mirror of
https://github.com/RPCS3/llvm-mirror.git
synced 2024-11-23 03:02:36 +01:00
[InstSimplify] Don't fold gep p, -p to null
This is a partial fix for https://bugs.llvm.org/show_bug.cgi?id=44403. Folding gep p, q-p to q is only legal if p and q have the same provenance. This fold should probably be guarded by something like getUnderlyingObject(p) == getUnderlyingObject(q). This patch is a partial fix that removes the special handling for gep p, 0-p, which will fold to a null pointer, which would certainly not pass an underlying object check (unless p is also null, in which case this would fold trivially anyway). Folding to a null pointer is particularly problematic due to the special handling it receives in many places, making end-to-end miscompiles more likely. Differential Revision: https://reviews.llvm.org/D93820
This commit is contained in:
Nikita Popov
parent
60e7732238
commit
2f31020aa4
@ -4270,9 +4270,7 @@ static Value *SimplifyGEPInst(Type *SrcTy, ArrayRef<Value *> Ops,
|
||||
// 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);
|
||||
auto PtrToInt = [GEPTy](Value *P) -> Value * {
|
||||
Value *Temp;
|
||||
if (match(P, m_PtrToInt(m_Value(Temp))))
|
||||
if (Temp->getType() == GEPTy)
|
||||
@ -4280,10 +4278,14 @@ static Value *SimplifyGEPInst(Type *SrcTy, ArrayRef<Value *> Ops,
|
||||
return nullptr;
|
||||
};
|
||||
|
||||
// FIXME: The following transforms are only legal if P and V have the
|
||||
// same provenance (PR44403). Check whether getUnderlyingObject() is
|
||||
// the same?
|
||||
|
||||
// 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))
|
||||
if (Value *R = PtrToInt(P))
|
||||
return R;
|
||||
|
||||
// getelementptr V, (ashr (sub P, V), C) -> Q
|
||||
@ -4292,7 +4294,7 @@ static Value *SimplifyGEPInst(Type *SrcTy, ArrayRef<Value *> Ops,
|
||||
m_AShr(m_Sub(m_Value(P), m_PtrToInt(m_Specific(Ops[0]))),
|
||||
m_ConstantInt(C))) &&
|
||||
TyAllocSize == 1ULL << C)
|
||||
if (Value *R = PtrToIntOrZero(P))
|
||||
if (Value *R = PtrToInt(P))
|
||||
return R;
|
||||
|
||||
// getelementptr V, (sdiv (sub P, V), C) -> Q
|
||||
@ -4300,7 +4302,7 @@ static Value *SimplifyGEPInst(Type *SrcTy, ArrayRef<Value *> Ops,
|
||||
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))
|
||||
if (Value *R = PtrToInt(P))
|
||||
return R;
|
||||
}
|
||||
}
|
||||
@ -4317,15 +4319,21 @@ static Value *SimplifyGEPInst(Type *SrcTy, ArrayRef<Value *> Ops,
|
||||
Ops[0]->stripAndAccumulateInBoundsConstantOffsets(Q.DL,
|
||||
BasePtrOffset);
|
||||
|
||||
// Avoid creating inttoptr of zero here: While LLVMs treatment of
|
||||
// inttoptr is generally conservative, this particular case is folded to
|
||||
// a null pointer, which will have incorrect provenance.
|
||||
|
||||
// gep (gep V, C), (sub 0, V) -> C
|
||||
if (match(Ops.back(),
|
||||
m_Sub(m_Zero(), m_PtrToInt(m_Specific(StrippedBasePtr))))) {
|
||||
m_Sub(m_Zero(), m_PtrToInt(m_Specific(StrippedBasePtr)))) &&
|
||||
!BasePtrOffset.isNullValue()) {
|
||||
auto *CI = ConstantInt::get(GEPTy->getContext(), BasePtrOffset);
|
||||
return ConstantExpr::getIntToPtr(CI, GEPTy);
|
||||
}
|
||||
// gep (gep V, C), (xor V, -1) -> C-1
|
||||
if (match(Ops.back(),
|
||||
m_Xor(m_PtrToInt(m_Specific(StrippedBasePtr)), m_AllOnes()))) {
|
||||
m_Xor(m_PtrToInt(m_Specific(StrippedBasePtr)), m_AllOnes())) &&
|
||||
!BasePtrOffset.isOneValue()) {
|
||||
auto *CI = ConstantInt::get(GEPTy->getContext(), BasePtrOffset - 1);
|
||||
return ConstantExpr::getIntToPtr(CI, GEPTy);
|
||||
}
|
||||
|
||||
@ -40,9 +40,16 @@ define i64* @test3(i64* %b, i64* %e) {
|
||||
ret i64* %gep
|
||||
}
|
||||
|
||||
; The following tests should not be folded to null, because this would
|
||||
; lose provenance of the base pointer %b.
|
||||
|
||||
define %struct.A* @test4(%struct.A* %b) {
|
||||
; CHECK-LABEL: @test4(
|
||||
; CHECK-NEXT: ret %struct.A* null
|
||||
; CHECK-NEXT: [[B_PTR:%.*]] = ptrtoint %struct.A* [[B:%.*]] to i64
|
||||
; CHECK-NEXT: [[SUB:%.*]] = sub i64 0, [[B_PTR]]
|
||||
; CHECK-NEXT: [[SDIV:%.*]] = sdiv exact i64 [[SUB]], 7
|
||||
; CHECK-NEXT: [[GEP:%.*]] = getelementptr [[STRUCT_A:%.*]], %struct.A* [[B]], i64 [[SDIV]]
|
||||
; CHECK-NEXT: ret %struct.A* [[GEP]]
|
||||
;
|
||||
%b_ptr = ptrtoint %struct.A* %b to i64
|
||||
%sub = sub i64 0, %b_ptr
|
||||
@ -53,7 +60,11 @@ define %struct.A* @test4(%struct.A* %b) {
|
||||
|
||||
define %struct.A* @test4_inbounds(%struct.A* %b) {
|
||||
; CHECK-LABEL: @test4_inbounds(
|
||||
; CHECK-NEXT: ret %struct.A* null
|
||||
; CHECK-NEXT: [[B_PTR:%.*]] = ptrtoint %struct.A* [[B:%.*]] to i64
|
||||
; CHECK-NEXT: [[SUB:%.*]] = sub i64 0, [[B_PTR]]
|
||||
; CHECK-NEXT: [[SDIV:%.*]] = sdiv exact i64 [[SUB]], 7
|
||||
; CHECK-NEXT: [[GEP:%.*]] = getelementptr inbounds [[STRUCT_A:%.*]], %struct.A* [[B]], i64 [[SDIV]]
|
||||
; CHECK-NEXT: ret %struct.A* [[GEP]]
|
||||
;
|
||||
%b_ptr = ptrtoint %struct.A* %b to i64
|
||||
%sub = sub i64 0, %b_ptr
|
||||
@ -64,7 +75,10 @@ define %struct.A* @test4_inbounds(%struct.A* %b) {
|
||||
|
||||
define i8* @test5(i8* %b) {
|
||||
; CHECK-LABEL: @test5(
|
||||
; CHECK-NEXT: ret i8* null
|
||||
; CHECK-NEXT: [[B_PTR:%.*]] = ptrtoint i8* [[B:%.*]] to i64
|
||||
; CHECK-NEXT: [[SUB:%.*]] = sub i64 0, [[B_PTR]]
|
||||
; CHECK-NEXT: [[GEP:%.*]] = getelementptr i8, i8* [[B]], i64 [[SUB]]
|
||||
; CHECK-NEXT: ret i8* [[GEP]]
|
||||
;
|
||||
%b_ptr = ptrtoint i8* %b to i64
|
||||
%sub = sub i64 0, %b_ptr
|
||||
@ -74,7 +88,10 @@ define i8* @test5(i8* %b) {
|
||||
|
||||
define i8* @test5_inbounds(i8* %b) {
|
||||
; CHECK-LABEL: @test5_inbounds(
|
||||
; CHECK-NEXT: ret i8* null
|
||||
; CHECK-NEXT: [[B_PTR:%.*]] = ptrtoint i8* [[B:%.*]] to i64
|
||||
; CHECK-NEXT: [[SUB:%.*]] = sub i64 0, [[B_PTR]]
|
||||
; CHECK-NEXT: [[GEP:%.*]] = getelementptr inbounds i8, i8* [[B]], i64 [[SUB]]
|
||||
; CHECK-NEXT: ret i8* [[GEP]]
|
||||
;
|
||||
%b_ptr = ptrtoint i8* %b to i64
|
||||
%sub = sub i64 0, %b_ptr
|
||||
@ -84,7 +101,11 @@ define i8* @test5_inbounds(i8* %b) {
|
||||
|
||||
define i64* @test6(i64* %b) {
|
||||
; CHECK-LABEL: @test6(
|
||||
; CHECK-NEXT: ret i64* null
|
||||
; CHECK-NEXT: [[B_PTR:%.*]] = ptrtoint i64* [[B:%.*]] to i64
|
||||
; CHECK-NEXT: [[SUB:%.*]] = sub i64 0, [[B_PTR]]
|
||||
; CHECK-NEXT: [[ASHR:%.*]] = ashr exact i64 [[SUB]], 3
|
||||
; CHECK-NEXT: [[GEP:%.*]] = getelementptr i64, i64* [[B]], i64 [[ASHR]]
|
||||
; CHECK-NEXT: ret i64* [[GEP]]
|
||||
;
|
||||
%b_ptr = ptrtoint i64* %b to i64
|
||||
%sub = sub i64 0, %b_ptr
|
||||
@ -95,7 +116,11 @@ define i64* @test6(i64* %b) {
|
||||
|
||||
define i64* @test6_inbounds(i64* %b) {
|
||||
; CHECK-LABEL: @test6_inbounds(
|
||||
; CHECK-NEXT: ret i64* null
|
||||
; CHECK-NEXT: [[B_PTR:%.*]] = ptrtoint i64* [[B:%.*]] to i64
|
||||
; CHECK-NEXT: [[SUB:%.*]] = sub i64 0, [[B_PTR]]
|
||||
; CHECK-NEXT: [[ASHR:%.*]] = ashr exact i64 [[SUB]], 3
|
||||
; CHECK-NEXT: [[GEP:%.*]] = getelementptr inbounds i64, i64* [[B]], i64 [[ASHR]]
|
||||
; CHECK-NEXT: ret i64* [[GEP]]
|
||||
;
|
||||
%b_ptr = ptrtoint i64* %b to i64
|
||||
%sub = sub i64 0, %b_ptr
|
||||
|
||||
Loading…
Reference in New Issue
Block a user