| #include "llvm/Transforms/Utils/VNCoercion.h" |
| #include "llvm/Analysis/AliasAnalysis.h" |
| #include "llvm/Analysis/ConstantFolding.h" |
| #include "llvm/Analysis/MemoryDependenceAnalysis.h" |
| #include "llvm/Analysis/ValueTracking.h" |
| #include "llvm/IR/IRBuilder.h" |
| #include "llvm/IR/IntrinsicInst.h" |
| #include "llvm/Support/Debug.h" |
| |
| #define DEBUG_TYPE "vncoerce" |
| namespace llvm { |
| namespace VNCoercion { |
| |
| /// Return true if coerceAvailableValueToLoadType will succeed. |
| bool canCoerceMustAliasedValueToLoad(Value *StoredVal, Type *LoadTy, |
| const DataLayout &DL) { |
| Type *StoredTy = StoredVal->getType(); |
| if (StoredTy == LoadTy) |
| return true; |
| |
| // If the loaded or stored value is an first class array or struct, don't try |
| // to transform them. We need to be able to bitcast to integer. |
| if (LoadTy->isStructTy() || LoadTy->isArrayTy() || StoredTy->isStructTy() || |
| StoredTy->isArrayTy()) |
| return false; |
| |
| uint64_t StoreSize = DL.getTypeSizeInBits(StoredTy); |
| |
| // The store size must be byte-aligned to support future type casts. |
| if (llvm::alignTo(StoreSize, 8) != StoreSize) |
| return false; |
| |
| // The store has to be at least as big as the load. |
| if (StoreSize < DL.getTypeSizeInBits(LoadTy)) |
| return false; |
| |
| // Don't coerce non-integral pointers to integers or vice versa. |
| if (DL.isNonIntegralPointerType(StoredVal->getType()->getScalarType()) != |
| DL.isNonIntegralPointerType(LoadTy->getScalarType())) { |
| // As a special case, allow coercion of memset used to initialize |
| // an array w/null. Despite non-integral pointers not generally having a |
| // specific bit pattern, we do assume null is zero. |
| if (auto *CI = dyn_cast<Constant>(StoredVal)) |
| return CI->isNullValue(); |
| return false; |
| } |
| |
| return true; |
| } |
| |
| 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; |
| |
| // 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 (StoredValSize == LoadedValSize) { |
| // Pointer to Pointer -> use bitcast. |
| if (StoredValTy->isPtrOrPtrVectorTy() && LoadedTy->isPtrOrPtrVectorTy()) { |
| StoredVal = Helper.CreateBitCast(StoredVal, LoadedTy); |
| } else { |
| // Convert source pointers to integers, which can be bitcast. |
| if (StoredValTy->isPtrOrPtrVectorTy()) { |
| StoredValTy = DL.getIntPtrType(StoredValTy); |
| StoredVal = Helper.CreatePtrToInt(StoredVal, StoredValTy); |
| } |
| |
| Type *TypeToCastTo = LoadedTy; |
| if (TypeToCastTo->isPtrOrPtrVectorTy()) |
| TypeToCastTo = DL.getIntPtrType(TypeToCastTo); |
| |
| if (StoredValTy != TypeToCastTo) |
| 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; |
| |
| 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"); |
| |
| // Convert source pointers to integers, which can be manipulated. |
| if (StoredValTy->isPtrOrPtrVectorTy()) { |
| StoredValTy = DL.getIntPtrType(StoredValTy); |
| StoredVal = Helper.CreatePtrToInt(StoredVal, StoredValTy); |
| } |
| |
| // Convert vectors and fp to integer, which can be manipulated. |
| if (!StoredValTy->isIntegerTy()) { |
| StoredValTy = IntegerType::get(StoredValTy->getContext(), StoredValSize); |
| StoredVal = Helper.CreateBitCast(StoredVal, StoredValTy); |
| } |
| |
| // If this is a big-endian system, we need to shift the value down to the low |
| // bits so that a truncate will work. |
| if (DL.isBigEndian()) { |
| uint64_t ShiftAmt = DL.getTypeStoreSizeInBits(StoredValTy) - |
| DL.getTypeStoreSizeInBits(LoadedTy); |
| StoredVal = Helper.CreateLShr( |
| StoredVal, ConstantInt::get(StoredVal->getType(), ShiftAmt)); |
| } |
| |
| // Truncate the integer to the right size now. |
| Type *NewIntTy = IntegerType::get(StoredValTy->getContext(), LoadedValSize); |
| StoredVal = Helper.CreateTruncOrBitCast(StoredVal, NewIntTy); |
| |
| if (LoadedTy != NewIntTy) { |
| // If the result is a pointer, inttoptr. |
| 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; |
| |
| 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. |
| /// |
| /// If we can't do it, return null. |
| Value *coerceAvailableValueToLoadType(Value *StoredVal, Type *LoadedTy, |
| IRBuilder<> &IRB, const DataLayout &DL) { |
| return coerceAvailableValueToLoadTypeHelper(StoredVal, LoadedTy, IRB, DL); |
| } |
| |
| /// This function is called when we have a memdep query of a load that ends up |
| /// being a clobbering memory write (store, memset, memcpy, memmove). This |
| /// means that the write *may* provide bits used by the load but we can't be |
| /// sure because the pointers don't must-alias. |
| /// |
| /// Check this case to see if there is anything more we can do before we give |
| /// up. This returns -1 if we have to give up, or a byte number in the stored |
| /// value of the piece that feeds the load. |
| static int analyzeLoadFromClobberingWrite(Type *LoadTy, Value *LoadPtr, |
| Value *WritePtr, |
| uint64_t WriteSizeInBits, |
| const DataLayout &DL) { |
| // If the loaded or stored value is a first class array or struct, don't try |
| // to transform them. We need to be able to bitcast to integer. |
| if (LoadTy->isStructTy() || LoadTy->isArrayTy()) |
| return -1; |
| |
| int64_t StoreOffset = 0, LoadOffset = 0; |
| Value *StoreBase = |
| GetPointerBaseWithConstantOffset(WritePtr, StoreOffset, DL); |
| Value *LoadBase = GetPointerBaseWithConstantOffset(LoadPtr, LoadOffset, DL); |
| if (StoreBase != LoadBase) |
| return -1; |
| |
| // If the load and store are to the exact same address, they should have been |
| // a must alias. AA must have gotten confused. |
| // FIXME: Study to see if/when this happens. One case is forwarding a memset |
| // to a load from the base of the memset. |
| |
| // If the load and store don't overlap at all, the store doesn't provide |
| // anything to the load. In this case, they really don't alias at all, AA |
| // must have gotten confused. |
| uint64_t LoadSize = DL.getTypeSizeInBits(LoadTy); |
| |
| if ((WriteSizeInBits & 7) | (LoadSize & 7)) |
| return -1; |
| uint64_t StoreSize = WriteSizeInBits / 8; // Convert to bytes. |
| LoadSize /= 8; |
| |
| bool isAAFailure = false; |
| if (StoreOffset < LoadOffset) |
| isAAFailure = StoreOffset + int64_t(StoreSize) <= LoadOffset; |
| else |
| isAAFailure = LoadOffset + int64_t(LoadSize) <= StoreOffset; |
| |
| if (isAAFailure) |
| return -1; |
| |
| // If the Load isn't completely contained within the stored bits, we don't |
| // have all the bits to feed it. We could do something crazy in the future |
| // (issue a smaller load then merge the bits in) but this seems unlikely to be |
| // valuable. |
| if (StoreOffset > LoadOffset || |
| StoreOffset + StoreSize < LoadOffset + LoadSize) |
| return -1; |
| |
| // Okay, we can do this transformation. Return the number of bytes into the |
| // store that the load is. |
| return LoadOffset - StoreOffset; |
| } |
| |
| /// This function is called when we have a |
| /// memdep query of a load that ends up being a clobbering store. |
| int analyzeLoadFromClobberingStore(Type *LoadTy, Value *LoadPtr, |
| StoreInst *DepSI, const DataLayout &DL) { |
| auto *StoredVal = DepSI->getValueOperand(); |
| |
| // Cannot handle reading from store of first-class aggregate yet. |
| if (StoredVal->getType()->isStructTy() || |
| StoredVal->getType()->isArrayTy()) |
| return -1; |
| |
| // Don't coerce non-integral pointers to integers or vice versa. |
| if (DL.isNonIntegralPointerType(StoredVal->getType()->getScalarType()) != |
| DL.isNonIntegralPointerType(LoadTy->getScalarType())) { |
| // Allow casts of zero values to null as a special case |
| auto *CI = dyn_cast<Constant>(StoredVal); |
| if (!CI || !CI->isNullValue()) |
| return -1; |
| } |
| |
| Value *StorePtr = DepSI->getPointerOperand(); |
| uint64_t StoreSize = |
| DL.getTypeSizeInBits(DepSI->getValueOperand()->getType()); |
| return analyzeLoadFromClobberingWrite(LoadTy, LoadPtr, StorePtr, StoreSize, |
| DL); |
| } |
| |
| /// This function is called when we have a |
| /// memdep query of a load that ends up being clobbered by another load. See if |
| /// the other load can feed into the second load. |
| int analyzeLoadFromClobberingLoad(Type *LoadTy, Value *LoadPtr, LoadInst *DepLI, |
| const DataLayout &DL) { |
| // Cannot handle reading from store of first-class aggregate yet. |
| if (DepLI->getType()->isStructTy() || DepLI->getType()->isArrayTy()) |
| return -1; |
| |
| // Don't coerce non-integral pointers to integers or vice versa. |
| if (DL.isNonIntegralPointerType(DepLI->getType()->getScalarType()) != |
| DL.isNonIntegralPointerType(LoadTy->getScalarType())) |
| return -1; |
| |
| Value *DepPtr = DepLI->getPointerOperand(); |
| uint64_t DepSize = DL.getTypeSizeInBits(DepLI->getType()); |
| int R = analyzeLoadFromClobberingWrite(LoadTy, LoadPtr, DepPtr, DepSize, DL); |
| if (R != -1) |
| return R; |
| |
| // If we have a load/load clobber an DepLI can be widened to cover this load, |
| // then we should widen it! |
| int64_t LoadOffs = 0; |
| const Value *LoadBase = |
| GetPointerBaseWithConstantOffset(LoadPtr, LoadOffs, DL); |
| unsigned LoadSize = DL.getTypeStoreSize(LoadTy); |
| |
| unsigned Size = MemoryDependenceResults::getLoadLoadClobberFullWidthSize( |
| LoadBase, LoadOffs, LoadSize, DepLI); |
| if (Size == 0) |
| return -1; |
| |
| // Check non-obvious conditions enforced by MDA which we rely on for being |
| // able to materialize this potentially available value |
| assert(DepLI->isSimple() && "Cannot widen volatile/atomic load!"); |
| assert(DepLI->getType()->isIntegerTy() && "Can't widen non-integer load"); |
| |
| return analyzeLoadFromClobberingWrite(LoadTy, LoadPtr, DepPtr, Size * 8, DL); |
| } |
| |
| int analyzeLoadFromClobberingMemInst(Type *LoadTy, Value *LoadPtr, |
| MemIntrinsic *MI, const DataLayout &DL) { |
| // If the mem operation is a non-constant size, we can't handle it. |
| ConstantInt *SizeCst = dyn_cast<ConstantInt>(MI->getLength()); |
| if (!SizeCst) |
| return -1; |
| uint64_t MemSizeInBits = SizeCst->getZExtValue() * 8; |
| |
| // If this is memset, we just need to see if the offset is valid in the size |
| // of the memset.. |
| if (MI->getIntrinsicID() == Intrinsic::memset) { |
| if (DL.isNonIntegralPointerType(LoadTy->getScalarType())) { |
| auto *CI = dyn_cast<ConstantInt>(cast<MemSetInst>(MI)->getValue()); |
| if (!CI || !CI->isZero()) |
| return -1; |
| } |
| return analyzeLoadFromClobberingWrite(LoadTy, LoadPtr, MI->getDest(), |
| MemSizeInBits, DL); |
| } |
| |
| // If we have a memcpy/memmove, the only case we can handle is if this is a |
| // copy from constant memory. In that case, we can read directly from the |
| // constant memory. |
| MemTransferInst *MTI = cast<MemTransferInst>(MI); |
| |
| Constant *Src = dyn_cast<Constant>(MTI->getSource()); |
| if (!Src) |
| return -1; |
| |
| GlobalVariable *GV = dyn_cast<GlobalVariable>(GetUnderlyingObject(Src, DL)); |
| if (!GV || !GV->isConstant() || !GV->hasDefinitiveInitializer()) |
| return -1; |
| |
| // See if the access is within the bounds of the transfer. |
| int Offset = analyzeLoadFromClobberingWrite(LoadTy, LoadPtr, MI->getDest(), |
| MemSizeInBits, DL); |
| if (Offset == -1) |
| return Offset; |
| |
| // Don't coerce non-integral pointers to integers or vice versa, and the |
| // memtransfer is implicitly a raw byte code |
| if (DL.isNonIntegralPointerType(LoadTy->getScalarType())) |
| // TODO: Can allow nullptrs from constant zeros |
| return -1; |
| |
| unsigned AS = Src->getType()->getPointerAddressSpace(); |
| // Otherwise, see if we can constant fold a load from the constant with the |
| // offset applied as appropriate. |
| Src = |
| ConstantExpr::getBitCast(Src, Type::getInt8PtrTy(Src->getContext(), AS)); |
| Constant *OffsetCst = |
| ConstantInt::get(Type::getInt64Ty(Src->getContext()), (unsigned)Offset); |
| Src = ConstantExpr::getGetElementPtr(Type::getInt8Ty(Src->getContext()), Src, |
| OffsetCst); |
| Src = ConstantExpr::getBitCast(Src, PointerType::get(LoadTy, AS)); |
| if (ConstantFoldLoadFromConstPtr(Src, LoadTy, DL)) |
| return Offset; |
| return -1; |
| } |
| |
| template <class T, class HelperClass> |
| static T *getStoreValueForLoadHelper(T *SrcVal, unsigned Offset, Type *LoadTy, |
| HelperClass &Helper, |
| const DataLayout &DL) { |
| LLVMContext &Ctx = SrcVal->getType()->getContext(); |
| |
| // If two pointers are in the same address space, they have the same size, |
| // so we don't need to do any truncation, etc. This avoids introducing |
| // ptrtoint instructions for pointers that may be non-integral. |
| if (SrcVal->getType()->isPointerTy() && LoadTy->isPointerTy() && |
| cast<PointerType>(SrcVal->getType())->getAddressSpace() == |
| cast<PointerType>(LoadTy)->getAddressSpace()) { |
| return SrcVal; |
| } |
| |
| uint64_t StoreSize = (DL.getTypeSizeInBits(SrcVal->getType()) + 7) / 8; |
| uint64_t LoadSize = (DL.getTypeSizeInBits(LoadTy) + 7) / 8; |
| // Compute which bits of the stored value are being used by the load. Convert |
| // to an integer type to start with. |
| if (SrcVal->getType()->isPtrOrPtrVectorTy()) |
| SrcVal = Helper.CreatePtrToInt(SrcVal, DL.getIntPtrType(SrcVal->getType())); |
| if (!SrcVal->getType()->isIntegerTy()) |
| SrcVal = Helper.CreateBitCast(SrcVal, IntegerType::get(Ctx, StoreSize * 8)); |
| |
| // Shift the bits to the least significant depending on endianness. |
| unsigned ShiftAmt; |
| if (DL.isLittleEndian()) |
| ShiftAmt = Offset * 8; |
| else |
| ShiftAmt = (StoreSize - LoadSize - Offset) * 8; |
| if (ShiftAmt) |
| SrcVal = Helper.CreateLShr(SrcVal, |
| ConstantInt::get(SrcVal->getType(), ShiftAmt)); |
| |
| if (LoadSize != StoreSize) |
| SrcVal = Helper.CreateTruncOrBitCast(SrcVal, |
| IntegerType::get(Ctx, LoadSize * 8)); |
| return SrcVal; |
| } |
| |
| /// This function is called when we have a memdep query of a load that ends up |
| /// being a clobbering store. This means that the store provides bits used by |
| /// the load but the pointers don't must-alias. Check this case to see if |
| /// there is anything more we can do before we give up. |
| Value *getStoreValueForLoad(Value *SrcVal, unsigned Offset, Type *LoadTy, |
| Instruction *InsertPt, const DataLayout &DL) { |
| |
| IRBuilder<> Builder(InsertPt); |
| SrcVal = getStoreValueForLoadHelper(SrcVal, Offset, LoadTy, Builder, DL); |
| return coerceAvailableValueToLoadTypeHelper(SrcVal, LoadTy, Builder, DL); |
| } |
| |
| Constant *getConstantStoreValueForLoad(Constant *SrcVal, unsigned Offset, |
| Type *LoadTy, const DataLayout &DL) { |
| ConstantFolder F; |
| SrcVal = getStoreValueForLoadHelper(SrcVal, Offset, LoadTy, F, DL); |
| return coerceAvailableValueToLoadTypeHelper(SrcVal, LoadTy, F, DL); |
| } |
| |
| /// This function is called when we have a memdep query of a load that ends up |
| /// being a clobbering load. This means that the load *may* provide bits used |
| /// by the load but we can't be sure because the pointers don't must-alias. |
| /// Check this case to see if there is anything more we can do before we give |
| /// up. |
| Value *getLoadValueForLoad(LoadInst *SrcVal, unsigned Offset, Type *LoadTy, |
| Instruction *InsertPt, const DataLayout &DL) { |
| // If Offset+LoadTy exceeds the size of SrcVal, then we must be wanting to |
| // widen SrcVal out to a larger load. |
| unsigned SrcValStoreSize = DL.getTypeStoreSize(SrcVal->getType()); |
| unsigned LoadSize = DL.getTypeStoreSize(LoadTy); |
| if (Offset + LoadSize > SrcValStoreSize) { |
| assert(SrcVal->isSimple() && "Cannot widen volatile/atomic load!"); |
| assert(SrcVal->getType()->isIntegerTy() && "Can't widen non-integer load"); |
| // If we have a load/load clobber an DepLI can be widened to cover this |
| // load, then we should widen it to the next power of 2 size big enough! |
| unsigned NewLoadSize = Offset + LoadSize; |
| if (!isPowerOf2_32(NewLoadSize)) |
| NewLoadSize = NextPowerOf2(NewLoadSize); |
| |
| Value *PtrVal = SrcVal->getPointerOperand(); |
| // Insert the new load after the old load. This ensures that subsequent |
| // memdep queries will find the new load. We can't easily remove the old |
| // load completely because it is already in the value numbering table. |
| IRBuilder<> Builder(SrcVal->getParent(), ++BasicBlock::iterator(SrcVal)); |
| Type *DestTy = IntegerType::get(LoadTy->getContext(), NewLoadSize * 8); |
| Type *DestPTy = |
| PointerType::get(DestTy, PtrVal->getType()->getPointerAddressSpace()); |
| Builder.SetCurrentDebugLocation(SrcVal->getDebugLoc()); |
| PtrVal = Builder.CreateBitCast(PtrVal, DestPTy); |
| LoadInst *NewLoad = Builder.CreateLoad(DestTy, PtrVal); |
| NewLoad->takeName(SrcVal); |
| NewLoad->setAlignment(MaybeAlign(SrcVal->getAlignment())); |
| |
| LLVM_DEBUG(dbgs() << "GVN WIDENED LOAD: " << *SrcVal << "\n"); |
| LLVM_DEBUG(dbgs() << "TO: " << *NewLoad << "\n"); |
| |
| // Replace uses of the original load with the wider load. On a big endian |
| // system, we need to shift down to get the relevant bits. |
| Value *RV = NewLoad; |
| if (DL.isBigEndian()) |
| RV = Builder.CreateLShr(RV, (NewLoadSize - SrcValStoreSize) * 8); |
| RV = Builder.CreateTrunc(RV, SrcVal->getType()); |
| SrcVal->replaceAllUsesWith(RV); |
| |
| SrcVal = NewLoad; |
| } |
| |
| return getStoreValueForLoad(SrcVal, Offset, LoadTy, InsertPt, DL); |
| } |
| |
| Constant *getConstantLoadValueForLoad(Constant *SrcVal, unsigned Offset, |
| Type *LoadTy, const DataLayout &DL) { |
| unsigned SrcValStoreSize = DL.getTypeStoreSize(SrcVal->getType()); |
| unsigned LoadSize = DL.getTypeStoreSize(LoadTy); |
| if (Offset + LoadSize > SrcValStoreSize) |
| return nullptr; |
| return getConstantStoreValueForLoad(SrcVal, Offset, LoadTy, DL); |
| } |
| |
| template <class T, class HelperClass> |
| T *getMemInstValueForLoadHelper(MemIntrinsic *SrcInst, unsigned Offset, |
| Type *LoadTy, HelperClass &Helper, |
| const DataLayout &DL) { |
| LLVMContext &Ctx = LoadTy->getContext(); |
| uint64_t LoadSize = DL.getTypeSizeInBits(LoadTy) / 8; |
| |
| // We know that this method is only called when the mem transfer fully |
| // provides the bits for the load. |
| if (MemSetInst *MSI = dyn_cast<MemSetInst>(SrcInst)) { |
| // memset(P, 'x', 1234) -> splat('x'), even if x is a variable, and |
| // independently of what the offset is. |
| T *Val = cast<T>(MSI->getValue()); |
| if (LoadSize != 1) |
| Val = |
| Helper.CreateZExtOrBitCast(Val, IntegerType::get(Ctx, LoadSize * 8)); |
| T *OneElt = Val; |
| |
| // Splat the value out to the right number of bits. |
| for (unsigned NumBytesSet = 1; NumBytesSet != LoadSize;) { |
| // If we can double the number of bytes set, do it. |
| if (NumBytesSet * 2 <= LoadSize) { |
| T *ShVal = Helper.CreateShl( |
| Val, ConstantInt::get(Val->getType(), NumBytesSet * 8)); |
| Val = Helper.CreateOr(Val, ShVal); |
| NumBytesSet <<= 1; |
| continue; |
| } |
| |
| // Otherwise insert one byte at a time. |
| T *ShVal = Helper.CreateShl(Val, ConstantInt::get(Val->getType(), 1 * 8)); |
| Val = Helper.CreateOr(OneElt, ShVal); |
| ++NumBytesSet; |
| } |
| |
| return coerceAvailableValueToLoadTypeHelper(Val, LoadTy, Helper, DL); |
| } |
| |
| // Otherwise, this is a memcpy/memmove from a constant global. |
| MemTransferInst *MTI = cast<MemTransferInst>(SrcInst); |
| Constant *Src = cast<Constant>(MTI->getSource()); |
| unsigned AS = Src->getType()->getPointerAddressSpace(); |
| |
| // Otherwise, see if we can constant fold a load from the constant with the |
| // offset applied as appropriate. |
| Src = |
| ConstantExpr::getBitCast(Src, Type::getInt8PtrTy(Src->getContext(), AS)); |
| Constant *OffsetCst = |
| ConstantInt::get(Type::getInt64Ty(Src->getContext()), (unsigned)Offset); |
| Src = ConstantExpr::getGetElementPtr(Type::getInt8Ty(Src->getContext()), Src, |
| OffsetCst); |
| Src = ConstantExpr::getBitCast(Src, PointerType::get(LoadTy, AS)); |
| return ConstantFoldLoadFromConstPtr(Src, LoadTy, DL); |
| } |
| |
| /// This function is called when we have a |
| /// memdep query of a load that ends up being a clobbering mem intrinsic. |
| Value *getMemInstValueForLoad(MemIntrinsic *SrcInst, unsigned Offset, |
| Type *LoadTy, Instruction *InsertPt, |
| const DataLayout &DL) { |
| IRBuilder<> Builder(InsertPt); |
| return getMemInstValueForLoadHelper<Value, IRBuilder<>>(SrcInst, Offset, |
| LoadTy, Builder, DL); |
| } |
| |
| Constant *getConstantMemInstValueForLoad(MemIntrinsic *SrcInst, unsigned Offset, |
| Type *LoadTy, const DataLayout &DL) { |
| // The only case analyzeLoadFromClobberingMemInst cannot be converted to a |
| // constant is when it's a memset of a non-constant. |
| if (auto *MSI = dyn_cast<MemSetInst>(SrcInst)) |
| if (!isa<Constant>(MSI->getValue())) |
| return nullptr; |
| ConstantFolder F; |
| return getMemInstValueForLoadHelper<Constant, ConstantFolder>(SrcInst, Offset, |
| LoadTy, F, DL); |
| } |
| } // namespace VNCoercion |
| } // namespace llvm |
