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;
}
}
}
/// 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->getDataLayout().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.
// 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(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;
}
bool VerboseAsm = Asm->OutStreamer.isVerboseAsm();
// 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.
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);
}
} else {
// DWARF Exception handling
assert(Asm->MAI->isExceptionHandlingDwarf());
// 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);
unsigned Entry = 0;
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.
if (VerboseAsm)
Asm->OutStreamer.AddComment(">> Call Site " + Twine(++Entry) + " <<");
Asm->EmitLabelDifference(BeginLabel, EHFuncBeginSym, 4);
if (VerboseAsm)
Asm->OutStreamer.AddComment(Twine(" Call between ") +
BeginLabel->getName() + " and " +
EndLabel->getName());
Asm->EmitLabelDifference(EndLabel, BeginLabel, 4);
// Offset of the landing pad, counted in 16-byte bundles relative to the
// @LPStart address.
if (!S.PadLabel) {
if (VerboseAsm)
Asm->OutStreamer.AddComment(" has no landing pad");
Asm->OutStreamer.EmitIntValue(0, 4/*size*/, 0/*addrspace*/);
} else {
if (VerboseAsm)
Asm->OutStreamer.AddComment(Twine(" jumps to ") +
S.PadLabel->getName());
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.
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);
}
}
// Emit the Action Table.
int Entry = 0;
for (SmallVectorImpl<ActionEntry>::const_iterator
I = Actions.begin(), E = Actions.end(); I != E; ++I) {
const ActionEntry &Action = *I;
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
//
// Self-relative signed displacement in bytes of the next action record,
// or 0 if there is no next action record.
if (VerboseAsm) {
if (Action.NextAction == 0) {
Asm->OutStreamer.AddComment(" No further actions");
} else {
unsigned NextAction = Entry + (Action.NextAction + 1) / 2;
Asm->OutStreamer.AddComment(" Continue to action "+Twine(NextAction));
}
}
Asm->EmitSLEB128(Action.NextAction);
}
// Emit the Catch TypeInfos.
if (VerboseAsm && !TypeInfos.empty()) {
Asm->OutStreamer.AddComment(">> Catch TypeInfos <<");
Asm->OutStreamer.AddBlankLine();
Entry = TypeInfos.size();
}
for (std::vector<const GlobalVariable *>::const_reverse_iterator
I = TypeInfos.rbegin(), E = TypeInfos.rend(); I != E; ++I) {
const GlobalVariable *GV = *I;
if (VerboseAsm)
Asm->OutStreamer.AddComment("TypeInfo " + Twine(Entry--));
if (GV)
Asm->EmitReference(GV, TTypeEncoding);
else
Asm->OutStreamer.EmitIntValue(0,Asm->GetSizeOfEncodedValue(TTypeEncoding),
0);
}
// 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 (TypeID != 0)
Asm->OutStreamer.AddComment("FilterInfo " + Twine(Entry));
}
Asm->EmitULEB128(TypeID);
}
Asm->EmitAlignment(2);
}
/// 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->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->isExceptionHandlingDwarf()) {
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->isExceptionHandlingDwarf()) {
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->isExceptionHandlingDwarf())
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->isExceptionHandlingDwarf()) {
CallSiteEntry Site = { LastLabel, 0, 0, 0 };
CallSites.push_back(Site);
}
}
void WinException::extendIP2StateTable(const MachineFunction *MF,
const Function *ParentF,
WinEHFuncInfo &FuncInfo) {
const Function *F = MF->getFunction();
// The Itanium LSDA table sorts similar landing pads together to simplify the
// actions table, but we don't need that.
SmallVector<const LandingPadInfo *, 64> LandingPads;
const std::vector<LandingPadInfo> &PadInfos = MMI->getLandingPads();
LandingPads.reserve(PadInfos.size());
for (const auto &LP : PadInfos)
LandingPads.push_back(&LP);
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;
int LastEHState = -2;
// The parent function and the catch handlers contribute to the 'ip2state'
// table.
// Include ip2state entries for the beginning of the main function and
// for catch handler functions.
if (F == ParentF) {
FuncInfo.IPToStateList.push_back(std::make_pair(LastLabel, -1));
LastEHState = -1;
} else if (FuncInfo.HandlerBaseState.count(F)) {
FuncInfo.IPToStateList.push_back(
std::make_pair(LastLabel, FuncInfo.HandlerBaseState[F]));
LastEHState = FuncInfo.HandlerBaseState[F];
}
for (const auto &MBB : *MF) {
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!");
// FIXME: Should this be using FuncInfo.HandlerBaseState?
if (SawPotentiallyThrowing && LastEHState != -1) {
FuncInfo.IPToStateList.push_back(std::make_pair(LastLabel, -1));
SawPotentiallyThrowing = false;
LastEHState = -1;
}
if (LandingPad->WinEHState != LastEHState)
FuncInfo.IPToStateList.push_back(
std::make_pair(BeginLabel, LandingPad->WinEHState));
LastEHState = LandingPad->WinEHState;
LastLabel = LandingPad->EndLabels[P.RangeIndex];
}
}
}
void Win64Exception::emitCXXFrameHandler3Table(const MachineFunction *MF) {
const Function *F = MF->getFunction();
const Function *ParentF = MMI->getWinEHParent(F);
auto &OS = *Asm->OutStreamer;
WinEHFuncInfo &FuncInfo = MMI->getWinEHFuncInfo(ParentF);
StringRef ParentLinkageName =
GlobalValue::getRealLinkageName(ParentF->getName());
MCSymbol *FuncInfoXData =
Asm->OutContext.getOrCreateSymbol(Twine("$cppxdata$", ParentLinkageName));
OS.EmitValue(createImageRel32(FuncInfoXData), 4);
// The Itanium LSDA table sorts similar landing pads together to simplify the
// actions table, but we don't need that.
SmallVector<const LandingPadInfo *, 64> LandingPads;
const std::vector<LandingPadInfo> &PadInfos = MMI->getLandingPads();
LandingPads.reserve(PadInfos.size());
for (const auto &LP : PadInfos)
LandingPads.push_back(&LP);
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;
int LastEHState = -2;
// The parent function and the catch handlers contribute to the 'ip2state'
// table.
// Include ip2state entries for the beginning of the main function and
// for catch handler functions.
if (F == ParentF) {
FuncInfo.IPToStateList.push_back(std::make_pair(LastLabel, -1));
LastEHState = -1;
} else if (FuncInfo.HandlerBaseState.count(F)) {
FuncInfo.IPToStateList.push_back(std::make_pair(LastLabel,
FuncInfo.HandlerBaseState[F]));
LastEHState = FuncInfo.HandlerBaseState[F];
}
for (const auto &MBB : *MF) {
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!");
// FIXME: Should this be using FuncInfo.HandlerBaseState?
if (SawPotentiallyThrowing && LastEHState != -1) {
FuncInfo.IPToStateList.push_back(std::make_pair(LastLabel, -1));
SawPotentiallyThrowing = false;
LastEHState = -1;
}
if (LandingPad->WinEHState != LastEHState)
FuncInfo.IPToStateList.push_back(
std::make_pair(BeginLabel, LandingPad->WinEHState));
LastEHState = LandingPad->WinEHState;
LastLabel = LandingPad->EndLabels[P.RangeIndex];
}
}
// Defer emission until we've visited the parent function and all the catch
// handlers. Cleanups don't contribute to the ip2state table yet, so don't
// count them.
if (ParentF != F && !FuncInfo.CatchHandlerMaxState.count(F))
return;
++FuncInfo.NumIPToStateFuncsVisited;
if (FuncInfo.NumIPToStateFuncsVisited != FuncInfo.CatchHandlerMaxState.size())
return;
MCSymbol *UnwindMapXData = nullptr;
MCSymbol *TryBlockMapXData = nullptr;
MCSymbol *IPToStateXData = nullptr;
if (!FuncInfo.UnwindMap.empty())
UnwindMapXData = Asm->OutContext.getOrCreateSymbol(
Twine("$stateUnwindMap$", ParentLinkageName));
if (!FuncInfo.TryBlockMap.empty())
TryBlockMapXData = Asm->OutContext.getOrCreateSymbol(
Twine("$tryMap$", ParentLinkageName));
if (!FuncInfo.IPToStateList.empty())
IPToStateXData = Asm->OutContext.getOrCreateSymbol(
Twine("$ip2state$", ParentLinkageName));
// FuncInfo {
// uint32_t MagicNumber
// int32_t MaxState;
// UnwindMapEntry *UnwindMap;
// uint32_t NumTryBlocks;
// TryBlockMapEntry *TryBlockMap;
// uint32_t IPMapEntries;
// IPToStateMapEntry *IPToStateMap;
// uint32_t UnwindHelp; // (x64/ARM only)
// ESTypeList *ESTypeList;
// int32_t EHFlags;
// }
// EHFlags & 1 -> Synchronous exceptions only, no async exceptions.
// EHFlags & 2 -> ???
// EHFlags & 4 -> The function is noexcept(true), unwinding can't continue.
OS.EmitLabel(FuncInfoXData);
OS.EmitIntValue(0x19930522, 4); // MagicNumber
OS.EmitIntValue(FuncInfo.UnwindMap.size(), 4); // MaxState
OS.EmitValue(createImageRel32(UnwindMapXData), 4); // UnwindMap
OS.EmitIntValue(FuncInfo.TryBlockMap.size(), 4); // NumTryBlocks
OS.EmitValue(createImageRel32(TryBlockMapXData), 4); // TryBlockMap
OS.EmitIntValue(FuncInfo.IPToStateList.size(), 4); // IPMapEntries
OS.EmitValue(createImageRel32(IPToStateXData), 4); // IPToStateMap
OS.EmitIntValue(FuncInfo.UnwindHelpFrameOffset, 4); // UnwindHelp
OS.EmitIntValue(0, 4); // ESTypeList
OS.EmitIntValue(1, 4); // EHFlags
// UnwindMapEntry {
// int32_t ToState;
// void (*Action)();
// };
if (UnwindMapXData) {
OS.EmitLabel(UnwindMapXData);
for (const WinEHUnwindMapEntry &UME : FuncInfo.UnwindMap) {
OS.EmitIntValue(UME.ToState, 4); // ToState
OS.EmitValue(createImageRel32(UME.Cleanup), 4); // Action
}
}
// TryBlockMap {
// int32_t TryLow;
// int32_t TryHigh;
// int32_t CatchHigh;
// int32_t NumCatches;
// HandlerType *HandlerArray;
// };
if (TryBlockMapXData) {
OS.EmitLabel(TryBlockMapXData);
SmallVector<MCSymbol *, 1> HandlerMaps;
for (size_t I = 0, E = FuncInfo.TryBlockMap.size(); I != E; ++I) {
WinEHTryBlockMapEntry &TBME = FuncInfo.TryBlockMap[I];
MCSymbol *HandlerMapXData = nullptr;
if (!TBME.HandlerArray.empty())
HandlerMapXData =
Asm->OutContext.getOrCreateSymbol(Twine("$handlerMap$")
.concat(Twine(I))
.concat("$")
.concat(ParentLinkageName));
HandlerMaps.push_back(HandlerMapXData);
int CatchHigh = -1;
for (WinEHHandlerType &HT : TBME.HandlerArray)
CatchHigh =
std::max(CatchHigh, FuncInfo.CatchHandlerMaxState[HT.Handler]);
assert(TBME.TryLow <= TBME.TryHigh);
OS.EmitIntValue(TBME.TryLow, 4); // TryLow
OS.EmitIntValue(TBME.TryHigh, 4); // TryHigh
OS.EmitIntValue(CatchHigh, 4); // CatchHigh
OS.EmitIntValue(TBME.HandlerArray.size(), 4); // NumCatches
OS.EmitValue(createImageRel32(HandlerMapXData), 4); // HandlerArray
}
for (size_t I = 0, E = FuncInfo.TryBlockMap.size(); I != E; ++I) {
WinEHTryBlockMapEntry &TBME = FuncInfo.TryBlockMap[I];
MCSymbol *HandlerMapXData = HandlerMaps[I];
if (!HandlerMapXData)
continue;
// HandlerType {
// int32_t Adjectives;
// TypeDescriptor *Type;
// int32_t CatchObjOffset;
// void (*Handler)();
// int32_t ParentFrameOffset; // x64 only
// };
OS.EmitLabel(HandlerMapXData);
for (const WinEHHandlerType &HT : TBME.HandlerArray) {
MCSymbol *ParentFrameOffset =
Asm->OutContext.getOrCreateParentFrameOffsetSymbol(
GlobalValue::getRealLinkageName(HT.Handler->getName()));
const MCSymbolRefExpr *ParentFrameOffsetRef = MCSymbolRefExpr::Create(
ParentFrameOffset, MCSymbolRefExpr::VK_None, Asm->OutContext);
// Get the frame escape label with the offset of the catch object. If
// the index is -1, then there is no catch object, and we should emit an
// offset of zero, indicating that no copy will occur.
const MCExpr *FrameAllocOffsetRef = nullptr;
if (HT.CatchObjRecoverIdx >= 0) {
MCSymbol *FrameAllocOffset =
Asm->OutContext.getOrCreateFrameAllocSymbol(
GlobalValue::getRealLinkageName(ParentF->getName()),
HT.CatchObjRecoverIdx);
FrameAllocOffsetRef = MCSymbolRefExpr::Create(
FrameAllocOffset, MCSymbolRefExpr::VK_None, Asm->OutContext);
} else {
FrameAllocOffsetRef = MCConstantExpr::Create(0, Asm->OutContext);
}
OS.EmitIntValue(HT.Adjectives, 4); // Adjectives
OS.EmitValue(createImageRel32(HT.TypeDescriptor), 4); // Type
OS.EmitValue(FrameAllocOffsetRef, 4); // CatchObjOffset
OS.EmitValue(createImageRel32(HT.Handler), 4); // Handler
OS.EmitValue(ParentFrameOffsetRef, 4); // ParentFrameOffset
}
}
}
// IPToStateMapEntry {
// void *IP;
// int32_t State;
// };
if (IPToStateXData) {
OS.EmitLabel(IPToStateXData);
for (auto &IPStatePair : FuncInfo.IPToStateList) {
OS.EmitValue(createImageRel32(IPStatePair.first), 4); // IP
OS.EmitIntValue(IPStatePair.second, 4); // State
}
}
}
unsigned char* JITDwarfEmitter::EmitExceptionTable(MachineFunction* MF,
unsigned char* StartFunction,
unsigned char* EndFunction) const {
assert(MMI && "MachineModuleInfo not registered!");
// Map all labels and get rid of any dead landing pads.
MMI->TidyLandingPads(JCE->getLabelLocations());
const std::vector<const GlobalVariable *> &TypeInfos = MMI->getTypeInfos();
const std::vector<unsigned> &FilterIds = MMI->getFilterIds();
const std::vector<LandingPadInfo> &PadInfos = MMI->getLandingPads();
if (PadInfos.empty()) return 0;
// 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);
// 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].
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);
}
// Compute the actions table and gather the first action index for each
// landing pad site.
SmallVector<ActionEntry, 32> Actions;
SmallVector<unsigned, 64> FirstActions;
FirstActions.reserve(LandingPads.size());
int FirstAction = 0;
unsigned SizeActions = 0;
for (unsigned i = 0, N = LandingPads.size(); i != N; ++i) {
const LandingPadInfo *LP = LandingPads[i];
const std::vector<int> &TypeIds = LP->TypeIds;
const unsigned NumShared = i ? SharedTypeIds(LP, LandingPads[i-1]) : 0;
unsigned SizeSiteActions = 0;
if (NumShared < TypeIds.size()) {
unsigned SizeAction = 0;
ActionEntry *PrevAction = 0;
if (NumShared) {
const unsigned SizePrevIds = LandingPads[i-1]->TypeIds.size();
assert(Actions.size());
PrevAction = &Actions.back();
SizeAction = MCAsmInfo::getSLEB128Size(PrevAction->NextAction) +
MCAsmInfo::getSLEB128Size(PrevAction->ValueForTypeID);
for (unsigned j = NumShared; j != SizePrevIds; ++j) {
SizeAction -= MCAsmInfo::getSLEB128Size(PrevAction->ValueForTypeID);
SizeAction += -PrevAction->NextAction;
PrevAction = PrevAction->Previous;
}
}
// Compute the actions.
for (unsigned I = NumShared, M = TypeIds.size(); I != M; ++I) {
int TypeID = TypeIds[I];
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.back();
}
// Record the first action of the landing pad site.
FirstAction = SizeActions + SizeSiteActions - SizeAction + 1;
} // else identical - re-use previous FirstAction
FirstActions.push_back(FirstAction);
// Compute this sites contribution to size.
SizeActions += SizeSiteActions;
}
// Compute the call-site table. Entries must be ordered by address.
SmallVector<CallSiteEntry, 64> CallSites;
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;
}
}
bool MayThrow = false;
MCSymbol *LastLabel = 0;
for (MachineFunction::const_iterator I = MF->begin(), E = MF->end();
I != E; ++I) {
for (MachineBasicBlock::const_iterator MI = I->begin(), E = I->end();
MI != E; ++MI) {
if (!MI->isLabel()) {
MayThrow |= MI->getDesc().isCall();
continue;
}
MCSymbol *BeginLabel = MI->getOperand(0).getMCSymbol();
assert(BeginLabel && "Invalid label!");
if (BeginLabel == LastLabel)
MayThrow = false;
RangeMapType::iterator L = PadMap.find(BeginLabel);
if (L == PadMap.end())
continue;
PadRange P = L->second;
const LandingPadInfo *LandingPad = LandingPads[P.PadIndex];
assert(BeginLabel == LandingPad->BeginLabels[P.RangeIndex] &&
"Inconsistent landing pad map!");
// 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 (MayThrow) {
CallSiteEntry Site = {LastLabel, BeginLabel, 0, 0};
CallSites.push_back(Site);
}
LastLabel = LandingPad->EndLabels[P.RangeIndex];
CallSiteEntry Site = {BeginLabel, LastLabel,
LandingPad->LandingPadLabel, FirstActions[P.PadIndex]};
assert(Site.BeginLabel && Site.EndLabel && Site.PadLabel &&
"Invalid landing pad!");
// Try to merge with the previous call-site.
if (CallSites.size()) {
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.
CallSites.push_back(Site);
}
}
// 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 (MayThrow) {
CallSiteEntry Site = {LastLabel, 0, 0, 0};
CallSites.push_back(Site);
}
// Final tallies.
unsigned SizeSites = CallSites.size() * (sizeof(int32_t) + // Site start.
sizeof(int32_t) + // Site length.
sizeof(int32_t)); // Landing pad.
for (unsigned i = 0, e = CallSites.size(); i < e; ++i)
SizeSites += MCAsmInfo::getULEB128Size(CallSites[i].Action);
unsigned SizeTypes = TypeInfos.size() * TD->getPointerSize();
unsigned TypeOffset = sizeof(int8_t) + // Call site format
// Call-site table length
MCAsmInfo::getULEB128Size(SizeSites) +
SizeSites + SizeActions + SizeTypes;
// Begin the exception table.
JCE->emitAlignmentWithFill(4, 0);
// Asm->EOL("Padding");
unsigned char* DwarfExceptionTable = (unsigned char*)JCE->getCurrentPCValue();
// Emit the header.
JCE->emitByte(dwarf::DW_EH_PE_omit);
// Asm->EOL("LPStart format (DW_EH_PE_omit)");
JCE->emitByte(dwarf::DW_EH_PE_absptr);
// Asm->EOL("TType format (DW_EH_PE_absptr)");
JCE->emitULEB128Bytes(TypeOffset);
// Asm->EOL("TType base offset");
JCE->emitByte(dwarf::DW_EH_PE_udata4);
// Asm->EOL("Call site format (DW_EH_PE_udata4)");
JCE->emitULEB128Bytes(SizeSites);
// Asm->EOL("Call-site table length");
// Emit the landing pad site information.
for (unsigned i = 0; i < CallSites.size(); ++i) {
CallSiteEntry &S = CallSites[i];
intptr_t BeginLabelPtr = 0;
intptr_t EndLabelPtr = 0;
if (!S.BeginLabel) {
BeginLabelPtr = (intptr_t)StartFunction;
JCE->emitInt32(0);
} else {
BeginLabelPtr = JCE->getLabelAddress(S.BeginLabel);
JCE->emitInt32(BeginLabelPtr - (intptr_t)StartFunction);
}
// Asm->EOL("Region start");
if (!S.EndLabel)
EndLabelPtr = (intptr_t)EndFunction;
else
EndLabelPtr = JCE->getLabelAddress(S.EndLabel);
JCE->emitInt32(EndLabelPtr - BeginLabelPtr);
//Asm->EOL("Region length");
if (!S.PadLabel) {
JCE->emitInt32(0);
} else {
unsigned PadLabelPtr = JCE->getLabelAddress(S.PadLabel);
JCE->emitInt32(PadLabelPtr - (intptr_t)StartFunction);
}
// Asm->EOL("Landing pad");
JCE->emitULEB128Bytes(S.Action);
// Asm->EOL("Action");
}
// Emit the actions.
for (unsigned I = 0, N = Actions.size(); I != N; ++I) {
ActionEntry &Action = Actions[I];
JCE->emitSLEB128Bytes(Action.ValueForTypeID);
//Asm->EOL("TypeInfo index");
JCE->emitSLEB128Bytes(Action.NextAction);
//Asm->EOL("Next action");
}
// Emit the type ids.
for (unsigned M = TypeInfos.size(); M; --M) {
const GlobalVariable *GV = TypeInfos[M - 1];
if (GV) {
if (TD->getPointerSize() == sizeof(int32_t))
JCE->emitInt32((intptr_t)Jit.getOrEmitGlobalVariable(GV));
else
JCE->emitInt64((intptr_t)Jit.getOrEmitGlobalVariable(GV));
} else {
if (TD->getPointerSize() == sizeof(int32_t))
JCE->emitInt32(0);
else
JCE->emitInt64(0);
}
// Asm->EOL("TypeInfo");
}
// Emit the filter typeids.
for (unsigned j = 0, M = FilterIds.size(); j < M; ++j) {
unsigned TypeID = FilterIds[j];
JCE->emitULEB128Bytes(TypeID);
//Asm->EOL("Filter TypeInfo index");
}
JCE->emitAlignmentWithFill(4, 0);
return DwarfExceptionTable;
}
/// 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 EHStreamer::
computeCallSiteTable(SmallVectorImpl<CallSiteEntry> &CallSites,
const SmallVectorImpl<const LandingPadInfo *> &LandingPads,
const SmallVectorImpl<unsigned> &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 so we can put them in the LSDA.
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;
}
}
// The end label of the previous invoke or nounwind try-range.
MCSymbol *LastLabel = nullptr;
// 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) {
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 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 && !IsSJLJ) {
CallSiteEntry Site = { LastLabel, BeginLabel, nullptr, 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 && !IsSJLJ) {
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 (!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 = 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 && !IsSJLJ) {
CallSiteEntry Site = { LastLabel, nullptr, nullptr, 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 the 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 reversed indexed base 1.
void DwarfException::EmitExceptionTable() {
const std::vector<GlobalVariable *> &TypeInfos = MMI->getTypeInfos();
const std::vector<unsigned> &FilterIds = MMI->getFilterIds();
const std::vector<LandingPadInfo> &PadInfos = MMI->getLandingPads();
if (PadInfos.empty()) return;
// 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) {
unsigned 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.
const unsigned SiteStartSize = sizeof(int32_t); // DW_EH_PE_udata4
const unsigned SiteLengthSize = sizeof(int32_t); // DW_EH_PE_udata4
const unsigned LandingPadSize = sizeof(int32_t); // DW_EH_PE_udata4
unsigned SizeSites;
bool HaveTTData = (TAI->getExceptionHandlingType() == ExceptionHandling::SjLj)
? (!TypeInfos.empty() || !FilterIds.empty()) : true;
if (TAI->getExceptionHandlingType() == ExceptionHandling::SjLj) {
SizeSites = 0;
} else
SizeSites = CallSites.size() *
(SiteStartSize + SiteLengthSize + LandingPadSize);
for (unsigned i = 0, e = CallSites.size(); i < e; ++i) {
SizeSites += TargetAsmInfo::getULEB128Size(CallSites[i].Action);
if (TAI->getExceptionHandlingType() == ExceptionHandling::SjLj)
SizeSites += TargetAsmInfo::getULEB128Size(i);
}
// Type infos.
const unsigned TypeInfoSize = TD->getPointerSize(); // DW_EH_PE_absptr
unsigned SizeTypes = TypeInfos.size() * TypeInfoSize;
unsigned TypeOffset = sizeof(int8_t) + // Call site format
TargetAsmInfo::getULEB128Size(SizeSites) + // Call-site table length
SizeSites + SizeActions + SizeTypes;
unsigned TotalSize = sizeof(int8_t) + // LPStart format
sizeof(int8_t) + // TType format
(HaveTTData ?
TargetAsmInfo::getULEB128Size(TypeOffset) : 0) + // TType base offset
TypeOffset;
unsigned SizeAlign = (4 - TotalSize) & 3;
// Begin the exception table.
const MCSection *LSDASection = Asm->getObjFileLowering().getLSDASection();
Asm->OutStreamer.SwitchSection(LSDASection);
Asm->EmitAlignment(2, 0, 0, false);
O << "GCC_except_table" << SubprogramCount << ":\n";
for (unsigned i = 0; i != SizeAlign; ++i) {
Asm->EmitInt8(0);
Asm->EOL("Padding");
}
EmitLabel("exception", SubprogramCount);
if (TAI->getExceptionHandlingType() == ExceptionHandling::SjLj) {
std::string SjLjName = "_lsda_";
SjLjName += MF->getFunction()->getName().str();
EmitLabel(SjLjName.c_str(), 0);
}
// Emit the header.
Asm->EmitInt8(dwarf::DW_EH_PE_omit);
Asm->EOL("@LPStart format (DW_EH_PE_omit)");
#if 0
if (TypeInfos.empty() && FilterIds.empty()) {
// If there are no typeinfos or filters, there is nothing to emit, optimize
// by specifying the "omit" encoding.
Asm->EmitInt8(dwarf::DW_EH_PE_omit);
Asm->EOL("@TType format (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 this 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.
//
if (LSDASection->isWritable() ||
Asm->TM.getRelocationModel() == Reloc::Static) {
Asm->EmitInt8(DW_EH_PE_absptr);
Asm->EOL("TType format (DW_EH_PE_absptr)");
} else {
Asm->EmitInt8(DW_EH_PE_pcrel | DW_EH_PE_indirect | DW_EH_PE_sdata4);
Asm->EOL("TType format (DW_EH_PE_pcrel | DW_EH_PE_indirect"
" | DW_EH_PE_sdata4)");
}
Asm->EmitULEB128Bytes(TypeOffset);
Asm->EOL("TType base offset");
}
#else
// For SjLj exceptions, if there is no TypeInfo, then we just explicitly
// say that we're omitting that bit.
// FIXME: does this apply to Dwarf also? The above #if 0 implies yes?
if (!HaveTTData) {
Asm->EmitInt8(dwarf::DW_EH_PE_omit);
Asm->EOL("@TType format (DW_EH_PE_omit)");
} else {
Asm->EmitInt8(dwarf::DW_EH_PE_absptr);
Asm->EOL("@TType format (DW_EH_PE_absptr)");
Asm->EmitULEB128Bytes(TypeOffset);
Asm->EOL("@TType base offset");
}
#endif
// SjLj Exception handilng
if (TAI->getExceptionHandlingType() == ExceptionHandling::SjLj) {
Asm->EmitInt8(dwarf::DW_EH_PE_udata4);
Asm->EOL("Call site format (DW_EH_PE_udata4)");
Asm->EmitULEB128Bytes(SizeSites);
Asm->EOL("Call site table length");
// 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->EmitULEB128Bytes(idx);
Asm->EOL("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->EmitULEB128Bytes(S.Action);
Asm->EOL("Action");
}
} else {
// DWARF Exception handling
assert(TAI->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. Such calls include:
//
// * Calls to destructors within cleanup code. C++ semantics forbids these
// calls to throw.
// * Calls to intrinsic routines in the standard library which are known
// not to throw (sin, memcpy, et al).
//
// If the runtime does not find the call-site entry for a given call, it
// will call `terminate()'.
// Emit the landing pad call site table.
Asm->EmitInt8(dwarf::DW_EH_PE_udata4);
Asm->EOL("Call site format (DW_EH_PE_udata4)");
Asm->EmitULEB128Bytes(SizeSites);
Asm->EOL("Call site table size");
for (SmallVectorImpl<CallSiteEntry>::const_iterator
I = CallSites.begin(), E = CallSites.end(); I != E; ++I) {
const CallSiteEntry &S = *I;
const char *BeginTag;
unsigned BeginNumber;
if (!S.BeginLabel) {
BeginTag = "eh_func_begin";
BeginNumber = SubprogramCount;
} else {
BeginTag = "label";
BeginNumber = S.BeginLabel;
}
// 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.
EmitSectionOffset(BeginTag, "eh_func_begin", BeginNumber, SubprogramCount,
true, true);
Asm->EOL("Region start");
if (!S.EndLabel)
EmitDifference("eh_func_end", SubprogramCount, BeginTag, BeginNumber,
true);
else
EmitDifference("label", S.EndLabel, BeginTag, BeginNumber, true);
Asm->EOL("Region length");
// Offset of the landing pad, counted in 16-byte bundles relative to the
// @LPStart address.
if (!S.PadLabel)
Asm->EmitInt32(0);
else
EmitSectionOffset("label", "eh_func_begin", S.PadLabel, SubprogramCount,
true, true);
Asm->EOL("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->EmitULEB128Bytes(S.Action);
Asm->EOL("Action");
}
}
// Emit the Action Table.
for (SmallVectorImpl<ActionEntry>::const_iterator
I = Actions.begin(), E = Actions.end(); I != E; ++I) {
const ActionEntry &Action = *I;
// 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->EmitSLEB128Bytes(Action.ValueForTypeID);
Asm->EOL("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->EmitSLEB128Bytes(Action.NextAction);
Asm->EOL("Next action");
}
// Emit the Catch Clauses. The code for the catch clauses following the same
// try is similar to a switch statement. The catch clause action record
// informs the runtime about the type of a catch clause and about the
// associated switch value.
//
// Action Record Fields:
//
// * Filter Value
// Positive value, starting at 1. Index in the types table of the
// __typeinfo for the catch-clause type. 1 is the first word preceding
// TTBase, 2 is the second word, and so on. Used by the runtime to check
// if the thrown exception type matches the catch-clause type. Back-end
// generated switch statements check against this value.
//
// * Next
// Signed offset, in bytes from the start of this field, to the next
// chained action record, or zero if none.
//
// The order of the action records determined by the next field is the order
// of the catch clauses as they appear in the source code, and must be kept in
// the same order. As a result, changing the order of the catch clause would
// change the semantics of the program.
for (std::vector<GlobalVariable *>::const_reverse_iterator
I = TypeInfos.rbegin(), E = TypeInfos.rend(); I != E; ++I) {
const GlobalVariable *GV = *I;
PrintRelDirective();
if (GV) {
std::string GLN;
O << Asm->getGlobalLinkName(GV, GLN);
} else {
O << "0";
}
Asm->EOL("TypeInfo");
}
// Emit the Type Table.
for (std::vector<unsigned>::const_iterator
I = FilterIds.begin(), E = FilterIds.end(); I < E; ++I) {
unsigned TypeID = *I;
Asm->EmitULEB128Bytes(TypeID);
Asm->EOL("Filter TypeInfo index");
}
Asm->EmitAlignment(2, 0, 0, false);
}
/// PrepareMonoLSDA - Collect information needed by EmitMonoLSDA
///
/// This function collects information available only during EndFunction which is needed
/// by EmitMonoLSDA and stores it into EHFrameInfo. It is the same as the
/// beginning of EmitExceptionTable.
///
void DwarfMonoException::PrepareMonoLSDA(FunctionEHFrameInfo *EHFrameInfo) {
const std::vector<const GlobalVariable *> &TypeInfos = MMI->getTypeInfos();
const std::vector<LandingPadInfo> &PadInfos = MMI->getLandingPads();
const MachineFunction *MF = Asm->MF;
// 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(),
[](const LandingPadInfo *L,
const LandingPadInfo *R) { return L->TypeIds < R->TypeIds; });
// 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<MonoCallSiteEntry, 64> CallSites;
MCSymbol *LastLabel = 0;
for (MachineFunction::const_iterator I = MF->begin(), E = MF->end();
I != E; ++I) {
for (MachineBasicBlock::const_iterator MI = I->begin(), E = I->end();
MI != E; ++MI) {
if (!MI->isLabel()) {
continue;
}
MCSymbol *BeginLabel = MI->getOperand(0).getMCSymbol();
assert(BeginLabel && "Invalid label!");
RangeMapType::iterator L = PadMap.find(BeginLabel);
if (L == PadMap.end())
continue;
PadRange P = L->second;
const LandingPadInfo *LandingPad = LandingPads[P.PadIndex];
assert(BeginLabel == LandingPad->BeginLabels[P.RangeIndex] &&
"Inconsistent landing pad map!");
// Mono emits one landing pad for each CLR exception clause,
// and the type info contains the clause index
assert (LandingPad->TypeIds.size() == 1);
assert (LandingPad->LandingPadLabel);
LastLabel = LandingPad->EndLabels[P.RangeIndex];
MonoCallSiteEntry Site = {BeginLabel, LastLabel,
LandingPad->LandingPadLabel, LandingPad->TypeIds [0]};
assert(Site.BeginLabel && Site.EndLabel && Site.PadLabel &&
"Invalid landing pad!");
// FIXME: This doesn't work because it includes ranges outside clauses
#if 0
// Try to merge with the previous call-site.
if (CallSites.size()) {
MonoCallSiteEntry &Prev = CallSites.back();
if (Site.PadLabel == Prev.PadLabel && Site.TypeID == Prev.TypeID) {
// Extend the range of the previous entry.
Prev.EndLabel = Site.EndLabel;
continue;
}
}
#endif
// Otherwise, create a new call-site.
CallSites.push_back(Site);
}
}
//
// Compute a mapping from method names to their AOT method index
//
if (FuncIndexes.size () == 0) {
const Module *m = MMI->getModule ();
NamedMDNode *indexes = m->getNamedMetadata ("mono.function_indexes");
if (indexes) {
for (unsigned int i = 0; i < indexes->getNumOperands (); ++i) {
MDNode *n = indexes->getOperand (i);
MDString *s = (MDString*)n->getOperand (0);
ConstantInt *idx = (ConstantInt*)n->getOperand (1);
FuncIndexes.GetOrCreateValue (s->getString (), (int)idx->getLimitedValue () + 1);
}
}
}
MonoEHFrameInfo *MonoEH = &EHFrameInfo->MonoEH;
// Save information for EmitMonoLSDA
MonoEH->MF = Asm->MF;
MonoEH->FunctionNumber = Asm->getFunctionNumber();
MonoEH->CallSites.insert(MonoEH->CallSites.begin(), CallSites.begin(), CallSites.end());
MonoEH->TypeInfos = TypeInfos;
MonoEH->PadInfos = PadInfos;
MonoEH->MonoMethodIdx = FuncIndexes.lookup (Asm->MF->getFunction ()->getName ()) - 1;
//outs()<<"A:"<<Asm->MF->getFunction()->getName() << " " << MonoEH->MonoMethodIdx << "\n";
int ThisSlot = Asm->MF->getMonoInfo()->getThisStackSlot();
if (ThisSlot != -1) {
unsigned FrameReg;
MonoEH->ThisOffset = Asm->MF->getTarget ().getSubtargetImpl ()->getFrameLowering ()->getFrameIndexReference (*Asm->MF, ThisSlot, FrameReg);
MonoEH->FrameReg = Asm->MF->getTarget ().getSubtargetImpl ()->getRegisterInfo ()->getDwarfRegNum (FrameReg, true);
} else {
MonoEH->FrameReg = -1;
}
}