Enum stable_mir::mir::body::Rvalue

pub enum Rvalue {
    AddressOf(Mutability, Place),
    Aggregate(AggregateKind, Vec<Operand>),
    BinaryOp(BinOp, Operand, Operand),
    Cast(CastKind, Operand, Ty),
    CheckedBinaryOp(BinOp, Operand, Operand),
    CopyForDeref(Place),
    Discriminant(Place),
    Len(Place),
    Ref(Region, BorrowKind, Place),
    Repeat(Operand, Const),
    ShallowInitBox(Operand, Ty),
    ThreadLocalRef(CrateItem),
    NullaryOp(NullOp, Ty),
    UnaryOp(UnOp, Operand),
    Use(Operand),
}

Variants

AddressOf(Mutability, Place)

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).

Aggregate(AggregateKind, Vec<Operand>)

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.

BinaryOp(BinOp, Operand, Operand)

• Offset has the same semantics as <*const T>::offset, except that the second parameter may be a usize as well.
• The comparison operations accept bools, chars, signed or unsigned integers, floats, raw pointers, or function pointers and return a bool. 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.

Cast(CastKind, Operand, Ty)

Performs essentially all of the casts that can be performed via as.

This allows for casts from/to a variety of types.

CheckedBinaryOp(BinOp, Operand, Operand)

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.

CopyForDeref(Place)

A CopyForDeref is equivalent to a read from a place. When such a read happens, it is guaranteed that the only use of the returned value is a deref operation, immediately followed by one or more projections.

Discriminant(Place)

Computes the discriminant of the place, returning it as an integer. 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;

Len(Place)

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.

Ref(Region, BorrowKind, Place)

Creates a reference to the place.

Repeat(Operand, Const)

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].

ShallowInitBox(Operand, Ty)

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.

ThreadLocalRef(CrateItem)

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?

NullaryOp(NullOp, Ty)

Computes a value as described by the operation.

UnaryOp(UnOp, Operand)

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.

Use(Operand)

Yields the operand unchanged

Trait Implementations

impl Clone for Rvalue

fn clone(&self) -> Rvalue

Returns a copy of the value.

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

Performs copy-assignment from source.

impl Debug for Rvalue

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

Formats the value using the given formatter.

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: 200 bytes

Size for each variant:

• AddressOf: 39 bytes
• Aggregate: 103 bytes
• BinaryOp: 199 bytes
• Cast: 111 bytes
• CheckedBinaryOp: 199 bytes
• CopyForDeref: 39 bytes
• Discriminant: 39 bytes
• Len: 39 bytes
• Ref: 103 bytes
• Repeat: 175 bytes
• ShallowInitBox: 111 bytes
• ThreadLocalRef: 15 bytes
• NullaryOp: 47 bytes
• UnaryOp: 103 bytes
• Use: 103 bytes