OperandValue in rustc_codegen_ssa::mir::operand - Rust
Description: The representation of a Rust value. The enum variant is in fact uniquely determined by the value’s type, but is kept as a safety check.

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## OperandValue

# Enum OperandValue

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    pub enum OperandValue<V> {
        Ref(PlaceValue<V>),
        Immediate(V),
        Pair(V, V),
        ZeroSized,
    }

Expand description

The representation of a Rust value. The enum variant is in fact uniquely determined by the value’s type, but is kept as a safety check.

## Variants§

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### Ref(PlaceValue<V>)

A reference to the actual operand. The data is guaranteed to be valid for the operand’s lifetime. The second value, if any, is the extra data (vtable or length) which indicates that it refers to an unsized rvalue.

An `OperandValue` must be this variant for any type for which `LayoutTypeCodegenMethods::is_backend_ref` returns `true`. (That basically amounts to “isn’t one of the other variants”.)

This holds a `PlaceValue` (like a `PlaceRef` does) with a pointer to the location holding the value. The type behind that pointer is the one returned by `LayoutTypeCodegenMethods::backend_type`.

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### Immediate(V)

A single LLVM immediate value.

An `OperandValue` must be this variant for any type for which `LayoutTypeCodegenMethods::is_backend_immediate` returns `true`. The backend value in this variant must be the immediate backend type, as returned by `LayoutTypeCodegenMethods::immediate_backend_type`.

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### Pair(V, V)

A pair of immediate LLVM values. Used by wide pointers too.

#### §Invariants

- For `Pair(a, b)`, `a` is always at offset 0, but may have `FieldIdx(1..)`
- `b` is not at offset 0, because `V` is not a 1ZST type.
- `a` and `b` will have a different FieldIdx, but otherwise `b`’s may be lower or they may not be adjacent, due to arbitrary numbers of 1ZST fields that will not affect the shape of the data which determines if `Pair` will be used.
- An `OperandValue` must be this variant for any type for which `LayoutTypeCodegenMethods::is_backend_scalar_pair` returns `true`.
- The backend values in this variant must be the immediate backend types, as returned by `LayoutTypeCodegenMethods::scalar_pair_element_backend_type` with `immediate: true`.

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### ZeroSized

A value taking no bytes, and which therefore needs no LLVM value at all.

If you ever need a `V` to pass to something, get a fresh poison value from `ConstCodegenMethods::const_poison`.

An `OperandValue` must be this variant for any type for which `is_zst` on its `Layout` returns `true`. Note however that these values can still require alignment.

## Implementations§

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### impl<V: CodegenObject> OperandValue<V>

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#### pub(crate) fn try_pointer_parts(self) -> Option<(V, Option<V>)>

Return the data pointer and optional metadata as backend values if this value can be treat as a pointer.

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#### pub(crate) fn pointer_parts(self) -> (V, Option<V>)

Treat this value as a pointer and return the data pointer and optional metadata as backend values.

If you’re making a place, use `Self::deref` instead.

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#### pub(crate) fn deref(self, align: Align) -> PlaceValue<V>

Treat this value as a pointer and return the place to which it points.

The pointer immediate doesn’t inherently know its alignment, so you need to pass it in. If you want to get it from a type’s ABI alignment, then maybe you want `OperandRef::deref` instead.

This is the inverse of `PlaceValue::address`.

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#### pub(crate) fn is_expected_variant_for_type<'tcx, Cx: LayoutTypeCodegenMethods<'tcx>>( &self, cx: &Cx, ty: TyAndLayout<'tcx>, ) -> bool

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### impl<'a, 'tcx, V: CodegenObject> OperandValue<V>

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#### pub fn poison<Bx: BuilderMethods<'a, 'tcx, Value = V>>( bx: &mut Bx, layout: TyAndLayout<'tcx>, ) -> OperandValue<V>

Returns an `OperandValue` that’s generally UB to use in any way.

Depending on the `layout`, returns `ZeroSized` for ZSTs, an `Immediate` or `Pair` containing poison value(s), or a `Ref` containing a poison pointer.

Supports sized types only.

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#### pub fn store<Bx: BuilderMethods<'a, 'tcx, Value = V>>( self, bx: &mut Bx, dest: PlaceRef<'tcx, V>, )

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#### pub fn volatile_store<Bx: BuilderMethods<'a, 'tcx, Value = V>>( self, bx: &mut Bx, dest: PlaceRef<'tcx, V>, )

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#### pub fn unaligned_volatile_store<Bx: BuilderMethods<'a, 'tcx, Value = V>>( self, bx: &mut Bx, dest: PlaceRef<'tcx, V>, )

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#### pub fn nontemporal_store<Bx: BuilderMethods<'a, 'tcx, Value = V>>( self, bx: &mut Bx, dest: PlaceRef<'tcx, V>, )

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#### pub(crate) fn store_with_flags<Bx: BuilderMethods<'a, 'tcx, Value = V>>( self, bx: &mut Bx, dest: PlaceRef<'tcx, V>, flags: MemFlags, )

## Trait Implementations§

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### impl<V: Clone> Clone for OperandValue<V>

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#### fn clone(&self) -> OperandValue<V>

Returns a duplicate of the value. Read more
1.0.0 (const: unstable) · Source§

#### fn clone_from(&mut self, source: &Self)

Performs copy-assignment from `source`. Read more
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### impl<V: Debug> Debug for OperandValue<V>

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#### fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter. Read more
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### impl<V: Copy> Copy for OperandValue<V>

## Auto Trait Implementations§

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### impl<V> DynSend for OperandValue<V>
where V: DynSend,

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### impl<V> DynSync for OperandValue<V>
where V: DynSync,

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### impl<V> Freeze for OperandValue<V>
where V: Freeze,

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### impl<V> RefUnwindSafe for OperandValue<V>
where V: RefUnwindSafe,

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### impl<V> Send for OperandValue<V>
where V: Send,

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### impl<V> Sync for OperandValue<V>
where V: Sync,

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### impl<V> Unpin for OperandValue<V>
where V: Unpin,

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### impl<V> UnsafeUnpin for OperandValue<V>
where V: UnsafeUnpin,

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### impl<V> UnwindSafe for OperandValue<V>
where V: UnwindSafe,

## Blanket Implementations§

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### impl<T> Aligned for T

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#### const ALIGN: Alignment

Alignment of `Self`.
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### impl<T> Any for T
where T: 'static + ?Sized,

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#### fn type_id(&self) -> TypeId

Gets the `TypeId` of `self`. Read more
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### impl<'tcx, T> ArenaAllocatable<'tcx, IsCopy> for T
where T: Copy,

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#### fn allocate_on(self, arena: &'tcx Arena<'tcx>) -> &'tcx mut T

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#### fn allocate_from_iter( arena: &'tcx Arena<'tcx>, iter: impl IntoIterator<Item = T>, ) -> &'tcx mut [T]

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### impl<'tcx, T> ArenaAllocatable<'tcx, IsCopy> for T
where T: Copy,

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#### fn allocate_on(self, arena: &'tcx Arena<'tcx>) -> &'tcx mut T

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#### fn allocate_from_iter( arena: &'tcx Arena<'tcx>, iter: impl IntoIterator<Item = T>, ) -> &'tcx mut [T]

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### impl<T> Borrow<T> for T
where T: ?Sized,

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#### fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
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### impl<T> BorrowMut<T> for T
where T: ?Sized,

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#### fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more
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### impl<T> CloneToUninit for T
where T: Clone,

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#### unsafe fn clone_to_uninit(&self, dest: *mut u8)

🔬This is a nightly-only experimental API. (`clone_to_uninit`)
Performs copy-assignment from `self` to `dest`. Read more
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### impl<T, R> CollectAndApply<T, R> for T

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#### fn collect_and_apply<I, F>(iter: I, f: F) -> R
where I: Iterator<Item = T>, F: FnOnce(&[T]) -> R,

Equivalent to `f(&iter.collect::<Vec<_>>())`.

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#### type Output = R

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### impl<T> DynClone for T
where T: Clone,

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#### fn __clone_box(&self, _: Private) -> *mut ()

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### impl<T> From<T> for T

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#### fn from(t: T) -> T

Returns the argument unchanged.

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### impl<T> Instrument for T

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#### fn instrument(self, span: Span) -> Instrumented<Self>

Instruments this type with the provided `Span`, returning an `Instrumented` wrapper. Read more
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#### fn in_current_span(self) -> Instrumented<Self>

Instruments this type with the current `Span`, returning an `Instrumented` wrapper. Read more
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### impl<T, U> Into<U> for T
where U: From<T>,

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#### fn into(self) -> U

Calls `U::from(self)`.

That is, this conversion is whatever the implementation of `From<T> for U` chooses to do.

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### impl<T> IntoEither for T

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#### fn into_either(self, into_left: bool) -> Either<Self, Self>

Converts `self` into a `Left` variant of `Either<Self, Self>` if `into_left` is `true`. Converts `self` into a `Right` variant of `Either<Self, Self>` otherwise. Read more
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#### fn into_either_with<F>(self, into_left: F) -> Either<Self, Self>
where F: FnOnce(&Self) -> bool,

Converts `self` into a `Left` variant of `Either<Self, Self>` if `into_left(&self)` returns `true`. Converts `self` into a `Right` variant of `Either<Self, Self>` otherwise. Read more
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### impl<K> IntoQueryKey<K> for K

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#### fn into_query_key(self) -> K

Argument conversion from `Self` to `K`. This should always be a very cheap conversion, e.g. `LocalDefId::to_def_id`.
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### impl<T> MaybeResult<T> for T

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#### type Error = !

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#### fn from(_: Result<T, <T as MaybeResult<T>>::Error>) -> T

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#### fn to_result(self) -> Result<T, <T as MaybeResult<T>>::Error>

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### impl<T> Pointable for T

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#### const ALIGN: usize

The alignment of pointer.
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#### type Init = T

The type for initializers.
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#### unsafe fn init(init: <T as Pointable>::Init) -> usize

Initializes a with the given initializer. Read more
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#### unsafe fn deref<'a>(ptr: usize) -> &'a T

Dereferences the given pointer. Read more
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#### unsafe fn deref_mut<'a>(ptr: usize) -> &'a mut T

Mutably dereferences the given pointer. Read more
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#### unsafe fn drop(ptr: usize)

Drops the object pointed to by the given pointer. Read more
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### impl<T> Same for T

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#### type Output = T

Should always be `Self`
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### impl<T> ToOwned for T
where T: Clone,

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#### type Owned = T

The resulting type after obtaining ownership.
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#### fn to_owned(&self) -> T

Creates owned data from borrowed data, usually by cloning. Read more
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#### fn clone_into(&self, target: &mut T)

Uses borrowed data to replace owned data, usually by cloning. Read more
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### impl<T, U> TryFrom<U> for T
where U: Into<T>,

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#### type Error = Infallible

The type returned in the event of a conversion error.
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#### fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.
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### impl<T, U> TryInto<U> for T
where U: TryFrom<T>,

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#### type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.
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#### fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.
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### impl<I, T, U> Upcast<I, U> for T
where U: UpcastFrom<I, T>,

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#### fn upcast(self, interner: I) -> U

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### impl<I, T> UpcastFrom<I, T> for T

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#### fn upcast_from(from: T, _tcx: I) -> T

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### impl<V, T> VZip<V> for T
where V: MultiLane<T>,

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#### fn vzip(self) -> V

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### impl<T> WithSubscriber for T

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#### fn with_subscriber<S>(self, subscriber: S) -> WithDispatch<Self>
where S: Into<Dispatch>,

Attaches the provided `Subscriber` to this type, returning a `WithDispatch` wrapper. Read more
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#### fn with_current_subscriber(self) -> WithDispatch<Self>

Attaches the current default `Subscriber` to this type, returning a `WithDispatch` wrapper. Read more
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### impl<T> ErasedDestructor for T
where T: 'static,

## Layout§

Note: Unable to compute type layout, possibly due to this type having generic parameters. Layout can only be computed for concrete, fully-instantiated types.