[ConstantFolding] Always return something from ConstantFoldConstant

[nikic]

Summary

Spin-off from D75407. As described there, ConstantFoldConstant() currently returns null for non-ConstantExpr/ConstantVector inputs, but otherwise always returns non-null, independently of whether any folding has happened or not.

This is confusing and makes consumer code more complicated. I would expect either that ConstantFoldConstant() returns only if it actually folded something, or that it always returns non-null. I'm going to the latter possibility here, which appears to be more useful considering existing usage.

[efriedma]

Nice cleanup! LGTM

lib/Transforms/InstCombine/InstCombineShifts.cpp

619 ↗

(On Diff #247950)

Maybe this code was written before we were doing folding in IRBuilder?

[nikic]

lib/Transforms/InstCombine/InstCombineShifts.cpp

619 ↗

(On Diff #247950)

That seems likely. I've double checked that this really does get folded without the call and dropped it in rG293d813020d7.

llvm/include/llvm/Analysis/ConstantFolding.h

 /// ConstantFoldInstruction - Try to constant fold the specified instruction.
 /// If successful, the constant result is returned, if not, null is returned.
 /// Note that this fails if not all of the operands are constant.  Otherwise,
 /// this function can only fail when attempting to fold instructions like loads
 /// and stores, which have no constant expression form.
 Constant *ConstantFoldInstruction(Instruction *I, const DataLayout &DL,
                                   const TargetLibraryInfo *TLI = nullptr);
 
-/// ConstantFoldConstant - Attempt to fold the constant using the
-/// specified DataLayout.
-/// If successful, the constant result is returned, if not, null is returned.
+/// ConstantFoldConstant - Fold the constant using the specified DataLayout.
+/// This function always returns a non-null constant: Either the folding result,
+/// or the original constant if further folding is not possible.
 Constant *ConstantFoldConstant(const Constant *C, const DataLayout &DL,
                                const TargetLibraryInfo *TLI = nullptr);
 
 /// ConstantFoldInstOperands - Attempt to constant fold an instruction with the
 /// specified operands.  If successful, the constant result is returned, if not,
 /// null is returned.  Note that this function can fail when attempting to
 /// fold instructions like loads and stores, which have no constant expression
 /// form.

llvm/include/llvm/Analysis/TargetFolder.h

 class DataLayout;
 
 /// TargetFolder - Create constants with target dependent folding.
 class TargetFolder final : public IRBuilderFolder {
   const DataLayout &DL;
 
   /// Fold - Fold the constant using target specific information.
   Constant *Fold(Constant *C) const {
-    if (Constant *CF = ConstantFoldConstant(C, DL))
-      return CF;
-    return C;
+    return ConstantFoldConstant(C, DL);
   }
 
   virtual void anchor();
 
 public:
   explicit TargetFolder(const DataLayout &DL) : DL(DL) {}
 
   //===--------------------------------------------------------------------===//

llvm/lib/Analysis/ConstantFolding.cpp

if ((i == 1 ||
       NewIdxs.push_back(Ops[i]);
   }
 
   if (!Any)
     return nullptr;
 
   Constant *C = ConstantExpr::getGetElementPtr(
       SrcElemTy, Ops[0], NewIdxs, /*InBounds=*/false, InRangeIndex);
-  if (Constant *Folded = ConstantFoldConstant(C, DL, TLI))
-    C = Folded;
-
-  return C;
+  return ConstantFoldConstant(C, DL, TLI);
 }
 
 /// Strip the pointer casts, but preserve the address space information.
 Constant *StripPtrCastKeepAS(Constant *Ptr, Type *&ElemTy) {
   assert(Ptr->getType()->isPointerTy() && "Not a pointer type");
   auto *OldPtrTy = cast<PointerType>(Ptr->getType());
   Ptr = cast<Constant>(Ptr->stripPointerCasts());
   auto *NewPtrTy = cast<PointerType>(Ptr->getType());
for (unsigned i = 1, e = Ops.size(); i != e; ++i)
           auto *CE = dyn_cast<ConstantExpr>(Ops[1]);
           assert((!CE || CE->getType() == IntIdxTy) &&
                  "CastGEPIndices didn't canonicalize index types!");
           if (CE && CE->getOpcode() == Instruction::Sub &&
               CE->getOperand(0)->isNullValue()) {
             Constant *Res = ConstantExpr::getPtrToInt(Ptr, CE->getType());
             Res = ConstantExpr::getSub(Res, CE->getOperand(1));
             Res = ConstantExpr::getIntToPtr(Res, ResTy);
-            if (auto *FoldedRes = ConstantFoldConstant(Res, DL, TLI))
-              Res = FoldedRes;
-            return Res;
+            return ConstantFoldConstant(Res, DL, TLI);
           }
         }
         return nullptr;
       }
 
   unsigned BitWidth = DL.getTypeSizeInBits(IntIdxTy);
   APInt Offset =
       APInt(BitWidth,

 
 namespace {
 
 Constant *
 ConstantFoldConstantImpl(const Constant *C, const DataLayout &DL,
                          const TargetLibraryInfo *TLI,
                          SmallDenseMap<Constant *, Constant *> &FoldedOps) {
   if (!isa<ConstantVector>(C) && !isa<ConstantExpr>(C))
-    return nullptr;
+    return const_cast<Constant *>(C);
 
   SmallVector<Constant *, 8> Ops;
-  for (const Use &NewU : C->operands()) {
-    auto *NewC = cast<Constant>(&NewU);
+  for (const Use &OldU : C->operands()) {
+    Constant *OldC = cast<Constant>(&OldU);
+    Constant *NewC = OldC;
     // Recursively fold the ConstantExpr's operands. If we have already folded
     // a ConstantExpr, we don't have to process it again.
-    if (isa<ConstantVector>(NewC) || isa<ConstantExpr>(NewC)) {
-      auto It = FoldedOps.find(NewC);
+    if (isa<ConstantVector>(OldC) || isa<ConstantExpr>(OldC)) {
+      auto It = FoldedOps.find(OldC);
       if (It == FoldedOps.end()) {
-        if (auto *FoldedC =
-                ConstantFoldConstantImpl(NewC, DL, TLI, FoldedOps)) {
-          FoldedOps.insert({NewC, FoldedC});
-          NewC = FoldedC;
-        } else {
-          FoldedOps.insert({NewC, NewC});
-        }
+        NewC = ConstantFoldConstantImpl(OldC, DL, TLI, FoldedOps);
+        FoldedOps.insert({OldC, NewC});
       } else {
         NewC = It->second;
       }
     }
     Ops.push_back(NewC);
   }
 
   if (auto *CE = dyn_cast<ConstantExpr>(C)) {
for (Value *Incoming : PN->incoming_values()) {
       // all operands are constants.
       if (isa<UndefValue>(Incoming))
         continue;
       // If the incoming value is not a constant, then give up.
       auto *C = dyn_cast<Constant>(Incoming);
       if (!C)
         return nullptr;
       // Fold the PHI's operands.
-      if (auto *FoldedC = ConstantFoldConstantImpl(C, DL, TLI, FoldedOps))
-        C = FoldedC;
+      C = ConstantFoldConstantImpl(C, DL, TLI, FoldedOps);
       // If the incoming value is a different constant to
       // the one we saw previously, then give up.
       if (CommonValue && C != CommonValue)
         return nullptr;
       CommonValue = C;
     }
 
     // If we reach here, all incoming values are the same constant or undef.
     return CommonValue ? CommonValue : UndefValue::get(PN->getType());
   }
 
   // Scan the operand list, checking to see if they are all constants, if so,
   // hand off to ConstantFoldInstOperandsImpl.
   if (!all_of(I->operands(), [](Use &U) { return isa<Constant>(U); }))
     return nullptr;
 
   SmallDenseMap<Constant *, Constant *> FoldedOps;
   SmallVector<Constant *, 8> Ops;
   for (const Use &OpU : I->operands()) {
     auto *Op = cast<Constant>(&OpU);
     // Fold the Instruction's operands.
-    if (auto *FoldedOp = ConstantFoldConstantImpl(Op, DL, TLI, FoldedOps))
-      Op = FoldedOp;
-
+    Op = ConstantFoldConstantImpl(Op, DL, TLI, FoldedOps);
     Ops.push_back(Op);
   }
 
   if (const auto *CI = dyn_cast<CmpInst>(I))
     return ConstantFoldCompareInstOperands(CI->getPredicate(), Ops[0], Ops[1],
                                            DL, TLI);
 
   if (const auto *LI = dyn_cast<LoadInst>(I))

llvm/lib/Analysis/InstructionSimplify.cpp

static Value *SimplifyGEPInst(Type *SrcTy, ArrayRef<Value *> Ops,
   }
 
   // Check to see if this is constant foldable.
   if (!all_of(Ops, [](Value *V) { return isa<Constant>(V); }))
     return nullptr;
 
   auto *CE = ConstantExpr::getGetElementPtr(SrcTy, cast<Constant>(Ops[0]),
                                             Ops.slice(1));
-  if (auto *CEFolded = ConstantFoldConstant(CE, Q.DL))
-    return CEFolded;
-  return CE;
+  return ConstantFoldConstant(CE, Q.DL);
 }
 
 Value *llvm::SimplifyGEPInst(Type *SrcTy, ArrayRef<Value *> Ops,
                              const SimplifyQuery &Q) {
   return ::SimplifyGEPInst(SrcTy, Ops, Q, RecursionLimit);
 }
 
 /// Given operands for an InsertValueInst, see if we can fold the result.

llvm/lib/Analysis/Lint.cpp

if (LoadInst *L = dyn_cast<LoadInst>(V)) {
     }
   }
 
   // As a last resort, try SimplifyInstruction or constant folding.
   if (Instruction *Inst = dyn_cast<Instruction>(V)) {
     if (Value *W = SimplifyInstruction(Inst, {*DL, TLI, DT, AC}))
       return findValueImpl(W, OffsetOk, Visited);
   } else if (auto *C = dyn_cast<Constant>(V)) {
-    if (Value *W = ConstantFoldConstant(C, *DL, TLI))
-      if (W && W != V)
-        return findValueImpl(W, OffsetOk, Visited);
+    Value *W = ConstantFoldConstant(C, *DL, TLI);
+    if (W != V)
   }
 
   return V;
 }
 
 //===----------------------------------------------------------------------===//
 //  Implement the public interfaces to this file...
 //===----------------------------------------------------------------------===//

llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp

if (const BlockAddress *BA = dyn_cast<BlockAddress>(CV))
     return MCSymbolRefExpr::create(GetBlockAddressSymbol(BA), Ctx);
 
   const ConstantExpr *CE = dyn_cast<ConstantExpr>(CV);
   if (!CE) {
     llvm_unreachable("Unknown constant value to lower!");
   }
 
   switch (CE->getOpcode()) {
-  default:
+  default: {
     // If the code isn't optimized, there may be outstanding folding
     // opportunities. Attempt to fold the expression using DataLayout as a
     // last resort before giving up.
-    if (Constant *C = ConstantFoldConstant(CE, getDataLayout()))
-      if (C != CE)
-        return lowerConstant(C);
+    Constant *C = ConstantFoldConstant(CE, getDataLayout());
 
     // Otherwise report the problem to the user.
-    {
-      std::string S;
-      raw_string_ostream OS(S);
-      OS << "Unsupported expression in static initializer: ";
-      CE->printAsOperand(OS, /*PrintType=*/false,
-                     !MF ? nullptr : MF->getFunction().getParent());
-      report_fatal_error(OS.str());
-    }
   case Instruction::GetElementPtr: {
     // Generate a symbolic expression for the byte address
     APInt OffsetAI(getDataLayout().getPointerTypeSizeInBits(CE->getType()), 0);
     cast<GEPOperator>(CE)->accumulateConstantOffset(getDataLayout(), OffsetAI);
 
     const MCExpr *Base = lowerConstant(CE->getOperand(0));
     if (!OffsetAI)
       return Base;
if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(CV)) {
     if (CE->getOpcode() == Instruction::BitCast)
       return emitGlobalConstantImpl(DL, CE->getOperand(0), AP);
 
     if (Size > 8) {
       // If the constant expression's size is greater than 64-bits, then we have
       // to emit the value in chunks. Try to constant fold the value and emit it
       // that way.
       Constant *New = ConstantFoldConstant(CE, DL);
-      if (New && New != CE)
+      if (New != CE)
         return emitGlobalConstantImpl(DL, New, AP);
     }
   }
 
   if (const ConstantVector *V = dyn_cast<ConstantVector>(CV))
     return emitGlobalConstantVector(DL, V, AP);
 
   // Otherwise, it must be a ConstantExpr.  Lower it to an MCExpr, then emit it

llvm/lib/Target/NVPTX/NVPTXAsmPrinter.cpp

if (ETy == Type::getInt8Ty(CPV->getContext())) {
       aggBuffer->addBytes(ptr, 2, Bytes);
     } else if (ETy == Type::getInt32Ty(CPV->getContext())) {
       if (const ConstantInt *constInt = dyn_cast<ConstantInt>(CPV)) {
         int int32 = (int)(constInt->getZExtValue());
         ConvertIntToBytes<>(ptr, int32);
         aggBuffer->addBytes(ptr, 4, Bytes);
         break;
       } else if (const auto *Cexpr = dyn_cast<ConstantExpr>(CPV)) {
-        if (const auto *constInt = dyn_cast_or_null<ConstantInt>(
+        if (const auto *constInt = dyn_cast<ConstantInt>(
                 ConstantFoldConstant(Cexpr, DL))) {
           int int32 = (int)(constInt->getZExtValue());
           ConvertIntToBytes<>(ptr, int32);
           aggBuffer->addBytes(ptr, 4, Bytes);
           break;
         }
         if (Cexpr->getOpcode() == Instruction::PtrToInt) {
           Value *v = Cexpr->getOperand(0)->stripPointerCasts();
           aggBuffer->addSymbol(v, Cexpr->getOperand(0));
           aggBuffer->addZeros(4);
           break;
         }
       }
       llvm_unreachable("unsupported integer const type");
     } else if (ETy == Type::getInt64Ty(CPV->getContext())) {
       if (const ConstantInt *constInt = dyn_cast<ConstantInt>(CPV)) {
         long long int64 = (long long)(constInt->getZExtValue());
         ConvertIntToBytes<>(ptr, int64);
         aggBuffer->addBytes(ptr, 8, Bytes);
         break;
       } else if (const ConstantExpr *Cexpr = dyn_cast<ConstantExpr>(CPV)) {
-        if (const auto *constInt = dyn_cast_or_null<ConstantInt>(
+        if (const auto *constInt = dyn_cast<ConstantInt>(
                 ConstantFoldConstant(Cexpr, DL))) {
           long long int64 = (long long)(constInt->getZExtValue());
           ConvertIntToBytes<>(ptr, int64);
           aggBuffer->addBytes(ptr, 8, Bytes);
           break;
         }
         if (Cexpr->getOpcode() == Instruction::PtrToInt) {
           Value *v = Cexpr->getOperand(0)->stripPointerCasts();
NVPTXAsmPrinter::lowerConstantForGV(const Constant *CV, bool ProcessingGeneric) {
   }
 
   const ConstantExpr *CE = dyn_cast<ConstantExpr>(CV);
   if (!CE) {
     llvm_unreachable("Unknown constant value to lower!");
   }
 
   switch (CE->getOpcode()) {
-  default:
+  default: {
     // If the code isn't optimized, there may be outstanding folding
     // opportunities. Attempt to fold the expression using DataLayout as a
     // last resort before giving up.
-    if (Constant *C = ConstantFoldConstant(CE, getDataLayout()))
-      if (C && C != CE)
-        return lowerConstantForGV(C, ProcessingGeneric);
+    Constant *C = ConstantFoldConstant(CE, getDataLayout());
+    if (C != CE)
 
     // Otherwise report the problem to the user.
-    {
-      std::string S;
-      raw_string_ostream OS(S);
-      OS << "Unsupported expression in static initializer: ";
-      CE->printAsOperand(OS, /*PrintType=*/false,
-                     !MF ? nullptr : MF->getFunction().getParent());
-      report_fatal_error(OS.str());
-    }
 
   case Instruction::AddrSpaceCast: {
     // Strip the addrspacecast and pass along the operand
     PointerType *DstTy = cast<PointerType>(CE->getType());
     if (DstTy->getAddressSpace() == 0) {
       return lowerConstantForGV(cast<const Constant>(CE->getOperand(0)), true);
     }
     std::string S;

llvm/lib/Transforms/AggressiveInstCombine/TruncInstCombine.cpp

static Type *getReducedType(Value *V, Type *Ty) {
   return Ty;
 }
 
 Value *TruncInstCombine::getReducedOperand(Value *V, Type *SclTy) {
   Type *Ty = getReducedType(V, SclTy);
   if (auto *C = dyn_cast<Constant>(V)) {
     C = ConstantExpr::getIntegerCast(C, Ty, false);
     // If we got a constantexpr back, try to simplify it with DL info.
-    if (Constant *FoldedC = ConstantFoldConstant(C, DL, &TLI))
-      C = FoldedC;
-    return C;
+    return ConstantFoldConstant(C, DL, &TLI);
   }
 
   auto *I = cast<Instruction>(V);
   Info Entry = InstInfoMap.lookup(I);
   assert(Entry.NewValue);
   return Entry.NewValue;
 }
 

llvm/lib/Transforms/IPO/GlobalOpt.cpp

for (Module::global_iterator GVI = M.global_begin(), E = M.global_end();
     // Simplify the initializer.
     if (GV->hasInitializer())
       if (auto *C = dyn_cast<Constant>(GV->getInitializer())) {
         auto &DL = M.getDataLayout();
         // TLI is not used in the case of a Constant, so use default nullptr
         // for that optional parameter, since we don't have a Function to
         // provide GetTLI anyway.
         Constant *New = ConstantFoldConstant(C, DL, /*TLI*/ nullptr);
-        if (New && New != C)
+        if (New != C)
           GV->setInitializer(New);
       }
 
     if (deleteIfDead(*GV, NotDiscardableComdats)) {
       Changed = true;
       continue;
     }
 

llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp

 
 /// Given an expression that CanEvaluateTruncated or CanEvaluateSExtd returns
 /// true for, actually insert the code to evaluate the expression.
 Value *InstCombiner::EvaluateInDifferentType(Value *V, Type *Ty,
                                              bool isSigned) {
   if (Constant *C = dyn_cast<Constant>(V)) {
     C = ConstantExpr::getIntegerCast(C, Ty, isSigned /*Sext or ZExt*/);
     // If we got a constantexpr back, try to simplify it with DL info.
-    if (Constant *FoldedC = ConstantFoldConstant(C, DL, &TLI))
-      C = FoldedC;
-    return C;
+    return ConstantFoldConstant(C, DL, &TLI);
   }
 
   // Otherwise, it must be an instruction.
   Instruction *I = cast<Instruction>(V);
   Instruction *Res = nullptr;
   unsigned Opc = I->getOpcode();
   switch (Opc) {
   case Instruction::Add:

llvm/lib/Transforms/InstCombine/InstCombineShifts.cpp

static Value *getShiftedValue(Value *V, unsigned NumBits, bool isLeftShift,
                               InstCombiner &IC, const DataLayout &DL) {
   // We can always evaluate constants shifted.
   if (Constant *C = dyn_cast<Constant>(V)) {
     if (isLeftShift)
       V = IC.Builder.CreateShl(C, NumBits);
     else
       V = IC.Builder.CreateLShr(C, NumBits);
     // If we got a constantexpr back, try to simplify it with TD info.
+    // TODO: This is dubious, IRBuilder<TargetFolder> should already do this.
     if (auto *C = dyn_cast<Constant>(V))
-      if (auto *FoldedC =
-              ConstantFoldConstant(C, DL, &IC.getTargetLibraryInfo()))
-        V = FoldedC;
+      V = ConstantFoldConstant(C, DL, &IC.getTargetLibraryInfo());
     return V;
   }
 
   Instruction *I = cast<Instruction>(V);
   IC.Worklist.push(I);
 
   switch (I->getOpcode()) {
   default: llvm_unreachable("Inconsistency with CanEvaluateShifted");

llvm/lib/Transforms/InstCombine/InstructionCombining.cpp

for (BasicBlock::iterator BBI = BB->begin(), E = BB->end(); BBI != E; ) {
       for (Use &U : Inst->operands()) {
         if (!isa<ConstantVector>(U) && !isa<ConstantExpr>(U))
           continue;
 
         auto *C = cast<Constant>(U);
         Constant *&FoldRes = FoldedConstants[C];
         if (!FoldRes)
           FoldRes = ConstantFoldConstant(C, DL, TLI);
-        if (!FoldRes)
-          FoldRes = C;
 
         if (FoldRes != C) {
           LLVM_DEBUG(dbgs() << "IC: ConstFold operand of: " << *Inst
                             << "\n    Old = " << *C
                             << "\n    New = " << *FoldRes << '\n');
           U = FoldRes;
           MadeIRChange = true;
         }

llvm/lib/Transforms/Utils/Evaluator.cpp

while (!(Val = Func(Ptr))) {
     if (!isa<StructType>(Ty))
       break;
 
     IntegerType *IdxTy = IntegerType::get(Ty->getContext(), 32);
     Constant *IdxZero = ConstantInt::get(IdxTy, 0, false);
     Constant *const IdxList[] = {IdxZero, IdxZero};
 
     Ptr = ConstantExpr::getGetElementPtr(Ty, Ptr, IdxList);
-    if (auto *FoldedPtr = ConstantFoldConstant(Ptr, DL, TLI))
-      Ptr = FoldedPtr;
+    Ptr = ConstantFoldConstant(Ptr, DL, TLI);
   }
   return Val;
 }
 
 static Constant *getInitializer(Constant *C) {
   auto *GV = dyn_cast<GlobalVariable>(C);
   return GV && GV->hasDefinitiveInitializer() ? GV->getInitializer() : nullptr;
 }
while (true) {
     LLVM_DEBUG(dbgs() << "Evaluating Instruction: " << *CurInst << "\n");
 
     if (StoreInst *SI = dyn_cast<StoreInst>(CurInst)) {
       if (!SI->isSimple()) {
         LLVM_DEBUG(dbgs() << "Store is not simple! Can not evaluate.\n");
         return false;  // no volatile/atomic accesses.
       }
       Constant *Ptr = getVal(SI->getOperand(1));
-      if (auto *FoldedPtr = ConstantFoldConstant(Ptr, DL, TLI)) {
+      Constant *FoldedPtr = ConstantFoldConstant(Ptr, DL, TLI);
+      if (Ptr != FoldedPtr) {
         LLVM_DEBUG(dbgs() << "Folding constant ptr expression: " << *Ptr);
         Ptr = FoldedPtr;
         LLVM_DEBUG(dbgs() << "; To: " << *Ptr << "\n");
       }
       if (!isSimpleEnoughPointerToCommit(Ptr)) {
         // If this is too complex for us to commit, reject it.
         LLVM_DEBUG(
             dbgs() << "Pointer is too complex for us to evaluate store.");
while (true) {
     } else if (LoadInst *LI = dyn_cast<LoadInst>(CurInst)) {
       if (!LI->isSimple()) {
         LLVM_DEBUG(
             dbgs() << "Found a Load! Not a simple load, can not evaluate.\n");
         return false;  // no volatile/atomic accesses.
       }
 
       Constant *Ptr = getVal(LI->getOperand(0));
-      if (auto *FoldedPtr = ConstantFoldConstant(Ptr, DL, TLI)) {
+      Constant *FoldedPtr = ConstantFoldConstant(Ptr, DL, TLI);
+      if (Ptr != FoldedPtr) {
         Ptr = FoldedPtr;
         LLVM_DEBUG(dbgs() << "Found a constant pointer expression, constant "
                              "folding: "
                           << *Ptr << "\n");
       }
       InstResult = ComputeLoadResult(Ptr);
       if (!InstResult) {
         LLVM_DEBUG(
if (StoreInst *SI = dyn_cast<StoreInst>(CurInst)) {
       // Did not know how to evaluate this!
       LLVM_DEBUG(
           dbgs() << "Failed to evaluate block due to unhandled instruction."
                     "\n");
       return false;
     }
 
     if (!CurInst->use_empty()) {
-      if (auto *FoldedInstResult = ConstantFoldConstant(InstResult, DL, TLI))
-        InstResult = FoldedInstResult;
-
+      InstResult = ConstantFoldConstant(InstResult, DL, TLI);
       setVal(&*CurInst, InstResult);
     }
 
     // If we just processed an invoke, we finished evaluating the block.
     if (InvokeInst *II = dyn_cast<InvokeInst>(CurInst)) {
       NextBB = II->getNormalDest();
       LLVM_DEBUG(dbgs() << "Found an invoke instruction. Finished Block.\n\n");
       return true;

llvm/lib/Transforms/Utils/VNCoercion.cpp

 
 template <class T, class HelperClass>
 static T *coerceAvailableValueToLoadTypeHelper(T *StoredVal, Type *LoadedTy,
                                                HelperClass &Helper,
                                                const DataLayout &DL) {
   assert(canCoerceMustAliasedValueToLoad(StoredVal, LoadedTy, DL) &&
          "precondition violation - materialization can't fail");
   if (auto *C = dyn_cast<Constant>(StoredVal))
-    if (auto *FoldedStoredVal = ConstantFoldConstant(C, DL))
-      StoredVal = FoldedStoredVal;
+    StoredVal = ConstantFoldConstant(C, DL);
 
   // If this is already the right type, just return it.
   Type *StoredValTy = StoredVal->getType();
 
   uint64_t StoredValSize = DL.getTypeSizeInBits(StoredValTy);
   uint64_t LoadedValSize = DL.getTypeSizeInBits(LoadedTy);
 
   // If the store and reload are the same size, we can always reuse it.
if (StoredValTy->isPtrOrPtrVectorTy() && LoadedTy->isPtrOrPtrVectorTy()) {
         StoredVal = Helper.CreateBitCast(StoredVal, TypeToCastTo);
 
       // Cast to pointer if the load needs a pointer type.
       if (LoadedTy->isPtrOrPtrVectorTy())
         StoredVal = Helper.CreateIntToPtr(StoredVal, LoadedTy);
     }
 
     if (auto *C = dyn_cast<ConstantExpr>(StoredVal))
-      if (auto *FoldedStoredVal = ConstantFoldConstant(C, DL))
-        StoredVal = FoldedStoredVal;
+      StoredVal = ConstantFoldConstant(C, DL);
 
     return StoredVal;
   }
   // If the loaded value is smaller than the available value, then we can
   // extract out a piece from it.  If the available value is too small, then we
   // can't do anything.
   assert(StoredValSize >= LoadedValSize &&
          "canCoerceMustAliasedValueToLoad fail");
if (LoadedTy != NewIntTy) {
     if (LoadedTy->isPtrOrPtrVectorTy())
       StoredVal = Helper.CreateIntToPtr(StoredVal, LoadedTy);
     else
       // Otherwise, bitcast.
       StoredVal = Helper.CreateBitCast(StoredVal, LoadedTy);
   }
 
   if (auto *C = dyn_cast<Constant>(StoredVal))
-    if (auto *FoldedStoredVal = ConstantFoldConstant(C, DL))
-      StoredVal = FoldedStoredVal;
+    StoredVal = ConstantFoldConstant(C, DL);
 
   return StoredVal;
 }
 
 /// If we saw a store of a value to memory, and
 /// then a load from a must-aliased pointer of a different type, try to coerce
 /// the stored value.  LoadedTy is the type of the load we want to replace.
 /// IRB is IRBuilder used to insert new instructions.