1//===- VarLocBasedImpl.cpp - Tracking Debug Value MIs with VarLoc class----===//
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/// \file VarLocBasedImpl.cpp
10///
11/// LiveDebugValues is an optimistic "available expressions" dataflow
12/// algorithm. The set of expressions is the set of machine locations
13/// (registers, spill slots, constants, and target indices) that a variable
14/// fragment might be located, qualified by a DIExpression and indirect-ness
15/// flag, while each variable is identified by a DebugVariable object. The
16/// availability of an expression begins when a DBG_VALUE instruction specifies
17/// the location of a DebugVariable, and continues until that location is
18/// clobbered or re-specified by a different DBG_VALUE for the same
19/// DebugVariable.
20///
21/// The output of LiveDebugValues is additional DBG_VALUE instructions,
22/// placed to extend variable locations as far they're available. This file
23/// and the VarLocBasedLDV class is an implementation that explicitly tracks
24/// locations, using the VarLoc class.
25///
26/// The canonical "available expressions" problem doesn't have expression
27/// clobbering, instead when a variable is re-assigned, any expressions using
28/// that variable get invalidated. LiveDebugValues can map onto "available
29/// expressions" by having every register represented by a variable, which is
30/// used in an expression that becomes available at a DBG_VALUE instruction.
31/// When the register is clobbered, its variable is effectively reassigned, and
32/// expressions computed from it become unavailable. A similar construct is
33/// needed when a DebugVariable has its location re-specified, to invalidate
34/// all other locations for that DebugVariable.
35///
36/// Using the dataflow analysis to compute the available expressions, we create
37/// a DBG_VALUE at the beginning of each block where the expression is
38/// live-in. This propagates variable locations into every basic block where
39/// the location can be determined, rather than only having DBG_VALUEs in blocks
40/// where locations are specified due to an assignment or some optimization.
41/// Movements of values between registers and spill slots are annotated with
42/// DBG_VALUEs too to track variable values bewteen locations. All this allows
43/// DbgEntityHistoryCalculator to focus on only the locations within individual
44/// blocks, facilitating testing and improving modularity.
45///
46/// We follow an optimisic dataflow approach, with this lattice:
47///
48/// \verbatim
49/// ┬ "Unknown"
50/// |
51/// v
52/// True
53/// |
54/// v
55/// ⊥ False
56/// \endverbatim With "True" signifying that the expression is available (and
57/// thus a DebugVariable's location is the corresponding register), while
58/// "False" signifies that the expression is unavailable. "Unknown"s never
59/// survive to the end of the analysis (see below).
60///
61/// Formally, all DebugVariable locations that are live-out of a block are
62/// initialized to \top. A blocks live-in values take the meet of the lattice
63/// value for every predecessors live-outs, except for the entry block, where
64/// all live-ins are \bot. The usual dataflow propagation occurs: the transfer
65/// function for a block assigns an expression for a DebugVariable to be "True"
66/// if a DBG_VALUE in the block specifies it; "False" if the location is
67/// clobbered; or the live-in value if it is unaffected by the block. We
68/// visit each block in reverse post order until a fixedpoint is reached. The
69/// solution produced is maximal.
70///
71/// Intuitively, we start by assuming that every expression / variable location
72/// is at least "True", and then propagate "False" from the entry block and any
73/// clobbers until there are no more changes to make. This gives us an accurate
74/// solution because all incorrect locations will have a "False" propagated into
75/// them. It also gives us a solution that copes well with loops by assuming
76/// that variable locations are live-through every loop, and then removing those
77/// that are not through dataflow.
78///
79/// Within LiveDebugValues: each variable location is represented by a
80/// VarLoc object that identifies the source variable, the set of
81/// machine-locations that currently describe it (a single location for
82/// DBG_VALUE or multiple for DBG_VALUE_LIST), and the DBG_VALUE inst that
83/// specifies the location. Each VarLoc is indexed in the (function-scope) \p
84/// VarLocMap, giving each VarLoc a set of unique indexes, each of which
85/// corresponds to one of the VarLoc's machine-locations and can be used to
86/// lookup the VarLoc in the VarLocMap. Rather than operate directly on machine
87/// locations, the dataflow analysis in this pass identifies locations by their
88/// indices in the VarLocMap, meaning all the variable locations in a block can
89/// be described by a sparse vector of VarLocMap indices.
90///
91/// All the storage for the dataflow analysis is local to the ExtendRanges
92/// method and passed down to helper methods. "OutLocs" and "InLocs" record the
93/// in and out lattice values for each block. "OpenRanges" maintains a list of
94/// variable locations and, with the "process" method, evaluates the transfer
95/// function of each block. "flushPendingLocs" installs debug value instructions
96/// for each live-in location at the start of blocks, while "Transfers" records
97/// transfers of values between machine-locations.
98///
99/// We avoid explicitly representing the "Unknown" (\top) lattice value in the
100/// implementation. Instead, unvisited blocks implicitly have all lattice
101/// values set as "Unknown". After being visited, there will be path back to
102/// the entry block where the lattice value is "False", and as the transfer
103/// function cannot make new "Unknown" locations, there are no scenarios where
104/// a block can have an "Unknown" location after being visited. Similarly, we
105/// don't enumerate all possible variable locations before exploring the
106/// function: when a new location is discovered, all blocks previously explored
107/// were implicitly "False" but unrecorded, and become explicitly "False" when
108/// a new VarLoc is created with its bit not set in predecessor InLocs or
109/// OutLocs.
110///
111//===----------------------------------------------------------------------===//
112
113#include "LiveDebugValues.h"
114
115#include "llvm/ADT/CoalescingBitVector.h"
116#include "llvm/ADT/DenseMap.h"
117#include "llvm/ADT/PostOrderIterator.h"
118#include "llvm/ADT/SmallPtrSet.h"
119#include "llvm/ADT/SmallSet.h"
120#include "llvm/ADT/SmallVector.h"
121#include "llvm/ADT/Statistic.h"
122#include "llvm/BinaryFormat/Dwarf.h"
123#include "llvm/CodeGen/LexicalScopes.h"
124#include "llvm/CodeGen/MachineBasicBlock.h"
125#include "llvm/CodeGen/MachineFunction.h"
126#include "llvm/CodeGen/MachineInstr.h"
127#include "llvm/CodeGen/MachineInstrBuilder.h"
128#include "llvm/CodeGen/MachineInstrBundle.h"
129#include "llvm/CodeGen/MachineMemOperand.h"
130#include "llvm/CodeGen/MachineOperand.h"
131#include "llvm/CodeGen/PseudoSourceValue.h"
132#include "llvm/CodeGen/TargetFrameLowering.h"
133#include "llvm/CodeGen/TargetInstrInfo.h"
134#include "llvm/CodeGen/TargetLowering.h"
135#include "llvm/CodeGen/TargetRegisterInfo.h"
136#include "llvm/CodeGen/TargetSubtargetInfo.h"
137#include "llvm/Config/llvm-config.h"
138#include "llvm/IR/DebugInfoMetadata.h"
139#include "llvm/IR/DebugLoc.h"
140#include "llvm/IR/Function.h"
141#include "llvm/MC/MCRegisterInfo.h"
142#include "llvm/Support/Casting.h"
143#include "llvm/Support/Debug.h"
144#include "llvm/Support/TypeSize.h"
145#include "llvm/Support/raw_ostream.h"
146#include "llvm/Target/TargetMachine.h"
147#include <cassert>
148#include <cstdint>
149#include <functional>
150#include <map>
151#include <optional>
152#include <queue>
153#include <tuple>
154#include <utility>
155#include <vector>
156
157using namespace llvm;
158
159#define DEBUG_TYPE "livedebugvalues"
160
161STATISTIC(NumInserted, "Number of DBG_VALUE instructions inserted");
162
163/// If \p Op is a stack or frame register return true, otherwise return false.
164/// This is used to avoid basing the debug entry values on the registers, since
165/// we do not support it at the moment.
166static bool isRegOtherThanSPAndFP(const MachineOperand &Op,
167 const MachineInstr &MI,
168 const TargetRegisterInfo *TRI) {
169 if (!Op.isReg())
170 return false;
171
172 const MachineFunction *MF = MI.getParent()->getParent();
173 const TargetLowering *TLI = MF->getSubtarget().getTargetLowering();
174 Register SP = TLI->getStackPointerRegisterToSaveRestore();
175 Register FP = TRI->getFrameRegister(MF: *MF);
176 Register Reg = Op.getReg();
177
178 return Reg && Reg != SP && Reg != FP;
179}
180
181namespace {
182
183// Max out the number of statically allocated elements in DefinedRegsSet, as
184// this prevents fallback to std::set::count() operations.
185using DefinedRegsSet = SmallSet<Register, 32>;
186
187// The IDs in this set correspond to MachineLocs in VarLocs, as well as VarLocs
188// that represent Entry Values; every VarLoc in the set will also appear
189// exactly once at Location=0.
190// As a result, each VarLoc may appear more than once in this "set", but each
191// range corresponding to a Reg, SpillLoc, or EntryValue type will still be a
192// "true" set (i.e. each VarLoc may appear only once), and the range Location=0
193// is the set of all VarLocs.
194using VarLocSet = CoalescingBitVector<uint64_t>;
195
196/// A type-checked pair of {Register Location (or 0), Index}, used to index
197/// into a \ref VarLocMap. This can be efficiently converted to a 64-bit int
198/// for insertion into a \ref VarLocSet, and efficiently converted back. The
199/// type-checker helps ensure that the conversions aren't lossy.
200///
201/// Why encode a location /into/ the VarLocMap index? This makes it possible
202/// to find the open VarLocs killed by a register def very quickly. This is a
203/// performance-critical operation for LiveDebugValues.
204struct LocIndex {
205 using u32_location_t = uint32_t;
206 using u32_index_t = uint32_t;
207
208 u32_location_t Location; // Physical registers live in the range [1;2^30) (see
209 // \ref MCRegister), so we have plenty of range left
210 // here to encode non-register locations.
211 u32_index_t Index;
212
213 /// The location that has an entry for every VarLoc in the map.
214 static constexpr u32_location_t kUniversalLocation = 0;
215
216 /// The first location that is reserved for VarLocs with locations of kind
217 /// RegisterKind.
218 static constexpr u32_location_t kFirstRegLocation = 1;
219
220 /// The first location greater than 0 that is not reserved for VarLocs with
221 /// locations of kind RegisterKind.
222 static constexpr u32_location_t kFirstInvalidRegLocation = 1 << 30;
223
224 /// A special location reserved for VarLocs with locations of kind
225 /// SpillLocKind.
226 static constexpr u32_location_t kSpillLocation = kFirstInvalidRegLocation;
227
228 /// A special location reserved for VarLocs of kind EntryValueBackupKind and
229 /// EntryValueCopyBackupKind.
230 static constexpr u32_location_t kEntryValueBackupLocation =
231 kFirstInvalidRegLocation + 1;
232
233 /// A special location reserved for VarLocs with locations of kind
234 /// WasmLocKind.
235 /// TODO Placing all Wasm target index locations in this single kWasmLocation
236 /// may cause slowdown in compilation time in very large functions. Consider
237 /// giving a each target index/offset pair its own u32_location_t if this
238 /// becomes a problem.
239 static constexpr u32_location_t kWasmLocation = kFirstInvalidRegLocation + 2;
240
241 /// The first location that is reserved for VarLocs with locations of kind
242 /// VirtualRegisterKind.
243 static constexpr u32_location_t kFirstVirtualRegLocation = 1 << 31;
244
245 LocIndex(u32_location_t Location, u32_index_t Index)
246 : Location(Location), Index(Index) {}
247
248 uint64_t getAsRawInteger() const {
249 return (static_cast<uint64_t>(Location) << 32) | Index;
250 }
251
252 template<typename IntT> static LocIndex fromRawInteger(IntT ID) {
253 static_assert(std::is_unsigned_v<IntT> && sizeof(ID) == sizeof(uint64_t),
254 "Cannot convert raw integer to LocIndex");
255 return {static_cast<u32_location_t>(ID >> 32),
256 static_cast<u32_index_t>(ID)};
257 }
258
259 /// Get the start of the interval reserved for VarLocs of kind RegisterKind
260 /// which reside in \p Reg. The end is at rawIndexForReg(Reg+1)-1.
261 static uint64_t rawIndexForReg(Register Reg) {
262 return LocIndex(Reg, 0).getAsRawInteger();
263 }
264
265 /// Return a range covering all set indices in the interval reserved for
266 /// \p Location in \p Set.
267 static auto indexRangeForLocation(const VarLocSet &Set,
268 u32_location_t Location) {
269 uint64_t Start = LocIndex(Location, 0).getAsRawInteger();
270 uint64_t End = LocIndex(Location + 1, 0).getAsRawInteger();
271 return Set.half_open_range(Start, End);
272 }
273};
274
275// Simple Set for storing all the VarLoc Indices at a Location bucket.
276using VarLocsInRange = SmallSet<LocIndex::u32_index_t, 32>;
277// Vector of all `LocIndex`s for a given VarLoc; the same Location should not
278// appear in any two of these, as each VarLoc appears at most once in any
279// Location bucket.
280using LocIndices = SmallVector<LocIndex, 2>;
281
282class VarLocBasedLDV : public LDVImpl {
283private:
284 const TargetRegisterInfo *TRI;
285 const TargetInstrInfo *TII;
286 const TargetFrameLowering *TFI;
287 bool ShouldEmitDebugEntryValues;
288 BitVector CalleeSavedRegs;
289 LexicalScopes LS;
290 VarLocSet::Allocator Alloc;
291
292 const MachineInstr *LastNonDbgMI;
293
294 enum struct TransferKind { TransferCopy, TransferSpill, TransferRestore };
295
296 using FragmentInfo = DIExpression::FragmentInfo;
297 using OptFragmentInfo = std::optional<DIExpression::FragmentInfo>;
298
299 /// A pair of debug variable and value location.
300 struct VarLoc {
301 // The location at which a spilled variable resides. It consists of a
302 // register and an offset.
303 struct SpillLoc {
304 unsigned SpillBase;
305 StackOffset SpillOffset;
306 bool operator==(const SpillLoc &Other) const {
307 return SpillBase == Other.SpillBase && SpillOffset == Other.SpillOffset;
308 }
309 bool operator!=(const SpillLoc &Other) const {
310 return !(*this == Other);
311 }
312 };
313
314 // Target indices used for wasm-specific locations.
315 struct WasmLoc {
316 // One of TargetIndex values defined in WebAssembly.h. We deal with
317 // local-related TargetIndex in this analysis (TI_LOCAL and
318 // TI_LOCAL_INDIRECT). Stack operands (TI_OPERAND_STACK) will be handled
319 // separately WebAssemblyDebugFixup pass, and we don't associate debug
320 // info with values in global operands (TI_GLOBAL_RELOC) at the moment.
321 int Index;
322 int64_t Offset;
323 bool operator==(const WasmLoc &Other) const {
324 return Index == Other.Index && Offset == Other.Offset;
325 }
326 bool operator!=(const WasmLoc &Other) const { return !(*this == Other); }
327 };
328
329 /// Identity of the variable at this location.
330 const DebugVariable Var;
331
332 /// The expression applied to this location.
333 const DIExpression *Expr;
334
335 /// DBG_VALUE to clone var/expr information from if this location
336 /// is moved.
337 const MachineInstr &MI;
338
339 enum class MachineLocKind {
340 InvalidKind = 0,
341 RegisterKind,
342 SpillLocKind,
343 ImmediateKind,
344 WasmLocKind
345 };
346
347 enum class EntryValueLocKind {
348 NonEntryValueKind = 0,
349 EntryValueKind,
350 EntryValueBackupKind,
351 EntryValueCopyBackupKind
352 } EVKind = EntryValueLocKind::NonEntryValueKind;
353
354 /// The value location. Stored separately to avoid repeatedly
355 /// extracting it from MI.
356 union MachineLocValue {
357 uint64_t RegNo;
358 SpillLoc SpillLocation;
359 uint64_t Hash;
360 int64_t Immediate;
361 const ConstantFP *FPImm;
362 const ConstantInt *CImm;
363 WasmLoc WasmLocation;
364 MachineLocValue() : Hash(0) {}
365 };
366
367 /// A single machine location; its Kind is either a register, spill
368 /// location, or immediate value.
369 /// If the VarLoc is not a NonEntryValueKind, then it will use only a
370 /// single MachineLoc of RegisterKind.
371 struct MachineLoc {
372 MachineLocKind Kind;
373 MachineLocValue Value;
374 bool operator==(const MachineLoc &Other) const {
375 if (Kind != Other.Kind)
376 return false;
377 switch (Kind) {
378 case MachineLocKind::SpillLocKind:
379 return Value.SpillLocation == Other.Value.SpillLocation;
380 case MachineLocKind::WasmLocKind:
381 return Value.WasmLocation == Other.Value.WasmLocation;
382 case MachineLocKind::RegisterKind:
383 case MachineLocKind::ImmediateKind:
384 return Value.Hash == Other.Value.Hash;
385 default:
386 llvm_unreachable("Invalid kind");
387 }
388 }
389 bool operator<(const MachineLoc &Other) const {
390 switch (Kind) {
391 case MachineLocKind::SpillLocKind:
392 return std::make_tuple(
393 args: Kind, args: Value.SpillLocation.SpillBase,
394 args: Value.SpillLocation.SpillOffset.getFixed(),
395 args: Value.SpillLocation.SpillOffset.getScalable()) <
396 std::make_tuple(
397 args: Other.Kind, args: Other.Value.SpillLocation.SpillBase,
398 args: Other.Value.SpillLocation.SpillOffset.getFixed(),
399 args: Other.Value.SpillLocation.SpillOffset.getScalable());
400 case MachineLocKind::WasmLocKind:
401 return std::make_tuple(args: Kind, args: Value.WasmLocation.Index,
402 args: Value.WasmLocation.Offset) <
403 std::make_tuple(args: Other.Kind, args: Other.Value.WasmLocation.Index,
404 args: Other.Value.WasmLocation.Offset);
405 case MachineLocKind::RegisterKind:
406 case MachineLocKind::ImmediateKind:
407 return std::tie(args: Kind, args: Value.Hash) <
408 std::tie(args: Other.Kind, args: Other.Value.Hash);
409 default:
410 llvm_unreachable("Invalid kind");
411 }
412 }
413 };
414
415 /// The set of machine locations used to determine the variable's value, in
416 /// conjunction with Expr. Initially populated with MI's debug operands,
417 /// but may be transformed independently afterwards.
418 SmallVector<MachineLoc, 8> Locs;
419 /// Used to map the index of each location in Locs back to the index of its
420 /// original debug operand in MI. Used when multiple location operands are
421 /// coalesced and the original MI's operands need to be accessed while
422 /// emitting a debug value.
423 SmallVector<unsigned, 8> OrigLocMap;
424
425 VarLoc(const MachineInstr &MI)
426 : Var(MI.getDebugVariable(), MI.getDebugExpression(),
427 MI.getDebugLoc()->getInlinedAt()),
428 Expr(MI.getDebugExpression()), MI(MI) {
429 assert(MI.isDebugValue() && "not a DBG_VALUE");
430 assert((MI.isDebugValueList() || MI.getNumOperands() == 4) &&
431 "malformed DBG_VALUE");
432 for (const MachineOperand &Op : MI.debug_operands()) {
433 MachineLoc ML = GetLocForOp(Op);
434 auto It = find(Range&: Locs, Val: ML);
435 if (It == Locs.end()) {
436 Locs.push_back(Elt: ML);
437 OrigLocMap.push_back(Elt: MI.getDebugOperandIndex(Op: &Op));
438 } else {
439 // ML duplicates an element in Locs; replace references to Op
440 // with references to the duplicating element.
441 unsigned OpIdx = Locs.size();
442 unsigned DuplicatingIdx = std::distance(first: Locs.begin(), last: It);
443 Expr = DIExpression::replaceArg(Expr, OldArg: OpIdx, NewArg: DuplicatingIdx);
444 }
445 }
446
447 // We create the debug entry values from the factory functions rather
448 // than from this ctor.
449 assert(EVKind != EntryValueLocKind::EntryValueKind &&
450 !isEntryBackupLoc());
451 }
452
453 static MachineLoc GetLocForOp(const MachineOperand &Op) {
454 MachineLocKind Kind;
455 MachineLocValue Loc;
456 if (Op.isReg()) {
457 Kind = MachineLocKind::RegisterKind;
458 Loc.RegNo = Op.getReg();
459 } else if (Op.isImm()) {
460 Kind = MachineLocKind::ImmediateKind;
461 Loc.Immediate = Op.getImm();
462 } else if (Op.isFPImm()) {
463 Kind = MachineLocKind::ImmediateKind;
464 Loc.FPImm = Op.getFPImm();
465 } else if (Op.isCImm()) {
466 Kind = MachineLocKind::ImmediateKind;
467 Loc.CImm = Op.getCImm();
468 } else if (Op.isTargetIndex()) {
469 Kind = MachineLocKind::WasmLocKind;
470 Loc.WasmLocation = {.Index: Op.getIndex(), .Offset: Op.getOffset()};
471 } else
472 llvm_unreachable("Invalid Op kind for MachineLoc.");
473 return {.Kind: Kind, .Value: Loc};
474 }
475
476 /// Take the variable and machine-location in DBG_VALUE MI, and build an
477 /// entry location using the given expression.
478 static VarLoc CreateEntryLoc(const MachineInstr &MI,
479 const DIExpression *EntryExpr, Register Reg) {
480 VarLoc VL(MI);
481 assert(VL.Locs.size() == 1 &&
482 VL.Locs[0].Kind == MachineLocKind::RegisterKind);
483 VL.EVKind = EntryValueLocKind::EntryValueKind;
484 VL.Expr = EntryExpr;
485 VL.Locs[0].Value.RegNo = Reg;
486 return VL;
487 }
488
489 /// Take the variable and machine-location from the DBG_VALUE (from the
490 /// function entry), and build an entry value backup location. The backup
491 /// location will turn into the normal location if the backup is valid at
492 /// the time of the primary location clobbering.
493 static VarLoc CreateEntryBackupLoc(const MachineInstr &MI,
494 const DIExpression *EntryExpr) {
495 VarLoc VL(MI);
496 assert(VL.Locs.size() == 1 &&
497 VL.Locs[0].Kind == MachineLocKind::RegisterKind);
498 VL.EVKind = EntryValueLocKind::EntryValueBackupKind;
499 VL.Expr = EntryExpr;
500 return VL;
501 }
502
503 /// Take the variable and machine-location from the DBG_VALUE (from the
504 /// function entry), and build a copy of an entry value backup location by
505 /// setting the register location to NewReg.
506 static VarLoc CreateEntryCopyBackupLoc(const MachineInstr &MI,
507 const DIExpression *EntryExpr,
508 Register NewReg) {
509 VarLoc VL(MI);
510 assert(VL.Locs.size() == 1 &&
511 VL.Locs[0].Kind == MachineLocKind::RegisterKind);
512 VL.EVKind = EntryValueLocKind::EntryValueCopyBackupKind;
513 VL.Expr = EntryExpr;
514 VL.Locs[0].Value.RegNo = NewReg;
515 return VL;
516 }
517
518 /// Copy the register location in DBG_VALUE MI, updating the register to
519 /// be NewReg.
520 static VarLoc CreateCopyLoc(const VarLoc &OldVL, const MachineLoc &OldML,
521 Register NewReg) {
522 VarLoc VL = OldVL;
523 for (MachineLoc &ML : VL.Locs)
524 if (ML == OldML) {
525 ML.Kind = MachineLocKind::RegisterKind;
526 ML.Value.RegNo = NewReg;
527 return VL;
528 }
529 llvm_unreachable("Should have found OldML in new VarLoc.");
530 }
531
532 /// Take the variable described by DBG_VALUE* MI, and create a VarLoc
533 /// locating it in the specified spill location.
534 static VarLoc CreateSpillLoc(const VarLoc &OldVL, const MachineLoc &OldML,
535 unsigned SpillBase, StackOffset SpillOffset) {
536 VarLoc VL = OldVL;
537 for (MachineLoc &ML : VL.Locs)
538 if (ML == OldML) {
539 ML.Kind = MachineLocKind::SpillLocKind;
540 ML.Value.SpillLocation = {.SpillBase: SpillBase, .SpillOffset: SpillOffset};
541 return VL;
542 }
543 llvm_unreachable("Should have found OldML in new VarLoc.");
544 }
545
546 /// Create a DBG_VALUE representing this VarLoc in the given function.
547 /// Copies variable-specific information such as DILocalVariable and
548 /// inlining information from the original DBG_VALUE instruction, which may
549 /// have been several transfers ago.
550 MachineInstr *BuildDbgValue(MachineFunction &MF) const {
551 assert(!isEntryBackupLoc() &&
552 "Tried to produce DBG_VALUE for backup VarLoc");
553 const DebugLoc &DbgLoc = MI.getDebugLoc();
554 bool Indirect = MI.isIndirectDebugValue();
555 const auto &IID = MI.getDesc();
556 const DILocalVariable *Var = MI.getDebugVariable();
557 NumInserted++;
558
559 const DIExpression *DIExpr = Expr;
560 SmallVector<MachineOperand, 8> MOs;
561 for (unsigned I = 0, E = Locs.size(); I < E; ++I) {
562 MachineLocKind LocKind = Locs[I].Kind;
563 MachineLocValue Loc = Locs[I].Value;
564 const MachineOperand &Orig = MI.getDebugOperand(Index: OrigLocMap[I]);
565 switch (LocKind) {
566 case MachineLocKind::RegisterKind:
567 // An entry value is a register location -- but with an updated
568 // expression. The register location of such DBG_VALUE is always the
569 // one from the entry DBG_VALUE, it does not matter if the entry value
570 // was copied in to another register due to some optimizations.
571 // Non-entry value register locations are like the source
572 // DBG_VALUE, but with the register number from this VarLoc.
573 MOs.push_back(Elt: MachineOperand::CreateReg(
574 Reg: EVKind == EntryValueLocKind::EntryValueKind ? Orig.getReg()
575 : Register(Loc.RegNo),
576 isDef: false));
577 break;
578 case MachineLocKind::SpillLocKind: {
579 // Spills are indirect DBG_VALUEs, with a base register and offset.
580 // Use the original DBG_VALUEs expression to build the spilt location
581 // on top of. FIXME: spill locations created before this pass runs
582 // are not recognized, and not handled here.
583 unsigned Base = Loc.SpillLocation.SpillBase;
584 auto *TRI = MF.getSubtarget().getRegisterInfo();
585 if (MI.isNonListDebugValue()) {
586 auto Deref = Indirect ? DIExpression::DerefAfter : 0;
587 DIExpr = TRI->prependOffsetExpression(
588 Expr: DIExpr, PrependFlags: DIExpression::ApplyOffset | Deref,
589 Offset: Loc.SpillLocation.SpillOffset);
590 Indirect = true;
591 } else {
592 SmallVector<uint64_t, 4> Ops;
593 TRI->getOffsetOpcodes(Offset: Loc.SpillLocation.SpillOffset, Ops);
594 Ops.push_back(Elt: dwarf::DW_OP_deref);
595 DIExpr = DIExpression::appendOpsToArg(Expr: DIExpr, Ops, ArgNo: I);
596 }
597 MOs.push_back(Elt: MachineOperand::CreateReg(Reg: Base, isDef: false));
598 break;
599 }
600 case MachineLocKind::ImmediateKind: {
601 MOs.push_back(Elt: Orig);
602 break;
603 }
604 case MachineLocKind::WasmLocKind: {
605 MOs.push_back(Elt: Orig);
606 break;
607 }
608 case MachineLocKind::InvalidKind:
609 llvm_unreachable("Tried to produce DBG_VALUE for invalid VarLoc");
610 }
611 }
612 return BuildMI(MF, DL: DbgLoc, MCID: IID, IsIndirect: Indirect, MOs, Variable: Var, Expr: DIExpr);
613 }
614
615 /// Is the Loc field a constant or constant object?
616 bool isConstant(MachineLocKind Kind) const {
617 return Kind == MachineLocKind::ImmediateKind;
618 }
619
620 /// Check if the Loc field is an entry backup location.
621 bool isEntryBackupLoc() const {
622 return EVKind == EntryValueLocKind::EntryValueBackupKind ||
623 EVKind == EntryValueLocKind::EntryValueCopyBackupKind;
624 }
625
626 /// If this variable is described by register \p Reg holding the entry
627 /// value, return true.
628 bool isEntryValueBackupReg(Register Reg) const {
629 return EVKind == EntryValueLocKind::EntryValueBackupKind && usesReg(Reg);
630 }
631
632 /// If this variable is described by register \p Reg holding a copy of the
633 /// entry value, return true.
634 bool isEntryValueCopyBackupReg(Register Reg) const {
635 return EVKind == EntryValueLocKind::EntryValueCopyBackupKind &&
636 usesReg(Reg);
637 }
638
639 /// If this variable is described in whole or part by \p Reg, return true.
640 bool usesReg(Register Reg) const {
641 MachineLoc RegML;
642 RegML.Kind = MachineLocKind::RegisterKind;
643 RegML.Value.RegNo = Reg;
644 return is_contained(Range: Locs, Element: RegML);
645 }
646
647 /// If this variable is described in whole or part by \p Reg, return true.
648 unsigned getRegIdx(Register Reg) const {
649 for (unsigned Idx = 0; Idx < Locs.size(); ++Idx)
650 if (Locs[Idx].Kind == MachineLocKind::RegisterKind &&
651 Register{static_cast<unsigned>(Locs[Idx].Value.RegNo)} == Reg)
652 return Idx;
653 llvm_unreachable("Could not find given Reg in Locs");
654 }
655
656 /// If this variable is described in whole or part by 1 or more registers,
657 /// add each of them to \p Regs and return true.
658 bool getDescribingRegs(SmallVectorImpl<uint32_t> &Regs) const {
659 bool AnyRegs = false;
660 for (const auto &Loc : Locs)
661 if (Loc.Kind == MachineLocKind::RegisterKind) {
662 Regs.push_back(Elt: Loc.Value.RegNo);
663 AnyRegs = true;
664 }
665 return AnyRegs;
666 }
667
668 bool containsSpillLocs() const {
669 return any_of(Range: Locs, P: [](VarLoc::MachineLoc ML) {
670 return ML.Kind == VarLoc::MachineLocKind::SpillLocKind;
671 });
672 }
673
674 /// If this variable is described in whole or part by \p SpillLocation,
675 /// return true.
676 bool usesSpillLoc(SpillLoc SpillLocation) const {
677 MachineLoc SpillML;
678 SpillML.Kind = MachineLocKind::SpillLocKind;
679 SpillML.Value.SpillLocation = SpillLocation;
680 return is_contained(Range: Locs, Element: SpillML);
681 }
682
683 /// If this variable is described in whole or part by \p SpillLocation,
684 /// return the index .
685 unsigned getSpillLocIdx(SpillLoc SpillLocation) const {
686 for (unsigned Idx = 0; Idx < Locs.size(); ++Idx)
687 if (Locs[Idx].Kind == MachineLocKind::SpillLocKind &&
688 Locs[Idx].Value.SpillLocation == SpillLocation)
689 return Idx;
690 llvm_unreachable("Could not find given SpillLoc in Locs");
691 }
692
693 bool containsWasmLocs() const {
694 return any_of(Range: Locs, P: [](VarLoc::MachineLoc ML) {
695 return ML.Kind == VarLoc::MachineLocKind::WasmLocKind;
696 });
697 }
698
699 /// If this variable is described in whole or part by \p WasmLocation,
700 /// return true.
701 bool usesWasmLoc(WasmLoc WasmLocation) const {
702 MachineLoc WasmML;
703 WasmML.Kind = MachineLocKind::WasmLocKind;
704 WasmML.Value.WasmLocation = WasmLocation;
705 return is_contained(Range: Locs, Element: WasmML);
706 }
707
708 /// Determine whether the lexical scope of this value's debug location
709 /// dominates MBB.
710 bool dominates(LexicalScopes &LS, MachineBasicBlock &MBB) const {
711 return LS.dominates(DL: MI.getDebugLoc().get(), MBB: &MBB);
712 }
713
714#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
715 // TRI and TII can be null.
716 void dump(const TargetRegisterInfo *TRI, const TargetInstrInfo *TII,
717 raw_ostream &Out = dbgs()) const {
718 Out << "VarLoc(";
719 for (const MachineLoc &MLoc : Locs) {
720 if (Locs.begin() != &MLoc)
721 Out << ", ";
722 switch (MLoc.Kind) {
723 case MachineLocKind::RegisterKind:
724 Out << printReg(MLoc.Value.RegNo, TRI);
725 break;
726 case MachineLocKind::SpillLocKind:
727 Out << printReg(MLoc.Value.SpillLocation.SpillBase, TRI);
728 Out << "[" << MLoc.Value.SpillLocation.SpillOffset.getFixed() << " + "
729 << MLoc.Value.SpillLocation.SpillOffset.getScalable()
730 << "x vscale"
731 << "]";
732 break;
733 case MachineLocKind::ImmediateKind:
734 Out << MLoc.Value.Immediate;
735 break;
736 case MachineLocKind::WasmLocKind: {
737 if (TII) {
738 auto Indices = TII->getSerializableTargetIndices();
739 auto Found =
740 find_if(Indices, [&](const std::pair<int, const char *> &I) {
741 return I.first == MLoc.Value.WasmLocation.Index;
742 });
743 assert(Found != Indices.end());
744 Out << Found->second;
745 if (MLoc.Value.WasmLocation.Offset > 0)
746 Out << " + " << MLoc.Value.WasmLocation.Offset;
747 } else {
748 Out << "WasmLoc";
749 }
750 break;
751 }
752 case MachineLocKind::InvalidKind:
753 llvm_unreachable("Invalid VarLoc in dump method");
754 }
755 }
756
757 Out << ", \"" << Var.getVariable()->getName() << "\", " << *Expr << ", ";
758 if (Var.getInlinedAt())
759 Out << "!" << Var.getInlinedAt()->getMetadataID() << ")\n";
760 else
761 Out << "(null))";
762
763 if (isEntryBackupLoc())
764 Out << " (backup loc)\n";
765 else
766 Out << "\n";
767 }
768#endif
769
770 bool operator==(const VarLoc &Other) const {
771 return std::tie(args: EVKind, args: Var, args: Expr, args: Locs) ==
772 std::tie(args: Other.EVKind, args: Other.Var, args: Other.Expr, args: Other.Locs);
773 }
774
775 /// This operator guarantees that VarLocs are sorted by Variable first.
776 bool operator<(const VarLoc &Other) const {
777 return std::tie(args: Var, args: EVKind, args: Locs, args: Expr) <
778 std::tie(args: Other.Var, args: Other.EVKind, args: Other.Locs, args: Other.Expr);
779 }
780 };
781
782#ifndef NDEBUG
783 using VarVec = SmallVector<VarLoc, 32>;
784#endif
785
786 /// VarLocMap is used for two things:
787 /// 1) Assigning LocIndices to a VarLoc. The LocIndices can be used to
788 /// virtually insert a VarLoc into a VarLocSet.
789 /// 2) Given a LocIndex, look up the unique associated VarLoc.
790 class VarLocMap {
791 /// Map a VarLoc to an index within the vector reserved for its location
792 /// within Loc2Vars.
793 std::map<VarLoc, LocIndices> Var2Indices;
794
795 /// Map a location to a vector which holds VarLocs which live in that
796 /// location.
797 SmallDenseMap<LocIndex::u32_location_t, std::vector<VarLoc>> Loc2Vars;
798
799 public:
800 /// Retrieve LocIndices for \p VL.
801 LocIndices insert(const VarLoc &VL) {
802 LocIndices &Indices = Var2Indices[VL];
803 // If Indices is not empty, VL is already in the map.
804 if (!Indices.empty())
805 return Indices;
806 SmallVector<LocIndex::u32_location_t, 4> Locations;
807 // LocIndices are determined by EVKind and MLs; each Register has a
808 // unique location, while all SpillLocs use a single bucket, and any EV
809 // VarLocs use only the Backup bucket or none at all (except the
810 // compulsory entry at the universal location index). LocIndices will
811 // always have an index at the universal location index as the last index.
812 if (VL.EVKind == VarLoc::EntryValueLocKind::NonEntryValueKind) {
813 VL.getDescribingRegs(Regs&: Locations);
814 assert(all_of(Locations,
815 [](auto RegNo) {
816 return (RegNo < LocIndex::kFirstInvalidRegLocation) ||
817 (LocIndex::kFirstVirtualRegLocation <= RegNo);
818 }) &&
819 "Physical or virtual register out of range?");
820 if (VL.containsSpillLocs())
821 Locations.push_back(Elt: LocIndex::kSpillLocation);
822 if (VL.containsWasmLocs())
823 Locations.push_back(Elt: LocIndex::kWasmLocation);
824 } else if (VL.EVKind != VarLoc::EntryValueLocKind::EntryValueKind) {
825 LocIndex::u32_location_t Loc = LocIndex::kEntryValueBackupLocation;
826 Locations.push_back(Elt: Loc);
827 }
828 Locations.push_back(Elt: LocIndex::kUniversalLocation);
829 for (LocIndex::u32_location_t Location : Locations) {
830 auto &Vars = Loc2Vars[Location];
831 Indices.push_back(
832 Elt: {Location, static_cast<LocIndex::u32_index_t>(Vars.size())});
833 Vars.push_back(x: VL);
834 }
835 return Indices;
836 }
837
838 LocIndices getAllIndices(const VarLoc &VL) const {
839 auto IndIt = Var2Indices.find(x: VL);
840 assert(IndIt != Var2Indices.end() && "VarLoc not tracked");
841 return IndIt->second;
842 }
843
844 /// Retrieve the unique VarLoc associated with \p ID.
845 const VarLoc &operator[](LocIndex ID) const {
846 auto LocIt = Loc2Vars.find(Val: ID.Location);
847 assert(LocIt != Loc2Vars.end() && "Location not tracked");
848 return LocIt->second[ID.Index];
849 }
850 };
851
852 using VarLocInMBB =
853 SmallDenseMap<const MachineBasicBlock *, std::unique_ptr<VarLocSet>>;
854 struct TransferDebugPair {
855 MachineInstr *TransferInst; ///< Instruction where this transfer occurs.
856 LocIndex LocationID; ///< Location number for the transfer dest.
857 };
858 using TransferMap = SmallVector<TransferDebugPair, 4>;
859 // Types for recording Entry Var Locations emitted by a single MachineInstr,
860 // as well as recording MachineInstr which last defined a register.
861 using InstToEntryLocMap = std::multimap<const MachineInstr *, LocIndex>;
862 using RegDefToInstMap = DenseMap<Register, MachineInstr *>;
863
864 // Types for recording sets of variable fragments that overlap. For a given
865 // local variable, we record all other fragments of that variable that could
866 // overlap it, to reduce search time.
867 using FragmentOfVar =
868 std::pair<const DILocalVariable *, DIExpression::FragmentInfo>;
869 using OverlapMap =
870 DenseMap<FragmentOfVar, SmallVector<DIExpression::FragmentInfo, 1>>;
871
872 // Helper while building OverlapMap, a map of all fragments seen for a given
873 // DILocalVariable.
874 using VarToFragments =
875 DenseMap<const DILocalVariable *, SmallSet<FragmentInfo, 4>>;
876
877 /// Collects all VarLocs from \p CollectFrom. Each unique VarLoc is added
878 /// to \p Collected once, in order of insertion into \p VarLocIDs.
879 static void collectAllVarLocs(SmallVectorImpl<VarLoc> &Collected,
880 const VarLocSet &CollectFrom,
881 const VarLocMap &VarLocIDs);
882
883 /// Get the registers which are used by VarLocs of kind RegisterKind tracked
884 /// by \p CollectFrom.
885 void getUsedRegs(const VarLocSet &CollectFrom,
886 SmallVectorImpl<Register> &UsedRegs) const;
887
888 /// This holds the working set of currently open ranges. For fast
889 /// access, this is done both as a set of VarLocIDs, and a map of
890 /// DebugVariable to recent VarLocID. Note that a DBG_VALUE ends all
891 /// previous open ranges for the same variable. In addition, we keep
892 /// two different maps (Vars/EntryValuesBackupVars), so erase/insert
893 /// methods act differently depending on whether a VarLoc is primary
894 /// location or backup one. In the case the VarLoc is backup location
895 /// we will erase/insert from the EntryValuesBackupVars map, otherwise
896 /// we perform the operation on the Vars.
897 class OpenRangesSet {
898 VarLocSet::Allocator &Alloc;
899 VarLocSet VarLocs;
900 // Map the DebugVariable to recent primary location ID.
901 SmallDenseMap<DebugVariable, LocIndices, 8> Vars;
902 // Map the DebugVariable to recent backup location ID.
903 SmallDenseMap<DebugVariable, LocIndices, 8> EntryValuesBackupVars;
904 OverlapMap &OverlappingFragments;
905
906 public:
907 OpenRangesSet(VarLocSet::Allocator &Alloc, OverlapMap &_OLapMap)
908 : Alloc(Alloc), VarLocs(Alloc), OverlappingFragments(_OLapMap) {}
909
910 const VarLocSet &getVarLocs() const { return VarLocs; }
911
912 // Fetches all VarLocs in \p VarLocIDs and inserts them into \p Collected.
913 // This method is needed to get every VarLoc once, as each VarLoc may have
914 // multiple indices in a VarLocMap (corresponding to each applicable
915 // location), but all VarLocs appear exactly once at the universal location
916 // index.
917 void getUniqueVarLocs(SmallVectorImpl<VarLoc> &Collected,
918 const VarLocMap &VarLocIDs) const {
919 collectAllVarLocs(Collected, CollectFrom: VarLocs, VarLocIDs);
920 }
921
922 /// Terminate all open ranges for VL.Var by removing it from the set.
923 void erase(const VarLoc &VL);
924
925 /// Terminate all open ranges listed as indices in \c KillSet with
926 /// \c Location by removing them from the set.
927 void erase(const VarLocsInRange &KillSet, const VarLocMap &VarLocIDs,
928 LocIndex::u32_location_t Location);
929
930 /// Insert a new range into the set.
931 void insert(LocIndices VarLocIDs, const VarLoc &VL);
932
933 /// Insert a set of ranges.
934 void insertFromLocSet(const VarLocSet &ToLoad, const VarLocMap &Map);
935
936 std::optional<LocIndices> getEntryValueBackup(DebugVariable Var);
937
938 /// Empty the set.
939 void clear() {
940 VarLocs.clear();
941 Vars.clear();
942 EntryValuesBackupVars.clear();
943 }
944
945 /// Return whether the set is empty or not.
946 bool empty() const {
947 assert(Vars.empty() == EntryValuesBackupVars.empty() &&
948 Vars.empty() == VarLocs.empty() &&
949 "open ranges are inconsistent");
950 return VarLocs.empty();
951 }
952
953 /// Get an empty range of VarLoc IDs.
954 auto getEmptyVarLocRange() const {
955 return iterator_range<VarLocSet::const_iterator>(getVarLocs().end(),
956 getVarLocs().end());
957 }
958
959 /// Get all set IDs for VarLocs with MLs of kind RegisterKind in \p Reg.
960 auto getRegisterVarLocs(Register Reg) const {
961 return LocIndex::indexRangeForLocation(Set: getVarLocs(), Location: Reg);
962 }
963
964 /// Get all set IDs for VarLocs with MLs of kind SpillLocKind.
965 auto getSpillVarLocs() const {
966 return LocIndex::indexRangeForLocation(Set: getVarLocs(),
967 Location: LocIndex::kSpillLocation);
968 }
969
970 /// Get all set IDs for VarLocs of EVKind EntryValueBackupKind or
971 /// EntryValueCopyBackupKind.
972 auto getEntryValueBackupVarLocs() const {
973 return LocIndex::indexRangeForLocation(
974 Set: getVarLocs(), Location: LocIndex::kEntryValueBackupLocation);
975 }
976
977 /// Get all set IDs for VarLocs with MLs of kind WasmLocKind.
978 auto getWasmVarLocs() const {
979 return LocIndex::indexRangeForLocation(Set: getVarLocs(),
980 Location: LocIndex::kWasmLocation);
981 }
982 };
983
984 /// Collect all VarLoc IDs from \p CollectFrom for VarLocs with MLs of kind
985 /// RegisterKind which are located in any reg in \p Regs. The IDs for each
986 /// VarLoc correspond to entries in the universal location bucket, which every
987 /// VarLoc has exactly 1 entry for. Insert collected IDs into \p Collected.
988 static void collectIDsForRegs(VarLocsInRange &Collected,
989 const DefinedRegsSet &Regs,
990 const VarLocSet &CollectFrom,
991 const VarLocMap &VarLocIDs);
992
993 VarLocSet &getVarLocsInMBB(const MachineBasicBlock *MBB, VarLocInMBB &Locs) {
994 std::unique_ptr<VarLocSet> &VLS = Locs[MBB];
995 if (!VLS)
996 VLS = std::make_unique<VarLocSet>(args&: Alloc);
997 return *VLS;
998 }
999
1000 const VarLocSet &getVarLocsInMBB(const MachineBasicBlock *MBB,
1001 const VarLocInMBB &Locs) const {
1002 auto It = Locs.find(Val: MBB);
1003 assert(It != Locs.end() && "MBB not in map");
1004 return *It->second;
1005 }
1006
1007 /// Tests whether this instruction is a spill to a stack location.
1008 bool isSpillInstruction(const MachineInstr &MI, MachineFunction *MF);
1009
1010 /// Decide if @MI is a spill instruction and return true if it is. We use 2
1011 /// criteria to make this decision:
1012 /// - Is this instruction a store to a spill slot?
1013 /// - Is there a register operand that is both used and killed?
1014 /// TODO: Store optimization can fold spills into other stores (including
1015 /// other spills). We do not handle this yet (more than one memory operand).
1016 bool isLocationSpill(const MachineInstr &MI, MachineFunction *MF,
1017 Register &Reg);
1018
1019 /// Returns true if the given machine instruction is a debug value which we
1020 /// can emit entry values for.
1021 ///
1022 /// Currently, we generate debug entry values only for parameters that are
1023 /// unmodified throughout the function and located in a register.
1024 bool isEntryValueCandidate(const MachineInstr &MI,
1025 const DefinedRegsSet &Regs) const;
1026
1027 /// If a given instruction is identified as a spill, return the spill location
1028 /// and set \p Reg to the spilled register.
1029 std::optional<VarLoc::SpillLoc> isRestoreInstruction(const MachineInstr &MI,
1030 MachineFunction *MF,
1031 Register &Reg);
1032 /// Given a spill instruction, extract the register and offset used to
1033 /// address the spill location in a target independent way.
1034 VarLoc::SpillLoc extractSpillBaseRegAndOffset(const MachineInstr &MI);
1035 void insertTransferDebugPair(MachineInstr &MI, OpenRangesSet &OpenRanges,
1036 TransferMap &Transfers, VarLocMap &VarLocIDs,
1037 LocIndex OldVarID, TransferKind Kind,
1038 const VarLoc::MachineLoc &OldLoc,
1039 Register NewReg = Register());
1040
1041 void transferDebugValue(const MachineInstr &MI, OpenRangesSet &OpenRanges,
1042 VarLocMap &VarLocIDs,
1043 InstToEntryLocMap &EntryValTransfers,
1044 RegDefToInstMap &RegSetInstrs);
1045 void transferSpillOrRestoreInst(MachineInstr &MI, OpenRangesSet &OpenRanges,
1046 VarLocMap &VarLocIDs, TransferMap &Transfers);
1047 void cleanupEntryValueTransfers(const MachineInstr *MI,
1048 OpenRangesSet &OpenRanges,
1049 VarLocMap &VarLocIDs, const VarLoc &EntryVL,
1050 InstToEntryLocMap &EntryValTransfers);
1051 void removeEntryValue(const MachineInstr &MI, OpenRangesSet &OpenRanges,
1052 VarLocMap &VarLocIDs, const VarLoc &EntryVL,
1053 InstToEntryLocMap &EntryValTransfers,
1054 RegDefToInstMap &RegSetInstrs);
1055 void emitEntryValues(MachineInstr &MI, OpenRangesSet &OpenRanges,
1056 VarLocMap &VarLocIDs,
1057 InstToEntryLocMap &EntryValTransfers,
1058 VarLocsInRange &KillSet);
1059 void recordEntryValue(const MachineInstr &MI,
1060 const DefinedRegsSet &DefinedRegs,
1061 OpenRangesSet &OpenRanges, VarLocMap &VarLocIDs);
1062 void transferRegisterCopy(MachineInstr &MI, OpenRangesSet &OpenRanges,
1063 VarLocMap &VarLocIDs, TransferMap &Transfers);
1064 void transferRegisterDef(MachineInstr &MI, OpenRangesSet &OpenRanges,
1065 VarLocMap &VarLocIDs,
1066 InstToEntryLocMap &EntryValTransfers,
1067 RegDefToInstMap &RegSetInstrs);
1068 void transferWasmDef(MachineInstr &MI, OpenRangesSet &OpenRanges,
1069 VarLocMap &VarLocIDs);
1070 bool transferTerminator(MachineBasicBlock *MBB, OpenRangesSet &OpenRanges,
1071 VarLocInMBB &OutLocs, const VarLocMap &VarLocIDs);
1072
1073 void process(MachineInstr &MI, OpenRangesSet &OpenRanges,
1074 VarLocMap &VarLocIDs, TransferMap &Transfers,
1075 InstToEntryLocMap &EntryValTransfers,
1076 RegDefToInstMap &RegSetInstrs);
1077
1078 void accumulateFragmentMap(MachineInstr &MI, VarToFragments &SeenFragments,
1079 OverlapMap &OLapMap);
1080
1081 bool join(MachineBasicBlock &MBB, VarLocInMBB &OutLocs, VarLocInMBB &InLocs,
1082 const VarLocMap &VarLocIDs,
1083 SmallPtrSet<const MachineBasicBlock *, 16> &Visited,
1084 SmallPtrSetImpl<const MachineBasicBlock *> &ArtificialBlocks);
1085
1086 /// Create DBG_VALUE insts for inlocs that have been propagated but
1087 /// had their instruction creation deferred.
1088 void flushPendingLocs(VarLocInMBB &PendingInLocs, VarLocMap &VarLocIDs);
1089
1090 bool ExtendRanges(MachineFunction &MF, MachineDominatorTree *DomTree,
1091 bool ShouldEmitDebugEntryValues, unsigned InputBBLimit,
1092 unsigned InputDbgValLimit) override;
1093
1094public:
1095 /// Default construct and initialize the pass.
1096 VarLocBasedLDV();
1097
1098 ~VarLocBasedLDV() override;
1099
1100 /// Print to ostream with a message.
1101 void printVarLocInMBB(const MachineFunction &MF, const VarLocInMBB &V,
1102 const VarLocMap &VarLocIDs, const char *msg,
1103 raw_ostream &Out) const;
1104};
1105
1106} // end anonymous namespace
1107
1108//===----------------------------------------------------------------------===//
1109// Implementation
1110//===----------------------------------------------------------------------===//
1111
1112VarLocBasedLDV::VarLocBasedLDV() = default;
1113
1114VarLocBasedLDV::~VarLocBasedLDV() = default;
1115
1116/// Erase a variable from the set of open ranges, and additionally erase any
1117/// fragments that may overlap it. If the VarLoc is a backup location, erase
1118/// the variable from the EntryValuesBackupVars set, indicating we should stop
1119/// tracking its backup entry location. Otherwise, if the VarLoc is primary
1120/// location, erase the variable from the Vars set.
1121void VarLocBasedLDV::OpenRangesSet::erase(const VarLoc &VL) {
1122 // Erasure helper.
1123 auto DoErase = [&VL, this](DebugVariable VarToErase) {
1124 auto *EraseFrom = VL.isEntryBackupLoc() ? &EntryValuesBackupVars : &Vars;
1125 auto It = EraseFrom->find(Val: VarToErase);
1126 if (It != EraseFrom->end()) {
1127 LocIndices IDs = It->second;
1128 for (LocIndex ID : IDs)
1129 VarLocs.reset(Index: ID.getAsRawInteger());
1130 EraseFrom->erase(I: It);
1131 }
1132 };
1133
1134 DebugVariable Var = VL.Var;
1135
1136 // Erase the variable/fragment that ends here.
1137 DoErase(Var);
1138
1139 // Extract the fragment. Interpret an empty fragment as one that covers all
1140 // possible bits.
1141 FragmentInfo ThisFragment = Var.getFragmentOrDefault();
1142
1143 // There may be fragments that overlap the designated fragment. Look them up
1144 // in the pre-computed overlap map, and erase them too.
1145 auto MapIt = OverlappingFragments.find(Val: {Var.getVariable(), ThisFragment});
1146 if (MapIt != OverlappingFragments.end()) {
1147 for (auto Fragment : MapIt->second) {
1148 VarLocBasedLDV::OptFragmentInfo FragmentHolder;
1149 if (!DebugVariable::isDefaultFragment(F: Fragment))
1150 FragmentHolder = VarLocBasedLDV::OptFragmentInfo(Fragment);
1151 DoErase({Var.getVariable(), FragmentHolder, Var.getInlinedAt()});
1152 }
1153 }
1154}
1155
1156void VarLocBasedLDV::OpenRangesSet::erase(const VarLocsInRange &KillSet,
1157 const VarLocMap &VarLocIDs,
1158 LocIndex::u32_location_t Location) {
1159 VarLocSet RemoveSet(Alloc);
1160 for (LocIndex::u32_index_t ID : KillSet) {
1161 const VarLoc &VL = VarLocIDs[LocIndex(Location, ID)];
1162 auto *EraseFrom = VL.isEntryBackupLoc() ? &EntryValuesBackupVars : &Vars;
1163 EraseFrom->erase(Val: VL.Var);
1164 LocIndices VLI = VarLocIDs.getAllIndices(VL);
1165 for (LocIndex ID : VLI)
1166 RemoveSet.set(ID.getAsRawInteger());
1167 }
1168 VarLocs.intersectWithComplement(Other: RemoveSet);
1169}
1170
1171void VarLocBasedLDV::OpenRangesSet::insertFromLocSet(const VarLocSet &ToLoad,
1172 const VarLocMap &Map) {
1173 VarLocsInRange UniqueVarLocIDs;
1174 DefinedRegsSet Regs;
1175 Regs.insert(V: LocIndex::kUniversalLocation);
1176 collectIDsForRegs(Collected&: UniqueVarLocIDs, Regs, CollectFrom: ToLoad, VarLocIDs: Map);
1177 for (uint64_t ID : UniqueVarLocIDs) {
1178 LocIndex Idx = LocIndex::fromRawInteger(ID);
1179 const VarLoc &VarL = Map[Idx];
1180 const LocIndices Indices = Map.getAllIndices(VL: VarL);
1181 insert(VarLocIDs: Indices, VL: VarL);
1182 }
1183}
1184
1185void VarLocBasedLDV::OpenRangesSet::insert(LocIndices VarLocIDs,
1186 const VarLoc &VL) {
1187 auto *InsertInto = VL.isEntryBackupLoc() ? &EntryValuesBackupVars : &Vars;
1188 for (LocIndex ID : VarLocIDs)
1189 VarLocs.set(ID.getAsRawInteger());
1190 InsertInto->insert(KV: {VL.Var, VarLocIDs});
1191}
1192
1193/// Return the Loc ID of an entry value backup location, if it exists for the
1194/// variable.
1195std::optional<LocIndices>
1196VarLocBasedLDV::OpenRangesSet::getEntryValueBackup(DebugVariable Var) {
1197 auto It = EntryValuesBackupVars.find(Val: Var);
1198 if (It != EntryValuesBackupVars.end())
1199 return It->second;
1200
1201 return std::nullopt;
1202}
1203
1204void VarLocBasedLDV::collectIDsForRegs(VarLocsInRange &Collected,
1205 const DefinedRegsSet &Regs,
1206 const VarLocSet &CollectFrom,
1207 const VarLocMap &VarLocIDs) {
1208 assert(!Regs.empty() && "Nothing to collect");
1209 SmallVector<Register, 32> SortedRegs;
1210 append_range(C&: SortedRegs, R: Regs);
1211 array_pod_sort(Start: SortedRegs.begin(), End: SortedRegs.end());
1212 auto It = CollectFrom.find(Index: LocIndex::rawIndexForReg(Reg: SortedRegs.front()));
1213 auto End = CollectFrom.end();
1214 for (Register Reg : SortedRegs) {
1215 // The half-open interval [FirstIndexForReg, FirstInvalidIndex) contains
1216 // all possible VarLoc IDs for VarLocs with MLs of kind RegisterKind which
1217 // live in Reg.
1218 uint64_t FirstIndexForReg = LocIndex::rawIndexForReg(Reg);
1219 uint64_t FirstInvalidIndex = LocIndex::rawIndexForReg(Reg: Reg + 1);
1220 It.advanceToLowerBound(Index: FirstIndexForReg);
1221
1222 // Iterate through that half-open interval and collect all the set IDs.
1223 for (; It != End && *It < FirstInvalidIndex; ++It) {
1224 LocIndex ItIdx = LocIndex::fromRawInteger(ID: *It);
1225 const VarLoc &VL = VarLocIDs[ItIdx];
1226 LocIndices LI = VarLocIDs.getAllIndices(VL);
1227 // For now, the back index is always the universal location index.
1228 assert(LI.back().Location == LocIndex::kUniversalLocation &&
1229 "Unexpected order of LocIndices for VarLoc; was it inserted into "
1230 "the VarLocMap correctly?");
1231 Collected.insert(V: LI.back().Index);
1232 }
1233
1234 if (It == End)
1235 return;
1236 }
1237}
1238
1239void VarLocBasedLDV::getUsedRegs(const VarLocSet &CollectFrom,
1240 SmallVectorImpl<Register> &UsedRegs) const {
1241 // All register-based VarLocs are assigned indices greater than or equal to
1242 // FirstRegIndex.
1243 uint64_t FirstRegIndex =
1244 LocIndex::rawIndexForReg(Reg: LocIndex::kFirstRegLocation);
1245 uint64_t FirstInvalidIndex =
1246 LocIndex::rawIndexForReg(Reg: LocIndex::kFirstInvalidRegLocation);
1247 uint64_t FirstVirtualRegIndex =
1248 LocIndex::rawIndexForReg(Reg: LocIndex::kFirstVirtualRegLocation);
1249 auto doGetUsedRegs = [&](VarLocSet::const_iterator &It) {
1250 // We found a VarLoc ID for a VarLoc that lives in a register. Figure out
1251 // which register and add it to UsedRegs.
1252 uint32_t FoundReg = LocIndex::fromRawInteger(ID: *It).Location;
1253 assert((UsedRegs.empty() || FoundReg != UsedRegs.back()) &&
1254 "Duplicate used reg");
1255 UsedRegs.push_back(Elt: FoundReg);
1256
1257 // Skip to the next /set/ register. Note that this finds a lower bound, so
1258 // even if there aren't any VarLocs living in `FoundReg+1`, we're still
1259 // guaranteed to move on to the next register (or to end()).
1260 uint64_t NextRegIndex = LocIndex::rawIndexForReg(Reg: FoundReg + 1);
1261 It.advanceToLowerBound(Index: NextRegIndex);
1262 };
1263 for (auto It = CollectFrom.find(Index: FirstRegIndex),
1264 End = CollectFrom.find(Index: FirstInvalidIndex);
1265 It != End;) {
1266 doGetUsedRegs(It);
1267 }
1268 for (auto It = CollectFrom.find(Index: FirstVirtualRegIndex),
1269 End = CollectFrom.end();
1270 It != End;) {
1271 doGetUsedRegs(It);
1272 }
1273}
1274
1275//===----------------------------------------------------------------------===//
1276// Debug Range Extension Implementation
1277//===----------------------------------------------------------------------===//
1278
1279#ifndef NDEBUG
1280void VarLocBasedLDV::printVarLocInMBB(const MachineFunction &MF,
1281 const VarLocInMBB &V,
1282 const VarLocMap &VarLocIDs,
1283 const char *msg,
1284 raw_ostream &Out) const {
1285 Out << '\n' << msg << '\n';
1286 for (const MachineBasicBlock &BB : MF) {
1287 if (!V.count(&BB))
1288 continue;
1289 const VarLocSet &L = getVarLocsInMBB(&BB, V);
1290 if (L.empty())
1291 continue;
1292 SmallVector<VarLoc, 32> VarLocs;
1293 collectAllVarLocs(VarLocs, L, VarLocIDs);
1294 Out << "MBB: " << BB.getNumber() << ":\n";
1295 for (const VarLoc &VL : VarLocs) {
1296 Out << " Var: " << VL.Var.getVariable()->getName();
1297 Out << " MI: ";
1298 VL.dump(TRI, TII, Out);
1299 }
1300 }
1301 Out << "\n";
1302}
1303#endif
1304
1305VarLocBasedLDV::VarLoc::SpillLoc
1306VarLocBasedLDV::extractSpillBaseRegAndOffset(const MachineInstr &MI) {
1307 assert(MI.hasOneMemOperand() &&
1308 "Spill instruction does not have exactly one memory operand?");
1309 auto MMOI = MI.memoperands_begin();
1310 const PseudoSourceValue *PVal = (*MMOI)->getPseudoValue();
1311 assert(PVal->kind() == PseudoSourceValue::FixedStack &&
1312 "Inconsistent memory operand in spill instruction");
1313 int FI = cast<FixedStackPseudoSourceValue>(Val: PVal)->getFrameIndex();
1314 const MachineBasicBlock *MBB = MI.getParent();
1315 Register Reg;
1316 StackOffset Offset = TFI->getFrameIndexReference(MF: *MBB->getParent(), FI, FrameReg&: Reg);
1317 return {.SpillBase: Reg, .SpillOffset: Offset};
1318}
1319
1320/// Do cleanup of \p EntryValTransfers created by \p TRInst, by removing the
1321/// Transfer, which uses the to-be-deleted \p EntryVL.
1322void VarLocBasedLDV::cleanupEntryValueTransfers(
1323 const MachineInstr *TRInst, OpenRangesSet &OpenRanges, VarLocMap &VarLocIDs,
1324 const VarLoc &EntryVL, InstToEntryLocMap &EntryValTransfers) {
1325 if (EntryValTransfers.empty() || TRInst == nullptr)
1326 return;
1327
1328 auto TransRange = EntryValTransfers.equal_range(x: TRInst);
1329 for (auto &TDPair : llvm::make_range(p: TransRange)) {
1330 const VarLoc &EmittedEV = VarLocIDs[TDPair.second];
1331 if (std::tie(args: EntryVL.Var, args: EntryVL.Locs[0].Value.RegNo, args: EntryVL.Expr) ==
1332 std::tie(args: EmittedEV.Var, args: EmittedEV.Locs[0].Value.RegNo,
1333 args: EmittedEV.Expr)) {
1334 OpenRanges.erase(VL: EmittedEV);
1335 EntryValTransfers.erase(x: TRInst);
1336 break;
1337 }
1338 }
1339}
1340
1341/// Try to salvage the debug entry value if we encounter a new debug value
1342/// describing the same parameter, otherwise stop tracking the value. Return
1343/// true if we should stop tracking the entry value and do the cleanup of
1344/// emitted Entry Value Transfers, otherwise return false.
1345void VarLocBasedLDV::removeEntryValue(const MachineInstr &MI,
1346 OpenRangesSet &OpenRanges,
1347 VarLocMap &VarLocIDs,
1348 const VarLoc &EntryVL,
1349 InstToEntryLocMap &EntryValTransfers,
1350 RegDefToInstMap &RegSetInstrs) {
1351 // Skip the DBG_VALUE which is the debug entry value itself.
1352 if (&MI == &EntryVL.MI)
1353 return;
1354
1355 // If the parameter's location is not register location, we can not track
1356 // the entry value any more. It doesn't have the TransferInst which defines
1357 // register, so no Entry Value Transfers have been emitted already.
1358 if (!MI.getDebugOperand(Index: 0).isReg())
1359 return;
1360
1361 // Try to get non-debug instruction responsible for the DBG_VALUE.
1362 Register Reg = MI.getDebugOperand(Index: 0).getReg();
1363 const MachineInstr *TransferInst =
1364 Reg.isValid() ? RegSetInstrs.lookup(Val: Reg) : nullptr;
1365
1366 // Case of the parameter's DBG_VALUE at the start of entry MBB.
1367 if (!TransferInst && !LastNonDbgMI && MI.getParent()->isEntryBlock())
1368 return;
1369
1370 // If the debug expression from the DBG_VALUE is not empty, we can assume the
1371 // parameter's value has changed indicating that we should stop tracking its
1372 // entry value as well.
1373 if (MI.getDebugExpression()->getNumElements() == 0 && TransferInst) {
1374 // If the DBG_VALUE comes from a copy instruction that copies the entry
1375 // value, it means the parameter's value has not changed and we should be
1376 // able to use its entry value.
1377 // TODO: Try to keep tracking of an entry value if we encounter a propagated
1378 // DBG_VALUE describing the copy of the entry value. (Propagated entry value
1379 // does not indicate the parameter modification.)
1380 auto DestSrc = TII->isCopyLikeInstr(MI: *TransferInst);
1381 if (DestSrc) {
1382 const MachineOperand *SrcRegOp, *DestRegOp;
1383 SrcRegOp = DestSrc->Source;
1384 DestRegOp = DestSrc->Destination;
1385 if (Reg == DestRegOp->getReg()) {
1386 for (uint64_t ID : OpenRanges.getEntryValueBackupVarLocs()) {
1387 const VarLoc &VL = VarLocIDs[LocIndex::fromRawInteger(ID)];
1388 if (VL.isEntryValueCopyBackupReg(Reg) &&
1389 // Entry Values should not be variadic.
1390 VL.MI.getDebugOperand(Index: 0).getReg() == SrcRegOp->getReg())
1391 return;
1392 }
1393 }
1394 }
1395 }
1396
1397 LLVM_DEBUG(dbgs() << "Deleting a DBG entry value because of: ";
1398 MI.print(dbgs(), /*IsStandalone*/ false,
1399 /*SkipOpers*/ false, /*SkipDebugLoc*/ false,
1400 /*AddNewLine*/ true, TII));
1401 cleanupEntryValueTransfers(TRInst: TransferInst, OpenRanges, VarLocIDs, EntryVL,
1402 EntryValTransfers);
1403 OpenRanges.erase(VL: EntryVL);
1404}
1405
1406/// End all previous ranges related to @MI and start a new range from @MI
1407/// if it is a DBG_VALUE instr.
1408void VarLocBasedLDV::transferDebugValue(const MachineInstr &MI,
1409 OpenRangesSet &OpenRanges,
1410 VarLocMap &VarLocIDs,
1411 InstToEntryLocMap &EntryValTransfers,
1412 RegDefToInstMap &RegSetInstrs) {
1413 if (!MI.isDebugValue())
1414 return;
1415 const DILocalVariable *Var = MI.getDebugVariable();
1416 const DIExpression *Expr = MI.getDebugExpression();
1417 const DILocation *DebugLoc = MI.getDebugLoc();
1418 const DILocation *InlinedAt = DebugLoc->getInlinedAt();
1419 assert(Var->isValidLocationForIntrinsic(DebugLoc) &&
1420 "Expected inlined-at fields to agree");
1421
1422 DebugVariable V(Var, Expr, InlinedAt);
1423
1424 // Check if this DBG_VALUE indicates a parameter's value changing.
1425 // If that is the case, we should stop tracking its entry value.
1426 auto EntryValBackupID = OpenRanges.getEntryValueBackup(Var: V);
1427 if (Var->isParameter() && EntryValBackupID) {
1428 const VarLoc &EntryVL = VarLocIDs[EntryValBackupID->back()];
1429 removeEntryValue(MI, OpenRanges, VarLocIDs, EntryVL, EntryValTransfers,
1430 RegSetInstrs);
1431 }
1432
1433 if (all_of(Range: MI.debug_operands(), P: [](const MachineOperand &MO) {
1434 return (MO.isReg() && MO.getReg()) || MO.isImm() || MO.isFPImm() ||
1435 MO.isCImm() || MO.isTargetIndex();
1436 })) {
1437 // Use normal VarLoc constructor for registers and immediates.
1438 VarLoc VL(MI);
1439 // End all previous ranges of VL.Var.
1440 OpenRanges.erase(VL);
1441
1442 LocIndices IDs = VarLocIDs.insert(VL);
1443 // Add the VarLoc to OpenRanges from this DBG_VALUE.
1444 OpenRanges.insert(VarLocIDs: IDs, VL);
1445 } else if (MI.memoperands().size() > 0) {
1446 llvm_unreachable("DBG_VALUE with mem operand encountered after regalloc?");
1447 } else {
1448 // This must be an undefined location. If it has an open range, erase it.
1449 assert(MI.isUndefDebugValue() &&
1450 "Unexpected non-undef DBG_VALUE encountered");
1451 VarLoc VL(MI);
1452 OpenRanges.erase(VL);
1453 }
1454}
1455
1456// This should be removed later, doesn't fit the new design.
1457void VarLocBasedLDV::collectAllVarLocs(SmallVectorImpl<VarLoc> &Collected,
1458 const VarLocSet &CollectFrom,
1459 const VarLocMap &VarLocIDs) {
1460 // The half-open interval [FirstIndexForReg, FirstInvalidIndex) contains all
1461 // possible VarLoc IDs for VarLocs with MLs of kind RegisterKind which live
1462 // in Reg.
1463 uint64_t FirstIndex = LocIndex::rawIndexForReg(Reg: LocIndex::kUniversalLocation);
1464 uint64_t FirstInvalidIndex =
1465 LocIndex::rawIndexForReg(Reg: LocIndex::kUniversalLocation + 1);
1466 // Iterate through that half-open interval and collect all the set IDs.
1467 for (auto It = CollectFrom.find(Index: FirstIndex), End = CollectFrom.end();
1468 It != End && *It < FirstInvalidIndex; ++It) {
1469 LocIndex RegIdx = LocIndex::fromRawInteger(ID: *It);
1470 Collected.push_back(Elt: VarLocIDs[RegIdx]);
1471 }
1472}
1473
1474/// Turn the entry value backup locations into primary locations.
1475void VarLocBasedLDV::emitEntryValues(MachineInstr &MI,
1476 OpenRangesSet &OpenRanges,
1477 VarLocMap &VarLocIDs,
1478 InstToEntryLocMap &EntryValTransfers,
1479 VarLocsInRange &KillSet) {
1480 // Do not insert entry value locations after a terminator.
1481 if (MI.isTerminator())
1482 return;
1483
1484 for (uint32_t ID : KillSet) {
1485 // The KillSet IDs are indices for the universal location bucket.
1486 LocIndex Idx = LocIndex(LocIndex::kUniversalLocation, ID);
1487 const VarLoc &VL = VarLocIDs[Idx];
1488 if (!VL.Var.getVariable()->isParameter())
1489 continue;
1490
1491 auto DebugVar = VL.Var;
1492 std::optional<LocIndices> EntryValBackupIDs =
1493 OpenRanges.getEntryValueBackup(Var: DebugVar);
1494
1495 // If the parameter has the entry value backup, it means we should
1496 // be able to use its entry value.
1497 if (!EntryValBackupIDs)
1498 continue;
1499
1500 const VarLoc &EntryVL = VarLocIDs[EntryValBackupIDs->back()];
1501 VarLoc EntryLoc = VarLoc::CreateEntryLoc(MI: EntryVL.MI, EntryExpr: EntryVL.Expr,
1502 Reg: EntryVL.Locs[0].Value.RegNo);
1503 LocIndices EntryValueIDs = VarLocIDs.insert(VL: EntryLoc);
1504 assert(EntryValueIDs.size() == 1 &&
1505 "EntryValue loc should not be variadic");
1506 EntryValTransfers.insert(x: {&MI, EntryValueIDs.back()});
1507 OpenRanges.insert(VarLocIDs: EntryValueIDs, VL: EntryLoc);
1508 }
1509}
1510
1511/// Create new TransferDebugPair and insert it in \p Transfers. The VarLoc
1512/// with \p OldVarID should be deleted form \p OpenRanges and replaced with
1513/// new VarLoc. If \p NewReg is different than default zero value then the
1514/// new location will be register location created by the copy like instruction,
1515/// otherwise it is variable's location on the stack.
1516void VarLocBasedLDV::insertTransferDebugPair(
1517 MachineInstr &MI, OpenRangesSet &OpenRanges, TransferMap &Transfers,
1518 VarLocMap &VarLocIDs, LocIndex OldVarID, TransferKind Kind,
1519 const VarLoc::MachineLoc &OldLoc, Register NewReg) {
1520 const VarLoc &OldVarLoc = VarLocIDs[OldVarID];
1521
1522 auto ProcessVarLoc = [&MI, &OpenRanges, &Transfers, &VarLocIDs](VarLoc &VL) {
1523 LocIndices LocIds = VarLocIDs.insert(VL);
1524
1525 // Close this variable's previous location range.
1526 OpenRanges.erase(VL);
1527
1528 // Record the new location as an open range, and a postponed transfer
1529 // inserting a DBG_VALUE for this location.
1530 OpenRanges.insert(VarLocIDs: LocIds, VL);
1531 assert(!MI.isTerminator() && "Cannot insert DBG_VALUE after terminator");
1532 TransferDebugPair MIP = {.TransferInst: &MI, .LocationID: LocIds.back()};
1533 Transfers.push_back(Elt: MIP);
1534 };
1535
1536 // End all previous ranges of VL.Var.
1537 OpenRanges.erase(VL: VarLocIDs[OldVarID]);
1538 switch (Kind) {
1539 case TransferKind::TransferCopy: {
1540 assert(NewReg &&
1541 "No register supplied when handling a copy of a debug value");
1542 // Create a DBG_VALUE instruction to describe the Var in its new
1543 // register location.
1544 VarLoc VL = VarLoc::CreateCopyLoc(OldVL: OldVarLoc, OldML: OldLoc, NewReg);
1545 ProcessVarLoc(VL);
1546 LLVM_DEBUG({
1547 dbgs() << "Creating VarLoc for register copy:";
1548 VL.dump(TRI, TII);
1549 });
1550 return;
1551 }
1552 case TransferKind::TransferSpill: {
1553 // Create a DBG_VALUE instruction to describe the Var in its spilled
1554 // location.
1555 VarLoc::SpillLoc SpillLocation = extractSpillBaseRegAndOffset(MI);
1556 VarLoc VL = VarLoc::CreateSpillLoc(
1557 OldVL: OldVarLoc, OldML: OldLoc, SpillBase: SpillLocation.SpillBase, SpillOffset: SpillLocation.SpillOffset);
1558 ProcessVarLoc(VL);
1559 LLVM_DEBUG({
1560 dbgs() << "Creating VarLoc for spill:";
1561 VL.dump(TRI, TII);
1562 });
1563 return;
1564 }
1565 case TransferKind::TransferRestore: {
1566 assert(NewReg &&
1567 "No register supplied when handling a restore of a debug value");
1568 // DebugInstr refers to the pre-spill location, therefore we can reuse
1569 // its expression.
1570 VarLoc VL = VarLoc::CreateCopyLoc(OldVL: OldVarLoc, OldML: OldLoc, NewReg);
1571 ProcessVarLoc(VL);
1572 LLVM_DEBUG({
1573 dbgs() << "Creating VarLoc for restore:";
1574 VL.dump(TRI, TII);
1575 });
1576 return;
1577 }
1578 }
1579 llvm_unreachable("Invalid transfer kind");
1580}
1581
1582/// A definition of a register may mark the end of a range.
1583void VarLocBasedLDV::transferRegisterDef(MachineInstr &MI,
1584 OpenRangesSet &OpenRanges,
1585 VarLocMap &VarLocIDs,
1586 InstToEntryLocMap &EntryValTransfers,
1587 RegDefToInstMap &RegSetInstrs) {
1588
1589 // Meta Instructions do not affect the debug liveness of any register they
1590 // define.
1591 if (MI.isMetaInstruction())
1592 return;
1593
1594 MachineFunction *MF = MI.getMF();
1595 const TargetLowering *TLI = MF->getSubtarget().getTargetLowering();
1596 Register SP = TLI->getStackPointerRegisterToSaveRestore();
1597
1598 // Find the regs killed by MI, and find regmasks of preserved regs.
1599 DefinedRegsSet DeadRegs;
1600 SmallVector<const uint32_t *, 4> RegMasks;
1601 for (const MachineOperand &MO : MI.operands()) {
1602 // Determine whether the operand is a register def.
1603 if (MO.isReg() && MO.isDef() && MO.getReg() && MO.getReg().isPhysical() &&
1604 !(MI.isCall() && MO.getReg() == SP)) {
1605 // Remove ranges of all aliased registers.
1606 for (MCRegAliasIterator RAI(MO.getReg(), TRI, true); RAI.isValid(); ++RAI)
1607 // FIXME: Can we break out of this loop early if no insertion occurs?
1608 DeadRegs.insert(V: (*RAI).id());
1609 RegSetInstrs.erase(Val: MO.getReg());
1610 RegSetInstrs.insert(KV: {MO.getReg(), &MI});
1611 } else if (MO.isRegMask()) {
1612 RegMasks.push_back(Elt: MO.getRegMask());
1613 }
1614 }
1615
1616 // Erase VarLocs which reside in one of the dead registers. For performance
1617 // reasons, it's critical to not iterate over the full set of open VarLocs.
1618 // Iterate over the set of dying/used regs instead.
1619 if (!RegMasks.empty()) {
1620 SmallVector<Register, 32> UsedRegs;
1621 getUsedRegs(CollectFrom: OpenRanges.getVarLocs(), UsedRegs);
1622 for (Register Reg : UsedRegs) {
1623 // Remove ranges of all clobbered registers. Register masks don't usually
1624 // list SP as preserved. Assume that call instructions never clobber SP,
1625 // because some backends (e.g., AArch64) never list SP in the regmask.
1626 // While the debug info may be off for an instruction or two around
1627 // callee-cleanup calls, transferring the DEBUG_VALUE across the call is
1628 // still a better user experience.
1629 if (Reg == SP)
1630 continue;
1631 bool AnyRegMaskKillsReg =
1632 any_of(Range&: RegMasks, P: [Reg](const uint32_t *RegMask) {
1633 return MachineOperand::clobbersPhysReg(RegMask, PhysReg: Reg);
1634 });
1635 if (AnyRegMaskKillsReg)
1636 DeadRegs.insert(V: Reg);
1637 if (AnyRegMaskKillsReg) {
1638 RegSetInstrs.erase(Val: Reg);
1639 RegSetInstrs.insert(KV: {Reg, &MI});
1640 }
1641 }
1642 }
1643
1644 if (DeadRegs.empty())
1645 return;
1646
1647 VarLocsInRange KillSet;
1648 collectIDsForRegs(Collected&: KillSet, Regs: DeadRegs, CollectFrom: OpenRanges.getVarLocs(), VarLocIDs);
1649 OpenRanges.erase(KillSet, VarLocIDs, Location: LocIndex::kUniversalLocation);
1650
1651 if (ShouldEmitDebugEntryValues)
1652 emitEntryValues(MI, OpenRanges, VarLocIDs, EntryValTransfers, KillSet);
1653}
1654
1655void VarLocBasedLDV::transferWasmDef(MachineInstr &MI,
1656 OpenRangesSet &OpenRanges,
1657 VarLocMap &VarLocIDs) {
1658 // If this is not a Wasm local.set or local.tee, which sets local values,
1659 // return.
1660 int Index;
1661 int64_t Offset;
1662 if (!TII->isExplicitTargetIndexDef(MI, Index, Offset))
1663 return;
1664
1665 // Find the target indices killed by MI, and delete those variable locations
1666 // from the open range.
1667 VarLocsInRange KillSet;
1668 VarLoc::WasmLoc Loc{.Index: Index, .Offset: Offset};
1669 for (uint64_t ID : OpenRanges.getWasmVarLocs()) {
1670 LocIndex Idx = LocIndex::fromRawInteger(ID);
1671 const VarLoc &VL = VarLocIDs[Idx];
1672 assert(VL.containsWasmLocs() && "Broken VarLocSet?");
1673 if (VL.usesWasmLoc(WasmLocation: Loc))
1674 KillSet.insert(V: ID);
1675 }
1676 OpenRanges.erase(KillSet, VarLocIDs, Location: LocIndex::kWasmLocation);
1677}
1678
1679bool VarLocBasedLDV::isSpillInstruction(const MachineInstr &MI,
1680 MachineFunction *MF) {
1681 // TODO: Handle multiple stores folded into one.
1682 if (!MI.hasOneMemOperand())
1683 return false;
1684
1685 if (!MI.getSpillSize(TII) && !MI.getFoldedSpillSize(TII))
1686 return false; // This is not a spill instruction, since no valid size was
1687 // returned from either function.
1688
1689 return true;
1690}
1691
1692bool VarLocBasedLDV::isLocationSpill(const MachineInstr &MI,
1693 MachineFunction *MF, Register &Reg) {
1694 if (!isSpillInstruction(MI, MF))
1695 return false;
1696
1697 auto isKilledReg = [&](const MachineOperand MO, Register &Reg) {
1698 if (!MO.isReg() || !MO.isUse()) {
1699 Reg = 0;
1700 return false;
1701 }
1702 Reg = MO.getReg();
1703 return MO.isKill();
1704 };
1705
1706 for (const MachineOperand &MO : MI.operands()) {
1707 // In a spill instruction generated by the InlineSpiller the spilled
1708 // register has its kill flag set.
1709 if (isKilledReg(MO, Reg))
1710 return true;
1711 if (Reg != 0) {
1712 // Check whether next instruction kills the spilled register.
1713 // FIXME: Current solution does not cover search for killed register in
1714 // bundles and instructions further down the chain.
1715 auto NextI = std::next(x: MI.getIterator());
1716 // Skip next instruction that points to basic block end iterator.
1717 if (MI.getParent()->end() == NextI)
1718 continue;
1719 Register RegNext;
1720 for (const MachineOperand &MONext : NextI->operands()) {
1721 // Return true if we came across the register from the
1722 // previous spill instruction that is killed in NextI.
1723 if (isKilledReg(MONext, RegNext) && RegNext == Reg)
1724 return true;
1725 }
1726 }
1727 }
1728 // Return false if we didn't find spilled register.
1729 return false;
1730}
1731
1732std::optional<VarLocBasedLDV::VarLoc::SpillLoc>
1733VarLocBasedLDV::isRestoreInstruction(const MachineInstr &MI,
1734 MachineFunction *MF, Register &Reg) {
1735 if (!MI.hasOneMemOperand())
1736 return std::nullopt;
1737
1738 // FIXME: Handle folded restore instructions with more than one memory
1739 // operand.
1740 if (MI.getRestoreSize(TII)) {
1741 Reg = MI.getOperand(i: 0).getReg();
1742 return extractSpillBaseRegAndOffset(MI);
1743 }
1744 return std::nullopt;
1745}
1746
1747/// A spilled register may indicate that we have to end the current range of
1748/// a variable and create a new one for the spill location.
1749/// A restored register may indicate the reverse situation.
1750/// We don't want to insert any instructions in process(), so we just create
1751/// the DBG_VALUE without inserting it and keep track of it in \p Transfers.
1752/// It will be inserted into the BB when we're done iterating over the
1753/// instructions.
1754void VarLocBasedLDV::transferSpillOrRestoreInst(MachineInstr &MI,
1755 OpenRangesSet &OpenRanges,
1756 VarLocMap &VarLocIDs,
1757 TransferMap &Transfers) {
1758 MachineFunction *MF = MI.getMF();
1759 TransferKind TKind;
1760 Register Reg;
1761 std::optional<VarLoc::SpillLoc> Loc;
1762
1763 LLVM_DEBUG(dbgs() << "Examining instruction: "; MI.dump(););
1764
1765 // First, if there are any DBG_VALUEs pointing at a spill slot that is
1766 // written to, then close the variable location. The value in memory
1767 // will have changed.
1768 VarLocsInRange KillSet;
1769 if (isSpillInstruction(MI, MF)) {
1770 Loc = extractSpillBaseRegAndOffset(MI);
1771 for (uint64_t ID : OpenRanges.getSpillVarLocs()) {
1772 LocIndex Idx = LocIndex::fromRawInteger(ID);
1773 const VarLoc &VL = VarLocIDs[Idx];
1774 assert(VL.containsSpillLocs() && "Broken VarLocSet?");
1775 if (VL.usesSpillLoc(SpillLocation: *Loc)) {
1776 // This location is overwritten by the current instruction -- terminate
1777 // the open range, and insert an explicit DBG_VALUE $noreg.
1778 //
1779 // Doing this at a later stage would require re-interpreting all
1780 // DBG_VALUes and DIExpressions to identify whether they point at
1781 // memory, and then analysing all memory writes to see if they
1782 // overwrite that memory, which is expensive.
1783 //
1784 // At this stage, we already know which DBG_VALUEs are for spills and
1785 // where they are located; it's best to fix handle overwrites now.
1786 KillSet.insert(V: ID);
1787 unsigned SpillLocIdx = VL.getSpillLocIdx(SpillLocation: *Loc);
1788 VarLoc::MachineLoc OldLoc = VL.Locs[SpillLocIdx];
1789 VarLoc UndefVL = VarLoc::CreateCopyLoc(OldVL: VL, OldML: OldLoc, NewReg: 0);
1790 LocIndices UndefLocIDs = VarLocIDs.insert(VL: UndefVL);
1791 Transfers.push_back(Elt: {.TransferInst: &MI, .LocationID: UndefLocIDs.back()});
1792 }
1793 }
1794 OpenRanges.erase(KillSet, VarLocIDs, Location: LocIndex::kSpillLocation);
1795 }
1796
1797 // Try to recognise spill and restore instructions that may create a new
1798 // variable location.
1799 if (isLocationSpill(MI, MF, Reg)) {
1800 TKind = TransferKind::TransferSpill;
1801 LLVM_DEBUG(dbgs() << "Recognized as spill: "; MI.dump(););
1802 LLVM_DEBUG(dbgs() << "Register: " << Reg.id() << " " << printReg(Reg, TRI)
1803 << "\n");
1804 } else {
1805 if (!(Loc = isRestoreInstruction(MI, MF, Reg)))
1806 return;
1807 TKind = TransferKind::TransferRestore;
1808 LLVM_DEBUG(dbgs() << "Recognized as restore: "; MI.dump(););
1809 LLVM_DEBUG(dbgs() << "Register: " << Reg.id() << " " << printReg(Reg, TRI)
1810 << "\n");
1811 }
1812 // Check if the register or spill location is the location of a debug value.
1813 auto TransferCandidates = OpenRanges.getEmptyVarLocRange();
1814 if (TKind == TransferKind::TransferSpill)
1815 TransferCandidates = OpenRanges.getRegisterVarLocs(Reg);
1816 else if (TKind == TransferKind::TransferRestore)
1817 TransferCandidates = OpenRanges.getSpillVarLocs();
1818 for (uint64_t ID : TransferCandidates) {
1819 LocIndex Idx = LocIndex::fromRawInteger(ID);
1820 const VarLoc &VL = VarLocIDs[Idx];
1821 unsigned LocIdx;
1822 if (TKind == TransferKind::TransferSpill) {
1823 assert(VL.usesReg(Reg) && "Broken VarLocSet?");
1824 LLVM_DEBUG(dbgs() << "Spilling Register " << printReg(Reg, TRI) << '('
1825 << VL.Var.getVariable()->getName() << ")\n");
1826 LocIdx = VL.getRegIdx(Reg);
1827 } else {
1828 assert(TKind == TransferKind::TransferRestore && VL.containsSpillLocs() &&
1829 "Broken VarLocSet?");
1830 if (!VL.usesSpillLoc(SpillLocation: *Loc))
1831 // The spill location is not the location of a debug value.
1832 continue;
1833 LLVM_DEBUG(dbgs() << "Restoring Register " << printReg(Reg, TRI) << '('
1834 << VL.Var.getVariable()->getName() << ")\n");
1835 LocIdx = VL.getSpillLocIdx(SpillLocation: *Loc);
1836 }
1837 VarLoc::MachineLoc MLoc = VL.Locs[LocIdx];
1838 insertTransferDebugPair(MI, OpenRanges, Transfers, VarLocIDs, OldVarID: Idx, Kind: TKind,
1839 OldLoc: MLoc, NewReg: Reg);
1840 // FIXME: A comment should explain why it's correct to return early here,
1841 // if that is in fact correct.
1842 return;
1843 }
1844}
1845
1846/// If \p MI is a register copy instruction, that copies a previously tracked
1847/// value from one register to another register that is callee saved, we
1848/// create new DBG_VALUE instruction described with copy destination register.
1849void VarLocBasedLDV::transferRegisterCopy(MachineInstr &MI,
1850 OpenRangesSet &OpenRanges,
1851 VarLocMap &VarLocIDs,
1852 TransferMap &Transfers) {
1853 auto DestSrc = TII->isCopyLikeInstr(MI);
1854 if (!DestSrc)
1855 return;
1856
1857 const MachineOperand *DestRegOp = DestSrc->Destination;
1858 const MachineOperand *SrcRegOp = DestSrc->Source;
1859
1860 if (!DestRegOp->isDef())
1861 return;
1862
1863 auto isCalleeSavedReg = [&](Register Reg) {
1864 for (MCRegAliasIterator RAI(Reg, TRI, true); RAI.isValid(); ++RAI)
1865 if (CalleeSavedRegs.test(Idx: (*RAI).id()))
1866 return true;
1867 return false;
1868 };
1869
1870 Register SrcReg = SrcRegOp->getReg();
1871 Register DestReg = DestRegOp->getReg();
1872
1873 // We want to recognize instructions where destination register is callee
1874 // saved register. If register that could be clobbered by the call is
1875 // included, there would be a great chance that it is going to be clobbered
1876 // soon. It is more likely that previous register location, which is callee
1877 // saved, is going to stay unclobbered longer, even if it is killed.
1878 if (!isCalleeSavedReg(DestReg))
1879 return;
1880
1881 // Remember an entry value movement. If we encounter a new debug value of
1882 // a parameter describing only a moving of the value around, rather then
1883 // modifying it, we are still able to use the entry value if needed.
1884 if (isRegOtherThanSPAndFP(Op: *DestRegOp, MI, TRI)) {
1885 for (uint64_t ID : OpenRanges.getEntryValueBackupVarLocs()) {
1886 LocIndex Idx = LocIndex::fromRawInteger(ID);
1887 const VarLoc &VL = VarLocIDs[Idx];
1888 if (VL.isEntryValueBackupReg(Reg: SrcReg)) {
1889 LLVM_DEBUG(dbgs() << "Copy of the entry value: "; MI.dump(););
1890 VarLoc EntryValLocCopyBackup =
1891 VarLoc::CreateEntryCopyBackupLoc(MI: VL.MI, EntryExpr: VL.Expr, NewReg: DestReg);
1892 // Stop tracking the original entry value.
1893 OpenRanges.erase(VL);
1894
1895 // Start tracking the entry value copy.
1896 LocIndices EntryValCopyLocIDs = VarLocIDs.insert(VL: EntryValLocCopyBackup);
1897 OpenRanges.insert(VarLocIDs: EntryValCopyLocIDs, VL: EntryValLocCopyBackup);
1898 break;
1899 }
1900 }
1901 }
1902
1903 if (!SrcRegOp->isKill())
1904 return;
1905
1906 for (uint64_t ID : OpenRanges.getRegisterVarLocs(Reg: SrcReg)) {
1907 LocIndex Idx = LocIndex::fromRawInteger(ID);
1908 assert(VarLocIDs[Idx].usesReg(SrcReg) && "Broken VarLocSet?");
1909 VarLoc::MachineLocValue Loc;
1910 Loc.RegNo = SrcReg;
1911 VarLoc::MachineLoc MLoc{.Kind: VarLoc::MachineLocKind::RegisterKind, .Value: Loc};
1912 insertTransferDebugPair(MI, OpenRanges, Transfers, VarLocIDs, OldVarID: Idx,
1913 Kind: TransferKind::TransferCopy, OldLoc: MLoc, NewReg: DestReg);
1914 // FIXME: A comment should explain why it's correct to return early here,
1915 // if that is in fact correct.
1916 return;
1917 }
1918}
1919
1920/// Terminate all open ranges at the end of the current basic block.
1921bool VarLocBasedLDV::transferTerminator(MachineBasicBlock *CurMBB,
1922 OpenRangesSet &OpenRanges,
1923 VarLocInMBB &OutLocs,
1924 const VarLocMap &VarLocIDs) {
1925 bool Changed = false;
1926 LLVM_DEBUG({
1927 VarVec VarLocs;
1928 OpenRanges.getUniqueVarLocs(VarLocs, VarLocIDs);
1929 for (VarLoc &VL : VarLocs) {
1930 // Copy OpenRanges to OutLocs, if not already present.
1931 dbgs() << "Add to OutLocs in MBB #" << CurMBB->getNumber() << ": ";
1932 VL.dump(TRI, TII);
1933 }
1934 });
1935 VarLocSet &VLS = getVarLocsInMBB(MBB: CurMBB, Locs&: OutLocs);
1936 Changed = VLS != OpenRanges.getVarLocs();
1937 // New OutLocs set may be different due to spill, restore or register
1938 // copy instruction processing.
1939 if (Changed)
1940 VLS = OpenRanges.getVarLocs();
1941 OpenRanges.clear();
1942 return Changed;
1943}
1944
1945/// Accumulate a mapping between each DILocalVariable fragment and other
1946/// fragments of that DILocalVariable which overlap. This reduces work during
1947/// the data-flow stage from "Find any overlapping fragments" to "Check if the
1948/// known-to-overlap fragments are present".
1949/// \param MI A previously unprocessed DEBUG_VALUE instruction to analyze for
1950/// fragment usage.
1951/// \param SeenFragments Map from DILocalVariable to all fragments of that
1952/// Variable which are known to exist.
1953/// \param OverlappingFragments The overlap map being constructed, from one
1954/// Var/Fragment pair to a vector of fragments known to overlap.
1955void VarLocBasedLDV::accumulateFragmentMap(MachineInstr &MI,
1956 VarToFragments &SeenFragments,
1957 OverlapMap &OverlappingFragments) {
1958 DebugVariable MIVar(MI.getDebugVariable(), MI.getDebugExpression(),
1959 MI.getDebugLoc()->getInlinedAt());
1960 FragmentInfo ThisFragment = MIVar.getFragmentOrDefault();
1961
1962 // If this is the first sighting of this variable, then we are guaranteed
1963 // there are currently no overlapping fragments either. Initialize the set
1964 // of seen fragments, record no overlaps for the current one, and return.
1965 auto [SeenIt, Inserted] = SeenFragments.try_emplace(Key: MIVar.getVariable());
1966 if (Inserted) {
1967 SeenIt->second.insert(V: ThisFragment);
1968
1969 OverlappingFragments.insert(KV: {{MIVar.getVariable(), ThisFragment}, {}});
1970 return;
1971 }
1972
1973 // If this particular Variable/Fragment pair already exists in the overlap
1974 // map, it has already been accounted for.
1975 auto IsInOLapMap =
1976 OverlappingFragments.insert(KV: {{MIVar.getVariable(), ThisFragment}, {}});
1977 if (!IsInOLapMap.second)
1978 return;
1979
1980 auto &ThisFragmentsOverlaps = IsInOLapMap.first->second;
1981 auto &AllSeenFragments = SeenIt->second;
1982
1983 // Otherwise, examine all other seen fragments for this variable, with "this"
1984 // fragment being a previously unseen fragment. Record any pair of
1985 // overlapping fragments.
1986 for (const auto &ASeenFragment : AllSeenFragments) {
1987 // Does this previously seen fragment overlap?
1988 if (DIExpression::fragmentsOverlap(A: ThisFragment, B: ASeenFragment)) {
1989 // Yes: Mark the current fragment as being overlapped.
1990 ThisFragmentsOverlaps.push_back(Elt: ASeenFragment);
1991 // Mark the previously seen fragment as being overlapped by the current
1992 // one.
1993 auto ASeenFragmentsOverlaps =
1994 OverlappingFragments.find(Val: {MIVar.getVariable(), ASeenFragment});
1995 assert(ASeenFragmentsOverlaps != OverlappingFragments.end() &&
1996 "Previously seen var fragment has no vector of overlaps");
1997 ASeenFragmentsOverlaps->second.push_back(Elt: ThisFragment);
1998 }
1999 }
2000
2001 AllSeenFragments.insert(V: ThisFragment);
2002}
2003
2004/// This routine creates OpenRanges.
2005void VarLocBasedLDV::process(MachineInstr &MI, OpenRangesSet &OpenRanges,
2006 VarLocMap &VarLocIDs, TransferMap &Transfers,
2007 InstToEntryLocMap &EntryValTransfers,
2008 RegDefToInstMap &RegSetInstrs) {
2009 if (!MI.isDebugInstr())
2010 LastNonDbgMI = &MI;
2011 transferDebugValue(MI, OpenRanges, VarLocIDs, EntryValTransfers,
2012 RegSetInstrs);
2013 transferRegisterDef(MI, OpenRanges, VarLocIDs, EntryValTransfers,
2014 RegSetInstrs);
2015 transferWasmDef(MI, OpenRanges, VarLocIDs);
2016 transferRegisterCopy(MI, OpenRanges, VarLocIDs, Transfers);
2017 transferSpillOrRestoreInst(MI, OpenRanges, VarLocIDs, Transfers);
2018}
2019
2020/// This routine joins the analysis results of all incoming edges in @MBB by
2021/// inserting a new DBG_VALUE instruction at the start of the @MBB - if the same
2022/// source variable in all the predecessors of @MBB reside in the same location.
2023bool VarLocBasedLDV::join(
2024 MachineBasicBlock &MBB, VarLocInMBB &OutLocs, VarLocInMBB &InLocs,
2025 const VarLocMap &VarLocIDs,
2026 SmallPtrSet<const MachineBasicBlock *, 16> &Visited,
2027 SmallPtrSetImpl<const MachineBasicBlock *> &ArtificialBlocks) {
2028 LLVM_DEBUG(dbgs() << "join MBB: " << MBB.getNumber() << "\n");
2029
2030 VarLocSet InLocsT(Alloc); // Temporary incoming locations.
2031
2032 // For all predecessors of this MBB, find the set of VarLocs that
2033 // can be joined.
2034 int NumVisited = 0;
2035 for (auto *p : MBB.predecessors()) {
2036 // Ignore backedges if we have not visited the predecessor yet. As the
2037 // predecessor hasn't yet had locations propagated into it, most locations
2038 // will not yet be valid, so treat them as all being uninitialized and
2039 // potentially valid. If a location guessed to be correct here is
2040 // invalidated later, we will remove it when we revisit this block.
2041 if (!Visited.count(Ptr: p)) {
2042 LLVM_DEBUG(dbgs() << " ignoring unvisited pred MBB: " << p->getNumber()
2043 << "\n");
2044 continue;
2045 }
2046 auto OL = OutLocs.find(Val: p);
2047 // Join is null in case of empty OutLocs from any of the pred.
2048 if (OL == OutLocs.end())
2049 return false;
2050
2051 // Just copy over the Out locs to incoming locs for the first visited
2052 // predecessor, and for all other predecessors join the Out locs.
2053 VarLocSet &OutLocVLS = *OL->second;
2054 if (!NumVisited)
2055 InLocsT = OutLocVLS;
2056 else
2057 InLocsT &= OutLocVLS;
2058
2059 LLVM_DEBUG({
2060 if (!InLocsT.empty()) {
2061 VarVec VarLocs;
2062 collectAllVarLocs(VarLocs, InLocsT, VarLocIDs);
2063 for (const VarLoc &VL : VarLocs)
2064 dbgs() << " gathered candidate incoming var: "
2065 << VL.Var.getVariable()->getName() << "\n";
2066 }
2067 });
2068
2069 NumVisited++;
2070 }
2071
2072 // Filter out DBG_VALUES that are out of scope.
2073 VarLocSet KillSet(Alloc);
2074 bool IsArtificial = ArtificialBlocks.count(Ptr: &MBB);
2075 if (!IsArtificial) {
2076 for (uint64_t ID : InLocsT) {
2077 LocIndex Idx = LocIndex::fromRawInteger(ID);
2078 if (!VarLocIDs[Idx].dominates(LS, MBB)) {
2079 KillSet.set(ID);
2080 LLVM_DEBUG({
2081 auto Name = VarLocIDs[Idx].Var.getVariable()->getName();
2082 dbgs() << " killing " << Name << ", it doesn't dominate MBB\n";
2083 });
2084 }
2085 }
2086 }
2087 InLocsT.intersectWithComplement(Other: KillSet);
2088
2089 // As we are processing blocks in reverse post-order we
2090 // should have processed at least one predecessor, unless it
2091 // is the entry block which has no predecessor.
2092 assert((NumVisited || MBB.pred_empty()) &&
2093 "Should have processed at least one predecessor");
2094
2095 VarLocSet &ILS = getVarLocsInMBB(MBB: &MBB, Locs&: InLocs);
2096 bool Changed = false;
2097 if (ILS != InLocsT) {
2098 ILS = InLocsT;
2099 Changed = true;
2100 }
2101
2102 return Changed;
2103}
2104
2105void VarLocBasedLDV::flushPendingLocs(VarLocInMBB &PendingInLocs,
2106 VarLocMap &VarLocIDs) {
2107 // PendingInLocs records all locations propagated into blocks, which have
2108 // not had DBG_VALUE insts created. Go through and create those insts now.
2109 for (auto &Iter : PendingInLocs) {
2110 // Map is keyed on a constant pointer, unwrap it so we can insert insts.
2111 auto &MBB = const_cast<MachineBasicBlock &>(*Iter.first);
2112 VarLocSet &Pending = *Iter.second;
2113
2114 SmallVector<VarLoc, 32> VarLocs;
2115 collectAllVarLocs(Collected&: VarLocs, CollectFrom: Pending, VarLocIDs);
2116
2117 for (VarLoc DiffIt : VarLocs) {
2118 // The ID location is live-in to MBB -- work out what kind of machine
2119 // location it is and create a DBG_VALUE.
2120 if (DiffIt.isEntryBackupLoc())
2121 continue;
2122 MachineInstr *MI = DiffIt.BuildDbgValue(MF&: *MBB.getParent());
2123 MBB.insert(I: MBB.instr_begin(), M: MI);
2124
2125 (void)MI;
2126 LLVM_DEBUG(dbgs() << "Inserted: "; MI->dump(););
2127 }
2128 }
2129}
2130
2131bool VarLocBasedLDV::isEntryValueCandidate(
2132 const MachineInstr &MI, const DefinedRegsSet &DefinedRegs) const {
2133 assert(MI.isDebugValue() && "This must be DBG_VALUE.");
2134
2135 // TODO: Add support for local variables that are expressed in terms of
2136 // parameters entry values.
2137 // TODO: Add support for modified arguments that can be expressed
2138 // by using its entry value.
2139 auto *DIVar = MI.getDebugVariable();
2140 if (!DIVar->isParameter())
2141 return false;
2142
2143 // Do not consider parameters that belong to an inlined function.
2144 if (MI.getDebugLoc()->getInlinedAt())
2145 return false;
2146
2147 // Only consider parameters that are described using registers. Parameters
2148 // that are passed on the stack are not yet supported, so ignore debug
2149 // values that are described by the frame or stack pointer.
2150 if (!isRegOtherThanSPAndFP(Op: MI.getDebugOperand(Index: 0), MI, TRI))
2151 return false;
2152
2153 // If a parameter's value has been propagated from the caller, then the
2154 // parameter's DBG_VALUE may be described using a register defined by some
2155 // instruction in the entry block, in which case we shouldn't create an
2156 // entry value.
2157 if (DefinedRegs.count(V: MI.getDebugOperand(Index: 0).getReg()))
2158 return false;
2159
2160 // TODO: Add support for parameters that have a pre-existing debug expressions
2161 // (e.g. fragments).
2162 // A simple deref expression is equivalent to an indirect debug value.
2163 const DIExpression *Expr = MI.getDebugExpression();
2164 if (Expr->getNumElements() > 0 && !Expr->isDeref())
2165 return false;
2166
2167 return true;
2168}
2169
2170/// Collect all register defines (including aliases) for the given instruction.
2171static void collectRegDefs(const MachineInstr &MI, DefinedRegsSet &Regs,
2172 const TargetRegisterInfo *TRI) {
2173 for (const MachineOperand &MO : MI.all_defs()) {
2174 if (MO.getReg() && MO.getReg().isPhysical()) {
2175 Regs.insert(V: MO.getReg());
2176 for (MCRegAliasIterator AI(MO.getReg(), TRI, true); AI.isValid(); ++AI)
2177 Regs.insert(V: *AI);
2178 }
2179 }
2180}
2181
2182/// This routine records the entry values of function parameters. The values
2183/// could be used as backup values. If we loose the track of some unmodified
2184/// parameters, the backup values will be used as a primary locations.
2185void VarLocBasedLDV::recordEntryValue(const MachineInstr &MI,
2186 const DefinedRegsSet &DefinedRegs,
2187 OpenRangesSet &OpenRanges,
2188 VarLocMap &VarLocIDs) {
2189 if (!ShouldEmitDebugEntryValues)
2190 return;
2191
2192 DebugVariable V(MI.getDebugVariable(), MI.getDebugExpression(),
2193 MI.getDebugLoc()->getInlinedAt());
2194
2195 if (!isEntryValueCandidate(MI, DefinedRegs) ||
2196 OpenRanges.getEntryValueBackup(Var: V))
2197 return;
2198
2199 LLVM_DEBUG(dbgs() << "Creating the backup entry location: "; MI.dump(););
2200
2201 // Create the entry value and use it as a backup location until it is
2202 // valid. It is valid until a parameter is not changed.
2203 DIExpression *NewExpr =
2204 DIExpression::prepend(Expr: MI.getDebugExpression(), Flags: DIExpression::EntryValue);
2205 VarLoc EntryValLocAsBackup = VarLoc::CreateEntryBackupLoc(MI, EntryExpr: NewExpr);
2206 LocIndices EntryValLocIDs = VarLocIDs.insert(VL: EntryValLocAsBackup);
2207 OpenRanges.insert(VarLocIDs: EntryValLocIDs, VL: EntryValLocAsBackup);
2208}
2209
2210/// Calculate the liveness information for the given machine function and
2211/// extend ranges across basic blocks.
2212bool VarLocBasedLDV::ExtendRanges(MachineFunction &MF,
2213 MachineDominatorTree *DomTree,
2214 bool ShouldEmitDebugEntryValues,
2215 unsigned InputBBLimit,
2216 unsigned InputDbgValLimit) {
2217 (void)DomTree;
2218 LLVM_DEBUG(dbgs() << "\nDebug Range Extension: " << MF.getName() << "\n");
2219
2220 if (!MF.getFunction().getSubprogram())
2221 // VarLocBaseLDV will already have removed all DBG_VALUEs.
2222 return false;
2223
2224 // Skip functions from NoDebug compilation units.
2225 if (MF.getFunction().getSubprogram()->getUnit()->getEmissionKind() ==
2226 DICompileUnit::NoDebug)
2227 return false;
2228
2229 TRI = MF.getSubtarget().getRegisterInfo();
2230 TII = MF.getSubtarget().getInstrInfo();
2231 TFI = MF.getSubtarget().getFrameLowering();
2232 TFI->getCalleeSaves(MF, SavedRegs&: CalleeSavedRegs);
2233 this->ShouldEmitDebugEntryValues = ShouldEmitDebugEntryValues;
2234
2235 LS.scanFunction(MF);
2236
2237 bool Changed = false;
2238 bool OLChanged = false;
2239 bool MBBJoined = false;
2240
2241 VarLocMap VarLocIDs; // Map VarLoc<>unique ID for use in bitvectors.
2242 OverlapMap OverlapFragments; // Map of overlapping variable fragments.
2243 OpenRangesSet OpenRanges(Alloc, OverlapFragments);
2244 // Ranges that are open until end of bb.
2245 VarLocInMBB OutLocs; // Ranges that exist beyond bb.
2246 VarLocInMBB InLocs; // Ranges that are incoming after joining.
2247 TransferMap Transfers; // DBG_VALUEs associated with transfers (such as
2248 // spills, copies and restores).
2249 // Map responsible MI to attached Transfer emitted from Backup Entry Value.
2250 InstToEntryLocMap EntryValTransfers;
2251 // Map a Register to the last MI which clobbered it.
2252 RegDefToInstMap RegSetInstrs;
2253
2254 VarToFragments SeenFragments;
2255
2256 // Blocks which are artificial, i.e. blocks which exclusively contain
2257 // instructions without locations, or with line 0 locations.
2258 SmallPtrSet<const MachineBasicBlock *, 16> ArtificialBlocks;
2259
2260 DenseMap<unsigned int, MachineBasicBlock *> OrderToBB;
2261 DenseMap<MachineBasicBlock *, unsigned int> BBToOrder;
2262 std::priority_queue<unsigned int, std::vector<unsigned int>,
2263 std::greater<unsigned int>>
2264 Worklist;
2265 std::priority_queue<unsigned int, std::vector<unsigned int>,
2266 std::greater<unsigned int>>
2267 Pending;
2268
2269 // Set of register defines that are seen when traversing the entry block
2270 // looking for debug entry value candidates.
2271 DefinedRegsSet DefinedRegs;
2272
2273 // Only in the case of entry MBB collect DBG_VALUEs representing
2274 // function parameters in order to generate debug entry values for them.
2275 MachineBasicBlock &First_MBB = *(MF.begin());
2276 for (auto &MI : First_MBB) {
2277 collectRegDefs(MI, Regs&: DefinedRegs, TRI);
2278 if (MI.isDebugValue())
2279 recordEntryValue(MI, DefinedRegs, OpenRanges, VarLocIDs);
2280 }
2281
2282 // Initialize per-block structures and scan for fragment overlaps.
2283 for (auto &MBB : MF)
2284 for (auto &MI : MBB)
2285 if (MI.isDebugValue())
2286 accumulateFragmentMap(MI, SeenFragments, OverlappingFragments&: OverlapFragments);
2287
2288 auto hasNonArtificialLocation = [](const MachineInstr &MI) -> bool {
2289 if (const DebugLoc &DL = MI.getDebugLoc())
2290 return DL.getLine() != 0;
2291 return false;
2292 };
2293 for (auto &MBB : MF)
2294 if (none_of(Range: MBB.instrs(), P: hasNonArtificialLocation))
2295 ArtificialBlocks.insert(Ptr: &MBB);
2296
2297 LLVM_DEBUG(printVarLocInMBB(MF, OutLocs, VarLocIDs,
2298 "OutLocs after initialization", dbgs()));
2299
2300 ReversePostOrderTraversal<MachineFunction *> RPOT(&MF);
2301 unsigned int RPONumber = 0;
2302 for (MachineBasicBlock *MBB : RPOT) {
2303 OrderToBB[RPONumber] = MBB;
2304 BBToOrder[MBB] = RPONumber;
2305 Worklist.push(x: RPONumber);
2306 ++RPONumber;
2307 }
2308
2309 if (RPONumber > InputBBLimit) {
2310 unsigned NumInputDbgValues = 0;
2311 for (auto &MBB : MF)
2312 for (auto &MI : MBB)
2313 if (MI.isDebugValue())
2314 ++NumInputDbgValues;
2315 if (NumInputDbgValues > InputDbgValLimit) {
2316 LLVM_DEBUG(dbgs() << "Disabling VarLocBasedLDV: " << MF.getName()
2317 << " has " << RPONumber << " basic blocks and "
2318 << NumInputDbgValues
2319 << " input DBG_VALUEs, exceeding limits.\n");
2320 return false;
2321 }
2322 }
2323
2324 // This is a standard "union of predecessor outs" dataflow problem.
2325 // To solve it, we perform join() and process() using the two worklist method
2326 // until the ranges converge.
2327 // Ranges have converged when both worklists are empty.
2328 SmallPtrSet<const MachineBasicBlock *, 16> Visited;
2329 while (!Worklist.empty() || !Pending.empty()) {
2330 // We track what is on the pending worklist to avoid inserting the same
2331 // thing twice. We could avoid this with a custom priority queue, but this
2332 // is probably not worth it.
2333 SmallPtrSet<MachineBasicBlock *, 16> OnPending;
2334 LLVM_DEBUG(dbgs() << "Processing Worklist\n");
2335 while (!Worklist.empty()) {
2336 MachineBasicBlock *MBB = OrderToBB[Worklist.top()];
2337 Worklist.pop();
2338 MBBJoined = join(MBB&: *MBB, OutLocs, InLocs, VarLocIDs, Visited,
2339 ArtificialBlocks);
2340 MBBJoined |= Visited.insert(Ptr: MBB).second;
2341 if (MBBJoined) {
2342 MBBJoined = false;
2343 Changed = true;
2344 // Now that we have started to extend ranges across BBs we need to
2345 // examine spill, copy and restore instructions to see whether they
2346 // operate with registers that correspond to user variables.
2347 // First load any pending inlocs.
2348 OpenRanges.insertFromLocSet(ToLoad: getVarLocsInMBB(MBB, Locs&: InLocs), Map: VarLocIDs);
2349 LastNonDbgMI = nullptr;
2350 RegSetInstrs.clear();
2351 // Iterate through instructions within each packet to handle VLIW
2352 // bundles correctly; this keeps DBG_VALUE placement valid on
2353 // packet-based targets.
2354 for (auto I = MBB->instr_begin(), E = MBB->instr_end(); I != E;) {
2355 auto BStart = llvm::getBundleStart(I);
2356 auto BEnd = llvm::getBundleEnd(I);
2357 bool PacketHasTerminator = false;
2358 for (auto BI = BStart; BI != BEnd; ++BI) {
2359 if (BI->isTerminator()) {
2360 PacketHasTerminator = true;
2361 break;
2362 }
2363 }
2364 if (PacketHasTerminator) {
2365 // FIXME: This drops debug info for spills in terminator bundles;
2366 // DBG_VALUE instructions can't be inserted after the bundle.
2367 // It may be possible to insert the DBG_VALUE elsewhere.
2368 I = BEnd;
2369 continue;
2370 }
2371 auto FirstOp = (BStart->isBundle()) ? std::next(x: BStart) : BStart;
2372 for (auto BI = FirstOp; BI != BEnd; ++BI) {
2373 if (BI->isTerminator())
2374 continue;
2375 process(MI&: *BI, OpenRanges, VarLocIDs, Transfers, EntryValTransfers,
2376 RegSetInstrs);
2377 }
2378 I = BEnd;
2379 }
2380 OLChanged |= transferTerminator(CurMBB: MBB, OpenRanges, OutLocs, VarLocIDs);
2381
2382 LLVM_DEBUG(printVarLocInMBB(MF, OutLocs, VarLocIDs,
2383 "OutLocs after propagating", dbgs()));
2384 LLVM_DEBUG(printVarLocInMBB(MF, InLocs, VarLocIDs,
2385 "InLocs after propagating", dbgs()));
2386
2387 if (OLChanged) {
2388 OLChanged = false;
2389 for (auto *s : MBB->successors())
2390 if (OnPending.insert(Ptr: s).second) {
2391 Pending.push(x: BBToOrder[s]);
2392 }
2393 }
2394 }
2395 }
2396 Worklist.swap(pq&: Pending);
2397 // At this point, pending must be empty, since it was just the empty
2398 // worklist
2399 assert(Pending.empty() && "Pending should be empty");
2400 }
2401
2402 // Add any DBG_VALUE instructions created by location transfers.
2403 for (auto &TR : Transfers) {
2404 assert(!TR.TransferInst->isTerminator() &&
2405 "Cannot insert DBG_VALUE after terminator");
2406 MachineBasicBlock *MBB = TR.TransferInst->getParent();
2407 const VarLoc &VL = VarLocIDs[TR.LocationID];
2408 MachineInstr *MI = VL.BuildDbgValue(MF);
2409 MBB->insertAfterBundle(I: TR.TransferInst->getIterator(), MI);
2410 }
2411 Transfers.clear();
2412
2413 // Add DBG_VALUEs created using Backup Entry Value location.
2414 for (auto &TR : EntryValTransfers) {
2415 MachineInstr *TRInst = const_cast<MachineInstr *>(TR.first);
2416 assert(!TRInst->isTerminator() &&
2417 "Cannot insert DBG_VALUE after terminator");
2418 MachineBasicBlock *MBB = TRInst->getParent();
2419 const VarLoc &VL = VarLocIDs[TR.second];
2420 MachineInstr *MI = VL.BuildDbgValue(MF);
2421 MBB->insertAfterBundle(I: TRInst->getIterator(), MI);
2422 }
2423 EntryValTransfers.clear();
2424
2425 // Deferred inlocs will not have had any DBG_VALUE insts created; do
2426 // that now.
2427 flushPendingLocs(PendingInLocs&: InLocs, VarLocIDs);
2428
2429 LLVM_DEBUG(printVarLocInMBB(MF, OutLocs, VarLocIDs, "Final OutLocs", dbgs()));
2430 LLVM_DEBUG(printVarLocInMBB(MF, InLocs, VarLocIDs, "Final InLocs", dbgs()));
2431 return Changed;
2432}
2433
2434LDVImpl *
2435llvm::makeVarLocBasedLiveDebugValues()
2436{
2437 return new VarLocBasedLDV();
2438}
2439