LLVM  10.0.0svn
ConstantHoisting.cpp
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1 //===- ConstantHoisting.cpp - Prepare code for expensive constants --------===//
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 identifies expensive constants to hoist and coalesces them to
10 // better prepare it for SelectionDAG-based code generation. This works around
11 // the limitations of the basic-block-at-a-time approach.
12 //
13 // First it scans all instructions for integer constants and calculates its
14 // cost. If the constant can be folded into the instruction (the cost is
15 // TCC_Free) or the cost is just a simple operation (TCC_BASIC), then we don't
16 // consider it expensive and leave it alone. This is the default behavior and
17 // the default implementation of getIntImmCost will always return TCC_Free.
18 //
19 // If the cost is more than TCC_BASIC, then the integer constant can't be folded
20 // into the instruction and it might be beneficial to hoist the constant.
21 // Similar constants are coalesced to reduce register pressure and
22 // materialization code.
23 //
24 // When a constant is hoisted, it is also hidden behind a bitcast to force it to
25 // be live-out of the basic block. Otherwise the constant would be just
26 // duplicated and each basic block would have its own copy in the SelectionDAG.
27 // The SelectionDAG recognizes such constants as opaque and doesn't perform
28 // certain transformations on them, which would create a new expensive constant.
29 //
30 // This optimization is only applied to integer constants in instructions and
31 // simple (this means not nested) constant cast expressions. For example:
32 // %0 = load i64* inttoptr (i64 big_constant to i64*)
33 //===----------------------------------------------------------------------===//
34 
36 #include "llvm/ADT/APInt.h"
37 #include "llvm/ADT/DenseMap.h"
38 #include "llvm/ADT/None.h"
39 #include "llvm/ADT/Optional.h"
40 #include "llvm/ADT/SmallPtrSet.h"
41 #include "llvm/ADT/SmallVector.h"
42 #include "llvm/ADT/Statistic.h"
47 #include "llvm/IR/BasicBlock.h"
48 #include "llvm/IR/Constants.h"
50 #include "llvm/IR/Dominators.h"
51 #include "llvm/IR/Function.h"
52 #include "llvm/IR/InstrTypes.h"
53 #include "llvm/IR/Instruction.h"
54 #include "llvm/IR/Instructions.h"
55 #include "llvm/IR/IntrinsicInst.h"
56 #include "llvm/IR/Value.h"
57 #include "llvm/Pass.h"
59 #include "llvm/Support/Casting.h"
61 #include "llvm/Support/Debug.h"
63 #include "llvm/Transforms/Scalar.h"
65 #include <algorithm>
66 #include <cassert>
67 #include <cstdint>
68 #include <iterator>
69 #include <tuple>
70 #include <utility>
71 
72 using namespace llvm;
73 using namespace consthoist;
74 
75 #define DEBUG_TYPE "consthoist"
76 
77 STATISTIC(NumConstantsHoisted, "Number of constants hoisted");
78 STATISTIC(NumConstantsRebased, "Number of constants rebased");
79 
81  "consthoist-with-block-frequency", cl::init(true), cl::Hidden,
82  cl::desc("Enable the use of the block frequency analysis to reduce the "
83  "chance to execute const materialization more frequently than "
84  "without hoisting."));
85 
87  "consthoist-gep", cl::init(false), cl::Hidden,
88  cl::desc("Try hoisting constant gep expressions"));
89 
90 static cl::opt<unsigned>
91 MinNumOfDependentToRebase("consthoist-min-num-to-rebase",
92  cl::desc("Do not rebase if number of dependent constants of a Base is less "
93  "than this number."),
94  cl::init(0), cl::Hidden);
95 
96 namespace {
97 
98 /// The constant hoisting pass.
99 class ConstantHoistingLegacyPass : public FunctionPass {
100 public:
101  static char ID; // Pass identification, replacement for typeid
102 
103  ConstantHoistingLegacyPass() : FunctionPass(ID) {
105  }
106 
107  bool runOnFunction(Function &Fn) override;
108 
109  StringRef getPassName() const override { return "Constant Hoisting"; }
110 
111  void getAnalysisUsage(AnalysisUsage &AU) const override {
112  AU.setPreservesCFG();
118  }
119 
120 private:
122 };
123 
124 } // end anonymous namespace
125 
127 
128 INITIALIZE_PASS_BEGIN(ConstantHoistingLegacyPass, "consthoist",
129  "Constant Hoisting", false, false)
134 INITIALIZE_PASS_END(ConstantHoistingLegacyPass, "consthoist",
135  "Constant Hoisting", false, false)
136 
138  return new ConstantHoistingLegacyPass();
139 }
140 
141 /// Perform the constant hoisting optimization for the given function.
143  if (skipFunction(Fn))
144  return false;
145 
146  LLVM_DEBUG(dbgs() << "********** Begin Constant Hoisting **********\n");
147  LLVM_DEBUG(dbgs() << "********** Function: " << Fn.getName() << '\n');
148 
149  bool MadeChange =
150  Impl.runImpl(Fn, getAnalysis<TargetTransformInfoWrapperPass>().getTTI(Fn),
151  getAnalysis<DominatorTreeWrapperPass>().getDomTree(),
153  ? &getAnalysis<BlockFrequencyInfoWrapperPass>().getBFI()
154  : nullptr,
155  Fn.getEntryBlock(),
156  &getAnalysis<ProfileSummaryInfoWrapperPass>().getPSI());
157 
158  if (MadeChange) {
159  LLVM_DEBUG(dbgs() << "********** Function after Constant Hoisting: "
160  << Fn.getName() << '\n');
161  LLVM_DEBUG(dbgs() << Fn);
162  }
163  LLVM_DEBUG(dbgs() << "********** End Constant Hoisting **********\n");
164 
165  return MadeChange;
166 }
167 
168 /// Find the constant materialization insertion point.
169 Instruction *ConstantHoistingPass::findMatInsertPt(Instruction *Inst,
170  unsigned Idx) const {
171  // If the operand is a cast instruction, then we have to materialize the
172  // constant before the cast instruction.
173  if (Idx != ~0U) {
174  Value *Opnd = Inst->getOperand(Idx);
175  if (auto CastInst = dyn_cast<Instruction>(Opnd))
176  if (CastInst->isCast())
177  return CastInst;
178  }
179 
180  // The simple and common case. This also includes constant expressions.
181  if (!isa<PHINode>(Inst) && !Inst->isEHPad())
182  return Inst;
183 
184  // We can't insert directly before a phi node or an eh pad. Insert before
185  // the terminator of the incoming or dominating block.
186  assert(Entry != Inst->getParent() && "PHI or landing pad in entry block!");
187  if (Idx != ~0U && isa<PHINode>(Inst))
188  return cast<PHINode>(Inst)->getIncomingBlock(Idx)->getTerminator();
189 
190  // This must be an EH pad. Iterate over immediate dominators until we find a
191  // non-EH pad. We need to skip over catchswitch blocks, which are both EH pads
192  // and terminators.
193  auto IDom = DT->getNode(Inst->getParent())->getIDom();
194  while (IDom->getBlock()->isEHPad()) {
195  assert(Entry != IDom->getBlock() && "eh pad in entry block");
196  IDom = IDom->getIDom();
197  }
198 
199  return IDom->getBlock()->getTerminator();
200 }
201 
202 /// Given \p BBs as input, find another set of BBs which collectively
203 /// dominates \p BBs and have the minimal sum of frequencies. Return the BB
204 /// set found in \p BBs.
206  BasicBlock *Entry,
208  assert(!BBs.count(Entry) && "Assume Entry is not in BBs");
209  // Nodes on the current path to the root.
211  // Candidates includes any block 'BB' in set 'BBs' that is not strictly
212  // dominated by any other blocks in set 'BBs', and all nodes in the path
213  // in the dominator tree from Entry to 'BB'.
215  for (auto BB : BBs) {
216  // Ignore unreachable basic blocks.
217  if (!DT.isReachableFromEntry(BB))
218  continue;
219  Path.clear();
220  // Walk up the dominator tree until Entry or another BB in BBs
221  // is reached. Insert the nodes on the way to the Path.
222  BasicBlock *Node = BB;
223  // The "Path" is a candidate path to be added into Candidates set.
224  bool isCandidate = false;
225  do {
226  Path.insert(Node);
227  if (Node == Entry || Candidates.count(Node)) {
228  isCandidate = true;
229  break;
230  }
231  assert(DT.getNode(Node)->getIDom() &&
232  "Entry doens't dominate current Node");
233  Node = DT.getNode(Node)->getIDom()->getBlock();
234  } while (!BBs.count(Node));
235 
236  // If isCandidate is false, Node is another Block in BBs dominating
237  // current 'BB'. Drop the nodes on the Path.
238  if (!isCandidate)
239  continue;
240 
241  // Add nodes on the Path into Candidates.
242  Candidates.insert(Path.begin(), Path.end());
243  }
244 
245  // Sort the nodes in Candidates in top-down order and save the nodes
246  // in Orders.
247  unsigned Idx = 0;
249  Orders.push_back(Entry);
250  while (Idx != Orders.size()) {
251  BasicBlock *Node = Orders[Idx++];
252  for (auto ChildDomNode : DT.getNode(Node)->getChildren()) {
253  if (Candidates.count(ChildDomNode->getBlock()))
254  Orders.push_back(ChildDomNode->getBlock());
255  }
256  }
257 
258  // Visit Orders in bottom-up order.
259  using InsertPtsCostPair =
260  std::pair<SetVector<BasicBlock *>, BlockFrequency>;
261 
262  // InsertPtsMap is a map from a BB to the best insertion points for the
263  // subtree of BB (subtree not including the BB itself).
265  InsertPtsMap.reserve(Orders.size() + 1);
266  for (auto RIt = Orders.rbegin(); RIt != Orders.rend(); RIt++) {
267  BasicBlock *Node = *RIt;
268  bool NodeInBBs = BBs.count(Node);
269  auto &InsertPts = InsertPtsMap[Node].first;
270  BlockFrequency &InsertPtsFreq = InsertPtsMap[Node].second;
271 
272  // Return the optimal insert points in BBs.
273  if (Node == Entry) {
274  BBs.clear();
275  if (InsertPtsFreq > BFI.getBlockFreq(Node) ||
276  (InsertPtsFreq == BFI.getBlockFreq(Node) && InsertPts.size() > 1))
277  BBs.insert(Entry);
278  else
279  BBs.insert(InsertPts.begin(), InsertPts.end());
280  break;
281  }
282 
283  BasicBlock *Parent = DT.getNode(Node)->getIDom()->getBlock();
284  // Initially, ParentInsertPts is empty and ParentPtsFreq is 0. Every child
285  // will update its parent's ParentInsertPts and ParentPtsFreq.
286  auto &ParentInsertPts = InsertPtsMap[Parent].first;
287  BlockFrequency &ParentPtsFreq = InsertPtsMap[Parent].second;
288  // Choose to insert in Node or in subtree of Node.
289  // Don't hoist to EHPad because we may not find a proper place to insert
290  // in EHPad.
291  // If the total frequency of InsertPts is the same as the frequency of the
292  // target Node, and InsertPts contains more than one nodes, choose hoisting
293  // to reduce code size.
294  if (NodeInBBs ||
295  (!Node->isEHPad() &&
296  (InsertPtsFreq > BFI.getBlockFreq(Node) ||
297  (InsertPtsFreq == BFI.getBlockFreq(Node) && InsertPts.size() > 1)))) {
298  ParentInsertPts.insert(Node);
299  ParentPtsFreq += BFI.getBlockFreq(Node);
300  } else {
301  ParentInsertPts.insert(InsertPts.begin(), InsertPts.end());
302  ParentPtsFreq += InsertPtsFreq;
303  }
304  }
305 }
306 
307 /// Find an insertion point that dominates all uses.
308 SetVector<Instruction *> ConstantHoistingPass::findConstantInsertionPoint(
309  const ConstantInfo &ConstInfo) const {
310  assert(!ConstInfo.RebasedConstants.empty() && "Invalid constant info entry.");
311  // Collect all basic blocks.
313  SetVector<Instruction *> InsertPts;
314  for (auto const &RCI : ConstInfo.RebasedConstants)
315  for (auto const &U : RCI.Uses)
316  BBs.insert(findMatInsertPt(U.Inst, U.OpndIdx)->getParent());
317 
318  if (BBs.count(Entry)) {
319  InsertPts.insert(&Entry->front());
320  return InsertPts;
321  }
322 
323  if (BFI) {
324  findBestInsertionSet(*DT, *BFI, Entry, BBs);
325  for (auto BB : BBs) {
326  BasicBlock::iterator InsertPt = BB->begin();
327  for (; isa<PHINode>(InsertPt) || InsertPt->isEHPad(); ++InsertPt)
328  ;
329  InsertPts.insert(&*InsertPt);
330  }
331  return InsertPts;
332  }
333 
334  while (BBs.size() >= 2) {
335  BasicBlock *BB, *BB1, *BB2;
336  BB1 = BBs.pop_back_val();
337  BB2 = BBs.pop_back_val();
338  BB = DT->findNearestCommonDominator(BB1, BB2);
339  if (BB == Entry) {
340  InsertPts.insert(&Entry->front());
341  return InsertPts;
342  }
343  BBs.insert(BB);
344  }
345  assert((BBs.size() == 1) && "Expected only one element.");
346  Instruction &FirstInst = (*BBs.begin())->front();
347  InsertPts.insert(findMatInsertPt(&FirstInst));
348  return InsertPts;
349 }
350 
351 /// Record constant integer ConstInt for instruction Inst at operand
352 /// index Idx.
353 ///
354 /// The operand at index Idx is not necessarily the constant integer itself. It
355 /// could also be a cast instruction or a constant expression that uses the
356 /// constant integer.
357 void ConstantHoistingPass::collectConstantCandidates(
358  ConstCandMapType &ConstCandMap, Instruction *Inst, unsigned Idx,
359  ConstantInt *ConstInt) {
360  unsigned Cost;
361  // Ask the target about the cost of materializing the constant for the given
362  // instruction and operand index.
363  if (auto IntrInst = dyn_cast<IntrinsicInst>(Inst))
364  Cost = TTI->getIntImmCost(IntrInst->getIntrinsicID(), Idx,
365  ConstInt->getValue(), ConstInt->getType());
366  else
367  Cost = TTI->getIntImmCost(Inst->getOpcode(), Idx, ConstInt->getValue(),
368  ConstInt->getType());
369 
370  // Ignore cheap integer constants.
371  if (Cost > TargetTransformInfo::TCC_Basic) {
372  ConstCandMapType::iterator Itr;
373  bool Inserted;
374  ConstPtrUnionType Cand = ConstInt;
375  std::tie(Itr, Inserted) = ConstCandMap.insert(std::make_pair(Cand, 0));
376  if (Inserted) {
377  ConstIntCandVec.push_back(ConstantCandidate(ConstInt));
378  Itr->second = ConstIntCandVec.size() - 1;
379  }
380  ConstIntCandVec[Itr->second].addUser(Inst, Idx, Cost);
381  LLVM_DEBUG(if (isa<ConstantInt>(Inst->getOperand(Idx))) dbgs()
382  << "Collect constant " << *ConstInt << " from " << *Inst
383  << " with cost " << Cost << '\n';
384  else dbgs() << "Collect constant " << *ConstInt
385  << " indirectly from " << *Inst << " via "
386  << *Inst->getOperand(Idx) << " with cost " << Cost
387  << '\n';);
388  }
389 }
390 
391 /// Record constant GEP expression for instruction Inst at operand index Idx.
392 void ConstantHoistingPass::collectConstantCandidates(
393  ConstCandMapType &ConstCandMap, Instruction *Inst, unsigned Idx,
394  ConstantExpr *ConstExpr) {
395  // TODO: Handle vector GEPs
396  if (ConstExpr->getType()->isVectorTy())
397  return;
398 
399  GlobalVariable *BaseGV = dyn_cast<GlobalVariable>(ConstExpr->getOperand(0));
400  if (!BaseGV)
401  return;
402 
403  // Get offset from the base GV.
404  PointerType *GVPtrTy = dyn_cast<PointerType>(BaseGV->getType());
405  IntegerType *PtrIntTy = DL->getIntPtrType(*Ctx, GVPtrTy->getAddressSpace());
406  APInt Offset(DL->getTypeSizeInBits(PtrIntTy), /*val*/0, /*isSigned*/true);
407  auto *GEPO = cast<GEPOperator>(ConstExpr);
408  if (!GEPO->accumulateConstantOffset(*DL, Offset))
409  return;
410 
411  if (!Offset.isIntN(32))
412  return;
413 
414  // A constant GEP expression that has a GlobalVariable as base pointer is
415  // usually lowered to a load from constant pool. Such operation is unlikely
416  // to be cheaper than compute it by <Base + Offset>, which can be lowered to
417  // an ADD instruction or folded into Load/Store instruction.
418  int Cost = TTI->getIntImmCost(Instruction::Add, 1, Offset, PtrIntTy);
419  ConstCandVecType &ExprCandVec = ConstGEPCandMap[BaseGV];
420  ConstCandMapType::iterator Itr;
421  bool Inserted;
422  ConstPtrUnionType Cand = ConstExpr;
423  std::tie(Itr, Inserted) = ConstCandMap.insert(std::make_pair(Cand, 0));
424  if (Inserted) {
425  ExprCandVec.push_back(ConstantCandidate(
426  ConstantInt::get(Type::getInt32Ty(*Ctx), Offset.getLimitedValue()),
427  ConstExpr));
428  Itr->second = ExprCandVec.size() - 1;
429  }
430  ExprCandVec[Itr->second].addUser(Inst, Idx, Cost);
431 }
432 
433 /// Check the operand for instruction Inst at index Idx.
434 void ConstantHoistingPass::collectConstantCandidates(
435  ConstCandMapType &ConstCandMap, Instruction *Inst, unsigned Idx) {
436  Value *Opnd = Inst->getOperand(Idx);
437 
438  // Visit constant integers.
439  if (auto ConstInt = dyn_cast<ConstantInt>(Opnd)) {
440  collectConstantCandidates(ConstCandMap, Inst, Idx, ConstInt);
441  return;
442  }
443 
444  // Visit cast instructions that have constant integers.
445  if (auto CastInst = dyn_cast<Instruction>(Opnd)) {
446  // Only visit cast instructions, which have been skipped. All other
447  // instructions should have already been visited.
448  if (!CastInst->isCast())
449  return;
450 
451  if (auto *ConstInt = dyn_cast<ConstantInt>(CastInst->getOperand(0))) {
452  // Pretend the constant is directly used by the instruction and ignore
453  // the cast instruction.
454  collectConstantCandidates(ConstCandMap, Inst, Idx, ConstInt);
455  return;
456  }
457  }
458 
459  // Visit constant expressions that have constant integers.
460  if (auto ConstExpr = dyn_cast<ConstantExpr>(Opnd)) {
461  // Handle constant gep expressions.
463  collectConstantCandidates(ConstCandMap, Inst, Idx, ConstExpr);
464 
465  // Only visit constant cast expressions.
466  if (!ConstExpr->isCast())
467  return;
468 
469  if (auto ConstInt = dyn_cast<ConstantInt>(ConstExpr->getOperand(0))) {
470  // Pretend the constant is directly used by the instruction and ignore
471  // the constant expression.
472  collectConstantCandidates(ConstCandMap, Inst, Idx, ConstInt);
473  return;
474  }
475  }
476 }
477 
478 /// Scan the instruction for expensive integer constants and record them
479 /// in the constant candidate vector.
480 void ConstantHoistingPass::collectConstantCandidates(
481  ConstCandMapType &ConstCandMap, Instruction *Inst) {
482  // Skip all cast instructions. They are visited indirectly later on.
483  if (Inst->isCast())
484  return;
485 
486  // Scan all operands.
487  for (unsigned Idx = 0, E = Inst->getNumOperands(); Idx != E; ++Idx) {
488  // The cost of materializing the constants (defined in
489  // `TargetTransformInfo::getIntImmCost`) for instructions which only take
490  // constant variables is lower than `TargetTransformInfo::TCC_Basic`. So
491  // it's safe for us to collect constant candidates from all IntrinsicInsts.
492  if (canReplaceOperandWithVariable(Inst, Idx) || isa<IntrinsicInst>(Inst)) {
493  collectConstantCandidates(ConstCandMap, Inst, Idx);
494  }
495  } // end of for all operands
496 }
497 
498 /// Collect all integer constants in the function that cannot be folded
499 /// into an instruction itself.
500 void ConstantHoistingPass::collectConstantCandidates(Function &Fn) {
501  ConstCandMapType ConstCandMap;
502  for (BasicBlock &BB : Fn)
503  for (Instruction &Inst : BB)
504  collectConstantCandidates(ConstCandMap, &Inst);
505 }
506 
507 // This helper function is necessary to deal with values that have different
508 // bit widths (APInt Operator- does not like that). If the value cannot be
509 // represented in uint64 we return an "empty" APInt. This is then interpreted
510 // as the value is not in range.
511 static Optional<APInt> calculateOffsetDiff(const APInt &V1, const APInt &V2) {
512  Optional<APInt> Res = None;
513  unsigned BW = V1.getBitWidth() > V2.getBitWidth() ?
514  V1.getBitWidth() : V2.getBitWidth();
515  uint64_t LimVal1 = V1.getLimitedValue();
516  uint64_t LimVal2 = V2.getLimitedValue();
517 
518  if (LimVal1 == ~0ULL || LimVal2 == ~0ULL)
519  return Res;
520 
521  uint64_t Diff = LimVal1 - LimVal2;
522  return APInt(BW, Diff, true);
523 }
524 
525 // From a list of constants, one needs to picked as the base and the other
526 // constants will be transformed into an offset from that base constant. The
527 // question is which we can pick best? For example, consider these constants
528 // and their number of uses:
529 //
530 // Constants| 2 | 4 | 12 | 42 |
531 // NumUses | 3 | 2 | 8 | 7 |
532 //
533 // Selecting constant 12 because it has the most uses will generate negative
534 // offsets for constants 2 and 4 (i.e. -10 and -8 respectively). If negative
535 // offsets lead to less optimal code generation, then there might be better
536 // solutions. Suppose immediates in the range of 0..35 are most optimally
537 // supported by the architecture, then selecting constant 2 is most optimal
538 // because this will generate offsets: 0, 2, 10, 40. Offsets 0, 2 and 10 are in
539 // range 0..35, and thus 3 + 2 + 8 = 13 uses are in range. Selecting 12 would
540 // have only 8 uses in range, so choosing 2 as a base is more optimal. Thus, in
541 // selecting the base constant the range of the offsets is a very important
542 // factor too that we take into account here. This algorithm calculates a total
543 // costs for selecting a constant as the base and substract the costs if
544 // immediates are out of range. It has quadratic complexity, so we call this
545 // function only when we're optimising for size and there are less than 100
546 // constants, we fall back to the straightforward algorithm otherwise
547 // which does not do all the offset calculations.
548 unsigned
549 ConstantHoistingPass::maximizeConstantsInRange(ConstCandVecType::iterator S,
550  ConstCandVecType::iterator E,
551  ConstCandVecType::iterator &MaxCostItr) {
552  unsigned NumUses = 0;
553 
554  bool OptForSize = Entry->getParent()->hasOptSize() ||
555  llvm::shouldOptimizeForSize(Entry->getParent(), PSI, BFI);
556  if (!OptForSize || std::distance(S,E) > 100) {
557  for (auto ConstCand = S; ConstCand != E; ++ConstCand) {
558  NumUses += ConstCand->Uses.size();
559  if (ConstCand->CumulativeCost > MaxCostItr->CumulativeCost)
560  MaxCostItr = ConstCand;
561  }
562  return NumUses;
563  }
564 
565  LLVM_DEBUG(dbgs() << "== Maximize constants in range ==\n");
566  int MaxCost = -1;
567  for (auto ConstCand = S; ConstCand != E; ++ConstCand) {
568  auto Value = ConstCand->ConstInt->getValue();
569  Type *Ty = ConstCand->ConstInt->getType();
570  int Cost = 0;
571  NumUses += ConstCand->Uses.size();
572  LLVM_DEBUG(dbgs() << "= Constant: " << ConstCand->ConstInt->getValue()
573  << "\n");
574 
575  for (auto User : ConstCand->Uses) {
576  unsigned Opcode = User.Inst->getOpcode();
577  unsigned OpndIdx = User.OpndIdx;
578  Cost += TTI->getIntImmCost(Opcode, OpndIdx, Value, Ty);
579  LLVM_DEBUG(dbgs() << "Cost: " << Cost << "\n");
580 
581  for (auto C2 = S; C2 != E; ++C2) {
583  C2->ConstInt->getValue(),
584  ConstCand->ConstInt->getValue());
585  if (Diff) {
586  const int ImmCosts =
587  TTI->getIntImmCodeSizeCost(Opcode, OpndIdx, Diff.getValue(), Ty);
588  Cost -= ImmCosts;
589  LLVM_DEBUG(dbgs() << "Offset " << Diff.getValue() << " "
590  << "has penalty: " << ImmCosts << "\n"
591  << "Adjusted cost: " << Cost << "\n");
592  }
593  }
594  }
595  LLVM_DEBUG(dbgs() << "Cumulative cost: " << Cost << "\n");
596  if (Cost > MaxCost) {
597  MaxCost = Cost;
598  MaxCostItr = ConstCand;
599  LLVM_DEBUG(dbgs() << "New candidate: " << MaxCostItr->ConstInt->getValue()
600  << "\n");
601  }
602  }
603  return NumUses;
604 }
605 
606 /// Find the base constant within the given range and rebase all other
607 /// constants with respect to the base constant.
608 void ConstantHoistingPass::findAndMakeBaseConstant(
609  ConstCandVecType::iterator S, ConstCandVecType::iterator E,
611  auto MaxCostItr = S;
612  unsigned NumUses = maximizeConstantsInRange(S, E, MaxCostItr);
613 
614  // Don't hoist constants that have only one use.
615  if (NumUses <= 1)
616  return;
617 
618  ConstantInt *ConstInt = MaxCostItr->ConstInt;
619  ConstantExpr *ConstExpr = MaxCostItr->ConstExpr;
620  ConstantInfo ConstInfo;
621  ConstInfo.BaseInt = ConstInt;
622  ConstInfo.BaseExpr = ConstExpr;
623  Type *Ty = ConstInt->getType();
624 
625  // Rebase the constants with respect to the base constant.
626  for (auto ConstCand = S; ConstCand != E; ++ConstCand) {
627  APInt Diff = ConstCand->ConstInt->getValue() - ConstInt->getValue();
628  Constant *Offset = Diff == 0 ? nullptr : ConstantInt::get(Ty, Diff);
629  Type *ConstTy =
630  ConstCand->ConstExpr ? ConstCand->ConstExpr->getType() : nullptr;
631  ConstInfo.RebasedConstants.push_back(
632  RebasedConstantInfo(std::move(ConstCand->Uses), Offset, ConstTy));
633  }
634  ConstInfoVec.push_back(std::move(ConstInfo));
635 }
636 
637 /// Finds and combines constant candidates that can be easily
638 /// rematerialized with an add from a common base constant.
639 void ConstantHoistingPass::findBaseConstants(GlobalVariable *BaseGV) {
640  // If BaseGV is nullptr, find base among candidate constant integers;
641  // Otherwise find base among constant GEPs that share the same BaseGV.
642  ConstCandVecType &ConstCandVec = BaseGV ?
643  ConstGEPCandMap[BaseGV] : ConstIntCandVec;
644  ConstInfoVecType &ConstInfoVec = BaseGV ?
645  ConstGEPInfoMap[BaseGV] : ConstIntInfoVec;
646 
647  // Sort the constants by value and type. This invalidates the mapping!
648  llvm::stable_sort(ConstCandVec, [](const ConstantCandidate &LHS,
649  const ConstantCandidate &RHS) {
650  if (LHS.ConstInt->getType() != RHS.ConstInt->getType())
651  return LHS.ConstInt->getType()->getBitWidth() <
652  RHS.ConstInt->getType()->getBitWidth();
653  return LHS.ConstInt->getValue().ult(RHS.ConstInt->getValue());
654  });
655 
656  // Simple linear scan through the sorted constant candidate vector for viable
657  // merge candidates.
658  auto MinValItr = ConstCandVec.begin();
659  for (auto CC = std::next(ConstCandVec.begin()), E = ConstCandVec.end();
660  CC != E; ++CC) {
661  if (MinValItr->ConstInt->getType() == CC->ConstInt->getType()) {
662  Type *MemUseValTy = nullptr;
663  for (auto &U : CC->Uses) {
664  auto *UI = U.Inst;
665  if (LoadInst *LI = dyn_cast<LoadInst>(UI)) {
666  MemUseValTy = LI->getType();
667  break;
668  } else if (StoreInst *SI = dyn_cast<StoreInst>(UI)) {
669  // Make sure the constant is used as pointer operand of the StoreInst.
670  if (SI->getPointerOperand() == SI->getOperand(U.OpndIdx)) {
671  MemUseValTy = SI->getValueOperand()->getType();
672  break;
673  }
674  }
675  }
676 
677  // Check if the constant is in range of an add with immediate.
678  APInt Diff = CC->ConstInt->getValue() - MinValItr->ConstInt->getValue();
679  if ((Diff.getBitWidth() <= 64) &&
680  TTI->isLegalAddImmediate(Diff.getSExtValue()) &&
681  // Check if Diff can be used as offset in addressing mode of the user
682  // memory instruction.
683  (!MemUseValTy || TTI->isLegalAddressingMode(MemUseValTy,
684  /*BaseGV*/nullptr, /*BaseOffset*/Diff.getSExtValue(),
685  /*HasBaseReg*/true, /*Scale*/0)))
686  continue;
687  }
688  // We either have now a different constant type or the constant is not in
689  // range of an add with immediate anymore.
690  findAndMakeBaseConstant(MinValItr, CC, ConstInfoVec);
691  // Start a new base constant search.
692  MinValItr = CC;
693  }
694  // Finalize the last base constant search.
695  findAndMakeBaseConstant(MinValItr, ConstCandVec.end(), ConstInfoVec);
696 }
697 
698 /// Updates the operand at Idx in instruction Inst with the result of
699 /// instruction Mat. If the instruction is a PHI node then special
700 /// handling for duplicate values form the same incoming basic block is
701 /// required.
702 /// \return The update will always succeed, but the return value indicated if
703 /// Mat was used for the update or not.
704 static bool updateOperand(Instruction *Inst, unsigned Idx, Instruction *Mat) {
705  if (auto PHI = dyn_cast<PHINode>(Inst)) {
706  // Check if any previous operand of the PHI node has the same incoming basic
707  // block. This is a very odd case that happens when the incoming basic block
708  // has a switch statement. In this case use the same value as the previous
709  // operand(s), otherwise we will fail verification due to different values.
710  // The values are actually the same, but the variable names are different
711  // and the verifier doesn't like that.
712  BasicBlock *IncomingBB = PHI->getIncomingBlock(Idx);
713  for (unsigned i = 0; i < Idx; ++i) {
714  if (PHI->getIncomingBlock(i) == IncomingBB) {
715  Value *IncomingVal = PHI->getIncomingValue(i);
716  Inst->setOperand(Idx, IncomingVal);
717  return false;
718  }
719  }
720  }
721 
722  Inst->setOperand(Idx, Mat);
723  return true;
724 }
725 
726 /// Emit materialization code for all rebased constants and update their
727 /// users.
728 void ConstantHoistingPass::emitBaseConstants(Instruction *Base,
729  Constant *Offset,
730  Type *Ty,
731  const ConstantUser &ConstUser) {
732  Instruction *Mat = Base;
733 
734  // The same offset can be dereferenced to different types in nested struct.
735  if (!Offset && Ty && Ty != Base->getType())
736  Offset = ConstantInt::get(Type::getInt32Ty(*Ctx), 0);
737 
738  if (Offset) {
739  Instruction *InsertionPt = findMatInsertPt(ConstUser.Inst,
740  ConstUser.OpndIdx);
741  if (Ty) {
742  // Constant being rebased is a ConstantExpr.
743  PointerType *Int8PtrTy = Type::getInt8PtrTy(*Ctx,
744  cast<PointerType>(Ty)->getAddressSpace());
745  Base = new BitCastInst(Base, Int8PtrTy, "base_bitcast", InsertionPt);
746  Mat = GetElementPtrInst::Create(Int8PtrTy->getElementType(), Base,
747  Offset, "mat_gep", InsertionPt);
748  Mat = new BitCastInst(Mat, Ty, "mat_bitcast", InsertionPt);
749  } else
750  // Constant being rebased is a ConstantInt.
751  Mat = BinaryOperator::Create(Instruction::Add, Base, Offset,
752  "const_mat", InsertionPt);
753 
754  LLVM_DEBUG(dbgs() << "Materialize constant (" << *Base->getOperand(0)
755  << " + " << *Offset << ") in BB "
756  << Mat->getParent()->getName() << '\n'
757  << *Mat << '\n');
758  Mat->setDebugLoc(ConstUser.Inst->getDebugLoc());
759  }
760  Value *Opnd = ConstUser.Inst->getOperand(ConstUser.OpndIdx);
761 
762  // Visit constant integer.
763  if (isa<ConstantInt>(Opnd)) {
764  LLVM_DEBUG(dbgs() << "Update: " << *ConstUser.Inst << '\n');
765  if (!updateOperand(ConstUser.Inst, ConstUser.OpndIdx, Mat) && Offset)
766  Mat->eraseFromParent();
767  LLVM_DEBUG(dbgs() << "To : " << *ConstUser.Inst << '\n');
768  return;
769  }
770 
771  // Visit cast instruction.
772  if (auto CastInst = dyn_cast<Instruction>(Opnd)) {
773  assert(CastInst->isCast() && "Expected an cast instruction!");
774  // Check if we already have visited this cast instruction before to avoid
775  // unnecessary cloning.
776  Instruction *&ClonedCastInst = ClonedCastMap[CastInst];
777  if (!ClonedCastInst) {
778  ClonedCastInst = CastInst->clone();
779  ClonedCastInst->setOperand(0, Mat);
780  ClonedCastInst->insertAfter(CastInst);
781  // Use the same debug location as the original cast instruction.
782  ClonedCastInst->setDebugLoc(CastInst->getDebugLoc());
783  LLVM_DEBUG(dbgs() << "Clone instruction: " << *CastInst << '\n'
784  << "To : " << *ClonedCastInst << '\n');
785  }
786 
787  LLVM_DEBUG(dbgs() << "Update: " << *ConstUser.Inst << '\n');
788  updateOperand(ConstUser.Inst, ConstUser.OpndIdx, ClonedCastInst);
789  LLVM_DEBUG(dbgs() << "To : " << *ConstUser.Inst << '\n');
790  return;
791  }
792 
793  // Visit constant expression.
794  if (auto ConstExpr = dyn_cast<ConstantExpr>(Opnd)) {
795  if (ConstExpr->isGEPWithNoNotionalOverIndexing()) {
796  // Operand is a ConstantGEP, replace it.
797  updateOperand(ConstUser.Inst, ConstUser.OpndIdx, Mat);
798  return;
799  }
800 
801  // Aside from constant GEPs, only constant cast expressions are collected.
802  assert(ConstExpr->isCast() && "ConstExpr should be a cast");
803  Instruction *ConstExprInst = ConstExpr->getAsInstruction();
804  ConstExprInst->setOperand(0, Mat);
805  ConstExprInst->insertBefore(findMatInsertPt(ConstUser.Inst,
806  ConstUser.OpndIdx));
807 
808  // Use the same debug location as the instruction we are about to update.
809  ConstExprInst->setDebugLoc(ConstUser.Inst->getDebugLoc());
810 
811  LLVM_DEBUG(dbgs() << "Create instruction: " << *ConstExprInst << '\n'
812  << "From : " << *ConstExpr << '\n');
813  LLVM_DEBUG(dbgs() << "Update: " << *ConstUser.Inst << '\n');
814  if (!updateOperand(ConstUser.Inst, ConstUser.OpndIdx, ConstExprInst)) {
815  ConstExprInst->eraseFromParent();
816  if (Offset)
817  Mat->eraseFromParent();
818  }
819  LLVM_DEBUG(dbgs() << "To : " << *ConstUser.Inst << '\n');
820  return;
821  }
822 }
823 
824 /// Hoist and hide the base constant behind a bitcast and emit
825 /// materialization code for derived constants.
826 bool ConstantHoistingPass::emitBaseConstants(GlobalVariable *BaseGV) {
827  bool MadeChange = false;
829  BaseGV ? ConstGEPInfoMap[BaseGV] : ConstIntInfoVec;
830  for (auto const &ConstInfo : ConstInfoVec) {
831  SetVector<Instruction *> IPSet = findConstantInsertionPoint(ConstInfo);
832  // We can have an empty set if the function contains unreachable blocks.
833  if (IPSet.empty())
834  continue;
835 
836  unsigned UsesNum = 0;
837  unsigned ReBasesNum = 0;
838  unsigned NotRebasedNum = 0;
839  for (Instruction *IP : IPSet) {
840  // First, collect constants depending on this IP of the base.
841  unsigned Uses = 0;
842  using RebasedUse = std::tuple<Constant *, Type *, ConstantUser>;
843  SmallVector<RebasedUse, 4> ToBeRebased;
844  for (auto const &RCI : ConstInfo.RebasedConstants) {
845  for (auto const &U : RCI.Uses) {
846  Uses++;
847  BasicBlock *OrigMatInsertBB =
848  findMatInsertPt(U.Inst, U.OpndIdx)->getParent();
849  // If Base constant is to be inserted in multiple places,
850  // generate rebase for U using the Base dominating U.
851  if (IPSet.size() == 1 ||
852  DT->dominates(IP->getParent(), OrigMatInsertBB))
853  ToBeRebased.push_back(RebasedUse(RCI.Offset, RCI.Ty, U));
854  }
855  }
856  UsesNum = Uses;
857 
858  // If only few constants depend on this IP of base, skip rebasing,
859  // assuming the base and the rebased have the same materialization cost.
860  if (ToBeRebased.size() < MinNumOfDependentToRebase) {
861  NotRebasedNum += ToBeRebased.size();
862  continue;
863  }
864 
865  // Emit an instance of the base at this IP.
866  Instruction *Base = nullptr;
867  // Hoist and hide the base constant behind a bitcast.
868  if (ConstInfo.BaseExpr) {
869  assert(BaseGV && "A base constant expression must have an base GV");
870  Type *Ty = ConstInfo.BaseExpr->getType();
871  Base = new BitCastInst(ConstInfo.BaseExpr, Ty, "const", IP);
872  } else {
873  IntegerType *Ty = ConstInfo.BaseInt->getType();
874  Base = new BitCastInst(ConstInfo.BaseInt, Ty, "const", IP);
875  }
876 
877  Base->setDebugLoc(IP->getDebugLoc());
878 
879  LLVM_DEBUG(dbgs() << "Hoist constant (" << *ConstInfo.BaseInt
880  << ") to BB " << IP->getParent()->getName() << '\n'
881  << *Base << '\n');
882 
883  // Emit materialization code for rebased constants depending on this IP.
884  for (auto const &R : ToBeRebased) {
885  Constant *Off = std::get<0>(R);
886  Type *Ty = std::get<1>(R);
887  ConstantUser U = std::get<2>(R);
888  emitBaseConstants(Base, Off, Ty, U);
889  ReBasesNum++;
890  // Use the same debug location as the last user of the constant.
892  Base->getDebugLoc(), U.Inst->getDebugLoc()));
893  }
894  assert(!Base->use_empty() && "The use list is empty!?");
895  assert(isa<Instruction>(Base->user_back()) &&
896  "All uses should be instructions.");
897  }
898  (void)UsesNum;
899  (void)ReBasesNum;
900  (void)NotRebasedNum;
901  // Expect all uses are rebased after rebase is done.
902  assert(UsesNum == (ReBasesNum + NotRebasedNum) &&
903  "Not all uses are rebased");
904 
905  NumConstantsHoisted++;
906 
907  // Base constant is also included in ConstInfo.RebasedConstants, so
908  // deduct 1 from ConstInfo.RebasedConstants.size().
909  NumConstantsRebased += ConstInfo.RebasedConstants.size() - 1;
910 
911  MadeChange = true;
912  }
913  return MadeChange;
914 }
915 
916 /// Check all cast instructions we made a copy of and remove them if they
917 /// have no more users.
918 void ConstantHoistingPass::deleteDeadCastInst() const {
919  for (auto const &I : ClonedCastMap)
920  if (I.first->use_empty())
921  I.first->eraseFromParent();
922 }
923 
924 /// Optimize expensive integer constants in the given function.
928  this->TTI = &TTI;
929  this->DT = &DT;
930  this->BFI = BFI;
931  this->DL = &Fn.getParent()->getDataLayout();
932  this->Ctx = &Fn.getContext();
933  this->Entry = &Entry;
934  this->PSI = PSI;
935  // Collect all constant candidates.
936  collectConstantCandidates(Fn);
937 
938  // Combine constants that can be easily materialized with an add from a common
939  // base constant.
940  if (!ConstIntCandVec.empty())
941  findBaseConstants(nullptr);
942  for (auto &MapEntry : ConstGEPCandMap)
943  if (!MapEntry.second.empty())
944  findBaseConstants(MapEntry.first);
945 
946  // Finally hoist the base constant and emit materialization code for dependent
947  // constants.
948  bool MadeChange = false;
949  if (!ConstIntInfoVec.empty())
950  MadeChange = emitBaseConstants(nullptr);
951  for (auto MapEntry : ConstGEPInfoMap)
952  if (!MapEntry.second.empty())
953  MadeChange |= emitBaseConstants(MapEntry.first);
954 
955 
956  // Cleanup dead instructions.
957  deleteDeadCastInst();
958 
959  cleanup();
960 
961  return MadeChange;
962 }
963 
966  auto &DT = AM.getResult<DominatorTreeAnalysis>(F);
967  auto &TTI = AM.getResult<TargetIRAnalysis>(F);
970  : nullptr;
971  auto &MAM = AM.getResult<ModuleAnalysisManagerFunctionProxy>(F).getManager();
972  auto *PSI = MAM.getCachedResult<ProfileSummaryAnalysis>(*F.getParent());
973  if (!runImpl(F, TTI, DT, BFI, F.getEntryBlock(), PSI))
974  return PreservedAnalyses::all();
975 
977  PA.preserveSet<CFGAnalyses>();
978  return PA;
979 }
const NoneType None
Definition: None.h:23
SymbolTableList< Instruction >::iterator eraseFromParent()
This method unlinks &#39;this&#39; from the containing basic block and deletes it.
Definition: Instruction.cpp:67
IntegerType * getType() const
getType - Specialize the getType() method to always return an IntegerType, which reduces the amount o...
Definition: Constants.h:171
static bool runImpl(Function &F, TargetLibraryInfo &TLI, DominatorTree &DT)
This is the entry point for all transforms.
INITIALIZE_PASS_BEGIN(ConstantHoistingLegacyPass, "consthoist", "Constant Hoisting", false, false) INITIALIZE_PASS_END(ConstantHoistingLegacyPass
static PassRegistry * getPassRegistry()
getPassRegistry - Access the global registry object, which is automatically initialized at applicatio...
A base constant and all its rebased constants.
PassT::Result & getResult(IRUnitT &IR, ExtraArgTs... ExtraArgs)
Get the result of an analysis pass for a given IR unit.
Definition: PassManager.h:776
This class represents lattice values for constants.
Definition: AllocatorList.h:23
void initializeConstantHoistingLegacyPassPass(PassRegistry &)
static const DILocation * getMergedLocation(const DILocation *LocA, const DILocation *LocB)
When two instructions are combined into a single instruction we also need to combine the original loc...
Analysis providing profile information.
static GetElementPtrInst * Create(Type *PointeeType, Value *Ptr, ArrayRef< Value *> IdxList, const Twine &NameStr="", Instruction *InsertBefore=nullptr)
Definition: Instructions.h:901
Keeps track of a constant candidate and its uses.
Analysis pass providing the TargetTransformInfo.
static bool updateOperand(Instruction *Inst, unsigned Idx, Instruction *Mat)
Updates the operand at Idx in instruction Inst with the result of instruction Mat.
static cl::opt< unsigned > MinNumOfDependentToRebase("consthoist-min-num-to-rebase", cl::desc("Do not rebase if number of dependent constants of a Base is less " "than this number."), cl::init(0), cl::Hidden)
STATISTIC(NumFunctions, "Total number of functions")
Analysis pass which computes a DominatorTree.
Definition: Dominators.h:230
F(f)
static void cleanup(BlockFrequencyInfoImplBase &BFI)
Clear all memory not needed downstream.
An instruction for reading from memory.
Definition: Instructions.h:167
bool isVectorTy() const
True if this is an instance of VectorType.
Definition: Type.h:229
bool shouldOptimizeForSize(Function *F, ProfileSummaryInfo *PSI, BlockFrequencyInfo *BFI)
Returns true if function F is suggested to be size-optimized base on the profile. ...
Definition: SizeOpts.cpp:23
bool isReachableFromEntry(const Use &U) const
Provide an overload for a Use.
Definition: Dominators.cpp:299
This represents a constant that has been rebased with respect to a base constant. ...
unsigned getBitWidth() const
Return the number of bits in the APInt.
Definition: APInt.h:1517
std::pair< iterator, bool > insert(const std::pair< KeyT, ValueT > &KV)
Definition: DenseMap.h:195
AnalysisUsage & addRequired()
#define INITIALIZE_PASS_DEPENDENCY(depName)
Definition: PassSupport.h:50
const DataLayout & getDataLayout() const
Get the data layout for the module&#39;s target platform.
Definition: Module.cpp:369
An analysis pass based on legacy pass manager to deliver ProfileSummaryInfo.
This is the base class for all instructions that perform data casts.
Definition: InstrTypes.h:439
Constant Hoisting
static cl::opt< bool > ConstHoistGEP("consthoist-gep", cl::init(false), cl::Hidden, cl::desc("Try hoisting constant gep expressions"))
Legacy analysis pass which computes BlockFrequencyInfo.
Instruction * getAsInstruction()
Returns an Instruction which implements the same operation as this ConstantExpr.
Definition: Constants.cpp:2985
This file implements a class to represent arbitrary precision integral constant values and operations...
Instruction * clone() const
Create a copy of &#39;this&#39; instruction that is identical in all ways except the following: ...
A constant value that is initialized with an expression using other constant values.
Definition: Constants.h:888
int64_t getSExtValue() const
Get sign extended value.
Definition: APInt.h:1583
Type * getType() const
All values are typed, get the type of this value.
Definition: Value.h:245
bool insert(const value_type &X)
Insert a new element into the SetVector.
Definition: SetVector.h:141
const T & getValue() const LLVM_LVALUE_FUNCTION
Definition: Optional.h:255
This class represents a no-op cast from one type to another.
const std::vector< DomTreeNodeBase * > & getChildren() const
const APInt & getValue() const
Return the constant as an APInt value reference.
Definition: Constants.h:137
bool isGEPWithNoNotionalOverIndexing() const
Return true if this is a getelementptr expression and all the index operands are compile-time known i...
Definition: Constants.cpp:1184
unsigned getOpcode() const
Returns a member of one of the enums like Instruction::Add.
Definition: Instruction.h:125
An instruction for storing to memory.
Definition: Instructions.h:320
unsigned getBitWidth() const
Get the number of bits in this IntegerType.
Definition: DerivedTypes.h:66
Concrete subclass of DominatorTreeBase that is used to compute a normal dominator tree...
Definition: Dominators.h:144
Value * getOperand(unsigned i) const
Definition: User.h:169
size_type count(const key_type &key) const
Count the number of elements of a given key in the SetVector.
Definition: SetVector.h:210
Class to represent pointers.
Definition: DerivedTypes.h:544
const BasicBlock & getEntryBlock() const
Definition: Function.h:664
NodeT * getBlock() const
BlockFrequencyInfo pass uses BlockFrequencyInfoImpl implementation to estimate IR basic block frequen...
static bool runOnFunction(Function &F, bool PostInlining)
initializer< Ty > init(const Ty &Val)
Definition: CommandLine.h:432
Wrapper pass for TargetTransformInfo.
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:328
LLVM Basic Block Representation.
Definition: BasicBlock.h:57
The instances of the Type class are immutable: once they are created, they are never changed...
Definition: Type.h:45
An analysis pass based on the new PM to deliver ProfileSummaryInfo.
bool ult(const APInt &RHS) const
Unsigned less than comparison.
Definition: APInt.h:1184
DomTreeNodeBase * getIDom() const
static GCRegistry::Add< CoreCLRGC > E("coreclr", "CoreCLR-compatible GC")
This is an important base class in LLVM.
Definition: Constant.h:41
bool canReplaceOperandWithVariable(const Instruction *I, unsigned OpIdx)
Given an instruction, is it legal to set operand OpIdx to a non-constant value?
Definition: Local.cpp:2907
This file contains the declarations for the subclasses of Constant, which represent the different fla...
std::pair< iterator, bool > insert(PtrType Ptr)
Inserts Ptr if and only if there is no element in the container equal to Ptr.
Definition: SmallPtrSet.h:370
Represent the analysis usage information of a pass.
FunctionPass class - This class is used to implement most global optimizations.
Definition: Pass.h:284
unsigned getAddressSpace() const
Return the address space of the Pointer type.
Definition: DerivedTypes.h:572
void reserve(size_type NumEntries)
Grow the densemap so that it can contain at least NumEntries items before resizing again...
Definition: DenseMap.h:103
size_type count(ConstPtrType Ptr) const
count - Return 1 if the specified pointer is in the set, 0 otherwise.
Definition: SmallPtrSet.h:381
Class to represent integer types.
Definition: DerivedTypes.h:40
LLVMContext & getContext() const
getContext - Return a reference to the LLVMContext associated with this function. ...
Definition: Function.cpp:205
static PreservedAnalyses all()
Construct a special preserved set that preserves all passes.
Definition: PassManager.h:159
bool isCast() const
Definition: Instruction.h:133
size_t size() const
Definition: SmallVector.h:52
static cl::opt< bool > ConstHoistWithBlockFrequency("consthoist-with-block-frequency", cl::init(true), cl::Hidden, cl::desc("Enable the use of the block frequency analysis to reduce the " "chance to execute const materialization more frequently than " "without hoisting."))
DomTreeNodeBase< NodeT > * getNode(const NodeT *BB) const
getNode - return the (Post)DominatorTree node for the specified basic block.
static PointerType * getInt8PtrTy(LLVMContext &C, unsigned AS=0)
Definition: Type.cpp:219
INITIALIZE_PASS_END(RegBankSelect, DEBUG_TYPE, "Assign register bank of generic virtual registers", false, false) RegBankSelect
Keeps track of the user of a constant and the operand index where the constant is used...
bool runImpl(Function &F, TargetTransformInfo &TTI, DominatorTree &DT, BlockFrequencyInfo *BFI, BasicBlock &Entry, ProfileSummaryInfo *PSI)
Optimize expensive integer constants in the given function.
Analysis pass which computes BlockFrequencyInfo.
Iterator for intrusive lists based on ilist_node.
unsigned getNumOperands() const
Definition: User.h:191
SmallPtrSet - This class implements a set which is optimized for holding SmallSize or less elements...
Definition: SmallPtrSet.h:417
This is the shared class of boolean and integer constants.
Definition: Constants.h:83
This pass provides access to the codegen interfaces that are needed for IR-level transformations.
An analysis over an "inner" IR unit that provides access to an analysis manager over a "outer" IR uni...
Definition: PassManager.h:1160
This is a &#39;vector&#39; (really, a variable-sized array), optimized for the case when the array is small...
Definition: SmallVector.h:837
Instruction * user_back()
Specialize the methods defined in Value, as we know that an instruction can only be used by other ins...
Definition: Instruction.h:63
static Constant * get(Type *Ty, uint64_t V, bool isSigned=false)
If Ty is a vector type, return a Constant with a splat of the given value.
Definition: Constants.cpp:653
void setPreservesCFG()
This function should be called by the pass, iff they do not:
Definition: Pass.cpp:301
static Optional< APInt > calculateOffsetDiff(const APInt &V1, const APInt &V2)
BlockFrequency getBlockFreq(const BasicBlock *BB) const
getblockFreq - Return block frequency.
void setOperand(unsigned i, Value *Val)
Definition: User.h:174
raw_ostream & dbgs()
dbgs() - This returns a reference to a raw_ostream for debugging messages.
Definition: Debug.cpp:132
PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM)
Class for arbitrary precision integers.
Definition: APInt.h:69
static BinaryOperator * Create(BinaryOps Op, Value *S1, Value *S2, const Twine &Name=Twine(), Instruction *InsertBefore=nullptr)
Construct a binary instruction, given the opcode and the two operands.
Represents analyses that only rely on functions&#39; control flow.
Definition: PassManager.h:114
const DebugLoc & getDebugLoc() const
Return the debug location for this node as a DebugLoc.
Definition: Instruction.h:331
static IntegerType * getInt32Ty(LLVMContext &C)
Definition: Type.cpp:175
LLVM_NODISCARD bool empty() const
Definition: SmallVector.h:55
uint64_t getLimitedValue(uint64_t Limit=UINT64_MAX) const
If this value is smaller than the specified limit, return it, otherwise return the limit value...
Definition: APInt.h:481
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
bool empty() const
Determine if the SetVector is empty or not.
Definition: SetVector.h:72
LLVM_NODISCARD std::enable_if<!is_simple_type< Y >::value, typename cast_retty< X, const Y >::ret_type >::type dyn_cast(const Y &Val)
Definition: Casting.h:332
static void findBestInsertionSet(DominatorTree &DT, BlockFrequencyInfo &BFI, BasicBlock *Entry, SetVector< BasicBlock *> &BBs)
Given BBs as input, find another set of BBs which collectively dominates BBs and have the minimal sum...
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
The cost of a typical &#39;add&#39; instruction.
void stable_sort(R &&Range)
Definition: STLExtras.h:1289
bool isEHPad() const
Return true if this basic block is an exception handling block.
Definition: BasicBlock.h:406
Module * getParent()
Get the module that this global value is contained inside of...
Definition: GlobalValue.h:575
LLVM Value Representation.
Definition: Value.h:73
A vector that has set insertion semantics.
Definition: SetVector.h:40
bool isCast() const
Return true if this is a convert constant expression.
Definition: Constants.cpp:1176
bool isEHPad() const
Return true if the instruction is a variety of EH-block.
Definition: Instruction.h:593
StringRef - Represent a constant reference to a string, i.e.
Definition: StringRef.h:48
A container for analyses that lazily runs them and caches their results.
RebasedConstantListType RebasedConstants
Legacy analysis pass which computes a DominatorTree.
Definition: Dominators.h:259
This pass exposes codegen information to IR-level passes.
#define LLVM_DEBUG(X)
Definition: Debug.h:122
bool use_empty() const
Definition: Value.h:342
Type * getElementType() const
Definition: DerivedTypes.h:563
PointerType * getType() const
Global values are always pointers.
Definition: GlobalValue.h:277
const BasicBlock * getParent() const
Definition: Instruction.h:66
FunctionPass * createConstantHoistingPass()