pub enum MirPhase {
    Built,
    Const,
    ConstsPromoted,
    DropsLowered,
    Deaggregated,
    GeneratorsLowered,
    Optimized,
}
Expand description

The various “big phases” that MIR goes through.

These phases all describe dialects of MIR. Since all MIR uses the same datastructures, the dialects forbid certain variants or values in certain phases. The sections below summarize the changes, but do not document them thoroughly. The full documentation is found in the appropriate documentation for the thing the change is affecting.

Warning: ordering of variants is significant.

Variants

Built

The dialect of MIR used during all phases before DropsLowered is the same. This is also the MIR that analysis such as borrowck uses.

One important thing to remember about the behavior of this section of MIR is that drop terminators (including drop and replace) are conditional. The elaborate drops pass will then replace each instance of a drop terminator with a nop, an unconditional drop, or a drop conditioned on a drop flag. Of course, this means that it is important that the drop elaboration can accurately recognize when things are initialized and when things are de-initialized. That means any code running on this version of MIR must be sure to produce output that drop elaboration can reason about. See the section on the drop terminatorss for more details.

Const

ConstsPromoted

This phase checks the MIR for promotable elements and takes them out of the main MIR body by creating a new MIR body per promoted element. After this phase (and thus the termination of the mir_promoted query), these promoted elements are available in the promoted_mir query.

DropsLowered

Beginning with this phase, the following variants are disallowed:

And the following variant is allowed:

Furthermore, Drop now uses explicit drop flags visible in the MIR and reaching a Drop terminator means that the auto-generated drop glue will be invoked. Also, Copy operands are allowed for non-Copy types.

Deaggregated

Beginning with this phase, the following variant is disallowed:

And the following variant is allowed:

GeneratorsLowered

Before this phase, generators are in the “source code” form, featuring yield statements and such. With this phase change, they are transformed into a proper state machine. Running optimizations before this change can be potentially dangerous because the source code is to some extent a “lie.” In particular, yield terminators effectively make the value of all locals visible to the caller. This means that dead store elimination before them, or code motion across them, is not correct in general. This is also exasperated by type checking having pre-computed a list of the types that it thinks are ok to be live across a yield point - this is necessary to decide eg whether autotraits are implemented. Introducing new types across a yield point will lead to ICEs becaues of this.

Beginning with this phase, the following variants are disallowed:

Optimized

Implementations

Gets the index of the current MirPhase within the set of all MirPhases.

Trait Implementations

Returns a copy of the value. Read more

Performs copy-assignment from source. Read more

Formats the value using the given formatter. Read more

This method returns an Ordering between self and other. Read more

Compares and returns the maximum of two values. Read more

Compares and returns the minimum of two values. Read more

Restrict a value to a certain interval. Read more

This method tests for self and other values to be equal, and is used by ==. Read more

This method tests for !=.

This method returns an ordering between self and other values if one exists. Read more

This method tests less than (for self and other) and is used by the < operator. Read more

This method tests less than or equal to (for self and other) and is used by the <= operator. Read more

This method tests greater than (for self and other) and is used by the > operator. Read more

This method tests greater than or equal to (for self and other) and is used by the >= operator. Read more

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

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

The main entry point for folding. To fold a value t with a folder f call: t.try_fold_with(f). Read more

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

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

The entry point for visiting. To visit a value t with a visitor v call: t.visit_with(v). Read more

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

Returns true if this self has any regions that escape binder (and hence are not bound by it). Read more

“Free” regions in this context means that it has any region that is not (a) erased or (b) late-bound. Read more

True if there are any un-erased free regions.

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

True if there are any late-bound regions

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

Auto Trait Implementations

Blanket Implementations

Gets the TypeId of self. Read more

Immutably borrows from an owned value. Read more

Mutably borrows from an owned value. Read more

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

This method tries to recover the query key from the given DepNode, something which is needed when forcing DepNodes 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

Returns the argument unchanged.

Calls U::from(self).

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

The resulting type after obtaining ownership.

Creates owned data from borrowed data, usually by cloning. Read more

🔬 This is a nightly-only experimental API. (toowned_clone_into)

Uses borrowed data to replace owned data, usually by cloning. Read more

The type returned in the event of a conversion error.

Performs the conversion.

The type returned in the event of a conversion error.

Performs the conversion.

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: 1 byte

Size for each variant:

  • Built: 0 bytes
  • Const: 0 bytes
  • ConstsPromoted: 0 bytes
  • DropsLowered: 0 bytes
  • Deaggregated: 0 bytes
  • GeneratorsLowered: 0 bytes
  • Optimized: 0 bytes