pub enum Operand<'tcx> {
Copy(Place<'tcx>),
Move(Place<'tcx>),
Constant(Box<ConstOperand<'tcx>>),
}
Expand description
An operand in MIR represents a “value” in Rust, the definition of which is undecided and part of the memory model. One proposal for a definition of values can be found on UCG.
The most common way to create values is via loading a place. Loading a place is an operation which reads the memory of the place and converts it to a value. This is a fundamentally typed operation. The nature of the value produced depends on the type of the conversion. Furthermore, there may be other effects: if the type has a validity constraint loading the place might be UB if the validity constraint is not met.
Needs clarification: Is loading a place that has its variant index set well-formed? Miri currently implements it, but it seems like this may be something to check against in the validator.
Variants§
Copy(Place<'tcx>)
Creates a value by loading the given place.
Before drop elaboration, the type of the place must be Copy
. After drop elaboration there
is no such requirement.
Move(Place<'tcx>)
Creates a value by performing loading the place, just like the Copy
operand.
This may additionally overwrite the place with uninit
bytes, depending on how we decide
in UCG#188. You should not emit MIR that may attempt a subsequent second load of this
place without first re-initializing it.
Needs clarification: The operational impact of Move
is unclear. Currently (both in
Miri and codegen) it has no effect at all unless it appears in an argument to Call
; for
Call
it allows the argument to be passed to the callee “in-place”, i.e. the callee might
just get a reference to this place instead of a full copy. Miri implements this with a
combination of aliasing model “protectors” and putting uninit
into the place. Ralf
proposes that we don’t want these semantics for Move
in regular assignments, because
loading a place should not have side-effects, and the aliasing model “protectors” are
inherently tied to a function call. Are these the semantics we want for MIR? Is this
something we can even decide without knowing more about Rust’s memory model?
Constant(Box<ConstOperand<'tcx>>)
Constants are already semantically values, and remain unchanged.
Implementations§
Source§impl<'tcx> Operand<'tcx>
impl<'tcx> Operand<'tcx>
Sourcepub fn function_handle(
tcx: TyCtxt<'tcx>,
def_id: DefId,
args: impl IntoIterator<Item = GenericArg<'tcx>>,
span: Span,
) -> Self
pub fn function_handle( tcx: TyCtxt<'tcx>, def_id: DefId, args: impl IntoIterator<Item = GenericArg<'tcx>>, span: Span, ) -> Self
Convenience helper to make a constant that refers to the fn
with given DefId
and args. Since this is used to synthesize
MIR, assumes user_ty
is None.
pub fn is_move(&self) -> bool
Sourcepub fn const_from_scalar(
tcx: TyCtxt<'tcx>,
ty: Ty<'tcx>,
val: Scalar,
span: Span,
) -> Operand<'tcx>
pub fn const_from_scalar( tcx: TyCtxt<'tcx>, ty: Ty<'tcx>, val: Scalar, span: Span, ) -> Operand<'tcx>
Convenience helper to make a literal-like constant from a given scalar value.
Since this is used to synthesize MIR, assumes user_ty
is None.
pub fn to_copy(&self) -> Self
Sourcepub fn place(&self) -> Option<Place<'tcx>>
pub fn place(&self) -> Option<Place<'tcx>>
Returns the Place
that is the target of this Operand
, or None
if this Operand
is a
constant.
Sourcepub fn constant(&self) -> Option<&ConstOperand<'tcx>>
pub fn constant(&self) -> Option<&ConstOperand<'tcx>>
Returns the ConstOperand
that is the target of this Operand
, or None
if this Operand
is a
place.
Sourcepub fn const_fn_def(&self) -> Option<(DefId, GenericArgsRef<'tcx>)>
pub fn const_fn_def(&self) -> Option<(DefId, GenericArgsRef<'tcx>)>
Gets the ty::FnDef
from an operand if it’s a constant function item.
While this is unlikely in general, it’s the normal case of what you’ll
find as the func
in a TerminatorKind::Call
.
Trait Implementations§
Source§impl<'tcx, '__ctx> HashStable<StableHashingContext<'__ctx>> for Operand<'tcx>
impl<'tcx, '__ctx> HashStable<StableHashingContext<'__ctx>> for Operand<'tcx>
fn hash_stable( &self, __hcx: &mut StableHashingContext<'__ctx>, __hasher: &mut StableHasher, )
Source§impl<'tcx> TypeFoldable<TyCtxt<'tcx>> for Operand<'tcx>
impl<'tcx> TypeFoldable<TyCtxt<'tcx>> for Operand<'tcx>
Source§fn try_fold_with<__F: FallibleTypeFolder<TyCtxt<'tcx>>>(
self,
__folder: &mut __F,
) -> Result<Self, __F::Error>
fn try_fold_with<__F: FallibleTypeFolder<TyCtxt<'tcx>>>( self, __folder: &mut __F, ) -> Result<Self, __F::Error>
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fn fold_with<F>(self, folder: &mut F) -> Selfwhere
F: TypeFolder<I>,
try_fold_with
for use with infallible
folders. Do not override this method, to ensure coherence with
try_fold_with
.Source§impl<'tcx> TypeVisitable<TyCtxt<'tcx>> for Operand<'tcx>
impl<'tcx> TypeVisitable<TyCtxt<'tcx>> for Operand<'tcx>
Source§fn visit_with<__V: TypeVisitor<TyCtxt<'tcx>>>(
&self,
__visitor: &mut __V,
) -> __V::Result
fn visit_with<__V: TypeVisitor<TyCtxt<'tcx>>>( &self, __visitor: &mut __V, ) -> __V::Result
impl<'tcx> StructuralPartialEq for Operand<'tcx>
Auto Trait Implementations§
impl<'tcx> DynSend for Operand<'tcx>
impl<'tcx> DynSync for Operand<'tcx>
impl<'tcx> Freeze for Operand<'tcx>
impl<'tcx> !RefUnwindSafe for Operand<'tcx>
impl<'tcx> Send for Operand<'tcx>
impl<'tcx> Sync for Operand<'tcx>
impl<'tcx> Unpin for Operand<'tcx>
impl<'tcx> !UnwindSafe for Operand<'tcx>
Blanket Implementations§
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impl<T> BorrowMut<T> for Twhere
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default fn fingerprint_style() -> FingerprintStyle
Source§default fn to_fingerprint(&self, tcx: Tcx) -> Fingerprint
default fn to_fingerprint(&self, tcx: Tcx) -> Fingerprint
default fn to_debug_str(&self, _: Tcx) -> String
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Layout§
Note: Most layout information is completely unstable and may even differ between compilations. The only exception is types with certain repr(...)
attributes. Please see the Rust Reference's “Type Layout” chapter for details on type layout guarantees.
Size: 24 bytes
Size for each variant:
Copy
: 16 bytesMove
: 16 bytesConstant
: 8 bytes