| //===- CodeGen/AsmPrinter/EHStreamer.cpp - Exception Directive Streamer ---===// |
| // |
| // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| // See https://llvm.org/LICENSE.txt for license information. |
| // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // This file contains support for writing exception info into assembly files. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "EHStreamer.h" |
| #include "llvm/ADT/SmallVector.h" |
| #include "llvm/ADT/Twine.h" |
| #include "llvm/ADT/iterator_range.h" |
| #include "llvm/BinaryFormat/Dwarf.h" |
| #include "llvm/CodeGen/AsmPrinter.h" |
| #include "llvm/CodeGen/MachineFunction.h" |
| #include "llvm/CodeGen/MachineInstr.h" |
| #include "llvm/CodeGen/MachineOperand.h" |
| #include "llvm/IR/DataLayout.h" |
| #include "llvm/IR/Function.h" |
| #include "llvm/MC/MCAsmInfo.h" |
| #include "llvm/MC/MCContext.h" |
| #include "llvm/MC/MCStreamer.h" |
| #include "llvm/MC/MCSymbol.h" |
| #include "llvm/MC/MCTargetOptions.h" |
| #include "llvm/Support/Casting.h" |
| #include "llvm/Support/LEB128.h" |
| #include "llvm/Target/TargetLoweringObjectFile.h" |
| #include <algorithm> |
| #include <cassert> |
| #include <cstdint> |
| #include <vector> |
| |
| using namespace llvm; |
| |
| EHStreamer::EHStreamer(AsmPrinter *A) : Asm(A), MMI(Asm->MMI) {} |
| |
| EHStreamer::~EHStreamer() = default; |
| |
| /// How many leading type ids two landing pads have in common. |
| unsigned EHStreamer::sharedTypeIDs(const LandingPadInfo *L, |
| const LandingPadInfo *R) { |
| const std::vector<int> &LIds = L->TypeIds, &RIds = R->TypeIds; |
| return std::mismatch(LIds.begin(), LIds.end(), RIds.begin(), RIds.end()) |
| .first - |
| LIds.begin(); |
| } |
| |
| /// Compute the actions table and gather the first action index for each landing |
| /// pad site. |
| void EHStreamer::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 = Asm->MF->getFilterIds(); |
| SmallVector<int, 16> FilterOffsets; |
| FilterOffsets.reserve(FilterIds.size()); |
| int Offset = -1; |
| |
| for (unsigned FilterId : FilterIds) { |
| FilterOffsets.push_back(Offset); |
| Offset -= getULEB128Size(FilterId); |
| } |
| |
| FirstActions.reserve(LandingPads.size()); |
| |
| int FirstAction = 0; |
| unsigned SizeActions = 0; // Total size of all action entries for a function |
| const LandingPadInfo *PrevLPI = nullptr; |
| |
| for (const LandingPadInfo *LPI : LandingPads) { |
| const std::vector<int> &TypeIds = LPI->TypeIds; |
| unsigned NumShared = PrevLPI ? sharedTypeIDs(LPI, PrevLPI) : 0; |
| unsigned SizeSiteActions = 0; // Total size of all entries for a landingpad |
| |
| if (NumShared < TypeIds.size()) { |
| // Size of one action entry (typeid + next action) |
| unsigned SizeActionEntry = 0; |
| unsigned PrevAction = (unsigned)-1; |
| |
| if (NumShared) { |
| unsigned SizePrevIds = PrevLPI->TypeIds.size(); |
| assert(Actions.size()); |
| PrevAction = Actions.size() - 1; |
| SizeActionEntry = getSLEB128Size(Actions[PrevAction].NextAction) + |
| getSLEB128Size(Actions[PrevAction].ValueForTypeID); |
| |
| for (unsigned j = NumShared; j != SizePrevIds; ++j) { |
| assert(PrevAction != (unsigned)-1 && "PrevAction is invalid!"); |
| SizeActionEntry -= getSLEB128Size(Actions[PrevAction].ValueForTypeID); |
| SizeActionEntry += -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 = |
| isFilterEHSelector(TypeID) ? FilterOffsets[-1 - TypeID] : TypeID; |
| unsigned SizeTypeID = getSLEB128Size(ValueForTypeID); |
| |
| int NextAction = SizeActionEntry ? -(SizeActionEntry + SizeTypeID) : 0; |
| SizeActionEntry = SizeTypeID + getSLEB128Size(NextAction); |
| SizeSiteActions += SizeActionEntry; |
| |
| 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 - SizeActionEntry + 1; |
| } // else identical - re-use previous FirstAction |
| |
| // Information used when creating 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 `true' if this is a call to a function marked `nounwind'. Return |
| /// `false' otherwise. |
| bool EHStreamer::callToNoUnwindFunction(const MachineInstr *MI) { |
| assert(MI->isCall() && "This should be a call instruction!"); |
| |
| bool MarkedNoUnwind = false; |
| bool SawFunc = false; |
| |
| for (const MachineOperand &MO : MI->operands()) { |
| if (!MO.isGlobal()) continue; |
| |
| const Function *F = dyn_cast<Function>(MO.getGlobal()); |
| if (!F) 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; |
| } |
| |
| void EHStreamer::computePadMap( |
| const SmallVectorImpl<const LandingPadInfo *> &LandingPads, |
| RangeMapType &PadMap) { |
| // 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 so we can put them in the LSDA. |
| 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. 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. |
| /// |
| /// Call-sites are split into one or more call-site ranges associated with |
| /// different sections of the function. |
| /// |
| /// - Without -basic-block-sections, all call-sites are grouped into one |
| /// call-site-range corresponding to the function section. |
| /// |
| /// - With -basic-block-sections, one call-site range is created for each |
| /// section, with its FragmentBeginLabel and FragmentEndLabel respectively |
| // set to the beginning and ending of the corresponding section and its |
| // ExceptionLabel set to the exception symbol dedicated for this section. |
| // Later, one LSDA header will be emitted for each call-site range with its |
| // call-sites following. The action table and type info table will be |
| // shared across all ranges. |
| void EHStreamer::computeCallSiteTable( |
| SmallVectorImpl<CallSiteEntry> &CallSites, |
| SmallVectorImpl<CallSiteRange> &CallSiteRanges, |
| const SmallVectorImpl<const LandingPadInfo *> &LandingPads, |
| const SmallVectorImpl<unsigned> &FirstActions) { |
| RangeMapType PadMap; |
| computePadMap(LandingPads, PadMap); |
| |
| // The end label of the previous invoke or nounwind try-range. |
| MCSymbol *LastLabel = Asm->getFunctionBegin(); |
| |
| // 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; |
| |
| bool IsSJLJ = Asm->MAI->getExceptionHandlingType() == ExceptionHandling::SjLj; |
| |
| // Visit all instructions in order of address. |
| for (const auto &MBB : *Asm->MF) { |
| if (&MBB == &Asm->MF->front() || MBB.isBeginSection()) { |
| // We start a call-site range upon function entry and at the beginning of |
| // every basic block section. |
| CallSiteRanges.push_back( |
| {Asm->MBBSectionRanges[MBB.getSectionIDNum()].BeginLabel, |
| Asm->MBBSectionRanges[MBB.getSectionIDNum()].EndLabel, |
| Asm->getMBBExceptionSym(MBB), CallSites.size()}); |
| PreviousIsInvoke = false; |
| SawPotentiallyThrowing = false; |
| LastLabel = nullptr; |
| } |
| |
| if (MBB.isEHPad()) |
| CallSiteRanges.back().IsLPRange = true; |
| |
| for (const auto &MI : MBB) { |
| if (!MI.isEHLabel()) { |
| if (MI.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 and AIX 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->usesCFIForEH() || |
| Asm->MAI->getExceptionHandlingType() == ExceptionHandling::AIX)) { |
| CallSites.push_back({LastLabel, BeginLabel, nullptr, 0}); |
| 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, |
| FirstActions[P.PadIndex] |
| }; |
| |
| // Try to merge with the previous call-site. SJLJ doesn't do this |
| if (PreviousIsInvoke && !IsSJLJ) { |
| CallSiteEntry &Prev = CallSites.back(); |
| if (Site.LPad == Prev.LPad && Site.Action == Prev.Action) { |
| // Extend the range of the previous entry. |
| Prev.EndLabel = Site.EndLabel; |
| continue; |
| } |
| } |
| |
| // Otherwise, create a new call-site. |
| if (!IsSJLJ) |
| CallSites.push_back(Site); |
| else { |
| // SjLj EH must maintain the call sites in the order assigned |
| // to them by the SjLjPrepare pass. |
| unsigned SiteNo = Asm->MF->getCallSiteBeginLabel(BeginLabel); |
| if (CallSites.size() < SiteNo) |
| CallSites.resize(SiteNo); |
| CallSites[SiteNo - 1] = Site; |
| } |
| PreviousIsInvoke = true; |
| } |
| } |
| |
| // We end the call-site range upon function exit and at the end of every |
| // basic block section. |
| if (&MBB == &Asm->MF->back() || MBB.isEndSection()) { |
| // 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 && !IsSJLJ) { |
| CallSiteEntry Site = {LastLabel, CallSiteRanges.back().FragmentEndLabel, |
| nullptr, 0}; |
| CallSites.push_back(Site); |
| SawPotentiallyThrowing = false; |
| } |
| CallSiteRanges.back().CallSiteEndIdx = CallSites.size(); |
| } |
| } |
| } |
| |
| /// 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. |
| /// |
| /// Returns the starting symbol of an exception table. |
| MCSymbol *EHStreamer::emitExceptionTable() { |
| const MachineFunction *MF = Asm->MF; |
| const std::vector<const GlobalValue *> &TypeInfos = MF->getTypeInfos(); |
| const std::vector<unsigned> &FilterIds = MF->getFilterIds(); |
| const std::vector<LandingPadInfo> &PadInfos = MF->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 (const LandingPadInfo &LPI : PadInfos) |
| LandingPads.push_back(&LPI); |
| |
| // Order landing pads lexicographically by type id. |
| llvm::sort(LandingPads, [](const LandingPadInfo *L, const LandingPadInfo *R) { |
| return L->TypeIds < R->TypeIds; |
| }); |
| |
| // Compute the actions table and gather the first action index for each |
| // landing pad site. |
| SmallVector<ActionEntry, 32> Actions; |
| SmallVector<unsigned, 64> FirstActions; |
| computeActionsTable(LandingPads, Actions, FirstActions); |
| |
| // Compute the call-site table and call-site ranges. Normally, there is only |
| // one call-site-range which covers the whole funciton. With |
| // -basic-block-sections, there is one call-site-range per basic block |
| // section. |
| SmallVector<CallSiteEntry, 64> CallSites; |
| SmallVector<CallSiteRange, 4> CallSiteRanges; |
| computeCallSiteTable(CallSites, CallSiteRanges, LandingPads, FirstActions); |
| |
| bool IsSJLJ = Asm->MAI->getExceptionHandlingType() == ExceptionHandling::SjLj; |
| bool IsWasm = Asm->MAI->getExceptionHandlingType() == ExceptionHandling::Wasm; |
| bool HasLEB128Directives = Asm->MAI->hasLEB128Directives(); |
| unsigned CallSiteEncoding = |
| IsSJLJ ? static_cast<unsigned>(dwarf::DW_EH_PE_udata4) : |
| Asm->getObjFileLowering().getCallSiteEncoding(); |
| bool HaveTTData = !TypeInfos.empty() || !FilterIds.empty(); |
| |
| // Type infos. |
| MCSection *LSDASection = Asm->getObjFileLowering().getSectionForLSDA( |
| MF->getFunction(), *Asm->CurrentFnSym, Asm->TM); |
| unsigned TTypeEncoding; |
| |
| if (!HaveTTData) { |
| // If there is no TypeInfo, then we just explicitly say that we're omitting |
| // that bit. |
| TTypeEncoding = dwarf::DW_EH_PE_omit; |
| } 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(); |
| } |
| |
| // Begin the exception table. |
| // Sometimes we want not to emit the data into separate section (e.g. ARM |
| // EHABI). In this case LSDASection will be NULL. |
| if (LSDASection) |
| Asm->OutStreamer->SwitchSection(LSDASection); |
| Asm->emitAlignment(Align(4)); |
| |
| // Emit the LSDA. |
| MCSymbol *GCCETSym = |
| Asm->OutContext.getOrCreateSymbol(Twine("GCC_except_table")+ |
| Twine(Asm->getFunctionNumber())); |
| Asm->OutStreamer->emitLabel(GCCETSym); |
| MCSymbol *CstEndLabel = Asm->createTempSymbol( |
| CallSiteRanges.size() > 1 ? "action_table_base" : "cst_end"); |
| |
| MCSymbol *TTBaseLabel = nullptr; |
| if (HaveTTData) |
| TTBaseLabel = Asm->createTempSymbol("ttbase"); |
| |
| const bool VerboseAsm = Asm->OutStreamer->isVerboseAsm(); |
| |
| // Helper for emitting references (offsets) for type table and the end of the |
| // call-site table (which marks the beginning of the action table). |
| // * For Itanium, these references will be emitted for every callsite range. |
| // * For SJLJ and Wasm, they will be emitted only once in the LSDA header. |
| auto EmitTypeTableRefAndCallSiteTableEndRef = [&]() { |
| Asm->emitEncodingByte(TTypeEncoding, "@TType"); |
| if (HaveTTData) { |
| // N.B.: There is a dependency loop between the size of the TTBase uleb128 |
| // here and the amount of padding before the aligned type table. The |
| // assembler must sometimes pad this uleb128 or insert extra padding |
| // before the type table. See PR35809 or GNU as bug 4029. |
| MCSymbol *TTBaseRefLabel = Asm->createTempSymbol("ttbaseref"); |
| Asm->emitLabelDifferenceAsULEB128(TTBaseLabel, TTBaseRefLabel); |
| Asm->OutStreamer->emitLabel(TTBaseRefLabel); |
| } |
| |
| // The Action table follows the call-site table. So we emit the |
| // label difference from here (start of the call-site table for SJLJ and |
| // Wasm, and start of a call-site range for Itanium) to the end of the |
| // whole call-site table (end of the last call-site range for Itanium). |
| MCSymbol *CstBeginLabel = Asm->createTempSymbol("cst_begin"); |
| Asm->emitEncodingByte(CallSiteEncoding, "Call site"); |
| Asm->emitLabelDifferenceAsULEB128(CstEndLabel, CstBeginLabel); |
| Asm->OutStreamer->emitLabel(CstBeginLabel); |
| }; |
| |
| // An alternative path to EmitTypeTableRefAndCallSiteTableEndRef. |
| // For some platforms, the system assembler does not accept the form of |
| // `.uleb128 label2 - label1`. In those situations, we would need to calculate |
| // the size between label1 and label2 manually. |
| // In this case, we would need to calculate the LSDA size and the call |
| // site table size. |
| auto EmitTypeTableOffsetAndCallSiteTableOffset = [&]() { |
| assert(CallSiteEncoding == dwarf::DW_EH_PE_udata4 && !HasLEB128Directives && |
| "Targets supporting .uleb128 do not need to take this path."); |
| if (CallSiteRanges.size() > 1) |
| report_fatal_error( |
| "-fbasic-block-sections is not yet supported on " |
| "platforms that do not have general LEB128 directive support."); |
| |
| uint64_t CallSiteTableSize = 0; |
| const CallSiteRange &CSRange = CallSiteRanges.back(); |
| for (size_t CallSiteIdx = CSRange.CallSiteBeginIdx; |
| CallSiteIdx < CSRange.CallSiteEndIdx; ++CallSiteIdx) { |
| const CallSiteEntry &S = CallSites[CallSiteIdx]; |
| // Each call site entry consists of 3 udata4 fields (12 bytes) and |
| // 1 ULEB128 field. |
| CallSiteTableSize += 12 + getULEB128Size(S.Action); |
| assert(isUInt<32>(CallSiteTableSize) && "CallSiteTableSize overflows."); |
| } |
| |
| Asm->emitEncodingByte(TTypeEncoding, "@TType"); |
| if (HaveTTData) { |
| const unsigned ByteSizeOfCallSiteOffset = |
| getULEB128Size(CallSiteTableSize); |
| uint64_t ActionTableSize = 0; |
| for (const ActionEntry &Action : Actions) { |
| // Each action entry consists of two SLEB128 fields. |
| ActionTableSize += getSLEB128Size(Action.ValueForTypeID) + |
| getSLEB128Size(Action.NextAction); |
| assert(isUInt<32>(ActionTableSize) && "ActionTableSize overflows."); |
| } |
| |
| const unsigned TypeInfoSize = |
| Asm->GetSizeOfEncodedValue(TTypeEncoding) * MF->getTypeInfos().size(); |
| |
| const uint64_t LSDASizeBeforeAlign = |
| 1 // Call site encoding byte. |
| + ByteSizeOfCallSiteOffset // ULEB128 encoding of CallSiteTableSize. |
| + CallSiteTableSize // Call site table content. |
| + ActionTableSize; // Action table content. |
| |
| const uint64_t LSDASizeWithoutAlign = LSDASizeBeforeAlign + TypeInfoSize; |
| const unsigned ByteSizeOfLSDAWithoutAlign = |
| getULEB128Size(LSDASizeWithoutAlign); |
| const uint64_t DisplacementBeforeAlign = |
| 2 // LPStartEncoding and TypeTableEncoding. |
| + ByteSizeOfLSDAWithoutAlign + LSDASizeBeforeAlign; |
| |
| // The type info area starts with 4 byte alignment. |
| const unsigned NeedAlignVal = (4 - DisplacementBeforeAlign % 4) % 4; |
| uint64_t LSDASizeWithAlign = LSDASizeWithoutAlign + NeedAlignVal; |
| const unsigned ByteSizeOfLSDAWithAlign = |
| getULEB128Size(LSDASizeWithAlign); |
| |
| // The LSDASizeWithAlign could use 1 byte less padding for alignment |
| // when the data we use to represent the LSDA Size "needs" to be 1 byte |
| // larger than the one previously calculated without alignment. |
| if (ByteSizeOfLSDAWithAlign > ByteSizeOfLSDAWithoutAlign) |
| LSDASizeWithAlign -= 1; |
| |
| Asm->OutStreamer->emitULEB128IntValue(LSDASizeWithAlign, |
| ByteSizeOfLSDAWithAlign); |
| } |
| |
| Asm->emitEncodingByte(CallSiteEncoding, "Call site"); |
| Asm->OutStreamer->emitULEB128IntValue(CallSiteTableSize); |
| }; |
| |
| // SjLj / Wasm Exception handling |
| if (IsSJLJ || IsWasm) { |
| Asm->OutStreamer->emitLabel(Asm->getMBBExceptionSym(Asm->MF->front())); |
| |
| // emit the LSDA header. |
| Asm->emitEncodingByte(dwarf::DW_EH_PE_omit, "@LPStart"); |
| EmitTypeTableRefAndCallSiteTableEndRef(); |
| |
| unsigned idx = 0; |
| for (SmallVectorImpl<CallSiteEntry>::const_iterator |
| I = CallSites.begin(), E = CallSites.end(); I != E; ++I, ++idx) { |
| const CallSiteEntry &S = *I; |
| |
| // Index of the call site entry. |
| if (VerboseAsm) { |
| Asm->OutStreamer->AddComment(">> Call Site " + Twine(idx) + " <<"); |
| Asm->OutStreamer->AddComment(" On exception at call site "+Twine(idx)); |
| } |
| Asm->emitULEB128(idx); |
| |
| // 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. |
| if (VerboseAsm) { |
| if (S.Action == 0) |
| Asm->OutStreamer->AddComment(" Action: cleanup"); |
| else |
| Asm->OutStreamer->AddComment(" Action: " + |
| Twine((S.Action - 1) / 2 + 1)); |
| } |
| Asm->emitULEB128(S.Action); |
| } |
| Asm->OutStreamer->emitLabel(CstEndLabel); |
| } else { |
| // Itanium LSDA exception handling |
| |
| // 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. |
| |
| assert(CallSiteRanges.size() != 0 && "No call-site ranges!"); |
| |
| // There should be only one call-site range which includes all the landing |
| // pads. Find that call-site range here. |
| const CallSiteRange *LandingPadRange = nullptr; |
| for (const CallSiteRange &CSRange : CallSiteRanges) { |
| if (CSRange.IsLPRange) { |
| assert(LandingPadRange == nullptr && |
| "All landing pads must be in a single callsite range."); |
| LandingPadRange = &CSRange; |
| } |
| } |
| |
| // The call-site table is split into its call-site ranges, each being |
| // emitted as: |
| // [ LPStartEncoding | LPStart ] |
| // [ TypeTableEncoding | TypeTableOffset ] |
| // [ CallSiteEncoding | CallSiteTableEndOffset ] |
| // cst_begin -> { call-site entries contained in this range } |
| // |
| // and is followed by the next call-site range. |
| // |
| // For each call-site range, CallSiteTableEndOffset is computed as the |
| // difference between cst_begin of that range and the last call-site-table's |
| // end label. This offset is used to find the action table. |
| |
| unsigned Entry = 0; |
| for (const CallSiteRange &CSRange : CallSiteRanges) { |
| if (CSRange.CallSiteBeginIdx != 0) { |
| // Align the call-site range for all ranges except the first. The |
| // first range is already aligned due to the exception table alignment. |
| Asm->emitAlignment(Align(4)); |
| } |
| Asm->OutStreamer->emitLabel(CSRange.ExceptionLabel); |
| |
| // Emit the LSDA header. |
| // If only one call-site range exists, LPStart is omitted as it is the |
| // same as the function entry. |
| if (CallSiteRanges.size() == 1) { |
| Asm->emitEncodingByte(dwarf::DW_EH_PE_omit, "@LPStart"); |
| } else if (!Asm->isPositionIndependent()) { |
| // For more than one call-site ranges, LPStart must be explicitly |
| // specified. |
| // For non-PIC we can simply use the absolute value. |
| Asm->emitEncodingByte(dwarf::DW_EH_PE_absptr, "@LPStart"); |
| Asm->OutStreamer->emitSymbolValue(LandingPadRange->FragmentBeginLabel, |
| Asm->MAI->getCodePointerSize()); |
| } else { |
| // For PIC mode, we Emit a PC-relative address for LPStart. |
| Asm->emitEncodingByte(dwarf::DW_EH_PE_pcrel, "@LPStart"); |
| MCContext &Context = Asm->OutStreamer->getContext(); |
| MCSymbol *Dot = Context.createTempSymbol(); |
| Asm->OutStreamer->emitLabel(Dot); |
| Asm->OutStreamer->emitValue( |
| MCBinaryExpr::createSub( |
| MCSymbolRefExpr::create(LandingPadRange->FragmentBeginLabel, |
| Context), |
| MCSymbolRefExpr::create(Dot, Context), Context), |
| Asm->MAI->getCodePointerSize()); |
| } |
| |
| if (HasLEB128Directives) |
| EmitTypeTableRefAndCallSiteTableEndRef(); |
| else |
| EmitTypeTableOffsetAndCallSiteTableOffset(); |
| |
| for (size_t CallSiteIdx = CSRange.CallSiteBeginIdx; |
| CallSiteIdx != CSRange.CallSiteEndIdx; ++CallSiteIdx) { |
| const CallSiteEntry &S = CallSites[CallSiteIdx]; |
| |
| MCSymbol *EHFuncBeginSym = CSRange.FragmentBeginLabel; |
| MCSymbol *EHFuncEndSym = CSRange.FragmentEndLabel; |
| |
| MCSymbol *BeginLabel = S.BeginLabel; |
| if (!BeginLabel) |
| BeginLabel = EHFuncBeginSym; |
| MCSymbol *EndLabel = S.EndLabel; |
| if (!EndLabel) |
| EndLabel = EHFuncEndSym; |
| |
| // Offset of the call site relative to the start of the procedure. |
| if (VerboseAsm) |
| Asm->OutStreamer->AddComment(">> Call Site " + Twine(++Entry) + |
| " <<"); |
| Asm->emitCallSiteOffset(BeginLabel, EHFuncBeginSym, CallSiteEncoding); |
| if (VerboseAsm) |
| Asm->OutStreamer->AddComment(Twine(" Call between ") + |
| BeginLabel->getName() + " and " + |
| EndLabel->getName()); |
| Asm->emitCallSiteOffset(EndLabel, BeginLabel, CallSiteEncoding); |
| |
| // Offset of the landing pad relative to the start of the landing pad |
| // fragment. |
| if (!S.LPad) { |
| if (VerboseAsm) |
| Asm->OutStreamer->AddComment(" has no landing pad"); |
| Asm->emitCallSiteValue(0, CallSiteEncoding); |
| } else { |
| if (VerboseAsm) |
| Asm->OutStreamer->AddComment(Twine(" jumps to ") + |
| S.LPad->LandingPadLabel->getName()); |
| Asm->emitCallSiteOffset(S.LPad->LandingPadLabel, |
| LandingPadRange->FragmentBeginLabel, |
| CallSiteEncoding); |
| } |
| |
| // 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. |
| if (VerboseAsm) { |
| if (S.Action == 0) |
| Asm->OutStreamer->AddComment(" On action: cleanup"); |
| else |
| Asm->OutStreamer->AddComment(" On action: " + |
| Twine((S.Action - 1) / 2 + 1)); |
| } |
| Asm->emitULEB128(S.Action); |
| } |
| } |
| Asm->OutStreamer->emitLabel(CstEndLabel); |
| } |
| |
| // Emit the Action Table. |
| int Entry = 0; |
| for (const ActionEntry &Action : Actions) { |
| if (VerboseAsm) { |
| // Emit comments that decode the action table. |
| Asm->OutStreamer->AddComment(">> Action Record " + Twine(++Entry) + " <<"); |
| } |
| |
| // 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. |
| if (VerboseAsm) { |
| if (Action.ValueForTypeID > 0) |
| Asm->OutStreamer->AddComment(" Catch TypeInfo " + |
| Twine(Action.ValueForTypeID)); |
| else if (Action.ValueForTypeID < 0) |
| Asm->OutStreamer->AddComment(" Filter TypeInfo " + |
| Twine(Action.ValueForTypeID)); |
| else |
| Asm->OutStreamer->AddComment(" Cleanup"); |
| } |
| Asm->emitSLEB128(Action.ValueForTypeID); |
| |
| // Action Record |
| if (VerboseAsm) { |
| if (Action.Previous == unsigned(-1)) { |
| Asm->OutStreamer->AddComment(" No further actions"); |
| } else { |
| Asm->OutStreamer->AddComment(" Continue to action " + |
| Twine(Action.Previous + 1)); |
| } |
| } |
| Asm->emitSLEB128(Action.NextAction); |
| } |
| |
| if (HaveTTData) { |
| Asm->emitAlignment(Align(4)); |
| emitTypeInfos(TTypeEncoding, TTBaseLabel); |
| } |
| |
| Asm->emitAlignment(Align(4)); |
| return GCCETSym; |
| } |
| |
| void EHStreamer::emitTypeInfos(unsigned TTypeEncoding, MCSymbol *TTBaseLabel) { |
| const MachineFunction *MF = Asm->MF; |
| const std::vector<const GlobalValue *> &TypeInfos = MF->getTypeInfos(); |
| const std::vector<unsigned> &FilterIds = MF->getFilterIds(); |
| |
| const bool VerboseAsm = Asm->OutStreamer->isVerboseAsm(); |
| |
| int Entry = 0; |
| // Emit the Catch TypeInfos. |
| if (VerboseAsm && !TypeInfos.empty()) { |
| Asm->OutStreamer->AddComment(">> Catch TypeInfos <<"); |
| Asm->OutStreamer->AddBlankLine(); |
| Entry = TypeInfos.size(); |
| } |
| |
| for (const GlobalValue *GV : llvm::reverse(TypeInfos)) { |
| if (VerboseAsm) |
| Asm->OutStreamer->AddComment("TypeInfo " + Twine(Entry--)); |
| Asm->emitTTypeReference(GV, TTypeEncoding); |
| } |
| |
| Asm->OutStreamer->emitLabel(TTBaseLabel); |
| |
| // Emit the Exception Specifications. |
| if (VerboseAsm && !FilterIds.empty()) { |
| Asm->OutStreamer->AddComment(">> Filter TypeInfos <<"); |
| Asm->OutStreamer->AddBlankLine(); |
| Entry = 0; |
| } |
| for (std::vector<unsigned>::const_iterator |
| I = FilterIds.begin(), E = FilterIds.end(); I < E; ++I) { |
| unsigned TypeID = *I; |
| if (VerboseAsm) { |
| --Entry; |
| if (isFilterEHSelector(TypeID)) |
| Asm->OutStreamer->AddComment("FilterInfo " + Twine(Entry)); |
| } |
| |
| Asm->emitULEB128(TypeID); |
| } |
| } |
