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 NumEntries += CSE.LPad->SEHHandlers.size();
211 Asm->OutStreamer.EmitIntValue(NumEntries, 4);
213 // If there are no actions, we don't need to iterate again.
217 // Emit the four-label records for each call site entry. The table has to be
218 // sorted in layout order, and the call sites should already be sorted.
219 for (const CallSiteEntry &CSE : CallSites) {
220 // Ignore gaps. Unlike the Itanium model, unwinding through a frame without
221 // an EH table entry will propagate the exception rather than terminating
225 const LandingPadInfo *LPad = CSE.LPad;
227 // Compute the label range. We may reuse the function begin and end labels
228 // rather than forming new ones.
229 const MCExpr *Begin =
230 createImageRel32(CSE.BeginLabel ? CSE.BeginLabel : EHFuncBeginSym);
233 // The interval is half-open, so we have to add one to include the return
234 // address of the last invoke in the range.
235 End = MCBinaryExpr::CreateAdd(createImageRel32(CSE.EndLabel),
236 MCConstantExpr::Create(1, Asm->OutContext),
239 End = createImageRel32(EHFuncEndSym);
242 // Emit an entry for each action.
243 for (SEHHandler Handler : LPad->SEHHandlers) {
244 Asm->OutStreamer.EmitValue(Begin, 4);
245 Asm->OutStreamer.EmitValue(End, 4);
247 // Emit the filter or finally function pointer, if present. Otherwise,
248 // emit '1' to indicate a catch-all.
249 const Function *F = Handler.FilterOrFinally;
251 Asm->OutStreamer.EmitValue(createImageRel32(Asm->getSymbol(F)), 4);
253 Asm->OutStreamer.EmitIntValue(1, 4);
255 // Emit the recovery address, if present. Otherwise, this must be a
257 const BlockAddress *BA = Handler.RecoverBA;
259 Asm->OutStreamer.EmitValue(
260 createImageRel32(Asm->GetBlockAddressSymbol(BA)), 4);
262 Asm->OutStreamer.EmitIntValue(0, 4);
267 void Win64Exception::emitCXXFrameHandler3Table(const MachineFunction *MF) {
268 const Function *F = MF->getFunction();
269 const Function *ParentF = MMI->getWinEHParent(F);
270 auto &OS = Asm->OutStreamer;
271 WinEHFuncInfo &FuncInfo = MMI->getWinEHFuncInfo(ParentF);
273 StringRef ParentLinkageName =
274 GlobalValue::getRealLinkageName(ParentF->getName());
276 MCSymbol *FuncInfoXData =
277 Asm->OutContext.GetOrCreateSymbol(Twine("$cppxdata$", ParentLinkageName));
278 OS.EmitValue(createImageRel32(FuncInfoXData), 4);
280 // The Itanium LSDA table sorts similar landing pads together to simplify the
281 // actions table, but we don't need that.
282 SmallVector<const LandingPadInfo *, 64> LandingPads;
283 const std::vector<LandingPadInfo> &PadInfos = MMI->getLandingPads();
284 LandingPads.reserve(PadInfos.size());
285 for (const auto &LP : PadInfos)
286 LandingPads.push_back(&LP);
289 computePadMap(LandingPads, PadMap);
291 // The end label of the previous invoke or nounwind try-range.
292 MCSymbol *LastLabel = Asm->getFunctionBegin();
294 // Whether there is a potentially throwing instruction (currently this means
295 // an ordinary call) between the end of the previous try-range and now.
296 bool SawPotentiallyThrowing = false;
298 int LastEHState = -2;
300 // The parent function and the catch handlers contribute to the 'ip2state'
302 for (const auto &MBB : *MF) {
303 for (const auto &MI : MBB) {
304 if (!MI.isEHLabel()) {
306 SawPotentiallyThrowing |= !callToNoUnwindFunction(&MI);
310 // End of the previous try-range?
311 MCSymbol *BeginLabel = MI.getOperand(0).getMCSymbol();
312 if (BeginLabel == LastLabel)
313 SawPotentiallyThrowing = false;
315 // Beginning of a new try-range?
316 RangeMapType::const_iterator L = PadMap.find(BeginLabel);
317 if (L == PadMap.end())
318 // Nope, it was just some random label.
321 const PadRange &P = L->second;
322 const LandingPadInfo *LandingPad = LandingPads[P.PadIndex];
323 assert(BeginLabel == LandingPad->BeginLabels[P.RangeIndex] &&
324 "Inconsistent landing pad map!");
326 if (SawPotentiallyThrowing) {
327 FuncInfo.IPToStateList.push_back(std::make_pair(LastLabel, -1));
328 SawPotentiallyThrowing = false;
332 if (LandingPad->WinEHState != LastEHState)
333 FuncInfo.IPToStateList.push_back(
334 std::make_pair(BeginLabel, LandingPad->WinEHState));
335 LastEHState = LandingPad->WinEHState;
336 LastLabel = LandingPad->EndLabels[P.RangeIndex];
340 // Defer emission until we've visited the parent function and all the catch
341 // handlers. Cleanups don't contribute to the ip2state table yet, so don't
343 if (ParentF != F && !FuncInfo.CatchHandlerMaxState.count(F))
345 ++FuncInfo.NumIPToStateFuncsVisited;
346 if (FuncInfo.NumIPToStateFuncsVisited != FuncInfo.CatchHandlerMaxState.size())
349 MCSymbol *UnwindMapXData = nullptr;
350 MCSymbol *TryBlockMapXData = nullptr;
351 MCSymbol *IPToStateXData = nullptr;
352 if (!FuncInfo.UnwindMap.empty())
353 UnwindMapXData = Asm->OutContext.GetOrCreateSymbol(
354 Twine("$stateUnwindMap$", ParentLinkageName));
355 if (!FuncInfo.TryBlockMap.empty())
356 TryBlockMapXData = Asm->OutContext.GetOrCreateSymbol(
357 Twine("$tryMap$", ParentLinkageName));
358 if (!FuncInfo.IPToStateList.empty())
359 IPToStateXData = Asm->OutContext.GetOrCreateSymbol(
360 Twine("$ip2state$", ParentLinkageName));
363 // uint32_t MagicNumber
365 // UnwindMapEntry *UnwindMap;
366 // uint32_t NumTryBlocks;
367 // TryBlockMapEntry *TryBlockMap;
368 // uint32_t IPMapEntries;
369 // IPToStateMapEntry *IPToStateMap;
370 // uint32_t UnwindHelp; // (x64/ARM only)
371 // ESTypeList *ESTypeList;
374 // EHFlags & 1 -> Synchronous exceptions only, no async exceptions.
375 // EHFlags & 2 -> ???
376 // EHFlags & 4 -> The function is noexcept(true), unwinding can't continue.
377 OS.EmitLabel(FuncInfoXData);
378 OS.EmitIntValue(0x19930522, 4); // MagicNumber
379 OS.EmitIntValue(FuncInfo.UnwindMap.size(), 4); // MaxState
380 OS.EmitValue(createImageRel32(UnwindMapXData), 4); // UnwindMap
381 OS.EmitIntValue(FuncInfo.TryBlockMap.size(), 4); // NumTryBlocks
382 OS.EmitValue(createImageRel32(TryBlockMapXData), 4); // TryBlockMap
383 OS.EmitIntValue(FuncInfo.IPToStateList.size(), 4); // IPMapEntries
384 OS.EmitValue(createImageRel32(IPToStateXData), 4); // IPToStateMap
385 OS.EmitIntValue(FuncInfo.UnwindHelpFrameOffset, 4); // UnwindHelp
386 OS.EmitIntValue(0, 4); // ESTypeList
387 OS.EmitIntValue(1, 4); // EHFlags
393 if (UnwindMapXData) {
394 OS.EmitLabel(UnwindMapXData);
395 for (const WinEHUnwindMapEntry &UME : FuncInfo.UnwindMap) {
396 OS.EmitIntValue(UME.ToState, 4); // ToState
397 OS.EmitValue(createImageRel32(UME.Cleanup), 4); // Action
404 // int32_t CatchHigh;
405 // int32_t NumCatches;
406 // HandlerType *HandlerArray;
408 if (TryBlockMapXData) {
409 OS.EmitLabel(TryBlockMapXData);
410 SmallVector<MCSymbol *, 1> HandlerMaps;
411 for (size_t I = 0, E = FuncInfo.TryBlockMap.size(); I != E; ++I) {
412 WinEHTryBlockMapEntry &TBME = FuncInfo.TryBlockMap[I];
413 MCSymbol *HandlerMapXData = nullptr;
415 if (!TBME.HandlerArray.empty())
417 Asm->OutContext.GetOrCreateSymbol(Twine("$handlerMap$")
420 .concat(ParentLinkageName));
422 HandlerMaps.push_back(HandlerMapXData);
425 for (WinEHHandlerType &HT : TBME.HandlerArray)
427 std::max(CatchHigh, FuncInfo.CatchHandlerMaxState[HT.Handler]);
429 assert(TBME.TryLow <= TBME.TryHigh);
430 assert(CatchHigh > TBME.TryHigh);
431 OS.EmitIntValue(TBME.TryLow, 4); // TryLow
432 OS.EmitIntValue(TBME.TryHigh, 4); // TryHigh
433 OS.EmitIntValue(CatchHigh, 4); // CatchHigh
434 OS.EmitIntValue(TBME.HandlerArray.size(), 4); // NumCatches
435 OS.EmitValue(createImageRel32(HandlerMapXData), 4); // HandlerArray
438 for (size_t I = 0, E = FuncInfo.TryBlockMap.size(); I != E; ++I) {
439 WinEHTryBlockMapEntry &TBME = FuncInfo.TryBlockMap[I];
440 MCSymbol *HandlerMapXData = HandlerMaps[I];
441 if (!HandlerMapXData)
444 // int32_t Adjectives;
445 // TypeDescriptor *Type;
446 // int32_t CatchObjOffset;
447 // void (*Handler)();
448 // int32_t ParentFrameOffset; // x64 only
450 OS.EmitLabel(HandlerMapXData);
451 for (const WinEHHandlerType &HT : TBME.HandlerArray) {
452 MCSymbol *ParentFrameOffset =
453 Asm->OutContext.getOrCreateParentFrameOffsetSymbol(
454 GlobalValue::getRealLinkageName(HT.Handler->getName()));
455 const MCSymbolRefExpr *ParentFrameOffsetRef = MCSymbolRefExpr::Create(
456 ParentFrameOffset, MCSymbolRefExpr::VK_None, Asm->OutContext);
458 // Get the frame escape label with the offset of the catch object. If
459 // the index is -1, then there is no catch object, and we should emit an
460 // offset of zero, indicating that no copy will occur.
461 const MCExpr *FrameAllocOffsetRef = nullptr;
462 if (HT.CatchObjRecoverIdx >= 0) {
463 MCSymbol *FrameAllocOffset =
464 Asm->OutContext.getOrCreateFrameAllocSymbol(
465 GlobalValue::getRealLinkageName(ParentF->getName()),
466 HT.CatchObjRecoverIdx);
467 FrameAllocOffsetRef = MCSymbolRefExpr::Create(
468 FrameAllocOffset, MCSymbolRefExpr::VK_None, Asm->OutContext);
470 FrameAllocOffsetRef = MCConstantExpr::Create(0, Asm->OutContext);
473 OS.EmitIntValue(HT.Adjectives, 4); // Adjectives
474 OS.EmitValue(createImageRel32(HT.TypeDescriptor), 4); // Type
475 OS.EmitValue(FrameAllocOffsetRef, 4); // CatchObjOffset
476 OS.EmitValue(createImageRel32(HT.Handler), 4); // Handler
477 OS.EmitValue(ParentFrameOffsetRef, 4); // ParentFrameOffset
482 // IPToStateMapEntry {
486 if (IPToStateXData) {
487 OS.EmitLabel(IPToStateXData);
488 for (auto &IPStatePair : FuncInfo.IPToStateList) {
489 OS.EmitValue(createImageRel32(IPStatePair.first), 4); // IP
490 OS.EmitIntValue(IPStatePair.second, 4); // State