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InstSimplify: Fold gep X, (sub 0, ptrtoint(X)) to null

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Save InstCombine some work if we can perform this fold during
InstSimplify.

llvm-svn: 216441
This commit is contained in:
David Majnemer
2014-08-26 07:08:03 +00:00
parent e81df3bbc9
commit 788d0ab8c8
2 changed files with 61 additions and 21 deletions
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53
llvm/lib/Analysis/InstructionSimplify.cpp
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@@ -2789,14 +2789,14 @@ static Value *SimplifyGEPInst(ArrayRef<Value *> Ops, const Query &Q, unsigned) {
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, AS);
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.
@@ -2816,26 +2816,37 @@ static Value *SimplifyGEPInst(ArrayRef<Value *> Ops, const Query &Q, unsigned) {
// doesn't truncate the pointers.
if (Ops[1]->getType()->getScalarSizeInBits() ==
Q.DL->getPointerSizeInBits(AS)) {
// getelementptr P, (sub Q, P) -> Q if P points to a type of size 1.
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_PtrToInt(m_Value(P)),
m_PtrToInt(m_Specific(Ops[0])))))
return P;
match(Ops[1], m_Sub(m_Value(P), m_PtrToInt(m_Specific(Ops[0])))))
if (Value *R = PtrToIntOrZero(P))
return R;
// getelementptr P, (ashr (sub Q, P), C) -> Q
// 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_PtrToInt(m_Value(P)),
m_PtrToInt(m_Specific(Ops[0]))),
m_ConstantInt(C))) &&
if (match(Ops[1],
m_AShr(m_Sub(m_Value(P), m_PtrToInt(m_Specific(Ops[0]))),
m_ConstantInt(C))) &&
TyAllocSize == 1ULL << C)
return P;
if (Value *R = PtrToIntOrZero(P))
return R;
// getelementptr P, (sdiv (sub Q, P), C) -> Q
// 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_PtrToInt(m_Value(P)),
m_PtrToInt(m_Specific(Ops[0]))),
m_SpecificInt(TyAllocSize))))
return P;
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;
}
}
}