Enum rustc_middle::mir::Rvalue
source · [−]pub enum Rvalue<'tcx> {
Show 14 variants
Use(Operand<'tcx>),
Repeat(Operand<'tcx>, Const<'tcx>),
Ref(Region<'tcx>, BorrowKind, Place<'tcx>),
ThreadLocalRef(DefId),
AddressOf(Mutability, Place<'tcx>),
Len(Place<'tcx>),
Cast(CastKind, Operand<'tcx>, Ty<'tcx>),
BinaryOp(BinOp, Box<(Operand<'tcx>, Operand<'tcx>)>),
CheckedBinaryOp(BinOp, Box<(Operand<'tcx>, Operand<'tcx>)>),
NullaryOp(NullOp, Ty<'tcx>),
UnaryOp(UnOp, Operand<'tcx>),
Discriminant(Place<'tcx>),
Aggregate(Box<AggregateKind<'tcx>>, Vec<Operand<'tcx>>),
ShallowInitBox(Operand<'tcx>, Ty<'tcx>),
}
Expand description
Rvalues The various kinds of rvalues that can appear in MIR.
Not all of these are allowed at every MirPhase
- when this is the case, it’s stated below.
Computing any rvalue begins by evaluating the places and operands in some order (Needs
clarification: Which order?). These are then used to produce a “value” - the same kind of
value that an Operand
produces.
Variants
Use(Operand<'tcx>)
Yields the operand unchanged
Repeat(Operand<'tcx>, Const<'tcx>)
Creates an array where each element is the value of the operand.
This is the cause of a bug in the case where the repetition count is zero because the value is not dropped, see #74836.
Corresponds to source code like [x; 32]
.
Ref(Region<'tcx>, BorrowKind, Place<'tcx>)
Creates a reference of the indicated kind to the place.
There is not much to document here, because besides the obvious parts the semantics of this are essentially entirely a part of the aliasing model. There are many UCG issues discussing exactly what the behavior of this operation should be.
Shallow
borrows are disallowed after drop lowering.
ThreadLocalRef(DefId)
Creates a pointer/reference to the given thread local.
The yielded type is a *mut T
if the static is mutable, otherwise if the static is extern a
*const T
, and if neither of those apply a &T
.
Note: This is a runtime operation that actually executes code and is in this sense more
like a function call. Also, eliminating dead stores of this rvalue causes fn main() {}
to
SIGILL for some reason that I (JakobDegen) never got a chance to look into.
Needs clarification: Are there weird additional semantics here related to the runtime nature of this operation?
AddressOf(Mutability, Place<'tcx>)
Creates a pointer with the indicated mutability to the place.
This is generated by pointer casts like &v as *const _
or raw address of expressions like
&raw v
or addr_of!(v)
.
Like with references, the semantics of this operation are heavily dependent on the aliasing model.
Len(Place<'tcx>)
Yields the length of the place, as a usize
.
If the type of the place is an array, this is the array length. For slices ([T]
, not
&[T]
) this accesses the place’s metadata to determine the length. This rvalue is
ill-formed for places of other types.
Cast(CastKind, Operand<'tcx>, Ty<'tcx>)
Performs essentially all of the casts that can be performed via as
.
This allows for casts from/to a variety of types.
FIXME: Document exactly which CastKind
s allow which types of casts. Figure out why
ArrayToPointer
and MutToConstPointer
are special.
BinaryOp(BinOp, Box<(Operand<'tcx>, Operand<'tcx>)>)
Offset
has the same semantics asoffset
, except that the second parameter may be ausize
as well.- The comparison operations accept
bool
s,char
s, signed or unsigned integers, floats, raw pointers, or function pointers and return abool
. The types of the operands must be matching, up to the usual caveat of the lifetimes in function pointers. - Left and right shift operations accept signed or unsigned integers not necessarily of the same type and return a value of the same type as their LHS. Like in Rust, the RHS is truncated as needed.
- The
Bit*
operations accept signed integers, unsigned integers, or bools with matching types and return a value of that type. - The remaining operations accept signed integers, unsigned integers, or floats with matching types and return a value of that type.
CheckedBinaryOp(BinOp, Box<(Operand<'tcx>, Operand<'tcx>)>)
Same as BinaryOp
, but yields (T, bool)
instead of T
. In addition to performing the
same computation as the matching BinaryOp
, checks if the infinite precison result would be
unequal to the actual result and sets the bool
if this is the case.
This only supports addition, subtraction, multiplication, and shift operations on integers.
NullaryOp(NullOp, Ty<'tcx>)
Computes a value as described by the operation.
UnaryOp(UnOp, Operand<'tcx>)
Exactly like BinaryOp
, but less operands.
Also does two’s-complement arithmetic. Negation requires a signed integer or a float; bitwise not requires a signed integer, unsigned integer, or bool. Both operation kinds return a value with the same type as their operand.
Discriminant(Place<'tcx>)
Computes the discriminant of the place, returning it as an integer of type
discriminant_ty
. Returns zero for types without discriminant.
The validity requirements for the underlying value are undecided for this rvalue, see
#91095. Note too that the value of the discriminant is not the same thing as the
variant index; use discriminant_for_variant
to convert.
Aggregate(Box<AggregateKind<'tcx>>, Vec<Operand<'tcx>>)
Creates an aggregate value, like a tuple or struct.
This is needed because dataflow analysis needs to distinguish
dest = Foo { x: ..., y: ... }
from dest.x = ...; dest.y = ...;
in the case that Foo
has a destructor.
Disallowed after deaggregation for all aggregate kinds except Array
and Generator
. After
generator lowering, Generator
aggregate kinds are disallowed too.
ShallowInitBox(Operand<'tcx>, Ty<'tcx>)
Transmutes a *mut u8
into shallow-initialized Box<T>
.
This is different from a normal transmute because dataflow analysis will treat the box as initialized but its content as uninitialized. Like other pointer casts, this in general affects alias analysis.
Implementations
sourceimpl<'tcx> Rvalue<'tcx>
impl<'tcx> Rvalue<'tcx>
pub fn ty<D>(&self, local_decls: &D, tcx: TyCtxt<'tcx>) -> Ty<'tcx> where
D: HasLocalDecls<'tcx>,
sourcepub fn initialization_state(&self) -> RvalueInitializationState
pub fn initialization_state(&self) -> RvalueInitializationState
Returns true
if this rvalue is deeply initialized (most rvalues) or
whether its only shallowly initialized (Rvalue::Box
).
Trait Implementations
sourceimpl<'tcx, '__ctx> HashStable<StableHashingContext<'__ctx>> for Rvalue<'tcx>
impl<'tcx, '__ctx> HashStable<StableHashingContext<'__ctx>> for Rvalue<'tcx>
fn hash_stable(
&self,
__hcx: &mut StableHashingContext<'__ctx>,
__hasher: &mut StableHasher
)
sourceimpl<'tcx> TypeFoldable<'tcx> for Rvalue<'tcx>
impl<'tcx> TypeFoldable<'tcx> for Rvalue<'tcx>
sourcefn try_super_fold_with<F: FallibleTypeFolder<'tcx>>(
self,
folder: &mut F
) -> Result<Self, F::Error>
fn try_super_fold_with<F: FallibleTypeFolder<'tcx>>(
self,
folder: &mut F
) -> Result<Self, F::Error>
Traverses the type in question, typically by calling try_fold_with
on
each field/element. This is true even for types of interest such as
Ty
. This should only be called within TypeFolder
methods, when
non-custom traversals are desired for types of interest. Read more
sourcefn super_visit_with<V: TypeVisitor<'tcx>>(
&self,
visitor: &mut V
) -> ControlFlow<V::BreakTy>
fn super_visit_with<V: TypeVisitor<'tcx>>(
&self,
visitor: &mut V
) -> ControlFlow<V::BreakTy>
Traverses the type in question, typically by calling visit_with
on
each field/element. This is true even for types of interest such as
Ty
. This should only be called within TypeVisitor
methods, when
non-custom traversals are desired for types of interest. Read more
sourcefn try_fold_with<F: FallibleTypeFolder<'tcx>>(
self,
folder: &mut F
) -> Result<Self, F::Error>
fn try_fold_with<F: FallibleTypeFolder<'tcx>>(
self,
folder: &mut F
) -> Result<Self, F::Error>
The main entry point for folding. To fold a value t
with a folder f
call: t.try_fold_with(f)
. Read more
sourcefn fold_with<F: TypeFolder<'tcx, Error = !>>(self, folder: &mut F) -> Self
fn fold_with<F: TypeFolder<'tcx, Error = !>>(self, folder: &mut F) -> Self
A convenient alternative to try_fold_with
for use with infallible
folders. Do not override this method, to ensure coherence with
try_fold_with
. Read more
sourcefn super_fold_with<F: TypeFolder<'tcx, Error = !>>(self, folder: &mut F) -> Self
fn super_fold_with<F: TypeFolder<'tcx, Error = !>>(self, folder: &mut F) -> Self
A convenient alternative to try_super_fold_with
for use with
infallible folders. Do not override this method, to ensure coherence
with try_super_fold_with
. Read more
sourcefn visit_with<V: TypeVisitor<'tcx>>(
&self,
visitor: &mut V
) -> ControlFlow<V::BreakTy>
fn visit_with<V: TypeVisitor<'tcx>>(
&self,
visitor: &mut V
) -> ControlFlow<V::BreakTy>
The entry point for visiting. To visit a value t
with a visitor v
call: t.visit_with(v)
. Read more
sourcefn has_vars_bound_at_or_above(&self, binder: DebruijnIndex) -> bool
fn has_vars_bound_at_or_above(&self, binder: DebruijnIndex) -> bool
Returns true
if self
has any late-bound regions that are either
bound by binder
or bound by some binder outside of binder
.
If binder
is ty::INNERMOST
, this indicates whether
there are any late-bound regions that appear free. Read more
sourcefn has_vars_bound_above(&self, binder: DebruijnIndex) -> bool
fn has_vars_bound_above(&self, binder: DebruijnIndex) -> bool
Returns true
if this self
has any regions that escape binder
(and
hence are not bound by it). Read more
fn has_escaping_bound_vars(&self) -> bool
fn has_type_flags(&self, flags: TypeFlags) -> bool
fn has_projections(&self) -> bool
fn has_opaque_types(&self) -> bool
fn references_error(&self) -> bool
fn error_reported(&self) -> Option<ErrorGuaranteed>
fn has_param_types_or_consts(&self) -> bool
fn has_infer_regions(&self) -> bool
fn has_infer_types(&self) -> bool
fn has_infer_types_or_consts(&self) -> bool
fn needs_infer(&self) -> bool
fn has_placeholders(&self) -> bool
fn needs_subst(&self) -> bool
sourcefn has_free_regions(&self) -> bool
fn has_free_regions(&self) -> bool
“Free” regions in this context means that it has any region that is not (a) erased or (b) late-bound. Read more
fn has_erased_regions(&self) -> bool
sourcefn has_erasable_regions(&self) -> bool
fn has_erasable_regions(&self) -> bool
True if there are any un-erased free regions.
sourcefn is_global(&self) -> bool
fn is_global(&self) -> bool
Indicates whether this value references only ‘global’ generic parameters that are the same regardless of what fn we are in. This is used for caching. Read more
sourcefn has_late_bound_regions(&self) -> bool
fn has_late_bound_regions(&self) -> bool
True if there are any late-bound regions
sourcefn still_further_specializable(&self) -> bool
fn still_further_specializable(&self) -> bool
Indicates whether this value still has parameters/placeholders/inference variables
which could be replaced later, in a way that would change the results of impl
specialization. Read more
impl<'tcx> StructuralPartialEq for Rvalue<'tcx>
Auto Trait Implementations
impl<'tcx> !RefUnwindSafe for Rvalue<'tcx>
impl<'tcx> !Send for Rvalue<'tcx>
impl<'tcx> !Sync for Rvalue<'tcx>
impl<'tcx> Unpin for Rvalue<'tcx>
impl<'tcx> !UnwindSafe for Rvalue<'tcx>
Blanket Implementations
sourceimpl<T> BorrowMut<T> for T where
T: ?Sized,
impl<T> BorrowMut<T> for T where
T: ?Sized,
const: unstable · sourcefn borrow_mut(&mut self) -> &mut T
fn borrow_mut(&mut self) -> &mut T
Mutably borrows from an owned value. Read more
sourceimpl<Ctxt, T> DepNodeParams<Ctxt> for T where
Ctxt: DepContext,
T: for<'a> HashStable<StableHashingContext<'a>> + Debug,
impl<Ctxt, T> DepNodeParams<Ctxt> for T where
Ctxt: DepContext,
T: for<'a> HashStable<StableHashingContext<'a>> + Debug,
default fn fingerprint_style() -> FingerprintStyle
sourcedefault fn to_fingerprint(&self, tcx: Ctxt) -> Fingerprint
default fn to_fingerprint(&self, tcx: Ctxt) -> Fingerprint
This method turns the parameters of a DepNodeConstructor into an opaque Fingerprint to be used in DepNode. Not all DepNodeParams support being turned into a Fingerprint (they don’t need to if the corresponding DepNode is anonymous). Read more
default fn to_debug_str(&self, Ctxt) -> String
sourcedefault fn recover(Ctxt, &DepNode<<Ctxt as DepContext>::DepKind>) -> Option<T>
default fn recover(Ctxt, &DepNode<<Ctxt as DepContext>::DepKind>) -> Option<T>
This method tries to recover the query key from the given DepNode
,
something which is needed when forcing DepNode
s during red-green
evaluation. The query system will only call this method if
fingerprint_style()
is not FingerprintStyle::Opaque
.
It is always valid to return None
here, in which case incremental
compilation will treat the query as having changed instead of forcing it. Read more
sourceimpl<T> MaybeResult<T> for T
impl<T> MaybeResult<T> for T
sourceimpl<T> ToOwned for T where
T: Clone,
impl<T> ToOwned for T where
T: Clone,
type Owned = T
type Owned = T
The resulting type after obtaining ownership.
sourcefn clone_into(&self, target: &mut T)
fn clone_into(&self, target: &mut T)
toowned_clone_into
)Uses borrowed data to replace owned data, usually by cloning. Read more
impl<'a, T> Captures<'a> for T where
T: ?Sized,
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: 40 bytes
Size for each variant:
Use
: 31 bytesRepeat
: 39 bytesRef
: 31 bytesThreadLocalRef
: 11 bytesAddressOf
: 23 bytesLen
: 23 bytesCast
: 39 bytesBinaryOp
: 15 bytesCheckedBinaryOp
: 15 bytesNullaryOp
: 15 bytesUnaryOp
: 31 bytesDiscriminant
: 23 bytesAggregate
: 39 bytesShallowInitBox
: 39 bytes