LLVM  9.0.0svn
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<SmallPtrSet<BasicBlock *, 16>, 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  SmallPtrSet<BasicBlock *, 16> &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  SmallPtrSet<BasicBlock *, 16> &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 SmallPtrSet<Instruction *, 8> ConstantHoistingPass::findConstantInsertionPoint(
309  const ConstantInfo &ConstInfo) const {
310  assert(!ConstInfo.RebasedConstants.empty() && "Invalid constant info entry.");
311  // Collect all basic blocks.
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.begin();
337  BB2 = *std::next(BBs.begin());
338  BB = DT->findNearestCommonDominator(BB1, BB2);
339  if (BB == Entry) {
340  InsertPts.insert(&Entry->front());
341  return InsertPts;
342  }
343  BBs.erase(BB1);
344  BBs.erase(BB2);
345  BBs.insert(BB);
346  }
347  assert((BBs.size() == 1) && "Expected only one element.");
348  Instruction &FirstInst = (*BBs.begin())->front();
349  InsertPts.insert(findMatInsertPt(&FirstInst));
350  return InsertPts;
351 }
352 
353 /// Record constant integer ConstInt for instruction Inst at operand
354 /// index Idx.
355 ///
356 /// The operand at index Idx is not necessarily the constant integer itself. It
357 /// could also be a cast instruction or a constant expression that uses the
358 /// constant integer.
359 void ConstantHoistingPass::collectConstantCandidates(
360  ConstCandMapType &ConstCandMap, Instruction *Inst, unsigned Idx,
361  ConstantInt *ConstInt) {
362  unsigned Cost;
363  // Ask the target about the cost of materializing the constant for the given
364  // instruction and operand index.
365  if (auto IntrInst = dyn_cast<IntrinsicInst>(Inst))
366  Cost = TTI->getIntImmCost(IntrInst->getIntrinsicID(), Idx,
367  ConstInt->getValue(), ConstInt->getType());
368  else
369  Cost = TTI->getIntImmCost(Inst->getOpcode(), Idx, ConstInt->getValue(),
370  ConstInt->getType());
371 
372  // Ignore cheap integer constants.
373  if (Cost > TargetTransformInfo::TCC_Basic) {
374  ConstCandMapType::iterator Itr;
375  bool Inserted;
376  ConstPtrUnionType Cand = ConstInt;
377  std::tie(Itr, Inserted) = ConstCandMap.insert(std::make_pair(Cand, 0));
378  if (Inserted) {
379  ConstIntCandVec.push_back(ConstantCandidate(ConstInt));
380  Itr->second = ConstIntCandVec.size() - 1;
381  }
382  ConstIntCandVec[Itr->second].addUser(Inst, Idx, Cost);
383  LLVM_DEBUG(if (isa<ConstantInt>(Inst->getOperand(Idx))) dbgs()
384  << "Collect constant " << *ConstInt << " from " << *Inst
385  << " with cost " << Cost << '\n';
386  else dbgs() << "Collect constant " << *ConstInt
387  << " indirectly from " << *Inst << " via "
388  << *Inst->getOperand(Idx) << " with cost " << Cost
389  << '\n';);
390  }
391 }
392 
393 /// Record constant GEP expression for instruction Inst at operand index Idx.
394 void ConstantHoistingPass::collectConstantCandidates(
395  ConstCandMapType &ConstCandMap, Instruction *Inst, unsigned Idx,
396  ConstantExpr *ConstExpr) {
397  // TODO: Handle vector GEPs
398  if (ConstExpr->getType()->isVectorTy())
399  return;
400 
401  GlobalVariable *BaseGV = dyn_cast<GlobalVariable>(ConstExpr->getOperand(0));
402  if (!BaseGV)
403  return;
404 
405  // Get offset from the base GV.
406  PointerType *GVPtrTy = dyn_cast<PointerType>(BaseGV->getType());
407  IntegerType *PtrIntTy = DL->getIntPtrType(*Ctx, GVPtrTy->getAddressSpace());
408  APInt Offset(DL->getTypeSizeInBits(PtrIntTy), /*val*/0, /*isSigned*/true);
409  auto *GEPO = cast<GEPOperator>(ConstExpr);
410  if (!GEPO->accumulateConstantOffset(*DL, Offset))
411  return;
412 
413  if (!Offset.isIntN(32))
414  return;
415 
416  // A constant GEP expression that has a GlobalVariable as base pointer is
417  // usually lowered to a load from constant pool. Such operation is unlikely
418  // to be cheaper than compute it by <Base + Offset>, which can be lowered to
419  // an ADD instruction or folded into Load/Store instruction.
420  int Cost = TTI->getIntImmCost(Instruction::Add, 1, Offset, PtrIntTy);
421  ConstCandVecType &ExprCandVec = ConstGEPCandMap[BaseGV];
422  ConstCandMapType::iterator Itr;
423  bool Inserted;
424  ConstPtrUnionType Cand = ConstExpr;
425  std::tie(Itr, Inserted) = ConstCandMap.insert(std::make_pair(Cand, 0));
426  if (Inserted) {
427  ExprCandVec.push_back(ConstantCandidate(
428  ConstantInt::get(Type::getInt32Ty(*Ctx), Offset.getLimitedValue()),
429  ConstExpr));
430  Itr->second = ExprCandVec.size() - 1;
431  }
432  ExprCandVec[Itr->second].addUser(Inst, Idx, Cost);
433 }
434 
435 /// Check the operand for instruction Inst at index Idx.
436 void ConstantHoistingPass::collectConstantCandidates(
437  ConstCandMapType &ConstCandMap, Instruction *Inst, unsigned Idx) {
438  Value *Opnd = Inst->getOperand(Idx);
439 
440  // Visit constant integers.
441  if (auto ConstInt = dyn_cast<ConstantInt>(Opnd)) {
442  collectConstantCandidates(ConstCandMap, Inst, Idx, ConstInt);
443  return;
444  }
445 
446  // Visit cast instructions that have constant integers.
447  if (auto CastInst = dyn_cast<Instruction>(Opnd)) {
448  // Only visit cast instructions, which have been skipped. All other
449  // instructions should have already been visited.
450  if (!CastInst->isCast())
451  return;
452 
453  if (auto *ConstInt = dyn_cast<ConstantInt>(CastInst->getOperand(0))) {
454  // Pretend the constant is directly used by the instruction and ignore
455  // the cast instruction.
456  collectConstantCandidates(ConstCandMap, Inst, Idx, ConstInt);
457  return;
458  }
459  }
460 
461  // Visit constant expressions that have constant integers.
462  if (auto ConstExpr = dyn_cast<ConstantExpr>(Opnd)) {
463  // Handle constant gep expressions.
465  collectConstantCandidates(ConstCandMap, Inst, Idx, ConstExpr);
466 
467  // Only visit constant cast expressions.
468  if (!ConstExpr->isCast())
469  return;
470 
471  if (auto ConstInt = dyn_cast<ConstantInt>(ConstExpr->getOperand(0))) {
472  // Pretend the constant is directly used by the instruction and ignore
473  // the constant expression.
474  collectConstantCandidates(ConstCandMap, Inst, Idx, ConstInt);
475  return;
476  }
477  }
478 }
479 
480 /// Scan the instruction for expensive integer constants and record them
481 /// in the constant candidate vector.
482 void ConstantHoistingPass::collectConstantCandidates(
483  ConstCandMapType &ConstCandMap, Instruction *Inst) {
484  // Skip all cast instructions. They are visited indirectly later on.
485  if (Inst->isCast())
486  return;
487 
488  // Scan all operands.
489  for (unsigned Idx = 0, E = Inst->getNumOperands(); Idx != E; ++Idx) {
490  // The cost of materializing the constants (defined in
491  // `TargetTransformInfo::getIntImmCost`) for instructions which only take
492  // constant variables is lower than `TargetTransformInfo::TCC_Basic`. So
493  // it's safe for us to collect constant candidates from all IntrinsicInsts.
494  if (canReplaceOperandWithVariable(Inst, Idx) || isa<IntrinsicInst>(Inst)) {
495  collectConstantCandidates(ConstCandMap, Inst, Idx);
496  }
497  } // end of for all operands
498 }
499 
500 /// Collect all integer constants in the function that cannot be folded
501 /// into an instruction itself.
502 void ConstantHoistingPass::collectConstantCandidates(Function &Fn) {
503  ConstCandMapType ConstCandMap;
504  for (BasicBlock &BB : Fn)
505  for (Instruction &Inst : BB)
506  collectConstantCandidates(ConstCandMap, &Inst);
507 }
508 
509 // This helper function is necessary to deal with values that have different
510 // bit widths (APInt Operator- does not like that). If the value cannot be
511 // represented in uint64 we return an "empty" APInt. This is then interpreted
512 // as the value is not in range.
513 static Optional<APInt> calculateOffsetDiff(const APInt &V1, const APInt &V2) {
514  Optional<APInt> Res = None;
515  unsigned BW = V1.getBitWidth() > V2.getBitWidth() ?
516  V1.getBitWidth() : V2.getBitWidth();
517  uint64_t LimVal1 = V1.getLimitedValue();
518  uint64_t LimVal2 = V2.getLimitedValue();
519 
520  if (LimVal1 == ~0ULL || LimVal2 == ~0ULL)
521  return Res;
522 
523  uint64_t Diff = LimVal1 - LimVal2;
524  return APInt(BW, Diff, true);
525 }
526 
527 // From a list of constants, one needs to picked as the base and the other
528 // constants will be transformed into an offset from that base constant. The
529 // question is which we can pick best? For example, consider these constants
530 // and their number of uses:
531 //
532 // Constants| 2 | 4 | 12 | 42 |
533 // NumUses | 3 | 2 | 8 | 7 |
534 //
535 // Selecting constant 12 because it has the most uses will generate negative
536 // offsets for constants 2 and 4 (i.e. -10 and -8 respectively). If negative
537 // offsets lead to less optimal code generation, then there might be better
538 // solutions. Suppose immediates in the range of 0..35 are most optimally
539 // supported by the architecture, then selecting constant 2 is most optimal
540 // because this will generate offsets: 0, 2, 10, 40. Offsets 0, 2 and 10 are in
541 // range 0..35, and thus 3 + 2 + 8 = 13 uses are in range. Selecting 12 would
542 // have only 8 uses in range, so choosing 2 as a base is more optimal. Thus, in
543 // selecting the base constant the range of the offsets is a very important
544 // factor too that we take into account here. This algorithm calculates a total
545 // costs for selecting a constant as the base and substract the costs if
546 // immediates are out of range. It has quadratic complexity, so we call this
547 // function only when we're optimising for size and there are less than 100
548 // constants, we fall back to the straightforward algorithm otherwise
549 // which does not do all the offset calculations.
550 unsigned
551 ConstantHoistingPass::maximizeConstantsInRange(ConstCandVecType::iterator S,
552  ConstCandVecType::iterator E,
553  ConstCandVecType::iterator &MaxCostItr) {
554  unsigned NumUses = 0;
555 
556  bool OptForSize = Entry->getParent()->hasOptSize() ||
557  llvm::shouldOptimizeForSize(Entry->getParent(), PSI, BFI);
558  if (!OptForSize || std::distance(S,E) > 100) {
559  for (auto ConstCand = S; ConstCand != E; ++ConstCand) {
560  NumUses += ConstCand->Uses.size();
561  if (ConstCand->CumulativeCost > MaxCostItr->CumulativeCost)
562  MaxCostItr = ConstCand;
563  }
564  return NumUses;
565  }
566 
567  LLVM_DEBUG(dbgs() << "== Maximize constants in range ==\n");
568  int MaxCost = -1;
569  for (auto ConstCand = S; ConstCand != E; ++ConstCand) {
570  auto Value = ConstCand->ConstInt->getValue();
571  Type *Ty = ConstCand->ConstInt->getType();
572  int Cost = 0;
573  NumUses += ConstCand->Uses.size();
574  LLVM_DEBUG(dbgs() << "= Constant: " << ConstCand->ConstInt->getValue()
575  << "\n");
576 
577  for (auto User : ConstCand->Uses) {
578  unsigned Opcode = User.Inst->getOpcode();
579  unsigned OpndIdx = User.OpndIdx;
580  Cost += TTI->getIntImmCost(Opcode, OpndIdx, Value, Ty);
581  LLVM_DEBUG(dbgs() << "Cost: " << Cost << "\n");
582 
583  for (auto C2 = S; C2 != E; ++C2) {
585  C2->ConstInt->getValue(),
586  ConstCand->ConstInt->getValue());
587  if (Diff) {
588  const int ImmCosts =
589  TTI->getIntImmCodeSizeCost(Opcode, OpndIdx, Diff.getValue(), Ty);
590  Cost -= ImmCosts;
591  LLVM_DEBUG(dbgs() << "Offset " << Diff.getValue() << " "
592  << "has penalty: " << ImmCosts << "\n"
593  << "Adjusted cost: " << Cost << "\n");
594  }
595  }
596  }
597  LLVM_DEBUG(dbgs() << "Cumulative cost: " << Cost << "\n");
598  if (Cost > MaxCost) {
599  MaxCost = Cost;
600  MaxCostItr = ConstCand;
601  LLVM_DEBUG(dbgs() << "New candidate: " << MaxCostItr->ConstInt->getValue()
602  << "\n");
603  }
604  }
605  return NumUses;
606 }
607 
608 /// Find the base constant within the given range and rebase all other
609 /// constants with respect to the base constant.
610 void ConstantHoistingPass::findAndMakeBaseConstant(
611  ConstCandVecType::iterator S, ConstCandVecType::iterator E,
613  auto MaxCostItr = S;
614  unsigned NumUses = maximizeConstantsInRange(S, E, MaxCostItr);
615 
616  // Don't hoist constants that have only one use.
617  if (NumUses <= 1)
618  return;
619 
620  ConstantInt *ConstInt = MaxCostItr->ConstInt;
621  ConstantExpr *ConstExpr = MaxCostItr->ConstExpr;
622  ConstantInfo ConstInfo;
623  ConstInfo.BaseInt = ConstInt;
624  ConstInfo.BaseExpr = ConstExpr;
625  Type *Ty = ConstInt->getType();
626 
627  // Rebase the constants with respect to the base constant.
628  for (auto ConstCand = S; ConstCand != E; ++ConstCand) {
629  APInt Diff = ConstCand->ConstInt->getValue() - ConstInt->getValue();
630  Constant *Offset = Diff == 0 ? nullptr : ConstantInt::get(Ty, Diff);
631  Type *ConstTy =
632  ConstCand->ConstExpr ? ConstCand->ConstExpr->getType() : nullptr;
633  ConstInfo.RebasedConstants.push_back(
634  RebasedConstantInfo(std::move(ConstCand->Uses), Offset, ConstTy));
635  }
636  ConstInfoVec.push_back(std::move(ConstInfo));
637 }
638 
639 /// Finds and combines constant candidates that can be easily
640 /// rematerialized with an add from a common base constant.
641 void ConstantHoistingPass::findBaseConstants(GlobalVariable *BaseGV) {
642  // If BaseGV is nullptr, find base among candidate constant integers;
643  // Otherwise find base among constant GEPs that share the same BaseGV.
644  ConstCandVecType &ConstCandVec = BaseGV ?
645  ConstGEPCandMap[BaseGV] : ConstIntCandVec;
646  ConstInfoVecType &ConstInfoVec = BaseGV ?
647  ConstGEPInfoMap[BaseGV] : ConstIntInfoVec;
648 
649  // Sort the constants by value and type. This invalidates the mapping!
650  llvm::stable_sort(ConstCandVec, [](const ConstantCandidate &LHS,
651  const ConstantCandidate &RHS) {
652  if (LHS.ConstInt->getType() != RHS.ConstInt->getType())
653  return LHS.ConstInt->getType()->getBitWidth() <
654  RHS.ConstInt->getType()->getBitWidth();
655  return LHS.ConstInt->getValue().ult(RHS.ConstInt->getValue());
656  });
657 
658  // Simple linear scan through the sorted constant candidate vector for viable
659  // merge candidates.
660  auto MinValItr = ConstCandVec.begin();
661  for (auto CC = std::next(ConstCandVec.begin()), E = ConstCandVec.end();
662  CC != E; ++CC) {
663  if (MinValItr->ConstInt->getType() == CC->ConstInt->getType()) {
664  Type *MemUseValTy = nullptr;
665  for (auto &U : CC->Uses) {
666  auto *UI = U.Inst;
667  if (LoadInst *LI = dyn_cast<LoadInst>(UI)) {
668  MemUseValTy = LI->getType();
669  break;
670  } else if (StoreInst *SI = dyn_cast<StoreInst>(UI)) {
671  // Make sure the constant is used as pointer operand of the StoreInst.
672  if (SI->getPointerOperand() == SI->getOperand(U.OpndIdx)) {
673  MemUseValTy = SI->getValueOperand()->getType();
674  break;
675  }
676  }
677  }
678 
679  // Check if the constant is in range of an add with immediate.
680  APInt Diff = CC->ConstInt->getValue() - MinValItr->ConstInt->getValue();
681  if ((Diff.getBitWidth() <= 64) &&
682  TTI->isLegalAddImmediate(Diff.getSExtValue()) &&
683  // Check if Diff can be used as offset in addressing mode of the user
684  // memory instruction.
685  (!MemUseValTy || TTI->isLegalAddressingMode(MemUseValTy,
686  /*BaseGV*/nullptr, /*BaseOffset*/Diff.getSExtValue(),
687  /*HasBaseReg*/true, /*Scale*/0)))
688  continue;
689  }
690  // We either have now a different constant type or the constant is not in
691  // range of an add with immediate anymore.
692  findAndMakeBaseConstant(MinValItr, CC, ConstInfoVec);
693  // Start a new base constant search.
694  MinValItr = CC;
695  }
696  // Finalize the last base constant search.
697  findAndMakeBaseConstant(MinValItr, ConstCandVec.end(), ConstInfoVec);
698 }
699 
700 /// Updates the operand at Idx in instruction Inst with the result of
701 /// instruction Mat. If the instruction is a PHI node then special
702 /// handling for duplicate values form the same incoming basic block is
703 /// required.
704 /// \return The update will always succeed, but the return value indicated if
705 /// Mat was used for the update or not.
706 static bool updateOperand(Instruction *Inst, unsigned Idx, Instruction *Mat) {
707  if (auto PHI = dyn_cast<PHINode>(Inst)) {
708  // Check if any previous operand of the PHI node has the same incoming basic
709  // block. This is a very odd case that happens when the incoming basic block
710  // has a switch statement. In this case use the same value as the previous
711  // operand(s), otherwise we will fail verification due to different values.
712  // The values are actually the same, but the variable names are different
713  // and the verifier doesn't like that.
714  BasicBlock *IncomingBB = PHI->getIncomingBlock(Idx);
715  for (unsigned i = 0; i < Idx; ++i) {
716  if (PHI->getIncomingBlock(i) == IncomingBB) {
717  Value *IncomingVal = PHI->getIncomingValue(i);
718  Inst->setOperand(Idx, IncomingVal);
719  return false;
720  }
721  }
722  }
723 
724  Inst->setOperand(Idx, Mat);
725  return true;
726 }
727 
728 /// Emit materialization code for all rebased constants and update their
729 /// users.
730 void ConstantHoistingPass::emitBaseConstants(Instruction *Base,
731  Constant *Offset,
732  Type *Ty,
733  const ConstantUser &ConstUser) {
734  Instruction *Mat = Base;
735 
736  // The same offset can be dereferenced to different types in nested struct.
737  if (!Offset && Ty && Ty != Base->getType())
738  Offset = ConstantInt::get(Type::getInt32Ty(*Ctx), 0);
739 
740  if (Offset) {
741  Instruction *InsertionPt = findMatInsertPt(ConstUser.Inst,
742  ConstUser.OpndIdx);
743  if (Ty) {
744  // Constant being rebased is a ConstantExpr.
745  PointerType *Int8PtrTy = Type::getInt8PtrTy(*Ctx,
746  cast<PointerType>(Ty)->getAddressSpace());
747  Base = new BitCastInst(Base, Int8PtrTy, "base_bitcast", InsertionPt);
748  Mat = GetElementPtrInst::Create(Int8PtrTy->getElementType(), Base,
749  Offset, "mat_gep", InsertionPt);
750  Mat = new BitCastInst(Mat, Ty, "mat_bitcast", InsertionPt);
751  } else
752  // Constant being rebased is a ConstantInt.
753  Mat = BinaryOperator::Create(Instruction::Add, Base, Offset,
754  "const_mat", InsertionPt);
755 
756  LLVM_DEBUG(dbgs() << "Materialize constant (" << *Base->getOperand(0)
757  << " + " << *Offset << ") in BB "
758  << Mat->getParent()->getName() << '\n'
759  << *Mat << '\n');
760  Mat->setDebugLoc(ConstUser.Inst->getDebugLoc());
761  }
762  Value *Opnd = ConstUser.Inst->getOperand(ConstUser.OpndIdx);
763 
764  // Visit constant integer.
765  if (isa<ConstantInt>(Opnd)) {
766  LLVM_DEBUG(dbgs() << "Update: " << *ConstUser.Inst << '\n');
767  if (!updateOperand(ConstUser.Inst, ConstUser.OpndIdx, Mat) && Offset)
768  Mat->eraseFromParent();
769  LLVM_DEBUG(dbgs() << "To : " << *ConstUser.Inst << '\n');
770  return;
771  }
772 
773  // Visit cast instruction.
774  if (auto CastInst = dyn_cast<Instruction>(Opnd)) {
775  assert(CastInst->isCast() && "Expected an cast instruction!");
776  // Check if we already have visited this cast instruction before to avoid
777  // unnecessary cloning.
778  Instruction *&ClonedCastInst = ClonedCastMap[CastInst];
779  if (!ClonedCastInst) {
780  ClonedCastInst = CastInst->clone();
781  ClonedCastInst->setOperand(0, Mat);
782  ClonedCastInst->insertAfter(CastInst);
783  // Use the same debug location as the original cast instruction.
784  ClonedCastInst->setDebugLoc(CastInst->getDebugLoc());
785  LLVM_DEBUG(dbgs() << "Clone instruction: " << *CastInst << '\n'
786  << "To : " << *ClonedCastInst << '\n');
787  }
788 
789  LLVM_DEBUG(dbgs() << "Update: " << *ConstUser.Inst << '\n');
790  updateOperand(ConstUser.Inst, ConstUser.OpndIdx, ClonedCastInst);
791  LLVM_DEBUG(dbgs() << "To : " << *ConstUser.Inst << '\n');
792  return;
793  }
794 
795  // Visit constant expression.
796  if (auto ConstExpr = dyn_cast<ConstantExpr>(Opnd)) {
797  if (ConstExpr->isGEPWithNoNotionalOverIndexing()) {
798  // Operand is a ConstantGEP, replace it.
799  updateOperand(ConstUser.Inst, ConstUser.OpndIdx, Mat);
800  return;
801  }
802 
803  // Aside from constant GEPs, only constant cast expressions are collected.
804  assert(ConstExpr->isCast() && "ConstExpr should be a cast");
805  Instruction *ConstExprInst = ConstExpr->getAsInstruction();
806  ConstExprInst->setOperand(0, Mat);
807  ConstExprInst->insertBefore(findMatInsertPt(ConstUser.Inst,
808  ConstUser.OpndIdx));
809 
810  // Use the same debug location as the instruction we are about to update.
811  ConstExprInst->setDebugLoc(ConstUser.Inst->getDebugLoc());
812 
813  LLVM_DEBUG(dbgs() << "Create instruction: " << *ConstExprInst << '\n'
814  << "From : " << *ConstExpr << '\n');
815  LLVM_DEBUG(dbgs() << "Update: " << *ConstUser.Inst << '\n');
816  if (!updateOperand(ConstUser.Inst, ConstUser.OpndIdx, ConstExprInst)) {
817  ConstExprInst->eraseFromParent();
818  if (Offset)
819  Mat->eraseFromParent();
820  }
821  LLVM_DEBUG(dbgs() << "To : " << *ConstUser.Inst << '\n');
822  return;
823  }
824 }
825 
826 /// Hoist and hide the base constant behind a bitcast and emit
827 /// materialization code for derived constants.
828 bool ConstantHoistingPass::emitBaseConstants(GlobalVariable *BaseGV) {
829  bool MadeChange = false;
831  BaseGV ? ConstGEPInfoMap[BaseGV] : ConstIntInfoVec;
832  for (auto const &ConstInfo : ConstInfoVec) {
833  SmallPtrSet<Instruction *, 8> IPSet = findConstantInsertionPoint(ConstInfo);
834  // We can have an empty set if the function contains unreachable blocks.
835  if (IPSet.empty())
836  continue;
837 
838  unsigned UsesNum = 0;
839  unsigned ReBasesNum = 0;
840  unsigned NotRebasedNum = 0;
841  for (Instruction *IP : IPSet) {
842  // First, collect constants depending on this IP of the base.
843  unsigned Uses = 0;
844  using RebasedUse = std::tuple<Constant *, Type *, ConstantUser>;
845  SmallVector<RebasedUse, 4> ToBeRebased;
846  for (auto const &RCI : ConstInfo.RebasedConstants) {
847  for (auto const &U : RCI.Uses) {
848  Uses++;
849  BasicBlock *OrigMatInsertBB =
850  findMatInsertPt(U.Inst, U.OpndIdx)->getParent();
851  // If Base constant is to be inserted in multiple places,
852  // generate rebase for U using the Base dominating U.
853  if (IPSet.size() == 1 ||
854  DT->dominates(IP->getParent(), OrigMatInsertBB))
855  ToBeRebased.push_back(RebasedUse(RCI.Offset, RCI.Ty, U));
856  }
857  }
858  UsesNum = Uses;
859 
860  // If only few constants depend on this IP of base, skip rebasing,
861  // assuming the base and the rebased have the same materialization cost.
862  if (ToBeRebased.size() < MinNumOfDependentToRebase) {
863  NotRebasedNum += ToBeRebased.size();
864  continue;
865  }
866 
867  // Emit an instance of the base at this IP.
868  Instruction *Base = nullptr;
869  // Hoist and hide the base constant behind a bitcast.
870  if (ConstInfo.BaseExpr) {
871  assert(BaseGV && "A base constant expression must have an base GV");
872  Type *Ty = ConstInfo.BaseExpr->getType();
873  Base = new BitCastInst(ConstInfo.BaseExpr, Ty, "const", IP);
874  } else {
875  IntegerType *Ty = ConstInfo.BaseInt->getType();
876  Base = new BitCastInst(ConstInfo.BaseInt, Ty, "const", IP);
877  }
878 
879  Base->setDebugLoc(IP->getDebugLoc());
880 
881  LLVM_DEBUG(dbgs() << "Hoist constant (" << *ConstInfo.BaseInt
882  << ") to BB " << IP->getParent()->getName() << '\n'
883  << *Base << '\n');
884 
885  // Emit materialization code for rebased constants depending on this IP.
886  for (auto const &R : ToBeRebased) {
887  Constant *Off = std::get<0>(R);
888  Type *Ty = std::get<1>(R);
889  ConstantUser U = std::get<2>(R);
890  emitBaseConstants(Base, Off, Ty, U);
891  ReBasesNum++;
892  // Use the same debug location as the last user of the constant.
894  Base->getDebugLoc(), U.Inst->getDebugLoc()));
895  }
896  assert(!Base->use_empty() && "The use list is empty!?");
897  assert(isa<Instruction>(Base->user_back()) &&
898  "All uses should be instructions.");
899  }
900  (void)UsesNum;
901  (void)ReBasesNum;
902  (void)NotRebasedNum;
903  // Expect all uses are rebased after rebase is done.
904  assert(UsesNum == (ReBasesNum + NotRebasedNum) &&
905  "Not all uses are rebased");
906 
907  NumConstantsHoisted++;
908 
909  // Base constant is also included in ConstInfo.RebasedConstants, so
910  // deduct 1 from ConstInfo.RebasedConstants.size().
911  NumConstantsRebased += ConstInfo.RebasedConstants.size() - 1;
912 
913  MadeChange = true;
914  }
915  return MadeChange;
916 }
917 
918 /// Check all cast instructions we made a copy of and remove them if they
919 /// have no more users.
920 void ConstantHoistingPass::deleteDeadCastInst() const {
921  for (auto const &I : ClonedCastMap)
922  if (I.first->use_empty())
923  I.first->eraseFromParent();
924 }
925 
926 /// Optimize expensive integer constants in the given function.
930  this->TTI = &TTI;
931  this->DT = &DT;
932  this->BFI = BFI;
933  this->DL = &Fn.getParent()->getDataLayout();
934  this->Ctx = &Fn.getContext();
935  this->Entry = &Entry;
936  this->PSI = PSI;
937  // Collect all constant candidates.
938  collectConstantCandidates(Fn);
939 
940  // Combine constants that can be easily materialized with an add from a common
941  // base constant.
942  if (!ConstIntCandVec.empty())
943  findBaseConstants(nullptr);
944  for (auto &MapEntry : ConstGEPCandMap)
945  if (!MapEntry.second.empty())
946  findBaseConstants(MapEntry.first);
947 
948  // Finally hoist the base constant and emit materialization code for dependent
949  // constants.
950  bool MadeChange = false;
951  if (!ConstIntInfoVec.empty())
952  MadeChange = emitBaseConstants(nullptr);
953  for (auto MapEntry : ConstGEPInfoMap)
954  if (!MapEntry.second.empty())
955  MadeChange |= emitBaseConstants(MapEntry.first);
956 
957 
958  // Cleanup dead instructions.
959  deleteDeadCastInst();
960 
961  cleanup();
962 
963  return MadeChange;
964 }
965 
968  auto &DT = AM.getResult<DominatorTreeAnalysis>(F);
969  auto &TTI = AM.getResult<TargetIRAnalysis>(F);
972  : nullptr;
973  auto &MAM = AM.getResult<ModuleAnalysisManagerFunctionProxy>(F).getManager();
974  auto *PSI = MAM.getCachedResult<ProfileSummaryAnalysis>(*F.getParent());
975  if (!runImpl(F, TTI, DT, BFI, F.getEntryBlock(), PSI))
976  return PreservedAnalyses::all();
977 
979  PA.preserveSet<CFGAnalyses>();
980  return PA;
981 }
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 void findBestInsertionSet(DominatorTree &DT, BlockFrequencyInfo &BFI, BasicBlock *Entry, SmallPtrSet< BasicBlock *, 8 > &BBs)
Given BBs as input, find another set of BBs which collectively dominates BBs and have the minimal sum...
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:899
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:1508
iterator begin()
Instruction iterator methods.
Definition: BasicBlock.h:268
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:416
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:2963
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:1574
Type * getType() const
All values are typed, get the type of this value.
Definition: Value.h:244
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:1162
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:65
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
Class to represent pointers.
Definition: DerivedTypes.h:498
const BasicBlock & getEntryBlock() const
Definition: Function.h:645
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:318
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
LLVM_NODISCARD bool empty() const
Definition: SmallPtrSet.h:91
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:2866
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:526
void reserve(size_type NumEntries)
Grow the densemap so that it can contain at least NumEntries items before resizing again...
Definition: DenseMap.h:129
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:39
LLVMContext & getContext() const
getContext - Return a reference to the LLVMContext associated with this function. ...
Definition: Function.cpp:196
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...
size_type size() const
Definition: SmallPtrSet.h:92
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.
bool erase(PtrType Ptr)
erase - If the set contains the specified pointer, remove it and return true, otherwise return false...
Definition: SmallPtrSet.h:377
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:841
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:631
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:321
iterator begin() const
Definition: SmallPtrSet.h:396
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
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
iterator end() const
Definition: SmallPtrSet.h:401
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
The cost of a typical &#39;add&#39; instruction.
void stable_sort(R &&Range)
Definition: STLExtras.h:1309
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:565
LLVM Value Representation.
Definition: Value.h:72
bool isCast() const
Return true if this is a convert constant expression.
Definition: Constants.cpp:1154
bool isEHPad() const
Return true if the instruction is a variety of EH-block.
Definition: Instruction.h:583
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:322
Type * getElementType() const
Definition: DerivedTypes.h:517
PointerType * getType() const
Global values are always pointers.
Definition: GlobalValue.h:273
const BasicBlock * getParent() const
Definition: Instruction.h:66
FunctionPass * createConstantHoistingPass()