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llvm-6502/lib/CodeGen/AsmPrinter/DwarfException.cpp
Jim Grosbach 1b747ad8a0 SjLj based exception handling unwinding support. This patch is nasty, brutish 
and short. Well, it's kinda short. Definitely nasty and brutish.

The front-end generates the register/unregister calls into the SjLj runtime,
call-site indices and landing pad dispatch. The back end fills in the LSDA
with the call-site information provided by the front end. Catch blocks are
not yet implemented.

Built on Darwin and verified no llvm-core "make check" regressions.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@78625 91177308-0d34-0410-b5e6-96231b3b80d8
2009-08-11 00:09:57 +00:00

841 lines
32 KiB
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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/Module.h"
#include "llvm/CodeGen/MachineModuleInfo.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineLocation.h"
#include "llvm/Support/Dwarf.h"
#include "llvm/Support/Timer.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Target/TargetAsmInfo.h"
#include "llvm/Target/TargetData.h"
#include "llvm/Target/TargetFrameInfo.h"
#include "llvm/Target/TargetLoweringObjectFile.h"
#include "llvm/Target/TargetOptions.h"
#include "llvm/Target/TargetRegisterInfo.h"
#include "llvm/ADT/StringExtras.h"
using namespace llvm;
static TimerGroup &getDwarfTimerGroup() {
static TimerGroup DwarfTimerGroup("Dwarf Exception");
return DwarfTimerGroup;
}
DwarfException::DwarfException(raw_ostream &OS, AsmPrinter *A,
const TargetAsmInfo *T)
: Dwarf(OS, A, T, "eh"), shouldEmitTable(false), shouldEmitMoves(false),
shouldEmitTableModule(false), shouldEmitMovesModule(false),
ExceptionTimer(0) {
if (TimePassesIsEnabled)
ExceptionTimer = new Timer("Dwarf Exception Writer",
getDwarfTimerGroup());
}
DwarfException::~DwarfException() {
delete ExceptionTimer;
}
void DwarfException::EmitCommonEHFrame(const Function *Personality,
unsigned Index) {
// Size and sign of stack growth.
int stackGrowth =
Asm->TM.getFrameInfo()->getStackGrowthDirection() ==
TargetFrameInfo::StackGrowsUp ?
TD->getPointerSize() : -TD->getPointerSize();
// Begin eh frame section.
Asm->SwitchToSection(Asm->getObjFileLowering().getEHFrameSection());
if (TAI->is_EHSymbolPrivate())
O << TAI->getPrivateGlobalPrefix();
O << "EH_frame" << Index << ":\n";
EmitLabel("section_eh_frame", Index);
// Define base labels.
EmitLabel("eh_frame_common", Index);
// Define the eh frame length.
EmitDifference("eh_frame_common_end", Index,
"eh_frame_common_begin", Index, true);
Asm->EOL("Length of Common Information Entry");
// EH frame header.
EmitLabel("eh_frame_common_begin", Index);
Asm->EmitInt32((int)0);
Asm->EOL("CIE Identifier Tag");
Asm->EmitInt8(dwarf::DW_CIE_VERSION);
Asm->EOL("CIE Version");
// The personality presence indicates that language specific information will
// show up in the eh frame.
Asm->EmitString(Personality ? "zPLR" : "zR");
Asm->EOL("CIE Augmentation");
// Round out reader.
Asm->EmitULEB128Bytes(1);
Asm->EOL("CIE Code Alignment Factor");
Asm->EmitSLEB128Bytes(stackGrowth);
Asm->EOL("CIE Data Alignment Factor");
Asm->EmitInt8(RI->getDwarfRegNum(RI->getRARegister(), true));
Asm->EOL("CIE Return Address Column");
// If there is a personality, we need to indicate the functions location.
if (Personality) {
Asm->EmitULEB128Bytes(7);
Asm->EOL("Augmentation Size");
if (TAI->getNeedsIndirectEncoding()) {
Asm->EmitInt8(dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4 |
dwarf::DW_EH_PE_indirect);
Asm->EOL("Personality (pcrel sdata4 indirect)");
} else {
Asm->EmitInt8(dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4);
Asm->EOL("Personality (pcrel sdata4)");
}
PrintRelDirective(true);
O << TAI->getPersonalityPrefix();
Asm->EmitExternalGlobal((const GlobalVariable *)(Personality));
O << TAI->getPersonalitySuffix();
if (strcmp(TAI->getPersonalitySuffix(), "+4@GOTPCREL"))
O << "-" << TAI->getPCSymbol();
Asm->EOL("Personality");
Asm->EmitInt8(dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4);
Asm->EOL("LSDA Encoding (pcrel sdata4)");
Asm->EmitInt8(dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4);
Asm->EOL("FDE Encoding (pcrel sdata4)");
} else {
Asm->EmitULEB128Bytes(1);
Asm->EOL("Augmentation Size");
Asm->EmitInt8(dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4);
Asm->EOL("FDE Encoding (pcrel sdata4)");
}
// Indicate locations of general callee saved registers in frame.
std::vector<MachineMove> Moves;
RI->getInitialFrameState(Moves);
EmitFrameMoves(NULL, 0, Moves, true);
// On Darwin the linker honors the alignment of eh_frame, which means it must
// be 8-byte on 64-bit targets to match what gcc does. Otherwise you get
// holes which confuse readers of eh_frame.
Asm->EmitAlignment(TD->getPointerSize() == sizeof(int32_t) ? 2 : 3,
0, 0, false);
EmitLabel("eh_frame_common_end", Index);
Asm->EOL();
}
/// EmitEHFrame - Emit function exception frame information.
///
void DwarfException::EmitEHFrame(const FunctionEHFrameInfo &EHFrameInfo) {
assert(!EHFrameInfo.function->hasAvailableExternallyLinkage() &&
"Should not emit 'available externally' functions at all");
const Function *TheFunc = EHFrameInfo.function;
Asm->SwitchToSection(Asm->getObjFileLowering().getEHFrameSection());
// Externally visible entry into the functions eh frame info. If the
// corresponding function is static, this should not be externally visible.
if (!TheFunc->hasLocalLinkage())
if (const char *GlobalEHDirective = TAI->getGlobalEHDirective())
O << GlobalEHDirective << EHFrameInfo.FnName << "\n";
// If corresponding function is weak definition, this should be too.
if (TheFunc->isWeakForLinker() && TAI->getWeakDefDirective())
O << TAI->getWeakDefDirective() << EHFrameInfo.FnName << "\n";
// If there are no calls then you can't unwind. This may mean we can omit the
// EH Frame, but some environments do not handle weak absolute symbols. If
// UnwindTablesMandatory is set we cannot do this optimization; the unwind
// info is to be available for non-EH uses.
if (!EHFrameInfo.hasCalls && !UnwindTablesMandatory &&
(!TheFunc->isWeakForLinker() ||
!TAI->getWeakDefDirective() ||
TAI->getSupportsWeakOmittedEHFrame())) {
O << EHFrameInfo.FnName << " = 0\n";
// This name has no connection to the function, so it might get
// dead-stripped when the function is not, erroneously. Prohibit
// dead-stripping unconditionally.
if (const char *UsedDirective = TAI->getUsedDirective())
O << UsedDirective << EHFrameInfo.FnName << "\n\n";
} else {
O << EHFrameInfo.FnName << ":\n";
// EH frame header.
EmitDifference("eh_frame_end", EHFrameInfo.Number,
"eh_frame_begin", EHFrameInfo.Number, true);
Asm->EOL("Length of Frame Information Entry");
EmitLabel("eh_frame_begin", EHFrameInfo.Number);
EmitSectionOffset("eh_frame_begin", "eh_frame_common",
EHFrameInfo.Number, EHFrameInfo.PersonalityIndex,
true, true, false);
Asm->EOL("FDE CIE offset");
EmitReference("eh_func_begin", EHFrameInfo.Number, true, true);
Asm->EOL("FDE initial location");
EmitDifference("eh_func_end", EHFrameInfo.Number,
"eh_func_begin", EHFrameInfo.Number, true);
Asm->EOL("FDE address range");
// If there is a personality and landing pads then point to the language
// specific data area in the exception table.
if (EHFrameInfo.PersonalityIndex) {
Asm->EmitULEB128Bytes(4);
Asm->EOL("Augmentation size");
if (EHFrameInfo.hasLandingPads)
EmitReference("exception", EHFrameInfo.Number, true, true);
else
Asm->EmitInt32((int)0);
Asm->EOL("Language Specific Data Area");
} else {
Asm->EmitULEB128Bytes(0);
Asm->EOL("Augmentation size");
}
// Indicate locations of function specific callee saved registers in frame.
EmitFrameMoves("eh_func_begin", EHFrameInfo.Number, EHFrameInfo.Moves,
true);
// On Darwin the linker honors the alignment of eh_frame, which means it
// must be 8-byte on 64-bit targets to match what gcc does. Otherwise you
// get holes which confuse readers of eh_frame.
Asm->EmitAlignment(TD->getPointerSize() == sizeof(int32_t) ? 2 : 3,
0, 0, false);
EmitLabel("eh_frame_end", EHFrameInfo.Number);
// If the function is marked used, this table should be also. We cannot
// make the mark unconditional in this case, since retaining the table also
// retains the function in this case, and there is code around that depends
// on unused functions (calling undefined externals) being dead-stripped to
// link correctly. Yes, there really is.
if (MMI->isUsedFunction(EHFrameInfo.function))
if (const char *UsedDirective = TAI->getUsedDirective())
O << UsedDirective << EHFrameInfo.FnName << "\n\n";
}
}
/// SharedTypeIds - How many leading type ids two landing pads have in common.
unsigned DwarfException::SharedTypeIds(const LandingPadInfo *L,
const LandingPadInfo *R) {
const std::vector<int> &LIds = L->TypeIds, &RIds = R->TypeIds;
unsigned LSize = LIds.size(), RSize = RIds.size();
unsigned MinSize = LSize < RSize ? LSize : RSize;
unsigned Count = 0;
for (; Count != MinSize; ++Count)
if (LIds[Count] != RIds[Count])
return Count;
return Count;
}
/// PadLT - Order landing pads lexicographically by type id.
bool DwarfException::PadLT(const LandingPadInfo *L, const LandingPadInfo *R) {
const std::vector<int> &LIds = L->TypeIds, &RIds = R->TypeIds;
unsigned LSize = LIds.size(), RSize = RIds.size();
unsigned MinSize = LSize < RSize ? LSize : RSize;
for (unsigned i = 0; i != MinSize; ++i)
if (LIds[i] != RIds[i])
return LIds[i] < RIds[i];
return LSize < RSize;
}
/// ComputeActionsTable - Compute the actions table and gather the first action
/// index for each landing pad site.
unsigned DwarfException::
ComputeActionsTable(const SmallVectorImpl<const LandingPadInfo*> &LandingPads,
SmallVectorImpl<ActionEntry> &Actions,
SmallVectorImpl<unsigned> &FirstActions) {
// 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 -= TargetAsmInfo::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;
const unsigned NumShared = PrevLPI ? SharedTypeIds(LPI, PrevLPI) : 0;
unsigned SizeSiteActions = 0;
if (NumShared < TypeIds.size()) {
unsigned SizeAction = 0;
ActionEntry *PrevAction = 0;
if (NumShared) {
const unsigned SizePrevIds = PrevLPI->TypeIds.size();
assert(Actions.size());
PrevAction = &Actions.back();
SizeAction = TargetAsmInfo::getSLEB128Size(PrevAction->NextAction) +
TargetAsmInfo::getSLEB128Size(PrevAction->ValueForTypeID);
for (unsigned j = NumShared; j != SizePrevIds; ++j) {
SizeAction -=
TargetAsmInfo::getSLEB128Size(PrevAction->ValueForTypeID);
SizeAction += -PrevAction->NextAction;
PrevAction = 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 = TargetAsmInfo::getSLEB128Size(ValueForTypeID);
int NextAction = SizeAction ? -(SizeAction + SizeTypeID) : 0;
SizeAction = SizeTypeID + TargetAsmInfo::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;
PrevLPI = LPI;
}
return SizeActions;
}
/// 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,
std::map<unsigned,CallSiteEntry*> &CallSiteIndexMap,
const RangeMapType &PadMap,
const SmallVectorImpl<const LandingPadInfo *> &LandingPads,
const SmallVectorImpl<unsigned> &FirstActions) {
// The end label of the previous invoke or nounwind try-range.
unsigned 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 = MF->begin(), E = MF->end();
I != E; ++I) {
for (MachineBasicBlock::const_iterator MI = I->begin(), E = I->end();
MI != E; ++MI) {
if (!MI->isLabel()) {
SawPotentiallyThrowing |= MI->getDesc().isCall();
continue;
}
unsigned BeginLabel = MI->getOperand(0).getImm();
assert(BeginLabel && "Invalid label!");
// End of the previous try-range?
if (BeginLabel == LastLabel)
SawPotentiallyThrowing = false;
// Beginning of a new try-range?
RangeMapType::iterator L = PadMap.find(BeginLabel);
if (L == PadMap.end())
// Nope, it was just some random label.
continue;
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 &&
TAI->getExceptionHandlingType() == ExceptionHandling::Dwarf) {
CallSiteEntry Site = {LastLabel, BeginLabel, 0, 0};
CallSites.push_back(Site);
PreviousIsInvoke = false;
}
LastLabel = LandingPad->EndLabels[P.RangeIndex];
assert(BeginLabel && LastLabel && "Invalid landing pad!");
if (LandingPad->LandingPadLabel) {
// This try-range is for an invoke.
CallSiteEntry Site = {BeginLabel, LastLabel,
LandingPad->LandingPadLabel,
FirstActions[P.PadIndex]};
// Try to merge with the previous call-site.
if (PreviousIsInvoke) {
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);
// For SjLj handling, map the call site entry to its index
if (TAI->getExceptionHandlingType() == ExceptionHandling::SjLj) {
unsigned Index =
MF->getLandingPadCallSiteIndex(LandingPad->LandingPadBlock);
CallSiteIndexMap[Index] = &CallSites.back();
}
PreviousIsInvoke = true;
} else {
// Create a gap.
PreviousIsInvoke = false;
}
}
}
// 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 &&
TAI->getExceptionHandlingType() == ExceptionHandling::Dwarf) {
CallSiteEntry Site = {LastLabel, 0, 0, 0};
CallSites.push_back(Site);
}
}
/// EmitExceptionTable - Emit landing pads and actions.
///
/// The general organization of the table is complex, but the basic concepts are
/// easy. First there is a header which describes the location and organization
/// of the three components that follow.
///
/// 1. The landing pad site information describes the range of code covered by
/// the try. In our case it's an accumulation of the ranges covered by the
/// invokes in the try. There is also a reference to the landing pad that
/// handles the exception once processed. Finally an index into the actions
/// table.
/// 2. The action table, in our case, is composed of pairs of type ids and next
/// action offset. Starting with the action index from the landing pad
/// site, each type Id is checked for a match to the current exception. If
/// it matches then the exception and type id are passed on to the landing
/// pad. Otherwise the next action is looked up. This chain is terminated
/// with a next action of zero. If no type id is found 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;
std::map<unsigned,CallSiteEntry*> CallSiteIndexMap;
ComputeCallSiteTable(CallSites, CallSiteIndexMap, 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;
if (TAI->getExceptionHandlingType() == ExceptionHandling::SjLj) {
SizeSites = (MF->getMaxCallSiteIndex() - CallSites.size()) *
TargetAsmInfo::getULEB128Size(0) * 2;
} 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);
// FIXME: 'i' above should be the landing pad index
}
// 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
TargetAsmInfo::getULEB128Size(TypeOffset) + // TType base offset
TypeOffset;
unsigned SizeAlign = (4 - TotalSize) & 3;
// Begin the exception table.
const MCSection *LSDASection = Asm->getObjFileLowering().getLSDASection();
Asm->SwitchToSection(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, is 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 (TAI->getExceptionHandlingType() == ExceptionHandling::SjLj
&& (TypeInfos.empty() || FilterIds.empty())) {
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");
assert(MF->getCallSiteCount() == CallSites.size());
// Emit the landing pad site information.
// SjLj handling assigned the call site indices in the front end, so
// we need to make sure the table here lines up with that. That's pretty
// horrible, and should be fixed ASAP to do that stuff in the back end
// instead.
std::map<unsigned, CallSiteEntry*>::const_iterator I, E;
I = CallSiteIndexMap.begin();
E = CallSiteIndexMap.end();
for (unsigned CurrIdx = 1; I != E; ++I) {
// paranoia.
assert(CurrIdx <= I->first);
// Fill in any gaps in the table
while (CurrIdx++ < I->first) {
Asm->EmitULEB128Bytes(0);
Asm->EOL("Filler landing pad");
Asm->EmitULEB128Bytes(0);
Asm->EOL("Filler action");
}
const CallSiteEntry &S = *(I->second);
Asm->EmitULEB128Bytes(I->first - 1);
Asm->EOL("Landing pad");
Asm->EmitULEB128Bytes(S.Action);
Asm->EOL("Action");
}
} else {
// DWARF Exception handling
assert(TAI->getExceptionHandlingType() == ExceptionHandling::Dwarf);
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.
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;
}
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");
if (!S.PadLabel)
Asm->EmitInt32(0);
else
EmitSectionOffset("label", "eh_func_begin", S.PadLabel, SubprogramCount,
true, true);
Asm->EOL("Landing pad");
Asm->EmitULEB128Bytes(S.Action);
Asm->EOL("Action");
}
}
// Emit the actions.
for (SmallVectorImpl<ActionEntry>::const_iterator
I = Actions.begin(), E = Actions.end(); I != E; ++I) {
const ActionEntry &Action = *I;
Asm->EmitSLEB128Bytes(Action.ValueForTypeID);
Asm->EOL("TypeInfo index");
Asm->EmitSLEB128Bytes(Action.NextAction);
Asm->EOL("Next action");
}
// Emit the type ids.
for (std::vector<GlobalVariable *>::const_reverse_iterator
I = TypeInfos.rbegin(), E = TypeInfos.rend(); I != E; ++I) {
GlobalVariable *GV = *I;
PrintRelDirective();
if (GV) {
std::string GLN;
O << Asm->getGlobalLinkName(GV, GLN);
} else {
O << "0";
}
Asm->EOL("TypeInfo");
}
// Emit the filter typeids.
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);
}
/// EndModule - Emit all exception information that should come after the
/// content.
void DwarfException::EndModule() {
if (TAI->getExceptionHandlingType() != ExceptionHandling::Dwarf)
return;
if (TimePassesIsEnabled)
ExceptionTimer->startTimer();
if (shouldEmitMovesModule || shouldEmitTableModule) {
const std::vector<Function *> Personalities = MMI->getPersonalities();
for (unsigned i = 0; i < Personalities.size(); ++i)
EmitCommonEHFrame(Personalities[i], i);
for (std::vector<FunctionEHFrameInfo>::iterator I = EHFrames.begin(),
E = EHFrames.end(); I != E; ++I)
EmitEHFrame(*I);
}
if (TimePassesIsEnabled)
ExceptionTimer->stopTimer();
}
/// BeginFunction - Gather pre-function exception information. Assumes being
/// emitted immediately after the function entry point.
void DwarfException::BeginFunction(MachineFunction *MF) {
if (TimePassesIsEnabled)
ExceptionTimer->startTimer();
this->MF = MF;
shouldEmitTable = shouldEmitMoves = false;
if (MMI && TAI->doesSupportExceptionHandling()) {
// Map all labels and get rid of any dead landing pads.
MMI->TidyLandingPads();
// If any landing pads survive, we need an EH table.
if (MMI->getLandingPads().size())
shouldEmitTable = true;
// See if we need frame move info.
if (!MF->getFunction()->doesNotThrow() || UnwindTablesMandatory)
shouldEmitMoves = true;
if (shouldEmitMoves || shouldEmitTable)
// Assumes in correct section after the entry point.
EmitLabel("eh_func_begin", ++SubprogramCount);
}
shouldEmitTableModule |= shouldEmitTable;
shouldEmitMovesModule |= shouldEmitMoves;
if (TimePassesIsEnabled)
ExceptionTimer->stopTimer();
}
/// EndFunction - Gather and emit post-function exception information.
///
void DwarfException::EndFunction() {
if (TimePassesIsEnabled)
ExceptionTimer->startTimer();
if (shouldEmitMoves || shouldEmitTable) {
EmitLabel("eh_func_end", SubprogramCount);
EmitExceptionTable();
// Save EH frame information
EHFrames.push_back(
FunctionEHFrameInfo(getAsm()->getCurrentFunctionEHName(MF),
SubprogramCount,
MMI->getPersonalityIndex(),
MF->getFrameInfo()->hasCalls(),
!MMI->getLandingPads().empty(),
MMI->getFrameMoves(),
MF->getFunction()));
}
if (TimePassesIsEnabled)
ExceptionTimer->stopTimer();
}
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