNoUnwindFunction(const MachineInstr *MI) { |
| assert(MI->getDesc().isCall() && "This should be a call instruction!"); |
| |
| bool MarkedNoUnwind = false; |
| bool SawFunc = false; |
| |
| for (unsigned I = 0, E = MI->getNumOperands(); I != E; ++I) { |
| const MachineOperand &MO = MI->getOperand(I); |
| |
| if (!MO.isGlobal()) continue; |
| |
| const Function *F = dyn_cast<Function>(MO.getGlobal()); |
| if (F == 0) continue; |
| |
| if (SawFunc) { |
| // Be conservative. If we have more than one function operand for this |
| // call, then we can't make the assumption that it's the callee and |
| // not a parameter to the call. |
| // |
| // FIXME: Determine if there's a way to say that `F' is the callee or |
| // parameter. |
| MarkedNoUnwind = false; |
| break; |
| } |
| |
| MarkedNoUnwind = F->doesNotThrow(); |
| SawFunc = true; |
| } |
| |
| return MarkedNoUnwind; |
| } |
| |
| /// ComputeCallSiteTable - Compute the call-site table. The entry for an invoke |
| /// has a try-range containing the call, a non-zero landing pad, and an |
| /// appropriate action. The entry for an ordinary call has a try-range |
| /// containing the call and zero for the landing pad and the action. Calls |
| /// marked 'nounwind' have no entry and must not be contained in the try-range |
| /// of any entry - they form gaps in the table. Entries must be ordered by |
| /// try-range address. |
| void DwarfException:: |
| ComputeCallSiteTable(SmallVectorImpl<CallSiteEntry> &CallSites, |
| const RangeMapType &PadMap, |
| const SmallVectorImpl<const LandingPadInfo *> &LandingPads, |
| const SmallVectorImpl<unsigned> &FirstActions) { |
| // The end label of the previous invoke or nounwind try-range. |
| MCSymbol *LastLabel = 0; |
| |
| // Whether there is a potentially throwing instruction (currently this means |
| // an ordinary call) between the end of the previous try-range and now. |
| bool SawPotentiallyThrowing = false; |
| |
| // Whether the last CallSite entry was for an invoke. |
| bool PreviousIsInvoke = false; |
| |
| // Visit all instructions in order of address. |
| for (MachineFunction::const_iterator I = Asm->MF->begin(), E = Asm->MF->end(); |
| I != E; ++I) { |
| for (MachineBasicBlock::const_iterator MI = I->begin(), E = I->end(); |
| MI != E; ++MI) { |
| if (!MI->isLabel()) { |
| if (MI->getDesc().isCall()) |
| SawPotentiallyThrowing |= !CallToNoUnwindFunction(MI); |
| continue; |
| } |
| |
| // End of the previous try-range? |
| MCSymbol *BeginLabel = MI->getOperand(0).getMCSymbol(); |
| if (BeginLabel == LastLabel) |
| SawPotentiallyThrowing = false; |
| |
| // Beginning of a new try-range? |
| RangeMapType::const_iterator L = PadMap.find(BeginLabel); |
| if (L == PadMap.end()) |
| // Nope, it was just some random label. |
| continue; |
| |
| const PadRange &P = L->second; |
| const LandingPadInfo *LandingPad = LandingPads[P.PadIndex]; |
| assert(BeginLabel == LandingPad->BeginLabels[P.RangeIndex] && |
| "Inconsistent landing pad map!"); |
| |
| // For Dwarf exception handling (SjLj handling doesn't use this). If some |
| // instruction between the previous try-range and this one may throw, |
| // create a call-site entry with no landing pad for the region between the |
| // try-ranges. |
| if (SawPotentiallyThrowing && |
| Asm->MAI->getExceptionHandlingType() == ExceptionHandling::Dwarf) { |
| CallSiteEntry Site = { LastLabel, BeginLabel, 0, 0 }; |
| CallSites.push_back(Site); |
| PreviousIsInvoke = false; |
| } |
| |
| LastLabel = LandingPad->EndLabels[P.RangeIndex]; |
| assert(BeginLabel && LastLabel && "Invalid landing pad!"); |
| |
| if (!LandingPad->LandingPadLabel) { |
| // Create a gap. |
| PreviousIsInvoke = false; |
| } else { |
| // This try-range is for an invoke. |
| CallSiteEntry Site = { |
| BeginLabel, |
| LastLabel, |
| LandingPad->LandingPadLabel, |
| FirstActions[P.PadIndex] |
| }; |
| |
| // Try to merge with the previous call-site. SJLJ doesn't do this |
| if (PreviousIsInvoke && |
| Asm->MAI->getExceptionHandlingType() == ExceptionHandling::Dwarf) { |
| CallSiteEntry &Prev = CallSites.back(); |
| if (Site.PadLabel == Prev.PadLabel && Site.Action == Prev.Action) { |
| // Extend the range of the previous entry. |
| Prev.EndLabel = Site.EndLabel; |
| continue; |
| } |
| } |
| |
| // Otherwise, create a new call-site. |
| if (Asm->MAI->getExceptionHandlingType() == ExceptionHandling::Dwarf) |
| CallSites.push_back(Site); |
| else { |
| // SjLj EH must maintain the call sites in the order assigned |
| // to them by the SjLjPrepare pass. |
| unsigned SiteNo = MMI->getCallSiteBeginLabel(BeginLabel); |
| if (CallSites.size() < SiteNo) |
| CallSites.resize(SiteNo); |
| CallSites[SiteNo - 1] = Site; |
| } |
| PreviousIsInvoke = true; |
| } |
| } |
| } |
| |
| // If some instruction between the previous try-range and the end of the |
| // function may throw, create a call-site entry with no landing pad for the |
| // region following the try-range. |
| if (SawPotentiallyThrowing && |
| Asm->MAI->getExceptionHandlingType() == ExceptionHandling::Dwarf) { |
| CallSiteEntry Site = { LastLabel, 0, 0, 0 }; |
| CallSites.push_back(Site); |
| } |
| } |
| |
| /// EmitExceptionTable - Emit landing pads and actions. |
| /// |
| /// The general organization of the table is complex, but the basic concepts are |
| /// easy. First there is a header which describes the location and organization |
| /// of the three components that follow. |
| /// |
| /// 1. The landing pad site information describes the range of code covered by |
| /// the try. In our case it's an accumulation of the ranges covered by the |
| /// invokes in the try. There is also a reference to the landing pad that |
| /// handles the exception once processed. Finally an index into the actions |
| /// table. |
| /// 2. The action table, in our case, is composed of pairs of type IDs and next |
| /// action offset. Starting with the action index from the landing pad |
| /// site, each type ID is checked for a match to the current exception. If |
| /// it matches then the exception and type id are passed on to the landing |
| /// pad. Otherwise the next action is looked up. This chain is terminated |
| /// with a next action of zero. If no type id is found then the frame is |
| /// unwound and handling continues. |
| /// 3. Type ID table contains references to all the C++ typeinfo for all |
| /// catches in the function. This tables is reverse indexed base 1. |
| void DwarfException::EmitExceptionTable() { |
| const std::vector<const GlobalVariable *> &TypeInfos = MMI->getTypeInfos(); |
| const std::vector<unsigned> &FilterIds = MMI->getFilterIds(); |
| const std::vector<LandingPadInfo> &PadInfos = MMI->getLandingPads(); |
| |
| // Sort the landing pads in order of their type ids. This is used to fold |
| // duplicate actions. |
| SmallVector<const LandingPadInfo *, 64> LandingPads; |
| LandingPads.reserve(PadInfos.size()); |
| |
| for (unsigned i = 0, N = PadInfos.size(); i != N; ++i) |
| LandingPads.push_back(&PadInfos[i]); |
| |
| std::sort(LandingPads.begin(), LandingPads.end(), PadLT); |
| |
| // Compute the actions table and gather the first action index for each |
| // landing pad site. |
| SmallVector<ActionEntry, 32> Actions; |
| SmallVector<unsigned, 64> FirstActions; |
| unsigned SizeActions=ComputeActionsTable(LandingPads, Actions, FirstActions); |
| |
| // Invokes and nounwind calls have entries in PadMap (due to being bracketed |
| // by try-range labels when lowered). Ordinary calls do not, so appropriate |
| // try-ranges for them need be deduced when using DWARF exception handling. |
| RangeMapType PadMap; |
| for (unsigned i = 0, N = LandingPads.size(); i != N; ++i) { |
| const LandingPadInfo *LandingPad = LandingPads[i]; |
| for (unsigned j = 0, E = LandingPad->BeginLabels.size(); j != E; ++j) { |
| MCSymbol *BeginLabel = LandingPad->BeginLabels[j]; |
| assert(!PadMap.count(BeginLabel) && "Duplicate landing pad labels!"); |
| PadRange P = { i, j }; |
| PadMap[BeginLabel] = P; |
| } |
| } |
| |
| // Compute the call-site table. |
| SmallVector<CallSiteEntry, 64> CallSites; |
| ComputeCallSiteTable(CallSites, PadMap, LandingPads, FirstActions); |
| |
| // Final tallies. |
| |
| // Call sites. |
| bool IsSJLJ = Asm->MAI->getExceptionHandlingType() == ExceptionHandling::SjLj; |
| bool HaveTTData = IsSJLJ ? (!TypeInfos.empty() || !FilterIds.empty()) : true; |
| |
| unsigned CallSiteTableLength; |
| if (IsSJLJ) |
| CallSiteTableLength = 0; |
| else { |
| unsigned SiteStartSize = 4; // dwarf::DW_EH_PE_udata4 |
| unsigned SiteLengthSize = 4; // dwarf::DW_EH_PE_udata4 |
| unsigned LandingPadSize = 4; // dwarf::DW_EH_PE_udata4 |
| CallSiteTableLength = |
| CallSites.size() * (SiteStartSize + SiteLengthSize + LandingPadSize); |
| } |
| |
| for (unsigned i = 0, e = CallSites.size(); i < e; ++i) { |
| CallSiteTableLength += MCAsmInfo::getULEB128Size(CallSites[i].Action); |
| if (IsSJLJ) |
| CallSiteTableLength += MCAsmInfo::getULEB128Size(i); |
| } |
| |
| // Type infos. |
| const MCSection *LSDASection = Asm->getObjFileLowering().getLSDASection(); |
| unsigned TTypeEncoding; |
| unsigned TypeFormatSize; |
| |
| if (!HaveTTData) { |
| // For SjLj exceptions, if there is no TypeInfo, then we just explicitly say |
| // that we're omitting that bit. |
| TTypeEncoding = dwarf::DW_EH_PE_omit; |
| // dwarf::DW_EH_PE_absptr |
| TypeFormatSize = Asm->getTargetData().getPointerSize(); |
| } else { |
| // Okay, we have actual filters or typeinfos to emit. As such, we need to |
| // pick a type encoding for them. We're about to emit a list of pointers to |
| // typeinfo objects at the end of the LSDA. However, unless we're in static |
| // mode, this reference will require a relocation by the dynamic linker. |
| // |
| // Because of this, we have a couple of options: |
| // |
| // 1) If we are in -static mode, we can always use an absolute reference |
| // from the LSDA, because the static linker will resolve it. |
| // |
| // 2) Otherwise, if the LSDA section is writable, we can output the direct |
| // reference to the typeinfo and allow the dynamic linker to relocate |
| // it. Since it is in a writable section, the dynamic linker won't |
| // have a problem. |
| // |
| // 3) Finally, if we're in PIC mode and the LDSA section isn't writable, |
| // we need to use some form of indirection. For example, on Darwin, |
| // we can output a statically-relocatable reference to a dyld stub. The |
| // offset to the stub is constant, but the contents are in a section |
| // that is updated by the dynamic linker. This is easy enough, but we |
| // need to tell the personality function of the unwinder to indirect |
| // through the dyld stub. |
| // |
| // FIXME: When (3) is actually implemented, we'll have to emit the stubs |
| // somewhere. This predicate should be moved to a shared location that is |
| // in target-independent code. |
| // |
| TTypeEncoding = Asm->getObjFileLowering().getTTypeEncoding(); |
| TypeFormatSize = Asm->GetSizeOfEncodedValue(TTypeEncoding); |
| } |
| |
| // Begin the exception table. |
| Asm->OutStreamer.SwitchSection(LSDASection); |
| Asm->EmitAlignment(2); |
| |
| // Emit the LSDA. |
| MCSymbol *GCCETSym = |
| Asm->OutContext.GetOrCreateSymbol(Twine("GCC_except_table")+ |
| Twine(Asm->getFunctionNumber())); |
| Asm->OutStreamer.EmitLabel(GCCETSym); |
| Asm->OutStreamer.EmitLabel(Asm->GetTempSymbol("exception", |
| Asm->getFunctionNumber())); |
| |
| if (IsSJLJ) |
| Asm->OutStreamer.EmitLabel(Asm->GetTempSymbol("_LSDA_", |
| Asm->getFunctionNumber())); |
| |
| // Emit the LSDA header. |
| Asm->EmitEncodingByte(dwarf::DW_EH_PE_omit, "@LPStart"); |
| Asm->EmitEncodingByte(TTypeEncoding, "@TType"); |
| |
| // The type infos need to be aligned. GCC does this by inserting padding just |
| // before the type infos. However, this changes the size of the exception |
| // table, so you need to take this into account when you output the exception |
| // table size. However, the size is output using a variable length encoding. |
| // So by increasing the size by inserting padding, you may increase the number |
| // of bytes used for writing the size. If it increases, say by one byte, then |
| // you now need to output one less byte of padding to get the type infos |
| // aligned. However this decreases the size of the exception table. This |
| // changes the value you have to output for the exception table size. Due to |
| // the variable length encoding, the number of bytes used for writing the |
| // length may decrease. If so, you then have to increase the amount of |
| // padding. And so on. If you look carefully at the GCC code you will see that |
| // it indeed does this in a loop, going on and on until the values stabilize. |
| // We chose another solution: don't output padding inside the table like GCC |
| // does, instead output it before the table. |
| unsigned SizeTypes = TypeInfos.size() * TypeFormatSize; |
| unsigned CallSiteTableLengthSize = |
| MCAsmInfo::getULEB128Size(CallSiteTableLength); |
| unsigned TTypeBaseOffset = |
| sizeof(int8_t) + // Call site format |
| CallSiteTableLengthSize + // Call site table length size |
| CallSiteTableLength + // Call site table length |
| SizeActions + // Actions size |
| SizeTypes; |
| unsigned TTypeBaseOffsetSize = MCAsmInfo::getULEB128Size(TTypeBaseOffset); |
| unsigned TotalSize = |
| sizeof(int8_t) + // LPStart format |
| sizeof(int8_t) + // TType format |
| (HaveTTData ? TTypeBaseOffsetSize : 0) + // TType base offset size |
| TTypeBaseOffset; // TType base offset |
| unsigned SizeAlign = (4 - TotalSize) & 3; |
| |
| if (HaveTTData) { |
| // Account for any extra padding that will be added to the call site table |
| // length. |
| Asm->EmitULEB128(TTypeBaseOffset, "@TType base offset", SizeAlign); |
| SizeAlign = 0; |
| } |
| |
| // SjLj Exception handling |
| if (IsSJLJ) { |
| Asm->EmitEncodingByte(dwarf::DW_EH_PE_udata4, "Call site"); |
| |
| // Add extra padding if it wasn't added to the TType base offset. |
| Asm->EmitULEB128(CallSiteTableLength, "Call site table length", SizeAlign); |
| |
| // Emit the landing pad site information. |
| unsigned idx = 0; |
| for (SmallVectorImpl<CallSiteEntry>::const_iterator |
| I = CallSites.begin(), E = CallSites.end(); I != E; ++I, ++idx) { |
| const CallSiteEntry &S = *I; |
| |
| // Offset of the landing pad, counted in 16-byte bundles relative to the |
| // @LPStart address. |
| Asm->EmitULEB128(idx, "Landing pad"); |
| |
| // Offset of the first associated action record, relative to the start of |
| // the action table. This value is biased by 1 (1 indicates the start of |
| // the action table), and 0 indicates that there are no actions. |
| Asm->EmitULEB128(S.Action, "Action"); |
| } |
| } else { |
| // DWARF Exception handling |
| assert(Asm->MAI->getExceptionHandlingType() == ExceptionHandling::Dwarf); |
| |
| // The call-site table is a list of all call sites that may throw an |
| // exception (including C++ 'throw' statements) in the procedure |
| // fragment. It immediately follows the LSDA header. Each entry indicates, |
| // for a given call, the first corresponding action record and corresponding |
| // landing pad. |
| // |
| // The table begins with the number of bytes, stored as an LEB128 |
| // compressed, unsigned integer. The records immediately follow the record |
| // count. They are sorted in increasing call-site address. Each record |
| // indicates: |
| // |
| // * The position of the call-site. |
| // * The position of the landing pad. |
| // * The first action record for that call site. |
| // |
| // A missing entry in the call-site table indicates that a call is not |
| // supposed to throw. |
| |
| // Emit the landing pad call site table. |
| Asm->EmitEncodingByte(dwarf::DW_EH_PE_udata4, "Call site"); |
| |
| // Add extra padding if it wasn't added to the TType base offset. |
| Asm->EmitULEB128(CallSiteTableLength, "Call site table length", SizeAlign); |
| |
| for (SmallVectorImpl<CallSiteEntry>::const_iterator |
| I = CallSites.begin(), E = CallSites.end(); I != E; ++I) { |
| const CallSiteEntry &S = *I; |
| |
| MCSymbol *EHFuncBeginSym = |
| Asm->GetTempSymbol("eh_func_begin", Asm->getFunctionNumber()); |
| |
| MCSymbol *BeginLabel = S.BeginLabel; |
| if (BeginLabel == 0) |
| BeginLabel = EHFuncBeginSym; |
| MCSymbol *EndLabel = S.EndLabel; |
| if (EndLabel == 0) |
| EndLabel = Asm->GetTempSymbol("eh_func_end", Asm->getFunctionNumber()); |
| |
| // Offset of the call site relative to the previous call site, counted in |
| // number of 16-byte bundles. The first call site is counted relative to |
| // the start of the procedure fragment. |
| Asm->OutStreamer.AddComment("Region start"); |
| Asm->EmitLabelDifference(BeginLabel, EHFuncBeginSym, 4); |
| |
| Asm->OutStreamer.AddComment("Region length"); |
| Asm->EmitLabelDifference(EndLabel, BeginLabel, 4); |
| |
| |
| // Offset of the landing pad, counted in 16-byte bundles relative to the |
| // @LPStart address. |
| Asm->OutStreamer.AddComment("Landing pad"); |
| if (!S.PadLabel) |
| Asm->OutStreamer.EmitIntValue(0, 4/*size*/, 0/*addrspace*/); |
| else |
| Asm->EmitLabelDifference(S.PadLabel, EHFuncBeginSym, 4); |
| |
| // Offset of the first associated action record, relative to the start of |
| // the action table. This value is biased by 1 (1 indicates the start of |
| // the action table), and 0 indicates that there are no actions. |
| Asm->EmitULEB128(S.Action, "Action"); |
| } |
| } |
| |
| // Emit the Action Table. |
| if (Actions.size() != 0) { |
| Asm->OutStreamer.AddComment("-- Action Record Table --"); |
| Asm->OutStreamer.AddBlankLine(); |
| } |
| |
| for (SmallVectorImpl<ActionEntry>::const_iterator |
| I = Actions.begin(), E = Actions.end(); I != E; ++I) { |
| const ActionEntry &Action = *I; |
| Asm->OutStreamer.AddComment("Action Record"); |
| Asm->OutStreamer.AddBlankLine(); |
| |
| // Type Filter |
| // |
| // Used by the runtime to match the type of the thrown exception to the |
| // type of the catch clauses or the types in the exception specification. |
| Asm->EmitSLEB128(Action.ValueForTypeID, " TypeInfo index"); |
| |
| // Action Record |
| // |
| // Self-relative signed displacement in bytes of the next action record, |
| // or 0 if there is no next action record. |
| Asm->EmitSLEB128(Action.NextAction, " Next action"); |
| } |
| |
| // Emit the Catch TypeInfos. |
| if (!TypeInfos.empty()) { |
| Asm->OutStreamer.AddComment("-- Catch TypeInfos --"); |
| Asm->OutStreamer.AddBlankLine(); |
| } |
| for (std::vector<const GlobalVariable *>::const_reverse_iterator |
| I = TypeInfos.rbegin(), E = TypeInfos.rend(); I != E; ++I) { |
| const GlobalVariable *GV = *I; |
| |
| Asm->OutStreamer.AddComment("TypeInfo"); |
| if (GV) |
| Asm->EmitReference(GV, TTypeEncoding); |
| else |
| Asm->OutStreamer.EmitIntValue(0,Asm->GetSizeOfEncodedValue(TTypeEncoding), |
| 0); |
| } |
| |
| // Emit the Exception Specifications. |
| if (!FilterIds.empty()) { |
| Asm->OutStreamer.AddComment("-- Filter IDs --"); |
| Asm->OutStreamer.AddBlankLine(); |
| } |
| for (std::vector<unsigned>::const_iterator |
| I = FilterIds.begin(), E = FilterIds.end(); I < E; ++I) { |
| unsigned TypeID = *I; |
| Asm->EmitULEB128(TypeID, TypeID != 0 ? "Exception specification" : 0); |
| } |
| |
| Asm->EmitAlignment(2); |
| } |
| |
| /// EndModule - Emit all exception information that should come after the |
| /// content. |
| void DwarfException::EndModule() { |
| if (Asm->MAI->getExceptionHandlingType() != ExceptionHandling::Dwarf) |
| 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 DwarfException::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 DwarfException::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())); |
| } |