1//===- lib/MC/MCWin64EH.cpp - MCWin64EH implementation --------------------===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8
9#include "llvm/MC/MCWin64EH.h"
10#include "llvm/ADT/Twine.h"
11#include "llvm/MC/MCContext.h"
12#include "llvm/MC/MCExpr.h"
13#include "llvm/MC/MCObjectFileInfo.h"
14#include "llvm/MC/MCObjectStreamer.h"
15#include "llvm/MC/MCSectionCOFF.h"
16#include "llvm/MC/MCStreamer.h"
17#include "llvm/MC/MCSymbol.h"
18#include "llvm/Support/Win64EH.h"
19
20using namespace llvm;
21
22// NOTE: All relocations generated here are 4-byte image-relative.
23
24static uint8_t CountOfUnwindCodes(std::vector<WinEH::Instruction> &Insns) {
25  uint8_t Count = 0;
26  for (const auto &I : Insns) {
27    switch (static_cast<Win64EH::UnwindOpcodes>(I.Operation)) {
28    default:
29      llvm_unreachable("Unsupported unwind code");
30    case Win64EH::UOP_PushNonVol:
31    case Win64EH::UOP_AllocSmall:
32    case Win64EH::UOP_SetFPReg:
33    case Win64EH::UOP_PushMachFrame:
34      Count += 1;
35      break;
36    case Win64EH::UOP_SaveNonVol:
37    case Win64EH::UOP_SaveXMM128:
38      Count += 2;
39      break;
40    case Win64EH::UOP_SaveNonVolBig:
41    case Win64EH::UOP_SaveXMM128Big:
42      Count += 3;
43      break;
44    case Win64EH::UOP_AllocLarge:
45      Count += (I.Offset > 512 * 1024 - 8) ? 3 : 2;
46      break;
47    }
48  }
49  return Count;
50}
51
52static void EmitAbsDifference(MCStreamer &Streamer, const MCSymbol *LHS,
53                              const MCSymbol *RHS) {
54  MCContext &Context = Streamer.getContext();
55  const MCExpr *Diff =
56      MCBinaryExpr::createSub(MCSymbolRefExpr::create(LHS, Context),
57                              MCSymbolRefExpr::create(RHS, Context), Context);
58  Streamer.emitValue(Diff, 1);
59}
60
61static void EmitUnwindCode(MCStreamer &streamer, const MCSymbol *begin,
62                           WinEH::Instruction &inst) {
63  uint8_t b2;
64  uint16_t w;
65  b2 = (inst.Operation & 0x0F);
66  switch (static_cast<Win64EH::UnwindOpcodes>(inst.Operation)) {
67  default:
68    llvm_unreachable("Unsupported unwind code");
69  case Win64EH::UOP_PushNonVol:
70    EmitAbsDifference(streamer, inst.Label, begin);
71    b2 |= (inst.Register & 0x0F) << 4;
72    streamer.emitInt8(b2);
73    break;
74  case Win64EH::UOP_AllocLarge:
75    EmitAbsDifference(streamer, inst.Label, begin);
76    if (inst.Offset > 512 * 1024 - 8) {
77      b2 |= 0x10;
78      streamer.emitInt8(b2);
79      w = inst.Offset & 0xFFF8;
80      streamer.emitInt16(w);
81      w = inst.Offset >> 16;
82    } else {
83      streamer.emitInt8(b2);
84      w = inst.Offset >> 3;
85    }
86    streamer.emitInt16(w);
87    break;
88  case Win64EH::UOP_AllocSmall:
89    b2 |= (((inst.Offset - 8) >> 3) & 0x0F) << 4;
90    EmitAbsDifference(streamer, inst.Label, begin);
91    streamer.emitInt8(b2);
92    break;
93  case Win64EH::UOP_SetFPReg:
94    EmitAbsDifference(streamer, inst.Label, begin);
95    streamer.emitInt8(b2);
96    break;
97  case Win64EH::UOP_SaveNonVol:
98  case Win64EH::UOP_SaveXMM128:
99    b2 |= (inst.Register & 0x0F) << 4;
100    EmitAbsDifference(streamer, inst.Label, begin);
101    streamer.emitInt8(b2);
102    w = inst.Offset >> 3;
103    if (inst.Operation == Win64EH::UOP_SaveXMM128)
104      w >>= 1;
105    streamer.emitInt16(w);
106    break;
107  case Win64EH::UOP_SaveNonVolBig:
108  case Win64EH::UOP_SaveXMM128Big:
109    b2 |= (inst.Register & 0x0F) << 4;
110    EmitAbsDifference(streamer, inst.Label, begin);
111    streamer.emitInt8(b2);
112    if (inst.Operation == Win64EH::UOP_SaveXMM128Big)
113      w = inst.Offset & 0xFFF0;
114    else
115      w = inst.Offset & 0xFFF8;
116    streamer.emitInt16(w);
117    w = inst.Offset >> 16;
118    streamer.emitInt16(w);
119    break;
120  case Win64EH::UOP_PushMachFrame:
121    if (inst.Offset == 1)
122      b2 |= 0x10;
123    EmitAbsDifference(streamer, inst.Label, begin);
124    streamer.emitInt8(b2);
125    break;
126  }
127}
128
129static void EmitSymbolRefWithOfs(MCStreamer &streamer,
130                                 const MCSymbol *Base,
131                                 const MCSymbol *Other) {
132  MCContext &Context = streamer.getContext();
133  const MCSymbolRefExpr *BaseRef = MCSymbolRefExpr::create(Base, Context);
134  const MCSymbolRefExpr *OtherRef = MCSymbolRefExpr::create(Other, Context);
135  const MCExpr *Ofs = MCBinaryExpr::createSub(OtherRef, BaseRef, Context);
136  const MCSymbolRefExpr *BaseRefRel = MCSymbolRefExpr::create(Base,
137                                              MCSymbolRefExpr::VK_COFF_IMGREL32,
138                                              Context);
139  streamer.emitValue(MCBinaryExpr::createAdd(BaseRefRel, Ofs, Context), 4);
140}
141
142static void EmitRuntimeFunction(MCStreamer &streamer,
143                                const WinEH::FrameInfo *info) {
144  MCContext &context = streamer.getContext();
145
146  streamer.emitValueToAlignment(4);
147  EmitSymbolRefWithOfs(streamer, info->Function, info->Begin);
148  EmitSymbolRefWithOfs(streamer, info->Function, info->End);
149  streamer.emitValue(MCSymbolRefExpr::create(info->Symbol,
150                                             MCSymbolRefExpr::VK_COFF_IMGREL32,
151                                             context), 4);
152}
153
154static void EmitUnwindInfo(MCStreamer &streamer, WinEH::FrameInfo *info) {
155  // If this UNWIND_INFO already has a symbol, it's already been emitted.
156  if (info->Symbol)
157    return;
158
159  MCContext &context = streamer.getContext();
160  MCSymbol *Label = context.createTempSymbol();
161
162  streamer.emitValueToAlignment(4);
163  streamer.emitLabel(Label);
164  info->Symbol = Label;
165
166  // Upper 3 bits are the version number (currently 1).
167  uint8_t flags = 0x01;
168  if (info->ChainedParent)
169    flags |= Win64EH::UNW_ChainInfo << 3;
170  else {
171    if (info->HandlesUnwind)
172      flags |= Win64EH::UNW_TerminateHandler << 3;
173    if (info->HandlesExceptions)
174      flags |= Win64EH::UNW_ExceptionHandler << 3;
175  }
176  streamer.emitInt8(flags);
177
178  if (info->PrologEnd)
179    EmitAbsDifference(streamer, info->PrologEnd, info->Begin);
180  else
181    streamer.emitInt8(0);
182
183  uint8_t numCodes = CountOfUnwindCodes(info->Instructions);
184  streamer.emitInt8(numCodes);
185
186  uint8_t frame = 0;
187  if (info->LastFrameInst >= 0) {
188    WinEH::Instruction &frameInst = info->Instructions[info->LastFrameInst];
189    assert(frameInst.Operation == Win64EH::UOP_SetFPReg);
190    frame = (frameInst.Register & 0x0F) | (frameInst.Offset & 0xF0);
191  }
192  streamer.emitInt8(frame);
193
194  // Emit unwind instructions (in reverse order).
195  uint8_t numInst = info->Instructions.size();
196  for (uint8_t c = 0; c < numInst; ++c) {
197    WinEH::Instruction inst = info->Instructions.back();
198    info->Instructions.pop_back();
199    EmitUnwindCode(streamer, info->Begin, inst);
200  }
201
202  // For alignment purposes, the instruction array will always have an even
203  // number of entries, with the final entry potentially unused (in which case
204  // the array will be one longer than indicated by the count of unwind codes
205  // field).
206  if (numCodes & 1) {
207    streamer.emitInt16(0);
208  }
209
210  if (flags & (Win64EH::UNW_ChainInfo << 3))
211    EmitRuntimeFunction(streamer, info->ChainedParent);
212  else if (flags &
213           ((Win64EH::UNW_TerminateHandler|Win64EH::UNW_ExceptionHandler) << 3))
214    streamer.emitValue(MCSymbolRefExpr::create(info->ExceptionHandler,
215                                              MCSymbolRefExpr::VK_COFF_IMGREL32,
216                                              context), 4);
217  else if (numCodes == 0) {
218    // The minimum size of an UNWIND_INFO struct is 8 bytes. If we're not
219    // a chained unwind info, if there is no handler, and if there are fewer
220    // than 2 slots used in the unwind code array, we have to pad to 8 bytes.
221    streamer.emitInt32(0);
222  }
223}
224
225void llvm::Win64EH::UnwindEmitter::Emit(MCStreamer &Streamer) const {
226  // Emit the unwind info structs first.
227  for (const auto &CFI : Streamer.getWinFrameInfos()) {
228    MCSection *XData = Streamer.getAssociatedXDataSection(CFI->TextSection);
229    Streamer.SwitchSection(XData);
230    ::EmitUnwindInfo(Streamer, CFI.get());
231  }
232
233  // Now emit RUNTIME_FUNCTION entries.
234  for (const auto &CFI : Streamer.getWinFrameInfos()) {
235    MCSection *PData = Streamer.getAssociatedPDataSection(CFI->TextSection);
236    Streamer.SwitchSection(PData);
237    EmitRuntimeFunction(Streamer, CFI.get());
238  }
239}
240
241void llvm::Win64EH::UnwindEmitter::EmitUnwindInfo(
242    MCStreamer &Streamer, WinEH::FrameInfo *info) const {
243  // Switch sections (the static function above is meant to be called from
244  // here and from Emit().
245  MCSection *XData = Streamer.getAssociatedXDataSection(info->TextSection);
246  Streamer.SwitchSection(XData);
247
248  ::EmitUnwindInfo(Streamer, info);
249}
250
251static int64_t GetAbsDifference(MCStreamer &Streamer, const MCSymbol *LHS,
252                                const MCSymbol *RHS) {
253  MCContext &Context = Streamer.getContext();
254  const MCExpr *Diff =
255      MCBinaryExpr::createSub(MCSymbolRefExpr::create(LHS, Context),
256                              MCSymbolRefExpr::create(RHS, Context), Context);
257  MCObjectStreamer *OS = (MCObjectStreamer *)(&Streamer);
258  // It should normally be possible to calculate the length of a function
259  // at this point, but it might not be possible in the presence of certain
260  // unusual constructs, like an inline asm with an alignment directive.
261  int64_t value;
262  if (!Diff->evaluateAsAbsolute(value, OS->getAssembler()))
263    report_fatal_error("Failed to evaluate function length in SEH unwind info");
264  return value;
265}
266
267static uint32_t
268ARM64CountOfUnwindCodes(const std::vector<WinEH::Instruction> &Insns) {
269  uint32_t Count = 0;
270  for (const auto &I : Insns) {
271    switch (static_cast<Win64EH::UnwindOpcodes>(I.Operation)) {
272    default:
273      llvm_unreachable("Unsupported ARM64 unwind code");
274    case Win64EH::UOP_AllocSmall:
275      Count += 1;
276      break;
277    case Win64EH::UOP_AllocMedium:
278      Count += 2;
279      break;
280    case Win64EH::UOP_AllocLarge:
281      Count += 4;
282      break;
283    case Win64EH::UOP_SaveFPLRX:
284      Count += 1;
285      break;
286    case Win64EH::UOP_SaveFPLR:
287      Count += 1;
288      break;
289    case Win64EH::UOP_SaveReg:
290      Count += 2;
291      break;
292    case Win64EH::UOP_SaveRegP:
293      Count += 2;
294      break;
295    case Win64EH::UOP_SaveRegPX:
296      Count += 2;
297      break;
298    case Win64EH::UOP_SaveRegX:
299      Count += 2;
300      break;
301    case Win64EH::UOP_SaveFReg:
302      Count += 2;
303      break;
304    case Win64EH::UOP_SaveFRegP:
305      Count += 2;
306      break;
307    case Win64EH::UOP_SaveFRegX:
308      Count += 2;
309      break;
310    case Win64EH::UOP_SaveFRegPX:
311      Count += 2;
312      break;
313    case Win64EH::UOP_SetFP:
314      Count += 1;
315      break;
316    case Win64EH::UOP_AddFP:
317      Count += 2;
318      break;
319    case Win64EH::UOP_Nop:
320      Count += 1;
321      break;
322    case Win64EH::UOP_End:
323      Count += 1;
324      break;
325    }
326  }
327  return Count;
328}
329
330// Unwind opcode encodings and restrictions are documented at
331// https://docs.microsoft.com/en-us/cpp/build/arm64-exception-handling
332static void ARM64EmitUnwindCode(MCStreamer &streamer, const MCSymbol *begin,
333                                WinEH::Instruction &inst) {
334  uint8_t b, reg;
335  switch (static_cast<Win64EH::UnwindOpcodes>(inst.Operation)) {
336  default:
337    llvm_unreachable("Unsupported ARM64 unwind code");
338  case Win64EH::UOP_AllocSmall:
339    b = (inst.Offset >> 4) & 0x1F;
340    streamer.emitInt8(b);
341    break;
342  case Win64EH::UOP_AllocMedium: {
343    uint16_t hw = (inst.Offset >> 4) & 0x7FF;
344    b = 0xC0;
345    b |= (hw >> 8);
346    streamer.emitInt8(b);
347    b = hw & 0xFF;
348    streamer.emitInt8(b);
349    break;
350  }
351  case Win64EH::UOP_AllocLarge: {
352    uint32_t w;
353    b = 0xE0;
354    streamer.emitInt8(b);
355    w = inst.Offset >> 4;
356    b = (w & 0x00FF0000) >> 16;
357    streamer.emitInt8(b);
358    b = (w & 0x0000FF00) >> 8;
359    streamer.emitInt8(b);
360    b = w & 0x000000FF;
361    streamer.emitInt8(b);
362    break;
363  }
364  case Win64EH::UOP_SetFP:
365    b = 0xE1;
366    streamer.emitInt8(b);
367    break;
368  case Win64EH::UOP_AddFP:
369    b = 0xE2;
370    streamer.emitInt8(b);
371    b = (inst.Offset >> 3);
372    streamer.emitInt8(b);
373    break;
374  case Win64EH::UOP_Nop:
375    b = 0xE3;
376    streamer.emitInt8(b);
377    break;
378  case Win64EH::UOP_SaveFPLRX:
379    b = 0x80;
380    b |= ((inst.Offset - 1) >> 3) & 0x3F;
381    streamer.emitInt8(b);
382    break;
383  case Win64EH::UOP_SaveFPLR:
384    b = 0x40;
385    b |= (inst.Offset >> 3) & 0x3F;
386    streamer.emitInt8(b);
387    break;
388  case Win64EH::UOP_SaveReg:
389    assert(inst.Register >= 19 && "Saved reg must be >= 19");
390    reg = inst.Register - 19;
391    b = 0xD0 | ((reg & 0xC) >> 2);
392    streamer.emitInt8(b);
393    b = ((reg & 0x3) << 6) | (inst.Offset >> 3);
394    streamer.emitInt8(b);
395    break;
396  case Win64EH::UOP_SaveRegX:
397    assert(inst.Register >= 19 && "Saved reg must be >= 19");
398    reg = inst.Register - 19;
399    b = 0xD4 | ((reg & 0x8) >> 3);
400    streamer.emitInt8(b);
401    b = ((reg & 0x7) << 5) | ((inst.Offset >> 3) - 1);
402    streamer.emitInt8(b);
403    break;
404  case Win64EH::UOP_SaveRegP:
405    assert(inst.Register >= 19 && "Saved registers must be >= 19");
406    reg = inst.Register - 19;
407    b = 0xC8 | ((reg & 0xC) >> 2);
408    streamer.emitInt8(b);
409    b = ((reg & 0x3) << 6) | (inst.Offset >> 3);
410    streamer.emitInt8(b);
411    break;
412  case Win64EH::UOP_SaveRegPX:
413    assert(inst.Register >= 19 && "Saved registers must be >= 19");
414    reg = inst.Register - 19;
415    b = 0xCC | ((reg & 0xC) >> 2);
416    streamer.emitInt8(b);
417    b = ((reg & 0x3) << 6) | ((inst.Offset >> 3) - 1);
418    streamer.emitInt8(b);
419    break;
420  case Win64EH::UOP_SaveFReg:
421    assert(inst.Register >= 8 && "Saved dreg must be >= 8");
422    reg = inst.Register - 8;
423    b = 0xDC | ((reg & 0x4) >> 2);
424    streamer.emitInt8(b);
425    b = ((reg & 0x3) << 6) | (inst.Offset >> 3);
426    streamer.emitInt8(b);
427    break;
428  case Win64EH::UOP_SaveFRegX:
429    assert(inst.Register >= 8 && "Saved dreg must be >= 8");
430    reg = inst.Register - 8;
431    b = 0xDE;
432    streamer.emitInt8(b);
433    b = ((reg & 0x7) << 5) | ((inst.Offset >> 3) - 1);
434    streamer.emitInt8(b);
435    break;
436  case Win64EH::UOP_SaveFRegP:
437    assert(inst.Register >= 8 && "Saved dregs must be >= 8");
438    reg = inst.Register - 8;
439    b = 0xD8 | ((reg & 0x4) >> 2);
440    streamer.emitInt8(b);
441    b = ((reg & 0x3) << 6) | (inst.Offset >> 3);
442    streamer.emitInt8(b);
443    break;
444  case Win64EH::UOP_SaveFRegPX:
445    assert(inst.Register >= 8 && "Saved dregs must be >= 8");
446    reg = inst.Register - 8;
447    b = 0xDA | ((reg & 0x4) >> 2);
448    streamer.emitInt8(b);
449    b = ((reg & 0x3) << 6) | ((inst.Offset >> 3) - 1);
450    streamer.emitInt8(b);
451    break;
452  case Win64EH::UOP_End:
453    b = 0xE4;
454    streamer.emitInt8(b);
455    break;
456  }
457}
458
459// Returns the epilog symbol of an epilog with the exact same unwind code
460// sequence, if it exists.  Otherwise, returns nulltpr.
461// EpilogInstrs - Unwind codes for the current epilog.
462// Epilogs - Epilogs that potentialy match the current epilog.
463static MCSymbol*
464FindMatchingEpilog(const std::vector<WinEH::Instruction>& EpilogInstrs,
465                   const std::vector<MCSymbol *>& Epilogs,
466                   const WinEH::FrameInfo *info) {
467  for (auto *EpilogStart : Epilogs) {
468    auto InstrsIter = info->EpilogMap.find(EpilogStart);
469    assert(InstrsIter != info->EpilogMap.end() &&
470           "Epilog not found in EpilogMap");
471    const auto &Instrs = InstrsIter->second;
472
473    if (Instrs.size() != EpilogInstrs.size())
474      continue;
475
476    bool Match = true;
477    for (unsigned i = 0; i < Instrs.size(); ++i)
478      if (Instrs[i].Operation != EpilogInstrs[i].Operation ||
479          Instrs[i].Offset != EpilogInstrs[i].Offset ||
480          Instrs[i].Register != EpilogInstrs[i].Register) {
481         Match = false;
482         break;
483      }
484
485    if (Match)
486      return EpilogStart;
487  }
488  return nullptr;
489}
490
491// Populate the .xdata section.  The format of .xdata on ARM64 is documented at
492// https://docs.microsoft.com/en-us/cpp/build/arm64-exception-handling
493static void ARM64EmitUnwindInfo(MCStreamer &streamer, WinEH::FrameInfo *info) {
494  // If this UNWIND_INFO already has a symbol, it's already been emitted.
495  if (info->Symbol)
496    return;
497
498  MCContext &context = streamer.getContext();
499  MCSymbol *Label = context.createTempSymbol();
500
501  streamer.emitValueToAlignment(4);
502  streamer.emitLabel(Label);
503  info->Symbol = Label;
504
505  int64_t RawFuncLength;
506  if (!info->FuncletOrFuncEnd) {
507    // FIXME: This is very wrong; we emit SEH data which covers zero bytes
508    // of code. But otherwise test/MC/AArch64/seh.s crashes.
509    RawFuncLength = 0;
510  } else {
511    // FIXME: GetAbsDifference tries to compute the length of the function
512    // immediately, before the whole file is emitted, but in general
513    // that's impossible: the size in bytes of certain assembler directives
514    // like .align and .fill is not known until the whole file is parsed and
515    // relaxations are applied. Currently, GetAbsDifference fails with a fatal
516    // error in that case. (We mostly don't hit this because inline assembly
517    // specifying those directives is rare, and we don't normally try to
518    // align loops on AArch64.)
519    //
520    // There are two potential approaches to delaying the computation. One,
521    // we could emit something like ".word (endfunc-beginfunc)/4+0x10800000",
522    // as long as we have some conservative estimate we could use to prove
523    // that we don't need to split the unwind data. Emitting the constant
524    // is straightforward, but there's no existing code for estimating the
525    // size of the function.
526    //
527    // The other approach would be to use a dedicated, relaxable fragment,
528    // which could grow to accommodate splitting the unwind data if
529    // necessary. This is more straightforward, since it automatically works
530    // without any new infrastructure, and it's consistent with how we handle
531    // relaxation in other contexts.  But it would require some refactoring
532    // to move parts of the pdata/xdata emission into the implementation of
533    // a fragment. We could probably continue to encode the unwind codes
534    // here, but we'd have to emit the pdata, the xdata header, and the
535    // epilogue scopes later, since they depend on whether the we need to
536    // split the unwind data.
537    RawFuncLength = GetAbsDifference(streamer, info->FuncletOrFuncEnd,
538                                     info->Begin);
539  }
540  if (RawFuncLength > 0xFFFFF)
541    report_fatal_error("SEH unwind data splitting not yet implemented");
542  uint32_t FuncLength = (uint32_t)RawFuncLength / 4;
543  uint32_t PrologCodeBytes = ARM64CountOfUnwindCodes(info->Instructions);
544  uint32_t TotalCodeBytes = PrologCodeBytes;
545
546  // Process epilogs.
547  MapVector<MCSymbol *, uint32_t> EpilogInfo;
548  // Epilogs processed so far.
549  std::vector<MCSymbol *> AddedEpilogs;
550
551  for (auto &I : info->EpilogMap) {
552    MCSymbol *EpilogStart = I.first;
553    auto &EpilogInstrs = I.second;
554    uint32_t CodeBytes = ARM64CountOfUnwindCodes(EpilogInstrs);
555
556    MCSymbol* MatchingEpilog =
557      FindMatchingEpilog(EpilogInstrs, AddedEpilogs, info);
558    if (MatchingEpilog) {
559      assert(EpilogInfo.find(MatchingEpilog) != EpilogInfo.end() &&
560             "Duplicate epilog not found");
561      EpilogInfo[EpilogStart] = EpilogInfo.lookup(MatchingEpilog);
562      // Clear the unwind codes in the EpilogMap, so that they don't get output
563      // in the logic below.
564      EpilogInstrs.clear();
565    } else {
566      EpilogInfo[EpilogStart] = TotalCodeBytes;
567      TotalCodeBytes += CodeBytes;
568      AddedEpilogs.push_back(EpilogStart);
569    }
570  }
571
572  // Code Words, Epilog count, E, X, Vers, Function Length
573  uint32_t row1 = 0x0;
574  uint32_t CodeWords = TotalCodeBytes / 4;
575  uint32_t CodeWordsMod = TotalCodeBytes % 4;
576  if (CodeWordsMod)
577    CodeWords++;
578  uint32_t EpilogCount = info->EpilogMap.size();
579  bool ExtensionWord = EpilogCount > 31 || TotalCodeBytes > 124;
580  if (!ExtensionWord) {
581    row1 |= (EpilogCount & 0x1F) << 22;
582    row1 |= (CodeWords & 0x1F) << 27;
583  }
584  // E is always 0 right now, TODO: packed epilog setup
585  if (info->HandlesExceptions) // X
586    row1 |= 1 << 20;
587  row1 |= FuncLength & 0x3FFFF;
588  streamer.emitInt32(row1);
589
590  // Extended Code Words, Extended Epilog Count
591  if (ExtensionWord) {
592    // FIXME: We should be able to split unwind info into multiple sections.
593    // FIXME: We should share epilog codes across epilogs, where possible,
594    // which would make this issue show up less frequently.
595    if (CodeWords > 0xFF || EpilogCount > 0xFFFF)
596      report_fatal_error("SEH unwind data splitting not yet implemented");
597    uint32_t row2 = 0x0;
598    row2 |= (CodeWords & 0xFF) << 16;
599    row2 |= (EpilogCount & 0xFFFF);
600    streamer.emitInt32(row2);
601  }
602
603  // Epilog Start Index, Epilog Start Offset
604  for (auto &I : EpilogInfo) {
605    MCSymbol *EpilogStart = I.first;
606    uint32_t EpilogIndex = I.second;
607    uint32_t EpilogOffset =
608        (uint32_t)GetAbsDifference(streamer, EpilogStart, info->Begin);
609    if (EpilogOffset)
610      EpilogOffset /= 4;
611    uint32_t row3 = EpilogOffset;
612    row3 |= (EpilogIndex & 0x3FF) << 22;
613    streamer.emitInt32(row3);
614  }
615
616  // Emit prolog unwind instructions (in reverse order).
617  uint8_t numInst = info->Instructions.size();
618  for (uint8_t c = 0; c < numInst; ++c) {
619    WinEH::Instruction inst = info->Instructions.back();
620    info->Instructions.pop_back();
621    ARM64EmitUnwindCode(streamer, info->Begin, inst);
622  }
623
624  // Emit epilog unwind instructions
625  for (auto &I : info->EpilogMap) {
626    auto &EpilogInstrs = I.second;
627    for (uint32_t i = 0; i < EpilogInstrs.size(); i++) {
628      WinEH::Instruction inst = EpilogInstrs[i];
629      ARM64EmitUnwindCode(streamer, info->Begin, inst);
630    }
631  }
632
633  int32_t BytesMod = CodeWords * 4 - TotalCodeBytes;
634  assert(BytesMod >= 0);
635  for (int i = 0; i < BytesMod; i++)
636    streamer.emitInt8(0xE3);
637
638  if (info->HandlesExceptions)
639    streamer.emitValue(
640        MCSymbolRefExpr::create(info->ExceptionHandler,
641                                MCSymbolRefExpr::VK_COFF_IMGREL32, context),
642        4);
643}
644
645static void ARM64EmitRuntimeFunction(MCStreamer &streamer,
646                                     const WinEH::FrameInfo *info) {
647  MCContext &context = streamer.getContext();
648
649  streamer.emitValueToAlignment(4);
650  EmitSymbolRefWithOfs(streamer, info->Function, info->Begin);
651  streamer.emitValue(MCSymbolRefExpr::create(info->Symbol,
652                                             MCSymbolRefExpr::VK_COFF_IMGREL32,
653                                             context),
654                     4);
655}
656
657void llvm::Win64EH::ARM64UnwindEmitter::Emit(MCStreamer &Streamer) const {
658  // Emit the unwind info structs first.
659  for (const auto &CFI : Streamer.getWinFrameInfos()) {
660    MCSection *XData = Streamer.getAssociatedXDataSection(CFI->TextSection);
661    Streamer.SwitchSection(XData);
662    ARM64EmitUnwindInfo(Streamer, CFI.get());
663  }
664
665  // Now emit RUNTIME_FUNCTION entries.
666  for (const auto &CFI : Streamer.getWinFrameInfos()) {
667    MCSection *PData = Streamer.getAssociatedPDataSection(CFI->TextSection);
668    Streamer.SwitchSection(PData);
669    ARM64EmitRuntimeFunction(Streamer, CFI.get());
670  }
671}
672
673void llvm::Win64EH::ARM64UnwindEmitter::EmitUnwindInfo(
674    MCStreamer &Streamer, WinEH::FrameInfo *info) const {
675  // Switch sections (the static function above is meant to be called from
676  // here and from Emit().
677  MCSection *XData = Streamer.getAssociatedXDataSection(info->TextSection);
678  Streamer.SwitchSection(XData);
679  ARM64EmitUnwindInfo(Streamer, info);
680}
681