lib/CodeGen/StackMaps.cpp

   1 //===- StackMaps.cpp ------------------------------------------------------===//
   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/CodeGen/StackMaps.h"
  10 #include "llvm/ADT/DenseMapInfo.h"
  11 #include "llvm/ADT/STLExtras.h"
  12 #include "llvm/ADT/Twine.h"
  13 #include "llvm/CodeGen/AsmPrinter.h"
  14 #include "llvm/CodeGen/MachineFrameInfo.h"
  15 #include "llvm/CodeGen/MachineFunction.h"
  16 #include "llvm/CodeGen/MachineInstr.h"
  17 #include "llvm/CodeGen/MachineOperand.h"
  18 #include "llvm/CodeGen/TargetOpcodes.h"
  19 #include "llvm/CodeGen/TargetRegisterInfo.h"
  20 #include "llvm/CodeGen/TargetSubtargetInfo.h"
  21 #include "llvm/IR/DataLayout.h"
  22 #include "llvm/MC/MCContext.h"
  23 #include "llvm/MC/MCExpr.h"
  24 #include "llvm/MC/MCObjectFileInfo.h"
  25 #include "llvm/MC/MCRegisterInfo.h"
  26 #include "llvm/MC/MCStreamer.h"
  27 #include "llvm/Support/CommandLine.h"
  28 #include "llvm/Support/Debug.h"
  29 #include "llvm/Support/ErrorHandling.h"
  30 #include "llvm/Support/MathExtras.h"
  31 #include "llvm/Support/raw_ostream.h"
  32 #include <algorithm>
  33 #include <cassert>
  34 #include <cstdint>
  35 #include <iterator>
  36 #include <utility>
  37
  38 using namespace llvm;
  39
  40 #define DEBUG_TYPE "stackmaps"
  41
  42 static cl::opt<int> StackMapVersion(
  43     "stackmap-version", cl::init(3), cl::Hidden,
  44     cl::desc("Specify the stackmap encoding version (default = 3)"));
  45
  46 const char *StackMaps::WSMP = "Stack Maps: ";
  47
  48 StackMapOpers::StackMapOpers(const MachineInstr *MI)
  49   : MI(MI) {
  50   assert(getVarIdx() <= MI->getNumOperands() &&
  51          "invalid stackmap definition");
  52 }
  53
  54 PatchPointOpers::PatchPointOpers(const MachineInstr *MI)
  55     : MI(MI), HasDef(MI->getOperand(0).isReg() && MI->getOperand(0).isDef() &&
  56                      !MI->getOperand(0).isImplicit()) {
  57 #ifndef NDEBUG
  58   unsigned CheckStartIdx = 0, e = MI->getNumOperands();
  59   while (CheckStartIdx < e && MI->getOperand(CheckStartIdx).isReg() &&
  60          MI->getOperand(CheckStartIdx).isDef() &&
  61          !MI->getOperand(CheckStartIdx).isImplicit())
  62     ++CheckStartIdx;
  63
  64   assert(getMetaIdx() == CheckStartIdx &&
  65          "Unexpected additional definition in Patchpoint intrinsic.");
  66 #endif
  67 }
  68
  69 unsigned PatchPointOpers::getNextScratchIdx(unsigned StartIdx) const {
  70   if (!StartIdx)
  71     StartIdx = getVarIdx();
  72
  73   // Find the next scratch register (implicit def and early clobber)
  74   unsigned ScratchIdx = StartIdx, e = MI->getNumOperands();
  75   while (ScratchIdx < e &&
  76          !(MI->getOperand(ScratchIdx).isReg() &&
  77            MI->getOperand(ScratchIdx).isDef() &&
  78            MI->getOperand(ScratchIdx).isImplicit() &&
  79            MI->getOperand(ScratchIdx).isEarlyClobber()))
  80     ++ScratchIdx;
  81
  82   assert(ScratchIdx != e && "No scratch register available");
  83   return ScratchIdx;
  84 }
  85
  86 StackMaps::StackMaps(AsmPrinter &AP) : AP(AP) {
  87   if (StackMapVersion != 3)
  88     llvm_unreachable("Unsupported stackmap version!");
  89 }
  90
  91 /// Go up the super-register chain until we hit a valid dwarf register number.
  92 static unsigned getDwarfRegNum(unsigned Reg, const TargetRegisterInfo *TRI) {
  93   int RegNum = TRI->getDwarfRegNum(Reg, false);
  94   for (MCSuperRegIterator SR(Reg, TRI); SR.isValid() && RegNum < 0; ++SR)
  95     RegNum = TRI->getDwarfRegNum(*SR, false);
  96
  97   assert(RegNum >= 0 && "Invalid Dwarf register number.");
  98   return (unsigned)RegNum;
  99 }
 100
 101 MachineInstr::const_mop_iterator
 102 StackMaps::parseOperand(MachineInstr::const_mop_iterator MOI,
 103                         MachineInstr::const_mop_iterator MOE, LocationVec &Locs,
 104                         LiveOutVec &LiveOuts) const {
 105   const TargetRegisterInfo *TRI = AP.MF->getSubtarget().getRegisterInfo();
 106   if (MOI->isImm()) {
 107     switch (MOI->getImm()) {
 108     default:
 109       llvm_unreachable("Unrecognized operand type.");
 110     case StackMaps::DirectMemRefOp: {
 111       auto &DL = AP.MF->getDataLayout();
 112
 113       unsigned Size = DL.getPointerSizeInBits();
 114       assert((Size % 8) == 0 && "Need pointer size in bytes.");
 115       Size /= 8;
 116       unsigned Reg = (++MOI)->getReg();
 117       int64_t Imm = (++MOI)->getImm();
 118       Locs.emplace_back(StackMaps::Location::Direct, Size,
 119                         getDwarfRegNum(Reg, TRI), Imm);
 120       break;
 121     }
 122     case StackMaps::IndirectMemRefOp: {
 123       int64_t Size = (++MOI)->getImm();
 124       assert(Size > 0 && "Need a valid size for indirect memory locations.");
 125       unsigned Reg = (++MOI)->getReg();
 126       int64_t Imm = (++MOI)->getImm();
 127       Locs.emplace_back(StackMaps::Location::Indirect, Size,
 128                         getDwarfRegNum(Reg, TRI), Imm);
 129       break;
 130     }
 131     case StackMaps::ConstantOp: {
 132       ++MOI;
 133       assert(MOI->isImm() && "Expected constant operand.");
 134       int64_t Imm = MOI->getImm();
 135       Locs.emplace_back(Location::Constant, sizeof(int64_t), 0, Imm);
 136       break;
 137     }
 138     }
 139     return ++MOI;
 140   }
 141
 142   // The physical register number will ultimately be encoded as a DWARF regno.
 143   // The stack map also records the size of a spill slot that can hold the
 144   // register content. (The runtime can track the actual size of the data type
 145   // if it needs to.)
 146   if (MOI->isReg()) {
 147     // Skip implicit registers (this includes our scratch registers)
 148     if (MOI->isImplicit())
 149       return ++MOI;
 150
 151     assert(TargetRegisterInfo::isPhysicalRegister(MOI->getReg()) &&
 152            "Virtreg operands should have been rewritten before now.");
 153     const TargetRegisterClass *RC = TRI->getMinimalPhysRegClass(MOI->getReg());
 154     assert(!MOI->getSubReg() && "Physical subreg still around.");
 155
 156     unsigned Offset = 0;
 157     unsigned DwarfRegNum = getDwarfRegNum(MOI->getReg(), TRI);
 158     unsigned LLVMRegNum = TRI->getLLVMRegNum(DwarfRegNum, false);
 159     unsigned SubRegIdx = TRI->getSubRegIndex(LLVMRegNum, MOI->getReg());
 160     if (SubRegIdx)
 161       Offset = TRI->getSubRegIdxOffset(SubRegIdx);
 162
 163     Locs.emplace_back(Location::Register, TRI->getSpillSize(*RC),
 164                       DwarfRegNum, Offset);
 165     return ++MOI;
 166   }
 167
 168   if (MOI->isRegLiveOut())
 169     LiveOuts = parseRegisterLiveOutMask(MOI->getRegLiveOut());
 170
 171   return ++MOI;
 172 }
 173
 174 void StackMaps::print(raw_ostream &OS) {
 175   const TargetRegisterInfo *TRI =
 176       AP.MF ? AP.MF->getSubtarget().getRegisterInfo() : nullptr;
 177   OS << WSMP << "callsites:\n";
 178   for (const auto &CSI : CSInfos) {
 179     const LocationVec &CSLocs = CSI.Locations;
 180     const LiveOutVec &LiveOuts = CSI.LiveOuts;
 181
 182     OS << WSMP << "callsite " << CSI.ID << "\n";
 183     OS << WSMP << "  has " << CSLocs.size() << " locations\n";
 184
 185     unsigned Idx = 0;
 186     for (const auto &Loc : CSLocs) {
 187       OS << WSMP << "\t\tLoc " << Idx << ": ";
 188       switch (Loc.Type) {
 189       case Location::Unprocessed:
 190         OS << "<Unprocessed operand>";
 191         break;
 192       case Location::Register:
 193         OS << "Register ";
 194         if (TRI)
 195           OS << printReg(Loc.Reg, TRI);
 196         else
 197           OS << Loc.Reg;
 198         break;
 199       case Location::Direct:
 200         OS << "Direct ";
 201         if (TRI)
 202           OS << printReg(Loc.Reg, TRI);
 203         else
 204           OS << Loc.Reg;
 205         if (Loc.Offset)
 206           OS << " + " << Loc.Offset;
 207         break;
 208       case Location::Indirect:
 209         OS << "Indirect ";
 210         if (TRI)
 211           OS << printReg(Loc.Reg, TRI);
 212         else
 213           OS << Loc.Reg;
 214         OS << "+" << Loc.Offset;
 215         break;
 216       case Location::Constant:
 217         OS << "Constant " << Loc.Offset;
 218         break;
 219       case Location::ConstantIndex:
 220         OS << "Constant Index " << Loc.Offset;
 221         break;
 222       }
 223       OS << "\t[encoding: .byte " << Loc.Type << ", .byte 0"
 224          << ", .short " << Loc.Size << ", .short " << Loc.Reg << ", .short 0"
 225          << ", .int " << Loc.Offset << "]\n";
 226       Idx++;
 227     }
 228
 229     OS << WSMP << "\thas " << LiveOuts.size() << " live-out registers\n";
 230
 231     Idx = 0;
 232     for (const auto &LO : LiveOuts) {
 233       OS << WSMP << "\t\tLO " << Idx << ": ";
 234       if (TRI)
 235         OS << printReg(LO.Reg, TRI);
 236       else
 237         OS << LO.Reg;
 238       OS << "\t[encoding: .short " << LO.DwarfRegNum << ", .byte 0, .byte "
 239          << LO.Size << "]\n";
 240       Idx++;
 241     }
 242   }
 243 }
 244
 245 /// Create a live-out register record for the given register Reg.
 246 StackMaps::LiveOutReg
 247 StackMaps::createLiveOutReg(unsigned Reg, const TargetRegisterInfo *TRI) const {
 248   unsigned DwarfRegNum = getDwarfRegNum(Reg, TRI);
 249   unsigned Size = TRI->getSpillSize(*TRI->getMinimalPhysRegClass(Reg));
 250   return LiveOutReg(Reg, DwarfRegNum, Size);
 251 }
 252
 253 /// Parse the register live-out mask and return a vector of live-out registers
 254 /// that need to be recorded in the stackmap.
 255 StackMaps::LiveOutVec
 256 StackMaps::parseRegisterLiveOutMask(const uint32_t *Mask) const {
 257   assert(Mask && "No register mask specified");
 258   const TargetRegisterInfo *TRI = AP.MF->getSubtarget().getRegisterInfo();
 259   LiveOutVec LiveOuts;
 260
 261   // Create a LiveOutReg for each bit that is set in the register mask.
 262   for (unsigned Reg = 0, NumRegs = TRI->getNumRegs(); Reg != NumRegs; ++Reg)
 263     if ((Mask[Reg / 32] >> Reg % 32) & 1)
 264       LiveOuts.push_back(createLiveOutReg(Reg, TRI));
 265
 266   // We don't need to keep track of a register if its super-register is already
 267   // in the list. Merge entries that refer to the same dwarf register and use
 268   // the maximum size that needs to be spilled.
 269
 270   llvm::sort(LiveOuts, [](const LiveOutReg &LHS, const LiveOutReg &RHS) {
 271     // Only sort by the dwarf register number.
 272     return LHS.DwarfRegNum < RHS.DwarfRegNum;
 273   });
 274
 275   for (auto I = LiveOuts.begin(), E = LiveOuts.end(); I != E; ++I) {
 276     for (auto II = std::next(I); II != E; ++II) {
 277       if (I->DwarfRegNum != II->DwarfRegNum) {
 278         // Skip all the now invalid entries.
 279         I = --II;
 280         break;
 281       }
 282       I->Size = std::max(I->Size, II->Size);
 283       if (TRI->isSuperRegister(I->Reg, II->Reg))
 284         I->Reg = II->Reg;
 285       II->Reg = 0; // mark for deletion.
 286     }
 287   }
 288
 289   LiveOuts.erase(
 290       llvm::remove_if(LiveOuts,
 291                       [](const LiveOutReg &LO) { return LO.Reg == 0; }),
 292       LiveOuts.end());
 293
 294   return LiveOuts;
 295 }
 296
 297 void StackMaps::recordStackMapOpers(const MachineInstr &MI, uint64_t ID,
 298                                     MachineInstr::const_mop_iterator MOI,
 299                                     MachineInstr::const_mop_iterator MOE,
 300                                     bool recordResult) {
 301   MCContext &OutContext = AP.OutStreamer->getContext();
 302   MCSymbol *MILabel = OutContext.createTempSymbol();
 303   AP.OutStreamer->EmitLabel(MILabel);
 304
 305   LocationVec Locations;
 306   LiveOutVec LiveOuts;
 307
 308   if (recordResult) {
 309     assert(PatchPointOpers(&MI).hasDef() && "Stackmap has no return value.");
 310     parseOperand(MI.operands_begin(), std::next(MI.operands_begin()), Locations,
 311                  LiveOuts);
 312   }
 313
 314   // Parse operands.
 315   while (MOI != MOE) {
 316     MOI = parseOperand(MOI, MOE, Locations, LiveOuts);
 317   }
 318
 319   // Move large constants into the constant pool.
 320   for (auto &Loc : Locations) {
 321     // Constants are encoded as sign-extended integers.
 322     // -1 is directly encoded as .long 0xFFFFFFFF with no constant pool.
 323     if (Loc.Type == Location::Constant && !isInt<32>(Loc.Offset)) {
 324       Loc.Type = Location::ConstantIndex;
 325       // ConstPool is intentionally a MapVector of 'uint64_t's (as
 326       // opposed to 'int64_t's).  We should never be in a situation
 327       // where we have to insert either the tombstone or the empty
 328       // keys into a map, and for a DenseMap<uint64_t, T> these are
 329       // (uint64_t)0 and (uint64_t)-1.  They can be and are
 330       // represented using 32 bit integers.
 331       assert((uint64_t)Loc.Offset != DenseMapInfo<uint64_t>::getEmptyKey() &&
 332              (uint64_t)Loc.Offset !=
 333                  DenseMapInfo<uint64_t>::getTombstoneKey() &&
 334              "empty and tombstone keys should fit in 32 bits!");
 335       auto Result = ConstPool.insert(std::make_pair(Loc.Offset, Loc.Offset));
 336       Loc.Offset = Result.first - ConstPool.begin();
 337     }
 338   }
 339
 340   // Create an expression to calculate the offset of the callsite from function
 341   // entry.
 342   const MCExpr *CSOffsetExpr = MCBinaryExpr::createSub(
 343       MCSymbolRefExpr::create(MILabel, OutContext),
 344       MCSymbolRefExpr::create(AP.CurrentFnSymForSize, OutContext), OutContext);
 345
 346   CSInfos.emplace_back(CSOffsetExpr, ID, std::move(Locations),
 347                        std::move(LiveOuts));
 348
 349   // Record the stack size of the current function and update callsite count.
 350   const MachineFrameInfo &MFI = AP.MF->getFrameInfo();
 351   const TargetRegisterInfo *RegInfo = AP.MF->getSubtarget().getRegisterInfo();
 352   bool HasDynamicFrameSize =
 353       MFI.hasVarSizedObjects() || RegInfo->needsStackRealignment(*(AP.MF));
 354   uint64_t FrameSize = HasDynamicFrameSize ? UINT64_MAX : MFI.getStackSize();
 355
 356   auto CurrentIt = FnInfos.find(AP.CurrentFnSym);
 357   if (CurrentIt != FnInfos.end())
 358     CurrentIt->second.RecordCount++;
 359   else
 360     FnInfos.insert(std::make_pair(AP.CurrentFnSym, FunctionInfo(FrameSize)));
 361 }
 362
 363 void StackMaps::recordStackMap(const MachineInstr &MI) {
 364   assert(MI.getOpcode() == TargetOpcode::STACKMAP && "expected stackmap");
 365
 366   StackMapOpers opers(&MI);
 367   const int64_t ID = MI.getOperand(PatchPointOpers::IDPos).getImm();
 368   recordStackMapOpers(MI, ID, std::next(MI.operands_begin(), opers.getVarIdx()),
 369                       MI.operands_end());
 370 }
 371
 372 void StackMaps::recordPatchPoint(const MachineInstr &MI) {
 373   assert(MI.getOpcode() == TargetOpcode::PATCHPOINT && "expected patchpoint");
 374
 375   PatchPointOpers opers(&MI);
 376   const int64_t ID = opers.getID();
 377   auto MOI = std::next(MI.operands_begin(), opers.getStackMapStartIdx());
 378   recordStackMapOpers(MI, ID, MOI, MI.operands_end(),
 379                       opers.isAnyReg() && opers.hasDef());
 380
 381 #ifndef NDEBUG
 382   // verify anyregcc
 383   auto &Locations = CSInfos.back().Locations;
 384   if (opers.isAnyReg()) {
 385     unsigned NArgs = opers.getNumCallArgs();
 386     for (unsigned i = 0, e = (opers.hasDef() ? NArgs + 1 : NArgs); i != e; ++i)
 387       assert(Locations[i].Type == Location::Register &&
 388              "anyreg arg must be in reg.");
 389   }
 390 #endif
 391 }
 392
 393 void StackMaps::recordStatepoint(const MachineInstr &MI) {
 394   assert(MI.getOpcode() == TargetOpcode::STATEPOINT && "expected statepoint");
 395
 396   StatepointOpers opers(&MI);
 397   // Record all the deopt and gc operands (they're contiguous and run from the
 398   // initial index to the end of the operand list)
 399   const unsigned StartIdx = opers.getVarIdx();
 400   recordStackMapOpers(MI, opers.getID(), MI.operands_begin() + StartIdx,
 401                       MI.operands_end(), false);
 402 }
 403
 404 /// Emit the stackmap header.
 405 ///
 406 /// Header {
 407 ///   uint8  : Stack Map Version (currently 2)
 408 ///   uint8  : Reserved (expected to be 0)
 409 ///   uint16 : Reserved (expected to be 0)
 410 /// }
 411 /// uint32 : NumFunctions
 412 /// uint32 : NumConstants
 413 /// uint32 : NumRecords
 414 void StackMaps::emitStackmapHeader(MCStreamer &OS) {
 415   // Header.
 416   OS.EmitIntValue(StackMapVersion, 1); // Version.
 417   OS.EmitIntValue(0, 1);               // Reserved.
 418   OS.EmitIntValue(0, 2);               // Reserved.
 419
 420   // Num functions.
 421   LLVM_DEBUG(dbgs() << WSMP << "#functions = " << FnInfos.size() << '\n');
 422   OS.EmitIntValue(FnInfos.size(), 4);
 423   // Num constants.
 424   LLVM_DEBUG(dbgs() << WSMP << "#constants = " << ConstPool.size() << '\n');
 425   OS.EmitIntValue(ConstPool.size(), 4);
 426   // Num callsites.
 427   LLVM_DEBUG(dbgs() << WSMP << "#callsites = " << CSInfos.size() << '\n');
 428   OS.EmitIntValue(CSInfos.size(), 4);
 429 }
 430
 431 /// Emit the function frame record for each function.
 432 ///
 433 /// StkSizeRecord[NumFunctions] {
 434 ///   uint64 : Function Address
 435 ///   uint64 : Stack Size
 436 ///   uint64 : Record Count
 437 /// }
 438 void StackMaps::emitFunctionFrameRecords(MCStreamer &OS) {
 439   // Function Frame records.
 440   LLVM_DEBUG(dbgs() << WSMP << "functions:\n");
 441   for (auto const &FR : FnInfos) {
 442     LLVM_DEBUG(dbgs() << WSMP << "function addr: " << FR.first
 443                       << " frame size: " << FR.second.StackSize
 444                       << " callsite count: " << FR.second.RecordCount << '\n');
 445     OS.EmitSymbolValue(FR.first, 8);
 446     OS.EmitIntValue(FR.second.StackSize, 8);
 447     OS.EmitIntValue(FR.second.RecordCount, 8);
 448   }
 449 }
 450
 451 /// Emit the constant pool.
 452 ///
 453 /// int64  : Constants[NumConstants]
 454 void StackMaps::emitConstantPoolEntries(MCStreamer &OS) {
 455   // Constant pool entries.
 456   LLVM_DEBUG(dbgs() << WSMP << "constants:\n");
 457   for (const auto &ConstEntry : ConstPool) {
 458     LLVM_DEBUG(dbgs() << WSMP << ConstEntry.second << '\n');
 459     OS.EmitIntValue(ConstEntry.second, 8);
 460   }
 461 }
 462
 463 /// Emit the callsite info for each callsite.
 464 ///
 465 /// StkMapRecord[NumRecords] {
 466 ///   uint64 : PatchPoint ID
 467 ///   uint32 : Instruction Offset
 468 ///   uint16 : Reserved (record flags)
 469 ///   uint16 : NumLocations
 470 ///   Location[NumLocations] {
 471 ///     uint8  : Register | Direct | Indirect | Constant | ConstantIndex
 472 ///     uint8  : Size in Bytes
 473 ///     uint16 : Dwarf RegNum
 474 ///     int32  : Offset
 475 ///   }
 476 ///   uint16 : Padding
 477 ///   uint16 : NumLiveOuts
 478 ///   LiveOuts[NumLiveOuts] {
 479 ///     uint16 : Dwarf RegNum
 480 ///     uint8  : Reserved
 481 ///     uint8  : Size in Bytes
 482 ///   }
 483 ///   uint32 : Padding (only if required to align to 8 byte)
 484 /// }
 485 ///
 486 /// Location Encoding, Type, Value:
 487 ///   0x1, Register, Reg                 (value in register)
 488 ///   0x2, Direct, Reg + Offset          (frame index)
 489 ///   0x3, Indirect, [Reg + Offset]      (spilled value)
 490 ///   0x4, Constant, Offset              (small constant)
 491 ///   0x5, ConstIndex, Constants[Offset] (large constant)
 492 void StackMaps::emitCallsiteEntries(MCStreamer &OS) {
 493   LLVM_DEBUG(print(dbgs()));
 494   // Callsite entries.
 495   for (const auto &CSI : CSInfos) {
 496     const LocationVec &CSLocs = CSI.Locations;
 497     const LiveOutVec &LiveOuts = CSI.LiveOuts;
 498
 499     // Verify stack map entry. It's better to communicate a problem to the
 500     // runtime than crash in case of in-process compilation. Currently, we do
 501     // simple overflow checks, but we may eventually communicate other
 502     // compilation errors this way.
 503     if (CSLocs.size() > UINT16_MAX || LiveOuts.size() > UINT16_MAX) {
 504       OS.EmitIntValue(UINT64_MAX, 8); // Invalid ID.
 505       OS.EmitValue(CSI.CSOffsetExpr, 4);
 506       OS.EmitIntValue(0, 2); // Reserved.
 507       OS.EmitIntValue(0, 2); // 0 locations.
 508       OS.EmitIntValue(0, 2); // padding.
 509       OS.EmitIntValue(0, 2); // 0 live-out registers.
 510       OS.EmitIntValue(0, 4); // padding.
 511       continue;
 512     }
 513
 514     OS.EmitIntValue(CSI.ID, 8);
 515     OS.EmitValue(CSI.CSOffsetExpr, 4);
 516
 517     // Reserved for flags.
 518     OS.EmitIntValue(0, 2);
 519     OS.EmitIntValue(CSLocs.size(), 2);
 520
 521     for (const auto &Loc : CSLocs) {
 522       OS.EmitIntValue(Loc.Type, 1);
 523       OS.EmitIntValue(0, 1);  // Reserved
 524       OS.EmitIntValue(Loc.Size, 2);
 525       OS.EmitIntValue(Loc.Reg, 2);
 526       OS.EmitIntValue(0, 2);  // Reserved
 527       OS.EmitIntValue(Loc.Offset, 4);
 528     }
 529
 530     // Emit alignment to 8 byte.
 531     OS.EmitValueToAlignment(8);
 532
 533     // Num live-out registers and padding to align to 4 byte.
 534     OS.EmitIntValue(0, 2);
 535     OS.EmitIntValue(LiveOuts.size(), 2);
 536
 537     for (const auto &LO : LiveOuts) {
 538       OS.EmitIntValue(LO.DwarfRegNum, 2);
 539       OS.EmitIntValue(0, 1);
 540       OS.EmitIntValue(LO.Size, 1);
 541     }
 542     // Emit alignment to 8 byte.
 543     OS.EmitValueToAlignment(8);
 544   }
 545 }
 546
 547 /// Serialize the stackmap data.
 548 void StackMaps::serializeToStackMapSection() {
 549   (void)WSMP;
 550   // Bail out if there's no stack map data.
 551   assert((!CSInfos.empty() || ConstPool.empty()) &&
 552          "Expected empty constant pool too!");
 553   assert((!CSInfos.empty() || FnInfos.empty()) &&
 554          "Expected empty function record too!");
 555   if (CSInfos.empty())
 556     return;
 557
 558   MCContext &OutContext = AP.OutStreamer->getContext();
 559   MCStreamer &OS = *AP.OutStreamer;
 560
 561   // Create the section.
 562   MCSection *StackMapSection =
 563       OutContext.getObjectFileInfo()->getStackMapSection();
 564   OS.SwitchSection(StackMapSection);
 565
 566   // Emit a dummy symbol to force section inclusion.
 567   OS.EmitLabel(OutContext.getOrCreateSymbol(Twine("__LLVM_StackMaps")));
 568
 569   // Serialize data.
 570   LLVM_DEBUG(dbgs() << "********** Stack Map Output **********\n");
 571   emitStackmapHeader(OS);
 572   emitFunctionFrameRecords(OS);
 573   emitConstantPoolEntries(OS);
 574   emitCallsiteEntries(OS);
 575   OS.AddBlankLine();
 576
 577   // Clean up.
 578   CSInfos.clear();
 579   ConstPool.clear();
 580 }