Merge llvm 3.5.0 release from ^/vendor/llvm/dist, resolve conflicts, and

preserve our customizations, where necessary.

1 files changed, 602 insertions, 0 deletions

diff --git a/contrib/llvm/lib/Transforms/Scalar/ConstantHoisting.cpp b/contrib/llvm/lib/Transforms/Scalar/ConstantHoisting.cpp
new file mode 100644
index 0000000..763d02b
--- /dev/null
+++ b/contrib/llvm/lib/Transforms/Scalar/ConstantHoisting.cpp
@@ -0,0 +1,602 @@
+//===- ConstantHoisting.cpp - Prepare code for expensive constants --------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This pass identifies expensive constants to hoist and coalesces them to
+// better prepare it for SelectionDAG-based code generation. This works around
+// the limitations of the basic-block-at-a-time approach.
+//
+// First it scans all instructions for integer constants and calculates its
+// cost. If the constant can be folded into the instruction (the cost is
+// TCC_Free) or the cost is just a simple operation (TCC_BASIC), then we don't
+// consider it expensive and leave it alone. This is the default behavior and
+// the default implementation of getIntImmCost will always return TCC_Free.
+//
+// If the cost is more than TCC_BASIC, then the integer constant can't be folded
+// into the instruction and it might be beneficial to hoist the constant.
+// Similar constants are coalesced to reduce register pressure and
+// materialization code.
+//
+// When a constant is hoisted, it is also hidden behind a bitcast to force it to
+// be live-out of the basic block. Otherwise the constant would be just
+// duplicated and each basic block would have its own copy in the SelectionDAG.
+// The SelectionDAG recognizes such constants as opaque and doesn't perform
+// certain transformations on them, which would create a new expensive constant.
+//
+// This optimization is only applied to integer constants in instructions and
+// simple (this means not nested) constant cast expressions. For example:
+// %0 = load i64* inttoptr (i64 big_constant to i64*)
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Transforms/Scalar.h"
+#include "llvm/ADT/SmallSet.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/ADT/Statistic.h"
+#include "llvm/Analysis/TargetTransformInfo.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/Dominators.h"
+#include "llvm/IR/IntrinsicInst.h"
+#include "llvm/Pass.h"
+#include "llvm/Support/Debug.h"
+#include <tuple>
+
+using namespace llvm;
+
+#define DEBUG_TYPE "consthoist"
+
+STATISTIC(NumConstantsHoisted, "Number of constants hoisted");
+STATISTIC(NumConstantsRebased, "Number of constants rebased");
+
+namespace {
+struct ConstantUser;
+struct RebasedConstantInfo;
+
+typedef SmallVector<ConstantUser, 8> ConstantUseListType;
+typedef SmallVector<RebasedConstantInfo, 4> RebasedConstantListType;
+
+/// \brief Keeps track of the user of a constant and the operand index where the
+/// constant is used.
+struct ConstantUser {
+  Instruction *Inst;
+  unsigned OpndIdx;
+
+  ConstantUser(Instruction *Inst, unsigned Idx) : Inst(Inst), OpndIdx(Idx) { }
+};
+
+/// \brief Keeps track of a constant candidate and its uses.
+struct ConstantCandidate {
+  ConstantUseListType Uses;
+  ConstantInt *ConstInt;
+  unsigned CumulativeCost;
+
+  ConstantCandidate(ConstantInt *ConstInt)
+    : ConstInt(ConstInt), CumulativeCost(0) { }
+
+  /// \brief Add the user to the use list and update the cost.
+  void addUser(Instruction *Inst, unsigned Idx, unsigned Cost) {
+    CumulativeCost += Cost;
+    Uses.push_back(ConstantUser(Inst, Idx));
+  }
+};
+
+/// \brief This represents a constant that has been rebased with respect to a
+/// base constant. The difference to the base constant is recorded in Offset.
+struct RebasedConstantInfo {
+  ConstantUseListType Uses;
+  Constant *Offset;
+
+  RebasedConstantInfo(ConstantUseListType &&Uses, Constant *Offset)
+    : Uses(Uses), Offset(Offset) { }
+};
+
+/// \brief A base constant and all its rebased constants.
+struct ConstantInfo {
+  ConstantInt *BaseConstant;
+  RebasedConstantListType RebasedConstants;
+};
+
+/// \brief The constant hoisting pass.
+class ConstantHoisting : public FunctionPass {
+  typedef DenseMap<ConstantInt *, unsigned> ConstCandMapType;
+  typedef std::vector<ConstantCandidate> ConstCandVecType;
+
+  const TargetTransformInfo *TTI;
+  DominatorTree *DT;
+  BasicBlock *Entry;
+
+  /// Keeps track of constant candidates found in the function.
+  ConstCandVecType ConstCandVec;
+
+  /// Keep track of cast instructions we already cloned.
+  SmallDenseMap<Instruction *, Instruction *> ClonedCastMap;
+
+  /// These are the final constants we decided to hoist.
+  SmallVector<ConstantInfo, 8> ConstantVec;
+public:
+  static char ID; // Pass identification, replacement for typeid
+  ConstantHoisting() : FunctionPass(ID), TTI(nullptr), DT(nullptr),
+                       Entry(nullptr) {
+    initializeConstantHoistingPass(*PassRegistry::getPassRegistry());
+  }
+
+  bool runOnFunction(Function &Fn) override;
+
+  const char *getPassName() const override { return "Constant Hoisting"; }
+
+  void getAnalysisUsage(AnalysisUsage &AU) const override {
+    AU.setPreservesCFG();
+    AU.addRequired<DominatorTreeWrapperPass>();
+    AU.addRequired<TargetTransformInfo>();
+  }
+
+private:
+  /// \brief Initialize the pass.
+  void setup(Function &Fn) {
+    DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
+    TTI = &getAnalysis<TargetTransformInfo>();
+    Entry = &Fn.getEntryBlock();
+  }
+
+  /// \brief Cleanup.
+  void cleanup() {
+    ConstantVec.clear();
+    ClonedCastMap.clear();
+    ConstCandVec.clear();
+
+    TTI = nullptr;
+    DT = nullptr;
+    Entry = nullptr;
+  }
+
+  Instruction *findMatInsertPt(Instruction *Inst, unsigned Idx = ~0U) const;
+  Instruction *findConstantInsertionPoint(const ConstantInfo &ConstInfo) const;
+  void collectConstantCandidates(ConstCandMapType &ConstCandMap,
+                                 Instruction *Inst, unsigned Idx,
+                                 ConstantInt *ConstInt);
+  void collectConstantCandidates(ConstCandMapType &ConstCandMap,
+                                 Instruction *Inst);
+  void collectConstantCandidates(Function &Fn);
+  void findAndMakeBaseConstant(ConstCandVecType::iterator S,
+                               ConstCandVecType::iterator E);
+  void findBaseConstants();
+  void emitBaseConstants(Instruction *Base, Constant *Offset,
+                         const ConstantUser &ConstUser);
+  bool emitBaseConstants();
+  void deleteDeadCastInst() const;
+  bool optimizeConstants(Function &Fn);
+};
+}
+
+char ConstantHoisting::ID = 0;
+INITIALIZE_PASS_BEGIN(ConstantHoisting, "consthoist", "Constant Hoisting",
+                      false, false)
+INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
+INITIALIZE_AG_DEPENDENCY(TargetTransformInfo)
+INITIALIZE_PASS_END(ConstantHoisting, "consthoist", "Constant Hoisting",
+                    false, false)
+
+FunctionPass *llvm::createConstantHoistingPass() {
+  return new ConstantHoisting();
+}
+
+/// \brief Perform the constant hoisting optimization for the given function.
+bool ConstantHoisting::runOnFunction(Function &Fn) {
+  DEBUG(dbgs() << "********** Begin Constant Hoisting **********\n");
+  DEBUG(dbgs() << "********** Function: " << Fn.getName() << '\n');
+
+  setup(Fn);
+
+  bool MadeChange = optimizeConstants(Fn);
+
+  if (MadeChange) {
+    DEBUG(dbgs() << "********** Function after Constant Hoisting: "
+                 << Fn.getName() << '\n');
+    DEBUG(dbgs() << Fn);
+  }
+  DEBUG(dbgs() << "********** End Constant Hoisting **********\n");
+
+  cleanup();
+
+  return MadeChange;
+}
+
+
+/// \brief Find the constant materialization insertion point.
+Instruction *ConstantHoisting::findMatInsertPt(Instruction *Inst,
+                                               unsigned Idx) const {
+  // If the operand is a cast instruction, then we have to materialize the
+  // constant before the cast instruction.
+  if (Idx != ~0U) {
+    Value *Opnd = Inst->getOperand(Idx);
+    if (auto CastInst = dyn_cast<Instruction>(Opnd))
+      if (CastInst->isCast())
+        return CastInst;
+  }
+
+  // The simple and common case. This also includes constant expressions.
+  if (!isa<PHINode>(Inst) && !isa<LandingPadInst>(Inst))
+    return Inst;
+
+  // We can't insert directly before a phi node or landing pad. Insert before
+  // the terminator of the incoming or dominating block.
+  assert(Entry != Inst->getParent() && "PHI or landing pad in entry block!");
+  if (Idx != ~0U && isa<PHINode>(Inst))
+    return cast<PHINode>(Inst)->getIncomingBlock(Idx)->getTerminator();
+
+  BasicBlock *IDom = DT->getNode(Inst->getParent())->getIDom()->getBlock();
+  return IDom->getTerminator();
+}
+
+/// \brief Find an insertion point that dominates all uses.
+Instruction *ConstantHoisting::
+findConstantInsertionPoint(const ConstantInfo &ConstInfo) const {
+  assert(!ConstInfo.RebasedConstants.empty() && "Invalid constant info entry.");
+  // Collect all basic blocks.
+  SmallPtrSet<BasicBlock *, 8> BBs;
+  for (auto const &RCI : ConstInfo.RebasedConstants)
+    for (auto const &U : RCI.Uses)
+      BBs.insert(findMatInsertPt(U.Inst, U.OpndIdx)->getParent());
+
+  if (BBs.count(Entry))
+    return &Entry->front();
+
+  while (BBs.size() >= 2) {
+    BasicBlock *BB, *BB1, *BB2;
+    BB1 = *BBs.begin();
+    BB2 = *std::next(BBs.begin());
+    BB = DT->findNearestCommonDominator(BB1, BB2);
+    if (BB == Entry)
+      return &Entry->front();
+    BBs.erase(BB1);
+    BBs.erase(BB2);
+    BBs.insert(BB);
+  }
+  assert((BBs.size() == 1) && "Expected only one element.");
+  Instruction &FirstInst = (*BBs.begin())->front();
+  return findMatInsertPt(&FirstInst);
+}
+
+
+/// \brief Record constant integer ConstInt for instruction Inst at operand
+/// index Idx.
+///
+/// The operand at index Idx is not necessarily the constant integer itself. It
+/// could also be a cast instruction or a constant expression that uses the
+// constant integer.
+void ConstantHoisting::collectConstantCandidates(ConstCandMapType &ConstCandMap,
+                                                 Instruction *Inst,
+                                                 unsigned Idx,
+                                                 ConstantInt *ConstInt) {
+  unsigned Cost;
+  // Ask the target about the cost of materializing the constant for the given
+  // instruction and operand index.
+  if (auto IntrInst = dyn_cast<IntrinsicInst>(Inst))
+    Cost = TTI->getIntImmCost(IntrInst->getIntrinsicID(), Idx,
+                              ConstInt->getValue(), ConstInt->getType());
+  else
+    Cost = TTI->getIntImmCost(Inst->getOpcode(), Idx, ConstInt->getValue(),
+                              ConstInt->getType());
+
+  // Ignore cheap integer constants.
+  if (Cost > TargetTransformInfo::TCC_Basic) {
+    ConstCandMapType::iterator Itr;
+    bool Inserted;
+    std::tie(Itr, Inserted) = ConstCandMap.insert(std::make_pair(ConstInt, 0));
+    if (Inserted) {
+      ConstCandVec.push_back(ConstantCandidate(ConstInt));
+      Itr->second = ConstCandVec.size() - 1;
+    }
+    ConstCandVec[Itr->second].addUser(Inst, Idx, Cost);
+    DEBUG(if (isa<ConstantInt>(Inst->getOperand(Idx)))
+            dbgs() << "Collect constant " << *ConstInt << " from " << *Inst
+                   << " with cost " << Cost << '\n';
+          else
+          dbgs() << "Collect constant " << *ConstInt << " indirectly from "
+                 << *Inst << " via " << *Inst->getOperand(Idx) << " with cost "
+                 << Cost << '\n';
+    );
+  }
+}
+
+/// \brief Scan the instruction for expensive integer constants and record them
+/// in the constant candidate vector.
+void ConstantHoisting::collectConstantCandidates(ConstCandMapType &ConstCandMap,
+                                                 Instruction *Inst) {
+  // Skip all cast instructions. They are visited indirectly later on.
+  if (Inst->isCast())
+    return;
+
+  // Can't handle inline asm. Skip it.
+  if (auto Call = dyn_cast<CallInst>(Inst))
+    if (isa<InlineAsm>(Call->getCalledValue()))
+      return;
+
+  // Scan all operands.
+  for (unsigned Idx = 0, E = Inst->getNumOperands(); Idx != E; ++Idx) {
+    Value *Opnd = Inst->getOperand(Idx);
+
+    // Visit constant integers.
+    if (auto ConstInt = dyn_cast<ConstantInt>(Opnd)) {
+      collectConstantCandidates(ConstCandMap, Inst, Idx, ConstInt);
+      continue;
+    }
+
+    // Visit cast instructions that have constant integers.
+    if (auto CastInst = dyn_cast<Instruction>(Opnd)) {
+      // Only visit cast instructions, which have been skipped. All other
+      // instructions should have already been visited.
+      if (!CastInst->isCast())
+        continue;
+
+      if (auto *ConstInt = dyn_cast<ConstantInt>(CastInst->getOperand(0))) {
+        // Pretend the constant is directly used by the instruction and ignore
+        // the cast instruction.
+        collectConstantCandidates(ConstCandMap, Inst, Idx, ConstInt);
+        continue;
+      }
+    }
+
+    // Visit constant expressions that have constant integers.
+    if (auto ConstExpr = dyn_cast<ConstantExpr>(Opnd)) {
+      // Only visit constant cast expressions.
+      if (!ConstExpr->isCast())
+        continue;
+
+      if (auto ConstInt = dyn_cast<ConstantInt>(ConstExpr->getOperand(0))) {
+        // Pretend the constant is directly used by the instruction and ignore
+        // the constant expression.
+        collectConstantCandidates(ConstCandMap, Inst, Idx, ConstInt);
+        continue;
+      }
+    }
+  } // end of for all operands
+}
+
+/// \brief Collect all integer constants in the function that cannot be folded
+/// into an instruction itself.
+void ConstantHoisting::collectConstantCandidates(Function &Fn) {
+  ConstCandMapType ConstCandMap;
+  for (Function::iterator BB : Fn)
+    for (BasicBlock::iterator Inst : *BB)
+      collectConstantCandidates(ConstCandMap, Inst);
+}
+
+/// \brief Find the base constant within the given range and rebase all other
+/// constants with respect to the base constant.
+void ConstantHoisting::findAndMakeBaseConstant(ConstCandVecType::iterator S,
+                                               ConstCandVecType::iterator E) {
+  auto MaxCostItr = S;
+  unsigned NumUses = 0;
+  // Use the constant that has the maximum cost as base constant.
+  for (auto ConstCand = S; ConstCand != E; ++ConstCand) {
+    NumUses += ConstCand->Uses.size();
+    if (ConstCand->CumulativeCost > MaxCostItr->CumulativeCost)
+      MaxCostItr = ConstCand;
+  }
+
+  // Don't hoist constants that have only one use.
+  if (NumUses <= 1)
+    return;
+
+  ConstantInfo ConstInfo;
+  ConstInfo.BaseConstant = MaxCostItr->ConstInt;
+  Type *Ty = ConstInfo.BaseConstant->getType();
+
+  // Rebase the constants with respect to the base constant.
+  for (auto ConstCand = S; ConstCand != E; ++ConstCand) {
+    APInt Diff = ConstCand->ConstInt->getValue() -
+                 ConstInfo.BaseConstant->getValue();
+    Constant *Offset = Diff == 0 ? nullptr : ConstantInt::get(Ty, Diff);
+    ConstInfo.RebasedConstants.push_back(
+      RebasedConstantInfo(std::move(ConstCand->Uses), Offset));
+  }
+  ConstantVec.push_back(ConstInfo);
+}
+
+/// \brief Finds and combines constant candidates that can be easily
+/// rematerialized with an add from a common base constant.
+void ConstantHoisting::findBaseConstants() {
+  // Sort the constants by value and type. This invalidates the mapping!
+  std::sort(ConstCandVec.begin(), ConstCandVec.end(),
+            [](const ConstantCandidate &LHS, const ConstantCandidate &RHS) {
+    if (LHS.ConstInt->getType() != RHS.ConstInt->getType())
+      return LHS.ConstInt->getType()->getBitWidth() <
+             RHS.ConstInt->getType()->getBitWidth();
+    return LHS.ConstInt->getValue().ult(RHS.ConstInt->getValue());
+  });
+
+  // Simple linear scan through the sorted constant candidate vector for viable
+  // merge candidates.
+  auto MinValItr = ConstCandVec.begin();
+  for (auto CC = std::next(ConstCandVec.begin()), E = ConstCandVec.end();
+       CC != E; ++CC) {
+    if (MinValItr->ConstInt->getType() == CC->ConstInt->getType()) {
+      // Check if the constant is in range of an add with immediate.
+      APInt Diff = CC->ConstInt->getValue() - MinValItr->ConstInt->getValue();
+      if ((Diff.getBitWidth() <= 64) &&
+          TTI->isLegalAddImmediate(Diff.getSExtValue()))
+        continue;
+    }
+    // We either have now a different constant type or the constant is not in
+    // range of an add with immediate anymore.
+    findAndMakeBaseConstant(MinValItr, CC);
+    // Start a new base constant search.
+    MinValItr = CC;
+  }
+  // Finalize the last base constant search.
+  findAndMakeBaseConstant(MinValItr, ConstCandVec.end());
+}
+
+/// \brief Updates the operand at Idx in instruction Inst with the result of
+///        instruction Mat. If the instruction is a PHI node then special
+///        handling for duplicate values form the same incomming basic block is
+///        required.
+/// \return The update will always succeed, but the return value indicated if
+///         Mat was used for the update or not.
+static bool updateOperand(Instruction *Inst, unsigned Idx, Instruction *Mat) {
+  if (auto PHI = dyn_cast<PHINode>(Inst)) {
+    // Check if any previous operand of the PHI node has the same incoming basic
+    // block. This is a very odd case that happens when the incoming basic block
+    // has a switch statement. In this case use the same value as the previous
+    // operand(s), otherwise we will fail verification due to different values.
+    // The values are actually the same, but the variable names are different
+    // and the verifier doesn't like that.
+    BasicBlock *IncomingBB = PHI->getIncomingBlock(Idx);
+    for (unsigned i = 0; i < Idx; ++i) {
+      if (PHI->getIncomingBlock(i) == IncomingBB) {
+        Value *IncomingVal = PHI->getIncomingValue(i);
+        Inst->setOperand(Idx, IncomingVal);
+        return false;
+      }
+    }
+  }
+
+  Inst->setOperand(Idx, Mat);
+  return true;
+}
+
+/// \brief Emit materialization code for all rebased constants and update their
+/// users.
+void ConstantHoisting::emitBaseConstants(Instruction *Base, Constant *Offset,
+                                         const ConstantUser &ConstUser) {
+  Instruction *Mat = Base;
+  if (Offset) {
+    Instruction *InsertionPt = findMatInsertPt(ConstUser.Inst,
+                                               ConstUser.OpndIdx);
+    Mat = BinaryOperator::Create(Instruction::Add, Base, Offset,
+                                 "const_mat", InsertionPt);
+
+    DEBUG(dbgs() << "Materialize constant (" << *Base->getOperand(0)
+                 << " + " << *Offset << ") in BB "
+                 << Mat->getParent()->getName() << '\n' << *Mat << '\n');
+    Mat->setDebugLoc(ConstUser.Inst->getDebugLoc());
+  }
+  Value *Opnd = ConstUser.Inst->getOperand(ConstUser.OpndIdx);
+
+  // Visit constant integer.
+  if (isa<ConstantInt>(Opnd)) {
+    DEBUG(dbgs() << "Update: " << *ConstUser.Inst << '\n');
+    if (!updateOperand(ConstUser.Inst, ConstUser.OpndIdx, Mat) && Offset)
+      Mat->eraseFromParent();
+    DEBUG(dbgs() << "To    : " << *ConstUser.Inst << '\n');
+    return;
+  }
+
+  // Visit cast instruction.
+  if (auto CastInst = dyn_cast<Instruction>(Opnd)) {
+    assert(CastInst->isCast() && "Expected an cast instruction!");
+    // Check if we already have visited this cast instruction before to avoid
+    // unnecessary cloning.
+    Instruction *&ClonedCastInst = ClonedCastMap[CastInst];
+    if (!ClonedCastInst) {
+      ClonedCastInst = CastInst->clone();
+      ClonedCastInst->setOperand(0, Mat);
+      ClonedCastInst->insertAfter(CastInst);
+      // Use the same debug location as the original cast instruction.
+      ClonedCastInst->setDebugLoc(CastInst->getDebugLoc());
+      DEBUG(dbgs() << "Clone instruction: " << *CastInst << '\n'
+                   << "To               : " << *ClonedCastInst << '\n');
+    }
+
+    DEBUG(dbgs() << "Update: " << *ConstUser.Inst << '\n');
+    updateOperand(ConstUser.Inst, ConstUser.OpndIdx, ClonedCastInst);
+    DEBUG(dbgs() << "To    : " << *ConstUser.Inst << '\n');
+    return;
+  }
+
+  // Visit constant expression.
+  if (auto ConstExpr = dyn_cast<ConstantExpr>(Opnd)) {
+    Instruction *ConstExprInst = ConstExpr->getAsInstruction();
+    ConstExprInst->setOperand(0, Mat);
+    ConstExprInst->insertBefore(findMatInsertPt(ConstUser.Inst,
+                                                ConstUser.OpndIdx));
+
+    // Use the same debug location as the instruction we are about to update.
+    ConstExprInst->setDebugLoc(ConstUser.Inst->getDebugLoc());
+
+    DEBUG(dbgs() << "Create instruction: " << *ConstExprInst << '\n'
+                 << "From              : " << *ConstExpr << '\n');
+    DEBUG(dbgs() << "Update: " << *ConstUser.Inst << '\n');
+    if (!updateOperand(ConstUser.Inst, ConstUser.OpndIdx, ConstExprInst)) {
+      ConstExprInst->eraseFromParent();
+      if (Offset)
+        Mat->eraseFromParent();
+    }
+    DEBUG(dbgs() << "To    : " << *ConstUser.Inst << '\n');
+    return;
+  }
+}
+
+/// \brief Hoist and hide the base constant behind a bitcast and emit
+/// materialization code for derived constants.
+bool ConstantHoisting::emitBaseConstants() {
+  bool MadeChange = false;
+  for (auto const &ConstInfo : ConstantVec) {
+    // Hoist and hide the base constant behind a bitcast.
+    Instruction *IP = findConstantInsertionPoint(ConstInfo);
+    IntegerType *Ty = ConstInfo.BaseConstant->getType();
+    Instruction *Base =
+      new BitCastInst(ConstInfo.BaseConstant, Ty, "const", IP);
+    DEBUG(dbgs() << "Hoist constant (" << *ConstInfo.BaseConstant << ") to BB "
+                 << IP->getParent()->getName() << '\n' << *Base << '\n');
+    NumConstantsHoisted++;
+
+    // Emit materialization code for all rebased constants.
+    for (auto const &RCI : ConstInfo.RebasedConstants) {
+      NumConstantsRebased++;
+      for (auto const &U : RCI.Uses)
+        emitBaseConstants(Base, RCI.Offset, U);
+    }
+
+    // Use the same debug location as the last user of the constant.
+    assert(!Base->use_empty() && "The use list is empty!?");
+    assert(isa<Instruction>(Base->user_back()) &&
+           "All uses should be instructions.");
+    Base->setDebugLoc(cast<Instruction>(Base->user_back())->getDebugLoc());
+
+    // Correct for base constant, which we counted above too.
+    NumConstantsRebased--;
+    MadeChange = true;
+  }
+  return MadeChange;
+}
+
+/// \brief Check all cast instructions we made a copy of and remove them if they
+/// have no more users.
+void ConstantHoisting::deleteDeadCastInst() const {
+  for (auto const &I : ClonedCastMap)
+    if (I.first->use_empty())
+      I.first->eraseFromParent();
+}
+
+/// \brief Optimize expensive integer constants in the given function.
+bool ConstantHoisting::optimizeConstants(Function &Fn) {
+  // Collect all constant candidates.
+  collectConstantCandidates(Fn);
+
+  // There are no constant candidates to worry about.
+  if (ConstCandVec.empty())
+    return false;
+
+  // Combine constants that can be easily materialized with an add from a common
+  // base constant.
+  findBaseConstants();
+
+  // There are no constants to emit.
+  if (ConstantVec.empty())
+    return false;
+
+  // Finally hoist the base constant and emit materialization code for dependent
+  // constants.
+  bool MadeChange = emitBaseConstants();
+
+  // Cleanup dead instructions.
+  deleteDeadCastInst();
+
+  return MadeChange;
+}