1//===-- LCSSA.cpp - Convert loops into loop-closed SSA form ---------------===//
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// This pass transforms loops by placing phi nodes at the end of the loops for
10// all values that are live across the loop boundary. For example, it turns
11// the left into the right code:
12//
13// for (...) for (...)
14// if (c) if (c)
15// X1 = ... X1 = ...
16// else else
17// X2 = ... X2 = ...
18// X3 = phi(X1, X2) X3 = phi(X1, X2)
19// ... = X3 + 4 X4 = phi(X3)
20// ... = X4 + 4
21//
22// This is still valid LLVM; the extra phi nodes are purely redundant, and will
23// be trivially eliminated by InstCombine. The major benefit of this
24// transformation is that it makes many other loop optimizations, such as
25// LoopUnswitching, simpler.
26//
27//===----------------------------------------------------------------------===//
28
29#include "llvm/Transforms/Utils/LCSSA.h"
30#include "llvm/ADT/STLExtras.h"
31#include "llvm/ADT/Statistic.h"
32#include "llvm/Analysis/AliasAnalysis.h"
33#include "llvm/Analysis/BasicAliasAnalysis.h"
34#include "llvm/Analysis/BranchProbabilityInfo.h"
35#include "llvm/Analysis/GlobalsModRef.h"
36#include "llvm/Analysis/LoopInfo.h"
37#include "llvm/Analysis/LoopPass.h"
38#include "llvm/Analysis/MemorySSA.h"
39#include "llvm/Analysis/ScalarEvolution.h"
40#include "llvm/Analysis/ScalarEvolutionAliasAnalysis.h"
41#include "llvm/IR/DebugInfo.h"
42#include "llvm/IR/Dominators.h"
43#include "llvm/IR/Instructions.h"
44#include "llvm/IR/PredIteratorCache.h"
45#include "llvm/InitializePasses.h"
46#include "llvm/Pass.h"
47#include "llvm/Support/CommandLine.h"
48#include "llvm/Transforms/Utils.h"
49#include "llvm/Transforms/Utils/LoopUtils.h"
50#include "llvm/Transforms/Utils/SSAUpdater.h"
51using namespace llvm;
52
53#define DEBUG_TYPE "lcssa"
54
55STATISTIC(NumLCSSA, "Number of live out of a loop variables");
56
57#ifdef EXPENSIVE_CHECKS
58static bool VerifyLoopLCSSA = true;
59#else
60static bool VerifyLoopLCSSA = false;
61#endif
62static cl::opt<bool, true>
63 VerifyLoopLCSSAFlag("verify-loop-lcssa", cl::location(L&: VerifyLoopLCSSA),
64 cl::Hidden,
65 cl::desc("Verify loop lcssa form (time consuming)"));
66
67/// Return true if the specified block is in the list.
68static bool isExitBlock(BasicBlock *BB,
69 const SmallVectorImpl<BasicBlock *> &ExitBlocks) {
70 return is_contained(Range: ExitBlocks, Element: BB);
71}
72
73// Cache the Loop ExitBlocks computed during the analysis. We expect to get a
74// lot of instructions within the same loops, computing the exit blocks is
75// expensive, and we're not mutating the loop structure.
76using LoopExitBlocksTy = SmallDenseMap<Loop *, SmallVector<BasicBlock *, 1>>;
77
78/// For every instruction from the worklist, check to see if it has any uses
79/// that are outside the current loop. If so, insert LCSSA PHI nodes and
80/// rewrite the uses.
81static bool
82formLCSSAForInstructionsImpl(SmallVectorImpl<Instruction *> &Worklist,
83 const DominatorTree &DT, const LoopInfo &LI,
84 ScalarEvolution *SE,
85 SmallVectorImpl<PHINode *> *PHIsToRemove,
86 SmallVectorImpl<PHINode *> *InsertedPHIs,
87 LoopExitBlocksTy &LoopExitBlocks) {
88 SmallVector<Use *, 16> UsesToRewrite;
89 SmallSetVector<PHINode *, 16> LocalPHIsToRemove;
90 PredIteratorCache PredCache;
91 bool Changed = false;
92
93 while (!Worklist.empty()) {
94 UsesToRewrite.clear();
95
96 Instruction *I = Worklist.pop_back_val();
97 assert(!I->getType()->isTokenLikeTy() &&
98 "Token-like values shouldn't be in the worklist");
99 BasicBlock *InstBB = I->getParent();
100 Loop *L = LI.getLoopFor(BB: InstBB);
101 assert(L && "Instruction belongs to a BB that's not part of a loop");
102 auto [It, Inserted] = LoopExitBlocks.try_emplace(Key: L);
103 if (Inserted)
104 L->getExitBlocks(ExitBlocks&: It->second);
105 const SmallVectorImpl<BasicBlock *> &ExitBlocks = It->second;
106
107 if (ExitBlocks.empty())
108 continue;
109
110 SmallVector<Instruction *> LifetimeMarkers;
111 bool DropLifetimeMarkers = false;
112 for (Use &U : make_early_inc_range(Range: I->uses())) {
113 Instruction *User = cast<Instruction>(Val: U.getUser());
114 BasicBlock *UserBB = User->getParent();
115
116 // Lifetime markers must refer directly to an alloca. Rewriting their
117 // operands through LCSSA PHIs would produce invalid IR, so conservatively
118 // drop all lifetime markers when one crosses the loop boundary.
119 if (User->isLifetimeStartOrEnd()) {
120 LifetimeMarkers.push_back(Elt: User);
121 if (InstBB != UserBB && !L->contains(BB: UserBB))
122 DropLifetimeMarkers = true;
123 continue;
124 }
125
126 // Skip uses in unreachable blocks.
127 if (!DT.isReachableFromEntry(A: UserBB)) {
128 U.set(PoisonValue::get(T: I->getType()));
129 continue;
130 }
131
132 // For practical purposes, we consider that the use in a PHI
133 // occurs in the respective predecessor block. For more info,
134 // see the `phi` doc in LangRef and the LCSSA doc.
135 if (auto *PN = dyn_cast<PHINode>(Val: User))
136 UserBB = PN->getIncomingBlock(U);
137
138 if (InstBB != UserBB && !L->contains(BB: UserBB))
139 UsesToRewrite.push_back(Elt: &U);
140 }
141
142 if (DropLifetimeMarkers) {
143 // Use-list order is arbitrary, so wait until all markers are collected.
144 for (Instruction *Marker : LifetimeMarkers)
145 Marker->eraseFromParent();
146 Changed = true;
147 }
148
149 // If there are no uses outside the loop, exit with no change.
150 if (UsesToRewrite.empty())
151 continue;
152
153 ++NumLCSSA; // We are applying the transformation
154
155 // Invoke instructions are special in that their result value is not
156 // available along their unwind edge. The code below tests to see whether
157 // DomBB dominates the value, so adjust DomBB to the normal destination
158 // block, which is effectively where the value is first usable.
159 BasicBlock *DomBB = InstBB;
160 if (auto *Inv = dyn_cast<InvokeInst>(Val: I))
161 DomBB = Inv->getNormalDest();
162
163 const DomTreeNode *DomNode = DT.getNode(BB: DomBB);
164
165 SmallVector<PHINode *, 16> AddedPHIs;
166 SmallVector<PHINode *, 8> PostProcessPHIs;
167
168 SmallVector<PHINode *, 4> LocalInsertedPHIs;
169 SSAUpdater SSAUpdate(&LocalInsertedPHIs);
170 SSAUpdate.Initialize(Ty: I->getType(), Name: I->getName());
171
172 // Insert the LCSSA phi's into all of the exit blocks dominated by the
173 // value, and add them to the Phi's map.
174 bool HasSCEV = SE && SE->isSCEVable(Ty: I->getType()) &&
175 SE->getExistingSCEV(V: I) != nullptr;
176 for (BasicBlock *ExitBB : ExitBlocks) {
177 if (!DT.dominates(A: DomNode, B: DT.getNode(BB: ExitBB)))
178 continue;
179
180 // If we already inserted something for this BB, don't reprocess it.
181 if (SSAUpdate.HasValueForBlock(BB: ExitBB))
182 continue;
183 PHINode *PN = PHINode::Create(Ty: I->getType(), NumReservedValues: PredCache.size(BB: ExitBB),
184 NameStr: I->getName() + ".lcssa");
185 PN->insertBefore(InsertPos: ExitBB->begin());
186 if (InsertedPHIs)
187 InsertedPHIs->push_back(Elt: PN);
188 // Get the debug location from the original instruction.
189 PN->setDebugLoc(I->getDebugLoc());
190
191 // Add inputs from inside the loop for this PHI. This is valid
192 // because `I` dominates `ExitBB` (checked above). This implies
193 // that every incoming block/edge is dominated by `I` as well,
194 // i.e. we can add uses of `I` to those incoming edges/append to the incoming
195 // blocks without violating the SSA dominance property.
196 for (BasicBlock *Pred : PredCache.get(BB: ExitBB)) {
197 PN->addIncoming(V: I, BB: Pred);
198
199 // If the exit block has a predecessor not within the loop, arrange for
200 // the incoming value use corresponding to that predecessor to be
201 // rewritten in terms of a different LCSSA PHI.
202 if (!L->contains(BB: Pred))
203 UsesToRewrite.push_back(
204 Elt: &PN->getOperandUse(i: PN->getOperandNumForIncomingValue(
205 i: PN->getNumIncomingValues() - 1)));
206 }
207
208 AddedPHIs.push_back(Elt: PN);
209
210 // Remember that this phi makes the value alive in this block.
211 SSAUpdate.AddAvailableValue(BB: ExitBB, V: PN);
212
213 // LoopSimplify might fail to simplify some loops (e.g. when indirect
214 // branches are involved). In such situations, it might happen that an
215 // exit for Loop L1 is the header of a disjoint Loop L2. Thus, when we
216 // create PHIs in such an exit block, we are also inserting PHIs into L2's
217 // header. This could break LCSSA form for L2 because these inserted PHIs
218 // can also have uses outside of L2. Remember all PHIs in such situation
219 // as to revisit than later on. FIXME: Remove this if indirectbr support
220 // into LoopSimplify gets improved.
221 if (auto *OtherLoop = LI.getLoopFor(BB: ExitBB))
222 if (!L->contains(L: OtherLoop))
223 PostProcessPHIs.push_back(Elt: PN);
224
225 // If we have a cached SCEV for the original instruction, make sure the
226 // new LCSSA phi node is also cached. This makes sures that BECounts
227 // based on it will be invalidated when the LCSSA phi node is invalidated,
228 // which some passes rely on.
229 if (HasSCEV)
230 SE->getSCEV(V: PN);
231 }
232
233 // Rewrite all uses outside the loop in terms of the new PHIs we just
234 // inserted.
235 for (Use *UseToRewrite : UsesToRewrite) {
236 Instruction *User = cast<Instruction>(Val: UseToRewrite->getUser());
237 BasicBlock *UserBB = User->getParent();
238
239 // For practical purposes, we consider that the use in a PHI
240 // occurs in the respective predecessor block. For more info,
241 // see the `phi` doc in LangRef and the LCSSA doc.
242 if (auto *PN = dyn_cast<PHINode>(Val: User))
243 UserBB = PN->getIncomingBlock(U: *UseToRewrite);
244
245 // If this use is in an exit block, rewrite to use the newly inserted PHI.
246 // This is required for correctness because SSAUpdate doesn't handle uses
247 // in the same block. It assumes the PHI we inserted is at the end of the
248 // block.
249 if (isa<PHINode>(Val: UserBB->begin()) && isExitBlock(BB: UserBB, ExitBlocks)) {
250 UseToRewrite->set(&UserBB->front());
251 continue;
252 }
253
254 // If we added a single PHI, it must dominate all uses and we can directly
255 // rename it.
256 if (AddedPHIs.size() == 1) {
257 UseToRewrite->set(AddedPHIs[0]);
258 continue;
259 }
260
261 // Otherwise, do full PHI insertion.
262 SSAUpdate.RewriteUse(U&: *UseToRewrite);
263 }
264
265 SmallVector<DbgVariableRecord *, 4> DbgVariableRecords;
266 llvm::findDbgValues(V: I, DbgVariableRecords);
267
268 // Update pre-existing debug value uses that reside outside the loop.
269 for (DbgVariableRecord *DVR : DbgVariableRecords) {
270 BasicBlock *UserBB = DVR->getMarker()->getParent();
271 if (InstBB == UserBB || L->contains(BB: UserBB))
272 continue;
273 // We currently only handle debug values residing in blocks that were
274 // traversed while rewriting the uses. If we inserted just a single PHI,
275 // we will handle all relevant debug values.
276 Value *V = AddedPHIs.size() == 1 ? AddedPHIs[0]
277 : SSAUpdate.FindValueForBlock(BB: UserBB);
278 if (V)
279 DVR->replaceVariableLocationOp(OldValue: I, NewValue: V);
280 }
281
282 // SSAUpdater might have inserted phi-nodes inside other loops. We'll need
283 // to post-process them to keep LCSSA form.
284 for (PHINode *InsertedPN : LocalInsertedPHIs) {
285 if (auto *OtherLoop = LI.getLoopFor(BB: InsertedPN->getParent()))
286 if (!L->contains(L: OtherLoop))
287 PostProcessPHIs.push_back(Elt: InsertedPN);
288 if (InsertedPHIs)
289 InsertedPHIs->push_back(Elt: InsertedPN);
290 }
291
292 // Post process PHI instructions that were inserted into another disjoint
293 // loop and update their exits properly.
294 for (auto *PostProcessPN : PostProcessPHIs)
295 if (!PostProcessPN->use_empty())
296 Worklist.push_back(Elt: PostProcessPN);
297
298 // Keep track of PHI nodes that we want to remove because they did not have
299 // any uses rewritten.
300 for (PHINode *PN : AddedPHIs)
301 if (PN->use_empty())
302 LocalPHIsToRemove.insert(X: PN);
303
304 Changed = true;
305 }
306
307 // Remove PHI nodes that did not have any uses rewritten or add them to
308 // PHIsToRemove, so the caller can remove them after some additional cleanup.
309 // We need to redo the use_empty() check here, because even if the PHI node
310 // wasn't used when added to LocalPHIsToRemove, later added PHI nodes can be
311 // using it. This cleanup is not guaranteed to handle trees/cycles of PHI
312 // nodes that only are used by each other. Such situations has only been
313 // noticed when the input IR contains unreachable code, and leaving some extra
314 // redundant PHI nodes in such situations is considered a minor problem.
315 if (PHIsToRemove) {
316 PHIsToRemove->append(in_start: LocalPHIsToRemove.begin(), in_end: LocalPHIsToRemove.end());
317 } else {
318 for (PHINode *PN : LocalPHIsToRemove)
319 if (PN->use_empty())
320 PN->eraseFromParent();
321 }
322 return Changed;
323}
324
325/// For every instruction from the worklist, check to see if it has any uses
326/// that are outside the current loop. If so, insert LCSSA PHI nodes and
327/// rewrite the uses.
328bool llvm::formLCSSAForInstructions(SmallVectorImpl<Instruction *> &Worklist,
329 const DominatorTree &DT, const LoopInfo &LI,
330 ScalarEvolution *SE,
331 SmallVectorImpl<PHINode *> *PHIsToRemove,
332 SmallVectorImpl<PHINode *> *InsertedPHIs) {
333 LoopExitBlocksTy LoopExitBlocks;
334
335 return formLCSSAForInstructionsImpl(Worklist, DT, LI, SE, PHIsToRemove,
336 InsertedPHIs, LoopExitBlocks);
337}
338
339// Compute the set of BasicBlocks in the loop `L` dominating at least one exit.
340static void computeBlocksDominatingExits(
341 Loop &L, const DominatorTree &DT, ArrayRef<BasicBlock *> ExitBlocks,
342 SmallSetVector<BasicBlock *, 8> &BlocksDominatingExits) {
343 // We start from the exit blocks, as every block trivially dominates itself
344 // (not strictly).
345 SmallVector<BasicBlock *, 8> BBWorklist(ExitBlocks);
346
347 while (!BBWorklist.empty()) {
348 BasicBlock *BB = BBWorklist.pop_back_val();
349
350 // Check if this is a loop header. If this is the case, we're done.
351 if (L.getHeader() == BB)
352 continue;
353
354 // Otherwise, add its immediate predecessor in the dominator tree to the
355 // worklist, unless we visited it already.
356 BasicBlock *IDomBB = DT.getNode(BB)->getIDom()->getBlock();
357
358 // Exit blocks can have an immediate dominator not belonging to the
359 // loop. For an exit block to be immediately dominated by another block
360 // outside the loop, it implies not all paths from that dominator, to the
361 // exit block, go through the loop.
362 // Example:
363 //
364 // |---- A
365 // | |
366 // | B<--
367 // | | |
368 // |---> C --
369 // |
370 // D
371 //
372 // C is the exit block of the loop and it's immediately dominated by A,
373 // which doesn't belong to the loop.
374 if (!L.contains(BB: IDomBB))
375 continue;
376
377 if (BlocksDominatingExits.insert(X: IDomBB))
378 BBWorklist.push_back(Elt: IDomBB);
379 }
380}
381
382static bool formLCSSAImpl(Loop &L, const DominatorTree &DT, const LoopInfo *LI,
383 ScalarEvolution *SE,
384 LoopExitBlocksTy &LoopExitBlocks) {
385 bool Changed = false;
386
387#ifdef EXPENSIVE_CHECKS
388 // Verify all sub-loops are in LCSSA form already.
389 for (Loop *SubLoop: L) {
390 (void)SubLoop; // Silence unused variable warning.
391 assert(SubLoop->isRecursivelyLCSSAForm(DT, *LI) && "Subloop not in LCSSA!");
392 }
393#endif
394
395 auto [It, Inserted] = LoopExitBlocks.try_emplace(Key: &L);
396 if (Inserted)
397 L.getExitBlocks(ExitBlocks&: It->second);
398 const SmallVectorImpl<BasicBlock *> &ExitBlocks = It->second;
399 if (ExitBlocks.empty())
400 return false;
401
402 SmallSetVector<BasicBlock *, 8> BlocksDominatingExits;
403
404 // We want to avoid use-scanning leveraging dominance informations.
405 // If a block doesn't dominate any of the loop exits, the none of the values
406 // defined in the loop can be used outside.
407 // We compute the set of blocks fullfilling the conditions in advance
408 // walking the dominator tree upwards until we hit a loop header.
409 computeBlocksDominatingExits(L, DT, ExitBlocks, BlocksDominatingExits);
410
411 SmallVector<Instruction *, 8> Worklist;
412
413 // Look at all the instructions in the loop, checking to see if they have uses
414 // outside the loop. If so, put them into the worklist to rewrite those uses.
415 for (BasicBlock *BB : BlocksDominatingExits) {
416 // Skip blocks that are part of any sub-loops, they must be in LCSSA
417 // already.
418 if (LI->getLoopFor(BB) != &L)
419 continue;
420 for (Instruction &I : *BB) {
421 // Reject two common cases fast: instructions with no uses (like stores)
422 // and instructions with one use that is in the same block as this.
423 if (I.use_empty() ||
424 (I.hasOneUse() && I.user_back()->getParent() == BB &&
425 !isa<PHINode>(Val: I.user_back())))
426 continue;
427
428 // Token-like values cannot be used in PHI nodes, so we skip over them.
429 // We can run into tokens which are live out of a loop with catchswitch
430 // instructions in Windows EH if the catchswitch has one catchpad which
431 // is inside the loop and another which is not.
432 if (I.getType()->isTokenLikeTy())
433 continue;
434
435 Worklist.push_back(Elt: &I);
436 }
437 }
438
439 Changed = formLCSSAForInstructionsImpl(Worklist, DT, LI: *LI, SE, PHIsToRemove: nullptr,
440 InsertedPHIs: nullptr, LoopExitBlocks);
441
442 assert(L.isLCSSAForm(DT));
443
444 return Changed;
445}
446
447bool llvm::formLCSSA(Loop &L, const DominatorTree &DT, const LoopInfo *LI,
448 ScalarEvolution *SE) {
449 LoopExitBlocksTy LoopExitBlocks;
450
451 return formLCSSAImpl(L, DT, LI, SE, LoopExitBlocks);
452}
453
454/// Process a loop nest depth first.
455static bool formLCSSARecursivelyImpl(Loop &L, const DominatorTree &DT,
456 const LoopInfo *LI, ScalarEvolution *SE,
457 LoopExitBlocksTy &LoopExitBlocks) {
458 bool Changed = false;
459
460 // Recurse depth-first through inner loops.
461 for (Loop *SubLoop : L.getSubLoops())
462 Changed |= formLCSSARecursivelyImpl(L&: *SubLoop, DT, LI, SE, LoopExitBlocks);
463
464 Changed |= formLCSSAImpl(L, DT, LI, SE, LoopExitBlocks);
465 return Changed;
466}
467
468/// Process a loop nest depth first.
469bool llvm::formLCSSARecursively(Loop &L, const DominatorTree &DT,
470 const LoopInfo *LI, ScalarEvolution *SE) {
471 LoopExitBlocksTy LoopExitBlocks;
472
473 return formLCSSARecursivelyImpl(L, DT, LI, SE, LoopExitBlocks);
474}
475
476/// Process all loops in the function, inner-most out.
477static bool formLCSSAOnAllLoops(const LoopInfo *LI, const DominatorTree &DT,
478 ScalarEvolution *SE) {
479 bool Changed = false;
480 for (const auto &L : *LI)
481 Changed |= formLCSSARecursively(L&: *L, DT, LI, SE);
482 return Changed;
483}
484
485namespace {
486struct LCSSAWrapperPass : public FunctionPass {
487 static char ID; // Pass identification, replacement for typeid
488 LCSSAWrapperPass() : FunctionPass(ID) {
489 initializeLCSSAWrapperPassPass(*PassRegistry::getPassRegistry());
490 }
491
492 // Cached analysis information for the current function.
493 DominatorTree *DT;
494 LoopInfo *LI;
495 ScalarEvolution *SE;
496
497 bool runOnFunction(Function &F) override;
498 void verifyAnalysis() const override {
499 // This check is very expensive. On the loop intensive compiles it may cause
500 // up to 10x slowdown. Currently it's disabled by default. LPPassManager
501 // always does limited form of the LCSSA verification. Similar reasoning
502 // was used for the LoopInfo verifier.
503 if (VerifyLoopLCSSA) {
504 assert(all_of(*LI,
505 [&](Loop *L) {
506 return L->isRecursivelyLCSSAForm(*DT, *LI);
507 }) &&
508 "LCSSA form is broken!");
509 }
510 };
511
512 /// This transformation requires natural loop information & requires that
513 /// loop preheaders be inserted into the CFG. It maintains both of these,
514 /// as well as the CFG. It also requires dominator information.
515 void getAnalysisUsage(AnalysisUsage &AU) const override {
516 AU.setPreservesCFG();
517
518 AU.addRequired<DominatorTreeWrapperPass>();
519 AU.addRequired<LoopInfoWrapperPass>();
520 AU.addPreservedID(ID&: LoopSimplifyID);
521 AU.addPreserved<AAResultsWrapperPass>();
522 AU.addPreserved<GlobalsAAWrapperPass>();
523 AU.addPreserved<ScalarEvolutionWrapperPass>();
524 AU.addPreserved<SCEVAAWrapperPass>();
525 AU.addPreserved<BranchProbabilityInfoWrapperPass>();
526 AU.addPreserved<MemorySSAWrapperPass>();
527
528 // This is needed to perform LCSSA verification inside LPPassManager
529 AU.addRequired<LCSSAVerificationPass>();
530 AU.addPreserved<LCSSAVerificationPass>();
531 }
532};
533}
534
535char LCSSAWrapperPass::ID = 0;
536INITIALIZE_PASS_BEGIN(LCSSAWrapperPass, "lcssa", "Loop-Closed SSA Form Pass",
537 false, false)
538INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
539INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass)
540INITIALIZE_PASS_DEPENDENCY(LCSSAVerificationPass)
541INITIALIZE_PASS_END(LCSSAWrapperPass, "lcssa", "Loop-Closed SSA Form Pass",
542 false, false)
543
544Pass *llvm::createLCSSAPass() { return new LCSSAWrapperPass(); }
545char &llvm::LCSSAID = LCSSAWrapperPass::ID;
546
547/// Transform \p F into loop-closed SSA form.
548bool LCSSAWrapperPass::runOnFunction(Function &F) {
549 LI = &getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
550 DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
551 auto *SEWP = getAnalysisIfAvailable<ScalarEvolutionWrapperPass>();
552 SE = SEWP ? &SEWP->getSE() : nullptr;
553
554 return formLCSSAOnAllLoops(LI, DT: *DT, SE);
555}
556
557PreservedAnalyses LCSSAPass::run(Function &F, FunctionAnalysisManager &AM) {
558 auto &LI = AM.getResult<LoopAnalysis>(IR&: F);
559 auto &DT = AM.getResult<DominatorTreeAnalysis>(IR&: F);
560 auto *SE = AM.getCachedResult<ScalarEvolutionAnalysis>(IR&: F);
561 if (!formLCSSAOnAllLoops(LI: &LI, DT, SE))
562 return PreservedAnalyses::all();
563
564 PreservedAnalyses PA;
565 PA.preserveSet<CFGAnalyses>();
566 PA.preserve<ScalarEvolutionAnalysis>();
567 PA.preserve<MemorySSAAnalysis>();
568 return PA;
569}
570