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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.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@216441 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
David Majnemer 2014-08-26 07:08:03 +00:00
parent 594e4a1dd3
commit 8058ffeb18
2 changed files with 61 additions and 21 deletions
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53
lib/Analysis/InstructionSimplify.cpp
View File

@ -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;
}
}
}

29
test/Transforms/InstSimplify/gep.ll
View File

@ -35,3 +35,32 @@ define i64* @test3(i64* %b, i64* %e) {
; CHECK-LABEL: @test3
; CHECK-NEXT: ret i64* %e
}
define %struct.A* @test4(%struct.A* %b) {
%b_ptr = ptrtoint %struct.A* %b to i64
%sub = sub i64 0, %b_ptr
%sdiv = sdiv exact i64 %sub, 7
%gep = getelementptr inbounds %struct.A* %b, i64 %sdiv
ret %struct.A* %gep
; CHECK-LABEL: @test4
; CHECK-NEXT: ret %struct.A* null
}
define i8* @test5(i8* %b) {
%b_ptr = ptrtoint i8* %b to i64
%sub = sub i64 0, %b_ptr
%gep = getelementptr inbounds i8* %b, i64 %sub
ret i8* %gep
; CHECK-LABEL: @test5
; CHECK-NEXT: ret i8* null
}
define i64* @test6(i64* %b) {
%b_ptr = ptrtoint i64* %b to i64
%sub = sub i64 0, %b_ptr
%ashr = ashr exact i64 %sub, 3
%gep = getelementptr inbounds i64* %b, i64 %ashr
ret i64* %gep
; CHECK-LABEL: @test6
; CHECK-NEXT: ret i64* null
}