Line data Source code
1 : //===- LiveDebugValues.cpp - Tracking Debug Value MIs ---------------------===//
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 : /// This pass implements a data flow analysis that propagates debug location
11 : /// information by inserting additional DBG_VALUE instructions into the machine
12 : /// instruction stream. The pass internally builds debug location liveness
13 : /// ranges to determine the points where additional DBG_VALUEs need to be
14 : /// inserted.
15 : ///
16 : /// This is a separate pass from DbgValueHistoryCalculator to facilitate
17 : /// testing and improve modularity.
18 : ///
19 : //===----------------------------------------------------------------------===//
20 :
21 : #include "llvm/ADT/DenseMap.h"
22 : #include "llvm/ADT/PostOrderIterator.h"
23 : #include "llvm/ADT/SmallPtrSet.h"
24 : #include "llvm/ADT/SmallVector.h"
25 : #include "llvm/ADT/SparseBitVector.h"
26 : #include "llvm/ADT/Statistic.h"
27 : #include "llvm/ADT/UniqueVector.h"
28 : #include "llvm/CodeGen/LexicalScopes.h"
29 : #include "llvm/CodeGen/MachineBasicBlock.h"
30 : #include "llvm/CodeGen/MachineFrameInfo.h"
31 : #include "llvm/CodeGen/MachineFunction.h"
32 : #include "llvm/CodeGen/MachineFunctionPass.h"
33 : #include "llvm/CodeGen/MachineInstr.h"
34 : #include "llvm/CodeGen/MachineInstrBuilder.h"
35 : #include "llvm/CodeGen/MachineMemOperand.h"
36 : #include "llvm/CodeGen/MachineOperand.h"
37 : #include "llvm/CodeGen/PseudoSourceValue.h"
38 : #include "llvm/CodeGen/TargetFrameLowering.h"
39 : #include "llvm/CodeGen/TargetInstrInfo.h"
40 : #include "llvm/CodeGen/TargetLowering.h"
41 : #include "llvm/CodeGen/TargetRegisterInfo.h"
42 : #include "llvm/CodeGen/TargetSubtargetInfo.h"
43 : #include "llvm/CodeGen/RegisterScavenging.h"
44 : #include "llvm/Config/llvm-config.h"
45 : #include "llvm/IR/DebugInfoMetadata.h"
46 : #include "llvm/IR/DebugLoc.h"
47 : #include "llvm/IR/Function.h"
48 : #include "llvm/IR/Module.h"
49 : #include "llvm/MC/MCRegisterInfo.h"
50 : #include "llvm/Pass.h"
51 : #include "llvm/Support/Casting.h"
52 : #include "llvm/Support/Compiler.h"
53 : #include "llvm/Support/Debug.h"
54 : #include "llvm/Support/raw_ostream.h"
55 : #include <algorithm>
56 : #include <cassert>
57 : #include <cstdint>
58 : #include <functional>
59 : #include <queue>
60 : #include <utility>
61 : #include <vector>
62 :
63 : using namespace llvm;
64 :
65 : #define DEBUG_TYPE "livedebugvalues"
66 :
67 : STATISTIC(NumInserted, "Number of DBG_VALUE instructions inserted");
68 :
69 : // If @MI is a DBG_VALUE with debug value described by a defined
70 : // register, returns the number of this register. In the other case, returns 0.
71 : static unsigned isDbgValueDescribedByReg(const MachineInstr &MI) {
72 : assert(MI.isDebugValue() && "expected a DBG_VALUE");
73 : assert(MI.getNumOperands() == 4 && "malformed DBG_VALUE");
74 : // If location of variable is described using a register (directly
75 : // or indirectly), this register is always a first operand.
76 1045002 : return MI.getOperand(0).isReg() ? MI.getOperand(0).getReg() : 0;
77 : }
78 :
79 : namespace {
80 :
81 : class LiveDebugValues : public MachineFunctionPass {
82 : private:
83 : const TargetRegisterInfo *TRI;
84 : const TargetInstrInfo *TII;
85 : const TargetFrameLowering *TFI;
86 : BitVector CalleeSavedRegs;
87 : LexicalScopes LS;
88 :
89 : /// Keeps track of lexical scopes associated with a user value's source
90 : /// location.
91 : class UserValueScopes {
92 : DebugLoc DL;
93 : LexicalScopes &LS;
94 : SmallPtrSet<const MachineBasicBlock *, 4> LBlocks;
95 :
96 : public:
97 635680 : UserValueScopes(DebugLoc D, LexicalScopes &L) : DL(std::move(D)), LS(L) {}
98 :
99 : /// Return true if current scope dominates at least one machine
100 : /// instruction in a given machine basic block.
101 367630 : bool dominates(MachineBasicBlock *MBB) {
102 367630 : if (LBlocks.empty())
103 52431 : LS.getMachineBasicBlocks(DL, LBlocks);
104 367630 : return LBlocks.count(MBB) != 0 || LS.dominates(DL, MBB);
105 : }
106 : };
107 :
108 : /// Based on std::pair so it can be used as an index into a DenseMap.
109 : using DebugVariableBase =
110 : std::pair<const DILocalVariable *, const DILocation *>;
111 : /// A potentially inlined instance of a variable.
112 : struct DebugVariable : public DebugVariableBase {
113 : DebugVariable(const DILocalVariable *Var, const DILocation *InlinedAt)
114 : : DebugVariableBase(Var, InlinedAt) {}
115 :
116 0 : const DILocalVariable *getVar() const { return this->first; }
117 0 : const DILocation *getInlinedAt() const { return this->second; }
118 :
119 : bool operator<(const DebugVariable &DV) const {
120 213393 : if (getVar() == DV.getVar())
121 63216 : return getInlinedAt() < DV.getInlinedAt();
122 150177 : return getVar() < DV.getVar();
123 : }
124 : };
125 :
126 : /// A pair of debug variable and value location.
127 770971 : struct VarLoc {
128 : const DebugVariable Var;
129 : const MachineInstr &MI; ///< Only used for cloning a new DBG_VALUE.
130 : mutable UserValueScopes UVS;
131 : enum { InvalidKind = 0, RegisterKind } Kind = InvalidKind;
132 :
133 : /// The value location. Stored separately to avoid repeatedly
134 : /// extracting it from MI.
135 : union {
136 : uint64_t RegNo;
137 : uint64_t Hash;
138 : } Loc;
139 :
140 317840 : VarLoc(const MachineInstr &MI, LexicalScopes &LS)
141 317840 : : Var(MI.getDebugVariable(), MI.getDebugLoc()->getInlinedAt()), MI(MI),
142 635680 : UVS(MI.getDebugLoc(), LS) {
143 : static_assert((sizeof(Loc) == sizeof(uint64_t)),
144 : "hash does not cover all members of Loc");
145 : assert(MI.isDebugValue() && "not a DBG_VALUE");
146 : assert(MI.getNumOperands() == 4 && "malformed DBG_VALUE");
147 317840 : if (int RegNo = isDbgValueDescribedByReg(MI)) {
148 317840 : Kind = RegisterKind;
149 317840 : Loc.RegNo = RegNo;
150 : }
151 317840 : }
152 :
153 : /// If this variable is described by a register, return it,
154 : /// otherwise return 0.
155 0 : unsigned isDescribedByReg() const {
156 0 : if (Kind == RegisterKind)
157 6940 : return Loc.RegNo;
158 : return 0;
159 : }
160 :
161 : /// Determine whether the lexical scope of this value's debug location
162 : /// dominates MBB.
163 0 : bool dominates(MachineBasicBlock &MBB) const { return UVS.dominates(&MBB); }
164 :
165 : #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
166 : LLVM_DUMP_METHOD void dump() const { MI.dump(); }
167 : #endif
168 :
169 : bool operator==(const VarLoc &Other) const {
170 : return Var == Other.Var && Loc.Hash == Other.Loc.Hash;
171 : }
172 :
173 : /// This operator guarantees that VarLocs are sorted by Variable first.
174 : bool operator<(const VarLoc &Other) const {
175 484594 : if (Var == Other.Var)
176 271201 : return Loc.Hash < Other.Loc.Hash;
177 : return Var < Other.Var;
178 : }
179 : };
180 :
181 : using VarLocMap = UniqueVector<VarLoc>;
182 : using VarLocSet = SparseBitVector<>;
183 : using VarLocInMBB = SmallDenseMap<const MachineBasicBlock *, VarLocSet>;
184 : struct TransferDebugPair {
185 : MachineInstr *TransferInst;
186 : MachineInstr *DebugInst;
187 : };
188 : using TransferMap = SmallVector<TransferDebugPair, 4>;
189 :
190 : /// This holds the working set of currently open ranges. For fast
191 : /// access, this is done both as a set of VarLocIDs, and a map of
192 : /// DebugVariable to recent VarLocID. Note that a DBG_VALUE ends all
193 : /// previous open ranges for the same variable.
194 : class OpenRangesSet {
195 : VarLocSet VarLocs;
196 : SmallDenseMap<DebugVariableBase, unsigned, 8> Vars;
197 :
198 : public:
199 1438 : const VarLocSet &getVarLocs() const { return VarLocs; }
200 :
201 : /// Terminate all open ranges for Var by removing it from the set.
202 364312 : void erase(DebugVariable Var) {
203 364312 : auto It = Vars.find(Var);
204 364312 : if (It != Vars.end()) {
205 32617 : unsigned ID = It->second;
206 32617 : VarLocs.reset(ID);
207 : Vars.erase(It);
208 : }
209 364312 : }
210 :
211 : /// Terminate all open ranges listed in \c KillSet by removing
212 : /// them from the set.
213 2220777 : void erase(const VarLocSet &KillSet, const VarLocMap &VarLocIDs) {
214 2220777 : VarLocs.intersectWithComplement(KillSet);
215 35049 : for (unsigned ID : KillSet)
216 70098 : Vars.erase(VarLocIDs[ID].Var);
217 2220777 : }
218 :
219 : /// Insert a new range into the set.
220 317840 : void insert(unsigned VarLocID, DebugVariableBase Var) {
221 317840 : VarLocs.set(VarLocID);
222 317840 : Vars.insert({Var, VarLocID});
223 317840 : }
224 :
225 : /// Empty the set.
226 49239 : void clear() {
227 : VarLocs.clear();
228 49239 : Vars.clear();
229 49239 : }
230 :
231 : /// Return whether the set is empty or not.
232 : bool empty() const {
233 : assert(Vars.empty() == VarLocs.empty() && "open ranges are inconsistent");
234 : return VarLocs.empty();
235 : }
236 : };
237 :
238 : bool isSpillInstruction(const MachineInstr &MI, MachineFunction *MF,
239 : unsigned &Reg);
240 : int extractSpillBaseRegAndOffset(const MachineInstr &MI, unsigned &Reg);
241 : void insertTransferDebugPair(MachineInstr &MI, OpenRangesSet &OpenRanges,
242 : TransferMap &Transfers, VarLocMap &VarLocIDs,
243 : unsigned OldVarID, unsigned NewReg = 0);
244 :
245 : void transferDebugValue(const MachineInstr &MI, OpenRangesSet &OpenRanges,
246 : VarLocMap &VarLocIDs);
247 : void transferSpillInst(MachineInstr &MI, OpenRangesSet &OpenRanges,
248 : VarLocMap &VarLocIDs, TransferMap &Transfers);
249 : void transferRegisterCopy(MachineInstr &MI, OpenRangesSet &OpenRanges,
250 : VarLocMap &VarLocIDs, TransferMap &Transfers);
251 : void transferRegisterDef(MachineInstr &MI, OpenRangesSet &OpenRanges,
252 : const VarLocMap &VarLocIDs);
253 : bool transferTerminatorInst(MachineInstr &MI, OpenRangesSet &OpenRanges,
254 : VarLocInMBB &OutLocs, const VarLocMap &VarLocIDs);
255 : bool process(MachineInstr &MI, OpenRangesSet &OpenRanges,
256 : VarLocInMBB &OutLocs, VarLocMap &VarLocIDs,
257 : TransferMap &Transfers, bool transferChanges);
258 :
259 : bool join(MachineBasicBlock &MBB, VarLocInMBB &OutLocs, VarLocInMBB &InLocs,
260 : const VarLocMap &VarLocIDs,
261 : SmallPtrSet<const MachineBasicBlock *, 16> &Visited,
262 : SmallPtrSetImpl<const MachineBasicBlock *> &ArtificialBlocks);
263 :
264 : bool ExtendRanges(MachineFunction &MF);
265 :
266 : public:
267 : static char ID;
268 :
269 : /// Default construct and initialize the pass.
270 : LiveDebugValues();
271 :
272 : /// Tell the pass manager which passes we depend on and what
273 : /// information we preserve.
274 : void getAnalysisUsage(AnalysisUsage &AU) const override;
275 :
276 26737 : MachineFunctionProperties getRequiredProperties() const override {
277 26737 : return MachineFunctionProperties().set(
278 26737 : MachineFunctionProperties::Property::NoVRegs);
279 : }
280 :
281 : /// Print to ostream with a message.
282 : void printVarLocInMBB(const MachineFunction &MF, const VarLocInMBB &V,
283 : const VarLocMap &VarLocIDs, const char *msg,
284 : raw_ostream &Out) const;
285 :
286 : /// Calculate the liveness information for the given machine function.
287 : bool runOnMachineFunction(MachineFunction &MF) override;
288 : };
289 :
290 : } // end anonymous namespace
291 :
292 : //===----------------------------------------------------------------------===//
293 : // Implementation
294 : //===----------------------------------------------------------------------===//
295 :
296 : char LiveDebugValues::ID = 0;
297 :
298 : char &llvm::LiveDebugValuesID = LiveDebugValues::ID;
299 :
300 112060 : INITIALIZE_PASS(LiveDebugValues, DEBUG_TYPE, "Live DEBUG_VALUE analysis",
301 : false, false)
302 :
303 : /// Default construct and initialize the pass.
304 26913 : LiveDebugValues::LiveDebugValues() : MachineFunctionPass(ID) {
305 26913 : initializeLiveDebugValuesPass(*PassRegistry::getPassRegistry());
306 26913 : }
307 :
308 : /// Tell the pass manager which passes we depend on and what information we
309 : /// preserve.
310 26734 : void LiveDebugValues::getAnalysisUsage(AnalysisUsage &AU) const {
311 26734 : AU.setPreservesCFG();
312 26734 : MachineFunctionPass::getAnalysisUsage(AU);
313 26734 : }
314 :
315 : //===----------------------------------------------------------------------===//
316 : // Debug Range Extension Implementation
317 : //===----------------------------------------------------------------------===//
318 :
319 : #ifndef NDEBUG
320 : void LiveDebugValues::printVarLocInMBB(const MachineFunction &MF,
321 : const VarLocInMBB &V,
322 : const VarLocMap &VarLocIDs,
323 : const char *msg,
324 : raw_ostream &Out) const {
325 : Out << '\n' << msg << '\n';
326 : for (const MachineBasicBlock &BB : MF) {
327 : const VarLocSet &L = V.lookup(&BB);
328 : if (L.empty())
329 : continue;
330 : Out << "MBB: " << BB.getNumber() << ":\n";
331 : for (unsigned VLL : L) {
332 : const VarLoc &VL = VarLocIDs[VLL];
333 : Out << " Var: " << VL.Var.getVar()->getName();
334 : Out << " MI: ";
335 : VL.dump();
336 : }
337 : }
338 : Out << "\n";
339 : }
340 : #endif
341 :
342 : /// Given a spill instruction, extract the register and offset used to
343 : /// address the spill location in a target independent way.
344 0 : int LiveDebugValues::extractSpillBaseRegAndOffset(const MachineInstr &MI,
345 : unsigned &Reg) {
346 : assert(MI.hasOneMemOperand() &&
347 : "Spill instruction does not have exactly one memory operand?");
348 : auto MMOI = MI.memoperands_begin();
349 0 : const PseudoSourceValue *PVal = (*MMOI)->getPseudoValue();
350 : assert(PVal->kind() == PseudoSourceValue::FixedStack &&
351 : "Inconsistent memory operand in spill instruction");
352 0 : int FI = cast<FixedStackPseudoSourceValue>(PVal)->getFrameIndex();
353 0 : const MachineBasicBlock *MBB = MI.getParent();
354 0 : return TFI->getFrameIndexReference(*MBB->getParent(), FI, Reg);
355 : }
356 :
357 : /// End all previous ranges related to @MI and start a new range from @MI
358 : /// if it is a DBG_VALUE instr.
359 2220777 : void LiveDebugValues::transferDebugValue(const MachineInstr &MI,
360 : OpenRangesSet &OpenRanges,
361 : VarLocMap &VarLocIDs) {
362 2220777 : if (!MI.isDebugValue())
363 1857196 : return;
364 363581 : const DILocalVariable *Var = MI.getDebugVariable();
365 : const DILocation *DebugLoc = MI.getDebugLoc();
366 : const DILocation *InlinedAt = DebugLoc->getInlinedAt();
367 : assert(Var->isValidLocationForIntrinsic(DebugLoc) &&
368 : "Expected inlined-at fields to agree");
369 :
370 : // End all previous ranges of Var.
371 : DebugVariable V(Var, InlinedAt);
372 363581 : OpenRanges.erase(V);
373 :
374 : // Add the VarLoc to OpenRanges from this DBG_VALUE.
375 : // TODO: Currently handles DBG_VALUE which has only reg as location.
376 348699 : if (isDbgValueDescribedByReg(MI)) {
377 317109 : VarLoc VL(MI, LS);
378 317109 : unsigned ID = VarLocIDs.insert(VL);
379 317109 : OpenRanges.insert(ID, VL.Var);
380 : }
381 : }
382 :
383 : /// Create new TransferDebugPair and insert it in \p Transfers. The VarLoc
384 : /// with \p OldVarID should be deleted form \p OpenRanges and replaced with
385 : /// new VarLoc. If \p NewReg is different than default zero value then the
386 : /// new location will be register location created by the copy like instruction,
387 : /// otherwise it is variable's location on the stack.
388 731 : void LiveDebugValues::insertTransferDebugPair(
389 : MachineInstr &MI, OpenRangesSet &OpenRanges, TransferMap &Transfers,
390 : VarLocMap &VarLocIDs, unsigned OldVarID, unsigned NewReg) {
391 731 : const MachineInstr *DMI = &VarLocIDs[OldVarID].MI;
392 731 : MachineFunction *MF = MI.getParent()->getParent();
393 : MachineInstr *NewDMI;
394 731 : if (NewReg) {
395 : // Create a DBG_VALUE instruction to describe the Var in its new
396 : // register location.
397 461 : NewDMI = BuildMI(*MF, DMI->getDebugLoc(), DMI->getDesc(),
398 : DMI->isIndirectDebugValue(), NewReg,
399 1383 : DMI->getDebugVariable(), DMI->getDebugExpression());
400 : if (DMI->isIndirectDebugValue())
401 0 : NewDMI->getOperand(1).setImm(DMI->getOperand(1).getImm());
402 : LLVM_DEBUG(dbgs() << "Creating DBG_VALUE inst for register copy: ";
403 : NewDMI->print(dbgs(), false, false, false, TII));
404 : } else {
405 : // Create a DBG_VALUE instruction to describe the Var in its spilled
406 : // location.
407 : unsigned SpillBase;
408 270 : int SpillOffset = extractSpillBaseRegAndOffset(MI, SpillBase);
409 270 : auto *SpillExpr = DIExpression::prepend(DMI->getDebugExpression(),
410 : DIExpression::NoDeref, SpillOffset);
411 270 : NewDMI = BuildMI(*MF, DMI->getDebugLoc(), DMI->getDesc(), true, SpillBase,
412 270 : DMI->getDebugVariable(), SpillExpr);
413 : LLVM_DEBUG(dbgs() << "Creating DBG_VALUE inst for spill: ";
414 : NewDMI->print(dbgs(), false, false, false, TII));
415 : }
416 :
417 : // The newly created DBG_VALUE instruction NewDMI must be inserted after
418 : // MI. Keep track of the pairing.
419 731 : TransferDebugPair MIP = {&MI, NewDMI};
420 731 : Transfers.push_back(MIP);
421 :
422 : // End all previous ranges of Var.
423 731 : OpenRanges.erase(VarLocIDs[OldVarID].Var);
424 :
425 : // Add the VarLoc to OpenRanges.
426 731 : VarLoc VL(*NewDMI, LS);
427 731 : unsigned LocID = VarLocIDs.insert(VL);
428 731 : OpenRanges.insert(LocID, VL.Var);
429 731 : }
430 :
431 : /// A definition of a register may mark the end of a range.
432 0 : void LiveDebugValues::transferRegisterDef(MachineInstr &MI,
433 : OpenRangesSet &OpenRanges,
434 : const VarLocMap &VarLocIDs) {
435 : MachineFunction *MF = MI.getMF();
436 0 : const TargetLowering *TLI = MF->getSubtarget().getTargetLowering();
437 0 : unsigned SP = TLI->getStackPointerRegisterToSaveRestore();
438 : SparseBitVector<> KillSet;
439 0 : for (const MachineOperand &MO : MI.operands()) {
440 : // Determine whether the operand is a register def. Assume that call
441 : // instructions never clobber SP, because some backends (e.g., AArch64)
442 : // never list SP in the regmask.
443 0 : if (MO.isReg() && MO.isDef() && MO.getReg() &&
444 0 : TRI->isPhysicalRegister(MO.getReg()) &&
445 0 : !(MI.isCall() && MO.getReg() == SP)) {
446 : // Remove ranges of all aliased registers.
447 0 : for (MCRegAliasIterator RAI(MO.getReg(), TRI, true); RAI.isValid(); ++RAI)
448 0 : for (unsigned ID : OpenRanges.getVarLocs())
449 0 : if (VarLocIDs[ID].isDescribedByReg() == *RAI)
450 0 : KillSet.set(ID);
451 0 : } else if (MO.isRegMask()) {
452 : // Remove ranges of all clobbered registers. Register masks don't usually
453 : // list SP as preserved. While the debug info may be off for an
454 : // instruction or two around callee-cleanup calls, transferring the
455 : // DEBUG_VALUE across the call is still a better user experience.
456 0 : for (unsigned ID : OpenRanges.getVarLocs()) {
457 0 : unsigned Reg = VarLocIDs[ID].isDescribedByReg();
458 0 : if (Reg && Reg != SP && MO.clobbersPhysReg(Reg))
459 0 : KillSet.set(ID);
460 : }
461 : }
462 : }
463 0 : OpenRanges.erase(KillSet, VarLocIDs);
464 0 : }
465 :
466 : /// Decide if @MI is a spill instruction and return true if it is. We use 2
467 : /// criteria to make this decision:
468 : /// - Is this instruction a store to a spill slot?
469 : /// - Is there a register operand that is both used and killed?
470 : /// TODO: Store optimization can fold spills into other stores (including
471 : /// other spills). We do not handle this yet (more than one memory operand).
472 0 : bool LiveDebugValues::isSpillInstruction(const MachineInstr &MI,
473 : MachineFunction *MF, unsigned &Reg) {
474 0 : const MachineFrameInfo &FrameInfo = MF->getFrameInfo();
475 : int FI;
476 : SmallVector<const MachineMemOperand*, 1> Accesses;
477 :
478 : // TODO: Handle multiple stores folded into one.
479 0 : if (!MI.hasOneMemOperand())
480 0 : return false;
481 :
482 : // To identify a spill instruction, use the same criteria as in AsmPrinter.
483 0 : if (!((TII->isStoreToStackSlotPostFE(MI, FI) &&
484 0 : FrameInfo.isSpillSlotObjectIndex(FI)) ||
485 0 : (TII->hasStoreToStackSlot(MI, Accesses) &&
486 : llvm::any_of(Accesses, [&FrameInfo](const MachineMemOperand *MMO) {
487 0 : return FrameInfo.isSpillSlotObjectIndex(
488 : cast<FixedStackPseudoSourceValue>(MMO->getPseudoValue())
489 : ->getFrameIndex());
490 : }))))
491 0 : return false;
492 :
493 : auto isKilledReg = [&](const MachineOperand MO, unsigned &Reg) {
494 0 : if (!MO.isReg() || !MO.isUse()) {
495 0 : Reg = 0;
496 : return false;
497 : }
498 0 : Reg = MO.getReg();
499 : return MO.isKill();
500 : };
501 :
502 0 : for (const MachineOperand &MO : MI.operands()) {
503 : // In a spill instruction generated by the InlineSpiller the spilled
504 : // register has its kill flag set.
505 0 : if (isKilledReg(MO, Reg))
506 0 : return true;
507 0 : if (Reg != 0) {
508 : // Check whether next instruction kills the spilled register.
509 : // FIXME: Current solution does not cover search for killed register in
510 : // bundles and instructions further down the chain.
511 0 : auto NextI = std::next(MI.getIterator());
512 : // Skip next instruction that points to basic block end iterator.
513 0 : if (MI.getParent()->end() == NextI)
514 : continue;
515 : unsigned RegNext;
516 0 : for (const MachineOperand &MONext : NextI->operands()) {
517 : // Return true if we came across the register from the
518 : // previous spill instruction that is killed in NextI.
519 0 : if (isKilledReg(MONext, RegNext) && RegNext == Reg)
520 0 : return true;
521 : }
522 : }
523 : }
524 : // Return false if we didn't find spilled register.
525 : return false;
526 : }
527 :
528 : /// A spilled register may indicate that we have to end the current range of
529 : /// a variable and create a new one for the spill location.
530 : /// We don't want to insert any instructions in process(), so we just create
531 : /// the DBG_VALUE without inserting it and keep track of it in \p Transfers.
532 : /// It will be inserted into the BB when we're done iterating over the
533 : /// instructions.
534 410030 : void LiveDebugValues::transferSpillInst(MachineInstr &MI,
535 : OpenRangesSet &OpenRanges,
536 : VarLocMap &VarLocIDs,
537 : TransferMap &Transfers) {
538 : unsigned Reg;
539 : MachineFunction *MF = MI.getMF();
540 410030 : if (!isSpillInstruction(MI, MF, Reg))
541 409669 : return;
542 :
543 : // Check if the register is the location of a debug value.
544 3728 : for (unsigned ID : OpenRanges.getVarLocs()) {
545 7456 : if (VarLocIDs[ID].isDescribedByReg() == Reg) {
546 : LLVM_DEBUG(dbgs() << "Spilling Register " << printReg(Reg, TRI) << '('
547 : << VarLocIDs[ID].Var.getVar()->getName() << ")\n");
548 270 : insertTransferDebugPair(MI, OpenRanges, Transfers, VarLocIDs, ID);
549 270 : return;
550 : }
551 : }
552 : }
553 :
554 : /// If \p MI is a register copy instruction, that copies a previously tracked
555 : /// value from one register to another register that is callee saved, we
556 : /// create new DBG_VALUE instruction described with copy destination register.
557 410030 : void LiveDebugValues::transferRegisterCopy(MachineInstr &MI,
558 : OpenRangesSet &OpenRanges,
559 : VarLocMap &VarLocIDs,
560 : TransferMap &Transfers) {
561 : const MachineOperand *SrcRegOp, *DestRegOp;
562 :
563 820060 : if (!TII->isCopyInstr(MI, SrcRegOp, DestRegOp) || !SrcRegOp->isKill() ||
564 5724 : !DestRegOp->isDef())
565 409684 : return;
566 :
567 : auto isCalleSavedReg = [&](unsigned Reg) {
568 : for (MCRegAliasIterator RAI(Reg, TRI, true); RAI.isValid(); ++RAI)
569 : if (CalleeSavedRegs.test(*RAI))
570 : return true;
571 : return false;
572 5724 : };
573 :
574 5724 : unsigned SrcReg = SrcRegOp->getReg();
575 5724 : unsigned DestReg = DestRegOp->getReg();
576 :
577 : // We want to recognize instructions where destination register is callee
578 : // saved register. If register that could be clobbered by the call is
579 : // included, there would be a great chance that it is going to be clobbered
580 : // soon. It is more likely that previous register location, which is callee
581 : // saved, is going to stay unclobbered longer, even if it is killed.
582 5724 : if (!isCalleSavedReg(DestReg))
583 : return;
584 :
585 3212 : for (unsigned ID : OpenRanges.getVarLocs()) {
586 6424 : if (VarLocIDs[ID].isDescribedByReg() == SrcReg) {
587 461 : insertTransferDebugPair(MI, OpenRanges, Transfers, VarLocIDs, ID,
588 : DestReg);
589 461 : return;
590 : }
591 : }
592 : }
593 :
594 : /// Terminate all open ranges at the end of the current basic block.
595 0 : bool LiveDebugValues::transferTerminatorInst(MachineInstr &MI,
596 : OpenRangesSet &OpenRanges,
597 : VarLocInMBB &OutLocs,
598 : const VarLocMap &VarLocIDs) {
599 : bool Changed = false;
600 0 : const MachineBasicBlock *CurMBB = MI.getParent();
601 0 : if (!(MI.isTerminator() || (&MI == &CurMBB->back())))
602 0 : return false;
603 :
604 0 : if (OpenRanges.empty())
605 0 : return false;
606 :
607 : LLVM_DEBUG(for (unsigned ID
608 : : OpenRanges.getVarLocs()) {
609 : // Copy OpenRanges to OutLocs, if not already present.
610 : dbgs() << "Add to OutLocs in MBB #" << CurMBB->getNumber() << ": ";
611 : VarLocIDs[ID].dump();
612 : });
613 : VarLocSet &VLS = OutLocs[CurMBB];
614 0 : Changed = VLS |= OpenRanges.getVarLocs();
615 0 : OpenRanges.clear();
616 0 : return Changed;
617 : }
618 :
619 : /// This routine creates OpenRanges and OutLocs.
620 2220777 : bool LiveDebugValues::process(MachineInstr &MI, OpenRangesSet &OpenRanges,
621 : VarLocInMBB &OutLocs, VarLocMap &VarLocIDs,
622 : TransferMap &Transfers, bool transferChanges) {
623 : bool Changed = false;
624 2220777 : transferDebugValue(MI, OpenRanges, VarLocIDs);
625 2220777 : transferRegisterDef(MI, OpenRanges, VarLocIDs);
626 2220777 : if (transferChanges) {
627 410030 : transferRegisterCopy(MI, OpenRanges, VarLocIDs, Transfers);
628 410030 : transferSpillInst(MI, OpenRanges, VarLocIDs, Transfers);
629 : }
630 2220777 : Changed = transferTerminatorInst(MI, OpenRanges, OutLocs, VarLocIDs);
631 2220777 : return Changed;
632 : }
633 :
634 : /// This routine joins the analysis results of all incoming edges in @MBB by
635 : /// inserting a new DBG_VALUE instruction at the start of the @MBB - if the same
636 : /// source variable in all the predecessors of @MBB reside in the same location.
637 0 : bool LiveDebugValues::join(
638 : MachineBasicBlock &MBB, VarLocInMBB &OutLocs, VarLocInMBB &InLocs,
639 : const VarLocMap &VarLocIDs,
640 : SmallPtrSet<const MachineBasicBlock *, 16> &Visited,
641 : SmallPtrSetImpl<const MachineBasicBlock *> &ArtificialBlocks) {
642 : LLVM_DEBUG(dbgs() << "join MBB: " << MBB.getNumber() << "\n");
643 : bool Changed = false;
644 :
645 : VarLocSet InLocsT; // Temporary incoming locations.
646 :
647 : // For all predecessors of this MBB, find the set of VarLocs that
648 : // can be joined.
649 : int NumVisited = 0;
650 0 : for (auto p : MBB.predecessors()) {
651 : // Ignore unvisited predecessor blocks. As we are processing
652 : // the blocks in reverse post-order any unvisited block can
653 : // be considered to not remove any incoming values.
654 0 : if (!Visited.count(p)) {
655 : LLVM_DEBUG(dbgs() << " ignoring unvisited pred MBB: " << p->getNumber()
656 : << "\n");
657 0 : continue;
658 : }
659 0 : auto OL = OutLocs.find(p);
660 : // Join is null in case of empty OutLocs from any of the pred.
661 0 : if (OL == OutLocs.end())
662 0 : return false;
663 :
664 : // Just copy over the Out locs to incoming locs for the first visited
665 : // predecessor, and for all other predecessors join the Out locs.
666 0 : if (!NumVisited)
667 0 : InLocsT = OL->second;
668 : else
669 0 : InLocsT &= OL->second;
670 :
671 : LLVM_DEBUG({
672 : if (!InLocsT.empty()) {
673 : for (auto ID : InLocsT)
674 : dbgs() << " gathered candidate incoming var: "
675 : << VarLocIDs[ID].Var.getVar()->getName() << "\n";
676 : }
677 : });
678 :
679 0 : NumVisited++;
680 : }
681 :
682 : // Filter out DBG_VALUES that are out of scope.
683 : VarLocSet KillSet;
684 0 : bool IsArtificial = ArtificialBlocks.count(&MBB);
685 0 : if (!IsArtificial) {
686 0 : for (auto ID : InLocsT) {
687 0 : if (!VarLocIDs[ID].dominates(MBB)) {
688 0 : KillSet.set(ID);
689 : LLVM_DEBUG({
690 : auto Name = VarLocIDs[ID].Var.getVar()->getName();
691 : dbgs() << " killing " << Name << ", it doesn't dominate MBB\n";
692 : });
693 : }
694 : }
695 : }
696 0 : InLocsT.intersectWithComplement(KillSet);
697 :
698 : // As we are processing blocks in reverse post-order we
699 : // should have processed at least one predecessor, unless it
700 : // is the entry block which has no predecessor.
701 : assert((NumVisited || MBB.pred_empty()) &&
702 : "Should have processed at least one predecessor");
703 0 : if (InLocsT.empty())
704 0 : return false;
705 :
706 0 : VarLocSet &ILS = InLocs[&MBB];
707 :
708 : // Insert DBG_VALUE instructions, if not already inserted.
709 0 : VarLocSet Diff = InLocsT;
710 0 : Diff.intersectWithComplement(ILS);
711 0 : for (auto ID : Diff) {
712 : // This VarLoc is not found in InLocs i.e. it is not yet inserted. So, a
713 : // new range is started for the var from the mbb's beginning by inserting
714 : // a new DBG_VALUE. process() will end this range however appropriate.
715 : const VarLoc &DiffIt = VarLocIDs[ID];
716 0 : const MachineInstr *DMI = &DiffIt.MI;
717 : MachineInstr *MI =
718 0 : BuildMI(MBB, MBB.instr_begin(), DMI->getDebugLoc(), DMI->getDesc(),
719 0 : DMI->isIndirectDebugValue(), DMI->getOperand(0).getReg(),
720 0 : DMI->getDebugVariable(), DMI->getDebugExpression());
721 : if (DMI->isIndirectDebugValue())
722 0 : MI->getOperand(1).setImm(DMI->getOperand(1).getImm());
723 : LLVM_DEBUG(dbgs() << "Inserted: "; MI->dump(););
724 0 : ILS.set(ID);
725 : ++NumInserted;
726 : Changed = true;
727 : }
728 : return Changed;
729 : }
730 :
731 : /// Calculate the liveness information for the given machine function and
732 : /// extend ranges across basic blocks.
733 9672 : bool LiveDebugValues::ExtendRanges(MachineFunction &MF) {
734 : LLVM_DEBUG(dbgs() << "\nDebug Range Extension\n");
735 :
736 : bool Changed = false;
737 : bool OLChanged = false;
738 : bool MBBJoined = false;
739 :
740 : VarLocMap VarLocIDs; // Map VarLoc<>unique ID for use in bitvectors.
741 9672 : OpenRangesSet OpenRanges; // Ranges that are open until end of bb.
742 9672 : VarLocInMBB OutLocs; // Ranges that exist beyond bb.
743 9671 : VarLocInMBB InLocs; // Ranges that are incoming after joining.
744 9672 : TransferMap Transfers; // DBG_VALUEs associated with spills.
745 :
746 : // Blocks which are artificial, i.e. blocks which exclusively contain
747 : // instructions without locations, or with line 0 locations.
748 : SmallPtrSet<const MachineBasicBlock *, 16> ArtificialBlocks;
749 :
750 : DenseMap<unsigned int, MachineBasicBlock *> OrderToBB;
751 : DenseMap<MachineBasicBlock *, unsigned int> BBToOrder;
752 : std::priority_queue<unsigned int, std::vector<unsigned int>,
753 : std::greater<unsigned int>>
754 : Worklist;
755 : std::priority_queue<unsigned int, std::vector<unsigned int>,
756 : std::greater<unsigned int>>
757 : Pending;
758 :
759 : enum : bool { dontTransferChanges = false, transferChanges = true };
760 :
761 : // Initialize every mbb with OutLocs.
762 : // We are not looking at any spill instructions during the initial pass
763 : // over the BBs. The LiveDebugVariables pass has already created DBG_VALUE
764 : // instructions for spills of registers that are known to be user variables
765 : // within the BB in which the spill occurs.
766 240960 : for (auto &MBB : MF)
767 2042035 : for (auto &MI : MBB)
768 1810747 : process(MI, OpenRanges, OutLocs, VarLocIDs, Transfers,
769 : dontTransferChanges);
770 :
771 : auto hasNonArtificialLocation = [](const MachineInstr &MI) -> bool {
772 0 : if (const DebugLoc &DL = MI.getDebugLoc())
773 0 : return DL.getLine() != 0;
774 : return false;
775 : };
776 240960 : for (auto &MBB : MF)
777 231287 : if (none_of(MBB.instrs(), hasNonArtificialLocation))
778 54629 : ArtificialBlocks.insert(&MBB);
779 :
780 : LLVM_DEBUG(printVarLocInMBB(MF, OutLocs, VarLocIDs,
781 : "OutLocs after initialization", dbgs()));
782 :
783 : ReversePostOrderTraversal<MachineFunction *> RPOT(&MF);
784 19344 : unsigned int RPONumber = 0;
785 240953 : for (auto RI = RPOT.begin(), RE = RPOT.end(); RI != RE; ++RI) {
786 231280 : OrderToBB[RPONumber] = *RI;
787 231280 : BBToOrder[*RI] = RPONumber;
788 231280 : Worklist.push(RPONumber);
789 231281 : ++RPONumber;
790 : }
791 : // This is a standard "union of predecessor outs" dataflow problem.
792 : // To solve it, we perform join() and process() using the two worklist method
793 : // until the ranges converge.
794 : // Ranges have converged when both worklists are empty.
795 : SmallPtrSet<const MachineBasicBlock *, 16> Visited;
796 20947 : while (!Worklist.empty() || !Pending.empty()) {
797 : // We track what is on the pending worklist to avoid inserting the same
798 : // thing twice. We could avoid this with a custom priority queue, but this
799 : // is probably not worth it.
800 : SmallPtrSet<MachineBasicBlock *, 16> OnPending;
801 : LLVM_DEBUG(dbgs() << "Processing Worklist\n");
802 278074 : while (!Worklist.empty()) {
803 266798 : MachineBasicBlock *MBB = OrderToBB[Worklist.top()];
804 : Worklist.pop();
805 : MBBJoined =
806 266799 : join(*MBB, OutLocs, InLocs, VarLocIDs, Visited, ArtificialBlocks);
807 266799 : Visited.insert(MBB);
808 266799 : if (MBBJoined) {
809 : MBBJoined = false;
810 : Changed = true;
811 : // Now that we have started to extend ranges across BBs we need to
812 : // examine spill instructions to see whether they spill registers that
813 : // correspond to user variables.
814 448201 : for (auto &MI : *MBB)
815 410030 : OLChanged |= process(MI, OpenRanges, OutLocs, VarLocIDs, Transfers,
816 : transferChanges);
817 :
818 : // Add any DBG_VALUE instructions necessitated by spills.
819 38902 : for (auto &TR : Transfers)
820 731 : MBB->insertAfter(MachineBasicBlock::iterator(*TR.TransferInst),
821 731 : TR.DebugInst);
822 : Transfers.clear();
823 :
824 : LLVM_DEBUG(printVarLocInMBB(MF, OutLocs, VarLocIDs,
825 : "OutLocs after propagating", dbgs()));
826 : LLVM_DEBUG(printVarLocInMBB(MF, InLocs, VarLocIDs,
827 : "InLocs after propagating", dbgs()));
828 :
829 38171 : if (OLChanged) {
830 : OLChanged = false;
831 90494 : for (auto s : MBB->successors())
832 54462 : if (OnPending.insert(s).second) {
833 35518 : Pending.push(BBToOrder[s]);
834 : }
835 : }
836 : }
837 : }
838 : Worklist.swap(Pending);
839 : // At this point, pending must be empty, since it was just the empty
840 : // worklist
841 : assert(Pending.empty() && "Pending should be empty");
842 : }
843 :
844 : LLVM_DEBUG(printVarLocInMBB(MF, OutLocs, VarLocIDs, "Final OutLocs", dbgs()));
845 : LLVM_DEBUG(printVarLocInMBB(MF, InLocs, VarLocIDs, "Final InLocs", dbgs()));
846 9672 : return Changed;
847 : }
848 :
849 401378 : bool LiveDebugValues::runOnMachineFunction(MachineFunction &MF) {
850 401378 : if (!MF.getFunction().getSubprogram())
851 : // LiveDebugValues will already have removed all DBG_VALUEs.
852 : return false;
853 :
854 : // Skip functions from NoDebug compilation units.
855 19376 : if (MF.getFunction().getSubprogram()->getUnit()->getEmissionKind() ==
856 : DICompileUnit::NoDebug)
857 : return false;
858 :
859 9672 : TRI = MF.getSubtarget().getRegisterInfo();
860 9672 : TII = MF.getSubtarget().getInstrInfo();
861 9672 : TFI = MF.getSubtarget().getFrameLowering();
862 9671 : TFI->determineCalleeSaves(MF, CalleeSavedRegs,
863 19344 : make_unique<RegScavenger>().get());
864 9672 : LS.initialize(MF);
865 :
866 9672 : bool Changed = ExtendRanges(MF);
867 9672 : return Changed;
868 : }
|
