1 //===-- CodeGen/AsmPrinter/Win64Exception.cpp - Dwarf Exception Impl ------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file contains support for writing Win64 exception info into asm files.
12 //===----------------------------------------------------------------------===//
14 #include "Win64Exception.h"
15 #include "llvm/ADT/SmallString.h"
16 #include "llvm/ADT/StringExtras.h"
17 #include "llvm/ADT/Twine.h"
18 #include "llvm/CodeGen/AsmPrinter.h"
19 #include "llvm/CodeGen/MachineFrameInfo.h"
20 #include "llvm/CodeGen/MachineFunction.h"
21 #include "llvm/CodeGen/MachineModuleInfo.h"
22 #include "llvm/CodeGen/WinEHFuncInfo.h"
23 #include "llvm/IR/DataLayout.h"
24 #include "llvm/IR/Mangler.h"
25 #include "llvm/IR/Module.h"
26 #include "llvm/MC/MCAsmInfo.h"
27 #include "llvm/MC/MCContext.h"
28 #include "llvm/MC/MCExpr.h"
29 #include "llvm/MC/MCSection.h"
30 #include "llvm/MC/MCStreamer.h"
31 #include "llvm/MC/MCSymbol.h"
32 #include "llvm/Support/Dwarf.h"
33 #include "llvm/Support/ErrorHandling.h"
34 #include "llvm/Support/FormattedStream.h"
35 #include "llvm/Target/TargetFrameLowering.h"
36 #include "llvm/Target/TargetLoweringObjectFile.h"
37 #include "llvm/Target/TargetOptions.h"
38 #include "llvm/Target/TargetRegisterInfo.h"
41 Win64Exception::Win64Exception(AsmPrinter *A)
42 : EHStreamer(A), shouldEmitPersonality(false), shouldEmitLSDA(false),
43 shouldEmitMoves(false) {}
45 Win64Exception::~Win64Exception() {}
47 /// endModule - Emit all exception information that should come after the
49 void Win64Exception::endModule() {
52 void Win64Exception::beginFunction(const MachineFunction *MF) {
53 shouldEmitMoves = shouldEmitPersonality = shouldEmitLSDA = false;
55 // If any landing pads survive, we need an EH table.
56 bool hasLandingPads = !MMI->getLandingPads().empty();
58 shouldEmitMoves = Asm->needsSEHMoves();
60 const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering();
61 unsigned PerEncoding = TLOF.getPersonalityEncoding();
62 const Function *Per = MF->getMMI().getPersonality();
64 shouldEmitPersonality = hasLandingPads &&
65 PerEncoding != dwarf::DW_EH_PE_omit && Per;
67 unsigned LSDAEncoding = TLOF.getLSDAEncoding();
68 shouldEmitLSDA = shouldEmitPersonality &&
69 LSDAEncoding != dwarf::DW_EH_PE_omit;
72 // If this was an outlined handler, we need to define the label corresponding
73 // to the offset of the parent frame relative to the stack pointer after the
75 const Function *F = MF->getFunction();
76 const Function *ParentF = MMI->getWinEHParent(F);
78 WinEHFuncInfo &FuncInfo = MMI->getWinEHFuncInfo(ParentF);
79 auto I = FuncInfo.CatchHandlerParentFrameObjOffset.find(F);
80 if (I != FuncInfo.CatchHandlerParentFrameObjOffset.end()) {
81 MCSymbol *HandlerTypeParentFrameOffset =
82 Asm->OutContext.getOrCreateParentFrameOffsetSymbol(
83 GlobalValue::getRealLinkageName(F->getName()));
85 // Emit a symbol assignment.
86 Asm->OutStreamer.EmitAssignment(
87 HandlerTypeParentFrameOffset,
88 MCConstantExpr::Create(I->second, Asm->OutContext));
92 if (!shouldEmitPersonality && !shouldEmitMoves)
95 Asm->OutStreamer.EmitWinCFIStartProc(Asm->CurrentFnSym);
97 if (!shouldEmitPersonality)
100 const MCSymbol *PersHandlerSym =
101 TLOF.getCFIPersonalitySymbol(Per, *Asm->Mang, Asm->TM, MMI);
102 Asm->OutStreamer.EmitWinEHHandler(PersHandlerSym, true, true);
105 /// endFunction - Gather and emit post-function exception information.
107 void Win64Exception::endFunction(const MachineFunction *MF) {
108 if (!shouldEmitPersonality && !shouldEmitMoves)
111 EHPersonality Per = MMI->getPersonalityType();
113 // Get rid of any dead landing pads if we're not using a Windows EH scheme. In
114 // Windows EH schemes, the landing pad is not actually reachable. It only
115 // exists so that we can emit the right table data.
116 if (!isMSVCEHPersonality(Per))
117 MMI->TidyLandingPads();
119 if (shouldEmitPersonality) {
120 Asm->OutStreamer.PushSection();
122 // Emit an UNWIND_INFO struct describing the prologue.
123 Asm->OutStreamer.EmitWinEHHandlerData();
125 // Emit the tables appropriate to the personality function in use. If we
126 // don't recognize the personality, assume it uses an Itanium-style LSDA.
127 if (Per == EHPersonality::MSVC_Win64SEH)
128 emitCSpecificHandlerTable();
129 else if (Per == EHPersonality::MSVC_CXX)
130 emitCXXFrameHandler3Table(MF);
132 emitExceptionTable();
134 Asm->OutStreamer.PopSection();
136 Asm->OutStreamer.EmitWinCFIEndProc();
139 const MCExpr *Win64Exception::createImageRel32(const MCSymbol *Value) {
141 return MCConstantExpr::Create(0, Asm->OutContext);
142 return MCSymbolRefExpr::Create(Value, MCSymbolRefExpr::VK_COFF_IMGREL32,
146 const MCExpr *Win64Exception::createImageRel32(const GlobalValue *GV) {
148 return MCConstantExpr::Create(0, Asm->OutContext);
149 return createImageRel32(Asm->getSymbol(GV));
152 /// Emit the language-specific data that __C_specific_handler expects. This
153 /// handler lives in the x64 Microsoft C runtime and allows catching or cleaning
154 /// up after faults with __try, __except, and __finally. The typeinfo values
155 /// are not really RTTI data, but pointers to filter functions that return an
156 /// integer (1, 0, or -1) indicating how to handle the exception. For __finally
157 /// blocks and other cleanups, the landing pad label is zero, and the filter
158 /// function is actually a cleanup handler with the same prototype. A catch-all
159 /// entry is modeled with a null filter function field and a non-zero landing
162 /// Possible filter function return values:
163 /// EXCEPTION_EXECUTE_HANDLER (1):
164 /// Jump to the landing pad label after cleanups.
165 /// EXCEPTION_CONTINUE_SEARCH (0):
166 /// Continue searching this table or continue unwinding.
167 /// EXCEPTION_CONTINUE_EXECUTION (-1):
168 /// Resume execution at the trapping PC.
170 /// Inferred table structure:
174 /// imagerel32 LabelStart;
175 /// imagerel32 LabelEnd;
176 /// imagerel32 FilterOrFinally; // One means catch-all.
177 /// imagerel32 LabelLPad; // Zero means __finally.
178 /// } Entries[NumEntries];
180 void Win64Exception::emitCSpecificHandlerTable() {
181 const std::vector<LandingPadInfo> &PadInfos = MMI->getLandingPads();
183 // Simplifying assumptions for first implementation:
184 // - Cleanups are not implemented.
185 // - Filters are not implemented.
187 // The Itanium LSDA table sorts similar landing pads together to simplify the
188 // actions table, but we don't need that.
189 SmallVector<const LandingPadInfo *, 64> LandingPads;
190 LandingPads.reserve(PadInfos.size());
191 for (const auto &LP : PadInfos)
192 LandingPads.push_back(&LP);
194 // Compute label ranges for call sites as we would for the Itanium LSDA, but
195 // use an all zero action table because we aren't using these actions.
196 SmallVector<unsigned, 64> FirstActions;
197 FirstActions.resize(LandingPads.size());
198 SmallVector<CallSiteEntry, 64> CallSites;
199 computeCallSiteTable(CallSites, LandingPads, FirstActions);
201 MCSymbol *EHFuncBeginSym = Asm->getFunctionBegin();
202 MCSymbol *EHFuncEndSym = Asm->getFunctionEnd();
204 // Emit the number of table entries.
205 unsigned NumEntries = 0;
206 for (const CallSiteEntry &CSE : CallSites) {
208 continue; // Ignore gaps.
209 for (int Selector : CSE.LPad->TypeIds) {
210 // Ignore C++ filter clauses in SEH.
211 // FIXME: Implement cleanup clauses.
212 if (isCatchEHSelector(Selector))
215 NumEntries += CSE.LPad->SEHHandlers.size();
217 Asm->OutStreamer.EmitIntValue(NumEntries, 4);
219 // If there are no actions, we don't need to iterate again.
223 // Emit the four-label records for each call site entry. The table has to be
224 // sorted in layout order, and the call sites should already be sorted.
225 for (const CallSiteEntry &CSE : CallSites) {
226 // Ignore gaps. Unlike the Itanium model, unwinding through a frame without
227 // an EH table entry will propagate the exception rather than terminating
231 const LandingPadInfo *LPad = CSE.LPad;
233 // Compute the label range. We may reuse the function begin and end labels
234 // rather than forming new ones.
235 const MCExpr *Begin =
236 createImageRel32(CSE.BeginLabel ? CSE.BeginLabel : EHFuncBeginSym);
239 // The interval is half-open, so we have to add one to include the return
240 // address of the last invoke in the range.
241 End = MCBinaryExpr::CreateAdd(createImageRel32(CSE.EndLabel),
242 MCConstantExpr::Create(1, Asm->OutContext),
245 End = createImageRel32(EHFuncEndSym);
248 // Emit an entry for each action.
249 for (SEHHandler Handler : LPad->SEHHandlers) {
250 Asm->OutStreamer.EmitValue(Begin, 4);
251 Asm->OutStreamer.EmitValue(End, 4);
253 // Emit the filter or finally function pointer, if present. Otherwise,
254 // emit '1' to indicate a catch-all.
255 const Function *F = Handler.FilterOrFinally;
257 Asm->OutStreamer.EmitValue(createImageRel32(Asm->getSymbol(F)), 4);
259 Asm->OutStreamer.EmitIntValue(1, 4);
261 // Emit the recovery address, if present. Otherwise, this must be a
263 const BlockAddress *BA = Handler.RecoverBA;
265 Asm->OutStreamer.EmitValue(
266 createImageRel32(Asm->GetBlockAddressSymbol(BA)), 4);
268 Asm->OutStreamer.EmitIntValue(0, 4);
270 if (!LPad->SEHHandlers.empty())
273 // These aren't really type info globals, they are actually pointers to
274 // filter functions ordered by selector. The zero selector is used for
275 // cleanups, so slot zero corresponds to selector 1.
276 const std::vector<const GlobalValue *> &SelectorToFilter = MMI->getTypeInfos();
278 // Do a parallel iteration across typeids and clause labels, skipping filter
280 size_t NextClauseLabel = 0;
281 for (size_t I = 0, E = LPad->TypeIds.size(); I < E; ++I) {
282 // AddLandingPadInfo stores the clauses in reverse, but there is a FIXME
284 int Selector = LPad->TypeIds[E - I - 1];
286 // Ignore C++ filter clauses in SEH.
287 // FIXME: Implement cleanup clauses.
288 if (!isCatchEHSelector(Selector))
291 Asm->OutStreamer.EmitValue(Begin, 4);
292 Asm->OutStreamer.EmitValue(End, 4);
293 if (isCatchEHSelector(Selector)) {
294 assert(unsigned(Selector - 1) < SelectorToFilter.size());
295 const GlobalValue *TI = SelectorToFilter[Selector - 1];
296 if (TI) // Emit the filter function pointer.
297 Asm->OutStreamer.EmitValue(createImageRel32(Asm->getSymbol(TI)), 4);
298 else // Otherwise, this is a "catch i8* null", or catch all.
299 Asm->OutStreamer.EmitIntValue(1, 4);
301 MCSymbol *ClauseLabel = LPad->ClauseLabels[NextClauseLabel++];
302 Asm->OutStreamer.EmitValue(createImageRel32(ClauseLabel), 4);
307 void Win64Exception::emitCXXFrameHandler3Table(const MachineFunction *MF) {
308 const Function *F = MF->getFunction();
309 const Function *ParentF = MMI->getWinEHParent(F);
310 auto &OS = Asm->OutStreamer;
311 WinEHFuncInfo &FuncInfo = MMI->getWinEHFuncInfo(ParentF);
313 StringRef ParentLinkageName =
314 GlobalValue::getRealLinkageName(ParentF->getName());
316 MCSymbol *FuncInfoXData =
317 Asm->OutContext.GetOrCreateSymbol(Twine("$cppxdata$", ParentLinkageName));
318 OS.EmitValue(createImageRel32(FuncInfoXData), 4);
320 // The Itanium LSDA table sorts similar landing pads together to simplify the
321 // actions table, but we don't need that.
322 SmallVector<const LandingPadInfo *, 64> LandingPads;
323 const std::vector<LandingPadInfo> &PadInfos = MMI->getLandingPads();
324 LandingPads.reserve(PadInfos.size());
325 for (const auto &LP : PadInfos)
326 LandingPads.push_back(&LP);
329 computePadMap(LandingPads, PadMap);
331 // The end label of the previous invoke or nounwind try-range.
332 MCSymbol *LastLabel = Asm->getFunctionBegin();
334 // Whether there is a potentially throwing instruction (currently this means
335 // an ordinary call) between the end of the previous try-range and now.
336 bool SawPotentiallyThrowing = false;
338 int LastEHState = -2;
340 // The parent function and the catch handlers contribute to the 'ip2state'
342 for (const auto &MBB : *MF) {
343 for (const auto &MI : MBB) {
344 if (!MI.isEHLabel()) {
346 SawPotentiallyThrowing |= !callToNoUnwindFunction(&MI);
350 // End of the previous try-range?
351 MCSymbol *BeginLabel = MI.getOperand(0).getMCSymbol();
352 if (BeginLabel == LastLabel)
353 SawPotentiallyThrowing = false;
355 // Beginning of a new try-range?
356 RangeMapType::const_iterator L = PadMap.find(BeginLabel);
357 if (L == PadMap.end())
358 // Nope, it was just some random label.
361 const PadRange &P = L->second;
362 const LandingPadInfo *LandingPad = LandingPads[P.PadIndex];
363 assert(BeginLabel == LandingPad->BeginLabels[P.RangeIndex] &&
364 "Inconsistent landing pad map!");
366 if (SawPotentiallyThrowing) {
367 FuncInfo.IPToStateList.push_back(std::make_pair(LastLabel, -1));
368 SawPotentiallyThrowing = false;
372 if (LandingPad->WinEHState != LastEHState)
373 FuncInfo.IPToStateList.push_back(
374 std::make_pair(BeginLabel, LandingPad->WinEHState));
375 LastEHState = LandingPad->WinEHState;
376 LastLabel = LandingPad->EndLabels[P.RangeIndex];
380 // Defer emission until we've visited the parent function and all the catch
381 // handlers. Cleanups don't contribute to the ip2state table yet, so don't
383 if (ParentF != F && !FuncInfo.CatchHandlerMaxState.count(F))
385 ++FuncInfo.NumIPToStateFuncsVisited;
386 if (FuncInfo.NumIPToStateFuncsVisited != FuncInfo.CatchHandlerMaxState.size())
389 MCSymbol *UnwindMapXData = nullptr;
390 MCSymbol *TryBlockMapXData = nullptr;
391 MCSymbol *IPToStateXData = nullptr;
392 if (!FuncInfo.UnwindMap.empty())
393 UnwindMapXData = Asm->OutContext.GetOrCreateSymbol(
394 Twine("$stateUnwindMap$", ParentLinkageName));
395 if (!FuncInfo.TryBlockMap.empty())
396 TryBlockMapXData = Asm->OutContext.GetOrCreateSymbol(
397 Twine("$tryMap$", ParentLinkageName));
398 if (!FuncInfo.IPToStateList.empty())
399 IPToStateXData = Asm->OutContext.GetOrCreateSymbol(
400 Twine("$ip2state$", ParentLinkageName));
403 // uint32_t MagicNumber
405 // UnwindMapEntry *UnwindMap;
406 // uint32_t NumTryBlocks;
407 // TryBlockMapEntry *TryBlockMap;
408 // uint32_t IPMapEntries;
409 // IPToStateMapEntry *IPToStateMap;
410 // uint32_t UnwindHelp; // (x64/ARM only)
411 // ESTypeList *ESTypeList;
414 // EHFlags & 1 -> Synchronous exceptions only, no async exceptions.
415 // EHFlags & 2 -> ???
416 // EHFlags & 4 -> The function is noexcept(true), unwinding can't continue.
417 OS.EmitLabel(FuncInfoXData);
418 OS.EmitIntValue(0x19930522, 4); // MagicNumber
419 OS.EmitIntValue(FuncInfo.UnwindMap.size(), 4); // MaxState
420 OS.EmitValue(createImageRel32(UnwindMapXData), 4); // UnwindMap
421 OS.EmitIntValue(FuncInfo.TryBlockMap.size(), 4); // NumTryBlocks
422 OS.EmitValue(createImageRel32(TryBlockMapXData), 4); // TryBlockMap
423 OS.EmitIntValue(FuncInfo.IPToStateList.size(), 4); // IPMapEntries
424 OS.EmitValue(createImageRel32(IPToStateXData), 4); // IPToStateMap
425 OS.EmitIntValue(FuncInfo.UnwindHelpFrameOffset, 4); // UnwindHelp
426 OS.EmitIntValue(0, 4); // ESTypeList
427 OS.EmitIntValue(1, 4); // EHFlags
433 if (UnwindMapXData) {
434 OS.EmitLabel(UnwindMapXData);
435 for (const WinEHUnwindMapEntry &UME : FuncInfo.UnwindMap) {
436 OS.EmitIntValue(UME.ToState, 4); // ToState
437 OS.EmitValue(createImageRel32(UME.Cleanup), 4); // Action
444 // int32_t CatchHigh;
445 // int32_t NumCatches;
446 // HandlerType *HandlerArray;
448 if (TryBlockMapXData) {
449 OS.EmitLabel(TryBlockMapXData);
450 SmallVector<MCSymbol *, 1> HandlerMaps;
451 for (size_t I = 0, E = FuncInfo.TryBlockMap.size(); I != E; ++I) {
452 WinEHTryBlockMapEntry &TBME = FuncInfo.TryBlockMap[I];
453 MCSymbol *HandlerMapXData = nullptr;
455 if (!TBME.HandlerArray.empty())
457 Asm->OutContext.GetOrCreateSymbol(Twine("$handlerMap$")
460 .concat(ParentLinkageName));
462 HandlerMaps.push_back(HandlerMapXData);
465 for (WinEHHandlerType &HT : TBME.HandlerArray)
467 std::max(CatchHigh, FuncInfo.CatchHandlerMaxState[HT.Handler]);
469 assert(TBME.TryLow <= TBME.TryHigh);
470 OS.EmitIntValue(TBME.TryLow, 4); // TryLow
471 OS.EmitIntValue(TBME.TryHigh, 4); // TryHigh
472 OS.EmitIntValue(CatchHigh, 4); // CatchHigh
473 OS.EmitIntValue(TBME.HandlerArray.size(), 4); // NumCatches
474 OS.EmitValue(createImageRel32(HandlerMapXData), 4); // HandlerArray
477 for (size_t I = 0, E = FuncInfo.TryBlockMap.size(); I != E; ++I) {
478 WinEHTryBlockMapEntry &TBME = FuncInfo.TryBlockMap[I];
479 MCSymbol *HandlerMapXData = HandlerMaps[I];
480 if (!HandlerMapXData)
483 // int32_t Adjectives;
484 // TypeDescriptor *Type;
485 // int32_t CatchObjOffset;
486 // void (*Handler)();
487 // int32_t ParentFrameOffset; // x64 only
489 OS.EmitLabel(HandlerMapXData);
490 for (const WinEHHandlerType &HT : TBME.HandlerArray) {
491 MCSymbol *ParentFrameOffset =
492 Asm->OutContext.getOrCreateParentFrameOffsetSymbol(
493 GlobalValue::getRealLinkageName(HT.Handler->getName()));
494 const MCSymbolRefExpr *ParentFrameOffsetRef = MCSymbolRefExpr::Create(
495 ParentFrameOffset, MCSymbolRefExpr::VK_None, Asm->OutContext);
497 // Get the frame escape label with the offset of the catch object. If
498 // the index is -1, then there is no catch object, and we should emit an
499 // offset of zero, indicating that no copy will occur.
500 const MCExpr *FrameAllocOffsetRef = nullptr;
501 if (HT.CatchObjRecoverIdx >= 0) {
502 MCSymbol *FrameAllocOffset =
503 Asm->OutContext.getOrCreateFrameAllocSymbol(
504 GlobalValue::getRealLinkageName(ParentF->getName()),
505 HT.CatchObjRecoverIdx);
506 FrameAllocOffsetRef = MCSymbolRefExpr::Create(
507 FrameAllocOffset, MCSymbolRefExpr::VK_None, Asm->OutContext);
509 FrameAllocOffsetRef = MCConstantExpr::Create(0, Asm->OutContext);
512 OS.EmitIntValue(HT.Adjectives, 4); // Adjectives
513 OS.EmitValue(createImageRel32(HT.TypeDescriptor), 4); // Type
514 OS.EmitValue(FrameAllocOffsetRef, 4); // CatchObjOffset
515 OS.EmitValue(createImageRel32(HT.Handler), 4); // Handler
516 OS.EmitValue(ParentFrameOffsetRef, 4); // ParentFrameOffset
521 // IPToStateMapEntry {
525 if (IPToStateXData) {
526 OS.EmitLabel(IPToStateXData);
527 for (auto &IPStatePair : FuncInfo.IPToStateList) {
528 OS.EmitValue(createImageRel32(IPStatePair.first), 4); // IP
529 OS.EmitIntValue(IPStatePair.second, 4); // State