vendor/llvm/llvm-trunk-r300422

1 files changed, 482 insertions, 0 deletions

diff --git a/lib/Transforms/Utils/VNCoercion.cpp b/lib/Transforms/Utils/VNCoercion.cpp
new file mode 100644
index 000000000000..4aeea02b1b1b
--- /dev/null
+++ b/lib/Transforms/Utils/VNCoercion.cpp
@@ -0,0 +1,482 @@
+#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) {
+  // 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() ||
+      StoredVal->getType()->isStructTy() || StoredVal->getType()->isArrayTy())
+    return false;
+
+  // The store has to be at least as big as the load.
+  if (DL.getTypeSizeInBits(StoredVal->getType()) < DL.getTypeSizeInBits(LoadTy))
+    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->getScalarType()->isPointerTy() &&
+        LoadedTy->getScalarType()->isPointerTy()) {
+      StoredVal = Helper.CreateBitCast(StoredVal, LoadedTy);
+    } else {
+      // Convert source pointers to integers, which can be bitcast.
+      if (StoredValTy->getScalarType()->isPointerTy()) {
+        StoredValTy = DL.getIntPtrType(StoredValTy);
+        StoredVal = Helper.CreatePtrToInt(StoredVal, StoredValTy);
+      }
+
+      Type *TypeToCastTo = LoadedTy;
+      if (TypeToCastTo->getScalarType()->isPointerTy())
+        TypeToCastTo = DL.getIntPtrType(TypeToCastTo);
+
+      if (StoredValTy != TypeToCastTo)
+        StoredVal = Helper.CreateBitCast(StoredVal, TypeToCastTo);
+
+      // Cast to pointer if the load needs a pointer type.
+      if (LoadedTy->getScalarType()->isPointerTy())
+        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->getScalarType()->isPointerTy()) {
+    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->getScalarType()->isPointerTy())
+      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) {
+  // Cannot handle reading from store of first-class aggregate yet.
+  if (DepSI->getValueOperand()->getType()->isStructTy() ||
+      DepSI->getValueOperand()->getType()->isArrayTy())
+    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;
+
+  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)
+    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())
+    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;
+
+  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();
+
+  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()->getScalarType()->isPointerTy())
+    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 *DestPTy = IntegerType::get(LoadTy->getContext(), NewLoadSize * 8);
+    DestPTy =
+        PointerType::get(DestPTy, PtrVal->getType()->getPointerAddressSpace());
+    Builder.SetCurrentDebugLocation(SrcVal->getDebugLoc());
+    PtrVal = Builder.CreateBitCast(PtrVal, DestPTy);
+    LoadInst *NewLoad = Builder.CreateLoad(PtrVal);
+    NewLoad->takeName(SrcVal);
+    NewLoad->setAlignment(SrcVal->getAlignment());
+
+    DEBUG(dbgs() << "GVN WIDENED LOAD: " << *SrcVal << "\n");
+    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