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Take alignment into account in isSafeToLoadUnconditionally

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Reviewed By: hfinkel

Differential Revision: http://reviews.llvm.org/D10475


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@240636 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Artur Pilipenko
2015-06-25 12:18:43 +00:00
parent 01381b0e95
commit f2e7bb5d2f
2 changed files with 37 additions and 6 deletions
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26
lib/Analysis/Loads.cpp
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@ -65,6 +65,12 @@ static bool AreEquivalentAddressValues(const Value *A, const Value *B) {
bool llvm::isSafeToLoadUnconditionally(Value *V, Instruction *ScanFrom,
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);
@ -102,7 +108,7 @@ bool llvm::isSafeToLoadUnconditionally(Value *V, Instruction *ScanFrom,
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))
((ByteOffset % Align) == 0))
return true;
}
}
@ -128,20 +134,28 @@ bool llvm::isSafeToLoadUnconditionally(Value *V, Instruction *ScanFrom,
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.
if (AccessedPtr == V)
return true;
auto *AccessedTy = cast<PointerType>(AccessedPtr->getType());
if (AreEquivalentAddressValues(AccessedPtr->stripPointerCasts(), V) &&
LoadSize <= DL.getTypeStoreSize(AccessedTy->getElementType()))
LoadSize <= DL.getTypeStoreSize(AccessedTy))
return true;
}
return false;