Enum rustc_middle::mir::syntax::Rvalue
source · pub enum Rvalue<'tcx> {
Show 15 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<'tcx>, Ty<'tcx>),
UnaryOp(UnOp, Operand<'tcx>),
Discriminant(Place<'tcx>),
Aggregate(Box<AggregateKind<'tcx>>, IndexVec<FieldIdx, Operand<'tcx>>),
ShallowInitBox(Operand<'tcx>, Ty<'tcx>),
CopyForDeref(Place<'tcx>),
}
Expand description
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)
with a bool
indicating an error condition.
For addition, subtraction, and multiplication on integers the error condition is set when the infinite precision result would not be equal to the actual result.
Other combinations of types and operators are unsupported.
NullaryOp(NullOp<'tcx>, 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>>, IndexVec<FieldIdx, 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.
CopyForDeref(Place<'tcx>)
A CopyForDeref is equivalent to a read from a place at the
codegen level, but is treated specially by drop elaboration. When such a read happens, it
is guaranteed (via nature of the mir_opt Derefer
in rustc_mir_transform/src/deref_separator)
that the only use of the returned value is a deref operation, immediately
followed by one or more projections. Drop elaboration treats this rvalue as if the
read never happened and just projects further. This allows simplifying various MIR
optimizations and codegen backends that previously had to handle deref operations anywhere
in a place.
Implementations§
source§impl<'tcx> Rvalue<'tcx>
impl<'tcx> Rvalue<'tcx>
Rvalues
sourcepub fn is_safe_to_remove(&self) -> bool
pub fn is_safe_to_remove(&self) -> bool
Returns true if rvalue can be safely removed when the result is unused.
source§impl<'tcx> Rvalue<'tcx>
impl<'tcx> Rvalue<'tcx>
pub fn ty<D>(&self, local_decls: &D, tcx: TyCtxt<'tcx>) -> Ty<'tcx>where D: HasLocalDecls<'tcx> + ?Sized,
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§
source§impl<'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 )
source§impl<'tcx> PartialEq<Rvalue<'tcx>> for Rvalue<'tcx>
impl<'tcx> PartialEq<Rvalue<'tcx>> for Rvalue<'tcx>
source§impl<'tcx> TypeFoldable<TyCtxt<'tcx>> for Rvalue<'tcx>
impl<'tcx> TypeFoldable<TyCtxt<'tcx>> for Rvalue<'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>
source§fn fold_with<F>(self, folder: &mut F) -> Selfwhere
F: TypeFolder<I>,
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 Rvalue<'tcx>
impl<'tcx> TypeVisitable<TyCtxt<'tcx>> for Rvalue<'tcx>
source§fn visit_with<__V: TypeVisitor<TyCtxt<'tcx>>>(
&self,
__visitor: &mut __V
) -> ControlFlow<__V::BreakTy>
fn visit_with<__V: TypeVisitor<TyCtxt<'tcx>>>( &self, __visitor: &mut __V ) -> ControlFlow<__V::BreakTy>
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§
source§impl<T> BorrowMut<T> for Twhere
T: ?Sized,
impl<T> BorrowMut<T> for Twhere T: ?Sized,
source§fn borrow_mut(&mut self) -> &mut T
fn borrow_mut(&mut self) -> &mut T
source§impl<T, R> CollectAndApply<T, R> for T
impl<T, R> CollectAndApply<T, R> for T
source§impl<Tcx, T> DepNodeParams<Tcx> for Twhere
Tcx: DepContext,
T: for<'a> HashStable<StableHashingContext<'a>> + Debug,
impl<Tcx, T> DepNodeParams<Tcx> for Twhere Tcx: DepContext, T: for<'a> HashStable<StableHashingContext<'a>> + Debug,
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
source§default fn recover(_: Tcx, _: &DepNode) -> Option<T>
default fn recover(_: Tcx, _: &DepNode) -> Option<T>
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.source§impl<P> IntoQueryParam<P> for P
impl<P> IntoQueryParam<P> for P
fn into_query_param(self) -> P
source§impl<'tcx, T> IsSuggestable<'tcx> for Twhere
T: TypeVisitable<TyCtxt<'tcx>> + TypeFoldable<TyCtxt<'tcx>>,
impl<'tcx, T> IsSuggestable<'tcx> for Twhere T: TypeVisitable<TyCtxt<'tcx>> + TypeFoldable<TyCtxt<'tcx>>,
source§impl<T> MaybeResult<T> for T
impl<T> MaybeResult<T> for T
source§impl<'tcx, T> ToPredicate<'tcx, T> for T
impl<'tcx, T> ToPredicate<'tcx, T> for T
fn to_predicate(self, _tcx: TyCtxt<'tcx>) -> T
source§impl<'tcx, T> TypeVisitableExt<'tcx> for Twhere
T: TypeVisitable<TyCtxt<'tcx>>,
impl<'tcx, T> TypeVisitableExt<'tcx> for Twhere T: TypeVisitable<TyCtxt<'tcx>>,
source§fn has_vars_bound_at_or_above(&self, binder: DebruijnIndex) -> bool
fn has_vars_bound_at_or_above(&self, binder: DebruijnIndex) -> bool
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.source§fn has_vars_bound_above(&self, binder: DebruijnIndex) -> bool
fn has_vars_bound_above(&self, binder: DebruijnIndex) -> bool
true
if this type has any regions that escape binder
(and
hence are not bound by it).source§fn has_escaping_bound_vars(&self) -> bool
fn has_escaping_bound_vars(&self) -> bool
true
if this type has regions that are not a part of the type.
For example, for<'a> fn(&'a i32)
return false
, while fn(&'a i32)
would return true
. The latter can occur when traversing through the
former. Read morefn has_type_flags(&self, flags: TypeFlags) -> bool
fn has_projections(&self) -> bool
fn has_inherent_projections(&self) -> bool
fn has_opaque_types(&self) -> bool
fn has_generators(&self) -> bool
fn references_error(&self) -> bool
fn error_reported(&self) -> Result<(), ErrorGuaranteed>
fn has_non_region_param(&self) -> bool
fn has_infer_regions(&self) -> bool
fn has_infer_types(&self) -> bool
fn has_non_region_infer(&self) -> bool
fn has_infer(&self) -> bool
fn has_placeholders(&self) -> bool
fn has_non_region_placeholders(&self) -> bool
fn has_param(&self) -> bool
source§fn has_free_regions(&self) -> bool
fn has_free_regions(&self) -> bool
fn has_erased_regions(&self) -> bool
source§fn has_erasable_regions(&self) -> bool
fn has_erasable_regions(&self) -> bool
source§fn is_global(&self) -> bool
fn is_global(&self) -> bool
source§fn has_late_bound_regions(&self) -> bool
fn has_late_bound_regions(&self) -> bool
source§fn has_non_region_late_bound(&self) -> bool
fn has_non_region_late_bound(&self) -> bool
source§fn has_late_bound_vars(&self) -> bool
fn has_late_bound_vars(&self) -> bool
source§fn still_further_specializable(&self) -> bool
fn still_further_specializable(&self) -> bool
impl
specialization.source§impl<Tcx, T> Value<Tcx> for Twhere
Tcx: DepContext,
impl<Tcx, T> Value<Tcx> for Twhere Tcx: DepContext,
default fn from_cycle_error( tcx: Tcx, cycle: &[QueryInfo], _guar: ErrorGuaranteed ) -> T
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
: 32 bytesRepeat
: 40 bytesRef
: 40 bytesThreadLocalRef
: 16 bytesAddressOf
: 32 bytesLen
: 24 bytesCast
: 40 bytesBinaryOp
: 24 bytesCheckedBinaryOp
: 24 bytesNullaryOp
: 32 bytesUnaryOp
: 40 bytesDiscriminant
: 24 bytesAggregate
: 40 bytesShallowInitBox
: 40 bytesCopyForDeref
: 24 bytes