LLVM  8.0.0svn
ConstantHoisting.cpp
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1 //===- ConstantHoisting.cpp - Prepare code for expensive constants --------===//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This pass identifies expensive constants to hoist and coalesces them to
11 // better prepare it for SelectionDAG-based code generation. This works around
12 // the limitations of the basic-block-at-a-time approach.
13 //
14 // First it scans all instructions for integer constants and calculates its
15 // cost. If the constant can be folded into the instruction (the cost is
16 // TCC_Free) or the cost is just a simple operation (TCC_BASIC), then we don't
17 // consider it expensive and leave it alone. This is the default behavior and
18 // the default implementation of getIntImmCost will always return TCC_Free.
19 //
20 // If the cost is more than TCC_BASIC, then the integer constant can't be folded
21 // into the instruction and it might be beneficial to hoist the constant.
22 // Similar constants are coalesced to reduce register pressure and
23 // materialization code.
24 //
25 // When a constant is hoisted, it is also hidden behind a bitcast to force it to
26 // be live-out of the basic block. Otherwise the constant would be just
27 // duplicated and each basic block would have its own copy in the SelectionDAG.
28 // The SelectionDAG recognizes such constants as opaque and doesn't perform
29 // certain transformations on them, which would create a new expensive constant.
30 //
31 // This optimization is only applied to integer constants in instructions and
32 // simple (this means not nested) constant cast expressions. For example:
33 // %0 = load i64* inttoptr (i64 big_constant to i64*)
34 //===----------------------------------------------------------------------===//
35 
37 #include "llvm/ADT/APInt.h"
38 #include "llvm/ADT/DenseMap.h"
39 #include "llvm/ADT/None.h"
40 #include "llvm/ADT/Optional.h"
41 #include "llvm/ADT/SmallPtrSet.h"
42 #include "llvm/ADT/SmallVector.h"
43 #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"
64 #include <algorithm>
65 #include <cassert>
66 #include <cstdint>
67 #include <iterator>
68 #include <tuple>
69 #include <utility>
70 
71 using namespace llvm;
72 using namespace consthoist;
73 
74 #define DEBUG_TYPE "consthoist"
75 
76 STATISTIC(NumConstantsHoisted, "Number of constants hoisted");
77 STATISTIC(NumConstantsRebased, "Number of constants rebased");
78 
80  "consthoist-with-block-frequency", cl::init(true), cl::Hidden,
81  cl::desc("Enable the use of the block frequency analysis to reduce the "
82  "chance to execute const materialization more frequently than "
83  "without hoisting."));
84 
86  "consthoist-gep", cl::init(false), cl::Hidden,
87  cl::desc("Try hoisting constant gep expressions"));
88 
89 static cl::opt<unsigned>
90 MinNumOfDependentToRebase("consthoist-min-num-to-rebase",
91  cl::desc("Do not rebase if number of dependent constants of a Base is less "
92  "than this number."),
93  cl::init(0), cl::Hidden);
94 
95 namespace {
96 
97 /// The constant hoisting pass.
98 class ConstantHoistingLegacyPass : public FunctionPass {
99 public:
100  static char ID; // Pass identification, replacement for typeid
101 
102  ConstantHoistingLegacyPass() : FunctionPass(ID) {
104  }
105 
106  bool runOnFunction(Function &Fn) override;
107 
108  StringRef getPassName() const override { return "Constant Hoisting"; }
109 
110  void getAnalysisUsage(AnalysisUsage &AU) const override {
111  AU.setPreservesCFG();
116  }
117 
118  void releaseMemory() override { Impl.releaseMemory(); }
119 
120 private:
122 };
123 
124 } // end anonymous namespace
125 
127 
128 INITIALIZE_PASS_BEGIN(ConstantHoistingLegacyPass, "consthoist",
129  "Constant Hoisting", false, false)
133 INITIALIZE_PASS_END(ConstantHoistingLegacyPass, "consthoist",
134  "Constant Hoisting", false, false)
135 
137  return new ConstantHoistingLegacyPass();
138 }
139 
140 /// Perform the constant hoisting optimization for the given function.
142  if (skipFunction(Fn))
143  return false;
144 
145  LLVM_DEBUG(dbgs() << "********** Begin Constant Hoisting **********\n");
146  LLVM_DEBUG(dbgs() << "********** Function: " << Fn.getName() << '\n');
147 
148  bool MadeChange =
149  Impl.runImpl(Fn, getAnalysis<TargetTransformInfoWrapperPass>().getTTI(Fn),
150  getAnalysis<DominatorTreeWrapperPass>().getDomTree(),
152  ? &getAnalysis<BlockFrequencyInfoWrapperPass>().getBFI()
153  : nullptr,
154  Fn.getEntryBlock());
155 
156  if (MadeChange) {
157  LLVM_DEBUG(dbgs() << "********** Function after Constant Hoisting: "
158  << Fn.getName() << '\n');
159  LLVM_DEBUG(dbgs() << Fn);
160  }
161  LLVM_DEBUG(dbgs() << "********** End Constant Hoisting **********\n");
162 
163  return MadeChange;
164 }
165 
166 /// Find the constant materialization insertion point.
167 Instruction *ConstantHoistingPass::findMatInsertPt(Instruction *Inst,
168  unsigned Idx) const {
169  // If the operand is a cast instruction, then we have to materialize the
170  // constant before the cast instruction.
171  if (Idx != ~0U) {
172  Value *Opnd = Inst->getOperand(Idx);
173  if (auto CastInst = dyn_cast<Instruction>(Opnd))
174  if (CastInst->isCast())
175  return CastInst;
176  }
177 
178  // The simple and common case. This also includes constant expressions.
179  if (!isa<PHINode>(Inst) && !Inst->isEHPad())
180  return Inst;
181 
182  // We can't insert directly before a phi node or an eh pad. Insert before
183  // the terminator of the incoming or dominating block.
184  assert(Entry != Inst->getParent() && "PHI or landing pad in entry block!");
185  if (Idx != ~0U && isa<PHINode>(Inst))
186  return cast<PHINode>(Inst)->getIncomingBlock(Idx)->getTerminator();
187 
188  // This must be an EH pad. Iterate over immediate dominators until we find a
189  // non-EH pad. We need to skip over catchswitch blocks, which are both EH pads
190  // and terminators.
191  auto IDom = DT->getNode(Inst->getParent())->getIDom();
192  while (IDom->getBlock()->isEHPad()) {
193  assert(Entry != IDom->getBlock() && "eh pad in entry block");
194  IDom = IDom->getIDom();
195  }
196 
197  return IDom->getBlock()->getTerminator();
198 }
199 
200 /// Given \p BBs as input, find another set of BBs which collectively
201 /// dominates \p BBs and have the minimal sum of frequencies. Return the BB
202 /// set found in \p BBs.
204  BasicBlock *Entry,
206  assert(!BBs.count(Entry) && "Assume Entry is not in BBs");
207  // Nodes on the current path to the root.
209  // Candidates includes any block 'BB' in set 'BBs' that is not strictly
210  // dominated by any other blocks in set 'BBs', and all nodes in the path
211  // in the dominator tree from Entry to 'BB'.
213  for (auto BB : BBs) {
214  Path.clear();
215  // Walk up the dominator tree until Entry or another BB in BBs
216  // is reached. Insert the nodes on the way to the Path.
217  BasicBlock *Node = BB;
218  // The "Path" is a candidate path to be added into Candidates set.
219  bool isCandidate = false;
220  do {
221  Path.insert(Node);
222  if (Node == Entry || Candidates.count(Node)) {
223  isCandidate = true;
224  break;
225  }
226  assert(DT.getNode(Node)->getIDom() &&
227  "Entry doens't dominate current Node");
228  Node = DT.getNode(Node)->getIDom()->getBlock();
229  } while (!BBs.count(Node));
230 
231  // If isCandidate is false, Node is another Block in BBs dominating
232  // current 'BB'. Drop the nodes on the Path.
233  if (!isCandidate)
234  continue;
235 
236  // Add nodes on the Path into Candidates.
237  Candidates.insert(Path.begin(), Path.end());
238  }
239 
240  // Sort the nodes in Candidates in top-down order and save the nodes
241  // in Orders.
242  unsigned Idx = 0;
244  Orders.push_back(Entry);
245  while (Idx != Orders.size()) {
246  BasicBlock *Node = Orders[Idx++];
247  for (auto ChildDomNode : DT.getNode(Node)->getChildren()) {
248  if (Candidates.count(ChildDomNode->getBlock()))
249  Orders.push_back(ChildDomNode->getBlock());
250  }
251  }
252 
253  // Visit Orders in bottom-up order.
254  using InsertPtsCostPair =
255  std::pair<SmallPtrSet<BasicBlock *, 16>, BlockFrequency>;
256 
257  // InsertPtsMap is a map from a BB to the best insertion points for the
258  // subtree of BB (subtree not including the BB itself).
260  InsertPtsMap.reserve(Orders.size() + 1);
261  for (auto RIt = Orders.rbegin(); RIt != Orders.rend(); RIt++) {
262  BasicBlock *Node = *RIt;
263  bool NodeInBBs = BBs.count(Node);
264  SmallPtrSet<BasicBlock *, 16> &InsertPts = InsertPtsMap[Node].first;
265  BlockFrequency &InsertPtsFreq = InsertPtsMap[Node].second;
266 
267  // Return the optimal insert points in BBs.
268  if (Node == Entry) {
269  BBs.clear();
270  if (InsertPtsFreq > BFI.getBlockFreq(Node) ||
271  (InsertPtsFreq == BFI.getBlockFreq(Node) && InsertPts.size() > 1))
272  BBs.insert(Entry);
273  else
274  BBs.insert(InsertPts.begin(), InsertPts.end());
275  break;
276  }
277 
278  BasicBlock *Parent = DT.getNode(Node)->getIDom()->getBlock();
279  // Initially, ParentInsertPts is empty and ParentPtsFreq is 0. Every child
280  // will update its parent's ParentInsertPts and ParentPtsFreq.
281  SmallPtrSet<BasicBlock *, 16> &ParentInsertPts = InsertPtsMap[Parent].first;
282  BlockFrequency &ParentPtsFreq = InsertPtsMap[Parent].second;
283  // Choose to insert in Node or in subtree of Node.
284  // Don't hoist to EHPad because we may not find a proper place to insert
285  // in EHPad.
286  // If the total frequency of InsertPts is the same as the frequency of the
287  // target Node, and InsertPts contains more than one nodes, choose hoisting
288  // to reduce code size.
289  if (NodeInBBs ||
290  (!Node->isEHPad() &&
291  (InsertPtsFreq > BFI.getBlockFreq(Node) ||
292  (InsertPtsFreq == BFI.getBlockFreq(Node) && InsertPts.size() > 1)))) {
293  ParentInsertPts.insert(Node);
294  ParentPtsFreq += BFI.getBlockFreq(Node);
295  } else {
296  ParentInsertPts.insert(InsertPts.begin(), InsertPts.end());
297  ParentPtsFreq += InsertPtsFreq;
298  }
299  }
300 }
301 
302 /// Find an insertion point that dominates all uses.
303 SmallPtrSet<Instruction *, 8> ConstantHoistingPass::findConstantInsertionPoint(
304  const ConstantInfo &ConstInfo) const {
305  assert(!ConstInfo.RebasedConstants.empty() && "Invalid constant info entry.");
306  // Collect all basic blocks.
309  for (auto const &RCI : ConstInfo.RebasedConstants)
310  for (auto const &U : RCI.Uses)
311  BBs.insert(findMatInsertPt(U.Inst, U.OpndIdx)->getParent());
312 
313  if (BBs.count(Entry)) {
314  InsertPts.insert(&Entry->front());
315  return InsertPts;
316  }
317 
318  if (BFI) {
319  findBestInsertionSet(*DT, *BFI, Entry, BBs);
320  for (auto BB : BBs) {
321  BasicBlock::iterator InsertPt = BB->begin();
322  for (; isa<PHINode>(InsertPt) || InsertPt->isEHPad(); ++InsertPt)
323  ;
324  InsertPts.insert(&*InsertPt);
325  }
326  return InsertPts;
327  }
328 
329  while (BBs.size() >= 2) {
330  BasicBlock *BB, *BB1, *BB2;
331  BB1 = *BBs.begin();
332  BB2 = *std::next(BBs.begin());
333  BB = DT->findNearestCommonDominator(BB1, BB2);
334  if (BB == Entry) {
335  InsertPts.insert(&Entry->front());
336  return InsertPts;
337  }
338  BBs.erase(BB1);
339  BBs.erase(BB2);
340  BBs.insert(BB);
341  }
342  assert((BBs.size() == 1) && "Expected only one element.");
343  Instruction &FirstInst = (*BBs.begin())->front();
344  InsertPts.insert(findMatInsertPt(&FirstInst));
345  return InsertPts;
346 }
347 
348 /// Record constant integer ConstInt for instruction Inst at operand
349 /// index Idx.
350 ///
351 /// The operand at index Idx is not necessarily the constant integer itself. It
352 /// could also be a cast instruction or a constant expression that uses the
353 /// constant integer.
354 void ConstantHoistingPass::collectConstantCandidates(
355  ConstCandMapType &ConstCandMap, Instruction *Inst, unsigned Idx,
356  ConstantInt *ConstInt) {
357  unsigned Cost;
358  // Ask the target about the cost of materializing the constant for the given
359  // instruction and operand index.
360  if (auto IntrInst = dyn_cast<IntrinsicInst>(Inst))
361  Cost = TTI->getIntImmCost(IntrInst->getIntrinsicID(), Idx,
362  ConstInt->getValue(), ConstInt->getType());
363  else
364  Cost = TTI->getIntImmCost(Inst->getOpcode(), Idx, ConstInt->getValue(),
365  ConstInt->getType());
366 
367  // Ignore cheap integer constants.
368  if (Cost > TargetTransformInfo::TCC_Basic) {
369  ConstCandMapType::iterator Itr;
370  bool Inserted;
371  ConstPtrUnionType Cand = ConstInt;
372  std::tie(Itr, Inserted) = ConstCandMap.insert(std::make_pair(Cand, 0));
373  if (Inserted) {
374  ConstIntCandVec.push_back(ConstantCandidate(ConstInt));
375  Itr->second = ConstIntCandVec.size() - 1;
376  }
377  ConstIntCandVec[Itr->second].addUser(Inst, Idx, Cost);
378  LLVM_DEBUG(if (isa<ConstantInt>(Inst->getOperand(Idx))) dbgs()
379  << "Collect constant " << *ConstInt << " from " << *Inst
380  << " with cost " << Cost << '\n';
381  else dbgs() << "Collect constant " << *ConstInt
382  << " indirectly from " << *Inst << " via "
383  << *Inst->getOperand(Idx) << " with cost " << Cost
384  << '\n';);
385  }
386 }
387 
388 /// Record constant GEP expression for instruction Inst at operand index Idx.
389 void ConstantHoistingPass::collectConstantCandidates(
390  ConstCandMapType &ConstCandMap, Instruction *Inst, unsigned Idx,
391  ConstantExpr *ConstExpr) {
392  // TODO: Handle vector GEPs
393  if (ConstExpr->getType()->isVectorTy())
394  return;
395 
396  GlobalVariable *BaseGV = dyn_cast<GlobalVariable>(ConstExpr->getOperand(0));
397  if (!BaseGV)
398  return;
399 
400  // Get offset from the base GV.
401  PointerType *GVPtrTy = dyn_cast<PointerType>(BaseGV->getType());
402  IntegerType *PtrIntTy = DL->getIntPtrType(*Ctx, GVPtrTy->getAddressSpace());
403  APInt Offset(DL->getTypeSizeInBits(PtrIntTy), /*val*/0, /*isSigned*/true);
404  auto *GEPO = cast<GEPOperator>(ConstExpr);
405  if (!GEPO->accumulateConstantOffset(*DL, Offset))
406  return;
407 
408  if (!Offset.isIntN(32))
409  return;
410 
411  // A constant GEP expression that has a GlobalVariable as base pointer is
412  // usually lowered to a load from constant pool. Such operation is unlikely
413  // to be cheaper than compute it by <Base + Offset>, which can be lowered to
414  // an ADD instruction or folded into Load/Store instruction.
415  int Cost = TTI->getIntImmCost(Instruction::Add, 1, Offset, PtrIntTy);
416  ConstCandVecType &ExprCandVec = ConstGEPCandMap[BaseGV];
417  ConstCandMapType::iterator Itr;
418  bool Inserted;
419  ConstPtrUnionType Cand = ConstExpr;
420  std::tie(Itr, Inserted) = ConstCandMap.insert(std::make_pair(Cand, 0));
421  if (Inserted) {
422  ExprCandVec.push_back(ConstantCandidate(
423  ConstantInt::get(Type::getInt32Ty(*Ctx), Offset.getLimitedValue()),
424  ConstExpr));
425  Itr->second = ExprCandVec.size() - 1;
426  }
427  ExprCandVec[Itr->second].addUser(Inst, Idx, Cost);
428 }
429 
430 /// Check the operand for instruction Inst at index Idx.
431 void ConstantHoistingPass::collectConstantCandidates(
432  ConstCandMapType &ConstCandMap, Instruction *Inst, unsigned Idx) {
433  Value *Opnd = Inst->getOperand(Idx);
434 
435  // Visit constant integers.
436  if (auto ConstInt = dyn_cast<ConstantInt>(Opnd)) {
437  collectConstantCandidates(ConstCandMap, Inst, Idx, ConstInt);
438  return;
439  }
440 
441  // Visit cast instructions that have constant integers.
442  if (auto CastInst = dyn_cast<Instruction>(Opnd)) {
443  // Only visit cast instructions, which have been skipped. All other
444  // instructions should have already been visited.
445  if (!CastInst->isCast())
446  return;
447 
448  if (auto *ConstInt = dyn_cast<ConstantInt>(CastInst->getOperand(0))) {
449  // Pretend the constant is directly used by the instruction and ignore
450  // the cast instruction.
451  collectConstantCandidates(ConstCandMap, Inst, Idx, ConstInt);
452  return;
453  }
454  }
455 
456  // Visit constant expressions that have constant integers.
457  if (auto ConstExpr = dyn_cast<ConstantExpr>(Opnd)) {
458  // Handle constant gep expressions.
460  collectConstantCandidates(ConstCandMap, Inst, Idx, ConstExpr);
461 
462  // Only visit constant cast expressions.
463  if (!ConstExpr->isCast())
464  return;
465 
466  if (auto ConstInt = dyn_cast<ConstantInt>(ConstExpr->getOperand(0))) {
467  // Pretend the constant is directly used by the instruction and ignore
468  // the constant expression.
469  collectConstantCandidates(ConstCandMap, Inst, Idx, ConstInt);
470  return;
471  }
472  }
473 }
474 
475 /// Scan the instruction for expensive integer constants and record them
476 /// in the constant candidate vector.
477 void ConstantHoistingPass::collectConstantCandidates(
478  ConstCandMapType &ConstCandMap, Instruction *Inst) {
479  // Skip all cast instructions. They are visited indirectly later on.
480  if (Inst->isCast())
481  return;
482 
483  // Scan all operands.
484  for (unsigned Idx = 0, E = Inst->getNumOperands(); Idx != E; ++Idx) {
485  // The cost of materializing the constants (defined in
486  // `TargetTransformInfo::getIntImmCost`) for instructions which only take
487  // constant variables is lower than `TargetTransformInfo::TCC_Basic`. So
488  // it's safe for us to collect constant candidates from all IntrinsicInsts.
489  if (canReplaceOperandWithVariable(Inst, Idx) || isa<IntrinsicInst>(Inst)) {
490  collectConstantCandidates(ConstCandMap, Inst, Idx);
491  }
492  } // end of for all operands
493 }
494 
495 /// Collect all integer constants in the function that cannot be folded
496 /// into an instruction itself.
497 void ConstantHoistingPass::collectConstantCandidates(Function &Fn) {
498  ConstCandMapType ConstCandMap;
499  for (BasicBlock &BB : Fn)
500  for (Instruction &Inst : BB)
501  collectConstantCandidates(ConstCandMap, &Inst);
502 }
503 
504 // This helper function is necessary to deal with values that have different
505 // bit widths (APInt Operator- does not like that). If the value cannot be
506 // represented in uint64 we return an "empty" APInt. This is then interpreted
507 // as the value is not in range.
508 static Optional<APInt> calculateOffsetDiff(const APInt &V1, const APInt &V2) {
509  Optional<APInt> Res = None;
510  unsigned BW = V1.getBitWidth() > V2.getBitWidth() ?
511  V1.getBitWidth() : V2.getBitWidth();
512  uint64_t LimVal1 = V1.getLimitedValue();
513  uint64_t LimVal2 = V2.getLimitedValue();
514 
515  if (LimVal1 == ~0ULL || LimVal2 == ~0ULL)
516  return Res;
517 
518  uint64_t Diff = LimVal1 - LimVal2;
519  return APInt(BW, Diff, true);
520 }
521 
522 // From a list of constants, one needs to picked as the base and the other
523 // constants will be transformed into an offset from that base constant. The
524 // question is which we can pick best? For example, consider these constants
525 // and their number of uses:
526 //
527 // Constants| 2 | 4 | 12 | 42 |
528 // NumUses | 3 | 2 | 8 | 7 |
529 //
530 // Selecting constant 12 because it has the most uses will generate negative
531 // offsets for constants 2 and 4 (i.e. -10 and -8 respectively). If negative
532 // offsets lead to less optimal code generation, then there might be better
533 // solutions. Suppose immediates in the range of 0..35 are most optimally
534 // supported by the architecture, then selecting constant 2 is most optimal
535 // because this will generate offsets: 0, 2, 10, 40. Offsets 0, 2 and 10 are in
536 // range 0..35, and thus 3 + 2 + 8 = 13 uses are in range. Selecting 12 would
537 // have only 8 uses in range, so choosing 2 as a base is more optimal. Thus, in
538 // selecting the base constant the range of the offsets is a very important
539 // factor too that we take into account here. This algorithm calculates a total
540 // costs for selecting a constant as the base and substract the costs if
541 // immediates are out of range. It has quadratic complexity, so we call this
542 // function only when we're optimising for size and there are less than 100
543 // constants, we fall back to the straightforward algorithm otherwise
544 // which does not do all the offset calculations.
545 unsigned
546 ConstantHoistingPass::maximizeConstantsInRange(ConstCandVecType::iterator S,
547  ConstCandVecType::iterator E,
548  ConstCandVecType::iterator &MaxCostItr) {
549  unsigned NumUses = 0;
550 
551  if(!Entry->getParent()->optForSize() || std::distance(S,E) > 100) {
552  for (auto ConstCand = S; ConstCand != E; ++ConstCand) {
553  NumUses += ConstCand->Uses.size();
554  if (ConstCand->CumulativeCost > MaxCostItr->CumulativeCost)
555  MaxCostItr = ConstCand;
556  }
557  return NumUses;
558  }
559 
560  LLVM_DEBUG(dbgs() << "== Maximize constants in range ==\n");
561  int MaxCost = -1;
562  for (auto ConstCand = S; ConstCand != E; ++ConstCand) {
563  auto Value = ConstCand->ConstInt->getValue();
564  Type *Ty = ConstCand->ConstInt->getType();
565  int Cost = 0;
566  NumUses += ConstCand->Uses.size();
567  LLVM_DEBUG(dbgs() << "= Constant: " << ConstCand->ConstInt->getValue()
568  << "\n");
569 
570  for (auto User : ConstCand->Uses) {
571  unsigned Opcode = User.Inst->getOpcode();
572  unsigned OpndIdx = User.OpndIdx;
573  Cost += TTI->getIntImmCost(Opcode, OpndIdx, Value, Ty);
574  LLVM_DEBUG(dbgs() << "Cost: " << Cost << "\n");
575 
576  for (auto C2 = S; C2 != E; ++C2) {
578  C2->ConstInt->getValue(),
579  ConstCand->ConstInt->getValue());
580  if (Diff) {
581  const int ImmCosts =
582  TTI->getIntImmCodeSizeCost(Opcode, OpndIdx, Diff.getValue(), Ty);
583  Cost -= ImmCosts;
584  LLVM_DEBUG(dbgs() << "Offset " << Diff.getValue() << " "
585  << "has penalty: " << ImmCosts << "\n"
586  << "Adjusted cost: " << Cost << "\n");
587  }
588  }
589  }
590  LLVM_DEBUG(dbgs() << "Cumulative cost: " << Cost << "\n");
591  if (Cost > MaxCost) {
592  MaxCost = Cost;
593  MaxCostItr = ConstCand;
594  LLVM_DEBUG(dbgs() << "New candidate: " << MaxCostItr->ConstInt->getValue()
595  << "\n");
596  }
597  }
598  return NumUses;
599 }
600 
601 /// Find the base constant within the given range and rebase all other
602 /// constants with respect to the base constant.
603 void ConstantHoistingPass::findAndMakeBaseConstant(
604  ConstCandVecType::iterator S, ConstCandVecType::iterator E,
606  auto MaxCostItr = S;
607  unsigned NumUses = maximizeConstantsInRange(S, E, MaxCostItr);
608 
609  // Don't hoist constants that have only one use.
610  if (NumUses <= 1)
611  return;
612 
613  ConstantInt *ConstInt = MaxCostItr->ConstInt;
614  ConstantExpr *ConstExpr = MaxCostItr->ConstExpr;
615  ConstantInfo ConstInfo;
616  ConstInfo.BaseInt = ConstInt;
617  ConstInfo.BaseExpr = ConstExpr;
618  Type *Ty = ConstInt->getType();
619 
620  // Rebase the constants with respect to the base constant.
621  for (auto ConstCand = S; ConstCand != E; ++ConstCand) {
622  APInt Diff = ConstCand->ConstInt->getValue() - ConstInt->getValue();
623  Constant *Offset = Diff == 0 ? nullptr : ConstantInt::get(Ty, Diff);
624  Type *ConstTy =
625  ConstCand->ConstExpr ? ConstCand->ConstExpr->getType() : nullptr;
626  ConstInfo.RebasedConstants.push_back(
627  RebasedConstantInfo(std::move(ConstCand->Uses), Offset, ConstTy));
628  }
629  ConstInfoVec.push_back(std::move(ConstInfo));
630 }
631 
632 /// Finds and combines constant candidates that can be easily
633 /// rematerialized with an add from a common base constant.
634 void ConstantHoistingPass::findBaseConstants(GlobalVariable *BaseGV) {
635  // If BaseGV is nullptr, find base among candidate constant integers;
636  // Otherwise find base among constant GEPs that share the same BaseGV.
637  ConstCandVecType &ConstCandVec = BaseGV ?
638  ConstGEPCandMap[BaseGV] : ConstIntCandVec;
639  ConstInfoVecType &ConstInfoVec = BaseGV ?
640  ConstGEPInfoMap[BaseGV] : ConstIntInfoVec;
641 
642  // Sort the constants by value and type. This invalidates the mapping!
643  std::stable_sort(ConstCandVec.begin(), ConstCandVec.end(),
644  [](const ConstantCandidate &LHS, const ConstantCandidate &RHS) {
645  if (LHS.ConstInt->getType() != RHS.ConstInt->getType())
646  return LHS.ConstInt->getType()->getBitWidth() <
647  RHS.ConstInt->getType()->getBitWidth();
648  return LHS.ConstInt->getValue().ult(RHS.ConstInt->getValue());
649  });
650 
651  // Simple linear scan through the sorted constant candidate vector for viable
652  // merge candidates.
653  auto MinValItr = ConstCandVec.begin();
654  for (auto CC = std::next(ConstCandVec.begin()), E = ConstCandVec.end();
655  CC != E; ++CC) {
656  if (MinValItr->ConstInt->getType() == CC->ConstInt->getType()) {
657  Type *MemUseValTy = nullptr;
658  for (auto &U : CC->Uses) {
659  auto *UI = U.Inst;
660  if (LoadInst *LI = dyn_cast<LoadInst>(UI)) {
661  MemUseValTy = LI->getType();
662  break;
663  } else if (StoreInst *SI = dyn_cast<StoreInst>(UI)) {
664  // Make sure the constant is used as pointer operand of the StoreInst.
665  if (SI->getPointerOperand() == SI->getOperand(U.OpndIdx)) {
666  MemUseValTy = SI->getValueOperand()->getType();
667  break;
668  }
669  }
670  }
671 
672  // Check if the constant is in range of an add with immediate.
673  APInt Diff = CC->ConstInt->getValue() - MinValItr->ConstInt->getValue();
674  if ((Diff.getBitWidth() <= 64) &&
675  TTI->isLegalAddImmediate(Diff.getSExtValue()) &&
676  // Check if Diff can be used as offset in addressing mode of the user
677  // memory instruction.
678  (!MemUseValTy || TTI->isLegalAddressingMode(MemUseValTy,
679  /*BaseGV*/nullptr, /*BaseOffset*/Diff.getSExtValue(),
680  /*HasBaseReg*/true, /*Scale*/0)))
681  continue;
682  }
683  // We either have now a different constant type or the constant is not in
684  // range of an add with immediate anymore.
685  findAndMakeBaseConstant(MinValItr, CC, ConstInfoVec);
686  // Start a new base constant search.
687  MinValItr = CC;
688  }
689  // Finalize the last base constant search.
690  findAndMakeBaseConstant(MinValItr, ConstCandVec.end(), ConstInfoVec);
691 }
692 
693 /// Updates the operand at Idx in instruction Inst with the result of
694 /// instruction Mat. If the instruction is a PHI node then special
695 /// handling for duplicate values form the same incoming basic block is
696 /// required.
697 /// \return The update will always succeed, but the return value indicated if
698 /// Mat was used for the update or not.
699 static bool updateOperand(Instruction *Inst, unsigned Idx, Instruction *Mat) {
700  if (auto PHI = dyn_cast<PHINode>(Inst)) {
701  // Check if any previous operand of the PHI node has the same incoming basic
702  // block. This is a very odd case that happens when the incoming basic block
703  // has a switch statement. In this case use the same value as the previous
704  // operand(s), otherwise we will fail verification due to different values.
705  // The values are actually the same, but the variable names are different
706  // and the verifier doesn't like that.
707  BasicBlock *IncomingBB = PHI->getIncomingBlock(Idx);
708  for (unsigned i = 0; i < Idx; ++i) {
709  if (PHI->getIncomingBlock(i) == IncomingBB) {
710  Value *IncomingVal = PHI->getIncomingValue(i);
711  Inst->setOperand(Idx, IncomingVal);
712  return false;
713  }
714  }
715  }
716 
717  Inst->setOperand(Idx, Mat);
718  return true;
719 }
720 
721 /// Emit materialization code for all rebased constants and update their
722 /// users.
723 void ConstantHoistingPass::emitBaseConstants(Instruction *Base,
724  Constant *Offset,
725  Type *Ty,
726  const ConstantUser &ConstUser) {
727  Instruction *Mat = Base;
728 
729  // The same offset can be dereferenced to different types in nested struct.
730  if (!Offset && Ty && Ty != Base->getType())
731  Offset = ConstantInt::get(Type::getInt32Ty(*Ctx), 0);
732 
733  if (Offset) {
734  Instruction *InsertionPt = findMatInsertPt(ConstUser.Inst,
735  ConstUser.OpndIdx);
736  if (Ty) {
737  // Constant being rebased is a ConstantExpr.
738  PointerType *Int8PtrTy = Type::getInt8PtrTy(*Ctx,
739  cast<PointerType>(Ty)->getAddressSpace());
740  Base = new BitCastInst(Base, Int8PtrTy, "base_bitcast", InsertionPt);
741  Mat = GetElementPtrInst::Create(Int8PtrTy->getElementType(), Base,
742  Offset, "mat_gep", InsertionPt);
743  Mat = new BitCastInst(Mat, Ty, "mat_bitcast", InsertionPt);
744  } else
745  // Constant being rebased is a ConstantInt.
746  Mat = BinaryOperator::Create(Instruction::Add, Base, Offset,
747  "const_mat", InsertionPt);
748 
749  LLVM_DEBUG(dbgs() << "Materialize constant (" << *Base->getOperand(0)
750  << " + " << *Offset << ") in BB "
751  << Mat->getParent()->getName() << '\n'
752  << *Mat << '\n');
753  Mat->setDebugLoc(ConstUser.Inst->getDebugLoc());
754  }
755  Value *Opnd = ConstUser.Inst->getOperand(ConstUser.OpndIdx);
756 
757  // Visit constant integer.
758  if (isa<ConstantInt>(Opnd)) {
759  LLVM_DEBUG(dbgs() << "Update: " << *ConstUser.Inst << '\n');
760  if (!updateOperand(ConstUser.Inst, ConstUser.OpndIdx, Mat) && Offset)
761  Mat->eraseFromParent();
762  LLVM_DEBUG(dbgs() << "To : " << *ConstUser.Inst << '\n');
763  return;
764  }
765 
766  // Visit cast instruction.
767  if (auto CastInst = dyn_cast<Instruction>(Opnd)) {
768  assert(CastInst->isCast() && "Expected an cast instruction!");
769  // Check if we already have visited this cast instruction before to avoid
770  // unnecessary cloning.
771  Instruction *&ClonedCastInst = ClonedCastMap[CastInst];
772  if (!ClonedCastInst) {
773  ClonedCastInst = CastInst->clone();
774  ClonedCastInst->setOperand(0, Mat);
775  ClonedCastInst->insertAfter(CastInst);
776  // Use the same debug location as the original cast instruction.
777  ClonedCastInst->setDebugLoc(CastInst->getDebugLoc());
778  LLVM_DEBUG(dbgs() << "Clone instruction: " << *CastInst << '\n'
779  << "To : " << *ClonedCastInst << '\n');
780  }
781 
782  LLVM_DEBUG(dbgs() << "Update: " << *ConstUser.Inst << '\n');
783  updateOperand(ConstUser.Inst, ConstUser.OpndIdx, ClonedCastInst);
784  LLVM_DEBUG(dbgs() << "To : " << *ConstUser.Inst << '\n');
785  return;
786  }
787 
788  // Visit constant expression.
789  if (auto ConstExpr = dyn_cast<ConstantExpr>(Opnd)) {
790  if (ConstExpr->isGEPWithNoNotionalOverIndexing()) {
791  // Operand is a ConstantGEP, replace it.
792  updateOperand(ConstUser.Inst, ConstUser.OpndIdx, Mat);
793  return;
794  }
795 
796  // Aside from constant GEPs, only constant cast expressions are collected.
797  assert(ConstExpr->isCast() && "ConstExpr should be a cast");
798  Instruction *ConstExprInst = ConstExpr->getAsInstruction();
799  ConstExprInst->setOperand(0, Mat);
800  ConstExprInst->insertBefore(findMatInsertPt(ConstUser.Inst,
801  ConstUser.OpndIdx));
802 
803  // Use the same debug location as the instruction we are about to update.
804  ConstExprInst->setDebugLoc(ConstUser.Inst->getDebugLoc());
805 
806  LLVM_DEBUG(dbgs() << "Create instruction: " << *ConstExprInst << '\n'
807  << "From : " << *ConstExpr << '\n');
808  LLVM_DEBUG(dbgs() << "Update: " << *ConstUser.Inst << '\n');
809  if (!updateOperand(ConstUser.Inst, ConstUser.OpndIdx, ConstExprInst)) {
810  ConstExprInst->eraseFromParent();
811  if (Offset)
812  Mat->eraseFromParent();
813  }
814  LLVM_DEBUG(dbgs() << "To : " << *ConstUser.Inst << '\n');
815  return;
816  }
817 }
818 
819 /// Hoist and hide the base constant behind a bitcast and emit
820 /// materialization code for derived constants.
821 bool ConstantHoistingPass::emitBaseConstants(GlobalVariable *BaseGV) {
822  bool MadeChange = false;
824  BaseGV ? ConstGEPInfoMap[BaseGV] : ConstIntInfoVec;
825  for (auto const &ConstInfo : ConstInfoVec) {
826  SmallPtrSet<Instruction *, 8> IPSet = findConstantInsertionPoint(ConstInfo);
827  assert(!IPSet.empty() && "IPSet is empty");
828 
829  unsigned UsesNum = 0;
830  unsigned ReBasesNum = 0;
831  unsigned NotRebasedNum = 0;
832  for (Instruction *IP : IPSet) {
833  // First, collect constants depending on this IP of the base.
834  unsigned Uses = 0;
835  using RebasedUse = std::tuple<Constant *, Type *, ConstantUser>;
836  SmallVector<RebasedUse, 4> ToBeRebased;
837  for (auto const &RCI : ConstInfo.RebasedConstants) {
838  for (auto const &U : RCI.Uses) {
839  Uses++;
840  BasicBlock *OrigMatInsertBB =
841  findMatInsertPt(U.Inst, U.OpndIdx)->getParent();
842  // If Base constant is to be inserted in multiple places,
843  // generate rebase for U using the Base dominating U.
844  if (IPSet.size() == 1 ||
845  DT->dominates(IP->getParent(), OrigMatInsertBB))
846  ToBeRebased.push_back(RebasedUse(RCI.Offset, RCI.Ty, U));
847  }
848  }
849  UsesNum = Uses;
850 
851  // If only few constants depend on this IP of base, skip rebasing,
852  // assuming the base and the rebased have the same materialization cost.
853  if (ToBeRebased.size() < MinNumOfDependentToRebase) {
854  NotRebasedNum += ToBeRebased.size();
855  continue;
856  }
857 
858  // Emit an instance of the base at this IP.
859  Instruction *Base = nullptr;
860  // Hoist and hide the base constant behind a bitcast.
861  if (ConstInfo.BaseExpr) {
862  assert(BaseGV && "A base constant expression must have an base GV");
863  Type *Ty = ConstInfo.BaseExpr->getType();
864  Base = new BitCastInst(ConstInfo.BaseExpr, Ty, "const", IP);
865  } else {
866  IntegerType *Ty = ConstInfo.BaseInt->getType();
867  Base = new BitCastInst(ConstInfo.BaseInt, Ty, "const", IP);
868  }
869 
870  Base->setDebugLoc(IP->getDebugLoc());
871 
872  LLVM_DEBUG(dbgs() << "Hoist constant (" << *ConstInfo.BaseInt
873  << ") to BB " << IP->getParent()->getName() << '\n'
874  << *Base << '\n');
875 
876  // Emit materialization code for rebased constants depending on this IP.
877  for (auto const &R : ToBeRebased) {
878  Constant *Off = std::get<0>(R);
879  Type *Ty = std::get<1>(R);
880  ConstantUser U = std::get<2>(R);
881  emitBaseConstants(Base, Off, Ty, U);
882  ReBasesNum++;
883  // Use the same debug location as the last user of the constant.
885  Base->getDebugLoc(), U.Inst->getDebugLoc()));
886  }
887  assert(!Base->use_empty() && "The use list is empty!?");
888  assert(isa<Instruction>(Base->user_back()) &&
889  "All uses should be instructions.");
890  }
891  (void)UsesNum;
892  (void)ReBasesNum;
893  (void)NotRebasedNum;
894  // Expect all uses are rebased after rebase is done.
895  assert(UsesNum == (ReBasesNum + NotRebasedNum) &&
896  "Not all uses are rebased");
897 
898  NumConstantsHoisted++;
899 
900  // Base constant is also included in ConstInfo.RebasedConstants, so
901  // deduct 1 from ConstInfo.RebasedConstants.size().
902  NumConstantsRebased += ConstInfo.RebasedConstants.size() - 1;
903 
904  MadeChange = true;
905  }
906  return MadeChange;
907 }
908 
909 /// Check all cast instructions we made a copy of and remove them if they
910 /// have no more users.
911 void ConstantHoistingPass::deleteDeadCastInst() const {
912  for (auto const &I : ClonedCastMap)
913  if (I.first->use_empty())
914  I.first->eraseFromParent();
915 }
916 
917 /// Optimize expensive integer constants in the given function.
920  BasicBlock &Entry) {
921  this->TTI = &TTI;
922  this->DT = &DT;
923  this->BFI = BFI;
924  this->DL = &Fn.getParent()->getDataLayout();
925  this->Ctx = &Fn.getContext();
926  this->Entry = &Entry;
927  // Collect all constant candidates.
928  collectConstantCandidates(Fn);
929 
930  // Combine constants that can be easily materialized with an add from a common
931  // base constant.
932  if (!ConstIntCandVec.empty())
933  findBaseConstants(nullptr);
934  for (auto &MapEntry : ConstGEPCandMap)
935  if (!MapEntry.second.empty())
936  findBaseConstants(MapEntry.first);
937 
938  // Finally hoist the base constant and emit materialization code for dependent
939  // constants.
940  bool MadeChange = false;
941  if (!ConstIntInfoVec.empty())
942  MadeChange = emitBaseConstants(nullptr);
943  for (auto MapEntry : ConstGEPInfoMap)
944  if (!MapEntry.second.empty())
945  MadeChange |= emitBaseConstants(MapEntry.first);
946 
947 
948  // Cleanup dead instructions.
949  deleteDeadCastInst();
950 
951  return MadeChange;
952 }
953 
956  auto &DT = AM.getResult<DominatorTreeAnalysis>(F);
957  auto &TTI = AM.getResult<TargetIRAnalysis>(F);
960  : nullptr;
961  if (!runImpl(F, TTI, DT, BFI, F.getEntryBlock()))
962  return PreservedAnalyses::all();
963 
965  PA.preserveSet<CFGAnalyses>();
966  return PA;
967 }
const NoneType None
Definition: None.h:24
SymbolTableList< Instruction >::iterator eraseFromParent()
This method unlinks &#39;this&#39; from the containing basic block and deletes it.
Definition: Instruction.cpp:68
IntegerType * getType() const
getType - Specialize the getType() method to always return an IntegerType, which reduces the amount o...
Definition: Constants.h:172
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:770
This class represents lattice values for constants.
Definition: AllocatorList.h:24
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...
virtual void releaseMemory()
releaseMemory() - This member can be implemented by a pass if it wants to be able to release its memo...
Definition: Pass.cpp:96
static GetElementPtrInst * Create(Type *PointeeType, Value *Ptr, ArrayRef< Value *> IdxList, const Twine &NameStr="", Instruction *InsertBefore=nullptr)
Definition: Instructions.h:869
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:231
F(f)
An instruction for reading from memory.
Definition: Instructions.h:168
bool isVectorTy() const
True if this is an instance of VectorType.
Definition: Type.h:230
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:1509
iterator begin()
Instruction iterator methods.
Definition: BasicBlock.h:269
AnalysisUsage & addRequired()
#define INITIALIZE_PASS_DEPENDENCY(depName)
Definition: PassSupport.h:51
const DataLayout & getDataLayout() const
Get the data layout for the module&#39;s target platform.
Definition: Module.cpp:364
This is the base class for all instructions that perform data casts.
Definition: InstrTypes.h:349
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:2974
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:889
int64_t getSExtValue() const
Get sign extended value.
Definition: APInt.h:1575
Type * getType() const
All values are typed, get the type of this value.
Definition: Value.h:245
const T & getValue() const LLVM_LVALUE_FUNCTION
Definition: Optional.h:161
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:138
bool isGEPWithNoNotionalOverIndexing() const
Return true if this is a getelementptr expression and all the index operands are compile-time known i...
Definition: Constants.cpp:1153
unsigned getOpcode() const
Returns a member of one of the enums like Instruction::Add.
Definition: Instruction.h:126
An instruction for storing to memory.
Definition: Instructions.h:310
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:145
Value * getOperand(unsigned i) const
Definition: User.h:170
Class to represent pointers.
Definition: DerivedTypes.h:467
const BasicBlock & getEntryBlock() const
Definition: Function.h:640
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:419
Wrapper pass for TargetTransformInfo.
A set of analyses that are preserved following a run of a transformation pass.
Definition: PassManager.h:154
void setDebugLoc(DebugLoc Loc)
Set the debug location information for this instruction.
Definition: Instruction.h:308
LLVM Basic Block Representation.
Definition: BasicBlock.h:58
The instances of the Type class are immutable: once they are created, they are never changed...
Definition: Type.h:46
bool ult(const APInt &RHS) const
Unsigned less than comparison.
Definition: APInt.h:1185
DomTreeNodeBase * getIDom() const
static GCRegistry::Add< CoreCLRGC > E("coreclr", "CoreCLR-compatible GC")
This is an important base class in LLVM.
Definition: Constant.h:42
LLVM_NODISCARD bool empty() const
Definition: SmallPtrSet.h:92
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:2853
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:371
Represent the analysis usage information of a pass.
FunctionPass class - This class is used to implement most global optimizations.
Definition: Pass.h:285
unsigned getAddressSpace() const
Return the address space of the Pointer type.
Definition: DerivedTypes.h:495
void reserve(size_type NumEntries)
Grow the densemap so that it can contain at least NumEntries items before resizing again...
Definition: DenseMap.h:130
size_type count(ConstPtrType Ptr) const
count - Return 1 if the specified pointer is in the set, 0 otherwise.
Definition: SmallPtrSet.h:382
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:194
static PreservedAnalyses all()
Construct a special preserved set that preserves all passes.
Definition: PassManager.h:160
bool isCast() const
Definition: Instruction.h:134
size_t size() const
Definition: SmallVector.h:53
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:220
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:93
Analysis pass which computes BlockFrequencyInfo.
Iterator for intrusive lists based on ilist_node.
unsigned getNumOperands() const
Definition: User.h:192
This is the shared class of boolean and integer constants.
Definition: Constants.h:84
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:378
This is a &#39;vector&#39; (really, a variable-sized array), optimized for the case when the array is small...
Definition: SmallVector.h:847
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:64
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:622
void setPreservesCFG()
This function should be called by the pass, iff they do not:
Definition: Pass.cpp:286
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:175
raw_ostream & dbgs()
dbgs() - This returns a reference to a raw_ostream for debugging messages.
Definition: Debug.cpp:133
PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM)
Class for arbitrary precision integers.
Definition: APInt.h:70
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:115
const DebugLoc & getDebugLoc() const
Return the debug location for this node as a DebugLoc.
Definition: Instruction.h:311
iterator begin() const
Definition: SmallPtrSet.h:397
static IntegerType * getInt32Ty(LLVMContext &C)
Definition: Type.cpp:176
LLVM_NODISCARD bool empty() const
Definition: SmallVector.h:56
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:482
void preserveSet()
Mark an analysis set as preserved.
Definition: PassManager.h:190
StringRef getName() const
Return a constant reference to the value&#39;s name.
Definition: Value.cpp:215
const Function * getParent() const
Return the enclosing method, or null if none.
Definition: BasicBlock.h:107
#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:323
iterator end() const
Definition: SmallPtrSet.h:402
bool runImpl(Function &F, TargetTransformInfo &TTI, DominatorTree &DT, BlockFrequencyInfo *BFI, BasicBlock &Entry)
Optimize expensive integer constants in the given function.
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
The cost of a typical &#39;add&#39; instruction.
bool isEHPad() const
Return true if this basic block is an exception handling block.
Definition: BasicBlock.h:399
Module * getParent()
Get the module that this global value is contained inside of...
Definition: GlobalValue.h:566
LLVM Value Representation.
Definition: Value.h:73
bool isCast() const
Return true if this is a convert constant expression.
Definition: Constants.cpp:1145
bool isEHPad() const
Return true if the instruction is a variety of EH-block.
Definition: Instruction.h:573
StringRef - Represent a constant reference to a string, i.e.
Definition: StringRef.h:49
A container for analyses that lazily runs them and caches their results.
RebasedConstantListType RebasedConstants
Legacy analysis pass which computes a DominatorTree.
Definition: Dominators.h:260
This pass exposes codegen information to IR-level passes.
#define LLVM_DEBUG(X)
Definition: Debug.h:123
bool use_empty() const
Definition: Value.h:323
Type * getElementType() const
Definition: DerivedTypes.h:486
PointerType * getType() const
Global values are always pointers.
Definition: GlobalValue.h:274
const BasicBlock * getParent() const
Definition: Instruction.h:67
FunctionPass * createConstantHoistingPass()