-/// isDereferenceablePointer - Test if this value is always a pointer to
-/// allocated and suitably aligned memory for a simple load or store.
-static bool isDereferenceablePointer(const Value *V, const DataLayout *DL,
- SmallPtrSet<const Value *, 32> &Visited) {
- // Note that it is not safe to speculate into a malloc'd region because
- // malloc may return null.
-
- // These are obviously ok.
- if (isa<AllocaInst>(V)) return true;
-
- // It's not always safe to follow a bitcast, for example:
- // bitcast i8* (alloca i8) to i32*
- // would result in a 4-byte load from a 1-byte alloca. However,
- // if we're casting from a pointer from a type of larger size
- // to a type of smaller size (or the same size), and the alignment
- // is at least as large as for the resulting pointer type, then
- // we can look through the bitcast.
- if (DL)
- if (const BitCastInst* BC = dyn_cast<BitCastInst>(V)) {
- Type *STy = BC->getSrcTy()->getPointerElementType(),
- *DTy = BC->getDestTy()->getPointerElementType();
- if (STy->isSized() && DTy->isSized() &&
- (DL->getTypeStoreSize(STy) >=
- DL->getTypeStoreSize(DTy)) &&
- (DL->getABITypeAlignment(STy) >=
- DL->getABITypeAlignment(DTy)))
- return isDereferenceablePointer(BC->getOperand(0), DL, Visited);
- }
-
- // Global variables which can't collapse to null are ok.
- if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(V))
- return !GV->hasExternalWeakLinkage();
-
- // byval arguments are ok.
- if (const Argument *A = dyn_cast<Argument>(V))
- return A->hasByValAttr();
-
- // For GEPs, determine if the indexing lands within the allocated object.
- if (const GEPOperator *GEP = dyn_cast<GEPOperator>(V)) {
- // Conservatively require that the base pointer be fully dereferenceable.
- if (!Visited.insert(GEP->getOperand(0)))
- return false;
- if (!isDereferenceablePointer(GEP->getOperand(0), DL, Visited))
- return false;
- // Check the indices.
- gep_type_iterator GTI = gep_type_begin(GEP);
- for (User::const_op_iterator I = GEP->op_begin()+1,
- E = GEP->op_end(); I != E; ++I) {
- Value *Index = *I;
- Type *Ty = *GTI++;
- // Struct indices can't be out of bounds.
- if (isa<StructType>(Ty))
- continue;
- ConstantInt *CI = dyn_cast<ConstantInt>(Index);
- if (!CI)
- return false;
- // Zero is always ok.
- if (CI->isZero())
- continue;
- // Check to see that it's within the bounds of an array.
- ArrayType *ATy = dyn_cast<ArrayType>(Ty);
- if (!ATy)
- return false;
- if (CI->getValue().getActiveBits() > 64)
- return false;
- if (CI->getZExtValue() >= ATy->getNumElements())
- return false;
- }
- // Indices check out; this is dereferenceable.
- return true;
- }
-
- // If we don't know, assume the worst.
- return false;
-}
-
-/// isDereferenceablePointer - Test if this value is always a pointer to
-/// allocated and suitably aligned memory for a simple load or store.
-bool Value::isDereferenceablePointer(const DataLayout *DL) const {
- SmallPtrSet<const Value *, 32> Visited;
- return ::isDereferenceablePointer(this, DL, Visited);
-}
-
-/// DoPHITranslation - If this value is a PHI node with CurBB as its parent,
-/// return the value in the PHI node corresponding to PredBB. If not, return
-/// ourself. This is useful if you want to know the value something has in a
-/// predecessor block.