Struct rustc_borrowck::type_check::liveness::local_use_map::LocalUseMap
source · pub(crate) struct LocalUseMap {
first_def_at: IndexVec<Local, Option<AppearanceIndex>>,
first_use_at: IndexVec<Local, Option<AppearanceIndex>>,
first_drop_at: IndexVec<Local, Option<AppearanceIndex>>,
appearances: IndexVec<AppearanceIndex, Appearance>,
}
Expand description
A map that cross references each local with the locations where it is defined (assigned), used, or dropped. Used during liveness computation.
We keep track only of Local
s we’ll do the liveness analysis later,
this means that our internal IndexVec
s will only be sparsely populated.
In the time-memory trade-off between keeping compact vectors with new
indexes (and needing to continuously map the Local
index to its compact
counterpart) and having IndexVec
s that we only use a fraction of, time
(and code simplicity) was favored. The rationale is that we only keep
a small number of IndexVec
s throughout the entire analysis while, in
contrast, we’re accessing each Local
many times.
Fields§
§first_def_at: IndexVec<Local, Option<AppearanceIndex>>
Head of a linked list of definitions of each variable –
definition in this context means assignment, e.g., x
is
defined in x = y
but not y
; that first def is the head of
a linked list that lets you enumerate all places the variable
is assigned.
first_use_at: IndexVec<Local, Option<AppearanceIndex>>
Head of a linked list of uses of each variable – use in
this context means that the existing value of the variable is
read or modified. e.g., y
is used in x = y
but not x
.
Note that DROP(x)
terminators are excluded from this list.
first_drop_at: IndexVec<Local, Option<AppearanceIndex>>
Head of a linked list of drops of each variable – these are a special category of uses corresponding to the drop that we add for each local variable.
appearances: IndexVec<AppearanceIndex, Appearance>
Implementations§
source§impl LocalUseMap
impl LocalUseMap
pub(crate) fn build( live_locals: &[Local], elements: &RegionValueElements, body: &Body<'_> ) -> Self
pub(crate) fn defs(&self, local: Local) -> impl Iterator<Item = PointIndex> + '_
pub(crate) fn uses(&self, local: Local) -> impl Iterator<Item = PointIndex> + '_
pub(crate) fn drops( &self, local: Local ) -> impl Iterator<Item = PointIndex> + '_
Auto Trait Implementations§
impl RefUnwindSafe for LocalUseMap
impl Send for LocalUseMap
impl Sync for LocalUseMap
impl Unpin for LocalUseMap
impl UnwindSafe for LocalUseMap
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
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: 96 bytes