LLVM  12.0.0git
LCSSA.cpp
Go to the documentation of this file.
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 
30 #include "llvm/ADT/STLExtras.h"
31 #include "llvm/ADT/Statistic.h"
36 #include "llvm/Analysis/LoopPass.h"
40 #include "llvm/IR/Constants.h"
41 #include "llvm/IR/Dominators.h"
42 #include "llvm/IR/Function.h"
43 #include "llvm/IR/IRBuilder.h"
44 #include "llvm/IR/Instructions.h"
45 #include "llvm/IR/IntrinsicInst.h"
47 #include "llvm/InitializePasses.h"
48 #include "llvm/Pass.h"
50 #include "llvm/Transforms/Utils.h"
54 using namespace llvm;
55 
56 #define DEBUG_TYPE "lcssa"
57 
58 STATISTIC(NumLCSSA, "Number of live out of a loop variables");
59 
60 #ifdef EXPENSIVE_CHECKS
61 static bool VerifyLoopLCSSA = true;
62 #else
63 static bool VerifyLoopLCSSA = false;
64 #endif
66  VerifyLoopLCSSAFlag("verify-loop-lcssa", cl::location(VerifyLoopLCSSA),
67  cl::Hidden,
68  cl::desc("Verify loop lcssa form (time consuming)"));
69 
70 /// Return true if the specified block is in the list.
71 static bool isExitBlock(BasicBlock *BB,
72  const SmallVectorImpl<BasicBlock *> &ExitBlocks) {
73  return is_contained(ExitBlocks, BB);
74 }
75 
76 /// For every instruction from the worklist, check to see if it has any uses
77 /// that are outside the current loop. If so, insert LCSSA PHI nodes and
78 /// rewrite the uses.
80  const DominatorTree &DT, const LoopInfo &LI,
82  SmallVectorImpl<PHINode *> *PHIsToRemove) {
83  SmallVector<Use *, 16> UsesToRewrite;
84  SmallSetVector<PHINode *, 16> LocalPHIsToRemove;
85  PredIteratorCache PredCache;
86  bool Changed = false;
87 
89 
90  // Cache the Loop ExitBlocks across this loop. We expect to get a lot of
91  // instructions within the same loops, computing the exit blocks is
92  // expensive, and we're not mutating the loop structure.
94 
95  while (!Worklist.empty()) {
96  UsesToRewrite.clear();
97 
98  Instruction *I = Worklist.pop_back_val();
99  assert(!I->getType()->isTokenTy() && "Tokens shouldn't be in the worklist");
100  BasicBlock *InstBB = I->getParent();
101  Loop *L = LI.getLoopFor(InstBB);
102  assert(L && "Instruction belongs to a BB that's not part of a loop");
103  if (!LoopExitBlocks.count(L))
104  L->getExitBlocks(LoopExitBlocks[L]);
105  assert(LoopExitBlocks.count(L));
106  const SmallVectorImpl<BasicBlock *> &ExitBlocks = LoopExitBlocks[L];
107 
108  if (ExitBlocks.empty())
109  continue;
110 
111  for (Use &U : I->uses()) {
112  Instruction *User = cast<Instruction>(U.getUser());
113  BasicBlock *UserBB = User->getParent();
114 
115  // For practical purposes, we consider that the use in a PHI
116  // occurs in the respective predecessor block. For more info,
117  // see the `phi` doc in LangRef and the LCSSA doc.
118  if (auto *PN = dyn_cast<PHINode>(User))
119  UserBB = PN->getIncomingBlock(U);
120 
121  if (InstBB != UserBB && !L->contains(UserBB))
122  UsesToRewrite.push_back(&U);
123  }
124 
125  // If there are no uses outside the loop, exit with no change.
126  if (UsesToRewrite.empty())
127  continue;
128 
129  ++NumLCSSA; // We are applying the transformation
130 
131  // Invoke instructions are special in that their result value is not
132  // available along their unwind edge. The code below tests to see whether
133  // DomBB dominates the value, so adjust DomBB to the normal destination
134  // block, which is effectively where the value is first usable.
135  BasicBlock *DomBB = InstBB;
136  if (auto *Inv = dyn_cast<InvokeInst>(I))
137  DomBB = Inv->getNormalDest();
138 
139  const DomTreeNode *DomNode = DT.getNode(DomBB);
140 
141  SmallVector<PHINode *, 16> AddedPHIs;
142  SmallVector<PHINode *, 8> PostProcessPHIs;
143 
144  SmallVector<PHINode *, 4> InsertedPHIs;
145  SSAUpdater SSAUpdate(&InsertedPHIs);
146  SSAUpdate.Initialize(I->getType(), I->getName());
147 
148  // Force re-computation of I, as some users now need to use the new PHI
149  // node.
150  if (SE)
151  SE->forgetValue(I);
152 
153  // Insert the LCSSA phi's into all of the exit blocks dominated by the
154  // value, and add them to the Phi's map.
155  for (BasicBlock *ExitBB : ExitBlocks) {
156  if (!DT.dominates(DomNode, DT.getNode(ExitBB)))
157  continue;
158 
159  // If we already inserted something for this BB, don't reprocess it.
160  if (SSAUpdate.HasValueForBlock(ExitBB))
161  continue;
162  Builder.SetInsertPoint(&ExitBB->front());
163  PHINode *PN = Builder.CreatePHI(I->getType(), PredCache.size(ExitBB),
164  I->getName() + ".lcssa");
165  // Get the debug location from the original instruction.
166  PN->setDebugLoc(I->getDebugLoc());
167 
168  // Add inputs from inside the loop for this PHI. This is valid
169  // because `I` dominates `ExitBB` (checked above). This implies
170  // that every incoming block/edge is dominated by `I` as well,
171  // i.e. we can add uses of `I` to those incoming edges/append to the incoming
172  // blocks without violating the SSA dominance property.
173  for (BasicBlock *Pred : PredCache.get(ExitBB)) {
174  PN->addIncoming(I, Pred);
175 
176  // If the exit block has a predecessor not within the loop, arrange for
177  // the incoming value use corresponding to that predecessor to be
178  // rewritten in terms of a different LCSSA PHI.
179  if (!L->contains(Pred))
180  UsesToRewrite.push_back(
182  PN->getNumIncomingValues() - 1)));
183  }
184 
185  AddedPHIs.push_back(PN);
186 
187  // Remember that this phi makes the value alive in this block.
188  SSAUpdate.AddAvailableValue(ExitBB, PN);
189 
190  // LoopSimplify might fail to simplify some loops (e.g. when indirect
191  // branches are involved). In such situations, it might happen that an
192  // exit for Loop L1 is the header of a disjoint Loop L2. Thus, when we
193  // create PHIs in such an exit block, we are also inserting PHIs into L2's
194  // header. This could break LCSSA form for L2 because these inserted PHIs
195  // can also have uses outside of L2. Remember all PHIs in such situation
196  // as to revisit than later on. FIXME: Remove this if indirectbr support
197  // into LoopSimplify gets improved.
198  if (auto *OtherLoop = LI.getLoopFor(ExitBB))
199  if (!L->contains(OtherLoop))
200  PostProcessPHIs.push_back(PN);
201  }
202 
203  // Rewrite all uses outside the loop in terms of the new PHIs we just
204  // inserted.
205  for (Use *UseToRewrite : UsesToRewrite) {
206  Instruction *User = cast<Instruction>(UseToRewrite->getUser());
207  BasicBlock *UserBB = User->getParent();
208 
209  // For practical purposes, we consider that the use in a PHI
210  // occurs in the respective predecessor block. For more info,
211  // see the `phi` doc in LangRef and the LCSSA doc.
212  if (auto *PN = dyn_cast<PHINode>(User))
213  UserBB = PN->getIncomingBlock(*UseToRewrite);
214 
215  // If this use is in an exit block, rewrite to use the newly inserted PHI.
216  // This is required for correctness because SSAUpdate doesn't handle uses
217  // in the same block. It assumes the PHI we inserted is at the end of the
218  // block.
219  if (isa<PHINode>(UserBB->begin()) && isExitBlock(UserBB, ExitBlocks)) {
220  UseToRewrite->set(&UserBB->front());
221  continue;
222  }
223 
224  // If we added a single PHI, it must dominate all uses and we can directly
225  // rename it.
226  if (AddedPHIs.size() == 1) {
227  UseToRewrite->set(AddedPHIs[0]);
228  continue;
229  }
230 
231  // Otherwise, do full PHI insertion.
232  SSAUpdate.RewriteUse(*UseToRewrite);
233  }
234 
236  llvm::findDbgValues(DbgValues, I);
237 
238  // Update pre-existing debug value uses that reside outside the loop.
239  auto &Ctx = I->getContext();
240  for (auto DVI : DbgValues) {
241  BasicBlock *UserBB = DVI->getParent();
242  if (InstBB == UserBB || L->contains(UserBB))
243  continue;
244  // We currently only handle debug values residing in blocks that were
245  // traversed while rewriting the uses. If we inserted just a single PHI,
246  // we will handle all relevant debug values.
247  Value *V = AddedPHIs.size() == 1 ? AddedPHIs[0]
248  : SSAUpdate.FindValueForBlock(UserBB);
249  if (V)
250  DVI->setOperand(0, MetadataAsValue::get(Ctx, ValueAsMetadata::get(V)));
251  }
252 
253  // SSAUpdater might have inserted phi-nodes inside other loops. We'll need
254  // to post-process them to keep LCSSA form.
255  for (PHINode *InsertedPN : InsertedPHIs) {
256  if (auto *OtherLoop = LI.getLoopFor(InsertedPN->getParent()))
257  if (!L->contains(OtherLoop))
258  PostProcessPHIs.push_back(InsertedPN);
259  }
260 
261  // Post process PHI instructions that were inserted into another disjoint
262  // loop and update their exits properly.
263  for (auto *PostProcessPN : PostProcessPHIs)
264  if (!PostProcessPN->use_empty())
265  Worklist.push_back(PostProcessPN);
266 
267  // Keep track of PHI nodes that we want to remove because they did not have
268  // any uses rewritten.
269  for (PHINode *PN : AddedPHIs)
270  if (PN->use_empty())
271  LocalPHIsToRemove.insert(PN);
272 
273  Changed = true;
274  }
275 
276  // Remove PHI nodes that did not have any uses rewritten or add them to
277  // PHIsToRemove, so the caller can remove them after some additional cleanup.
278  // We need to redo the use_empty() check here, because even if the PHI node
279  // wasn't used when added to LocalPHIsToRemove, later added PHI nodes can be
280  // using it. This cleanup is not guaranteed to handle trees/cycles of PHI
281  // nodes that only are used by each other. Such situations has only been
282  // noticed when the input IR contains unreachable code, and leaving some extra
283  // redundant PHI nodes in such situations is considered a minor problem.
284  if (PHIsToRemove) {
285  PHIsToRemove->append(LocalPHIsToRemove.begin(), LocalPHIsToRemove.end());
286  } else {
287  for (PHINode *PN : LocalPHIsToRemove)
288  if (PN->use_empty())
289  PN->eraseFromParent();
290  }
291  return Changed;
292 }
293 
294 // Compute the set of BasicBlocks in the loop `L` dominating at least one exit.
296  Loop &L, const DominatorTree &DT, SmallVector<BasicBlock *, 8> &ExitBlocks,
297  SmallSetVector<BasicBlock *, 8> &BlocksDominatingExits) {
298  SmallVector<BasicBlock *, 8> BBWorklist;
299 
300  // We start from the exit blocks, as every block trivially dominates itself
301  // (not strictly).
302  for (BasicBlock *BB : ExitBlocks)
303  BBWorklist.push_back(BB);
304 
305  while (!BBWorklist.empty()) {
306  BasicBlock *BB = BBWorklist.pop_back_val();
307 
308  // Check if this is a loop header. If this is the case, we're done.
309  if (L.getHeader() == BB)
310  continue;
311 
312  // Otherwise, add its immediate predecessor in the dominator tree to the
313  // worklist, unless we visited it already.
314  BasicBlock *IDomBB = DT.getNode(BB)->getIDom()->getBlock();
315 
316  // Exit blocks can have an immediate dominator not beloinging to the
317  // loop. For an exit block to be immediately dominated by another block
318  // outside the loop, it implies not all paths from that dominator, to the
319  // exit block, go through the loop.
320  // Example:
321  //
322  // |---- A
323  // | |
324  // | B<--
325  // | | |
326  // |---> C --
327  // |
328  // D
329  //
330  // C is the exit block of the loop and it's immediately dominated by A,
331  // which doesn't belong to the loop.
332  if (!L.contains(IDomBB))
333  continue;
334 
335  if (BlocksDominatingExits.insert(IDomBB))
336  BBWorklist.push_back(IDomBB);
337  }
338 }
339 
340 bool llvm::formLCSSA(Loop &L, const DominatorTree &DT, const LoopInfo *LI,
341  ScalarEvolution *SE) {
342  bool Changed = false;
343 
344 #ifdef EXPENSIVE_CHECKS
345  // Verify all sub-loops are in LCSSA form already.
346  for (Loop *SubLoop: L)
347  assert(SubLoop->isRecursivelyLCSSAForm(DT, *LI) && "Subloop not in LCSSA!");
348 #endif
349 
350  SmallVector<BasicBlock *, 8> ExitBlocks;
351  L.getExitBlocks(ExitBlocks);
352  if (ExitBlocks.empty())
353  return false;
354 
355  SmallSetVector<BasicBlock *, 8> BlocksDominatingExits;
356 
357  // We want to avoid use-scanning leveraging dominance informations.
358  // If a block doesn't dominate any of the loop exits, the none of the values
359  // defined in the loop can be used outside.
360  // We compute the set of blocks fullfilling the conditions in advance
361  // walking the dominator tree upwards until we hit a loop header.
362  computeBlocksDominatingExits(L, DT, ExitBlocks, BlocksDominatingExits);
363 
365 
366  // Look at all the instructions in the loop, checking to see if they have uses
367  // outside the loop. If so, put them into the worklist to rewrite those uses.
368  for (BasicBlock *BB : BlocksDominatingExits) {
369  // Skip blocks that are part of any sub-loops, they must be in LCSSA
370  // already.
371  if (LI->getLoopFor(BB) != &L)
372  continue;
373  for (Instruction &I : *BB) {
374  // Reject two common cases fast: instructions with no uses (like stores)
375  // and instructions with one use that is in the same block as this.
376  if (I.use_empty() ||
377  (I.hasOneUse() && I.user_back()->getParent() == BB &&
378  !isa<PHINode>(I.user_back())))
379  continue;
380 
381  // Tokens cannot be used in PHI nodes, so we skip over them.
382  // We can run into tokens which are live out of a loop with catchswitch
383  // instructions in Windows EH if the catchswitch has one catchpad which
384  // is inside the loop and another which is not.
385  if (I.getType()->isTokenTy())
386  continue;
387 
388  Worklist.push_back(&I);
389  }
390  }
391 
392  IRBuilder<> Builder(L.getHeader()->getContext());
393  Changed = formLCSSAForInstructions(Worklist, DT, *LI, SE, Builder);
394 
395  // If we modified the code, remove any caches about the loop from SCEV to
396  // avoid dangling entries.
397  // FIXME: This is a big hammer, can we clear the cache more selectively?
398  if (SE && Changed)
399  SE->forgetLoop(&L);
400 
401  assert(L.isLCSSAForm(DT));
402 
403  return Changed;
404 }
405 
406 /// Process a loop nest depth first.
408  const LoopInfo *LI, ScalarEvolution *SE) {
409  bool Changed = false;
410 
411  // Recurse depth-first through inner loops.
412  for (Loop *SubLoop : L.getSubLoops())
413  Changed |= formLCSSARecursively(*SubLoop, DT, LI, SE);
414 
415  Changed |= formLCSSA(L, DT, LI, SE);
416  return Changed;
417 }
418 
419 /// Process all loops in the function, inner-most out.
420 static bool formLCSSAOnAllLoops(const LoopInfo *LI, const DominatorTree &DT,
421  ScalarEvolution *SE) {
422  bool Changed = false;
423  for (auto &L : *LI)
424  Changed |= formLCSSARecursively(*L, DT, LI, SE);
425  return Changed;
426 }
427 
428 namespace {
429 struct LCSSAWrapperPass : public FunctionPass {
430  static char ID; // Pass identification, replacement for typeid
431  LCSSAWrapperPass() : FunctionPass(ID) {
433  }
434 
435  // Cached analysis information for the current function.
436  DominatorTree *DT;
437  LoopInfo *LI;
438  ScalarEvolution *SE;
439 
440  bool runOnFunction(Function &F) override;
441  void verifyAnalysis() const override {
442  // This check is very expensive. On the loop intensive compiles it may cause
443  // up to 10x slowdown. Currently it's disabled by default. LPPassManager
444  // always does limited form of the LCSSA verification. Similar reasoning
445  // was used for the LoopInfo verifier.
446  if (VerifyLoopLCSSA) {
447  assert(all_of(*LI,
448  [&](Loop *L) {
449  return L->isRecursivelyLCSSAForm(*DT, *LI);
450  }) &&
451  "LCSSA form is broken!");
452  }
453  };
454 
455  /// This transformation requires natural loop information & requires that
456  /// loop preheaders be inserted into the CFG. It maintains both of these,
457  /// as well as the CFG. It also requires dominator information.
458  void getAnalysisUsage(AnalysisUsage &AU) const override {
459  AU.setPreservesCFG();
460 
471 
472  // This is needed to perform LCSSA verification inside LPPassManager
475  }
476 };
477 }
478 
479 char LCSSAWrapperPass::ID = 0;
480 INITIALIZE_PASS_BEGIN(LCSSAWrapperPass, "lcssa", "Loop-Closed SSA Form Pass",
481  false, false)
485 INITIALIZE_PASS_END(LCSSAWrapperPass, "lcssa", "Loop-Closed SSA Form Pass",
486  false, false)
487 
488 Pass *llvm::createLCSSAPass() { return new LCSSAWrapperPass(); }
490 
491 /// Transform \p F into loop-closed SSA form.
493  LI = &getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
494  DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
495  auto *SEWP = getAnalysisIfAvailable<ScalarEvolutionWrapperPass>();
496  SE = SEWP ? &SEWP->getSE() : nullptr;
497 
498  return formLCSSAOnAllLoops(LI, *DT, SE);
499 }
500 
502  auto &LI = AM.getResult<LoopAnalysis>(F);
503  auto &DT = AM.getResult<DominatorTreeAnalysis>(F);
504  auto *SE = AM.getCachedResult<ScalarEvolutionAnalysis>(F);
505  if (!formLCSSAOnAllLoops(&LI, DT, SE))
506  return PreservedAnalyses::all();
507 
509  PA.preserveSet<CFGAnalyses>();
510  PA.preserve<BasicAA>();
511  PA.preserve<GlobalsAA>();
512  PA.preserve<SCEVAA>();
514  // BPI maps terminators to probabilities, since we don't modify the CFG, no
515  // updates are needed to preserve it.
518  return PA;
519 }
Legacy wrapper pass to provide the GlobalsAAResult object.
Pass interface - Implemented by all 'passes'.
Definition: Pass.h:91
Common base class shared among various IRBuilders.
Definition: IRBuilder.h:95
void initializeLCSSAWrapperPassPass(PassRegistry &)
AnalysisUsage & addPreserved()
Add the specified Pass class to the set of analyses preserved by this pass.
Helper class for SSA formation on a set of values defined in multiple blocks.
Definition: SSAUpdater.h:38
void addIncoming(Value *V, BasicBlock *BB)
Add an incoming value to the end of the PHI list.
static PassRegistry * getPassRegistry()
getPassRegistry - Access the global registry object, which is automatically initialized at applicatio...
PassT::Result & getResult(IRUnitT &IR, ExtraArgTs... ExtraArgs)
Get the result of an analysis pass for a given IR unit.
Definition: PassManager.h:785
This class represents lattice values for constants.
Definition: AllocatorList.h:23
static bool formLCSSAOnAllLoops(const LoopInfo *LI, const DominatorTree &DT, ScalarEvolution *SE)
Process all loops in the function, inner-most out.
Definition: LCSSA.cpp:420
This is the interface for a simple mod/ref and alias analysis over globals.
void Initialize(Type *Ty, StringRef Name)
Reset this object to get ready for a new set of SSA updates with type 'Ty'.
Definition: SSAUpdater.cpp:53
void AddAvailableValue(BasicBlock *BB, Value *V)
Indicate that a rewritten value is available in the specified block with the specified value.
Definition: SSAUpdater.cpp:70
The main scalar evolution driver.
void findDbgValues(SmallVectorImpl< DbgValueInst * > &DbgValues, Value *V)
Finds the llvm.dbg.value intrinsics describing a value.
Definition: Local.cpp:1634
Pass * createLCSSAPass()
Definition: LCSSA.cpp:488
const Use & getOperandUse(unsigned i) const
Definition: User.h:182
bool all_of(R &&range, UnaryPredicate P)
Provide wrappers to std::all_of which take ranges instead of having to pass begin/end explicitly.
Definition: STLExtras.h:1498
STATISTIC(NumFunctions, "Total number of functions")
Analysis pass which computes a DominatorTree.
Definition: Dominators.h:249
F(f)
static void computeBlocksDominatingExits(Loop &L, const DominatorTree &DT, SmallVector< BasicBlock *, 8 > &ExitBlocks, SmallSetVector< BasicBlock *, 8 > &BlocksDominatingExits)
Definition: LCSSA.cpp:295
iterator end()
Get an iterator to the end of the SetVector.
Definition: SetVector.h:92
static unsigned getOperandNumForIncomingValue(unsigned i)
AnalysisUsage & addRequired()
ArrayRef< BasicBlock * > get(BasicBlock *BB)
Legacy analysis pass which computes MemorySSA.
Definition: MemorySSA.h:960
This is the interface for a SCEV-based alias analysis.
LoopT * getLoopFor(const BlockT *BB) const
Return the inner most loop that BB lives in.
Definition: LoopInfo.h:963
A Use represents the edge between a Value definition and its users.
Definition: Use.h:44
This class consists of common code factored out of the SmallVector class to reduce code duplication b...
Definition: APFloat.h:43
Analysis pass that exposes the LoopInfo for a function.
Definition: LoopInfo.h:1224
BlockT * getHeader() const
Definition: LoopInfo.h:104
Analysis pass which computes BranchProbabilityInfo.
bool insert(const value_type &X)
Insert a new element into the SetVector.
Definition: SetVector.h:141
PredIteratorCache - This class is an extremely trivial cache for predecessor iterator queries.
iterator begin()
Get an iterator to the beginning of the SetVector.
Definition: SetVector.h:82
Memory SSA
Definition: MemorySSA.cpp:72
AnalysisUsage & addPreservedID(const void *ID)
Concrete subclass of DominatorTreeBase that is used to compute a normal dominator tree.
Definition: Dominators.h:151
Legacy analysis pass which computes BranchProbabilityInfo.
bool formLCSSAForInstructions(SmallVectorImpl< Instruction * > &Worklist, const DominatorTree &DT, const LoopInfo &LI, ScalarEvolution *SE, IRBuilderBase &Builder, SmallVectorImpl< PHINode * > *PHIsToRemove=nullptr)
Ensures LCSSA form for every instruction from the Worklist in the scope of innermost containing loop.
Definition: LCSSA.cpp:79
Value * FindValueForBlock(BasicBlock *BB) const
Return the value for the specified block if the SSAUpdater has one, otherwise return nullptr.
Definition: SSAUpdater.cpp:66
static MetadataAsValue * get(LLVMContext &Context, Metadata *MD)
Definition: Metadata.cpp:106
NodeT * getBlock() const
static bool runOnFunction(Function &F, bool PostInlining)
A set of analyses that are preserved following a run of a transformation pass.
Definition: PassManager.h:155
void setDebugLoc(DebugLoc Loc)
Set the debug location information for this instruction.
Definition: Instruction.h:362
LLVM Basic Block Representation.
Definition: BasicBlock.h:58
size_t size(BasicBlock *BB) const
DomTreeNodeBase * getIDom() const
static cl::opt< bool, true > VerifyLoopLCSSAFlag("verify-loop-lcssa", cl::location(VerifyLoopLCSSA), cl::Hidden, cl::desc("Verify loop lcssa form (time consuming)"))
static bool VerifyLoopLCSSA
Definition: LCSSA.cpp:63
This file contains the declarations for the subclasses of Constant, which represent the different fla...
char & LCSSAID
Definition: LCSSA.cpp:489
Represent the analysis usage information of a pass.
Analysis pass providing a never-invalidated alias analysis result.
bool dominates(const Value *Def, const Use &U) const
Return true if value Def dominates use U, in the sense that Def is available at U,...
Definition: Dominators.cpp:260
bool formLCSSARecursively(Loop &L, const DominatorTree &DT, const LoopInfo *LI, ScalarEvolution *SE)
Put a loop nest into LCSSA form.
Definition: LCSSA.cpp:407
FunctionPass class - This class is used to implement most global optimizations.
Definition: Pass.h:298
Analysis pass providing a never-invalidated alias analysis result.
void forgetValue(Value *V)
This method should be called by the client when it has changed a value in a way that may effect its v...
void getExitBlocks(SmallVectorImpl< BlockT * > &ExitBlocks) const
Return all of the successor blocks of this loop.
Definition: LoopInfoImpl.h:61
assume Assume Builder
static PreservedAnalyses all()
Construct a special preserved set that preserves all passes.
Definition: PassManager.h:161
DomTreeNodeBase< NodeT > * getNode(const NodeT *BB) const
getNode - return the (Post)DominatorTree node for the specified basic block.
INITIALIZE_PASS_END(RegBankSelect, DEBUG_TYPE, "Assign register bank of generic virtual registers", false, false) RegBankSelect
char & LoopSimplifyID
bool contains(const LoopT *L) const
Return true if the specified loop is contained within in this loop.
Definition: LoopInfo.h:122
A SetVector that performs no allocations if smaller than a certain size.
Definition: SetVector.h:307
Legacy wrapper pass to provide the SCEVAAResult object.
static ValueAsMetadata * get(Value *V)
Definition: Metadata.cpp:349
This is a 'vector' (really, a variable-sized array), optimized for the case when the array is small.
Definition: SmallVector.h:1116
bool formLCSSA(Loop &L, const DominatorTree &DT, const LoopInfo *LI, ScalarEvolution *SE)
Put loop into LCSSA form.
Definition: LCSSA.cpp:340
An analysis that produces MemorySSA for a function.
Definition: MemorySSA.h:921
LLVM_NODISCARD T pop_back_val()
Definition: SmallVector.h:595
void setPreservesCFG()
This function should be called by the pass, iff they do not:
Definition: Pass.cpp:253
unsigned getNumIncomingValues() const
Return the number of incoming edges.
PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM)
Definition: LCSSA.cpp:501
Represents analyses that only rely on functions' control flow.
Definition: PassManager.h:116
void append(in_iter in_start, in_iter in_end)
Add the specified range to the end of the SmallVector.
Definition: SmallVector.h:608
Analysis pass that exposes the ScalarEvolution for a function.
lcssa
Definition: LCSSA.cpp:485
const std::vector< LoopT * > & getSubLoops() const
Return the loops contained entirely within this loop.
Definition: LoopInfo.h:143
Analysis pass providing a never-invalidated alias analysis result.
void forgetLoop(const Loop *L)
This method should be called by the client when it has changed a loop in a way that may effect Scalar...
Represents a single loop in the control flow graph.
Definition: LoopInfo.h:529
void preserveSet()
Mark an analysis set as preserved.
Definition: PassManager.h:191
const Function * getParent() const
Return the enclosing method, or null if none.
Definition: BasicBlock.h:107
#define I(x, y, z)
Definition: MD5.cpp:59
PassT::Result * getCachedResult(IRUnitT &IR) const
Get the cached result of an analysis pass for a given IR unit.
Definition: PassManager.h:804
void preserve()
Mark an analysis as preserved.
Definition: PassManager.h:176
INITIALIZE_PASS_BEGIN(LCSSAWrapperPass, "lcssa", "Loop-Closed SSA Form Pass", false, false) INITIALIZE_PASS_END(LCSSAWrapperPass
size_type count(const_arg_type_t< KeyT > Val) const
Return 1 if the specified key is in the map, 0 otherwise.
Definition: DenseMap.h:145
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
LLVM Value Representation.
Definition: Value.h:75
bool isRecursivelyLCSSAForm(const DominatorTree &DT, const LoopInfo &LI) const
Return true if this Loop and all inner subloops are in LCSSA form.
Definition: LoopInfo.cpp:461
This file exposes an interface to building/using memory SSA to walk memory instructions using a use/d...
The legacy pass manager's analysis pass to compute loop information.
Definition: LoopInfo.h:1249
static bool isExitBlock(BasicBlock *BB, const SmallVectorImpl< BasicBlock * > &ExitBlocks)
Return true if the specified block is in the list.
Definition: LCSSA.cpp:71
This is the interface for LLVM's primary stateless and local alias analysis.
A container for analyses that lazily runs them and caches their results.
Legacy analysis pass which computes a DominatorTree.
Definition: Dominators.h:278
A wrapper pass to provide the legacy pass manager access to a suitably prepared AAResults object.
void RewriteUse(Use &U)
Rewrite a use of the symbolic value.
Definition: SSAUpdater.cpp:188
LocationClass< Ty > location(Ty &L)
Definition: CommandLine.h:443
bool HasValueForBlock(BasicBlock *BB) const
Return true if the SSAUpdater already has a value for the specified block.
Definition: SSAUpdater.cpp:62
INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
Legacy wrapper pass to provide the BasicAAResult object.
bool is_contained(R &&Range, const E &Element)
Wrapper function around std::find to detect if an element exists in a container.
Definition: STLExtras.h:1563