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Reland r216439 215441, majnemer has a real fix for PR20771.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@216586 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Nico Weber
2014-08-27 20:06:19 +00:00
parent 1a7f705fba
commit 1c768816d7
3 changed files with 142 additions and 11 deletions
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64
lib/Analysis/InstructionSimplify.cpp
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@@ -2799,29 +2799,71 @@ Value *llvm::SimplifySelectInst(Value *Cond, Value *TrueVal, Value *FalseVal,
static Value *SimplifyGEPInst(ArrayRef<Value *> Ops, const Query &Q, unsigned) {
// The type of the GEP pointer operand.
PointerType *PtrTy = cast<PointerType>(Ops[0]->getType()->getScalarType());
unsigned AS = PtrTy->getAddressSpace();
// getelementptr P -> P.
if (Ops.size() == 1)
return Ops[0];
if (isa<UndefValue>(Ops[0])) {
// Compute the (pointer) type returned by the GEP instruction.
Type *LastType = GetElementPtrInst::getIndexedType(PtrTy, Ops.slice(1));
Type *GEPTy = PointerType::get(LastType, PtrTy->getAddressSpace());
if (VectorType *VT = dyn_cast<VectorType>(Ops[0]->getType()))
GEPTy = VectorType::get(GEPTy, VT->getNumElements());
// Compute the (pointer) type returned by the GEP instruction.
Type *LastType = GetElementPtrInst::getIndexedType(PtrTy, Ops.slice(1));
Type *GEPTy = PointerType::get(LastType, AS);
if (VectorType *VT = dyn_cast<VectorType>(Ops[0]->getType()))
GEPTy = VectorType::get(GEPTy, VT->getNumElements());
if (isa<UndefValue>(Ops[0]))
return UndefValue::get(GEPTy);
}
if (Ops.size() == 2) {
// getelementptr P, 0 -> P.
if (match(Ops[1], m_Zero()))
return Ops[0];
// getelementptr P, N -> P if P points to a type of zero size.
if (Q.DL) {
Type *Ty = PtrTy->getElementType();
if (Ty->isSized() && Q.DL->getTypeAllocSize(Ty) == 0)
Type *Ty = PtrTy->getElementType();
if (Q.DL && Ty->isSized()) {
Value *P;
uint64_t C;
uint64_t TyAllocSize = Q.DL->getTypeAllocSize(Ty);
// getelementptr P, N -> P if P points to a type of zero size.
if (TyAllocSize == 0)
return Ops[0];
// The following transforms are only safe if the ptrtoint cast
// doesn't truncate the pointers.
if (Ops[1]->getType()->getScalarSizeInBits() ==
Q.DL->getPointerSizeInBits(AS)) {
auto PtrToIntOrZero = [GEPTy](Value *P) -> Value * {
if (match(P, m_Zero()))
return Constant::getNullValue(GEPTy);
Value *Temp;
if (match(P, m_PtrToInt(m_Value(Temp))))
return Temp;
return nullptr;
};
// getelementptr V, (sub P, V) -> P if P points to a type of size 1.
if (TyAllocSize == 1 &&
match(Ops[1], m_Sub(m_Value(P), m_PtrToInt(m_Specific(Ops[0])))))
if (Value *R = PtrToIntOrZero(P))
return R;
// getelementptr V, (ashr (sub P, V), C) -> Q
// if P points to a type of size 1 << C.
if (match(Ops[1],
m_AShr(m_Sub(m_Value(P), m_PtrToInt(m_Specific(Ops[0]))),
m_ConstantInt(C))) &&
TyAllocSize == 1ULL << C)
if (Value *R = PtrToIntOrZero(P))
return R;
// getelementptr V, (sdiv (sub P, V), C) -> Q
// if P points to a type of size C.
if (match(Ops[1],
m_SDiv(m_Sub(m_Value(P), m_PtrToInt(m_Specific(Ops[0]))),
m_SpecificInt(TyAllocSize))))
if (Value *R = PtrToIntOrZero(P))
return R;
}
}
}