1//===-- VPlanVerifier.cpp -------------------------------------------------===//
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
10/// This file defines the class VPlanVerifier, which contains utility functions
11/// to check the consistency and invariants of a VPlan.
12///
13//===----------------------------------------------------------------------===//
14
15#include "VPlanVerifier.h"
16#include "VPlan.h"
17#include "VPlanCFG.h"
18#include "VPlanDominatorTree.h"
19#include "VPlanHelpers.h"
20#include "VPlanPatternMatch.h"
21#include "VPlanUtils.h"
22#include "llvm/ADT/SmallPtrSet.h"
23
24#define DEBUG_TYPE "loop-vectorize"
25
26using namespace llvm;
27using namespace VPlanPatternMatch;
28
29namespace {
30class VPlanVerifier {
31 const VPDominatorTree &VPDT;
32
33 SmallPtrSet<BasicBlock *, 8> WrappedIRBBs;
34
35 // Verify that phi-like recipes are at the beginning of \p VPBB, with no
36 // other recipes in between. Also check that only header blocks contain
37 // VPHeaderPHIRecipes.
38 bool verifyPhiRecipes(const VPBasicBlock *VPBB);
39
40 /// Verify that \p LastActiveLane's operand is guaranteed to be a prefix-mask.
41 bool verifyLastActiveLaneRecipe(const VPInstruction &LastActiveLane) const;
42
43 bool verifyVPBasicBlock(const VPBasicBlock *VPBB);
44
45 bool verifyBlock(const VPBlockBase *VPB);
46
47 /// Helper function that verifies the CFG invariants of the VPBlockBases
48 /// within
49 /// \p Region. Checks in this function are generic for VPBlockBases. They are
50 /// not specific for VPBasicBlocks or VPRegionBlocks.
51 bool verifyBlocksInRegion(const VPRegionBlock *Region);
52
53 /// Verify the CFG invariants of VPRegionBlock \p Region and its nested
54 /// VPBlockBases. Do not recurse inside nested VPRegionBlocks.
55 bool verifyRegion(const VPRegionBlock *Region);
56
57 /// Verify the CFG invariants of VPRegionBlock \p Region and its nested
58 /// VPBlockBases. Recurse inside nested VPRegionBlocks.
59 bool verifyRegionRec(const VPRegionBlock *Region);
60
61public:
62 VPlanVerifier(VPDominatorTree &VPDT) : VPDT(VPDT) {}
63
64 bool verify(const VPlan &Plan);
65};
66} // namespace
67
68bool VPlanVerifier::verifyPhiRecipes(const VPBasicBlock *VPBB) {
69 auto RecipeI = VPBB->begin();
70 auto End = VPBB->end();
71 unsigned NumActiveLaneMaskPhiRecipes = 0;
72 bool IsHeaderVPBB = VPBlockUtils::isHeader(VPB: VPBB, VPDT);
73 while (RecipeI != End && RecipeI->isPhi()) {
74 if (isa<VPActiveLaneMaskPHIRecipe>(Val: RecipeI))
75 NumActiveLaneMaskPhiRecipes++;
76
77 if (IsHeaderVPBB &&
78 !isa<VPHeaderPHIRecipe, VPWidenPHIRecipe, VPPhi>(Val: *RecipeI)) {
79 errs() << "Found non-header PHI recipe in header VPBB";
80#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
81 errs() << ": ";
82 RecipeI->dump();
83#endif
84 return false;
85 }
86
87 if (!IsHeaderVPBB && isa<VPHeaderPHIRecipe>(Val: *RecipeI)) {
88 errs() << "Found header PHI recipe in non-header VPBB";
89#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
90 errs() << ": ";
91 RecipeI->dump();
92#endif
93 return false;
94 }
95
96 // In region form, VPCurrentIterationPHIRecipe must be the first header phi
97 // recipe. In a plain CFG VPlan, it must either be the first or second.
98 if (isa<VPCurrentIterationPHIRecipe>(Val: RecipeI) &&
99 (VPBB->getPlan()->getVectorLoopRegion()
100 ? RecipeI->getIterator() != VPBB->begin()
101 : RecipeI->getIterator() != VPBB->begin() &&
102 RecipeI->getIterator() != std::next(x: VPBB->begin()))) {
103 errs() << "CurrentIteration PHI is not the first/second recipe\n";
104 return false;
105 }
106
107 // Check if the recipe operands match the number of predecessors.
108 // TODO Extend to other phi-like recipes.
109 if (auto *PhiIRI = dyn_cast<VPIRPhi>(Val: &*RecipeI)) {
110 if (PhiIRI->getNumOperands() != VPBB->getNumPredecessors()) {
111 errs() << "Phi-like recipe with different number of operands and "
112 "predecessors.\n";
113 // TODO: Print broken recipe. At the moment printing an ill-formed
114 // phi-like recipe may crash.
115 return false;
116 }
117 }
118
119 RecipeI++;
120 }
121
122 if (!VPBB->getPlan()->isUnrolled() && NumActiveLaneMaskPhiRecipes > 1) {
123 errs() << "There should be no more than one VPActiveLaneMaskPHIRecipe";
124 return false;
125 }
126
127 while (RecipeI != End) {
128 if (RecipeI->isPhi() && !isa<VPBlendRecipe>(Val: &*RecipeI)) {
129 errs() << "Found phi-like recipe after non-phi recipe";
130
131#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
132 errs() << ": ";
133 RecipeI->dump();
134 errs() << "after\n";
135 std::prev(RecipeI)->dump();
136#endif
137 return false;
138 }
139 RecipeI++;
140 }
141 return true;
142}
143
144static bool isKnownMonotonic(VPValue *V) {
145 VPValue *X, *Y;
146 if (match(V, P: m_Add(Op0: m_VPValue(V&: X), Op1: m_VPValue(V&: Y))))
147 return cast<VPRecipeWithIRFlags>(Val: V)->hasNoUnsignedWrap() &&
148 isKnownMonotonic(V: X) && isKnownMonotonic(V: Y);
149 if (match(V, P: m_StepVector()))
150 return true;
151 // Only handle a subset of IVs until we can guarantee there's no overflow.
152 if (auto *WidenIV = dyn_cast<VPWidenIntOrFpInductionRecipe>(Val: V))
153 return WidenIV->isCanonical() || WidenIV->hasNoUnsignedWrap();
154 if (auto *Steps = dyn_cast<VPScalarIVStepsRecipe>(Val: V))
155 return match(V: Steps->getOperand(N: 0),
156 P: m_CombineOr(
157 Ps: m_CanonicalIV(),
158 Ps: m_DerivedIV(Op0: m_ZeroInt(), Op1: m_CanonicalIV(), Op2: m_One()))) &&
159 match(V: Steps->getStepValue(), P: m_One());
160 if (isa<VPWidenCanonicalIVRecipe>(Val: V))
161 return true;
162 return vputils::isUniformAcrossVFsAndUFs(V);
163}
164
165bool VPlanVerifier::verifyLastActiveLaneRecipe(
166 const VPInstruction &LastActiveLane) const {
167 assert(LastActiveLane.getOpcode() == VPInstruction::LastActiveLane &&
168 "must be called with VPInstruction::LastActiveLane");
169
170 if (LastActiveLane.getNumOperands() < 1) {
171 errs() << "LastActiveLane must have at least one operand\n";
172 return false;
173 }
174
175 const VPlan &Plan = *LastActiveLane.getParent()->getPlan();
176 // All operands must be prefix-mask. This means an icmp ult/ule LHS, RHS where
177 // the LHS is monotonically increasing and RHS is uniform across VFs and UF.
178 for (VPValue *Op : LastActiveLane.operands()) {
179 VPValue *Mask = Op;
180 VPValue *HeaderMask;
181
182 // Look through any `and`s with a loop_dependence_war_mask, which is always
183 // a prefix mask. TODO: Verify the full loop.dependence.mask chain.
184 if (match(V: Op,
185 P: m_c_BinaryAnd(
186 Op0: m_VPValue(V&: HeaderMask),
187 Op1: m_CombineOr(
188 Ps: m_c_BinaryAnd(
189 Op0: m_Intrinsic<Intrinsic::loop_dependence_war_mask>(),
190 Op1: m_VPValue()),
191 Ps: m_Intrinsic<Intrinsic::loop_dependence_war_mask>()))))
192 Mask = HeaderMask;
193
194 if (vputils::isHeaderMask(V: Mask, Plan))
195 continue;
196
197 if (match(V: Mask, P: m_ActiveLaneMask(Op0: m_VPValue(), Op1: m_VPValue(), Op2: m_VPValue())))
198 continue;
199
200 CmpPredicate Pred;
201 VPValue *LHS, *RHS;
202 if (match(V: Mask, P: m_ICmp(Pred, Op0: m_VPValue(V&: LHS), Op1: m_VPValue(V&: RHS))) &&
203 (Pred == CmpInst::ICMP_ULE || Pred == CmpInst::ICMP_ULT) &&
204 isKnownMonotonic(V: LHS) &&
205 (vputils::isUniformAcrossVFsAndUFs(V: RHS) ||
206 match(V: RHS, P: m_EVL(Op0: m_VPValue()))))
207 continue;
208
209 errs() << "LastActiveLane operand ";
210#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
211 VPSlotTracker Tracker(&Plan);
212 Op->printAsOperand(errs(), Tracker);
213#endif
214 errs() << " must be prefix mask (a header mask or an "
215 "EVL-derived mask currently)\n";
216 return false;
217 }
218
219 return true;
220}
221
222bool VPlanVerifier::verifyVPBasicBlock(const VPBasicBlock *VPBB) {
223 if (!verifyPhiRecipes(VPBB))
224 return false;
225
226 // Verify that defs in VPBB dominate all their uses.
227 DenseMap<const VPRecipeBase *, unsigned> RecipeNumbering;
228 unsigned Cnt = 0;
229 for (const VPRecipeBase &R : *VPBB)
230 RecipeNumbering[&R] = Cnt++;
231
232 for (const VPRecipeBase &R : *VPBB) {
233 if (isa<VPIRInstruction>(Val: &R) && !isa<VPIRBasicBlock>(Val: VPBB)) {
234 errs() << "VPIRInstructions ";
235#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
236 R.dump();
237 errs() << " ";
238#endif
239 errs() << "not in a VPIRBasicBlock!\n";
240 return false;
241 }
242 for (const VPValue *V : R.definedValues()) {
243 // Verify that each defined value has a scalar type.
244 if (!V->getScalarType()) {
245 errs() << "VPValue without scalar type!\n";
246 return false;
247 }
248
249 // MaskedCond may be used from blocks it don't dominate; the block will be
250 // linearized and it will dominate its users after linearization.
251 if (match(V: &R, P: m_VPInstruction<VPInstruction::MaskedCond>()))
252 continue;
253
254 for (const VPUser *U : V->users()) {
255 auto *UI = cast<VPRecipeBase>(Val: U);
256 if (isa<VPIRPhi>(Val: UI) &&
257 UI->getNumOperands() != UI->getParent()->getNumPredecessors()) {
258 errs() << "Phi-like recipe with different number of operands and "
259 "predecessors.\n";
260 return false;
261 }
262
263 if (auto *Phi = dyn_cast<VPPhiAccessors>(Val: UI)) {
264 for (const auto &[IncomingVPV, IncomingVPBB] :
265 Phi->incoming_values_and_blocks()) {
266 if (IncomingVPV != V)
267 continue;
268
269 if (VPDT.dominates(A: VPBB, B: IncomingVPBB))
270 continue;
271
272 errs() << "Incoming def does not dominate incoming block!\n";
273#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
274 VPSlotTracker Tracker(VPBB->getPlan());
275 IncomingVPV->getDefiningRecipe()->print(errs(), " ", Tracker);
276 errs() << "\n does not dominate " << IncomingVPBB->getName()
277 << " for\n";
278 UI->print(errs(), " ", Tracker);
279#endif
280 return false;
281 }
282 continue;
283 }
284 // TODO: Also verify VPPredInstPHIRecipe.
285 if (isa<VPPredInstPHIRecipe>(Val: UI))
286 continue;
287
288 // If the user is in the same block, check it comes after R in the
289 // block.
290 if (UI->getParent() == VPBB) {
291 if (RecipeNumbering[UI] >= RecipeNumbering[&R])
292 continue;
293 } else {
294 if (VPDT.dominates(A: VPBB, B: UI->getParent()))
295 continue;
296 }
297
298 // Recipes in blocks with a MaskedCond may be used in exit blocks; the
299 // block will be linearized and its recipes will dominate their users
300 // after linearization.
301 bool BlockHasMaskedCond = any_of(Range: *VPBB, P: [](const VPRecipeBase &R) {
302 return match(V: &R, P: m_VPInstruction<VPInstruction::MaskedCond>());
303 });
304 if (BlockHasMaskedCond &&
305 any_of(Range: VPBB->getPlan()->getExitBlocks(), P: [UI](VPIRBasicBlock *EB) {
306 return is_contained(Range&: EB->getPredecessors(), Element: UI->getParent());
307 })) {
308 continue;
309 }
310
311 errs() << "Use before def!\n";
312#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
313 VPSlotTracker Tracker(VPBB->getPlan());
314 UI->print(errs(), " ", Tracker);
315 errs() << "\n before\n";
316 R.print(errs(), " ", Tracker);
317 errs() << "\n";
318#endif
319 return false;
320 }
321 }
322 if (const auto *VPI = dyn_cast<VPInstruction>(Val: &R)) {
323 switch (VPI->getOpcode()) {
324 case VPInstruction::LastActiveLane:
325 if (!verifyLastActiveLaneRecipe(LastActiveLane: *VPI))
326 return false;
327 break;
328 default:
329 break;
330 }
331 }
332 if (const auto *ScalarIVSteps = dyn_cast<VPScalarIVStepsRecipe>(Val: &R)) {
333 unsigned NumOps = ScalarIVSteps->getNumOperands();
334 if (NumOps != 3 && NumOps != 4) {
335 errs() << "VPScalarIVStepsRecipe must have 3 or 4 operands\n";
336 return false;
337 }
338 }
339 }
340
341 auto *IRBB = dyn_cast<VPIRBasicBlock>(Val: VPBB);
342 if (!IRBB)
343 return true;
344
345 if (!WrappedIRBBs.insert(Ptr: IRBB->getIRBasicBlock()).second) {
346 errs() << "Same IR basic block used by multiple wrapper blocks!\n";
347 return false;
348 }
349
350 return true;
351}
352
353bool VPlanVerifier::verifyBlock(const VPBlockBase *VPB) {
354 auto *VPBB = dyn_cast<VPBasicBlock>(Val: VPB);
355 // Check block's condition bit.
356 if (VPBB && !isa<VPIRBasicBlock>(Val: VPB)) {
357 // For plain CFG VPlans, verify header and latch block structure.
358 if (!VPBB->getParent()) {
359 if (VPBlockUtils::isHeader(VPB: VPBB, VPDT)) {
360 if (VPB->getNumPredecessors() != 2) {
361 errs()
362 << "Header block in plain CFG VPlan must have 2 predecessors!\n";
363 return false;
364 }
365 // Predecessor 0 is preheader, predecessor 1 is latch.
366 if (!VPBlockUtils::isLatch(VPB: VPB->getPredecessors()[1], VPDT)) {
367 errs() << "Header's second predecessor must be the latch!\n";
368 return false;
369 }
370 }
371
372 if (VPBlockUtils::isLatch(VPB: VPBB, VPDT)) {
373 auto BranchTerminator =
374 m_CombineOr(Ps: m_BranchOnCond(),
375 Ps: m_CombineOr(Ps: m_BranchOnCount(), Ps: m_BranchOnTwoConds()));
376 if (!match(V: VPBB->getTerminator(), P: BranchTerminator)) {
377 errs() << "Latch block must have a branch terminator!\n";
378 return false;
379 }
380 // Successor 0 is middle block, successor 1 is header.
381 if (VPBlockUtils::isHeader(VPB: VPB->getSuccessors()[0], VPDT)) {
382 errs() << "Latch's first successor must not be the header (must be "
383 "middle block)!\n";
384 return false;
385 }
386 }
387 } else if (VPB->getNumSuccessors() > 1 ||
388 (VPBB->isExiting() && !VPBB->getParent()->isReplicator())) {
389 if (!VPBB->getTerminator()) {
390 errs() << "Block has multiple successors but doesn't "
391 "have a proper branch recipe!\n";
392 return false;
393 }
394 } else if (VPBB->getTerminator()) {
395 errs() << "Unexpected branch recipe!\n";
396 return false;
397 }
398 }
399
400 // Check block's successors.
401 const auto &Successors = VPB->getSuccessors();
402 for (const VPBlockBase *Succ : Successors) {
403 // There must be a bi-directional link between block and successor.
404 const auto &SuccPreds = Succ->getPredecessors();
405 if (!is_contained(Range: SuccPreds, Element: VPB)) {
406 errs() << "Missing predecessor link.\n";
407 return false;
408 }
409 }
410
411 // Check block's predecessors.
412 const auto &Predecessors = VPB->getPredecessors();
413
414 for (const VPBlockBase *Pred : Predecessors) {
415 // Block and predecessor must be inside the same region.
416 if (Pred->getParent() != VPB->getParent()) {
417 errs() << "Predecessor is not in the same region.\n";
418 return false;
419 }
420
421 // There must be a bi-directional link between block and predecessor.
422 const auto &PredSuccs = Pred->getSuccessors();
423 if (!is_contained(Range: PredSuccs, Element: VPB)) {
424 errs() << "Missing successor link.\n";
425 return false;
426 }
427 }
428 return !VPBB || verifyVPBasicBlock(VPBB);
429}
430
431bool VPlanVerifier::verifyBlocksInRegion(const VPRegionBlock *Region) {
432 for (const VPBlockBase *VPB : vp_depth_first_shallow(G: Region->getEntry())) {
433 // Check block's parent.
434 if (VPB->getParent() != Region) {
435 errs() << "VPBlockBase has wrong parent\n";
436 return false;
437 }
438
439 if (!verifyBlock(VPB))
440 return false;
441 }
442 return true;
443}
444
445bool VPlanVerifier::verifyRegion(const VPRegionBlock *Region) {
446 const VPBlockBase *Entry = Region->getEntry();
447 const VPBlockBase *Exiting = Region->getExiting();
448
449 // Entry and Exiting shouldn't have any predecessor/successor, respectively.
450 if (Entry->hasPredecessors()) {
451 errs() << "region entry block has predecessors\n";
452 return false;
453 }
454 if (Exiting->getNumSuccessors() != 0) {
455 errs() << "region exiting block has successors\n";
456 return false;
457 }
458
459 return verifyBlocksInRegion(Region);
460}
461
462bool VPlanVerifier::verifyRegionRec(const VPRegionBlock *Region) {
463 // Recurse inside nested regions and check all blocks inside the region.
464 return verifyRegion(Region) &&
465 all_of(Range: vp_depth_first_shallow(G: Region->getEntry()),
466 P: [this](const VPBlockBase *VPB) {
467 const auto *SubRegion = dyn_cast<VPRegionBlock>(Val: VPB);
468 return !SubRegion || verifyRegionRec(Region: SubRegion);
469 });
470}
471
472bool VPlanVerifier::verify(const VPlan &Plan) {
473 if (any_of(Range: vp_depth_first_shallow(G: Plan.getEntry()),
474 P: [this](const VPBlockBase *VPB) { return !verifyBlock(VPB); }))
475 return false;
476
477 const VPRegionBlock *TopRegion = Plan.getVectorLoopRegion();
478 // TODO: Verify all blocks using vp_depth_first_deep iterators.
479 if (!TopRegion)
480 return true;
481
482 if (!verifyRegionRec(Region: TopRegion))
483 return false;
484
485 if (TopRegion->getParent()) {
486 errs() << "VPlan Top Region should have no parent.\n";
487 return false;
488 }
489
490 const VPBasicBlock *Entry = dyn_cast<VPBasicBlock>(Val: TopRegion->getEntry());
491 if (!Entry) {
492 errs() << "VPlan entry block is not a VPBasicBlock\n";
493 return false;
494 }
495
496 const VPBasicBlock *Exiting = dyn_cast<VPBasicBlock>(Val: TopRegion->getExiting());
497 if (!Exiting) {
498 errs() << "VPlan exiting block is not a VPBasicBlock\n";
499 return false;
500 }
501
502 if (Exiting->empty()) {
503 errs() << "VPlan vector loop exiting block must end with BranchOnCount, "
504 "BranchOnCond, or BranchOnTwoConds VPInstruction but is empty\n";
505 return false;
506 }
507
508 auto *LastInst = dyn_cast<VPInstruction>(Val: std::prev(x: Exiting->end()));
509 if (!match(V: LastInst, P: m_CombineOr(Ps: m_BranchOnCond(),
510 Ps: m_CombineOr(Ps: m_BranchOnCount(),
511 Ps: m_BranchOnTwoConds())))) {
512 errs() << "VPlan vector loop exit must end with BranchOnCount, "
513 "BranchOnCond, or BranchOnTwoConds VPInstruction\n";
514 return false;
515 }
516
517 return true;
518}
519
520bool llvm::verifyVPlanIsValid(const VPlan &Plan) {
521 VPDominatorTree VPDT(const_cast<VPlan &>(Plan));
522 VPlanVerifier Verifier(VPDT);
523 return Verifier.verify(Plan);
524}
525