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Revert "Make LocalAnalizer visitor iterate instead of recurse" #61641

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merged 1 commit into from
Jun 8, 2019
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Revert "Make LocalAnalizer visitor iterate instead of recurse" #61641

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85 changes: 37 additions & 48 deletions src/librustc_codegen_ssa/mir/analyze.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -154,62 +154,51 @@ impl<'mir, 'a: 'mir, 'tcx: 'a, Bx: BuilderMethods<'a, 'tcx>> Visitor<'tcx>
context: PlaceContext,
location: Location) {
debug!("visit_place(place={:?}, context={:?})", place, context);
let mut context = context;
let cx = self.fx.cx;

place.iterate(|place_base, place_projections| {
for proj in place_projections {
// 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 = proj.base.ty(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.
continue;
}
}
if let mir::Place::Projection(ref proj) = *place {
// 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 = proj.base.ty(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;
}

// A deref projection only reads the pointer, never needs the place.
if let mir::ProjectionElem::Deref = proj.elem {
return self.visit_place(
&proj.base,
PlaceContext::NonMutatingUse(NonMutatingUseContext::Copy),
location
);
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(&proj.base, context, location);
return;
}
}

context = if context.is_mutating_use() {
PlaceContext::MutatingUse(MutatingUseContext::Projection)
} else {
PlaceContext::NonMutatingUse(NonMutatingUseContext::Projection)
};
}

// Default base visit behavior
if let mir::PlaceBase::Local(local) = place_base {
self.visit_local(local, context, location);
// A deref projection only reads the pointer, never needs the place.
if let mir::ProjectionElem::Deref = proj.elem {
return self.visit_place(
&proj.base,
PlaceContext::NonMutatingUse(NonMutatingUseContext::Copy),
location
);
}
});
}

self.super_place(place, context, location);
}

fn visit_local(&mut self,
Expand Down