pub struct EarlyOtherwiseBranch;
Expand description
This pass optimizes something like
ⓘ
let x: Option<()>;
let y: Option<()>;
match (x,y) {
(Some(_), Some(_)) => {0},
(None, None) => {2},
_ => {1}
}
into something like
ⓘ
let x: Option<()>;
let y: Option<()>;
let discriminant_x = std::mem::discriminant(x);
let discriminant_y = std::mem::discriminant(y);
if discriminant_x == discriminant_y {
match x {
Some(_) => 0,
None => 2,
}
} else {
1
}
Specifically, it looks for instances of control flow like this:
=================
| BB1 |
|---------------| ============================
| ... | /------> | BBC |
|---------------| | |--------------------------|
| switchInt(Q) | | | _cl = discriminant(P) |
| c | --------/ |--------------------------|
| d | -------\ | switchInt(_cl) |
| ... | | | c | ---> BBC.2
| otherwise | --\ | /--- | otherwise |
================= | | | ============================
| | |
================= | | |
| BBU | <-| | | ============================
|---------------| \-------> | BBD |
|---------------| | |--------------------------|
| unreachable | | | _dl = discriminant(P) |
================= | |--------------------------|
| | switchInt(_dl) |
================= | | d | ---> BBD.2
| BB9 | <--------------- | otherwise |
|---------------| ============================
| ... |
=================
Where the otherwise
branch on BB1
is permitted to either go to BBU
. In the
code:
BB1
isparent
andBBC, BBD
are childrenP
ischild_place
child_ty
is the type of_cl
.Q
isparent_op
.parent_ty
is the type ofQ
.BB9
isdestination
All this is then transformed into:
=======================
| BB1 |
|---------------------| ============================
| ... | /------> | BBEq |
| _s = discriminant(P)| | |--------------------------|
| _t = Ne(Q, _s) | | |--------------------------|
|---------------------| | | switchInt(Q) |
| switchInt(_t) | | | c | ---> BBC.2
| false | --------/ | d | ---> BBD.2
| otherwise | /--------- | otherwise |
======================= | ============================
|
================= |
| BB9 | <-----------/
|---------------|
| ... |
=================
Trait Implementations§
source§impl<'tcx> MirPass<'tcx> for EarlyOtherwiseBranch
impl<'tcx> MirPass<'tcx> for EarlyOtherwiseBranch
source§fn is_enabled(&self, sess: &Session) -> bool
fn is_enabled(&self, sess: &Session) -> bool
Returns
true
if this pass is enabled with the current combination of compiler flags.fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>)
fn name(&self) -> &'static str
fn profiler_name(&self) -> &'static str
fn is_mir_dump_enabled(&self) -> bool
Auto Trait Implementations§
impl Freeze for EarlyOtherwiseBranch
impl RefUnwindSafe for EarlyOtherwiseBranch
impl Send for EarlyOtherwiseBranch
impl Sync for EarlyOtherwiseBranch
impl Unpin for EarlyOtherwiseBranch
impl UnwindSafe for EarlyOtherwiseBranch
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
Mutably borrows from an owned value. Read more
source§impl<T, R> CollectAndApply<T, R> for T
impl<T, R> CollectAndApply<T, R> for T
source§impl<T> Filterable for T
impl<T> Filterable for T
source§fn filterable(
self,
filter_name: &'static str,
) -> RequestFilterDataProvider<T, fn(_: DataRequest<'_>) -> bool>
fn filterable( self, filter_name: &'static str, ) -> RequestFilterDataProvider<T, fn(_: DataRequest<'_>) -> bool>
Creates a filterable data provider with the given name for debugging. Read more
source§impl<T> Instrument for T
impl<T> Instrument for T
source§fn instrument(self, span: Span) -> Instrumented<Self>
fn instrument(self, span: Span) -> Instrumented<Self>
source§fn in_current_span(self) -> Instrumented<Self>
fn in_current_span(self) -> Instrumented<Self>
source§impl<T> IntoEither for T
impl<T> IntoEither for T
source§fn into_either(self, into_left: bool) -> Either<Self, Self>
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 moresource§fn into_either_with<F>(self, into_left: F) -> Either<Self, Self>
fn into_either_with<F>(self, into_left: F) -> Either<Self, Self>
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 moresource§impl<P> IntoQueryParam<P> for P
impl<P> IntoQueryParam<P> for P
fn into_query_param(self) -> P
source§impl<T> MaybeResult<T> for T
impl<T> MaybeResult<T> for T
source§impl<I, T, U> Upcast<I, U> for Twhere
U: UpcastFrom<I, T>,
impl<I, T, U> Upcast<I, U> for Twhere
U: UpcastFrom<I, T>,
source§impl<I, T> UpcastFrom<I, T> for T
impl<I, T> UpcastFrom<I, T> for T
fn upcast_from(from: T, _tcx: I) -> T
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_error: &CycleError, _guar: ErrorGuaranteed, ) -> T
source§impl<T> WithSubscriber for T
impl<T> WithSubscriber for T
source§fn with_subscriber<S>(self, subscriber: S) -> WithDispatch<Self>
fn with_subscriber<S>(self, subscriber: S) -> WithDispatch<Self>
source§fn with_current_subscriber(self) -> WithDispatch<Self>
fn with_current_subscriber(self) -> WithDispatch<Self>
impl<'a, T> Captures<'a> for Twhere
T: ?Sized,
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T: ?Sized,
impl<T> ErasedDestructor for Twhere
T: 'static,
impl<T> MaybeSendSync for 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: 0 bytes