StackMaps.cpp revision 302408 
1//===---------------------------- StackMaps.cpp ---------------------------===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9
10#include "llvm/CodeGen/StackMaps.h"
11#include "llvm/CodeGen/AsmPrinter.h"
12#include "llvm/CodeGen/MachineFrameInfo.h"
13#include "llvm/CodeGen/MachineFunction.h"
14#include "llvm/CodeGen/MachineInstr.h"
15#include "llvm/IR/DataLayout.h"
16#include "llvm/MC/MCContext.h"
17#include "llvm/MC/MCExpr.h"
18#include "llvm/MC/MCObjectFileInfo.h"
19#include "llvm/MC/MCSectionMachO.h"
20#include "llvm/MC/MCStreamer.h"
21#include "llvm/Support/CommandLine.h"
22#include "llvm/Target/TargetMachine.h"
23#include "llvm/Target/TargetOpcodes.h"
24#include "llvm/Target/TargetRegisterInfo.h"
25#include "llvm/Target/TargetSubtargetInfo.h"
26#include <iterator>
27
28using namespace llvm;
29
30#define DEBUG_TYPE "stackmaps"
31
32static cl::opt<int> StackMapVersion(
33    "stackmap-version", cl::init(1),
34    cl::desc("Specify the stackmap encoding version (default = 1)"));
35
36const char *StackMaps::WSMP = "Stack Maps: ";
37
38PatchPointOpers::PatchPointOpers(const MachineInstr *MI)
39    : MI(MI), HasDef(MI->getOperand(0).isReg() && MI->getOperand(0).isDef() &&
40                     !MI->getOperand(0).isImplicit()),
41      IsAnyReg(MI->getOperand(getMetaIdx(CCPos)).getImm() ==
42               CallingConv::AnyReg) {
43#ifndef NDEBUG
44  unsigned CheckStartIdx = 0, e = MI->getNumOperands();
45  while (CheckStartIdx < e && MI->getOperand(CheckStartIdx).isReg() &&
46         MI->getOperand(CheckStartIdx).isDef() &&
47         !MI->getOperand(CheckStartIdx).isImplicit())
48    ++CheckStartIdx;
49
50  assert(getMetaIdx() == CheckStartIdx &&
51         "Unexpected additional definition in Patchpoint intrinsic.");
52#endif
53}
54
55unsigned PatchPointOpers::getNextScratchIdx(unsigned StartIdx) const {
56  if (!StartIdx)
57    StartIdx = getVarIdx();
58
59  // Find the next scratch register (implicit def and early clobber)
60  unsigned ScratchIdx = StartIdx, e = MI->getNumOperands();
61  while (ScratchIdx < e &&
62         !(MI->getOperand(ScratchIdx).isReg() &&
63           MI->getOperand(ScratchIdx).isDef() &&
64           MI->getOperand(ScratchIdx).isImplicit() &&
65           MI->getOperand(ScratchIdx).isEarlyClobber()))
66    ++ScratchIdx;
67
68  assert(ScratchIdx != e && "No scratch register available");
69  return ScratchIdx;
70}
71
72StackMaps::StackMaps(AsmPrinter &AP) : AP(AP) {
73  if (StackMapVersion != 1)
74    llvm_unreachable("Unsupported stackmap version!");
75}
76
77/// Go up the super-register chain until we hit a valid dwarf register number.
78static unsigned getDwarfRegNum(unsigned Reg, const TargetRegisterInfo *TRI) {
79  int RegNum = TRI->getDwarfRegNum(Reg, false);
80  for (MCSuperRegIterator SR(Reg, TRI); SR.isValid() && RegNum < 0; ++SR)
81    RegNum = TRI->getDwarfRegNum(*SR, false);
82
83  assert(RegNum >= 0 && "Invalid Dwarf register number.");
84  return (unsigned)RegNum;
85}
86
87MachineInstr::const_mop_iterator
88StackMaps::parseOperand(MachineInstr::const_mop_iterator MOI,
89                        MachineInstr::const_mop_iterator MOE, LocationVec &Locs,
90                        LiveOutVec &LiveOuts) const {
91  const TargetRegisterInfo *TRI = AP.MF->getSubtarget().getRegisterInfo();
92  if (MOI->isImm()) {
93    switch (MOI->getImm()) {
94    default:
95      llvm_unreachable("Unrecognized operand type.");
96    case StackMaps::DirectMemRefOp: {
97      auto &DL = AP.MF->getDataLayout();
98
99      unsigned Size = DL.getPointerSizeInBits();
100      assert((Size % 8) == 0 && "Need pointer size in bytes.");
101      Size /= 8;
102      unsigned Reg = (++MOI)->getReg();
103      int64_t Imm = (++MOI)->getImm();
104      Locs.emplace_back(StackMaps::Location::Direct, Size,
105                        getDwarfRegNum(Reg, TRI), Imm);
106      break;
107    }
108    case StackMaps::IndirectMemRefOp: {
109      int64_t Size = (++MOI)->getImm();
110      assert(Size > 0 && "Need a valid size for indirect memory locations.");
111      unsigned Reg = (++MOI)->getReg();
112      int64_t Imm = (++MOI)->getImm();
113      Locs.emplace_back(StackMaps::Location::Indirect, Size,
114                        getDwarfRegNum(Reg, TRI), Imm);
115      break;
116    }
117    case StackMaps::ConstantOp: {
118      ++MOI;
119      assert(MOI->isImm() && "Expected constant operand.");
120      int64_t Imm = MOI->getImm();
121      Locs.emplace_back(Location::Constant, sizeof(int64_t), 0, Imm);
122      break;
123    }
124    }
125    return ++MOI;
126  }
127
128  // The physical register number will ultimately be encoded as a DWARF regno.
129  // The stack map also records the size of a spill slot that can hold the
130  // register content. (The runtime can track the actual size of the data type
131  // if it needs to.)
132  if (MOI->isReg()) {
133    // Skip implicit registers (this includes our scratch registers)
134    if (MOI->isImplicit())
135      return ++MOI;
136
137    assert(TargetRegisterInfo::isPhysicalRegister(MOI->getReg()) &&
138           "Virtreg operands should have been rewritten before now.");
139    const TargetRegisterClass *RC = TRI->getMinimalPhysRegClass(MOI->getReg());
140    assert(!MOI->getSubReg() && "Physical subreg still around.");
141
142    unsigned Offset = 0;
143    unsigned DwarfRegNum = getDwarfRegNum(MOI->getReg(), TRI);
144    unsigned LLVMRegNum = TRI->getLLVMRegNum(DwarfRegNum, false);
145    unsigned SubRegIdx = TRI->getSubRegIndex(LLVMRegNum, MOI->getReg());
146    if (SubRegIdx)
147      Offset = TRI->getSubRegIdxOffset(SubRegIdx);
148
149    Locs.emplace_back(Location::Register, RC->getSize(), DwarfRegNum, Offset);
150    return ++MOI;
151  }
152
153  if (MOI->isRegLiveOut())
154    LiveOuts = parseRegisterLiveOutMask(MOI->getRegLiveOut());
155
156  return ++MOI;
157}
158
159void StackMaps::print(raw_ostream &OS) {
160  const TargetRegisterInfo *TRI =
161      AP.MF ? AP.MF->getSubtarget().getRegisterInfo() : nullptr;
162  OS << WSMP << "callsites:\n";
163  for (const auto &CSI : CSInfos) {
164    const LocationVec &CSLocs = CSI.Locations;
165    const LiveOutVec &LiveOuts = CSI.LiveOuts;
166
167    OS << WSMP << "callsite " << CSI.ID << "\n";
168    OS << WSMP << "  has " << CSLocs.size() << " locations\n";
169
170    unsigned Idx = 0;
171    for (const auto &Loc : CSLocs) {
172      OS << WSMP << "\t\tLoc " << Idx << ": ";
173      switch (Loc.Type) {
174      case Location::Unprocessed:
175        OS << "<Unprocessed operand>";
176        break;
177      case Location::Register:
178        OS << "Register ";
179        if (TRI)
180          OS << TRI->getName(Loc.Reg);
181        else
182          OS << Loc.Reg;
183        break;
184      case Location::Direct:
185        OS << "Direct ";
186        if (TRI)
187          OS << TRI->getName(Loc.Reg);
188        else
189          OS << Loc.Reg;
190        if (Loc.Offset)
191          OS << " + " << Loc.Offset;
192        break;
193      case Location::Indirect:
194        OS << "Indirect ";
195        if (TRI)
196          OS << TRI->getName(Loc.Reg);
197        else
198          OS << Loc.Reg;
199        OS << "+" << Loc.Offset;
200        break;
201      case Location::Constant:
202        OS << "Constant " << Loc.Offset;
203        break;
204      case Location::ConstantIndex:
205        OS << "Constant Index " << Loc.Offset;
206        break;
207      }
208      OS << "\t[encoding: .byte " << Loc.Type << ", .byte " << Loc.Size
209         << ", .short " << Loc.Reg << ", .int " << Loc.Offset << "]\n";
210      Idx++;
211    }
212
213    OS << WSMP << "\thas " << LiveOuts.size() << " live-out registers\n";
214
215    Idx = 0;
216    for (const auto &LO : LiveOuts) {
217      OS << WSMP << "\t\tLO " << Idx << ": ";
218      if (TRI)
219        OS << TRI->getName(LO.Reg);
220      else
221        OS << LO.Reg;
222      OS << "\t[encoding: .short " << LO.DwarfRegNum << ", .byte 0, .byte "
223         << LO.Size << "]\n";
224      Idx++;
225    }
226  }
227}
228
229/// Create a live-out register record for the given register Reg.
230StackMaps::LiveOutReg
231StackMaps::createLiveOutReg(unsigned Reg, const TargetRegisterInfo *TRI) const {
232  unsigned DwarfRegNum = getDwarfRegNum(Reg, TRI);
233  unsigned Size = TRI->getMinimalPhysRegClass(Reg)->getSize();
234  return LiveOutReg(Reg, DwarfRegNum, Size);
235}
236
237/// Parse the register live-out mask and return a vector of live-out registers
238/// that need to be recorded in the stackmap.
239StackMaps::LiveOutVec
240StackMaps::parseRegisterLiveOutMask(const uint32_t *Mask) const {
241  assert(Mask && "No register mask specified");
242  const TargetRegisterInfo *TRI = AP.MF->getSubtarget().getRegisterInfo();
243  LiveOutVec LiveOuts;
244
245  // Create a LiveOutReg for each bit that is set in the register mask.
246  for (unsigned Reg = 0, NumRegs = TRI->getNumRegs(); Reg != NumRegs; ++Reg)
247    if ((Mask[Reg / 32] >> Reg % 32) & 1)
248      LiveOuts.push_back(createLiveOutReg(Reg, TRI));
249
250  // We don't need to keep track of a register if its super-register is already
251  // in the list. Merge entries that refer to the same dwarf register and use
252  // the maximum size that needs to be spilled.
253
254  std::sort(LiveOuts.begin(), LiveOuts.end(),
255            [](const LiveOutReg &LHS, const LiveOutReg &RHS) {
256              // Only sort by the dwarf register number.
257              return LHS.DwarfRegNum < RHS.DwarfRegNum;
258            });
259
260  for (auto I = LiveOuts.begin(), E = LiveOuts.end(); I != E; ++I) {
261    for (auto II = std::next(I); II != E; ++II) {
262      if (I->DwarfRegNum != II->DwarfRegNum) {
263        // Skip all the now invalid entries.
264        I = --II;
265        break;
266      }
267      I->Size = std::max(I->Size, II->Size);
268      if (TRI->isSuperRegister(I->Reg, II->Reg))
269        I->Reg = II->Reg;
270      II->Reg = 0; // mark for deletion.
271    }
272  }
273
274  LiveOuts.erase(
275      std::remove_if(LiveOuts.begin(), LiveOuts.end(),
276                     [](const LiveOutReg &LO) { return LO.Reg == 0; }),
277      LiveOuts.end());
278
279  return LiveOuts;
280}
281
282void StackMaps::recordStackMapOpers(const MachineInstr &MI, uint64_t ID,
283                                    MachineInstr::const_mop_iterator MOI,
284                                    MachineInstr::const_mop_iterator MOE,
285                                    bool recordResult) {
286
287  MCContext &OutContext = AP.OutStreamer->getContext();
288  MCSymbol *MILabel = OutContext.createTempSymbol();
289  AP.OutStreamer->EmitLabel(MILabel);
290
291  LocationVec Locations;
292  LiveOutVec LiveOuts;
293
294  if (recordResult) {
295    assert(PatchPointOpers(&MI).hasDef() && "Stackmap has no return value.");
296    parseOperand(MI.operands_begin(), std::next(MI.operands_begin()), Locations,
297                 LiveOuts);
298  }
299
300  // Parse operands.
301  while (MOI != MOE) {
302    MOI = parseOperand(MOI, MOE, Locations, LiveOuts);
303  }
304
305  // Move large constants into the constant pool.
306  for (auto &Loc : Locations) {
307    // Constants are encoded as sign-extended integers.
308    // -1 is directly encoded as .long 0xFFFFFFFF with no constant pool.
309    if (Loc.Type == Location::Constant && !isInt<32>(Loc.Offset)) {
310      Loc.Type = Location::ConstantIndex;
311      // ConstPool is intentionally a MapVector of 'uint64_t's (as
312      // opposed to 'int64_t's).  We should never be in a situation
313      // where we have to insert either the tombstone or the empty
314      // keys into a map, and for a DenseMap<uint64_t, T> these are
315      // (uint64_t)0 and (uint64_t)-1.  They can be and are
316      // represented using 32 bit integers.
317      assert((uint64_t)Loc.Offset != DenseMapInfo<uint64_t>::getEmptyKey() &&
318             (uint64_t)Loc.Offset !=
319                 DenseMapInfo<uint64_t>::getTombstoneKey() &&
320             "empty and tombstone keys should fit in 32 bits!");
321      auto Result = ConstPool.insert(std::make_pair(Loc.Offset, Loc.Offset));
322      Loc.Offset = Result.first - ConstPool.begin();
323    }
324  }
325
326  // Create an expression to calculate the offset of the callsite from function
327  // entry.
328  const MCExpr *CSOffsetExpr = MCBinaryExpr::createSub(
329      MCSymbolRefExpr::create(MILabel, OutContext),
330      MCSymbolRefExpr::create(AP.CurrentFnSymForSize, OutContext), OutContext);
331
332  CSInfos.emplace_back(CSOffsetExpr, ID, std::move(Locations),
333                       std::move(LiveOuts));
334
335  // Record the stack size of the current function.
336  const MachineFrameInfo *MFI = AP.MF->getFrameInfo();
337  const TargetRegisterInfo *RegInfo = AP.MF->getSubtarget().getRegisterInfo();
338  bool HasDynamicFrameSize =
339      MFI->hasVarSizedObjects() || RegInfo->needsStackRealignment(*(AP.MF));
340  FnStackSize[AP.CurrentFnSym] =
341      HasDynamicFrameSize ? UINT64_MAX : MFI->getStackSize();
342}
343
344void StackMaps::recordStackMap(const MachineInstr &MI) {
345  assert(MI.getOpcode() == TargetOpcode::STACKMAP && "expected stackmap");
346
347  int64_t ID = MI.getOperand(0).getImm();
348  recordStackMapOpers(MI, ID, std::next(MI.operands_begin(), 2),
349                      MI.operands_end());
350}
351
352void StackMaps::recordPatchPoint(const MachineInstr &MI) {
353  assert(MI.getOpcode() == TargetOpcode::PATCHPOINT && "expected patchpoint");
354
355  PatchPointOpers opers(&MI);
356  int64_t ID = opers.getMetaOper(PatchPointOpers::IDPos).getImm();
357
358  auto MOI = std::next(MI.operands_begin(), opers.getStackMapStartIdx());
359  recordStackMapOpers(MI, ID, MOI, MI.operands_end(),
360                      opers.isAnyReg() && opers.hasDef());
361
362#ifndef NDEBUG
363  // verify anyregcc
364  auto &Locations = CSInfos.back().Locations;
365  if (opers.isAnyReg()) {
366    unsigned NArgs = opers.getMetaOper(PatchPointOpers::NArgPos).getImm();
367    for (unsigned i = 0, e = (opers.hasDef() ? NArgs + 1 : NArgs); i != e; ++i)
368      assert(Locations[i].Type == Location::Register &&
369             "anyreg arg must be in reg.");
370  }
371#endif
372}
373void StackMaps::recordStatepoint(const MachineInstr &MI) {
374  assert(MI.getOpcode() == TargetOpcode::STATEPOINT && "expected statepoint");
375
376  StatepointOpers opers(&MI);
377  // Record all the deopt and gc operands (they're contiguous and run from the
378  // initial index to the end of the operand list)
379  const unsigned StartIdx = opers.getVarIdx();
380  recordStackMapOpers(MI, opers.getID(), MI.operands_begin() + StartIdx,
381                      MI.operands_end(), false);
382}
383
384/// Emit the stackmap header.
385///
386/// Header {
387///   uint8  : Stack Map Version (currently 1)
388///   uint8  : Reserved (expected to be 0)
389///   uint16 : Reserved (expected to be 0)
390/// }
391/// uint32 : NumFunctions
392/// uint32 : NumConstants
393/// uint32 : NumRecords
394void StackMaps::emitStackmapHeader(MCStreamer &OS) {
395  // Header.
396  OS.EmitIntValue(StackMapVersion, 1); // Version.
397  OS.EmitIntValue(0, 1);               // Reserved.
398  OS.EmitIntValue(0, 2);               // Reserved.
399
400  // Num functions.
401  DEBUG(dbgs() << WSMP << "#functions = " << FnStackSize.size() << '\n');
402  OS.EmitIntValue(FnStackSize.size(), 4);
403  // Num constants.
404  DEBUG(dbgs() << WSMP << "#constants = " << ConstPool.size() << '\n');
405  OS.EmitIntValue(ConstPool.size(), 4);
406  // Num callsites.
407  DEBUG(dbgs() << WSMP << "#callsites = " << CSInfos.size() << '\n');
408  OS.EmitIntValue(CSInfos.size(), 4);
409}
410
411/// Emit the function frame record for each function.
412///
413/// StkSizeRecord[NumFunctions] {
414///   uint64 : Function Address
415///   uint64 : Stack Size
416/// }
417void StackMaps::emitFunctionFrameRecords(MCStreamer &OS) {
418  // Function Frame records.
419  DEBUG(dbgs() << WSMP << "functions:\n");
420  for (auto const &FR : FnStackSize) {
421    DEBUG(dbgs() << WSMP << "function addr: " << FR.first
422                 << " frame size: " << FR.second);
423    OS.EmitSymbolValue(FR.first, 8);
424    OS.EmitIntValue(FR.second, 8);
425  }
426}
427
428/// Emit the constant pool.
429///
430/// int64  : Constants[NumConstants]
431void StackMaps::emitConstantPoolEntries(MCStreamer &OS) {
432  // Constant pool entries.
433  DEBUG(dbgs() << WSMP << "constants:\n");
434  for (const auto &ConstEntry : ConstPool) {
435    DEBUG(dbgs() << WSMP << ConstEntry.second << '\n');
436    OS.EmitIntValue(ConstEntry.second, 8);
437  }
438}
439
440/// Emit the callsite info for each callsite.
441///
442/// StkMapRecord[NumRecords] {
443///   uint64 : PatchPoint ID
444///   uint32 : Instruction Offset
445///   uint16 : Reserved (record flags)
446///   uint16 : NumLocations
447///   Location[NumLocations] {
448///     uint8  : Register | Direct | Indirect | Constant | ConstantIndex
449///     uint8  : Size in Bytes
450///     uint16 : Dwarf RegNum
451///     int32  : Offset
452///   }
453///   uint16 : Padding
454///   uint16 : NumLiveOuts
455///   LiveOuts[NumLiveOuts] {
456///     uint16 : Dwarf RegNum
457///     uint8  : Reserved
458///     uint8  : Size in Bytes
459///   }
460///   uint32 : Padding (only if required to align to 8 byte)
461/// }
462///
463/// Location Encoding, Type, Value:
464///   0x1, Register, Reg                 (value in register)
465///   0x2, Direct, Reg + Offset          (frame index)
466///   0x3, Indirect, [Reg + Offset]      (spilled value)
467///   0x4, Constant, Offset              (small constant)
468///   0x5, ConstIndex, Constants[Offset] (large constant)
469void StackMaps::emitCallsiteEntries(MCStreamer &OS) {
470  DEBUG(print(dbgs()));
471  // Callsite entries.
472  for (const auto &CSI : CSInfos) {
473    const LocationVec &CSLocs = CSI.Locations;
474    const LiveOutVec &LiveOuts = CSI.LiveOuts;
475
476    // Verify stack map entry. It's better to communicate a problem to the
477    // runtime than crash in case of in-process compilation. Currently, we do
478    // simple overflow checks, but we may eventually communicate other
479    // compilation errors this way.
480    if (CSLocs.size() > UINT16_MAX || LiveOuts.size() > UINT16_MAX) {
481      OS.EmitIntValue(UINT64_MAX, 8); // Invalid ID.
482      OS.EmitValue(CSI.CSOffsetExpr, 4);
483      OS.EmitIntValue(0, 2); // Reserved.
484      OS.EmitIntValue(0, 2); // 0 locations.
485      OS.EmitIntValue(0, 2); // padding.
486      OS.EmitIntValue(0, 2); // 0 live-out registers.
487      OS.EmitIntValue(0, 4); // padding.
488      continue;
489    }
490
491    OS.EmitIntValue(CSI.ID, 8);
492    OS.EmitValue(CSI.CSOffsetExpr, 4);
493
494    // Reserved for flags.
495    OS.EmitIntValue(0, 2);
496    OS.EmitIntValue(CSLocs.size(), 2);
497
498    for (const auto &Loc : CSLocs) {
499      OS.EmitIntValue(Loc.Type, 1);
500      OS.EmitIntValue(Loc.Size, 1);
501      OS.EmitIntValue(Loc.Reg, 2);
502      OS.EmitIntValue(Loc.Offset, 4);
503    }
504
505    // Num live-out registers and padding to align to 4 byte.
506    OS.EmitIntValue(0, 2);
507    OS.EmitIntValue(LiveOuts.size(), 2);
508
509    for (const auto &LO : LiveOuts) {
510      OS.EmitIntValue(LO.DwarfRegNum, 2);
511      OS.EmitIntValue(0, 1);
512      OS.EmitIntValue(LO.Size, 1);
513    }
514    // Emit alignment to 8 byte.
515    OS.EmitValueToAlignment(8);
516  }
517}
518
519/// Serialize the stackmap data.
520void StackMaps::serializeToStackMapSection() {
521  (void)WSMP;
522  // Bail out if there's no stack map data.
523  assert((!CSInfos.empty() || (CSInfos.empty() && ConstPool.empty())) &&
524         "Expected empty constant pool too!");
525  assert((!CSInfos.empty() || (CSInfos.empty() && FnStackSize.empty())) &&
526         "Expected empty function record too!");
527  if (CSInfos.empty())
528    return;
529
530  MCContext &OutContext = AP.OutStreamer->getContext();
531  MCStreamer &OS = *AP.OutStreamer;
532
533  // Create the section.
534  MCSection *StackMapSection =
535      OutContext.getObjectFileInfo()->getStackMapSection();
536  OS.SwitchSection(StackMapSection);
537
538  // Emit a dummy symbol to force section inclusion.
539  OS.EmitLabel(OutContext.getOrCreateSymbol(Twine("__LLVM_StackMaps")));
540
541  // Serialize data.
542  DEBUG(dbgs() << "********** Stack Map Output **********\n");
543  emitStackmapHeader(OS);
544  emitFunctionFrameRecords(OS);
545  emitConstantPoolEntries(OS);
546  emitCallsiteEntries(OS);
547  OS.AddBlankLine();
548
549  // Clean up.
550  CSInfos.clear();
551  ConstPool.clear();
552}
553