[Constant Hoisting] Hoisting Constant GEP Expressions

[zzheng]

Summary

Leverage existing logic in constant hoisting pass so that constant gep expressions
sharing the same base global variable are transformed into the form of
[Base + Offset], where Base is a constant gep and Offset is an integer.

This transformation can effectively reduce constant pool entries in the backend.

[efriedma]

include/llvm/Transforms/Scalar/ConstantHoisting.h

81 ↗

(On Diff #162999)

Could use a comment explaining what ConstExpr and ConstInt represent.

110 ↗

(On Diff #162999)

Could use a comment explaining what BaseExpr and BaseInt represent.

111 ↗

(On Diff #162999)

I'm sort of confused by the usage of BaseTy; why does the type of the base matter? It just gets bitcast away later, anyway.

lib/Transforms/Scalar/ConstantHoisting.cpp

412 ↗

(On Diff #162999)

getIntImmCodeSizeCost returns either zero or one on ARM... so it's always less than SizeCost?

745 ↗

(On Diff #162999)

Please use bitcast+GEP+bitcast, instead of ptrtoint/inttoptr.

[zzheng]

Unfortunately bitcast + gep + bitcast will only change the constant GEP expr from multi-dimension to single dimension, and it's still a constant pool entry after lowering.

[efriedma]

lib/Transforms/Scalar/ConstantHoisting.cpp

407 ↗

(On Diff #163165)

This still seems weird; we only hoist if the cost is less than 3?

[zzheng]

lib/Transforms/Scalar/ConstantHoisting.cpp

407 ↗

(On Diff #163165)

We want to hoist when cost of hoisting is smaller than cost of not-hoisting.

Currently a constant GEP whose base pointer is a GV, is lowered to a CP entry. The initial value of Cost reflects cost of loading this CP entry.

If loading from CP is always more expensive than computing it by <base + offset>, perhaps we can get rid of this if condition?

[efriedma]

lib/Transforms/Scalar/ConstantHoisting.cpp

407 ↗

(On Diff #163165)

Making it unconditional is probably okay.

Well, we might not want to hoist if the offset is so small we aren't actually getting any benefit. (e.g. loading from [r0] and [r0, #4] isn't really better than loading from [r0, #8] and [r0, #12]).

[zzheng]

Updated version reflects discussion with Eli.

Added AArch64 llc test.

Turns out one of our internal changes is bloating code size on thumbv6m. Will upstream a follow up patch address that.

[zzheng]

lib/Transforms/Scalar/ConstantHoisting.cpp

407 ↗

(On Diff #163165)

This patch tries to change from loading a group of CP entries to loading one CP entry and loading the reset by <Base + Offset>.

However, that's the case on our internal tree. We have a patch that lowers constant GEPs to CP entries

[efriedma]

A few more comments with minor tweaks. Otherwise looks good.

include/llvm/Transforms/Scalar/ConstantHoisting.h

182 ↗

(On Diff #163603)

Dead declaration.

192 ↗

(On Diff #163603)

Don't use default arguments for functions like this... it's more confusing than helpful.

lib/Transforms/Scalar/ConstantHoisting.cpp

732 ↗

(On Diff #163603)

You probably should specify the address-space here, to the same address-space as Ty.

788 ↗

(On Diff #163603)

Could you add an assertion here assert(ConstExpr->isCast()), so it's clear this matches the code in collectConstantCandidates?

[zzheng]

Addressed Eli's comments.

[efriedma]

LGTM

lib/Transforms/Scalar/ConstantHoisting.cpp

733 ↗

(On Diff #163605)

cast<PointerType>(Ty)

llvm/trunk/include/llvm/Transforms/Scalar/ConstantHoisting.h

 // %0 = load i64* inttoptr (i64 big_constant to i64*)
 //
 //===----------------------------------------------------------------------===//
 
 #ifndef LLVM_TRANSFORMS_SCALAR_CONSTANTHOISTING_H
 #define LLVM_TRANSFORMS_SCALAR_CONSTANTHOISTING_H
 
 #include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/PointerUnion.h"
 #include "llvm/ADT/SmallPtrSet.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/IR/PassManager.h"
 #include <algorithm>
 #include <vector>
 
 namespace llvm {
 
 class BasicBlock;
 class BlockFrequencyInfo;
 class Constant;
 class ConstantInt;
+class ConstantExpr;
 class DominatorTree;
 class Function;
+class GlobalVariable;
 class Instruction;
 class TargetTransformInfo;
 
 /// A private "module" namespace for types and utilities used by
 /// ConstantHoisting. These are implementation details and should not be used by
 /// clients.
 namespace consthoist {
 
 /// 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) {}
 };
 
 using ConstantUseListType = SmallVector<ConstantUser, 8>;
 
 /// Keeps track of a constant candidate and its uses.
 struct ConstantCandidate {
   ConstantUseListType Uses;
+  // If the candidate is a ConstantExpr (currely only constant GEP expressions
+  // whose base pointers are GlobalVariables are supported), ConstInt records
+  // its offset from the base GV, ConstExpr tracks the candidate GEP expr.
   ConstantInt *ConstInt;
+  ConstantExpr *ConstExpr;
   unsigned CumulativeCost = 0;
 
-  ConstantCandidate(ConstantInt *ConstInt) : ConstInt(ConstInt) {}
+  ConstantCandidate(ConstantInt *ConstInt, ConstantExpr *ConstExpr=nullptr) :
+      ConstInt(ConstInt), ConstExpr(ConstExpr) {}
 
   /// 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));
   }
 };
 
 /// 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;
+  Type *Ty;
 
-  RebasedConstantInfo(ConstantUseListType &&Uses, Constant *Offset)
-    : Uses(std::move(Uses)), Offset(Offset) {}
+  RebasedConstantInfo(ConstantUseListType &&Uses, Constant *Offset,
+      Type *Ty=nullptr) : Uses(std::move(Uses)), Offset(Offset), Ty(Ty) {}
 };
 
 using RebasedConstantListType = SmallVector<RebasedConstantInfo, 4>;
 
 /// A base constant and all its rebased constants.
 struct ConstantInfo {
-  ConstantInt *BaseConstant;
+  // If the candidate is a ConstantExpr (currely only constant GEP expressions
+  // whose base pointers are GlobalVariables are supported), ConstInt records
+  // its offset from the base GV, ConstExpr tracks the candidate GEP expr.
+  ConstantInt *BaseInt;
+  ConstantExpr *BaseExpr;
   RebasedConstantListType RebasedConstants;
 };
 
 } // end namespace consthoist
 
 class ConstantHoistingPass : public PassInfoMixin<ConstantHoistingPass> {
 public:
   PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM);
 
   // Glue for old PM.
   bool runImpl(Function &F, TargetTransformInfo &TTI, DominatorTree &DT,
                BlockFrequencyInfo *BFI, BasicBlock &Entry);
 
   void releaseMemory() {
-    ConstantVec.clear();
     ClonedCastMap.clear();
-    ConstCandVec.clear();
+    ConstIntCandVec.clear();
+    for (auto MapEntry : ConstGEPCandMap)
+      MapEntry.second.clear();
+    ConstGEPCandMap.clear();
+    ConstIntInfoVec.clear();
+    for (auto MapEntry : ConstGEPInfoMap)
+      MapEntry.second.clear();
+    ConstGEPInfoMap.clear();
   }
 
 private:
-  using ConstCandMapType = DenseMap<ConstantInt *, unsigned>;
-  using ConstCandVecType = std::vector<consthoist::ConstantCandidate>;
+  using ConstPtrUnionType = PointerUnion<ConstantInt *, ConstantExpr *>;
+  using ConstCandMapType = DenseMap<ConstPtrUnionType, unsigned>;
 
   const TargetTransformInfo *TTI;
   DominatorTree *DT;
   BlockFrequencyInfo *BFI;
+  LLVMContext *Ctx;
+  const DataLayout *DL;
   BasicBlock *Entry;
 
   /// Keeps track of constant candidates found in the function.
-  ConstCandVecType ConstCandVec;
+  using ConstCandVecType = std::vector<consthoist::ConstantCandidate>;
+  using GVCandVecMapType = DenseMap<GlobalVariable *, ConstCandVecType>;
+  ConstCandVecType ConstIntCandVec;
+  GVCandVecMapType ConstGEPCandMap;
+
+  /// These are the final constants we decided to hoist.
+  using ConstInfoVecType = SmallVector<consthoist::ConstantInfo, 8>;
+  using GVInfoVecMapType = DenseMap<GlobalVariable *, ConstInfoVecType>;
+  ConstInfoVecType ConstIntInfoVec;
+  GVInfoVecMapType ConstGEPInfoMap;
 
   /// Keep track of cast instructions we already cloned.
   SmallDenseMap<Instruction *, Instruction *> ClonedCastMap;
 
-  /// These are the final constants we decided to hoist.
-  SmallVector<consthoist::ConstantInfo, 8> ConstantVec;
-
   Instruction *findMatInsertPt(Instruction *Inst, unsigned Idx = ~0U) const;
   SmallPtrSet<Instruction *, 8>
   findConstantInsertionPoint(const consthoist::ConstantInfo &ConstInfo) const;
   void collectConstantCandidates(ConstCandMapType &ConstCandMap,
                                  Instruction *Inst, unsigned Idx,
                                  ConstantInt *ConstInt);
   void collectConstantCandidates(ConstCandMapType &ConstCandMap,
+                                 Instruction *Inst, unsigned Idx,
+                                 ConstantExpr *ConstExpr);
+  void collectConstantCandidates(ConstCandMapType &ConstCandMap,
                                  Instruction *Inst, unsigned Idx);
   void collectConstantCandidates(ConstCandMapType &ConstCandMap,
                                  Instruction *Inst);
   void collectConstantCandidates(Function &Fn);
   void findAndMakeBaseConstant(ConstCandVecType::iterator S,
-                               ConstCandVecType::iterator E);
+                               ConstCandVecType::iterator E,
+      SmallVectorImpl<consthoist::ConstantInfo> &ConstInfoVec);
   unsigned maximizeConstantsInRange(ConstCandVecType::iterator S,
                                     ConstCandVecType::iterator E,
                                     ConstCandVecType::iterator &MaxCostItr);
-  void findBaseConstants();
-  void emitBaseConstants(Instruction *Base, Constant *Offset,
+  // If BaseGV is nullptr, find base among Constant Integer candidates;
+  // otherwise find base among constant GEPs sharing BaseGV as base pointer.
+  void findBaseConstants(GlobalVariable *BaseGV);
+  void emitBaseConstants(Instruction *Base, Constant *Offset, Type *Ty,
                          const consthoist::ConstantUser &ConstUser);
-  bool emitBaseConstants();
+  // If BaseGV is nullptr, emit Constant Integer base; otherwise emit
+  // constant GEP base.
+  bool emitBaseConstants(GlobalVariable *BaseGV);
   void deleteDeadCastInst() const;
   bool optimizeConstants(Function &Fn);
 };
 
 } // end namespace llvm
 
 #endif // LLVM_TRANSFORMS_SCALAR_CONSTANTHOISTING_H

llvm/trunk/lib/Transforms/Scalar/ConstantHoisting.cpp

 STATISTIC(NumConstantsRebased, "Number of constants rebased");
 
 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."));
 
+static cl::opt<bool> ConstHoistGEP(
+    "consthoist-gep", cl::init(false), cl::Hidden,
+    cl::desc("Try hoisting constant gep expressions"));
+
 namespace {
 
 /// The constant hoisting pass.
 class ConstantHoistingLegacyPass : public FunctionPass {
 public:
   static char ID; // Pass identification, replacement for typeid
 
   ConstantHoistingLegacyPass() : FunctionPass(ID) {
SmallPtrSet<Instruction *, 8> ConstantHoistingPass::findConstantInsertionPoint(
   return InsertPts;
 }
 
 /// 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.
+/// constant integer.
 void ConstantHoistingPass::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));
+    ConstPtrUnionType Cand = ConstInt;
+    std::tie(Itr, Inserted) = ConstCandMap.insert(std::make_pair(Cand, 0));
     if (Inserted) {
-      ConstCandVec.push_back(ConstantCandidate(ConstInt));
-      Itr->second = ConstCandVec.size() - 1;
+      ConstIntCandVec.push_back(ConstantCandidate(ConstInt));
+      Itr->second = ConstIntCandVec.size() - 1;
     }
-    ConstCandVec[Itr->second].addUser(Inst, Idx, Cost);
+    ConstIntCandVec[Itr->second].addUser(Inst, Idx, Cost);
     LLVM_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';);
   }
 }
 
+/// Record constant GEP expression for instruction Inst at operand index Idx.
+void ConstantHoistingPass::collectConstantCandidates(
+    ConstCandMapType &ConstCandMap, Instruction *Inst, unsigned Idx,
+    ConstantExpr *ConstExpr) {
+  // TODO: Handle vector GEPs
+  if (ConstExpr->getType()->isVectorTy())
+    return;
+
+  GlobalVariable *BaseGV = dyn_cast<GlobalVariable>(ConstExpr->getOperand(0));
+  if (!BaseGV)
+    return;
+
+  // Get offset from the base GV.
+  PointerType *GVPtrTy = dyn_cast<PointerType>(BaseGV->getType());
+  IntegerType *PtrIntTy = DL->getIntPtrType(*Ctx, GVPtrTy->getAddressSpace());
+  APInt Offset(DL->getTypeSizeInBits(PtrIntTy), /*val*/0, /*isSigned*/true);
+  auto *GEPO = cast<GEPOperator>(ConstExpr);
+  if (!GEPO->accumulateConstantOffset(*DL, Offset))
+    return;
+
+  if (!Offset.isIntN(32))
+    return;
+
+  // A constant GEP expression that has a GlobalVariable as base pointer is
+  // usually lowered to a load from constant pool. Such operation is unlikely
+  // to be cheaper than compute it by <Base + Offset>, which can be lowered to
+  // an ADD instruction or folded into Load/Store instruction.
+  int Cost = TTI->getIntImmCost(Instruction::Add, 1, Offset, PtrIntTy);
+  ConstCandVecType &ExprCandVec = ConstGEPCandMap[BaseGV];
+  ConstCandMapType::iterator Itr;
+  bool Inserted;
+  ConstPtrUnionType Cand = ConstExpr;
+  std::tie(Itr, Inserted) = ConstCandMap.insert(std::make_pair(Cand, 0));
+  if (Inserted) {
+    ExprCandVec.push_back(ConstantCandidate(
+        ConstantInt::get(Type::getInt32Ty(*Ctx), Offset.getLimitedValue()),
+        ConstExpr));
+    Itr->second = ExprCandVec.size() - 1;
+  }
+  ExprCandVec[Itr->second].addUser(Inst, Idx, Cost);
+}
+
 /// Check the operand for instruction Inst at index Idx.
 void ConstantHoistingPass::collectConstantCandidates(
     ConstCandMapType &ConstCandMap, Instruction *Inst, unsigned Idx) {
   Value *Opnd = Inst->getOperand(Idx);
 
   // Visit constant integers.
   if (auto ConstInt = dyn_cast<ConstantInt>(Opnd)) {
     collectConstantCandidates(ConstCandMap, Inst, Idx, ConstInt);
if (auto *ConstInt = dyn_cast<ConstantInt>(CastInst->getOperand(0))) {
       // the cast instruction.
       collectConstantCandidates(ConstCandMap, Inst, Idx, ConstInt);
       return;
     }
   }
 
   // Visit constant expressions that have constant integers.
   if (auto ConstExpr = dyn_cast<ConstantExpr>(Opnd)) {
+    // Handle constant gep expressions.
+    if (ConstHoistGEP && ConstExpr->isGEPWithNoNotionalOverIndexing())
+      collectConstantCandidates(ConstCandMap, Inst, Idx, ConstExpr);
+
     // Only visit constant cast expressions.
     if (!ConstExpr->isCast())
       return;
 
     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);
for (auto ConstCand = S; ConstCand != E; ++ConstCand) {
     }
   }
   return NumUses;
 }
 
 /// Find the base constant within the given range and rebase all other
 /// constants with respect to the base constant.
 void ConstantHoistingPass::findAndMakeBaseConstant(
-    ConstCandVecType::iterator S, ConstCandVecType::iterator E) {
+    ConstCandVecType::iterator S, ConstCandVecType::iterator E,
+    SmallVectorImpl<consthoist::ConstantInfo> &ConstInfoVec) {
   auto MaxCostItr = S;
   unsigned NumUses = maximizeConstantsInRange(S, E, MaxCostItr);
 
   // Don't hoist constants that have only one use.
   if (NumUses <= 1)
     return;
 
+  ConstantInt *ConstInt = MaxCostItr->ConstInt;
+  ConstantExpr *ConstExpr = MaxCostItr->ConstExpr;
   ConstantInfo ConstInfo;
-  ConstInfo.BaseConstant = MaxCostItr->ConstInt;
-  Type *Ty = ConstInfo.BaseConstant->getType();
+  ConstInfo.BaseInt = ConstInt;
+  ConstInfo.BaseExpr = ConstExpr;
+  Type *Ty = ConstInt->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();
+    APInt Diff = ConstCand->ConstInt->getValue() - ConstInt->getValue();
     Constant *Offset = Diff == 0 ? nullptr : ConstantInt::get(Ty, Diff);
+    Type *ConstTy =
+        ConstCand->ConstExpr ? ConstCand->ConstExpr->getType() : nullptr;
     ConstInfo.RebasedConstants.push_back(
-      RebasedConstantInfo(std::move(ConstCand->Uses), Offset));
+      RebasedConstantInfo(std::move(ConstCand->Uses), Offset, ConstTy));
   }
-  ConstantVec.push_back(std::move(ConstInfo));
+  ConstInfoVec.push_back(std::move(ConstInfo));
 }
 
 /// Finds and combines constant candidates that can be easily
 /// rematerialized with an add from a common base constant.
-void ConstantHoistingPass::findBaseConstants() {
+void ConstantHoistingPass::findBaseConstants(GlobalVariable *BaseGV) {
+  // If BaseGV is nullptr, find base among candidate constant integers;
+  // Otherwise find base among constant GEPs that share the same BaseGV.
+  ConstCandVecType &ConstCandVec = BaseGV ?
+      ConstGEPCandMap[BaseGV] : ConstIntCandVec;
+  ConstInfoVecType &ConstInfoVec = BaseGV ?
+      ConstGEPInfoMap[BaseGV] : ConstIntInfoVec;
+
   // Sort the constants by value and type. This invalidates the mapping!
   llvm::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());
   });
if (MinValItr->ConstInt->getType() == CC->ConstInt->getType()) {
           // memory instruction.
           (!MemUseValTy || TTI->isLegalAddressingMode(MemUseValTy,
            /*BaseGV*/nullptr, /*BaseOffset*/Diff.getSExtValue(),
            /*HasBaseReg*/true, /*Scale*/0)))
         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);
+    findAndMakeBaseConstant(MinValItr, CC, ConstInfoVec);
     // Start a new base constant search.
     MinValItr = CC;
   }
   // Finalize the last base constant search.
-  findAndMakeBaseConstant(MinValItr, ConstCandVec.end());
+  findAndMakeBaseConstant(MinValItr, ConstCandVec.end(), ConstInfoVec);
 }
 
 /// 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 incoming 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) {
   Inst->setOperand(Idx, Mat);
   return true;
 }
 
 /// Emit materialization code for all rebased constants and update their
 /// users.
 void ConstantHoistingPass::emitBaseConstants(Instruction *Base,
                                              Constant *Offset,
+                                             Type *Ty,
                                              const ConstantUser &ConstUser) {
   Instruction *Mat = Base;
+
+  // The same offset can be dereferenced to different types in nested struct.
+  if (!Offset && Ty && Ty != Base->getType())
+    Offset = ConstantInt::get(Type::getInt32Ty(*Ctx), 0);
+
   if (Offset) {
     Instruction *InsertionPt = findMatInsertPt(ConstUser.Inst,
                                                ConstUser.OpndIdx);
+    if (Ty) {
+      // Constant being rebased is a ConstantExpr.
+      PointerType *Int8PtrTy = Type::getInt8PtrTy(*Ctx,
+          cast<PointerType>(Ty)->getAddressSpace());
+      Base = new BitCastInst(Base, Int8PtrTy, "base_bitcast", InsertionPt);
+      Mat = GetElementPtrInst::Create(Int8PtrTy->getElementType(), Base,
+          Offset, "mat_gep", InsertionPt);
+      Mat = new BitCastInst(Mat, Ty, "mat_bitcast", InsertionPt);
+    } else
+      // Constant being rebased is a ConstantInt.
       Mat = BinaryOperator::Create(Instruction::Add, Base, Offset,
                                  "const_mat", InsertionPt);
 
     LLVM_DEBUG(dbgs() << "Materialize constant (" << *Base->getOperand(0)
                       << " + " << *Offset << ") in BB "
                       << Mat->getParent()->getName() << '\n'
                       << *Mat << '\n');
     Mat->setDebugLoc(ConstUser.Inst->getDebugLoc());
   }
if (auto CastInst = dyn_cast<Instruction>(Opnd)) {
     LLVM_DEBUG(dbgs() << "Update: " << *ConstUser.Inst << '\n');
     updateOperand(ConstUser.Inst, ConstUser.OpndIdx, ClonedCastInst);
     LLVM_DEBUG(dbgs() << "To    : " << *ConstUser.Inst << '\n');
     return;
   }
 
   // Visit constant expression.
   if (auto ConstExpr = dyn_cast<ConstantExpr>(Opnd)) {
+    if (ConstExpr->isGEPWithNoNotionalOverIndexing()) {
+      // Operand is a ConstantGEP, replace it.
+      updateOperand(ConstUser.Inst, ConstUser.OpndIdx, Mat);
+      return;
+    }
+
+    // Aside from constant GEPs, only constant cast expressions are collected.
+    assert(ConstExpr->isCast() && "ConstExpr should be a cast");
     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());
 
     LLVM_DEBUG(dbgs() << "Create instruction: " << *ConstExprInst << '\n'
                       << "From              : " << *ConstExpr << '\n');
     LLVM_DEBUG(dbgs() << "Update: " << *ConstUser.Inst << '\n');
     if (!updateOperand(ConstUser.Inst, ConstUser.OpndIdx, ConstExprInst)) {
       ConstExprInst->eraseFromParent();
       if (Offset)
         Mat->eraseFromParent();
     }
     LLVM_DEBUG(dbgs() << "To    : " << *ConstUser.Inst << '\n');
     return;
   }
 }
 
 /// Hoist and hide the base constant behind a bitcast and emit
 /// materialization code for derived constants.
-bool ConstantHoistingPass::emitBaseConstants() {
+bool ConstantHoistingPass::emitBaseConstants(GlobalVariable *BaseGV) {
   bool MadeChange = false;
-  for (auto const &ConstInfo : ConstantVec) {
-    // Hoist and hide the base constant behind a bitcast.
+  SmallVectorImpl<consthoist::ConstantInfo> &ConstInfoVec =
+      BaseGV ? ConstGEPInfoMap[BaseGV] : ConstIntInfoVec;
+  for (auto const &ConstInfo : ConstInfoVec) {
     SmallPtrSet<Instruction *, 8> IPSet = findConstantInsertionPoint(ConstInfo);
     assert(!IPSet.empty() && "IPSet is empty");
 
     unsigned UsesNum = 0;
     unsigned ReBasesNum = 0;
     for (Instruction *IP : IPSet) {
-      IntegerType *Ty = ConstInfo.BaseConstant->getType();
-      Instruction *Base =
-          new BitCastInst(ConstInfo.BaseConstant, Ty, "const", IP);
+      Instruction *Base = nullptr;
+      // Hoist and hide the base constant behind a bitcast.
+      if (ConstInfo.BaseExpr) {
+        assert(BaseGV && "A base constant expression must have an base GV");
+        Type *Ty = ConstInfo.BaseExpr->getType();
+        Base = new BitCastInst(ConstInfo.BaseExpr, Ty, "const", IP);
+      } else {
+        IntegerType *Ty = ConstInfo.BaseInt->getType();
+        Base = new BitCastInst(ConstInfo.BaseInt, Ty, "const", IP);
+      }
 
       Base->setDebugLoc(IP->getDebugLoc());
 
-      LLVM_DEBUG(dbgs() << "Hoist constant (" << *ConstInfo.BaseConstant
+      LLVM_DEBUG(dbgs() << "Hoist constant (" << *ConstInfo.BaseInt
                         << ") to BB " << IP->getParent()->getName() << '\n'
                         << *Base << '\n');
 
       // Emit materialization code for all rebased constants.
       unsigned Uses = 0;
       for (auto const &RCI : ConstInfo.RebasedConstants) {
         for (auto const &U : RCI.Uses) {
           Uses++;
           BasicBlock *OrigMatInsertBB =
               findMatInsertPt(U.Inst, U.OpndIdx)->getParent();
           // If Base constant is to be inserted in multiple places,
           // generate rebase for U using the Base dominating U.
           if (IPSet.size() == 1 ||
               DT->dominates(Base->getParent(), OrigMatInsertBB)) {
-            emitBaseConstants(Base, RCI.Offset, U);
+            emitBaseConstants(Base, RCI.Offset, RCI.Ty, U);
             ReBasesNum++;
           }
 
-          Base->setDebugLoc(DILocation::getMergedLocation(Base->getDebugLoc(), U.Inst->getDebugLoc()));
+          Base->setDebugLoc(DILocation::getMergedLocation(
+              Base->getDebugLoc(), U.Inst->getDebugLoc()));
         }
       }
       UsesNum = Uses;
 
       // 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.");
     }
     (void)UsesNum;
     (void)ReBasesNum;
     // Expect all uses are rebased after rebase is done.
     assert(UsesNum == ReBasesNum && "Not all uses are rebased");
 
     NumConstantsHoisted++;
 
     // Base constant is also included in ConstInfo.RebasedConstants, so
     // deduct 1 from ConstInfo.RebasedConstants.size().
-    NumConstantsRebased = ConstInfo.RebasedConstants.size() - 1;
+    NumConstantsRebased += ConstInfo.RebasedConstants.size() - 1;
 
     MadeChange = true;
   }
   return MadeChange;
 }
 
 /// Check all cast instructions we made a copy of and remove them if they
 /// have no more users.
 void ConstantHoistingPass::deleteDeadCastInst() const {
   for (auto const &I : ClonedCastMap)
     if (I.first->use_empty())
       I.first->eraseFromParent();
 }
 
 /// Optimize expensive integer constants in the given function.
 bool ConstantHoistingPass::runImpl(Function &Fn, TargetTransformInfo &TTI,
                                    DominatorTree &DT, BlockFrequencyInfo *BFI,
                                    BasicBlock &Entry) {
   this->TTI = &TTI;
   this->DT = &DT;
   this->BFI = BFI;
+  this->DL = &Fn.getParent()->getDataLayout();
+  this->Ctx = &Fn.getContext();
   this->Entry = &Entry;
   // 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;
+  if (!ConstIntCandVec.empty())
+    findBaseConstants(nullptr);
+  for (auto &MapEntry : ConstGEPCandMap)
+    if (!MapEntry.second.empty())
+      findBaseConstants(MapEntry.first);
 
   // Finally hoist the base constant and emit materialization code for dependent
   // constants.
-  bool MadeChange = emitBaseConstants();
+  bool MadeChange = false;
+  if (!ConstIntInfoVec.empty())
+    MadeChange = emitBaseConstants(nullptr);
+  for (auto MapEntry : ConstGEPInfoMap)
+    if (!MapEntry.second.empty())
+      MadeChange |= emitBaseConstants(MapEntry.first);
+
 
   // Cleanup dead instructions.
   deleteDeadCastInst();
 
   return MadeChange;
 }
 
 PreservedAnalyses ConstantHoistingPass::run(Function &F,

llvm/trunk/test/CodeGen/AArch64/consthoist-gep.ll

+; RUN: llc -mtriple=aarch64-none-unknown-linuxeabi -consthoist-gep %s -o - | FileCheck %s
+
+; CHECK-NOT: adrp    x10, global+332
+; CHECK-NOT: add     x10, x10, :lo12:global+332
+; CHECK: adrp    x10, global+528
+; CHECK-NEXT: add     x10, x10, :lo12:global+528
+
+%struct.blam = type { %struct.bar, %struct.bar.0, %struct.wobble, %struct.wombat, i8, i16, %struct.snork.2, %struct.foo, %struct.snork.3, %struct.wobble.4, %struct.quux, [9 x i16], %struct.spam, %struct.zot }
+%struct.bar = type { i8, i8, %struct.snork }
+%struct.snork = type { i16, i8, i8 }
+%struct.bar.0 = type { i8, i8, i16, i8, i8, %struct.barney }
+%struct.barney = type { i8, i8, i8, i8 }
+%struct.wobble = type { i8, i8, %struct.eggs, %struct.bar.1 }
+%struct.eggs = type { i8, i8, i8 }
+%struct.bar.1 = type { i8, i8, i8, i8 }
+%struct.wombat = type { i8, i8, i16, i32, i32, i32, i32 }
+%struct.snork.2 = type { i8, i8, i8 }
+%struct.foo = type { [12 x i32], [12 x i32], [4 x i32], i8, i8, i8, i8, i8, i8, i8, i8 }
+%struct.snork.3 = type { i16, i8, i8, i8, i8, i8, i8, i8, i8, i8, i8, i8, i8, i8, i8, i16 }
+%struct.wobble.4 = type { i32, i32, i32, i32, i32, i32, i16, i16, i8, i8, i16, i32, i32, i16, i8, i8 }
+%struct.quux = type { i32, %struct.foo.5, i8, i8, i8, i8, i32, %struct.snork.6, %struct.foo.7, [16 x i8], i16, i16, i8, i8, i8, i8, i32, i32, i32 }
+%struct.foo.5 = type { i16, i8, i8 }
+%struct.snork.6 = type { i16, i8, i8 }
+%struct.foo.7 = type { i8, i8, i8, i8, i8, i8, i8, i8, i8, i8, i8, i8, i8, i8, i8, i8 }
+%struct.spam = type { i8, i8 }
+%struct.zot = type { [5 x i32], [3 x i32], [6 x i32], [3 x i32], [2 x i32], [4 x i32], [3 x i32], [2 x i32], [4 x i32], [5 x i32], [3 x i32], [6 x i32], [1 x i32], i32, i32, i32, i32, i32, i32 }
+
+@global = external dso_local local_unnamed_addr global %struct.blam, align 4
+
+; Function Attrs: norecurse nounwind optsize ssp
+define dso_local void @blam() local_unnamed_addr #0 {
+bb:
+  %tmp = load i8, i8* getelementptr inbounds (%struct.blam, %struct.blam* @global, i32 0, i32 7, i32 9), align 2, !tbaa !3
+  %tmp1 = and i8 %tmp, 1
+  %tmp2 = icmp eq i8 %tmp1, 0
+  br i1 %tmp2, label %bb3, label %bb19
+
+bb3:                                              ; preds = %bb
+  %tmp4 = load volatile i32, i32* inttoptr (i32 805874688 to i32*), align 1024, !tbaa !23
+  store i32 %tmp4, i32* getelementptr inbounds (%struct.blam, %struct.blam* @global, i32 0, i32 13, i32 0, i32 0), align 4, !tbaa !23
+  %tmp5 = load volatile i32, i32* inttoptr (i32 805874692 to i32*), align 4, !tbaa !23
+  %tmp6 = and i32 %tmp5, 65535
+  store i32 %tmp6, i32* getelementptr inbounds (%struct.blam, %struct.blam* @global, i32 0, i32 13, i32 0, i32 1), align 4, !tbaa !23
+  %tmp7 = load volatile i32, i32* inttoptr (i32 805874696 to i32*), align 8, !tbaa !23
+  %tmp8 = and i32 %tmp7, 522133279
+  store i32 %tmp8, i32* getelementptr inbounds (%struct.blam, %struct.blam* @global, i32 0, i32 13, i32 0, i32 2), align 4, !tbaa !23
+  %tmp9 = load volatile i32, i32* inttoptr (i32 805874700 to i32*), align 4, !tbaa !23
+  %tmp10 = and i32 %tmp9, 522133279
+  store i32 %tmp10, i32* getelementptr inbounds (%struct.blam, %struct.blam* @global, i32 0, i32 13, i32 0, i32 3), align 4, !tbaa !23
+  %tmp11 = load volatile i32, i32* inttoptr (i32 805874860 to i32*), align 4, !tbaa !23
+  %tmp12 = and i32 %tmp11, 16777215
+  store i32 %tmp12, i32* getelementptr inbounds (%struct.blam, %struct.blam* @global, i32 0, i32 13, i32 15), align 4, !tbaa !24
+  %tmp13 = load volatile i32, i32* inttoptr (i32 805874864 to i32*), align 16, !tbaa !23
+  %tmp14 = and i32 %tmp13, 16777215
+  store i32 %tmp14, i32* getelementptr inbounds (%struct.blam, %struct.blam* @global, i32 0, i32 13, i32 16), align 4, !tbaa !25
+  %tmp15 = load volatile i32, i32* inttoptr (i32 805874868 to i32*), align 4, !tbaa !23
+  %tmp16 = and i32 %tmp15, 16777215
+  store i32 %tmp16, i32* getelementptr inbounds (%struct.blam, %struct.blam* @global, i32 0, i32 13, i32 17), align 4, !tbaa !26
+  %tmp17 = load volatile i32, i32* inttoptr (i32 805874872 to i32*), align 8, !tbaa !23
+  %tmp18 = and i32 %tmp17, 16777215
+  store i32 %tmp18, i32* getelementptr inbounds (%struct.blam, %struct.blam* @global, i32 0, i32 13, i32 18), align 4, !tbaa !27
+  br label %bb19
+
+bb19:                                             ; preds = %bb3, %bb
+  ret void
+}
+
+attributes #0 = { norecurse nounwind optsize ssp "correctly-rounded-divide-sqrt-fp-math"="false" "disable-tail-calls"="false" "less-precise-fpmad"="false" "no-frame-pointer-elim"="false" "no-infs-fp-math"="false" "no-jump-tables"="false" "no-nans-fp-math"="false" "no-signed-zeros-fp-math"="false" "no-trapping-math"="false" "stack-protector-buffer-size"="8" "unsafe-fp-math"="false" "use-soft-float"="false" }
+
+!llvm.module.flags = !{!0, !1}
+!llvm.ident = !{!2}
+
+!0 = !{i32 1, !"wchar_size", i32 4}
+!1 = !{i32 1, !"min_enum_size", i32 1}
+!2 = !{!"Snapdragon LLVM ARM Compiler 8.0.0 (based on LLVM 8.0.0)"}
+!3 = !{!4, !6, i64 174}
+!4 = !{!"", !5, i64 0, !10, i64 6, !12, i64 16, !14, i64 28, !6, i64 48, !9, i64 50, !13, i64 52, !16, i64 56, !17, i64 176, !18, i64 196, !19, i64 240, !6, i64 312, !21, i64 330, !22, i64 332}
+!5 = !{!"", !6, i64 0, !6, i64 1, !8, i64 2}
+!6 = !{!"omnipotent char", !7, i64 0}
+!7 = !{!"Simple C/C++ TBAA"}
+!8 = !{!"", !9, i64 0, !6, i64 2, !6, i64 3}
+!9 = !{!"short", !6, i64 0}
+!10 = !{!"", !6, i64 0, !6, i64 1, !9, i64 2, !6, i64 4, !6, i64 5, !11, i64 6}
+!11 = !{!"", !6, i64 0, !6, i64 1, !6, i64 2, !6, i64 3}
+!12 = !{!"", !6, i64 0, !6, i64 1, !13, i64 2, !11, i64 5}
+!13 = !{!"", !6, i64 0, !6, i64 1, !6, i64 2}
+!14 = !{!"", !6, i64 0, !6, i64 1, !9, i64 2, !15, i64 4, !15, i64 8, !15, i64 12, !15, i64 16}
+!15 = !{!"long", !6, i64 0}
+!16 = !{!"", !6, i64 0, !6, i64 48, !6, i64 96, !6, i64 112, !6, i64 113, !6, i64 114, !6, i64 115, !6, i64 116, !6, i64 117, !6, i64 118, !6, i64 119}
+!17 = !{!"", !9, i64 0, !6, i64 2, !6, i64 3, !6, i64 4, !6, i64 5, !6, i64 6, !6, i64 7, !6, i64 8, !6, i64 9, !6, i64 10, !6, i64 11, !6, i64 12, !6, i64 13, !6, i64 14, !6, i64 15, !9, i64 16}
+!18 = !{!"", !15, i64 0, !15, i64 4, !15, i64 8, !15, i64 12, !15, i64 16, !15, i64 20, !9, i64 24, !9, i64 26, !6, i64 28, !6, i64 29, !9, i64 30, !15, i64 32, !15, i64 36, !9, i64 40, !6, i64 42, !6, i64 43}
+!19 = !{!"", !15, i64 0, !8, i64 4, !6, i64 8, !6, i64 9, !6, i64 10, !6, i64 11, !15, i64 12, !8, i64 16, !20, i64 20, !6, i64 36, !9, i64 52, !9, i64 54, !6, i64 56, !6, i64 57, !6, i64 58, !6, i64 59, !15, i64 60, !15, i64 64, !15, i64 68}
+!20 = !{!"", !6, i64 0, !6, i64 1, !6, i64 2, !6, i64 3, !6, i64 4, !6, i64 5, !6, i64 6, !6, i64 7, !6, i64 8, !6, i64 9, !6, i64 10, !6, i64 11, !6, i64 12, !6, i64 13, !6, i64 14, !6, i64 15}
+!21 = !{!"", !6, i64 0, !6, i64 1}
+!22 = !{!"", !6, i64 0, !6, i64 20, !6, i64 32, !6, i64 56, !6, i64 68, !6, i64 76, !6, i64 92, !6, i64 104, !6, i64 112, !6, i64 128, !6, i64 148, !6, i64 160, !6, i64 184, !15, i64 188, !15, i64 192, !15, i64 196, !15, i64 200, !15, i64 204, !15, i64 208}
+!23 = !{!15, !15, i64 0}
+!24 = !{!4, !15, i64 528}
+!25 = !{!4, !15, i64 532}
+!26 = !{!4, !15, i64 536}
+!27 = !{!4, !15, i64 540}

llvm/trunk/test/Transforms/ConstantHoisting/AArch64/const-hoist-gep.ll

+; RUN: opt -consthoist -consthoist-gep -S -o - %s | FileCheck %s
+
+target triple = "aarch64-none--musleabi"
+
+; Check that constant GEP expressions are rewritten to one-dimensional
+; (single-index) GEPs, whose base poiner is a multi-dimensional GEP.
+; CHECK:  %const = bitcast i32* getelementptr inbounds (%0, %0* @global, i32 0, i32 4, i32 0, i32 0) to i32*
+; CHECK-NEXT:  store i32 undef, i32* %const, align 4
+
+; CHECK-NEXT:  %[[BC1:[a-z0-9_]+]] = bitcast i32* %const to i8*
+; CHECK-NEXT:  %[[M1:[a-z0-9_]+]] = getelementptr i8, i8* %[[BC1]], i32 4
+; CHECK-NEXT:  %[[BC2:[a-z0-9_]+]] = bitcast i8* %[[M1]] to i32*
+; CHECK-NEXT:  store i32 undef, i32* %[[BC2]], align 4
+
+; CHECK-NEXT:  %[[BC3:[a-z0-9_]+]] = bitcast i32* %const to i8*
+; CHECK-NEXT:  %[[M2:[a-z0-9_]+]] = getelementptr i8, i8* %[[BC3]], i32 160
+; CHECK-NEXT:  %[[BC4:[a-z0-9_]+]] = bitcast i8* %[[M2]] to i32*
+; CHECK-NEXT:  store i32 undef, i32* %[[BC4]], align 4
+
+; CHECK-NEXT:  %[[BC5:[a-z0-9_]+]] = bitcast i32* %const to i8*
+; CHECK-NEXT:  %[[M3:[a-z0-9_]+]] = getelementptr i8, i8* %[[BC5]], i32 164
+; CHECK-NEXT:  %[[BC6:[a-z0-9_]+]] = bitcast i8* %[[M3]] to i32*
+; CHECK-NEXT:  store i32 undef, i32* %[[BC6]], align 4
+
+%0 = type { %1, %2, [9 x i16], %6, %7 }
+%1 = type { i32, i32, i32, i32, i32, i32, i16, i16, i8, i8, i16, i32, i32, i16, i8, i8 }
+%2 = type { i32, %3, i8, i8, i8, i8, i32, %4, %5, [16 x i8], i16, i16, i8, i8, i8, i8, i32, i32, i32 }
+%3 = type { i16, i8, i8 }
+%4 = type { i16, i8, i8 }
+%5 = type { i8, i8, i8, i8, i8, i8, i8, i8, i8, i8, i8, i8, i8, i8, i8, i8 }
+%6 = type { i8, i8 }
+%7 = type { [5 x i32], [3 x i32], [6 x i32], [3 x i32], [2 x i32], [4 x i32], [3 x i32], [2 x i32], [4 x i32], [5 x i32], [3 x i32], [6 x i32], [1 x i32], i32, i32, i32, i32, i32, i32 }
+
+@global = external dso_local local_unnamed_addr global %0, align 4
+
+define dso_local void @zot() {
+bb:
+  store i32 undef, i32* getelementptr inbounds (%0, %0* @global, i32 0, i32 4, i32 0, i32 0), align 4
+  store i32 undef, i32* getelementptr inbounds (%0, %0* @global, i32 0, i32 4, i32 0, i32 1), align 4
+  store i32 undef, i32* getelementptr inbounds (%0, %0* @global, i32 0, i32 4, i32 11, i32 0), align 4
+  store i32 undef, i32* getelementptr inbounds (%0, %0* @global, i32 0, i32 4, i32 11, i32 1), align 4
+  ret void
+}
+

llvm/trunk/test/Transforms/ConstantHoisting/ARM/const-hoist-gep.ll

+; RUN: opt -consthoist -consthoist-gep -S -o - %s | FileCheck %s
+
+target datalayout = "e-m:e-p:32:32-i64:64-v128:64:128-a:0:32-n32-S64"
+target triple = "thumbv6m-none--musleabi"
+
+; Check that constant GEP expressions are rewritten to one-dimensional
+; (single-index) GEPs, whose base poiner is a multi-dimensional GEP.
+; CHECK-DAG:  %[[C1:const[0-9]?]] = bitcast i32* getelementptr inbounds (%0, %0* @global, i32 0, i32 4, i32 11, i32 0) to i32*
+; CHECK-DAG:  %[[C2:const[0-9]?]] = bitcast i32* getelementptr inbounds (%0, %0* @global, i32 0, i32 4, i32 0, i32 0) to i32*
+
+; CHECK:  store i32 undef, i32* %[[C2]], align 4
+; CHECK-NEXT:  %[[BC1:[a-z0-9_]+]] = bitcast i32* %[[C2]] to i8*
+; CHECK-NEXT:  %[[M1:[a-z0-9_]+]] = getelementptr i8, i8* %[[BC1]], i32 4
+; CHECK-NEXT:  %[[BC2:[a-z0-9_]+]] = bitcast i8* %[[M1]] to i32*
+; CHECK-NEXT:  store i32 undef, i32* %[[BC2]], align 4
+
+; CHECK-NEXT:  store i32 undef, i32* %[[C1]], align 4
+; CHECK-NEXT:  %[[BC3:[a-z0-9_]+]] = bitcast i32* %[[C1]] to i8*
+; CHECK-NEXT:  %[[M2:[a-z0-9_]+]] = getelementptr i8, i8* %[[BC3]], i32 4
+; CHECK-NEXT:  %[[BC4:[a-z0-9_]+]] = bitcast i8* %[[M2]] to i32*
+; CHECK-NEXT:  store i32 undef, i32* %[[BC4]], align 4
+
+%0 = type { %1, %2, [9 x i16], %6, %7 }
+%1 = type { i32, i32, i32, i32, i32, i32, i16, i16, i8, i8, i16, i32, i32, i16, i8, i8 }
+%2 = type { i32, %3, i8, i8, i8, i8, i32, %4, %5, [16 x i8], i16, i16, i8, i8, i8, i8, i32, i32, i32 }
+%3 = type { i16, i8, i8 }
+%4 = type { i16, i8, i8 }
+%5 = type { i8, i8, i8, i8, i8, i8, i8, i8, i8, i8, i8, i8, i8, i8, i8, i8 }
+%6 = type { i8, i8 }
+%7 = type { [5 x i32], [3 x i32], [6 x i32], [3 x i32], [2 x i32], [4 x i32], [3 x i32], [2 x i32], [4 x i32], [5 x i32], [3 x i32], [6 x i32], [1 x i32], i32, i32, i32, i32, i32, i32 }
+
+@global = external dso_local local_unnamed_addr global %0, align 4
+
+define dso_local void @zot() {
+bb:
+  store i32 undef, i32* getelementptr inbounds (%0, %0* @global, i32 0, i32 4, i32 0, i32 0), align 4
+  store i32 undef, i32* getelementptr inbounds (%0, %0* @global, i32 0, i32 4, i32 0, i32 1), align 4
+  store i32 undef, i32* getelementptr inbounds (%0, %0* @global, i32 0, i32 4, i32 11, i32 0), align 4
+  store i32 undef, i32* getelementptr inbounds (%0, %0* @global, i32 0, i32 4, i32 11, i32 1), align 4
+  ret void
+}
+

llvm/trunk/test/Transforms/ConstantHoisting/ARM/same-offset-multi-types.ll

+; RUN: opt -consthoist -consthoist-gep -S -o - %s | FileCheck %s
+
+target datalayout = "e-m:e-p:32:32-i64:64-v128:64:128-a:0:32-n32-S64"
+target triple = "thumbv6m-none--musleabi"
+
+; Check that for the same offset from the base constant, different types are materialized separately.
+; CHECK:  %const = bitcast %5** getelementptr inbounds (%0, %0* @global, i32 0, i32 2, i32 0) to %5**
+; CHECK:  %tmp = load %5*, %5** %const, align 4
+; CHECK:  %base_bitcast = bitcast %5** %const to i8*
+; CHECK:  %mat_gep = getelementptr i8, i8* %base_bitcast, i32 0
+; CHECK:  %mat_bitcast = bitcast i8* %mat_gep to %4*
+; CHECK:  tail call void undef(%5* nonnull %tmp, %4* %mat_bitcast)
+
+%0 = type { [16 x %1], %2, %4, [16 x %5], %6, %7, i32, [4 x i32], [8 x %3], i8, i8, i8, i8, i8, i8, i8, %8, %11, %11*, i32, i16, i8, i8, i8, i8, i8, i8, [15 x i16], i8, i8, [23 x %12], i8, i8*, i8, %13, i8, i8 }
+%1 = type { i32, i32, i8, i8, i8, i8, i8, i8, i8, i8 }
+%2 = type { %3*, i16, i16, i16 }
+%3 = type { [4 x i32] }
+%4 = type { %5*, %5*, i8 }
+%5 = type { [4 x i32], i8*, i8, i8 }
+%6 = type { i8, [4 x i32] }
+%7 = type { i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32 }
+%8 = type { [16 x %9], %9*, %9*, %9*, %9*, %11, %11, %11, i8, i8, i8, i8 }
+%9 = type { %1, %11, %11, %9*, %9*, %10, i8, i8, i8, i8 }
+%10 = type { i32, i16 }
+%11 = type { %11*, %11* }
+%12 = type { i8, i16, i32 }
+%13 = type { i32, i32, i8 }
+
+@global = external dso_local global %0, align 4
+
+; Function Attrs: nounwind optsize ssp
+define dso_local void @zot() {
+bb:
+  br i1 undef, label %bb2, label %bb1
+
+bb1:                                              ; preds = %bb
+  %tmp = load %5*, %5** getelementptr inbounds (%0, %0* @global, i32 0, i32 2, i32 0), align 4
+  tail call void undef(%5* nonnull %tmp, %4* getelementptr inbounds (%0, %0* @global, i32 0, i32 2))
+  unreachable
+
+bb2:                                              ; preds = %bb
+  ret void
+}
+