LLVM  9.0.0svn
LCSSA.cpp
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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"
35 #include "llvm/Analysis/LoopPass.h"
39 #include "llvm/IR/Constants.h"
40 #include "llvm/IR/Dominators.h"
41 #include "llvm/IR/Function.h"
42 #include "llvm/IR/Instructions.h"
43 #include "llvm/IR/IntrinsicInst.h"
45 #include "llvm/Pass.h"
46 #include "llvm/Transforms/Utils.h"
49 using namespace llvm;
50 
51 #define DEBUG_TYPE "lcssa"
52 
53 STATISTIC(NumLCSSA, "Number of live out of a loop variables");
54 
55 #ifdef EXPENSIVE_CHECKS
56 static bool VerifyLoopLCSSA = true;
57 #else
58 static bool VerifyLoopLCSSA = false;
59 #endif
61  VerifyLoopLCSSAFlag("verify-loop-lcssa", cl::location(VerifyLoopLCSSA),
62  cl::Hidden,
63  cl::desc("Verify loop lcssa form (time consuming)"));
64 
65 /// Return true if the specified block is in the list.
66 static bool isExitBlock(BasicBlock *BB,
67  const SmallVectorImpl<BasicBlock *> &ExitBlocks) {
68  return is_contained(ExitBlocks, BB);
69 }
70 
71 /// For every instruction from the worklist, check to see if it has any uses
72 /// that are outside the current loop. If so, insert LCSSA PHI nodes and
73 /// rewrite the uses.
75  DominatorTree &DT, LoopInfo &LI) {
76  SmallVector<Use *, 16> UsesToRewrite;
77  SmallSetVector<PHINode *, 16> PHIsToRemove;
78  PredIteratorCache PredCache;
79  bool Changed = false;
80 
81  // Cache the Loop ExitBlocks across this loop. We expect to get a lot of
82  // instructions within the same loops, computing the exit blocks is
83  // expensive, and we're not mutating the loop structure.
85 
86  while (!Worklist.empty()) {
87  UsesToRewrite.clear();
88 
89  Instruction *I = Worklist.pop_back_val();
90  assert(!I->getType()->isTokenTy() && "Tokens shouldn't be in the worklist");
91  BasicBlock *InstBB = I->getParent();
92  Loop *L = LI.getLoopFor(InstBB);
93  assert(L && "Instruction belongs to a BB that's not part of a loop");
94  if (!LoopExitBlocks.count(L))
95  L->getExitBlocks(LoopExitBlocks[L]);
96  assert(LoopExitBlocks.count(L));
97  const SmallVectorImpl<BasicBlock *> &ExitBlocks = LoopExitBlocks[L];
98 
99  if (ExitBlocks.empty())
100  continue;
101 
102  for (Use &U : I->uses()) {
103  Instruction *User = cast<Instruction>(U.getUser());
104  BasicBlock *UserBB = User->getParent();
105  if (auto *PN = dyn_cast<PHINode>(User))
106  UserBB = PN->getIncomingBlock(U);
107 
108  if (InstBB != UserBB && !L->contains(UserBB))
109  UsesToRewrite.push_back(&U);
110  }
111 
112  // If there are no uses outside the loop, exit with no change.
113  if (UsesToRewrite.empty())
114  continue;
115 
116  ++NumLCSSA; // We are applying the transformation
117 
118  // Invoke instructions are special in that their result value is not
119  // available along their unwind edge. The code below tests to see whether
120  // DomBB dominates the value, so adjust DomBB to the normal destination
121  // block, which is effectively where the value is first usable.
122  BasicBlock *DomBB = InstBB;
123  if (auto *Inv = dyn_cast<InvokeInst>(I))
124  DomBB = Inv->getNormalDest();
125 
126  DomTreeNode *DomNode = DT.getNode(DomBB);
127 
128  SmallVector<PHINode *, 16> AddedPHIs;
129  SmallVector<PHINode *, 8> PostProcessPHIs;
130 
131  SmallVector<PHINode *, 4> InsertedPHIs;
132  SSAUpdater SSAUpdate(&InsertedPHIs);
133  SSAUpdate.Initialize(I->getType(), I->getName());
134 
135  // Insert the LCSSA phi's into all of the exit blocks dominated by the
136  // value, and add them to the Phi's map.
137  for (BasicBlock *ExitBB : ExitBlocks) {
138  if (!DT.dominates(DomNode, DT.getNode(ExitBB)))
139  continue;
140 
141  // If we already inserted something for this BB, don't reprocess it.
142  if (SSAUpdate.HasValueForBlock(ExitBB))
143  continue;
144 
145  PHINode *PN = PHINode::Create(I->getType(), PredCache.size(ExitBB),
146  I->getName() + ".lcssa", &ExitBB->front());
147  // Get the debug location from the original instruction.
148  PN->setDebugLoc(I->getDebugLoc());
149  // Add inputs from inside the loop for this PHI.
150  for (BasicBlock *Pred : PredCache.get(ExitBB)) {
151  PN->addIncoming(I, Pred);
152 
153  // If the exit block has a predecessor not within the loop, arrange for
154  // the incoming value use corresponding to that predecessor to be
155  // rewritten in terms of a different LCSSA PHI.
156  if (!L->contains(Pred))
157  UsesToRewrite.push_back(
159  PN->getNumIncomingValues() - 1)));
160  }
161 
162  AddedPHIs.push_back(PN);
163 
164  // Remember that this phi makes the value alive in this block.
165  SSAUpdate.AddAvailableValue(ExitBB, PN);
166 
167  // LoopSimplify might fail to simplify some loops (e.g. when indirect
168  // branches are involved). In such situations, it might happen that an
169  // exit for Loop L1 is the header of a disjoint Loop L2. Thus, when we
170  // create PHIs in such an exit block, we are also inserting PHIs into L2's
171  // header. This could break LCSSA form for L2 because these inserted PHIs
172  // can also have uses outside of L2. Remember all PHIs in such situation
173  // as to revisit than later on. FIXME: Remove this if indirectbr support
174  // into LoopSimplify gets improved.
175  if (auto *OtherLoop = LI.getLoopFor(ExitBB))
176  if (!L->contains(OtherLoop))
177  PostProcessPHIs.push_back(PN);
178  }
179 
180  // Rewrite all uses outside the loop in terms of the new PHIs we just
181  // inserted.
182  for (Use *UseToRewrite : UsesToRewrite) {
183  // If this use is in an exit block, rewrite to use the newly inserted PHI.
184  // This is required for correctness because SSAUpdate doesn't handle uses
185  // in the same block. It assumes the PHI we inserted is at the end of the
186  // block.
187  Instruction *User = cast<Instruction>(UseToRewrite->getUser());
188  BasicBlock *UserBB = User->getParent();
189  if (auto *PN = dyn_cast<PHINode>(User))
190  UserBB = PN->getIncomingBlock(*UseToRewrite);
191 
192  if (isa<PHINode>(UserBB->begin()) && isExitBlock(UserBB, ExitBlocks)) {
193  // Tell the VHs that the uses changed. This updates SCEV's caches.
194  if (UseToRewrite->get()->hasValueHandle())
195  ValueHandleBase::ValueIsRAUWd(*UseToRewrite, &UserBB->front());
196  UseToRewrite->set(&UserBB->front());
197  continue;
198  }
199 
200  // If we added a single PHI, it must dominate all uses and we can directly
201  // rename it.
202  if (AddedPHIs.size() == 1) {
203  // Tell the VHs that the uses changed. This updates SCEV's caches.
204  // We might call ValueIsRAUWd multiple times for the same value.
205  if (UseToRewrite->get()->hasValueHandle())
206  ValueHandleBase::ValueIsRAUWd(*UseToRewrite, AddedPHIs[0]);
207  UseToRewrite->set(AddedPHIs[0]);
208  continue;
209  }
210 
211  // Otherwise, do full PHI insertion.
212  SSAUpdate.RewriteUse(*UseToRewrite);
213  }
214 
216  llvm::findDbgValues(DbgValues, I);
217 
218  // Update pre-existing debug value uses that reside outside the loop.
219  auto &Ctx = I->getContext();
220  for (auto DVI : DbgValues) {
221  BasicBlock *UserBB = DVI->getParent();
222  if (InstBB == UserBB || L->contains(UserBB))
223  continue;
224  // We currently only handle debug values residing in blocks that were
225  // traversed while rewriting the uses. If we inserted just a single PHI,
226  // we will handle all relevant debug values.
227  Value *V = AddedPHIs.size() == 1 ? AddedPHIs[0]
228  : SSAUpdate.FindValueForBlock(UserBB);
229  if (V)
230  DVI->setOperand(0, MetadataAsValue::get(Ctx, ValueAsMetadata::get(V)));
231  }
232 
233  // SSAUpdater might have inserted phi-nodes inside other loops. We'll need
234  // to post-process them to keep LCSSA form.
235  for (PHINode *InsertedPN : InsertedPHIs) {
236  if (auto *OtherLoop = LI.getLoopFor(InsertedPN->getParent()))
237  if (!L->contains(OtherLoop))
238  PostProcessPHIs.push_back(InsertedPN);
239  }
240 
241  // Post process PHI instructions that were inserted into another disjoint
242  // loop and update their exits properly.
243  for (auto *PostProcessPN : PostProcessPHIs)
244  if (!PostProcessPN->use_empty())
245  Worklist.push_back(PostProcessPN);
246 
247  // Keep track of PHI nodes that we want to remove because they did not have
248  // any uses rewritten. If the new PHI is used, store it so that we can
249  // try to propagate dbg.value intrinsics to it.
250  SmallVector<PHINode *, 2> NeedDbgValues;
251  for (PHINode *PN : AddedPHIs)
252  if (PN->use_empty())
253  PHIsToRemove.insert(PN);
254  else
255  NeedDbgValues.push_back(PN);
256  insertDebugValuesForPHIs(InstBB, NeedDbgValues);
257  Changed = true;
258  }
259  // Remove PHI nodes that did not have any uses rewritten. We need to redo the
260  // use_empty() check here, because even if the PHI node wasn't used when added
261  // to PHIsToRemove, later added PHI nodes can be using it. This cleanup is
262  // not guaranteed to handle trees/cycles of PHI nodes that only are used by
263  // each other. Such situations has only been noticed when the input IR
264  // contains unreachable code, and leaving some extra redundant PHI nodes in
265  // such situations is considered a minor problem.
266  for (PHINode *PN : PHIsToRemove)
267  if (PN->use_empty())
268  PN->eraseFromParent();
269  return Changed;
270 }
271 
272 // Compute the set of BasicBlocks in the loop `L` dominating at least one exit.
274  Loop &L, DominatorTree &DT, SmallVector<BasicBlock *, 8> &ExitBlocks,
275  SmallSetVector<BasicBlock *, 8> &BlocksDominatingExits) {
276  SmallVector<BasicBlock *, 8> BBWorklist;
277 
278  // We start from the exit blocks, as every block trivially dominates itself
279  // (not strictly).
280  for (BasicBlock *BB : ExitBlocks)
281  BBWorklist.push_back(BB);
282 
283  while (!BBWorklist.empty()) {
284  BasicBlock *BB = BBWorklist.pop_back_val();
285 
286  // Check if this is a loop header. If this is the case, we're done.
287  if (L.getHeader() == BB)
288  continue;
289 
290  // Otherwise, add its immediate predecessor in the dominator tree to the
291  // worklist, unless we visited it already.
292  BasicBlock *IDomBB = DT.getNode(BB)->getIDom()->getBlock();
293 
294  // Exit blocks can have an immediate dominator not beloinging to the
295  // loop. For an exit block to be immediately dominated by another block
296  // outside the loop, it implies not all paths from that dominator, to the
297  // exit block, go through the loop.
298  // Example:
299  //
300  // |---- A
301  // | |
302  // | B<--
303  // | | |
304  // |---> C --
305  // |
306  // D
307  //
308  // C is the exit block of the loop and it's immediately dominated by A,
309  // which doesn't belong to the loop.
310  if (!L.contains(IDomBB))
311  continue;
312 
313  if (BlocksDominatingExits.insert(IDomBB))
314  BBWorklist.push_back(IDomBB);
315  }
316 }
317 
319  ScalarEvolution *SE) {
320  bool Changed = false;
321 
322 #ifdef EXPENSIVE_CHECKS
323  // Verify all sub-loops are in LCSSA form already.
324  for (Loop *SubLoop: L)
325  assert(SubLoop->isRecursivelyLCSSAForm(DT, *LI) && "Subloop not in LCSSA!");
326 #endif
327 
328  SmallVector<BasicBlock *, 8> ExitBlocks;
329  L.getExitBlocks(ExitBlocks);
330  if (ExitBlocks.empty())
331  return false;
332 
333  SmallSetVector<BasicBlock *, 8> BlocksDominatingExits;
334 
335  // We want to avoid use-scanning leveraging dominance informations.
336  // If a block doesn't dominate any of the loop exits, the none of the values
337  // defined in the loop can be used outside.
338  // We compute the set of blocks fullfilling the conditions in advance
339  // walking the dominator tree upwards until we hit a loop header.
340  computeBlocksDominatingExits(L, DT, ExitBlocks, BlocksDominatingExits);
341 
343 
344  // Look at all the instructions in the loop, checking to see if they have uses
345  // outside the loop. If so, put them into the worklist to rewrite those uses.
346  for (BasicBlock *BB : BlocksDominatingExits) {
347  // Skip blocks that are part of any sub-loops, they must be in LCSSA
348  // already.
349  if (LI->getLoopFor(BB) != &L)
350  continue;
351  for (Instruction &I : *BB) {
352  // Reject two common cases fast: instructions with no uses (like stores)
353  // and instructions with one use that is in the same block as this.
354  if (I.use_empty() ||
355  (I.hasOneUse() && I.user_back()->getParent() == BB &&
356  !isa<PHINode>(I.user_back())))
357  continue;
358 
359  // Tokens cannot be used in PHI nodes, so we skip over them.
360  // We can run into tokens which are live out of a loop with catchswitch
361  // instructions in Windows EH if the catchswitch has one catchpad which
362  // is inside the loop and another which is not.
363  if (I.getType()->isTokenTy())
364  continue;
365 
366  Worklist.push_back(&I);
367  }
368  }
369  Changed = formLCSSAForInstructions(Worklist, DT, *LI);
370 
371  // If we modified the code, remove any caches about the loop from SCEV to
372  // avoid dangling entries.
373  // FIXME: This is a big hammer, can we clear the cache more selectively?
374  if (SE && Changed)
375  SE->forgetLoop(&L);
376 
377  assert(L.isLCSSAForm(DT));
378 
379  return Changed;
380 }
381 
382 /// Process a loop nest depth first.
384  ScalarEvolution *SE) {
385  bool Changed = false;
386 
387  // Recurse depth-first through inner loops.
388  for (Loop *SubLoop : L.getSubLoops())
389  Changed |= formLCSSARecursively(*SubLoop, DT, LI, SE);
390 
391  Changed |= formLCSSA(L, DT, LI, SE);
392  return Changed;
393 }
394 
395 /// Process all loops in the function, inner-most out.
397  ScalarEvolution *SE) {
398  bool Changed = false;
399  for (auto &L : *LI)
400  Changed |= formLCSSARecursively(*L, DT, LI, SE);
401  return Changed;
402 }
403 
404 namespace {
405 struct LCSSAWrapperPass : public FunctionPass {
406  static char ID; // Pass identification, replacement for typeid
407  LCSSAWrapperPass() : FunctionPass(ID) {
409  }
410 
411  // Cached analysis information for the current function.
412  DominatorTree *DT;
413  LoopInfo *LI;
414  ScalarEvolution *SE;
415 
416  bool runOnFunction(Function &F) override;
417  void verifyAnalysis() const override {
418  // This check is very expensive. On the loop intensive compiles it may cause
419  // up to 10x slowdown. Currently it's disabled by default. LPPassManager
420  // always does limited form of the LCSSA verification. Similar reasoning
421  // was used for the LoopInfo verifier.
422  if (VerifyLoopLCSSA) {
423  assert(all_of(*LI,
424  [&](Loop *L) {
425  return L->isRecursivelyLCSSAForm(*DT, *LI);
426  }) &&
427  "LCSSA form is broken!");
428  }
429  };
430 
431  /// This transformation requires natural loop information & requires that
432  /// loop preheaders be inserted into the CFG. It maintains both of these,
433  /// as well as the CFG. It also requires dominator information.
434  void getAnalysisUsage(AnalysisUsage &AU) const override {
435  AU.setPreservesCFG();
436 
445 
446  // This is needed to perform LCSSA verification inside LPPassManager
449  }
450 };
451 }
452 
453 char LCSSAWrapperPass::ID = 0;
454 INITIALIZE_PASS_BEGIN(LCSSAWrapperPass, "lcssa", "Loop-Closed SSA Form Pass",
455  false, false)
459 INITIALIZE_PASS_END(LCSSAWrapperPass, "lcssa", "Loop-Closed SSA Form Pass",
460  false, false)
461 
462 Pass *llvm::createLCSSAPass() { return new LCSSAWrapperPass(); }
464 
465 /// Transform \p F into loop-closed SSA form.
467  LI = &getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
468  DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
469  auto *SEWP = getAnalysisIfAvailable<ScalarEvolutionWrapperPass>();
470  SE = SEWP ? &SEWP->getSE() : nullptr;
471 
472  return formLCSSAOnAllLoops(LI, *DT, SE);
473 }
474 
476  auto &LI = AM.getResult<LoopAnalysis>(F);
477  auto &DT = AM.getResult<DominatorTreeAnalysis>(F);
478  auto *SE = AM.getCachedResult<ScalarEvolutionAnalysis>(F);
479  if (!formLCSSAOnAllLoops(&LI, DT, SE))
480  return PreservedAnalyses::all();
481 
483  PA.preserveSet<CFGAnalyses>();
484  PA.preserve<BasicAA>();
485  PA.preserve<GlobalsAA>();
486  PA.preserve<SCEVAA>();
488  return PA;
489 }
Legacy wrapper pass to provide the GlobalsAAResult object.
Pass interface - Implemented by all &#39;passes&#39;.
Definition: Pass.h:80
void initializeLCSSAWrapperPassPass(PassRegistry &)
iterator_range< use_iterator > uses()
Definition: Value.h:354
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:769
This class represents lattice values for constants.
Definition: AllocatorList.h:23
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 &#39;Ty&#39;.
Definition: SSAUpdater.cpp:53
bool isRecursivelyLCSSAForm(DominatorTree &DT, const LoopInfo &LI) const
Return true if this Loop and all inner subloops are in LCSSA form.
Definition: LoopInfo.cpp:183
void AddAvailableValue(BasicBlock *BB, Value *V)
Indicate that a rewritten value is available in the specified block with the specified value...
Definition: SSAUpdater.cpp:71
The main scalar evolution driver.
LLVMContext & getContext() const
All values hold a context through their type.
Definition: Value.cpp:705
Pass * createLCSSAPass()
Definition: LCSSA.cpp:462
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:1185
STATISTIC(NumFunctions, "Total number of functions")
Analysis pass which computes a DominatorTree.
Definition: Dominators.h:230
F(f)
static bool isExitBlock(BasicBlock *BB, const SmallVectorImpl< BasicBlock *> &ExitBlocks)
Return true if the specified block is in the list.
Definition: LCSSA.cpp:66
bool formLCSSARecursively(Loop &L, DominatorTree &DT, LoopInfo *LI, ScalarEvolution *SE)
Put a loop nest into LCSSA form.
Definition: LCSSA.cpp:383
static unsigned getOperandNumForIncomingValue(unsigned i)
AnalysisUsage & addRequired()
ArrayRef< BasicBlock * > get(BasicBlock *BB)
#define INITIALIZE_PASS_DEPENDENCY(depName)
Definition: PassSupport.h:50
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:689
A Use represents the edge between a Value definition and its users.
Definition: Use.h:55
Analysis pass that exposes the LoopInfo for a function.
Definition: LoopInfo.h:944
BlockT * getHeader() const
Definition: LoopInfo.h:99
void insertDebugValuesForPHIs(BasicBlock *BB, SmallVectorImpl< PHINode *> &InsertedPHIs)
Propagate dbg.value intrinsics through the newly inserted PHIs.
Definition: Local.cpp:1440
void getExitBlocks(SmallVectorImpl< BlockT *> &ExitBlocks) const
Return all of the successor blocks of this loop.
Definition: LoopInfoImpl.h:62
void findDbgValues(SmallVectorImpl< DbgValueInst *> &DbgValues, Value *V)
Finds the llvm.dbg.value intrinsics describing a value.
Definition: Local.cpp:1506
Type * getType() const
All values are typed, get the type of this value.
Definition: Value.h:244
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...
Memory SSA
Definition: MemorySSA.cpp:64
AnalysisUsage & addPreservedID(const void *ID)
static void ValueIsRAUWd(Value *Old, Value *New)
Definition: Value.cpp:885
Concrete subclass of DominatorTreeBase that is used to compute a normal dominator tree...
Definition: Dominators.h:144
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:105
NodeT * getBlock() const
static bool runOnFunction(Function &F, bool PostInlining)
bool formLCSSAForInstructions(SmallVectorImpl< Instruction *> &Worklist, DominatorTree &DT, LoopInfo &LI)
Ensures LCSSA form for every instruction from the Worklist in the scope of innermost containing loop...
Definition: LCSSA.cpp:74
A set of analyses that are preserved following a run of a transformation pass.
Definition: PassManager.h:153
void setDebugLoc(DebugLoc Loc)
Set the debug location information for this instruction.
Definition: Instruction.h:321
LLVM Basic Block Representation.
Definition: BasicBlock.h:57
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:58
This file contains the declarations for the subclasses of Constant, which represent the different fla...
char & LCSSAID
Definition: LCSSA.cpp:463
Represent the analysis usage information of a pass.
Analysis pass providing a never-invalidated alias analysis result.
FunctionPass class - This class is used to implement most global optimizations.
Definition: Pass.h:284
Analysis pass providing a never-invalidated alias analysis result.
static PreservedAnalyses all()
Construct a special preserved set that preserves all passes.
Definition: PassManager.h:159
size_t size() const
Definition: SmallVector.h:52
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
static bool formLCSSAOnAllLoops(LoopInfo *LI, DominatorTree &DT, ScalarEvolution *SE)
Process all loops in the function, inner-most out.
Definition: LCSSA.cpp:396
bool formLCSSA(Loop &L, DominatorTree &DT, LoopInfo *LI, ScalarEvolution *SE)
Put loop into LCSSA form.
Definition: LCSSA.cpp:318
bool contains(const LoopT *L) const
Return true if the specified loop is contained within in this loop.
Definition: LoopInfo.h:109
A SetVector that performs no allocations if smaller than a certain size.
Definition: SetVector.h:297
Legacy wrapper pass to provide the SCEVAAResult object.
static ValueAsMetadata * get(Value *V)
Definition: Metadata.cpp:348
This is a &#39;vector&#39; (really, a variable-sized array), optimized for the case when the array is small...
Definition: SmallVector.h:839
bool dominates(const Instruction *Def, const Use &U) const
Return true if Def dominates a use in User.
Definition: Dominators.cpp:248
LLVM_NODISCARD T pop_back_val()
Definition: SmallVector.h:373
static PHINode * Create(Type *Ty, unsigned NumReservedValues, const Twine &NameStr="", Instruction *InsertBefore=nullptr)
Constructors - NumReservedValues is a hint for the number of incoming edges that this phi node will h...
void setPreservesCFG()
This function should be called by the pass, iff they do not:
Definition: Pass.cpp:285
unsigned getNumIncomingValues() const
Return the number of incoming edges.
PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM)
Definition: LCSSA.cpp:475
Represents analyses that only rely on functions&#39; control flow.
Definition: PassManager.h:114
Analysis pass that exposes the ScalarEvolution for a function.
lcssa
Definition: LCSSA.cpp:459
const std::vector< LoopT * > & getSubLoops() const
Return the loops contained entirely within this loop.
Definition: LoopInfo.h:130
Analysis pass providing a never-invalidated alias analysis result.
const DebugLoc & getDebugLoc() const
Return the debug location for this node as a DebugLoc.
Definition: Instruction.h:324
static void computeBlocksDominatingExits(Loop &L, DominatorTree &DT, SmallVector< BasicBlock *, 8 > &ExitBlocks, SmallSetVector< BasicBlock *, 8 > &BlocksDominatingExits)
Definition: LCSSA.cpp:273
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...
LLVM_NODISCARD bool empty() const
Definition: SmallVector.h:55
Represents a single loop in the control flow graph.
Definition: LoopInfo.h:464
bool isTokenTy() const
Return true if this is &#39;token&#39;.
Definition: Type.h:193
void preserveSet()
Mark an analysis set as preserved.
Definition: PassManager.h:189
StringRef getName() const
Return a constant reference to the value&#39;s name.
Definition: Value.cpp:214
const Function * getParent() const
Return the enclosing method, or null if none.
Definition: BasicBlock.h:106
#define I(x, y, z)
Definition: MD5.cpp:58
PassT::Result * getCachedResult(IRUnitT &IR) const
Get the cached result of an analysis pass for a given IR unit.
Definition: PassManager.h:788
void preserve()
Mark an analysis as preserved.
Definition: PassManager.h:174
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:171
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
LLVM_NODISCARD char front() const
front - Get the first character in the string.
Definition: StringRef.h:134
LLVM Value Representation.
Definition: Value.h:72
The legacy pass manager&#39;s analysis pass to compute loop information.
Definition: LoopInfo.h:969
This is the interface for LLVM&#39;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:259
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:189
LocationClass< Ty > location(Ty &L)
Definition: CommandLine.h:438
const BasicBlock * getParent() const
Definition: Instruction.h:66
bool HasValueForBlock(BasicBlock *BB) const
Return true if the SSAUpdater already has a value for the specified block.
Definition: SSAUpdater.cpp:62
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:1244