/// This uses the pointee type to determine how many bytes need to be safe to
/// load from the pointer.
bool llvm::isSafeToLoadUnconditionally(Value *V, Instruction *ScanFrom,
- unsigned Align, const DataLayout *DL) {
+ unsigned Align) {
+ const DataLayout &DL = ScanFrom->getModule()->getDataLayout();
+
+ // Zero alignment means that the load has the ABI alignment for the target
+ if (Align == 0)
+ Align = DL.getABITypeAlignment(V->getType()->getPointerElementType());
+ assert(isPowerOf2_32(Align));
+
int64_t ByteOffset = 0;
Value *Base = V;
Base = GetPointerBaseWithConstantOffset(V, ByteOffset, DL);
}
PointerType *AddrTy = cast<PointerType>(V->getType());
- uint64_t LoadSize = DL ? DL->getTypeStoreSize(AddrTy->getElementType()) : 0;
+ uint64_t LoadSize = DL.getTypeStoreSize(AddrTy->getElementType());
// If we found a base allocated type from either an alloca or global variable,
// try to see if we are definitively within the allocated region. We need to
// know the size of the base type and the loaded type to do anything in this
- // case, so only try this when we have the DataLayout available.
- if (BaseType && BaseType->isSized() && DL) {
+ // case.
+ if (BaseType && BaseType->isSized()) {
if (BaseAlign == 0)
- BaseAlign = DL->getPrefTypeAlignment(BaseType);
+ BaseAlign = DL.getPrefTypeAlignment(BaseType);
if (Align <= BaseAlign) {
// Check if the load is within the bounds of the underlying object.
- if (ByteOffset + LoadSize <= DL->getTypeAllocSize(BaseType) &&
- (Align == 0 || (ByteOffset % Align) == 0))
+ if (ByteOffset + LoadSize <= DL.getTypeAllocSize(BaseType) &&
+ ((ByteOffset % Align) == 0))
return true;
}
}
// from/to. If so, the previous load or store would have already trapped,
// so there is no harm doing an extra load (also, CSE will later eliminate
// the load entirely).
- BasicBlock::iterator BBI = ScanFrom, E = ScanFrom->getParent()->begin();
+ BasicBlock::iterator BBI = ScanFrom->getIterator(),
+ E = ScanFrom->getParent()->begin();
// We can at least always strip pointer casts even though we can't use the
// base here.
return false;
Value *AccessedPtr;
- if (LoadInst *LI = dyn_cast<LoadInst>(BBI))
+ unsigned AccessedAlign;
+ if (LoadInst *LI = dyn_cast<LoadInst>(BBI)) {
AccessedPtr = LI->getPointerOperand();
- else if (StoreInst *SI = dyn_cast<StoreInst>(BBI))
+ AccessedAlign = LI->getAlignment();
+ } else if (StoreInst *SI = dyn_cast<StoreInst>(BBI)) {
AccessedPtr = SI->getPointerOperand();
- else
+ AccessedAlign = SI->getAlignment();
+ } else
+ continue;
+
+ Type *AccessedTy = AccessedPtr->getType()->getPointerElementType();
+ if (AccessedAlign == 0)
+ AccessedAlign = DL.getABITypeAlignment(AccessedTy);
+ if (AccessedAlign < Align)
continue;
- // Handle trivial cases even w/o DataLayout or other work.
+ // Handle trivial cases.
if (AccessedPtr == V)
return true;
- if (!DL)
- continue;
-
- auto *AccessedTy = cast<PointerType>(AccessedPtr->getType());
if (AreEquivalentAddressValues(AccessedPtr->stripPointerCasts(), V) &&
- LoadSize <= DL->getTypeStoreSize(AccessedTy->getElementType()))
+ LoadSize <= DL.getTypeStoreSize(AccessedTy))
return true;
}
return false;
}
+/// DefMaxInstsToScan - the default number of maximum instructions
+/// to scan in the block, used by FindAvailableLoadedValue().
+/// FindAvailableLoadedValue() was introduced in r60148, to improve jump
+/// threading in part by eliminating partially redundant loads.
+/// At that point, the value of MaxInstsToScan was already set to '6'
+/// without documented explanation.
+cl::opt<unsigned>
+llvm::DefMaxInstsToScan("available-load-scan-limit", cl::init(6), cl::Hidden,
+ cl::desc("Use this to specify the default maximum number of instructions "
+ "to scan backward from a given instruction, when searching for "
+ "available loaded value"));
+
/// \brief Scan the ScanBB block backwards to see if we have the value at the
/// memory address *Ptr locally available within a small number of instructions.
///
Type *AccessTy = cast<PointerType>(Ptr->getType())->getElementType();
- // Try to get the DataLayout for this module. This may be null, in which case
- // the optimizations will be limited.
const DataLayout &DL = ScanBB->getModule()->getDataLayout();
// Try to get the store size for the type.
while (ScanFrom != ScanBB->begin()) {
// We must ignore debug info directives when counting (otherwise they
// would affect codegen).
- Instruction *Inst = --ScanFrom;
+ Instruction *Inst = &*--ScanFrom;
if (isa<DbgInfoIntrinsic>(Inst))
continue;
if (LoadInst *LI = dyn_cast<LoadInst>(Inst))
if (AreEquivalentAddressValues(
LI->getPointerOperand()->stripPointerCasts(), StrippedPtr) &&
- CastInst::isBitOrNoopPointerCastable(LI->getType(), AccessTy, &DL)) {
+ CastInst::isBitOrNoopPointerCastable(LI->getType(), AccessTy, DL)) {
if (AATags)
LI->getAAMetadata(*AATags);
return LI;
// those cases are unlikely.)
if (AreEquivalentAddressValues(StorePtr, StrippedPtr) &&
CastInst::isBitOrNoopPointerCastable(SI->getValueOperand()->getType(),
- AccessTy, &DL)) {
+ AccessTy, DL)) {
if (AATags)
SI->getAAMetadata(*AATags);
return SI->getOperand(0);
// If we have alias analysis and it says the store won't modify the loaded
// value, ignore the store.
- if (AA &&
- (AA->getModRefInfo(SI, StrippedPtr, AccessSize) &
- AliasAnalysis::Mod) == 0)
+ if (AA && (AA->getModRefInfo(SI, StrippedPtr, AccessSize) & MRI_Mod) == 0)
continue;
// Otherwise the store that may or may not alias the pointer, bail out.
// If alias analysis claims that it really won't modify the load,
// ignore it.
if (AA &&
- (AA->getModRefInfo(Inst, StrippedPtr, AccessSize) &
- AliasAnalysis::Mod) == 0)
+ (AA->getModRefInfo(Inst, StrippedPtr, AccessSize) & MRI_Mod) == 0)
continue;
// May modify the pointer, bail out.
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