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 // All operands must be prefix-mask. This means an icmp ult/ule LHS, RHS where
176 // the LHS is monotonically increasing and RHS is uniform across VFs and UF.
177 for (VPValue *Op : LastActiveLane.operands()) {
178 VPValue *Mask = Op;
179 VPValue *HeaderMask;
180
181 // Look through any `and`s with the incoming alias mask or a
182 // loop_dependence_war_mask, which are always prefix masks.
183 // 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 Ps: m_VPInstruction<VPInstruction::IncomingAliasMask>()))))
193 Mask = HeaderMask;
194
195 // The header mask is a prefix mask. Before being materialized it is the
196 // loop region's abstract header mask; afterwards it is an active lane mask
197 // (an intrinsic or a phi), or the icmp checked below.
198 if (match(V: Mask, P: m_HeaderMask()) || isa<VPActiveLaneMaskPHIRecipe>(Val: Mask) ||
199 match(V: Mask, P: m_VPInstruction<VPInstruction::ActiveLaneMask>()))
200 continue;
201
202 if (match(V: Mask, P: m_ActiveLaneMask(Op0: m_VPValue(), Op1: m_VPValue(), Op2: m_VPValue())))
203 continue;
204
205 CmpPredicate Pred;
206 VPValue *LHS, *RHS;
207 if (match(V: Mask, P: m_ICmp(Pred, Op0: m_VPValue(V&: LHS), Op1: m_VPValue(V&: RHS))) &&
208 (Pred == CmpInst::ICMP_ULE || Pred == CmpInst::ICMP_ULT) &&
209 isKnownMonotonic(V: LHS) &&
210 (vputils::isUniformAcrossVFsAndUFs(V: RHS) ||
211 match(V: RHS, P: m_EVL(Op0: m_VPValue()))))
212 continue;
213
214 errs() << "LastActiveLane operand ";
215#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
216 VPSlotTracker Tracker(LastActiveLane.getParent()->getPlan());
217 Op->printAsOperand(errs(), Tracker);
218#endif
219 errs() << " must be prefix mask (a header mask or an "
220 "EVL-derived mask currently)\n";
221 return false;
222 }
223
224 return true;
225}
226
227bool VPlanVerifier::verifyVPBasicBlock(const VPBasicBlock *VPBB) {
228 if (!verifyPhiRecipes(VPBB))
229 return false;
230
231 // Verify that defs in VPBB dominate all their uses.
232 DenseMap<const VPRecipeBase *, unsigned> RecipeNumbering;
233 unsigned Cnt = 0;
234 for (const VPRecipeBase &R : *VPBB)
235 RecipeNumbering[&R] = Cnt++;
236
237 for (const VPRecipeBase &R : *VPBB) {
238 if (isa<VPIRInstruction>(Val: &R) && !isa<VPIRBasicBlock>(Val: VPBB)) {
239 errs() << "VPIRInstructions ";
240#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
241 R.dump();
242 errs() << " ";
243#endif
244 errs() << "not in a VPIRBasicBlock!\n";
245 return false;
246 }
247 for (const VPValue *V : R.definedValues()) {
248 // Verify that each defined value has a scalar type.
249 if (!V->getScalarType()) {
250 errs() << "VPValue without scalar type!\n";
251 return false;
252 }
253
254 // MaskedCond may be used from blocks it don't dominate; the block will be
255 // linearized and it will dominate its users after linearization.
256 if (match(V: &R, P: m_VPInstruction<VPInstruction::MaskedCond>()))
257 continue;
258
259 for (const VPUser *U : V->users()) {
260 auto *UI = cast<VPRecipeBase>(Val: U);
261 if (isa<VPIRPhi>(Val: UI) &&
262 UI->getNumOperands() != UI->getParent()->getNumPredecessors()) {
263 errs() << "Phi-like recipe with different number of operands and "
264 "predecessors.\n";
265 return false;
266 }
267
268 if (auto *Phi = dyn_cast<VPPhiAccessors>(Val: UI)) {
269 for (const auto &[IncomingVPV, IncomingVPBB] :
270 Phi->incoming_values_and_blocks()) {
271 if (IncomingVPV != V)
272 continue;
273
274 if (VPDT.dominates(A: VPBB, B: IncomingVPBB))
275 continue;
276
277 errs() << "Incoming def does not dominate incoming block!\n";
278#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
279 VPSlotTracker Tracker(VPBB->getPlan());
280 IncomingVPV->getDefiningRecipe()->print(errs(), " ", Tracker);
281 errs() << "\n does not dominate " << IncomingVPBB->getName()
282 << " for\n";
283 UI->print(errs(), " ", Tracker);
284#endif
285 return false;
286 }
287 continue;
288 }
289 // TODO: Also verify VPPredInstPHIRecipe.
290 if (isa<VPPredInstPHIRecipe>(Val: UI))
291 continue;
292
293 // If the user is in the same block, check it comes after R in the
294 // block.
295 if (UI->getParent() == VPBB) {
296 if (RecipeNumbering[UI] >= RecipeNumbering[&R])
297 continue;
298 } else {
299 if (VPDT.dominates(A: VPBB, B: UI->getParent()))
300 continue;
301 }
302
303 // Recipes in blocks with a MaskedCond may be used in exit blocks; the
304 // block will be linearized and its recipes will dominate their users
305 // after linearization.
306 bool BlockHasMaskedCond = any_of(Range: *VPBB, P: [](const VPRecipeBase &R) {
307 return match(V: &R, P: m_VPInstruction<VPInstruction::MaskedCond>());
308 });
309 if (BlockHasMaskedCond &&
310 any_of(Range: VPBB->getPlan()->getExitBlocks(), P: [UI](VPIRBasicBlock *EB) {
311 return is_contained(Range&: EB->getPredecessors(), Element: UI->getParent());
312 })) {
313 continue;
314 }
315
316 errs() << "Use before def!\n";
317#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
318 VPSlotTracker Tracker(VPBB->getPlan());
319 UI->print(errs(), " ", Tracker);
320 errs() << "\n before\n";
321 R.print(errs(), " ", Tracker);
322 errs() << "\n";
323#endif
324 return false;
325 }
326 }
327 if (const auto *VPI = dyn_cast<VPInstruction>(Val: &R)) {
328 switch (VPI->getOpcode()) {
329 case VPInstruction::LastActiveLane:
330 if (!verifyLastActiveLaneRecipe(LastActiveLane: *VPI))
331 return false;
332 break;
333 default:
334 break;
335 }
336 }
337 if (const auto *DIV = dyn_cast<VPDerivedIVRecipe>(Val: &R)) {
338 if (!DIV->getStartValue()->isDefinedOutsideLoopRegions()) {
339 errs() << "VPDerivedIVRecipe must have start value defined outside "
340 "loop regions\n";
341 return false;
342 }
343 }
344 if (const auto *ScalarIVSteps = dyn_cast<VPScalarIVStepsRecipe>(Val: &R)) {
345 unsigned NumOps = ScalarIVSteps->getNumOperands();
346 if (NumOps != 3 && NumOps != 4) {
347 errs() << "VPScalarIVStepsRecipe must have 3 or 4 operands\n";
348 return false;
349 }
350 }
351 }
352
353 auto *IRBB = dyn_cast<VPIRBasicBlock>(Val: VPBB);
354 if (!IRBB)
355 return true;
356
357 if (!WrappedIRBBs.insert(Ptr: IRBB->getIRBasicBlock()).second) {
358 errs() << "Same IR basic block used by multiple wrapper blocks!\n";
359 return false;
360 }
361
362 return true;
363}
364
365bool VPlanVerifier::verifyBlock(const VPBlockBase *VPB) {
366 auto *VPBB = dyn_cast<VPBasicBlock>(Val: VPB);
367 // Check block's condition bit.
368 if (VPBB && !isa<VPIRBasicBlock>(Val: VPB)) {
369 // For plain CFG VPlans, verify header and latch block structure.
370 if (!VPBB->getParent()) {
371 if (VPBlockUtils::isHeader(VPB: VPBB, VPDT)) {
372 if (VPB->getNumPredecessors() != 2) {
373 errs()
374 << "Header block in plain CFG VPlan must have 2 predecessors!\n";
375 return false;
376 }
377 // Predecessor 0 is preheader, predecessor 1 is latch.
378 if (!VPBlockUtils::isLatch(VPB: VPB->getPredecessors()[1], VPDT)) {
379 errs() << "Header's second predecessor must be the latch!\n";
380 return false;
381 }
382 }
383
384 if (VPBlockUtils::isLatch(VPB: VPBB, VPDT)) {
385 if (!match(V: VPBB->getTerminator(), P: m_Branch())) {
386 errs() << "Latch block must have a branch terminator!\n";
387 return false;
388 }
389 // Successor 0 is middle block, successor 1 is header.
390 if (VPBlockUtils::isHeader(VPB: VPB->getSuccessors()[0], VPDT)) {
391 errs() << "Latch's first successor must not be the header (must be "
392 "middle block)!\n";
393 return false;
394 }
395 }
396 } else if (VPB->getNumSuccessors() > 1 ||
397 (VPBB->isExiting() && !VPBB->getParent()->isReplicator())) {
398 if (!VPBB->getTerminator()) {
399 errs() << "Block has multiple successors but doesn't "
400 "have a proper branch recipe!\n";
401 return false;
402 }
403 } else if (VPBB->getTerminator()) {
404 errs() << "Unexpected branch recipe!\n";
405 return false;
406 }
407 }
408
409 // Check block's successors.
410 const auto &Successors = VPB->getSuccessors();
411 for (const VPBlockBase *Succ : Successors) {
412 // There must be a bi-directional link between block and successor.
413 const auto &SuccPreds = Succ->getPredecessors();
414 if (!is_contained(Range: SuccPreds, Element: VPB)) {
415 errs() << "Missing predecessor link.\n";
416 return false;
417 }
418 }
419
420 // Check block's predecessors.
421 const auto &Predecessors = VPB->getPredecessors();
422
423 for (const VPBlockBase *Pred : Predecessors) {
424 // Block and predecessor must be inside the same region.
425 if (Pred->getParent() != VPB->getParent()) {
426 errs() << "Predecessor is not in the same region.\n";
427 return false;
428 }
429
430 // There must be a bi-directional link between block and predecessor.
431 const auto &PredSuccs = Pred->getSuccessors();
432 if (!is_contained(Range: PredSuccs, Element: VPB)) {
433 errs() << "Missing successor link.\n";
434 return false;
435 }
436 }
437 return !VPBB || verifyVPBasicBlock(VPBB);
438}
439
440bool VPlanVerifier::verifyBlocksInRegion(const VPRegionBlock *Region) {
441 for (const VPBlockBase *VPB : vp_depth_first_shallow(G: Region->getEntry())) {
442 // Check block's parent.
443 if (VPB->getParent() != Region) {
444 errs() << "VPBlockBase has wrong parent\n";
445 return false;
446 }
447
448 if (!verifyBlock(VPB))
449 return false;
450 }
451 return true;
452}
453
454bool VPlanVerifier::verifyRegion(const VPRegionBlock *Region) {
455 const VPBlockBase *Entry = Region->getEntry();
456 const VPBlockBase *Exiting = Region->getExiting();
457
458 // Entry and Exiting shouldn't have any predecessor/successor, respectively.
459 if (Entry->hasPredecessors()) {
460 errs() << "region entry block has predecessors\n";
461 return false;
462 }
463 if (Exiting->getNumSuccessors() != 0) {
464 errs() << "region exiting block has successors\n";
465 return false;
466 }
467
468 return verifyBlocksInRegion(Region);
469}
470
471bool VPlanVerifier::verifyRegionRec(const VPRegionBlock *Region) {
472 // Recurse inside nested regions and check all blocks inside the region.
473 return verifyRegion(Region) &&
474 all_of(Range: vp_depth_first_shallow(G: Region->getEntry()),
475 P: [this](const VPBlockBase *VPB) {
476 const auto *SubRegion = dyn_cast<VPRegionBlock>(Val: VPB);
477 return !SubRegion || verifyRegionRec(Region: SubRegion);
478 });
479}
480
481bool VPlanVerifier::verify(const VPlan &Plan) {
482 if (any_of(Range: vp_depth_first_shallow(G: Plan.getEntry()),
483 P: [this](const VPBlockBase *VPB) { return !verifyBlock(VPB); }))
484 return false;
485
486 const VPRegionBlock *TopRegion = Plan.getVectorLoopRegion();
487 // TODO: Verify all blocks using vp_depth_first_deep iterators.
488 if (!TopRegion)
489 return true;
490
491 if (!verifyRegionRec(Region: TopRegion))
492 return false;
493
494 if (TopRegion->getParent()) {
495 errs() << "VPlan Top Region should have no parent.\n";
496 return false;
497 }
498
499 const VPBasicBlock *Entry = dyn_cast<VPBasicBlock>(Val: TopRegion->getEntry());
500 if (!Entry) {
501 errs() << "VPlan entry block is not a VPBasicBlock\n";
502 return false;
503 }
504
505 const VPBasicBlock *Exiting = dyn_cast<VPBasicBlock>(Val: TopRegion->getExiting());
506 if (!Exiting) {
507 errs() << "VPlan exiting block is not a VPBasicBlock\n";
508 return false;
509 }
510
511 if (Exiting->empty()) {
512 errs() << "VPlan vector loop exiting block must end with BranchOnCount, "
513 "BranchOnCond, or BranchOnTwoConds VPInstruction but is empty\n";
514 return false;
515 }
516
517 auto *LastInst = dyn_cast<VPInstruction>(Val: std::prev(x: Exiting->end()));
518 if (!match(V: LastInst, P: m_Branch())) {
519 errs() << "VPlan vector loop exit must end with BranchOnCount, "
520 "BranchOnCond, or BranchOnTwoConds VPInstruction\n";
521 return false;
522 }
523
524 return true;
525}
526
527bool llvm::verifyVPlanIsValid(const VPlan &Plan) {
528 VPDominatorTree VPDT(const_cast<VPlan &>(Plan));
529 VPlanVerifier Verifier(VPDT);
530 return Verifier.verify(Plan);
531}
532