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interpret/visitor: support visiting with a PlaceTy

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This commit is contained in:
Ralf Jung
2022-07-14 20:32:45 -04:00
parent 6c6cccdd9b
commit c4cb043f06
5 changed files with 268 additions and 48 deletions
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272
compiler/rustc_const_eval/src/interpret/visitor.rs
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@@ -8,23 +8,33 @@ use rustc_target::abi::{FieldsShape, VariantIdx, Variants};
use std::num::NonZeroUsize;
use super::{InterpCx, MPlaceTy, Machine, OpTy};
use super::{InterpCx, MPlaceTy, Machine, OpTy, PlaceTy};
// A thing that we can project into, and that has a layout.
// This wouldn't have to depend on `Machine` but with the current type inference,
// that's just more convenient to work with (avoids repeating all the `Machine` bounds).
/// A thing that we can project into, and that has a layout.
/// This wouldn't have to depend on `Machine` but with the current type inference,
/// that's just more convenient to work with (avoids repeating all the `Machine` bounds).
pub trait Value<'mir, 'tcx, M: Machine<'mir, 'tcx>>: Copy {
/// Gets this value's layout.
fn layout(&self) -> TyAndLayout<'tcx>;
/// Makes this into an `OpTy`.
fn to_op(&self, ecx: &InterpCx<'mir, 'tcx, M>)
-> InterpResult<'tcx, OpTy<'tcx, M::PointerTag>>;
/// Makes this into an `OpTy`, in a cheap way that is good for reading.
fn to_op_for_read(
&self,
ecx: &InterpCx<'mir, 'tcx, M>,
) -> InterpResult<'tcx, OpTy<'tcx, M::PointerTag>>;
/// Makes this into an `OpTy`, in a potentially more expensive way that is good for projections.
fn to_op_for_proj(
&self,
ecx: &InterpCx<'mir, 'tcx, M>,
) -> InterpResult<'tcx, OpTy<'tcx, M::PointerTag>> {
self.to_op_for_read(ecx)
}
/// Creates this from an `OpTy`.
///
/// If `to_op` only ever produces `Indirect` operands, then this one is definitely `Indirect`.
fn from_op(mplace: OpTy<'tcx, M::PointerTag>) -> Self;
/// If `to_op_for_proj` only ever produces `Indirect` operands, then this one is definitely `Indirect`.
fn from_op(op: &OpTy<'tcx, M::PointerTag>) -> Self;
/// Projects to the given enum variant.
fn project_downcast(
@@ -41,8 +51,50 @@ pub trait Value<'mir, 'tcx, M: Machine<'mir, 'tcx>>: Copy {
) -> InterpResult<'tcx, Self>;
}
// Operands and memory-places are both values.
// Places in general are not due to `place_field` having to do `force_allocation`.
/// A thing that we can project into given *mutable* access to `ecx`, and that has a layout.
/// This wouldn't have to depend on `Machine` but with the current type inference,
/// that's just more convenient to work with (avoids repeating all the `Machine` bounds).
pub trait ValueMut<'mir, 'tcx, M: Machine<'mir, 'tcx>>: Copy {
/// Gets this value's layout.
fn layout(&self) -> TyAndLayout<'tcx>;
/// Makes this into an `OpTy`, in a cheap way that is good for reading.
fn to_op_for_read(
&self,
ecx: &InterpCx<'mir, 'tcx, M>,
) -> InterpResult<'tcx, OpTy<'tcx, M::PointerTag>>;
/// Makes this into an `OpTy`, in a potentially more expensive way that is good for projections.
fn to_op_for_proj(
&self,
ecx: &mut InterpCx<'mir, 'tcx, M>,
) -> InterpResult<'tcx, OpTy<'tcx, M::PointerTag>>;
/// Creates this from an `OpTy`.
///
/// If `to_op_for_proj` only ever produces `Indirect` operands, then this one is definitely `Indirect`.
fn from_op(op: &OpTy<'tcx, M::PointerTag>) -> Self;
/// Projects to the given enum variant.
fn project_downcast(
&self,
ecx: &mut InterpCx<'mir, 'tcx, M>,
variant: VariantIdx,
) -> InterpResult<'tcx, Self>;
/// Projects to the n-th field.
fn project_field(
&self,
ecx: &mut InterpCx<'mir, 'tcx, M>,
field: usize,
) -> InterpResult<'tcx, Self>;
}
// We cannot have a general impl which shows that Value implies ValueMut. (When we do, it says we
// cannot `impl ValueMut for PlaceTy` because some downstream crate could `impl Value for PlaceTy`.)
// So we have some copy-paste here. (We could have a macro but since we only have 2 types with this
// double-impl, that would barely make the code shorter, if at all.)
impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> Value<'mir, 'tcx, M> for OpTy<'tcx, M::PointerTag> {
#[inline(always)]
fn layout(&self) -> TyAndLayout<'tcx> {
@@ -50,7 +102,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> Value<'mir, 'tcx, M> for OpTy<'tc
}
#[inline(always)]
fn to_op(
fn to_op_for_read(
&self,
_ecx: &InterpCx<'mir, 'tcx, M>,
) -> InterpResult<'tcx, OpTy<'tcx, M::PointerTag>> {
@@ -58,8 +110,8 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> Value<'mir, 'tcx, M> for OpTy<'tc
}
#[inline(always)]
fn from_op(op: OpTy<'tcx, M::PointerTag>) -> Self {
op
fn from_op(op: &OpTy<'tcx, M::PointerTag>) -> Self {
*op
}
#[inline(always)]
@@ -81,6 +133,54 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> Value<'mir, 'tcx, M> for OpTy<'tc
}
}
impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> ValueMut<'mir, 'tcx, M>
for OpTy<'tcx, M::PointerTag>
{
#[inline(always)]
fn layout(&self) -> TyAndLayout<'tcx> {
self.layout
}
#[inline(always)]
fn to_op_for_read(
&self,
_ecx: &InterpCx<'mir, 'tcx, M>,
) -> InterpResult<'tcx, OpTy<'tcx, M::PointerTag>> {
Ok(*self)
}
#[inline(always)]
fn to_op_for_proj(
&self,
_ecx: &mut InterpCx<'mir, 'tcx, M>,
) -> InterpResult<'tcx, OpTy<'tcx, M::PointerTag>> {
Ok(*self)
}
#[inline(always)]
fn from_op(op: &OpTy<'tcx, M::PointerTag>) -> Self {
*op
}
#[inline(always)]
fn project_downcast(
&self,
ecx: &mut InterpCx<'mir, 'tcx, M>,
variant: VariantIdx,
) -> InterpResult<'tcx, Self> {
ecx.operand_downcast(self, variant)
}
#[inline(always)]
fn project_field(
&self,
ecx: &mut InterpCx<'mir, 'tcx, M>,
field: usize,
) -> InterpResult<'tcx, Self> {
ecx.operand_field(self, field)
}
}
impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> Value<'mir, 'tcx, M>
for MPlaceTy<'tcx, M::PointerTag>
{
@@ -90,7 +190,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> Value<'mir, 'tcx, M>
}
#[inline(always)]
fn to_op(
fn to_op_for_read(
&self,
_ecx: &InterpCx<'mir, 'tcx, M>,
) -> InterpResult<'tcx, OpTy<'tcx, M::PointerTag>> {
@@ -98,8 +198,8 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> Value<'mir, 'tcx, M>
}
#[inline(always)]
fn from_op(op: OpTy<'tcx, M::PointerTag>) -> Self {
// assert is justified because our `to_op` only ever produces `Indirect` operands.
fn from_op(op: &OpTy<'tcx, M::PointerTag>) -> Self {
// assert is justified because our `to_op_for_read` only ever produces `Indirect` operands.
op.assert_mem_place()
}
@@ -122,11 +222,111 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> Value<'mir, 'tcx, M>
}
}
impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> ValueMut<'mir, 'tcx, M>
for MPlaceTy<'tcx, M::PointerTag>
{
#[inline(always)]
fn layout(&self) -> TyAndLayout<'tcx> {
self.layout
}
#[inline(always)]
fn to_op_for_read(
&self,
_ecx: &InterpCx<'mir, 'tcx, M>,
) -> InterpResult<'tcx, OpTy<'tcx, M::PointerTag>> {
Ok(self.into())
}
#[inline(always)]
fn to_op_for_proj(
&self,
_ecx: &mut InterpCx<'mir, 'tcx, M>,
) -> InterpResult<'tcx, OpTy<'tcx, M::PointerTag>> {
Ok(self.into())
}
#[inline(always)]
fn from_op(op: &OpTy<'tcx, M::PointerTag>) -> Self {
// assert is justified because our `to_op_for_proj` only ever produces `Indirect` operands.
op.assert_mem_place()
}
#[inline(always)]
fn project_downcast(
&self,
ecx: &mut InterpCx<'mir, 'tcx, M>,
variant: VariantIdx,
) -> InterpResult<'tcx, Self> {
ecx.mplace_downcast(self, variant)
}
#[inline(always)]
fn project_field(
&self,
ecx: &mut InterpCx<'mir, 'tcx, M>,
field: usize,
) -> InterpResult<'tcx, Self> {
ecx.mplace_field(self, field)
}
}
impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> ValueMut<'mir, 'tcx, M>
for PlaceTy<'tcx, M::PointerTag>
{
#[inline(always)]
fn layout(&self) -> TyAndLayout<'tcx> {
self.layout
}
#[inline(always)]
fn to_op_for_read(
&self,
ecx: &InterpCx<'mir, 'tcx, M>,
) -> InterpResult<'tcx, OpTy<'tcx, M::PointerTag>> {
// We `force_allocation` here so that `from_op` below can work.
ecx.place_to_op(self)
}
#[inline(always)]
fn to_op_for_proj(
&self,
ecx: &mut InterpCx<'mir, 'tcx, M>,
) -> InterpResult<'tcx, OpTy<'tcx, M::PointerTag>> {
// We `force_allocation` here so that `from_op` below can work.
Ok(ecx.force_allocation(self)?.into())
}
#[inline(always)]
fn from_op(op: &OpTy<'tcx, M::PointerTag>) -> Self {
// assert is justified because our `to_op` only ever produces `Indirect` operands.
op.assert_mem_place().into()
}
#[inline(always)]
fn project_downcast(
&self,
ecx: &mut InterpCx<'mir, 'tcx, M>,
variant: VariantIdx,
) -> InterpResult<'tcx, Self> {
ecx.place_downcast(self, variant)
}
#[inline(always)]
fn project_field(
&self,
ecx: &mut InterpCx<'mir, 'tcx, M>,
field: usize,
) -> InterpResult<'tcx, Self> {
ecx.place_field(self, field)
}
}
macro_rules! make_value_visitor {
($visitor_trait_name:ident, $($mutability:ident)?) => {
($visitor_trait:ident, $value_trait:ident, $($mutability:ident)?) => {
// How to traverse a value and what to do when we are at the leaves.
pub trait $visitor_trait_name<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>>: Sized {
type V: Value<'mir, 'tcx, M>;
pub trait $visitor_trait<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>>: Sized {
type V: $value_trait<'mir, 'tcx, M>;
/// The visitor must have an `InterpCx` in it.
fn ecx(&$($mutability)? self)
@@ -215,19 +415,20 @@ macro_rules! make_value_visitor {
}
fn walk_value(&mut self, v: &Self::V) -> InterpResult<'tcx>
{
trace!("walk_value: type: {}", v.layout().ty);
let ty = v.layout().ty;
trace!("walk_value: type: {ty}");
// Special treatment for special types, where the (static) layout is not sufficient.
match *v.layout().ty.kind() {
match *ty.kind() {
// If it is a trait object, switch to the real type that was used to create it.
ty::Dynamic(..) => {
// unsized values are never immediate, so we can assert_mem_place
let op = v.to_op(self.ecx())?;
let op = v.to_op_for_read(self.ecx())?;
let dest = op.assert_mem_place();
let inner = self.ecx().unpack_dyn_trait(&dest)?.1;
trace!("walk_value: dyn object layout: {:#?}", inner.layout);
let inner_mplace = self.ecx().unpack_dyn_trait(&dest)?.1;
trace!("walk_value: dyn object layout: {:#?}", inner_mplace.layout);
// recurse with the inner type
return self.visit_field(&v, 0, &Value::from_op(inner.into()));
return self.visit_field(&v, 0, &$value_trait::from_op(&inner_mplace.into()));
},
// Slices do not need special handling here: they have `Array` field
// placement with length 0, so we enter the `Array` case below which
@@ -278,10 +479,10 @@ macro_rules! make_value_visitor {
// Visit the fields of this value.
match v.layout().fields {
FieldsShape::Primitive => {},
FieldsShape::Primitive => {}
FieldsShape::Union(fields) => {
self.visit_union(v, fields)?;
},
}
FieldsShape::Arbitrary { ref offsets, .. } => {
// FIXME: We collect in a vec because otherwise there are lifetime
// errors: Projecting to a field needs access to `ecx`.
@@ -291,16 +492,17 @@ macro_rules! make_value_visitor {
})
.collect();
self.visit_aggregate(v, fields.into_iter())?;
},
}
FieldsShape::Array { .. } => {
// Let's get an mplace first.
let op = v.to_op(self.ecx())?;
// Let's get an mplace (or immediate) first.
// This might `force_allocate` if `v` is a `PlaceTy`, but `place_index` does that anyway.
let op = v.to_op_for_proj(self.ecx())?;
// Now we can go over all the fields.
// This uses the *run-time length*, i.e., if we are a slice,
// the dynamic info from the metadata is used.
let iter = self.ecx().operand_array_fields(&op)?
.map(|f| f.and_then(|f| {
Ok(Value::from_op(f))
Ok($value_trait::from_op(&f))
}));
self.visit_aggregate(v, iter)?;
}
@@ -310,7 +512,7 @@ macro_rules! make_value_visitor {
// If this is a multi-variant layout, find the right variant and proceed
// with *its* fields.
Variants::Multiple { .. } => {
let op = v.to_op(self.ecx())?;
let op = v.to_op_for_read(self.ecx())?;
let idx = self.read_discriminant(&op)?;
let inner = v.project_downcast(self.ecx(), idx)?;
trace!("walk_value: variant layout: {:#?}", inner.layout());
@@ -325,5 +527,5 @@ macro_rules! make_value_visitor {
}
}
make_value_visitor!(ValueVisitor,);
make_value_visitor!(MutValueVisitor, mut);
make_value_visitor!(ValueVisitor, Value,);
make_value_visitor!(MutValueVisitor, ValueMut, mut);