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llvm-project/llvm/lib/CodeGen/AsmPrinter/DwarfException.cpp

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//===-- CodeGen/AsmPrinter/DwarfException.cpp - Dwarf Exception Impl ------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file contains support for writing DWARF exception info into asm files.
//
//===----------------------------------------------------------------------===//
#include "DwarfException.h"
#include "llvm/ADT/SmallString.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/ADT/Twine.h"
#include "llvm/CodeGen/AsmPrinter.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineModuleInfo.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/Mangler.h"
#include "llvm/IR/Module.h"
#include "llvm/MC/MCAsmInfo.h"
#include "llvm/MC/MCContext.h"
#include "llvm/MC/MCExpr.h"
#include "llvm/MC/MCSection.h"
#include "llvm/MC/MCStreamer.h"
#include "llvm/MC/MCSymbol.h"
#include "llvm/Support/Dwarf.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/FormattedStream.h"
#include "llvm/Support/LEB128.h"
#include "llvm/Target/TargetFrameLowering.h"
#include "llvm/Target/TargetLoweringObjectFile.h"
#include "llvm/Target/TargetOptions.h"
#include "llvm/Target/TargetRegisterInfo.h"
using namespace llvm;
DwarfException::DwarfException(AsmPrinter *A)
: Asm(A), MMI(Asm->MMI) {}
DwarfException::~DwarfException() {}
/// SharedTypeIds - How many leading type ids two landing pads have in common.
unsigned DwarfException::SharedTypeIds(const LandingPadInfo *L,
const LandingPadInfo *R) {
const std::vector<int> &LIds = L->TypeIds, &RIds = R->TypeIds;
unsigned LSize = LIds.size(), RSize = RIds.size();
unsigned MinSize = LSize < RSize ? LSize : RSize;
unsigned Count = 0;
for (; Count != MinSize; ++Count)
if (LIds[Count] != RIds[Count])
return Count;
return Count;
}
/// ComputeActionsTable - Compute the actions table and gather the first action
/// index for each landing pad site.
unsigned DwarfException::
ComputeActionsTable(const SmallVectorImpl<const LandingPadInfo*> &LandingPads,
SmallVectorImpl<ActionEntry> &Actions,
SmallVectorImpl<unsigned> &FirstActions) {
// The action table follows the call-site table in the LSDA. The individual
// records are of two types:
//
// * Catch clause
// * Exception specification
//
// The two record kinds have the same format, with only small differences.
// They are distinguished by the "switch value" field: Catch clauses
// (TypeInfos) have strictly positive switch values, and exception
// specifications (FilterIds) have strictly negative switch values. Value 0
// indicates a catch-all clause.
//
// Negative type IDs index into FilterIds. Positive type IDs index into
// TypeInfos. The value written for a positive type ID is just the type ID
// itself. For a negative type ID, however, the value written is the
// (negative) byte offset of the corresponding FilterIds entry. The byte
// offset is usually equal to the type ID (because the FilterIds entries are
// written using a variable width encoding, which outputs one byte per entry
// as long as the value written is not too large) but can differ. This kind
// of complication does not occur for positive type IDs because type infos are
// output using a fixed width encoding. FilterOffsets[i] holds the byte
// offset corresponding to FilterIds[i].
const std::vector<unsigned> &FilterIds = MMI->getFilterIds();
SmallVector<int, 16> FilterOffsets;
FilterOffsets.reserve(FilterIds.size());
int Offset = -1;
for (std::vector<unsigned>::const_iterator
I = FilterIds.begin(), E = FilterIds.end(); I != E; ++I) {
FilterOffsets.push_back(Offset);
Offset -= getULEB128Size(*I);
}
FirstActions.reserve(LandingPads.size());
int FirstAction = 0;
unsigned SizeActions = 0;
const LandingPadInfo *PrevLPI = 0;
for (SmallVectorImpl<const LandingPadInfo *>::const_iterator
I = LandingPads.begin(), E = LandingPads.end(); I != E; ++I) {
const LandingPadInfo *LPI = *I;
const std::vector<int> &TypeIds = LPI->TypeIds;
unsigned NumShared = PrevLPI ? SharedTypeIds(LPI, PrevLPI) : 0;
unsigned SizeSiteActions = 0;
if (NumShared < TypeIds.size()) {
unsigned SizeAction = 0;
unsigned PrevAction = (unsigned)-1;
if (NumShared) {
unsigned SizePrevIds = PrevLPI->TypeIds.size();
assert(Actions.size());
PrevAction = Actions.size() - 1;
SizeAction = getSLEB128Size(Actions[PrevAction].NextAction) +
getSLEB128Size(Actions[PrevAction].ValueForTypeID);
for (unsigned j = NumShared; j != SizePrevIds; ++j) {
assert(PrevAction != (unsigned)-1 && "PrevAction is invalid!");
SizeAction -= getSLEB128Size(Actions[PrevAction].ValueForTypeID);
SizeAction += -Actions[PrevAction].NextAction;
PrevAction = Actions[PrevAction].Previous;
}
}
// Compute the actions.
for (unsigned J = NumShared, M = TypeIds.size(); J != M; ++J) {
int TypeID = TypeIds[J];
assert(-1 - TypeID < (int)FilterOffsets.size() && "Unknown filter id!");
int ValueForTypeID = TypeID < 0 ? FilterOffsets[-1 - TypeID] : TypeID;
unsigned SizeTypeID = getSLEB128Size(ValueForTypeID);
int NextAction = SizeAction ? -(SizeAction + SizeTypeID) : 0;
SizeAction = SizeTypeID + getSLEB128Size(NextAction);
SizeSiteActions += SizeAction;
ActionEntry Action = { ValueForTypeID, NextAction, PrevAction };
Actions.push_back(Action);
PrevAction = Actions.size() - 1;
}
// Record the first action of the landing pad site.
FirstAction = SizeActions + SizeSiteActions - SizeAction + 1;
} // else identical - re-use previous FirstAction
// Information used when created the call-site table. The action record
// field of the call site record is the offset of the first associated
// action record, relative to the start of the actions table. This value is
// biased by 1 (1 indicating the start of the actions table), and 0
// indicates that there are no actions.
FirstActions.push_back(FirstAction);
// Compute this sites contribution to size.
SizeActions += SizeSiteActions;
PrevLPI = LPI;
}
return SizeActions;
}
/// CallToNoUnwindFunction - Return `true' if this is a call to a function
/// marked `nounwind'. Return `false' otherwise.
bool DwarfException::CallToNoUnwindFunction(const MachineInstr *MI) {
assert(MI->isCall() && "This should be a call instruction!");
bool MarkedNoUnwind = false;
bool SawFunc = false;
for (unsigned I = 0, E = MI->getNumOperands(); I != E; ++I) {
const MachineOperand &MO = MI->getOperand(I);
if (!MO.isGlobal()) continue;
const Function *F = dyn_cast<Function>(MO.getGlobal());
if (F == 0) continue;
if (SawFunc) {
// Be conservative. If we have more than one function operand for this
// call, then we can't make the assumption that it's the callee and
// not a parameter to the call.
//
// FIXME: Determine if there's a way to say that `F' is the callee or
// parameter.
MarkedNoUnwind = false;
break;
}
MarkedNoUnwind = F->doesNotThrow();
SawFunc = true;
}
return MarkedNoUnwind;
}
/// ComputeCallSiteTable - Compute the call-site table. The entry for an invoke
/// has a try-range containing the call, a non-zero landing pad, and an
/// appropriate action. The entry for an ordinary call has a try-range
/// containing the call and zero for the landing pad and the action. Calls
/// marked 'nounwind' have no entry and must not be contained in the try-range
/// of any entry - they form gaps in the table. Entries must be ordered by
/// try-range address.
void DwarfException::
ComputeCallSiteTable(SmallVectorImpl<CallSiteEntry> &CallSites,
const RangeMapType &PadMap,
const SmallVectorImpl<const LandingPadInfo *> &LandingPads,
const SmallVectorImpl<unsigned> &FirstActions) {
// The end label of the previous invoke or nounwind try-range.
MCSymbol *LastLabel = 0;
// Whether there is a potentially throwing instruction (currently this means
// an ordinary call) between the end of the previous try-range and now.
bool SawPotentiallyThrowing = false;
// Whether the last CallSite entry was for an invoke.
bool PreviousIsInvoke = false;
// Visit all instructions in order of address.
for (MachineFunction::const_iterator I = Asm->MF->begin(), E = Asm->MF->end();
I != E; ++I) {
for (MachineBasicBlock::const_iterator MI = I->begin(), E = I->end();
MI != E; ++MI) {
if (!MI->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 && 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);
}
}
/// 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]);
// Order landing pads lexicographically by type id.
std::sort(LandingPads.begin(), LandingPads.end(),
[](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;
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 += getULEB128Size(CallSites[i].Action);
if (IsSJLJ)
CallSiteTableLength += 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 = 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 = 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*/);
} 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);
}
EmitTypeInfos(TTypeEncoding);
Asm->EmitAlignment(2);
}
void DwarfException::EmitTypeInfos(unsigned TTypeEncoding) {
const std::vector<const GlobalVariable *> &TypeInfos = MMI->getTypeInfos();
const std::vector<unsigned> &FilterIds = MMI->getFilterIds();
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 (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--));
Asm->EmitTTypeReference(GV, TTypeEncoding);
}
// 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);
}
}
/// endModule - Emit all exception information that should come after the
/// content.
void DwarfException::endModule() {
llvm_unreachable("Should be implemented");
}
/// beginFunction - Gather pre-function exception information. Assumes it's
/// being emitted immediately after the function entry point.
void DwarfException::beginFunction(const MachineFunction *MF) {
llvm_unreachable("Should be implemented");
}
/// endFunction - Gather and emit post-function exception information.
void DwarfException::endFunction(const MachineFunction *) {
llvm_unreachable("Should be implemented");
}
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