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Avoid cloning place in LocalAnalyzer visitor

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This commit is contained in:
Santiago Pastorino 2019-07-01 23:30:38 +02:00
parent d0accade3e
commit 98d2324875
2 changed files with 91 additions and 56 deletions
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6
src/librustc/mir/mod.rs
View File

@ -1826,6 +1826,12 @@ newtype_index! {
}
}
#[derive(Debug)]
pub struct PlaceRef<'a, 'tcx> {
pub base: &'a PlaceBase<'tcx>,
pub projection: &'a Option<Box<Projection<'tcx>>>,
}
impl<'tcx> Place<'tcx> {
pub const RETURN_PLACE: Place<'tcx> = Place {
base: PlaceBase::Local(RETURN_PLACE),

141
src/librustc_codegen_ssa/mir/analyze.rs
View File

@ -92,6 +92,86 @@ impl<Bx: BuilderMethods<'a, 'tcx>> LocalAnalyzer<'mir, 'a, 'tcx, Bx> {
self.first_assignment[local] = location;
}
}
fn process_place(&mut self,
place_ref: &mir::PlaceRef<'_, 'tcx>,
context: PlaceContext,
location: Location) {
let cx = self.fx.cx;
if let Some(proj) = place_ref.projection {
// Allow uses of projections that are ZSTs or from scalar fields.
let is_consume = match context {
PlaceContext::NonMutatingUse(NonMutatingUseContext::Copy) |
PlaceContext::NonMutatingUse(NonMutatingUseContext::Move) => true,
_ => false
};
if is_consume {
let base_ty =
mir::Place::ty_from(place_ref.base, &proj.base, self.fx.mir, cx.tcx());
let base_ty = self.fx.monomorphize(&base_ty);
// ZSTs don't require any actual memory access.
let elem_ty = base_ty
.projection_ty(cx.tcx(), &proj.elem)
.ty;
let elem_ty = self.fx.monomorphize(&elem_ty);
if cx.layout_of(elem_ty).is_zst() {
return;
}
if let mir::ProjectionElem::Field(..) = proj.elem {
let layout = cx.layout_of(base_ty.ty);
if cx.is_backend_immediate(layout) || cx.is_backend_scalar_pair(layout) {
// Recurse with the same context, instead of `Projection`,
// potentially stopping at non-operand projections,
// which would trigger `not_ssa` on locals.
self.process_place(
&mir::PlaceRef {
base: place_ref.base,
projection: &proj.base,
},
context,
location,
);
return;
}
}
}
// A deref projection only reads the pointer, never needs the place.
if let mir::ProjectionElem::Deref = proj.elem {
self.process_place(
&mir::PlaceRef {
base: place_ref.base,
projection: &proj.base,
},
PlaceContext::NonMutatingUse(NonMutatingUseContext::Copy),
location
);
return;
}
}
// FIXME this is super_place code, is repeated here to avoid cloning place or changing
// visit_place API
let mut context = context;
if place_ref.projection.is_some() {
context = if context.is_mutating_use() {
PlaceContext::MutatingUse(MutatingUseContext::Projection)
} else {
PlaceContext::NonMutatingUse(NonMutatingUseContext::Projection)
};
}
self.visit_place_base(place_ref.base, context, location);
if let Some(box proj) = place_ref.projection {
self.visit_projection(place_ref.base, proj, context, location);
}
}
}
impl<'mir, 'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> Visitor<'tcx>
@ -158,63 +238,12 @@ impl<'mir, 'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> Visitor<'tcx>
context: PlaceContext,
location: Location) {
debug!("visit_place(place={:?}, context={:?})", place, context);
let cx = self.fx.cx;
if let Some(proj) = &place.projection {
// Allow uses of projections that are ZSTs or from scalar fields.
let is_consume = match context {
PlaceContext::NonMutatingUse(NonMutatingUseContext::Copy) |
PlaceContext::NonMutatingUse(NonMutatingUseContext::Move) => true,
_ => false
};
if is_consume {
let base_ty = mir::Place::ty_from(&place.base, &proj.base, self.fx.mir, cx.tcx());
let base_ty = self.fx.monomorphize(&base_ty);
// ZSTs don't require any actual memory access.
let elem_ty = base_ty
.projection_ty(cx.tcx(), &proj.elem)
.ty;
let elem_ty = self.fx.monomorphize(&elem_ty);
if cx.layout_of(elem_ty).is_zst() {
return;
}
if let mir::ProjectionElem::Field(..) = proj.elem {
let layout = cx.layout_of(base_ty.ty);
if cx.is_backend_immediate(layout) || cx.is_backend_scalar_pair(layout) {
// Recurse with the same context, instead of `Projection`,
// potentially stopping at non-operand projections,
// which would trigger `not_ssa` on locals.
self.visit_place(
// FIXME do not clone
&mir::Place {
base: place.base.clone(),
projection: proj.base.clone(),
},
context,
location,
);
return;
}
}
}
// A deref projection only reads the pointer, never needs the place.
if let mir::ProjectionElem::Deref = proj.elem {
return self.visit_place(
// FIXME do not clone
&mir::Place {
base: place.base.clone(),
projection: proj.base.clone(),
},
PlaceContext::NonMutatingUse(NonMutatingUseContext::Copy),
location
);
}
}
self.super_place(place, context, location);
let place_ref = mir::PlaceRef {
base: &place.base,
projection: &place.projection,
};
self.process_place(&place_ref, context, location);
}
fn visit_local(&mut self,