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 #define DEBUG_TYPE "stackmaps"
11 
12 #include "llvm/CodeGen/StackMaps.h"
13 
14 #include "llvm/CodeGen/AsmPrinter.h"
15 #include "llvm/CodeGen/MachineInstr.h"
16 #include "llvm/IR/DataLayout.h"
17 #include "llvm/MC/MCContext.h"
18 #include "llvm/MC/MCExpr.h"
19 #include "llvm/MC/MCObjectFileInfo.h"
20 #include "llvm/MC/MCSectionMachO.h"
21 #include "llvm/MC/MCStreamer.h"
22 #include "llvm/Support/Debug.h"
23 #include "llvm/Support/raw_ostream.h"
24 #include "llvm/Target/TargetOpcodes.h"
25 #include "llvm/Target/TargetMachine.h"
26 #include "llvm/Target/TargetRegisterInfo.h"
27 
28 #include <iterator>
29 
30 using namespace llvm;
31 
32 PatchPointOpers::PatchPointOpers(const MachineInstr *MI):
33   MI(MI),
34   HasDef(MI->getOperand(0).isReg() && MI->getOperand(0).isDef() &&
35          !MI->getOperand(0).isImplicit()),
36   IsAnyReg(MI->getOperand(getMetaIdx(CCPos)).getImm() == CallingConv::AnyReg) {
37 
38 #ifndef NDEBUG
39   {
40   unsigned CheckStartIdx = 0, e = MI->getNumOperands();
41   while (CheckStartIdx < e && MI->getOperand(CheckStartIdx).isReg() &&
42          MI->getOperand(CheckStartIdx).isDef() &&
43          !MI->getOperand(CheckStartIdx).isImplicit())
44     ++CheckStartIdx;
45 
46   assert(getMetaIdx() == CheckStartIdx &&
47          "Unexpected additonal definition in Patchpoint intrinsic.");
48   }
49 #endif
50 }
51 
52 unsigned PatchPointOpers::getNextScratchIdx(unsigned StartIdx) const {
53   if (!StartIdx)
54     StartIdx = getVarIdx();
55 
56   // Find the next scratch register (implicit def and early clobber)
57   unsigned ScratchIdx = StartIdx, e = MI->getNumOperands();
58   while (ScratchIdx < e &&
59          !(MI->getOperand(ScratchIdx).isReg() &&
60            MI->getOperand(ScratchIdx).isDef() &&
61            MI->getOperand(ScratchIdx).isImplicit() &&
62            MI->getOperand(ScratchIdx).isEarlyClobber()))
63     ++ScratchIdx;
64 
65   assert(ScratchIdx != e && "No scratch register available");
66   return ScratchIdx;
67 }
68 
69 std::pair<StackMaps::Location, MachineInstr::const_mop_iterator>
70 StackMaps::parseOperand(MachineInstr::const_mop_iterator MOI,
71                         MachineInstr::const_mop_iterator MOE) {
72   const MachineOperand &MOP = *MOI;
73   assert(!MOP.isRegMask() && (!MOP.isReg() || !MOP.isImplicit()) &&
74          "Register mask and implicit operands should not be processed.");
75 
76   if (MOP.isImm()) {
77     // Verify anyregcc
78     // [<def>], <id>, <numBytes>, <target>, <numArgs>, <cc>, ...
79 
80     switch (MOP.getImm()) {
81       default: llvm_unreachable("Unrecognized operand type.");
82       case StackMaps::DirectMemRefOp: {
83         unsigned Size = AP.TM.getDataLayout()->getPointerSizeInBits();
84         assert((Size % 8) == 0 && "Need pointer size in bytes.");
85         Size /= 8;
86         unsigned Reg = (++MOI)->getReg();
87         int64_t Imm = (++MOI)->getImm();
88         return std::make_pair(
89           Location(StackMaps::Location::Direct, Size, Reg, Imm), ++MOI);
90       }
91       case StackMaps::IndirectMemRefOp: {
92         int64_t Size = (++MOI)->getImm();
93         assert(Size > 0 && "Need a valid size for indirect memory locations.");
94         unsigned Reg = (++MOI)->getReg();
95         int64_t Imm = (++MOI)->getImm();
96         return std::make_pair(
97           Location(StackMaps::Location::Indirect, Size, Reg, Imm), ++MOI);
98       }
99       case StackMaps::ConstantOp: {
100         ++MOI;
101         assert(MOI->isImm() && "Expected constant operand.");
102         int64_t Imm = MOI->getImm();
103         return std::make_pair(
104           Location(Location::Constant, sizeof(int64_t), 0, Imm), ++MOI);
105       }
106     }
107   }
108 
109   // Otherwise this is a reg operand. The physical register number will
110   // ultimately be encoded as a DWARF regno. The stack map also records the size
111   // of a spill slot that can hold the register content. (The runtime can
112   // track the actual size of the data type if it needs to.)
113   assert(MOP.isReg() && "Expected register operand here.");
114   assert(TargetRegisterInfo::isPhysicalRegister(MOP.getReg()) &&
115          "Virtreg operands should have been rewritten before now.");
116   const TargetRegisterClass *RC =
117     AP.TM.getRegisterInfo()->getMinimalPhysRegClass(MOP.getReg());
118   assert(!MOP.getSubReg() && "Physical subreg still around.");
119   return std::make_pair(
120     Location(Location::Register, RC->getSize(), MOP.getReg(), 0), ++MOI);
121 }
122 
123 void StackMaps::recordStackMapOpers(const MachineInstr &MI, uint64_t ID,
124                                     MachineInstr::const_mop_iterator MOI,
125                                     MachineInstr::const_mop_iterator MOE,
126                                     bool recordResult) {
127 
128   MCContext &OutContext = AP.OutStreamer.getContext();
129   MCSymbol *MILabel = OutContext.CreateTempSymbol();
130   AP.OutStreamer.EmitLabel(MILabel);
131 
132   LocationVec CallsiteLocs;
133 
134   if (recordResult) {
135     std::pair<Location, MachineInstr::const_mop_iterator> ParseResult =
136       parseOperand(MI.operands_begin(), llvm::next(MI.operands_begin()));
137 
138     Location &Loc = ParseResult.first;
139     assert(Loc.LocType == Location::Register &&
140            "Stackmap return location must be a register.");
141     CallsiteLocs.push_back(Loc);
142   }
143 
144   while (MOI != MOE) {
145     Location Loc;
146     tie(Loc, MOI) = parseOperand(MOI, MOE);
147 
148     // Move large constants into the constant pool.
149     if (Loc.LocType == Location::Constant && (Loc.Offset & ~0xFFFFFFFFULL)) {
150       Loc.LocType = Location::ConstantIndex;
151       Loc.Offset = ConstPool.getConstantIndex(Loc.Offset);
152     }
153 
154     CallsiteLocs.push_back(Loc);
155   }
156 
157   const MCExpr *CSOffsetExpr = MCBinaryExpr::CreateSub(
158     MCSymbolRefExpr::Create(MILabel, OutContext),
159     MCSymbolRefExpr::Create(AP.CurrentFnSym, OutContext),
160     OutContext);
161 
162   CSInfos.push_back(CallsiteInfo(CSOffsetExpr, ID, CallsiteLocs));
163 }
164 
165 static MachineInstr::const_mop_iterator
166 getStackMapEndMOP(MachineInstr::const_mop_iterator MOI,
167                   MachineInstr::const_mop_iterator MOE) {
168   for (; MOI != MOE; ++MOI)
169     if (MOI->isRegMask() || (MOI->isReg() && MOI->isImplicit()))
170       break;
171 
172   return MOI;
173 }
174 
175 void StackMaps::recordStackMap(const MachineInstr &MI) {
176   assert(MI.getOpcode() == TargetOpcode::STACKMAP && "exected stackmap");
177 
178   int64_t ID = MI.getOperand(0).getImm();
179   recordStackMapOpers(MI, ID, llvm::next(MI.operands_begin(), 2),
180                       getStackMapEndMOP(MI.operands_begin(),
181                                         MI.operands_end()));
182 }
183 
184 void StackMaps::recordPatchPoint(const MachineInstr &MI) {
185   assert(MI.getOpcode() == TargetOpcode::PATCHPOINT && "exected stackmap");
186 
187   PatchPointOpers opers(&MI);
188   int64_t ID = opers.getMetaOper(PatchPointOpers::IDPos).getImm();
189 
190   MachineInstr::const_mop_iterator MOI =
191     llvm::next(MI.operands_begin(), opers.getStackMapStartIdx());
192   recordStackMapOpers(MI, ID, MOI, getStackMapEndMOP(MOI, MI.operands_end()),
193                       opers.isAnyReg() && opers.hasDef());
194 
195 #ifndef NDEBUG
196   // verify anyregcc
197   LocationVec &Locations = CSInfos.back().Locations;
198   if (opers.isAnyReg()) {
199     unsigned NArgs = opers.getMetaOper(PatchPointOpers::NArgPos).getImm();
200     for (unsigned i = 0, e = (opers.hasDef() ? NArgs+1 : NArgs); i != e; ++i)
201       assert(Locations[i].LocType == Location::Register &&
202              "anyreg arg must be in reg.");
203   }
204 #endif
205 }
206 
207 /// serializeToStackMapSection conceptually populates the following fields:
208 ///
209 /// uint32 : Reserved (header)
210 /// uint32 : NumConstants
211 /// int64  : Constants[NumConstants]
212 /// uint32 : NumRecords
213 /// StkMapRecord[NumRecords] {
214 ///   uint64 : PatchPoint ID
215 ///   uint32 : Instruction Offset
216 ///   uint16 : Reserved (record flags)
217 ///   uint16 : NumLocations
218 ///   Location[NumLocations] {
219 ///     uint8  : Register | Direct | Indirect | Constant | ConstantIndex
220 ///     uint8  : Size in Bytes
221 ///     uint16 : Dwarf RegNum
222 ///     int32  : Offset
223 ///   }
224 /// }
225 ///
226 /// Location Encoding, Type, Value:
227 ///   0x1, Register, Reg                 (value in register)
228 ///   0x2, Direct, Reg + Offset          (frame index)
229 ///   0x3, Indirect, [Reg + Offset]      (spilled value)
230 ///   0x4, Constant, Offset              (small constant)
231 ///   0x5, ConstIndex, Constants[Offset] (large constant)
232 ///
233 void StackMaps::serializeToStackMapSection() {
234   // Bail out if there's no stack map data.
235   if (CSInfos.empty())
236     return;
237 
238   MCContext &OutContext = AP.OutStreamer.getContext();
239   const TargetRegisterInfo *TRI = AP.TM.getRegisterInfo();
240 
241   // Create the section.
242   const MCSection *StackMapSection =
243     OutContext.getObjectFileInfo()->getStackMapSection();
244   AP.OutStreamer.SwitchSection(StackMapSection);
245 
246   // Emit a dummy symbol to force section inclusion.
247   AP.OutStreamer.EmitLabel(
248     OutContext.GetOrCreateSymbol(Twine("__LLVM_StackMaps")));
249 
250   // Serialize data.
251   const char *WSMP = "Stack Maps: ";
252   (void)WSMP;
253   const MCRegisterInfo &MCRI = *OutContext.getRegisterInfo();
254 
255   DEBUG(dbgs() << "********** Stack Map Output **********\n");
256 
257   // Header.
258   AP.OutStreamer.EmitIntValue(0, 4);
259 
260   // Num constants.
261   AP.OutStreamer.EmitIntValue(ConstPool.getNumConstants(), 4);
262 
263   // Constant pool entries.
264   for (unsigned i = 0; i < ConstPool.getNumConstants(); ++i)
265     AP.OutStreamer.EmitIntValue(ConstPool.getConstant(i), 8);
266 
267   DEBUG(dbgs() << WSMP << "#callsites = " << CSInfos.size() << "\n");
268   AP.OutStreamer.EmitIntValue(CSInfos.size(), 4);
269 
270   for (CallsiteInfoList::const_iterator CSII = CSInfos.begin(),
271                                         CSIE = CSInfos.end();
272        CSII != CSIE; ++CSII) {
273 
274     uint64_t CallsiteID = CSII->ID;
275     const LocationVec &CSLocs = CSII->Locations;
276 
277     DEBUG(dbgs() << WSMP << "callsite " << CallsiteID << "\n");
278 
279     // Verify stack map entry. It's better to communicate a problem to the
280     // runtime than crash in case of in-process compilation. Currently, we do
281     // simple overflow checks, but we may eventually communicate other
282     // compilation errors this way.
283     if (CSLocs.size() > UINT16_MAX) {
284       AP.OutStreamer.EmitIntValue(UINT32_MAX, 8); // Invalid ID.
285       AP.OutStreamer.EmitValue(CSII->CSOffsetExpr, 4);
286       AP.OutStreamer.EmitIntValue(0, 2); // Reserved.
287       AP.OutStreamer.EmitIntValue(0, 2); // 0 locations.
288       continue;
289     }
290 
291     AP.OutStreamer.EmitIntValue(CallsiteID, 8);
292     AP.OutStreamer.EmitValue(CSII->CSOffsetExpr, 4);
293 
294     // Reserved for flags.
295     AP.OutStreamer.EmitIntValue(0, 2);
296 
297     DEBUG(dbgs() << WSMP << "  has " << CSLocs.size() << " locations\n");
298 
299     AP.OutStreamer.EmitIntValue(CSLocs.size(), 2);
300 
301     unsigned operIdx = 0;
302     for (LocationVec::const_iterator LocI = CSLocs.begin(), LocE = CSLocs.end();
303          LocI != LocE; ++LocI, ++operIdx) {
304       const Location &Loc = *LocI;
305       unsigned RegNo = 0;
306       int Offset = Loc.Offset;
307       if(Loc.Reg) {
308         RegNo = MCRI.getDwarfRegNum(Loc.Reg, false);
309         for (MCSuperRegIterator SR(Loc.Reg, TRI);
310              SR.isValid() && (int)RegNo < 0; ++SR) {
311           RegNo = TRI->getDwarfRegNum(*SR, false);
312         }
313         // If this is a register location, put the subregister byte offset in
314         // the location offset.
315         if (Loc.LocType == Location::Register) {
316           assert(!Loc.Offset && "Register location should have zero offset");
317           unsigned LLVMRegNo = MCRI.getLLVMRegNum(RegNo, false);
318           unsigned SubRegIdx = MCRI.getSubRegIndex(LLVMRegNo, Loc.Reg);
319           if (SubRegIdx)
320             Offset = MCRI.getSubRegIdxOffset(SubRegIdx);
321         }
322       }
323       else {
324         assert(Loc.LocType != Location::Register &&
325                "Missing location register");
326       }
327 
328       DEBUG(
329         dbgs() << WSMP << "  Loc " << operIdx << ": ";
330         switch (Loc.LocType) {
331         case Location::Unprocessed:
332           dbgs() << "<Unprocessed operand>";
333           break;
334         case Location::Register:
335           dbgs() << "Register " << MCRI.getName(Loc.Reg);
336           break;
337         case Location::Direct:
338           dbgs() << "Direct " << MCRI.getName(Loc.Reg);
339           if (Loc.Offset)
340             dbgs() << " + " << Loc.Offset;
341           break;
342         case Location::Indirect:
343           dbgs() << "Indirect " << MCRI.getName(Loc.Reg)
344                  << " + " << Loc.Offset;
345           break;
346         case Location::Constant:
347           dbgs() << "Constant " << Loc.Offset;
348           break;
349         case Location::ConstantIndex:
350           dbgs() << "Constant Index " << Loc.Offset;
351           break;
352         }
353         dbgs() << "     [encoding: .byte " << Loc.LocType
354                << ", .byte " << Loc.Size
355                << ", .short " << RegNo
356                << ", .int " << Offset << "]\n";
357       );
358 
359       AP.OutStreamer.EmitIntValue(Loc.LocType, 1);
360       AP.OutStreamer.EmitIntValue(Loc.Size, 1);
361       AP.OutStreamer.EmitIntValue(RegNo, 2);
362       AP.OutStreamer.EmitIntValue(Offset, 4);
363     }
364   }
365 
366   AP.OutStreamer.AddBlankLine();
367 
368   CSInfos.clear();
369 }
370