diff options
Diffstat (limited to 'contrib/llvm/lib/CodeGen/AsmPrinter/DwarfException.cpp')
| -rw-r--r-- | contrib/llvm/lib/CodeGen/AsmPrinter/DwarfException.cpp | 960 |
1 files changed, 960 insertions, 0 deletions
diff --git a/contrib/llvm/lib/CodeGen/AsmPrinter/DwarfException.cpp b/contrib/llvm/lib/CodeGen/AsmPrinter/DwarfException.cpp new file mode 100644 index 0000000..c872840 --- /dev/null +++ b/contrib/llvm/lib/CodeGen/AsmPrinter/DwarfException.cpp @@ -0,0 +1,960 @@ +//===-- 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())); +} |
