1//===- InstrRefBasedImpl.h - Tracking Debug Value MIs ---------------------===//
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#ifndef LLVM_LIB_CODEGEN_LIVEDEBUGVALUES_INSTRREFBASEDLDV_H
10#define LLVM_LIB_CODEGEN_LIVEDEBUGVALUES_INSTRREFBASEDLDV_H
11
12#include "llvm/ADT/DenseMap.h"
13#include "llvm/ADT/IndexedMap.h"
14#include "llvm/ADT/SmallPtrSet.h"
15#include "llvm/ADT/SmallVector.h"
16#include "llvm/ADT/UniqueVector.h"
17#include "llvm/CodeGen/LexicalScopes.h"
18#include "llvm/CodeGen/MachineBasicBlock.h"
19#include "llvm/CodeGen/MachineInstr.h"
20#include "llvm/CodeGen/TargetRegisterInfo.h"
21#include "llvm/IR/DebugInfoMetadata.h"
22#include <optional>
23
24#include "LiveDebugValues.h"
25
26class TransferTracker;
27
28// Forward dec of unit test class, so that we can peer into the LDV object.
29class InstrRefLDVTest;
30
31namespace LiveDebugValues {
32
33class MLocTracker;
34class DbgOpIDMap;
35
36using namespace llvm;
37
38using DebugVariableID = unsigned;
39using VarAndLoc = std::pair<DebugVariable, const DILocation *>;
40
41/// Mapping from DebugVariable to/from a unique identifying number. Each
42/// DebugVariable consists of three pointers, and after a small amount of
43/// work to identify overlapping fragments of variables we mostly only use
44/// DebugVariables as identities of variables. It's much more compile-time
45/// efficient to use an ID number instead, which this class provides.
46class DebugVariableMap {
47 DenseMap<DebugVariable, unsigned> VarToIdx;
48 SmallVector<VarAndLoc> IdxToVar;
49
50public:
51 DebugVariableID getDVID(const DebugVariable &Var) const {
52 auto It = VarToIdx.find(Val: Var);
53 assert(It != VarToIdx.end());
54 return It->second;
55 }
56
57 DebugVariableID insertDVID(DebugVariable &Var, const DILocation *Loc) {
58 unsigned Size = VarToIdx.size();
59 auto ItPair = VarToIdx.insert(KV: {Var, Size});
60 if (ItPair.second) {
61 IdxToVar.push_back(Elt: {Var, Loc});
62 return Size;
63 }
64
65 return ItPair.first->second;
66 }
67
68 const VarAndLoc &lookupDVID(DebugVariableID ID) const { return IdxToVar[ID]; }
69
70 void clear() {
71 VarToIdx.clear();
72 IdxToVar.clear();
73 }
74};
75
76/// Handle-class for a particular "location". This value-type uniquely
77/// symbolises a register or stack location, allowing manipulation of locations
78/// without concern for where that location is. Practically, this allows us to
79/// treat the state of the machine at a particular point as an array of values,
80/// rather than a map of values.
81class LocIdx {
82 unsigned Location;
83
84 // Default constructor is private, initializing to an illegal location number.
85 // Use only for "not an entry" elements in IndexedMaps.
86 LocIdx() : Location(UINT_MAX) {}
87
88public:
89#define NUM_LOC_BITS 24
90 LocIdx(unsigned L) : Location(L) {
91 assert(L < (1 << NUM_LOC_BITS) && "Machine locations must fit in 24 bits");
92 }
93
94 static LocIdx MakeIllegalLoc() { return LocIdx(); }
95 static LocIdx MakeTombstoneLoc() {
96 LocIdx L = LocIdx();
97 --L.Location;
98 return L;
99 }
100
101 bool isIllegal() const { return Location == UINT_MAX; }
102
103 uint64_t asU64() const { return Location; }
104
105 bool operator==(unsigned L) const { return Location == L; }
106
107 bool operator==(const LocIdx &L) const { return Location == L.Location; }
108
109 bool operator!=(unsigned L) const { return !(*this == L); }
110
111 bool operator!=(const LocIdx &L) const { return !(*this == L); }
112
113 bool operator<(const LocIdx &Other) const {
114 return Location < Other.Location;
115 }
116};
117
118// The location at which a spilled value resides. It consists of a register and
119// an offset.
120struct SpillLoc {
121 unsigned SpillBase;
122 StackOffset SpillOffset;
123 bool operator==(const SpillLoc &Other) const {
124 return std::make_pair(x: SpillBase, y: SpillOffset) ==
125 std::make_pair(x: Other.SpillBase, y: Other.SpillOffset);
126 }
127 bool operator<(const SpillLoc &Other) const {
128 return std::make_tuple(args: SpillBase, args: SpillOffset.getFixed(),
129 args: SpillOffset.getScalable()) <
130 std::make_tuple(args: Other.SpillBase, args: Other.SpillOffset.getFixed(),
131 args: Other.SpillOffset.getScalable());
132 }
133};
134
135/// Unique identifier for a value defined by an instruction, as a value type.
136/// Casts back and forth to a uint64_t. Probably replacable with something less
137/// bit-constrained. Each value identifies the instruction and machine location
138/// where the value is defined, although there may be no corresponding machine
139/// operand for it (ex: regmasks clobbering values). The instructions are
140/// one-based, and definitions that are PHIs have instruction number zero.
141///
142/// The obvious limits of a 1M block function or 1M instruction blocks are
143/// problematic; but by that point we should probably have bailed out of
144/// trying to analyse the function.
145class ValueIDNum {
146 union {
147 struct {
148 uint64_t BlockNo : 20; /// The block where the def happens.
149 uint64_t InstNo : 20; /// The Instruction where the def happens.
150 /// One based, is distance from start of block.
151 uint64_t LocNo
152 : NUM_LOC_BITS; /// The machine location where the def happens.
153 } s;
154 uint64_t Value;
155 } u;
156
157 static_assert(sizeof(u) == 8, "Badly packed ValueIDNum?");
158
159public:
160 // Default-initialize to EmptyValue. This is necessary to make IndexedMaps
161 // of values to work.
162 ValueIDNum() { u.Value = EmptyValue.asU64(); }
163
164 ValueIDNum(uint64_t Block, uint64_t Inst, uint64_t Loc) {
165 u.s = {.BlockNo: Block, .InstNo: Inst, .LocNo: Loc};
166 }
167
168 ValueIDNum(uint64_t Block, uint64_t Inst, LocIdx Loc) {
169 u.s = {.BlockNo: Block, .InstNo: Inst, .LocNo: Loc.asU64()};
170 }
171
172 uint64_t getBlock() const { return u.s.BlockNo; }
173 uint64_t getInst() const { return u.s.InstNo; }
174 uint64_t getLoc() const { return u.s.LocNo; }
175 bool isPHI() const { return u.s.InstNo == 0; }
176
177 uint64_t asU64() const { return u.Value; }
178
179 static ValueIDNum fromU64(uint64_t v) {
180 ValueIDNum Val;
181 Val.u.Value = v;
182 return Val;
183 }
184
185 bool operator<(const ValueIDNum &Other) const {
186 return asU64() < Other.asU64();
187 }
188
189 bool operator==(const ValueIDNum &Other) const {
190 return u.Value == Other.u.Value;
191 }
192
193 bool operator!=(const ValueIDNum &Other) const { return !(*this == Other); }
194
195 std::string asString(const std::string &mlocname) const {
196 return Twine("Value{bb: ")
197 .concat(Suffix: Twine(u.s.BlockNo)
198 .concat(Suffix: Twine(", inst: ")
199 .concat(Suffix: (u.s.InstNo ? Twine(u.s.InstNo)
200 : Twine("live-in"))
201 .concat(Suffix: Twine(", loc: ").concat(
202 Suffix: Twine(mlocname)))
203 .concat(Suffix: Twine("}")))))
204 .str();
205 }
206
207 static ValueIDNum EmptyValue;
208 static ValueIDNum TombstoneValue;
209};
210
211} // End namespace LiveDebugValues
212
213namespace llvm {
214using namespace LiveDebugValues;
215
216template <> struct DenseMapInfo<LocIdx> {
217 static inline LocIdx getEmptyKey() { return LocIdx::MakeIllegalLoc(); }
218 static inline LocIdx getTombstoneKey() { return LocIdx::MakeTombstoneLoc(); }
219
220 static unsigned getHashValue(const LocIdx &Loc) { return Loc.asU64(); }
221
222 static bool isEqual(const LocIdx &A, const LocIdx &B) { return A == B; }
223};
224
225template <> struct DenseMapInfo<ValueIDNum> {
226 static inline ValueIDNum getEmptyKey() { return ValueIDNum::EmptyValue; }
227 static inline ValueIDNum getTombstoneKey() {
228 return ValueIDNum::TombstoneValue;
229 }
230
231 static unsigned getHashValue(const ValueIDNum &Val) {
232 return hash_value(value: Val.asU64());
233 }
234
235 static bool isEqual(const ValueIDNum &A, const ValueIDNum &B) {
236 return A == B;
237 }
238};
239
240} // end namespace llvm
241
242namespace LiveDebugValues {
243using namespace llvm;
244
245/// Type for a table of values in a block.
246using ValueTable = SmallVector<ValueIDNum, 0>;
247
248/// A collection of ValueTables, one per BB in a function, with convenient
249/// accessor methods.
250struct FuncValueTable {
251 FuncValueTable(int NumBBs, int NumLocs) {
252 Storage.reserve(N: NumBBs);
253 for (int i = 0; i != NumBBs; ++i)
254 Storage.push_back(
255 Elt: std::make_unique<ValueTable>(args&: NumLocs, args&: ValueIDNum::EmptyValue));
256 }
257
258 /// Returns the ValueTable associated with MBB.
259 ValueTable &operator[](const MachineBasicBlock &MBB) const {
260 return (*this)[MBB.getNumber()];
261 }
262
263 /// Returns the ValueTable associated with the MachineBasicBlock whose number
264 /// is MBBNum.
265 ValueTable &operator[](int MBBNum) const {
266 auto &TablePtr = Storage[MBBNum];
267 assert(TablePtr && "Trying to access a deleted table");
268 return *TablePtr;
269 }
270
271 /// Returns the ValueTable associated with the entry MachineBasicBlock.
272 ValueTable &tableForEntryMBB() const { return (*this)[0]; }
273
274 /// Returns true if the ValueTable associated with MBB has not been freed.
275 bool hasTableFor(MachineBasicBlock &MBB) const {
276 return Storage[MBB.getNumber()] != nullptr;
277 }
278
279 /// Frees the memory of the ValueTable associated with MBB.
280 void ejectTableForBlock(const MachineBasicBlock &MBB) {
281 Storage[MBB.getNumber()].reset();
282 }
283
284private:
285 /// ValueTables are stored as unique_ptrs to allow for deallocation during
286 /// LDV; this was measured to have a significant impact on compiler memory
287 /// usage.
288 SmallVector<std::unique_ptr<ValueTable>, 0> Storage;
289};
290
291/// Thin wrapper around an integer -- designed to give more type safety to
292/// spill location numbers.
293class SpillLocationNo {
294public:
295 explicit SpillLocationNo(unsigned SpillNo) : SpillNo(SpillNo) {}
296 unsigned SpillNo;
297 unsigned id() const { return SpillNo; }
298
299 bool operator<(const SpillLocationNo &Other) const {
300 return SpillNo < Other.SpillNo;
301 }
302
303 bool operator==(const SpillLocationNo &Other) const {
304 return SpillNo == Other.SpillNo;
305 }
306 bool operator!=(const SpillLocationNo &Other) const {
307 return !(*this == Other);
308 }
309};
310
311/// Meta qualifiers for a value. Pair of whatever expression is used to qualify
312/// the value, and Boolean of whether or not it's indirect.
313class DbgValueProperties {
314public:
315 DbgValueProperties(const DIExpression *DIExpr, bool Indirect, bool IsVariadic)
316 : DIExpr(DIExpr), Indirect(Indirect), IsVariadic(IsVariadic) {}
317
318 /// Extract properties from an existing DBG_VALUE instruction.
319 DbgValueProperties(const MachineInstr &MI) {
320 assert(MI.isDebugValue());
321 assert(MI.getDebugExpression()->getNumLocationOperands() == 0 ||
322 MI.isDebugValueList() || MI.isUndefDebugValue());
323 IsVariadic = MI.isDebugValueList();
324 DIExpr = MI.getDebugExpression();
325 Indirect = MI.isDebugOffsetImm();
326 }
327
328 bool isJoinable(const DbgValueProperties &Other) const {
329 return DIExpression::isEqualExpression(FirstExpr: DIExpr, FirstIndirect: Indirect, SecondExpr: Other.DIExpr,
330 SecondIndirect: Other.Indirect);
331 }
332
333 bool operator==(const DbgValueProperties &Other) const {
334 return std::tie(args: DIExpr, args: Indirect, args: IsVariadic) ==
335 std::tie(args: Other.DIExpr, args: Other.Indirect, args: Other.IsVariadic);
336 }
337
338 bool operator!=(const DbgValueProperties &Other) const {
339 return !(*this == Other);
340 }
341
342 unsigned getLocationOpCount() const {
343 return IsVariadic ? DIExpr->getNumLocationOperands() : 1;
344 }
345
346 const DIExpression *DIExpr;
347 bool Indirect;
348 bool IsVariadic;
349};
350
351/// TODO: Might pack better if we changed this to a Struct of Arrays, since
352/// MachineOperand is width 32, making this struct width 33. We could also
353/// potentially avoid storing the whole MachineOperand (sizeof=32), instead
354/// choosing to store just the contents portion (sizeof=8) and a Kind enum,
355/// since we already know it is some type of immediate value.
356/// Stores a single debug operand, which can either be a MachineOperand for
357/// directly storing immediate values, or a ValueIDNum representing some value
358/// computed at some point in the program. IsConst is used as a discriminator.
359struct DbgOp {
360 union {
361 ValueIDNum ID;
362 MachineOperand MO;
363 };
364 bool IsConst;
365
366 DbgOp() : ID(ValueIDNum::EmptyValue), IsConst(false) {}
367 DbgOp(ValueIDNum ID) : ID(ID), IsConst(false) {}
368 DbgOp(MachineOperand MO) : MO(MO), IsConst(true) {}
369
370 bool isUndef() const { return !IsConst && ID == ValueIDNum::EmptyValue; }
371
372#ifndef NDEBUG
373 void dump(const MLocTracker *MTrack) const;
374#endif
375};
376
377/// A DbgOp whose ID (if any) has resolved to an actual location, LocIdx. Used
378/// when working with concrete debug values, i.e. when joining MLocs and VLocs
379/// in the TransferTracker or emitting DBG_VALUE/DBG_VALUE_LIST instructions in
380/// the MLocTracker.
381struct ResolvedDbgOp {
382 union {
383 LocIdx Loc;
384 MachineOperand MO;
385 };
386 bool IsConst;
387
388 ResolvedDbgOp(LocIdx Loc) : Loc(Loc), IsConst(false) {}
389 ResolvedDbgOp(MachineOperand MO) : MO(MO), IsConst(true) {}
390
391 bool operator==(const ResolvedDbgOp &Other) const {
392 if (IsConst != Other.IsConst)
393 return false;
394 if (IsConst)
395 return MO.isIdenticalTo(Other: Other.MO);
396 return Loc == Other.Loc;
397 }
398
399#ifndef NDEBUG
400 void dump(const MLocTracker *MTrack) const;
401#endif
402};
403
404/// An ID used in the DbgOpIDMap (below) to lookup a stored DbgOp. This is used
405/// in place of actual DbgOps inside of a DbgValue to reduce its size, as
406/// DbgValue is very frequently used and passed around, and the actual DbgOp is
407/// over 8x larger than this class, due to storing a MachineOperand. This ID
408/// should be equal for all equal DbgOps, and also encodes whether the mapped
409/// DbgOp is a constant, meaning that for simple equality or const-ness checks
410/// it is not necessary to lookup this ID.
411struct DbgOpID {
412 struct IsConstIndexPair {
413 uint32_t IsConst : 1;
414 uint32_t Index : 31;
415 };
416
417 union {
418 struct IsConstIndexPair ID;
419 uint32_t RawID;
420 };
421
422 DbgOpID() : RawID(UndefID.RawID) {
423 static_assert(sizeof(DbgOpID) == 4, "DbgOpID should fit within 4 bytes.");
424 }
425 DbgOpID(uint32_t RawID) : RawID(RawID) {}
426 DbgOpID(bool IsConst, uint32_t Index) : ID({.IsConst: IsConst, .Index: Index}) {}
427
428 static DbgOpID UndefID;
429
430 bool operator==(const DbgOpID &Other) const { return RawID == Other.RawID; }
431 bool operator!=(const DbgOpID &Other) const { return !(*this == Other); }
432
433 uint32_t asU32() const { return RawID; }
434
435 bool isUndef() const { return *this == UndefID; }
436 bool isConst() const { return ID.IsConst && !isUndef(); }
437 uint32_t getIndex() const { return ID.Index; }
438
439#ifndef NDEBUG
440 void dump(const MLocTracker *MTrack, const DbgOpIDMap *OpStore) const;
441#endif
442};
443
444/// Class storing the complete set of values that are observed by DbgValues
445/// within the current function. Allows 2-way lookup, with `find` returning the
446/// Op for a given ID and `insert` returning the ID for a given Op (creating one
447/// if none exists).
448class DbgOpIDMap {
449
450 SmallVector<ValueIDNum, 0> ValueOps;
451 SmallVector<MachineOperand, 0> ConstOps;
452
453 DenseMap<ValueIDNum, DbgOpID> ValueOpToID;
454 DenseMap<MachineOperand, DbgOpID> ConstOpToID;
455
456public:
457 /// If \p Op does not already exist in this map, it is inserted and the
458 /// corresponding DbgOpID is returned. If Op already exists in this map, then
459 /// no change is made and the existing ID for Op is returned.
460 /// Calling this with the undef DbgOp will always return DbgOpID::UndefID.
461 DbgOpID insert(DbgOp Op) {
462 if (Op.isUndef())
463 return DbgOpID::UndefID;
464 if (Op.IsConst)
465 return insertConstOp(MO&: Op.MO);
466 return insertValueOp(VID: Op.ID);
467 }
468 /// Returns the DbgOp associated with \p ID. Should only be used for IDs
469 /// returned from calling `insert` from this map or DbgOpID::UndefID.
470 DbgOp find(DbgOpID ID) const {
471 if (ID == DbgOpID::UndefID)
472 return DbgOp();
473 if (ID.isConst())
474 return DbgOp(ConstOps[ID.getIndex()]);
475 return DbgOp(ValueOps[ID.getIndex()]);
476 }
477
478 void clear() {
479 ValueOps.clear();
480 ConstOps.clear();
481 ValueOpToID.clear();
482 ConstOpToID.clear();
483 }
484
485private:
486 DbgOpID insertConstOp(MachineOperand &MO) {
487 auto [It, Inserted] = ConstOpToID.try_emplace(Key: MO, Args: true, Args: ConstOps.size());
488 if (Inserted)
489 ConstOps.push_back(Elt: MO);
490 return It->second;
491 }
492 DbgOpID insertValueOp(ValueIDNum VID) {
493 auto [It, Inserted] = ValueOpToID.try_emplace(Key: VID, Args: false, Args: ValueOps.size());
494 if (Inserted)
495 ValueOps.push_back(Elt: VID);
496 return It->second;
497 }
498};
499
500// We set the maximum number of operands that we will handle to keep DbgValue
501// within a reasonable size (64 bytes), as we store and pass a lot of them
502// around.
503#define MAX_DBG_OPS 8
504
505/// Class recording the (high level) _value_ of a variable. Identifies the value
506/// of the variable as a list of ValueIDNums and constant MachineOperands, or as
507/// an empty list for undef debug values or VPHI values which we have not found
508/// valid locations for.
509/// This class also stores meta-information about how the value is qualified.
510/// Used to reason about variable values when performing the second
511/// (DebugVariable specific) dataflow analysis.
512class DbgValue {
513private:
514 /// If Kind is Def or VPHI, the set of IDs corresponding to the DbgOps that
515 /// are used. VPHIs set every ID to EmptyID when we have not found a valid
516 /// machine-value for every operand, and sets them to the corresponding
517 /// machine-values when we have found all of them.
518 DbgOpID DbgOps[MAX_DBG_OPS];
519 unsigned OpCount;
520
521public:
522 /// For a NoVal or VPHI DbgValue, which block it was generated in.
523 int BlockNo;
524
525 /// Qualifiers for the ValueIDNum above.
526 DbgValueProperties Properties;
527
528 typedef enum {
529 Undef, // Represents a DBG_VALUE $noreg in the transfer function only.
530 Def, // This value is defined by some combination of constants,
531 // instructions, or PHI values.
532 VPHI, // Incoming values to BlockNo differ, those values must be joined by
533 // a PHI in this block.
534 NoVal, // Empty DbgValue indicating an unknown value. Used as initializer,
535 // before dominating blocks values are propagated in.
536 } KindT;
537 /// Discriminator for whether this is a constant or an in-program value.
538 KindT Kind;
539
540 DbgValue(ArrayRef<DbgOpID> DbgOps, const DbgValueProperties &Prop)
541 : OpCount(DbgOps.size()), BlockNo(0), Properties(Prop), Kind(Def) {
542 static_assert(sizeof(DbgValue) <= 64,
543 "DbgValue should fit within 64 bytes.");
544 assert(DbgOps.size() == Prop.getLocationOpCount());
545 if (DbgOps.size() > MAX_DBG_OPS ||
546 any_of(Range&: DbgOps, P: [](DbgOpID ID) { return ID.isUndef(); })) {
547 Kind = Undef;
548 OpCount = 0;
549#define DEBUG_TYPE "LiveDebugValues"
550 if (DbgOps.size() > MAX_DBG_OPS) {
551 LLVM_DEBUG(dbgs() << "Found DbgValue with more than maximum allowed "
552 "operands.\n");
553 }
554#undef DEBUG_TYPE
555 } else {
556 for (unsigned Idx = 0; Idx < DbgOps.size(); ++Idx)
557 this->DbgOps[Idx] = DbgOps[Idx];
558 }
559 }
560
561 DbgValue(unsigned BlockNo, const DbgValueProperties &Prop, KindT Kind)
562 : OpCount(0), BlockNo(BlockNo), Properties(Prop), Kind(Kind) {
563 assert(Kind == NoVal || Kind == VPHI);
564 }
565
566 DbgValue(const DbgValueProperties &Prop, KindT Kind)
567 : OpCount(0), BlockNo(0), Properties(Prop), Kind(Kind) {
568 assert(Kind == Undef &&
569 "Empty DbgValue constructor must pass in Undef kind");
570 }
571
572#ifndef NDEBUG
573 void dump(const MLocTracker *MTrack = nullptr,
574 const DbgOpIDMap *OpStore = nullptr) const;
575#endif
576
577 bool operator==(const DbgValue &Other) const {
578 if (std::tie(args: Kind, args: Properties) != std::tie(args: Other.Kind, args: Other.Properties))
579 return false;
580 else if (Kind == Def && !equal(LRange: getDbgOpIDs(), RRange: Other.getDbgOpIDs()))
581 return false;
582 else if (Kind == NoVal && BlockNo != Other.BlockNo)
583 return false;
584 else if (Kind == VPHI && BlockNo != Other.BlockNo)
585 return false;
586 else if (Kind == VPHI && !equal(LRange: getDbgOpIDs(), RRange: Other.getDbgOpIDs()))
587 return false;
588
589 return true;
590 }
591
592 bool operator!=(const DbgValue &Other) const { return !(*this == Other); }
593
594 // Returns an array of all the machine values used to calculate this variable
595 // value, or an empty list for an Undef or unjoined VPHI.
596 ArrayRef<DbgOpID> getDbgOpIDs() const { return {DbgOps, OpCount}; }
597
598 // Returns either DbgOps[Index] if this DbgValue has Debug Operands, or
599 // the ID for ValueIDNum::EmptyValue otherwise (i.e. if this is an Undef,
600 // NoVal, or an unjoined VPHI).
601 DbgOpID getDbgOpID(unsigned Index) const {
602 if (!OpCount)
603 return DbgOpID::UndefID;
604 assert(Index < OpCount);
605 return DbgOps[Index];
606 }
607 // Replaces this DbgValue's existing DbgOpIDs (if any) with the contents of
608 // \p NewIDs. The number of DbgOpIDs passed must be equal to the number of
609 // arguments expected by this DbgValue's properties (the return value of
610 // `getLocationOpCount()`).
611 void setDbgOpIDs(ArrayRef<DbgOpID> NewIDs) {
612 // We can go from no ops to some ops, but not from some ops to no ops.
613 assert(NewIDs.size() == getLocationOpCount() &&
614 "Incorrect number of Debug Operands for this DbgValue.");
615 OpCount = NewIDs.size();
616 for (unsigned Idx = 0; Idx < NewIDs.size(); ++Idx)
617 DbgOps[Idx] = NewIDs[Idx];
618 }
619
620 // The number of debug operands expected by this DbgValue's expression.
621 // getDbgOpIDs() should return an array of this length, unless this is an
622 // Undef or an unjoined VPHI.
623 unsigned getLocationOpCount() const {
624 return Properties.getLocationOpCount();
625 }
626
627 // Returns true if this or Other are unjoined PHIs, which do not have defined
628 // Loc Ops, or if the `n`th Loc Op for this has a different constness to the
629 // `n`th Loc Op for Other.
630 bool hasJoinableLocOps(const DbgValue &Other) const {
631 if (isUnjoinedPHI() || Other.isUnjoinedPHI())
632 return true;
633 for (unsigned Idx = 0; Idx < getLocationOpCount(); ++Idx) {
634 if (getDbgOpID(Index: Idx).isConst() != Other.getDbgOpID(Index: Idx).isConst())
635 return false;
636 }
637 return true;
638 }
639
640 bool isUnjoinedPHI() const { return Kind == VPHI && OpCount == 0; }
641
642 bool hasIdenticalValidLocOps(const DbgValue &Other) const {
643 if (!OpCount)
644 return false;
645 return equal(LRange: getDbgOpIDs(), RRange: Other.getDbgOpIDs());
646 }
647};
648
649class LocIdxToIndexFunctor {
650public:
651 using argument_type = LocIdx;
652 unsigned operator()(const LocIdx &L) const { return L.asU64(); }
653};
654
655/// Tracker for what values are in machine locations. Listens to the Things
656/// being Done by various instructions, and maintains a table of what machine
657/// locations have what values (as defined by a ValueIDNum).
658///
659/// There are potentially a much larger number of machine locations on the
660/// target machine than the actual working-set size of the function. On x86 for
661/// example, we're extremely unlikely to want to track values through control
662/// or debug registers. To avoid doing so, MLocTracker has several layers of
663/// indirection going on, described below, to avoid unnecessarily tracking
664/// any location.
665///
666/// Here's a sort of diagram of the indexes, read from the bottom up:
667///
668/// Size on stack Offset on stack
669/// \ /
670/// Stack Idx (Where in slot is this?)
671/// /
672/// /
673/// Slot Num (%stack.0) /
674/// FrameIdx => SpillNum /
675/// \ /
676/// SpillID (int) Register number (int)
677/// \ /
678/// LocationID => LocIdx
679/// |
680/// LocIdx => ValueIDNum
681///
682/// The aim here is that the LocIdx => ValueIDNum vector is just an array of
683/// values in numbered locations, so that later analyses can ignore whether the
684/// location is a register or otherwise. To map a register / spill location to
685/// a LocIdx, you have to use the (sparse) LocationID => LocIdx map. And to
686/// build a LocationID for a stack slot, you need to combine identifiers for
687/// which stack slot it is and where within that slot is being described.
688///
689/// Register mask operands cause trouble by technically defining every register;
690/// various hacks are used to avoid tracking registers that are never read and
691/// only written by regmasks.
692class MLocTracker {
693public:
694 MachineFunction &MF;
695 const TargetInstrInfo &TII;
696 const TargetRegisterInfo &TRI;
697 const TargetLowering &TLI;
698
699 /// IndexedMap type, mapping from LocIdx to ValueIDNum.
700 using LocToValueType = IndexedMap<ValueIDNum, LocIdxToIndexFunctor>;
701
702 /// Map of LocIdxes to the ValueIDNums that they store. This is tightly
703 /// packed, entries only exist for locations that are being tracked.
704 LocToValueType LocIdxToIDNum;
705
706 /// "Map" of machine location IDs (i.e., raw register or spill number) to the
707 /// LocIdx key / number for that location. There are always at least as many
708 /// as the number of registers on the target -- if the value in the register
709 /// is not being tracked, then the LocIdx value will be zero. New entries are
710 /// appended if a new spill slot begins being tracked.
711 /// This, and the corresponding reverse map persist for the analysis of the
712 /// whole function, and is necessarying for decoding various vectors of
713 /// values.
714 std::vector<LocIdx> LocIDToLocIdx;
715
716 /// Inverse map of LocIDToLocIdx.
717 IndexedMap<unsigned, LocIdxToIndexFunctor> LocIdxToLocID;
718
719 /// When clobbering register masks, we chose to not believe the machine model
720 /// and don't clobber SP. Do the same for SP aliases, and for efficiency,
721 /// keep a set of them here.
722 SmallSet<Register, 8> SPAliases;
723
724 /// Unique-ification of spill. Used to number them -- their LocID number is
725 /// the index in SpillLocs minus one plus NumRegs.
726 UniqueVector<SpillLoc> SpillLocs;
727
728 // If we discover a new machine location, assign it an mphi with this
729 // block number.
730 unsigned CurBB = -1;
731
732 /// Cached local copy of the number of registers the target has.
733 unsigned NumRegs;
734
735 /// Number of slot indexes the target has -- distinct segments of a stack
736 /// slot that can take on the value of a subregister, when a super-register
737 /// is written to the stack.
738 unsigned NumSlotIdxes;
739
740 /// Collection of register mask operands that have been observed. Second part
741 /// of pair indicates the instruction that they happened in. Used to
742 /// reconstruct where defs happened if we start tracking a location later
743 /// on.
744 SmallVector<std::pair<const MachineOperand *, unsigned>, 32> Masks;
745
746 /// Pair for describing a position within a stack slot -- first the size in
747 /// bits, then the offset.
748 typedef std::pair<unsigned short, unsigned short> StackSlotPos;
749
750 /// Map from a size/offset pair describing a position in a stack slot, to a
751 /// numeric identifier for that position. Allows easier identification of
752 /// individual positions.
753 DenseMap<StackSlotPos, unsigned> StackSlotIdxes;
754
755 /// Inverse of StackSlotIdxes.
756 DenseMap<unsigned, StackSlotPos> StackIdxesToPos;
757
758 /// Iterator for locations and the values they contain. Dereferencing
759 /// produces a struct/pair containing the LocIdx key for this location,
760 /// and a reference to the value currently stored. Simplifies the process
761 /// of seeking a particular location.
762 class MLocIterator {
763 LocToValueType &ValueMap;
764 LocIdx Idx;
765
766 public:
767 class value_type {
768 public:
769 value_type(LocIdx Idx, ValueIDNum &Value) : Idx(Idx), Value(Value) {}
770 const LocIdx Idx; /// Read-only index of this location.
771 ValueIDNum &Value; /// Reference to the stored value at this location.
772 };
773
774 MLocIterator(LocToValueType &ValueMap, LocIdx Idx)
775 : ValueMap(ValueMap), Idx(Idx) {}
776
777 bool operator==(const MLocIterator &Other) const {
778 assert(&ValueMap == &Other.ValueMap);
779 return Idx == Other.Idx;
780 }
781
782 bool operator!=(const MLocIterator &Other) const {
783 return !(*this == Other);
784 }
785
786 void operator++() { Idx = LocIdx(Idx.asU64() + 1); }
787
788 value_type operator*() { return value_type(Idx, ValueMap[LocIdx(Idx)]); }
789 };
790
791 MLocTracker(MachineFunction &MF, const TargetInstrInfo &TII,
792 const TargetRegisterInfo &TRI, const TargetLowering &TLI);
793
794 /// Produce location ID number for a Register. Provides some small amount of
795 /// type safety.
796 /// \param Reg The register we're looking up.
797 unsigned getLocID(Register Reg) { return Reg.id(); }
798
799 /// Produce location ID number for a spill position.
800 /// \param Spill The number of the spill we're fetching the location for.
801 /// \param SpillSubReg Subregister within the spill we're addressing.
802 unsigned getLocID(SpillLocationNo Spill, unsigned SpillSubReg) {
803 unsigned short Size = TRI.getSubRegIdxSize(Idx: SpillSubReg);
804 unsigned short Offs = TRI.getSubRegIdxOffset(Idx: SpillSubReg);
805 return getLocID(Spill, Idx: {Size, Offs});
806 }
807
808 /// Produce location ID number for a spill position.
809 /// \param Spill The number of the spill we're fetching the location for.
810 /// \apram SpillIdx size/offset within the spill slot to be addressed.
811 unsigned getLocID(SpillLocationNo Spill, StackSlotPos Idx) {
812 unsigned SlotNo = Spill.id() - 1;
813 SlotNo *= NumSlotIdxes;
814 assert(StackSlotIdxes.contains(Idx));
815 SlotNo += StackSlotIdxes[Idx];
816 SlotNo += NumRegs;
817 return SlotNo;
818 }
819
820 /// Given a spill number, and a slot within the spill, calculate the ID number
821 /// for that location.
822 unsigned getSpillIDWithIdx(SpillLocationNo Spill, unsigned Idx) {
823 unsigned SlotNo = Spill.id() - 1;
824 SlotNo *= NumSlotIdxes;
825 SlotNo += Idx;
826 SlotNo += NumRegs;
827 return SlotNo;
828 }
829
830 /// Return the spill number that a location ID corresponds to.
831 SpillLocationNo locIDToSpill(unsigned ID) const {
832 assert(ID >= NumRegs);
833 ID -= NumRegs;
834 // Truncate away the index part, leaving only the spill number.
835 ID /= NumSlotIdxes;
836 return SpillLocationNo(ID + 1); // The UniqueVector is one-based.
837 }
838
839 /// Returns the spill-slot size/offs that a location ID corresponds to.
840 StackSlotPos locIDToSpillIdx(unsigned ID) const {
841 assert(ID >= NumRegs);
842 ID -= NumRegs;
843 unsigned Idx = ID % NumSlotIdxes;
844 return StackIdxesToPos.find(Val: Idx)->second;
845 }
846
847 unsigned getNumLocs() const { return LocIdxToIDNum.size(); }
848
849 /// Reset all locations to contain a PHI value at the designated block. Used
850 /// sometimes for actual PHI values, othertimes to indicate the block entry
851 /// value (before any more information is known).
852 void setMPhis(unsigned NewCurBB) {
853 CurBB = NewCurBB;
854 for (auto Location : locations())
855 Location.Value = {CurBB, 0, Location.Idx};
856 }
857
858 /// Load values for each location from array of ValueIDNums. Take current
859 /// bbnum just in case we read a value from a hitherto untouched register.
860 void loadFromArray(ValueTable &Locs, unsigned NewCurBB) {
861 CurBB = NewCurBB;
862 // Iterate over all tracked locations, and load each locations live-in
863 // value into our local index.
864 for (auto Location : locations())
865 Location.Value = Locs[Location.Idx.asU64()];
866 }
867
868 /// Wipe any un-necessary location records after traversing a block.
869 void reset() {
870 // We could reset all the location values too; however either loadFromArray
871 // or setMPhis should be called before this object is re-used. Just
872 // clear Masks, they're definitely not needed.
873 Masks.clear();
874 }
875
876 /// Clear all data. Destroys the LocID <=> LocIdx map, which makes most of
877 /// the information in this pass uninterpretable.
878 void clear() {
879 reset();
880 LocIDToLocIdx.clear();
881 LocIdxToLocID.clear();
882 LocIdxToIDNum.clear();
883 // SpillLocs.reset(); XXX UniqueVector::reset assumes a SpillLoc casts from
884 // 0
885 SpillLocs = decltype(SpillLocs)();
886 StackSlotIdxes.clear();
887 StackIdxesToPos.clear();
888
889 LocIDToLocIdx.resize(new_size: NumRegs, x: LocIdx::MakeIllegalLoc());
890 }
891
892 /// Set a locaiton to a certain value.
893 void setMLoc(LocIdx L, ValueIDNum Num) {
894 assert(L.asU64() < LocIdxToIDNum.size());
895 LocIdxToIDNum[L] = Num;
896 }
897
898 /// Read the value of a particular location
899 ValueIDNum readMLoc(LocIdx L) {
900 assert(L.asU64() < LocIdxToIDNum.size());
901 return LocIdxToIDNum[L];
902 }
903
904 /// Create a LocIdx for an untracked register ID. Initialize it to either an
905 /// mphi value representing a live-in, or a recent register mask clobber.
906 LocIdx trackRegister(unsigned ID);
907
908 LocIdx lookupOrTrackRegister(unsigned ID) {
909 LocIdx &Index = LocIDToLocIdx[ID];
910 if (Index.isIllegal())
911 Index = trackRegister(ID);
912 return Index;
913 }
914
915 /// Is register R currently tracked by MLocTracker?
916 bool isRegisterTracked(Register R) {
917 LocIdx &Index = LocIDToLocIdx[R];
918 return !Index.isIllegal();
919 }
920
921 /// Record a definition of the specified register at the given block / inst.
922 /// This doesn't take a ValueIDNum, because the definition and its location
923 /// are synonymous.
924 void defReg(Register R, unsigned BB, unsigned Inst) {
925 unsigned ID = getLocID(Reg: R);
926 LocIdx Idx = lookupOrTrackRegister(ID);
927 ValueIDNum ValueID = {BB, Inst, Idx};
928 LocIdxToIDNum[Idx] = ValueID;
929 }
930
931 /// Set a register to a value number. To be used if the value number is
932 /// known in advance.
933 void setReg(Register R, ValueIDNum ValueID) {
934 unsigned ID = getLocID(Reg: R);
935 LocIdx Idx = lookupOrTrackRegister(ID);
936 LocIdxToIDNum[Idx] = ValueID;
937 }
938
939 ValueIDNum readReg(Register R) {
940 unsigned ID = getLocID(Reg: R);
941 LocIdx Idx = lookupOrTrackRegister(ID);
942 return LocIdxToIDNum[Idx];
943 }
944
945 /// Reset a register value to zero / empty. Needed to replicate the
946 /// VarLoc implementation where a copy to/from a register effectively
947 /// clears the contents of the source register. (Values can only have one
948 /// machine location in VarLocBasedImpl).
949 void wipeRegister(Register R) {
950 unsigned ID = getLocID(Reg: R);
951 LocIdx Idx = LocIDToLocIdx[ID];
952 LocIdxToIDNum[Idx] = ValueIDNum::EmptyValue;
953 }
954
955 /// Determine the LocIdx of an existing register.
956 LocIdx getRegMLoc(Register R) {
957 unsigned ID = getLocID(Reg: R);
958 assert(ID < LocIDToLocIdx.size());
959 assert(LocIDToLocIdx[ID] != UINT_MAX); // Sentinel for IndexedMap.
960 return LocIDToLocIdx[ID];
961 }
962
963 /// Record a RegMask operand being executed. Defs any register we currently
964 /// track, stores a pointer to the mask in case we have to account for it
965 /// later.
966 void writeRegMask(const MachineOperand *MO, unsigned CurBB, unsigned InstID);
967
968 /// Find LocIdx for SpillLoc \p L, creating a new one if it's not tracked.
969 /// Returns std::nullopt when in scenarios where a spill slot could be
970 /// tracked, but we would likely run into resource limitations.
971 std::optional<SpillLocationNo> getOrTrackSpillLoc(SpillLoc L);
972
973 // Get LocIdx of a spill ID.
974 LocIdx getSpillMLoc(unsigned SpillID) {
975 assert(LocIDToLocIdx[SpillID] != UINT_MAX); // Sentinel for IndexedMap.
976 return LocIDToLocIdx[SpillID];
977 }
978
979 /// Return true if Idx is a spill machine location.
980 bool isSpill(LocIdx Idx) const { return LocIdxToLocID[Idx] >= NumRegs; }
981
982 /// How large is this location (aka, how wide is a value defined there?).
983 unsigned getLocSizeInBits(LocIdx L) const {
984 unsigned ID = LocIdxToLocID[L];
985 if (!isSpill(Idx: L)) {
986 return TRI.getRegSizeInBits(Reg: Register(ID), MRI: MF.getRegInfo());
987 } else {
988 // The slot location on the stack is uninteresting, we care about the
989 // position of the value within the slot (which comes with a size).
990 StackSlotPos Pos = locIDToSpillIdx(ID);
991 return Pos.first;
992 }
993 }
994
995 MLocIterator begin() { return MLocIterator(LocIdxToIDNum, 0); }
996
997 MLocIterator end() {
998 return MLocIterator(LocIdxToIDNum, LocIdxToIDNum.size());
999 }
1000
1001 /// Return a range over all locations currently tracked.
1002 iterator_range<MLocIterator> locations() {
1003 return llvm::make_range(x: begin(), y: end());
1004 }
1005
1006 std::string LocIdxToName(LocIdx Idx) const;
1007
1008 std::string IDAsString(const ValueIDNum &Num) const;
1009
1010#ifndef NDEBUG
1011 LLVM_DUMP_METHOD void dump();
1012
1013 LLVM_DUMP_METHOD void dump_mloc_map();
1014#endif
1015
1016 /// Create a DBG_VALUE based on debug operands \p DbgOps. Qualify it with the
1017 /// information in \pProperties, for variable Var. Don't insert it anywhere,
1018 /// just return the builder for it.
1019 MachineInstrBuilder emitLoc(const SmallVectorImpl<ResolvedDbgOp> &DbgOps,
1020 const DebugVariable &Var, const DILocation *DILoc,
1021 const DbgValueProperties &Properties);
1022};
1023
1024/// Types for recording sets of variable fragments that overlap. For a given
1025/// local variable, we record all other fragments of that variable that could
1026/// overlap it, to reduce search time.
1027using FragmentOfVar =
1028 std::pair<const DILocalVariable *, DIExpression::FragmentInfo>;
1029using OverlapMap =
1030 DenseMap<FragmentOfVar, SmallVector<DIExpression::FragmentInfo, 1>>;
1031
1032/// Collection of DBG_VALUEs observed when traversing a block. Records each
1033/// variable and the value the DBG_VALUE refers to. Requires the machine value
1034/// location dataflow algorithm to have run already, so that values can be
1035/// identified.
1036class VLocTracker {
1037public:
1038 /// Ref to function-wide map of DebugVariable <=> ID-numbers.
1039 DebugVariableMap &DVMap;
1040 /// Map DebugVariable to the latest Value it's defined to have.
1041 /// Needs to be a MapVector because we determine order-in-the-input-MIR from
1042 /// the order in this container. (FIXME: likely no longer true as the ordering
1043 /// is now provided by DebugVariableMap).
1044 /// We only retain the last DbgValue in each block for each variable, to
1045 /// determine the blocks live-out variable value. The Vars container forms the
1046 /// transfer function for this block, as part of the dataflow analysis. The
1047 /// movement of values between locations inside of a block is handled at a
1048 /// much later stage, in the TransferTracker class.
1049 SmallMapVector<DebugVariableID, DbgValue, 8> Vars;
1050 SmallDenseMap<DebugVariableID, const DILocation *, 8> Scopes;
1051 MachineBasicBlock *MBB = nullptr;
1052 const OverlapMap &OverlappingFragments;
1053 DbgValueProperties EmptyProperties;
1054
1055public:
1056 VLocTracker(DebugVariableMap &DVMap, const OverlapMap &O,
1057 const DIExpression *EmptyExpr)
1058 : DVMap(DVMap), OverlappingFragments(O),
1059 EmptyProperties(EmptyExpr, false, false) {}
1060
1061 void defVar(const MachineInstr &MI, const DbgValueProperties &Properties,
1062 const SmallVectorImpl<DbgOpID> &DebugOps) {
1063 assert(MI.isDebugValueLike());
1064 DebugVariable Var(MI.getDebugVariable(), MI.getDebugExpression(),
1065 MI.getDebugLoc()->getInlinedAt());
1066 // Either insert or fetch an ID number for this variable.
1067 DebugVariableID VarID = DVMap.insertDVID(Var, Loc: MI.getDebugLoc().get());
1068 DbgValue Rec = (DebugOps.size() > 0)
1069 ? DbgValue(DebugOps, Properties)
1070 : DbgValue(Properties, DbgValue::Undef);
1071
1072 // Attempt insertion; overwrite if it's already mapped.
1073 Vars.insert_or_assign(Key: VarID, Val&: Rec);
1074 Scopes[VarID] = MI.getDebugLoc().get();
1075
1076 considerOverlaps(Var, Loc: MI.getDebugLoc().get());
1077 }
1078
1079 void considerOverlaps(const DebugVariable &Var, const DILocation *Loc) {
1080 auto Overlaps = OverlappingFragments.find(
1081 Val: {Var.getVariable(), Var.getFragmentOrDefault()});
1082 if (Overlaps == OverlappingFragments.end())
1083 return;
1084
1085 // Otherwise: terminate any overlapped variable locations.
1086 for (auto FragmentInfo : Overlaps->second) {
1087 // The "empty" fragment is stored as DebugVariable::DefaultFragment, so
1088 // that it overlaps with everything, however its cannonical representation
1089 // in a DebugVariable is as "None".
1090 std::optional<DIExpression::FragmentInfo> OptFragmentInfo = FragmentInfo;
1091 if (DebugVariable::isDefaultFragment(F: FragmentInfo))
1092 OptFragmentInfo = std::nullopt;
1093
1094 DebugVariable Overlapped(Var.getVariable(), OptFragmentInfo,
1095 Var.getInlinedAt());
1096 // Produce an ID number for this overlapping fragment of a variable.
1097 DebugVariableID OverlappedID = DVMap.insertDVID(Var&: Overlapped, Loc);
1098 DbgValue Rec = DbgValue(EmptyProperties, DbgValue::Undef);
1099
1100 // Attempt insertion; overwrite if it's already mapped.
1101 Vars.insert_or_assign(Key: OverlappedID, Val&: Rec);
1102 Scopes[OverlappedID] = Loc;
1103 }
1104 }
1105
1106 void clear() {
1107 Vars.clear();
1108 Scopes.clear();
1109 }
1110};
1111
1112// XXX XXX docs
1113class InstrRefBasedLDV : public LDVImpl {
1114public:
1115 friend class ::InstrRefLDVTest;
1116
1117 using FragmentInfo = DIExpression::FragmentInfo;
1118 using OptFragmentInfo = std::optional<DIExpression::FragmentInfo>;
1119
1120 // Helper while building OverlapMap, a map of all fragments seen for a given
1121 // DILocalVariable.
1122 using VarToFragments =
1123 DenseMap<const DILocalVariable *, SmallSet<FragmentInfo, 4>>;
1124
1125 /// Machine location/value transfer function, a mapping of which locations
1126 /// are assigned which new values.
1127 using MLocTransferMap = SmallDenseMap<LocIdx, ValueIDNum>;
1128
1129 /// Live in/out structure for the variable values: a per-block map of
1130 /// variables to their values.
1131 using LiveIdxT = SmallDenseMap<const MachineBasicBlock *, DbgValue *, 16>;
1132
1133 using VarAndLoc = std::pair<DebugVariableID, DbgValue>;
1134
1135 /// Type for a live-in value: the predecessor block, and its value.
1136 using InValueT = std::pair<MachineBasicBlock *, DbgValue *>;
1137
1138 /// Vector (per block) of a collection (inner smallvector) of live-ins.
1139 /// Used as the result type for the variable value dataflow problem.
1140 using LiveInsT = SmallVector<SmallVector<VarAndLoc, 8>, 8>;
1141
1142 /// Mapping from lexical scopes to a DILocation in that scope.
1143 using ScopeToDILocT = DenseMap<const LexicalScope *, const DILocation *>;
1144
1145 /// Mapping from lexical scopes to variables in that scope.
1146 using ScopeToVarsT =
1147 DenseMap<const LexicalScope *, SmallSet<DebugVariableID, 4>>;
1148
1149 /// Mapping from lexical scopes to blocks where variables in that scope are
1150 /// assigned. Such blocks aren't necessarily "in" the lexical scope, it's
1151 /// just a block where an assignment happens.
1152 using ScopeToAssignBlocksT = DenseMap<const LexicalScope *, SmallPtrSet<MachineBasicBlock *, 4>>;
1153
1154private:
1155 MachineDominatorTree *DomTree;
1156 const TargetRegisterInfo *TRI;
1157 const MachineRegisterInfo *MRI;
1158 const TargetInstrInfo *TII;
1159 const TargetFrameLowering *TFI;
1160 const MachineFrameInfo *MFI;
1161 BitVector CalleeSavedRegs;
1162 LexicalScopes LS;
1163
1164 // An empty DIExpression. Used default / placeholder DbgValueProperties
1165 // objects, as we can't have null expressions.
1166 const DIExpression *EmptyExpr;
1167
1168 /// Object to track machine locations as we step through a block. Could
1169 /// probably be a field rather than a pointer, as it's always used.
1170 MLocTracker *MTracker = nullptr;
1171
1172 /// Number of the current block LiveDebugValues is stepping through.
1173 unsigned CurBB = -1;
1174
1175 /// Number of the current instruction LiveDebugValues is evaluating.
1176 unsigned CurInst;
1177
1178 /// Variable tracker -- listens to DBG_VALUEs occurring as InstrRefBasedImpl
1179 /// steps through a block. Reads the values at each location from the
1180 /// MLocTracker object.
1181 VLocTracker *VTracker = nullptr;
1182
1183 /// Tracker for transfers, listens to DBG_VALUEs and transfers of values
1184 /// between locations during stepping, creates new DBG_VALUEs when values move
1185 /// location.
1186 TransferTracker *TTracker = nullptr;
1187
1188 /// Blocks which are artificial, i.e. blocks which exclusively contain
1189 /// instructions without DebugLocs, or with line 0 locations.
1190 SmallPtrSet<MachineBasicBlock *, 16> ArtificialBlocks;
1191
1192 // Mapping of blocks to and from their RPOT order.
1193 SmallVector<MachineBasicBlock *> OrderToBB;
1194 DenseMap<const MachineBasicBlock *, unsigned int> BBToOrder;
1195 DenseMap<unsigned, unsigned> BBNumToRPO;
1196
1197 /// Pair of MachineInstr, and its 1-based offset into the containing block.
1198 using InstAndNum = std::pair<const MachineInstr *, unsigned>;
1199 /// Map from debug instruction number to the MachineInstr labelled with that
1200 /// number, and its location within the function. Used to transform
1201 /// instruction numbers in DBG_INSTR_REFs into machine value numbers.
1202 std::map<uint64_t, InstAndNum> DebugInstrNumToInstr;
1203
1204 /// Record of where we observed a DBG_PHI instruction.
1205 class DebugPHIRecord {
1206 public:
1207 /// Instruction number of this DBG_PHI.
1208 uint64_t InstrNum;
1209 /// Block where DBG_PHI occurred.
1210 MachineBasicBlock *MBB;
1211 /// The value number read by the DBG_PHI -- or std::nullopt if it didn't
1212 /// refer to a value.
1213 std::optional<ValueIDNum> ValueRead;
1214 /// Register/Stack location the DBG_PHI reads -- or std::nullopt if it
1215 /// referred to something unexpected.
1216 std::optional<LocIdx> ReadLoc;
1217
1218 operator unsigned() const { return InstrNum; }
1219 };
1220
1221 /// Map from instruction numbers defined by DBG_PHIs to a record of what that
1222 /// DBG_PHI read and where. Populated and edited during the machine value
1223 /// location problem -- we use LLVMs SSA Updater to fix changes by
1224 /// optimizations that destroy PHI instructions.
1225 SmallVector<DebugPHIRecord, 32> DebugPHINumToValue;
1226
1227 // Map of overlapping variable fragments.
1228 OverlapMap OverlapFragments;
1229 VarToFragments SeenFragments;
1230
1231 /// Mapping of DBG_INSTR_REF instructions to their values, for those
1232 /// DBG_INSTR_REFs that call resolveDbgPHIs. These variable references solve
1233 /// a mini SSA problem caused by DBG_PHIs being cloned, this collection caches
1234 /// the result.
1235 DenseMap<std::pair<MachineInstr *, unsigned>, std::optional<ValueIDNum>>
1236 SeenDbgPHIs;
1237
1238 DbgOpIDMap DbgOpStore;
1239
1240 /// Mapping between DebugVariables and unique ID numbers. This is a more
1241 /// efficient way to represent the identity of a variable, versus a plain
1242 /// DebugVariable.
1243 DebugVariableMap DVMap;
1244
1245 /// True if we need to examine call instructions for stack clobbers. We
1246 /// normally assume that they don't clobber SP, but stack probes on Windows
1247 /// do.
1248 bool AdjustsStackInCalls = false;
1249
1250 /// If AdjustsStackInCalls is true, this holds the name of the target's stack
1251 /// probe function, which is the function we expect will alter the stack
1252 /// pointer.
1253 StringRef StackProbeSymbolName;
1254
1255 /// Tests whether this instruction is a spill to a stack slot.
1256 std::optional<SpillLocationNo> isSpillInstruction(const MachineInstr &MI,
1257 MachineFunction *MF);
1258
1259 /// Decide if @MI is a spill instruction and return true if it is. We use 2
1260 /// criteria to make this decision:
1261 /// - Is this instruction a store to a spill slot?
1262 /// - Is there a register operand that is both used and killed?
1263 /// TODO: Store optimization can fold spills into other stores (including
1264 /// other spills). We do not handle this yet (more than one memory operand).
1265 bool isLocationSpill(const MachineInstr &MI, MachineFunction *MF,
1266 unsigned &Reg);
1267
1268 /// If a given instruction is identified as a spill, return the spill slot
1269 /// and set \p Reg to the spilled register.
1270 std::optional<SpillLocationNo> isRestoreInstruction(const MachineInstr &MI,
1271 MachineFunction *MF,
1272 unsigned &Reg);
1273
1274 /// Given a spill instruction, extract the spill slot information, ensure it's
1275 /// tracked, and return the spill number.
1276 std::optional<SpillLocationNo>
1277 extractSpillBaseRegAndOffset(const MachineInstr &MI);
1278
1279 /// For an instruction reference given by \p InstNo and \p OpNo in instruction
1280 /// \p MI returns the Value pointed to by that instruction reference if any
1281 /// exists, otherwise returns std::nullopt.
1282 std::optional<ValueIDNum> getValueForInstrRef(unsigned InstNo, unsigned OpNo,
1283 MachineInstr &MI,
1284 const FuncValueTable *MLiveOuts,
1285 const FuncValueTable *MLiveIns);
1286
1287 /// Observe a single instruction while stepping through a block.
1288 void process(MachineInstr &MI, const FuncValueTable *MLiveOuts,
1289 const FuncValueTable *MLiveIns);
1290
1291 /// Examines whether \p MI is a DBG_VALUE and notifies trackers.
1292 /// \returns true if MI was recognized and processed.
1293 bool transferDebugValue(const MachineInstr &MI);
1294
1295 /// Examines whether \p MI is a DBG_INSTR_REF and notifies trackers.
1296 /// \returns true if MI was recognized and processed.
1297 bool transferDebugInstrRef(MachineInstr &MI, const FuncValueTable *MLiveOuts,
1298 const FuncValueTable *MLiveIns);
1299
1300 /// Stores value-information about where this PHI occurred, and what
1301 /// instruction number is associated with it.
1302 /// \returns true if MI was recognized and processed.
1303 bool transferDebugPHI(MachineInstr &MI);
1304
1305 /// Examines whether \p MI is copy instruction, and notifies trackers.
1306 /// \returns true if MI was recognized and processed.
1307 bool transferRegisterCopy(MachineInstr &MI);
1308
1309 /// Examines whether \p MI is stack spill or restore instruction, and
1310 /// notifies trackers. \returns true if MI was recognized and processed.
1311 bool transferSpillOrRestoreInst(MachineInstr &MI);
1312
1313 /// Examines \p MI for any registers that it defines, and notifies trackers.
1314 void transferRegisterDef(MachineInstr &MI);
1315
1316 /// Copy one location to the other, accounting for movement of subregisters
1317 /// too.
1318 void performCopy(Register Src, Register Dst);
1319
1320 void accumulateFragmentMap(MachineInstr &MI);
1321
1322 /// Determine the machine value number referred to by (potentially several)
1323 /// DBG_PHI instructions. Block duplication and tail folding can duplicate
1324 /// DBG_PHIs, shifting the position where values in registers merge, and
1325 /// forming another mini-ssa problem to solve.
1326 /// \p Here the position of a DBG_INSTR_REF seeking a machine value number
1327 /// \p InstrNum Debug instruction number defined by DBG_PHI instructions.
1328 /// \returns The machine value number at position Here, or std::nullopt.
1329 std::optional<ValueIDNum> resolveDbgPHIs(MachineFunction &MF,
1330 const FuncValueTable &MLiveOuts,
1331 const FuncValueTable &MLiveIns,
1332 MachineInstr &Here,
1333 uint64_t InstrNum);
1334
1335 std::optional<ValueIDNum> resolveDbgPHIsImpl(MachineFunction &MF,
1336 const FuncValueTable &MLiveOuts,
1337 const FuncValueTable &MLiveIns,
1338 MachineInstr &Here,
1339 uint64_t InstrNum);
1340
1341 /// Step through the function, recording register definitions and movements
1342 /// in an MLocTracker. Convert the observations into a per-block transfer
1343 /// function in \p MLocTransfer, suitable for using with the machine value
1344 /// location dataflow problem.
1345 void
1346 produceMLocTransferFunction(MachineFunction &MF,
1347 SmallVectorImpl<MLocTransferMap> &MLocTransfer,
1348 unsigned MaxNumBlocks);
1349
1350 /// Solve the machine value location dataflow problem. Takes as input the
1351 /// transfer functions in \p MLocTransfer. Writes the output live-in and
1352 /// live-out arrays to the (initialized to zero) multidimensional arrays in
1353 /// \p MInLocs and \p MOutLocs. The outer dimension is indexed by block
1354 /// number, the inner by LocIdx.
1355 void buildMLocValueMap(MachineFunction &MF, FuncValueTable &MInLocs,
1356 FuncValueTable &MOutLocs,
1357 SmallVectorImpl<MLocTransferMap> &MLocTransfer);
1358
1359 /// Examine the stack indexes (i.e. offsets within the stack) to find the
1360 /// basic units of interference -- like reg units, but for the stack.
1361 void findStackIndexInterference(SmallVectorImpl<unsigned> &Slots);
1362
1363 /// Install PHI values into the live-in array for each block, according to
1364 /// the IDF of each register.
1365 void placeMLocPHIs(MachineFunction &MF,
1366 SmallPtrSetImpl<MachineBasicBlock *> &AllBlocks,
1367 FuncValueTable &MInLocs,
1368 SmallVectorImpl<MLocTransferMap> &MLocTransfer);
1369
1370 /// Propagate variable values to blocks in the common case where there's
1371 /// only one value assigned to the variable. This function has better
1372 /// performance as it doesn't have to find the dominance frontier between
1373 /// different assignments.
1374 void placePHIsForSingleVarDefinition(
1375 const SmallPtrSetImpl<MachineBasicBlock *> &InScopeBlocks,
1376 MachineBasicBlock *MBB, SmallVectorImpl<VLocTracker> &AllTheVLocs,
1377 DebugVariableID Var, LiveInsT &Output);
1378
1379 /// Calculate the iterated-dominance-frontier for a set of defs, using the
1380 /// existing LLVM facilities for this. Works for a single "value" or
1381 /// machine/variable location.
1382 /// \p AllBlocks Set of blocks where we might consume the value.
1383 /// \p DefBlocks Set of blocks where the value/location is defined.
1384 /// \p PHIBlocks Output set of blocks where PHIs must be placed.
1385 void BlockPHIPlacement(const SmallPtrSetImpl<MachineBasicBlock *> &AllBlocks,
1386 const SmallPtrSetImpl<MachineBasicBlock *> &DefBlocks,
1387 SmallVectorImpl<MachineBasicBlock *> &PHIBlocks);
1388
1389 /// Perform a control flow join (lattice value meet) of the values in machine
1390 /// locations at \p MBB. Follows the algorithm described in the file-comment,
1391 /// reading live-outs of predecessors from \p OutLocs, the current live ins
1392 /// from \p InLocs, and assigning the newly computed live ins back into
1393 /// \p InLocs. \returns two bools -- the first indicates whether a change
1394 /// was made, the second whether a lattice downgrade occurred. If the latter
1395 /// is true, revisiting this block is necessary.
1396 bool mlocJoin(MachineBasicBlock &MBB,
1397 SmallPtrSet<const MachineBasicBlock *, 16> &Visited,
1398 FuncValueTable &OutLocs, ValueTable &InLocs);
1399
1400 /// Produce a set of blocks that are in the current lexical scope. This means
1401 /// those blocks that contain instructions "in" the scope, blocks where
1402 /// assignments to variables in scope occur, and artificial blocks that are
1403 /// successors to any of the earlier blocks. See https://llvm.org/PR48091 for
1404 /// more commentry on what "in scope" means.
1405 /// \p DILoc A location in the scope that we're fetching blocks for.
1406 /// \p Output Set to put in-scope-blocks into.
1407 /// \p AssignBlocks Blocks known to contain assignments of variables in scope.
1408 void
1409 getBlocksForScope(const DILocation *DILoc,
1410 SmallPtrSetImpl<const MachineBasicBlock *> &Output,
1411 const SmallPtrSetImpl<MachineBasicBlock *> &AssignBlocks);
1412
1413 /// Solve the variable value dataflow problem, for a single lexical scope.
1414 /// Uses the algorithm from the file comment to resolve control flow joins
1415 /// using PHI placement and value propagation. Reads the locations of machine
1416 /// values from the \p MInLocs and \p MOutLocs arrays (see buildMLocValueMap)
1417 /// and reads the variable values transfer function from \p AllTheVlocs.
1418 /// Live-in and Live-out variable values are stored locally, with the live-ins
1419 /// permanently stored to \p Output once a fixedpoint is reached.
1420 /// \p VarsWeCareAbout contains a collection of the variables in \p Scope
1421 /// that we should be tracking.
1422 /// \p AssignBlocks contains the set of blocks that aren't in \p DILoc's
1423 /// scope, but which do contain DBG_VALUEs, which VarLocBasedImpl tracks
1424 /// locations through.
1425 void buildVLocValueMap(const DILocation *DILoc,
1426 const SmallSet<DebugVariableID, 4> &VarsWeCareAbout,
1427 SmallPtrSetImpl<MachineBasicBlock *> &AssignBlocks,
1428 LiveInsT &Output, FuncValueTable &MOutLocs,
1429 FuncValueTable &MInLocs,
1430 SmallVectorImpl<VLocTracker> &AllTheVLocs);
1431
1432 /// Attempt to eliminate un-necessary PHIs on entry to a block. Examines the
1433 /// live-in values coming from predecessors live-outs, and replaces any PHIs
1434 /// already present in this blocks live-ins with a live-through value if the
1435 /// PHI isn't needed.
1436 /// \p LiveIn Old live-in value, overwritten with new one if live-in changes.
1437 /// \returns true if any live-ins change value, either from value propagation
1438 /// or PHI elimination.
1439 bool vlocJoin(MachineBasicBlock &MBB, LiveIdxT &VLOCOutLocs,
1440 SmallPtrSet<const MachineBasicBlock *, 8> &BlocksToExplore,
1441 DbgValue &LiveIn);
1442
1443 /// For the given block and live-outs feeding into it, try to find
1444 /// machine locations for each debug operand where all the values feeding
1445 /// into that operand join together.
1446 /// \returns true if a joined location was found for every value that needed
1447 /// to be joined.
1448 bool
1449 pickVPHILoc(SmallVectorImpl<DbgOpID> &OutValues, const MachineBasicBlock &MBB,
1450 const LiveIdxT &LiveOuts, FuncValueTable &MOutLocs,
1451 const SmallVectorImpl<const MachineBasicBlock *> &BlockOrders);
1452
1453 std::optional<ValueIDNum> pickOperandPHILoc(
1454 unsigned DbgOpIdx, const MachineBasicBlock &MBB, const LiveIdxT &LiveOuts,
1455 FuncValueTable &MOutLocs,
1456 const SmallVectorImpl<const MachineBasicBlock *> &BlockOrders);
1457
1458 /// Take collections of DBG_VALUE instructions stored in TTracker, and
1459 /// install them into their output blocks.
1460 bool emitTransfers();
1461
1462 /// Boilerplate computation of some initial sets, artifical blocks and
1463 /// RPOT block ordering.
1464 void initialSetup(MachineFunction &MF);
1465
1466 /// Produce a map of the last lexical scope that uses a block, using the
1467 /// scopes DFSOut number. Mapping is block-number to DFSOut.
1468 /// \p EjectionMap Pre-allocated vector in which to install the built ma.
1469 /// \p ScopeToDILocation Mapping of LexicalScopes to their DILocations.
1470 /// \p AssignBlocks Map of blocks where assignments happen for a scope.
1471 void makeDepthFirstEjectionMap(SmallVectorImpl<unsigned> &EjectionMap,
1472 const ScopeToDILocT &ScopeToDILocation,
1473 ScopeToAssignBlocksT &AssignBlocks);
1474
1475 /// When determining per-block variable values and emitting to DBG_VALUEs,
1476 /// this function explores by lexical scope depth. Doing so means that per
1477 /// block information can be fully computed before exploration finishes,
1478 /// allowing us to emit it and free data structures earlier than otherwise.
1479 /// It's also good for locality.
1480 bool depthFirstVLocAndEmit(
1481 unsigned MaxNumBlocks, const ScopeToDILocT &ScopeToDILocation,
1482 const ScopeToVarsT &ScopeToVars, ScopeToAssignBlocksT &ScopeToBlocks,
1483 LiveInsT &Output, FuncValueTable &MOutLocs, FuncValueTable &MInLocs,
1484 SmallVectorImpl<VLocTracker> &AllTheVLocs, MachineFunction &MF,
1485 bool ShouldEmitDebugEntryValues);
1486
1487 bool ExtendRanges(MachineFunction &MF, MachineDominatorTree *DomTree,
1488 bool ShouldEmitDebugEntryValues, unsigned InputBBLimit,
1489 unsigned InputDbgValLimit) override;
1490
1491public:
1492 /// Default construct and initialize the pass.
1493 InstrRefBasedLDV();
1494
1495 LLVM_DUMP_METHOD
1496 void dump_mloc_transfer(const MLocTransferMap &mloc_transfer) const;
1497
1498 bool isCalleeSaved(LocIdx L) const;
1499 bool isCalleeSavedReg(Register R) const;
1500
1501 bool hasFoldedStackStore(const MachineInstr &MI) {
1502 // Instruction must have a memory operand that's a stack slot, and isn't
1503 // aliased, meaning it's a spill from regalloc instead of a variable.
1504 // If it's aliased, we can't guarantee its value.
1505 if (!MI.hasOneMemOperand())
1506 return false;
1507 auto *MemOperand = *MI.memoperands_begin();
1508 return MemOperand->isStore() &&
1509 MemOperand->getPseudoValue() &&
1510 MemOperand->getPseudoValue()->kind() == PseudoSourceValue::FixedStack
1511 && !MemOperand->getPseudoValue()->isAliased(MFI);
1512 }
1513
1514 std::optional<LocIdx> findLocationForMemOperand(const MachineInstr &MI);
1515
1516 // Utility for unit testing, don't use directly.
1517 DebugVariableMap &getDVMap() {
1518 return DVMap;
1519 }
1520};
1521
1522} // namespace LiveDebugValues
1523
1524#endif /* LLVM_LIB_CODEGEN_LIVEDEBUGVALUES_INSTRREFBASEDLDV_H */
1525