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add cast kind of from_exposed_addr (int-to-ptr casts) #97653

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Jun 3, 2022
Merged

add cast kind of from_exposed_addr (int-to-ptr casts) #97653

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add cast kind of from_exposed_addr (int-to-ptr casts)
RalfJung Jun 2, 2022
d5a590f
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RalfJung Jun 2, 2022
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50 changes: 37 additions & 13 deletions compiler/rustc_borrowck/src/type_check/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -2154,31 +2154,55 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
match (cast_ty_from, cast_ty_to) {
(Some(CastTy::Ptr(_) | CastTy::FnPtr), Some(CastTy::Int(_))) => (),
_ => {
span_mirbug!(self, rvalue, "Invalid cast {:?} -> {:?}", ty_from, ty)
span_mirbug!(
self,
rvalue,
"Invalid PointerExposeAddress cast {:?} -> {:?}",
ty_from,
ty
)
}
}
}

CastKind::Misc => {
CastKind::PointerFromExposedAddress => {
let ty_from = op.ty(body, tcx);
let cast_ty_from = CastTy::from_ty(ty_from);
let cast_ty_to = CastTy::from_ty(*ty);
match (cast_ty_from, cast_ty_to) {
(None, _)
| (_, None | Some(CastTy::FnPtr))
| (Some(CastTy::Float), Some(CastTy::Ptr(_)))
| (
Some(CastTy::Ptr(_) | CastTy::FnPtr),
Some(CastTy::Float | CastTy::Int(_)),
) => {
span_mirbug!(self, rvalue, "Invalid cast {:?} -> {:?}", ty_from, ty,)
(Some(CastTy::Int(_)), Some(CastTy::Ptr(_))) => (),
_ => {
span_mirbug!(
self,
rvalue,
"Invalid PointerFromExposedAddress cast {:?} -> {:?}",
ty_from,
ty
)
}
}
}

CastKind::Misc => {
let ty_from = op.ty(body, tcx);
let cast_ty_from = CastTy::from_ty(ty_from);
let cast_ty_to = CastTy::from_ty(*ty);
// Misc casts are either between floats and ints, or one ptr type to another.
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@oli-obk this looks like logic that would also be nice to have in MIR validation, but without duplicating everything...

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yea, I was actually wondering whether we shouldn't move (large) parts of mir typeck to mir validation

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basically anything that doesn't produce obligations I guess

match (cast_ty_from, cast_ty_to) {
(
Some(CastTy::Int(_)),
Some(CastTy::Int(_) | CastTy::Float | CastTy::Ptr(_)),
Some(CastTy::Int(_) | CastTy::Float),
Some(CastTy::Int(_) | CastTy::Float),
)
| (Some(CastTy::Float), Some(CastTy::Int(_) | CastTy::Float))
| (Some(CastTy::Ptr(_) | CastTy::FnPtr), Some(CastTy::Ptr(_))) => (),
_ => {
span_mirbug!(
self,
rvalue,
"Invalid Misc cast {:?} -> {:?}",
ty_from,
ty,
)
}
}
}
}
Expand Down
4 changes: 3 additions & 1 deletion compiler/rustc_codegen_cranelift/src/base.rs
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Expand Up @@ -608,7 +608,9 @@ fn codegen_stmt<'tcx>(
lval.write_cvalue(fx, operand.cast_pointer_to(to_layout));
}
Rvalue::Cast(
CastKind::Misc | CastKind::PointerExposeAddress,
CastKind::Misc
| CastKind::PointerExposeAddress
| CastKind::PointerFromExposedAddress,
ref operand,
to_ty,
) => {
Expand Down
6 changes: 5 additions & 1 deletion compiler/rustc_codegen_ssa/src/mir/rvalue.rs
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Expand Up @@ -269,7 +269,11 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
mir::CastKind::Pointer(
PointerCast::MutToConstPointer | PointerCast::ArrayToPointer,
)
| mir::CastKind::Misc => {
| mir::CastKind::Misc
// Since int2ptr can have arbitrary integer types as input (so we have to do
// sign extension and all that), it is currently best handled in the same code
// path as the other integer-to-X casts.
| mir::CastKind::PointerFromExposedAddress => {
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assert!(bx.cx().is_backend_immediate(cast));
let ll_t_out = bx.cx().immediate_backend_type(cast);
if operand.layout.abi.is_uninhabited() {
Expand Down
34 changes: 24 additions & 10 deletions compiler/rustc_const_eval/src/interpret/cast.rs
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Expand Up @@ -37,6 +37,12 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
self.write_immediate(res, dest)?;
}

PointerFromExposedAddress => {
let src = self.read_immediate(src)?;
let res = self.pointer_from_exposed_address_cast(&src, cast_ty)?;
self.write_immediate(res, dest)?;
}

Misc => {
let src = self.read_immediate(src)?;
let res = self.misc_cast(&src, cast_ty)?;
Expand Down Expand Up @@ -201,6 +207,24 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
Ok(self.cast_from_int_like(scalar, src.layout, cast_ty)?.into())
}

pub fn pointer_from_exposed_address_cast(
&mut self,
src: &ImmTy<'tcx, M::PointerTag>,
cast_ty: Ty<'tcx>,
) -> InterpResult<'tcx, Immediate<M::PointerTag>> {
assert!(src.layout.ty.is_integral());
assert_matches!(cast_ty.kind(), ty::RawPtr(_));

// First cast to usize.
let scalar = src.to_scalar()?;
let addr = self.cast_from_int_like(scalar, src.layout, self.tcx.types.usize)?;
let addr = addr.to_machine_usize(self)?;

// Then turn address into pointer.
let ptr = M::ptr_from_addr_cast(&self, addr);
Ok(Scalar::from_maybe_pointer(ptr, self).into())
}

pub fn cast_from_int_like(
&self,
scalar: Scalar<M::PointerTag>, // input value (there is no ScalarTy so we separate data+layout)
Expand All @@ -225,16 +249,6 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
Scalar::from_uint(v, size)
}

RawPtr(_) => {
assert!(src_layout.ty.is_integral());

let size = self.pointer_size();
let addr = u64::try_from(size.truncate(v)).unwrap();

let ptr = M::ptr_from_addr_cast(&self, addr);
Scalar::from_maybe_pointer(ptr, self)
}

Float(FloatTy::F32) if signed => Scalar::from_f32(Single::from_i128(v as i128).value),
Float(FloatTy::F64) if signed => Scalar::from_f64(Double::from_i128(v as i128).value),
Float(FloatTy::F32) => Scalar::from_f32(Single::from_u128(v).value),
Expand Down
18 changes: 8 additions & 10 deletions compiler/rustc_const_eval/src/transform/check_consts/check.rs
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Expand Up @@ -519,32 +519,30 @@ impl<'tcx> Visitor<'tcx> for Checker<'_, 'tcx> {
}
}

Rvalue::Cast(
CastKind::Pointer(PointerCast::MutToConstPointer | PointerCast::ArrayToPointer),
_,
_,
) => {}

Rvalue::Cast(
CastKind::Pointer(
PointerCast::UnsafeFnPointer
PointerCast::MutToConstPointer
| PointerCast::ArrayToPointer
| PointerCast::UnsafeFnPointer
| PointerCast::ClosureFnPointer(_)
| PointerCast::ReifyFnPointer,
),
_,
_,
) => {
// Nothing to do here. Function pointer casts are allowed now.
// These are all okay; they only change the type, not the data.
}

Rvalue::Cast(CastKind::Pointer(PointerCast::Unsize), _, _) => {
// Nothing to check here (`check_local_or_return_ty` ensures no trait objects occur
// in the type of any local, which also excludes casts).
// Unsizing is implemented for CTFE.
}

Rvalue::Cast(CastKind::PointerExposeAddress, _, _) => {
self.check_op(ops::RawPtrToIntCast);
}
Rvalue::Cast(CastKind::PointerFromExposedAddress, _, _) => {
// Since no pointer can ever get exposed (rejected above), this is easy to support.
}

Rvalue::Cast(CastKind::Misc, _, _) => {}

Expand Down
3 changes: 2 additions & 1 deletion compiler/rustc_const_eval/src/transform/promote_consts.rs
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Expand Up @@ -504,7 +504,8 @@ impl<'tcx> Validator<'_, 'tcx> {
// ptr-to-int casts are not possible in consts and thus not promotable
Rvalue::Cast(CastKind::PointerExposeAddress, _, _) => return Err(Unpromotable),

// int-to-ptr casts are fine, they just use the integer value at pointer type.
// all other casts including int-to-ptr casts are fine, they just use the integer value
// at pointer type.
Rvalue::Cast(_, operand, _) => {
self.validate_operand(operand)?;
}
Expand Down
8 changes: 7 additions & 1 deletion compiler/rustc_middle/src/mir/mod.rs
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Expand Up @@ -2613,12 +2613,18 @@ impl<'tcx> Rvalue<'tcx> {

#[derive(Clone, Copy, Debug, PartialEq, Eq, TyEncodable, TyDecodable, Hash, HashStable)]
pub enum CastKind {
Misc,
/// An exposing pointer to address cast. A cast between a pointer and an integer type, or
/// between a function pointer and an integer type.
/// See the docs on `expose_addr` for more details.
PointerExposeAddress,
/// An address-to-pointer cast that picks up an exposed provenance.
/// See the docs on `from_exposed_addr` for more details.
PointerFromExposedAddress,
/// All sorts of pointer-to-pointer casts. Note that reference-to-raw-ptr casts are
/// translated into `&raw mut/const *r`, i.e., they are not actually casts.
Pointer(PointerCast),
/// Remaining unclassified casts.
Misc,
}

#[derive(Clone, Debug, PartialEq, Eq, TyEncodable, TyDecodable, Hash, HashStable)]
Expand Down
3 changes: 3 additions & 0 deletions compiler/rustc_mir_build/src/build/expr/as_rvalue.rs
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Expand Up @@ -196,6 +196,9 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
(Some(CastTy::Ptr(_) | CastTy::FnPtr), Some(CastTy::Int(_))) => {
CastKind::PointerExposeAddress
}
(Some(CastTy::Int(_)), Some(CastTy::Ptr(_))) => {
CastKind::PointerFromExposedAddress
}
(_, _) => CastKind::Misc,
};
let source = unpack!(
Expand Down
2 changes: 1 addition & 1 deletion src/test/mir-opt/const_prop/reify_fn_ptr.main.ConstProp.diff
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Expand Up @@ -19,7 +19,7 @@
// + literal: Const { ty: fn() {main}, val: Value(Scalar(<ZST>)) }
_2 = move _3 as usize (PointerExposeAddress); // scope 0 at $DIR/reify_fn_ptr.rs:4:13: 4:26
StorageDead(_3); // scope 0 at $DIR/reify_fn_ptr.rs:4:25: 4:26
_1 = move _2 as *const fn() (Misc); // scope 0 at $DIR/reify_fn_ptr.rs:4:13: 4:41
_1 = move _2 as *const fn() (PointerFromExposedAddress); // scope 0 at $DIR/reify_fn_ptr.rs:4:13: 4:41
StorageDead(_2); // scope 0 at $DIR/reify_fn_ptr.rs:4:40: 4:41
StorageDead(_1); // scope 0 at $DIR/reify_fn_ptr.rs:4:41: 4:42
nop; // scope 0 at $DIR/reify_fn_ptr.rs:3:11: 5:2
Expand Down
7 changes: 6 additions & 1 deletion src/tools/clippy/clippy_utils/src/qualify_min_const_fn.rs
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Expand Up @@ -131,7 +131,12 @@ fn check_rvalue<'tcx>(
Rvalue::Cast(CastKind::Misc, operand, _) => {
check_operand(tcx, operand, span, body)
},
Rvalue::Cast(CastKind::Pointer(PointerCast::MutToConstPointer | PointerCast::ArrayToPointer), operand, _) => {
Rvalue::Cast(
CastKind::PointerFromExposedAddress
| CastKind::Pointer(PointerCast::MutToConstPointer | PointerCast::ArrayToPointer),
operand,
_
) => {
check_operand(tcx, operand, span, body)
},
Rvalue::Cast(
Expand Down