Add additional trace statements to the const propagator
This makes it easier to figure out when const propagation fails.
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@ -295,6 +295,7 @@ impl<'a, 'mir, 'tcx> ConstPropagator<'a, 'mir, 'tcx> {
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}
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fn eval_place(&mut self, place: &Place<'tcx>, source_info: SourceInfo) -> Option<Const<'tcx>> {
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trace!("eval_place(place={:?})", place);
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match *place {
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Place::Base(PlaceBase::Local(loc)) => self.places[loc].clone(),
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Place::Projection(ref proj) => match proj.elem {
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@ -515,6 +516,7 @@ impl<'a, 'mir, 'tcx> ConstPropagator<'a, 'mir, 'tcx> {
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}
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fn replace_with_const(&self, rval: &mut Rvalue<'tcx>, value: Const<'tcx>, span: Span) {
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trace!("attepting to replace {:?} with {:?}", rval, value);
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self.ecx.validate_operand(
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value,
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vec![],
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@ -578,6 +580,10 @@ impl CanConstProp {
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// FIXME(oli-obk): lint variables until they are used in a condition
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// FIXME(oli-obk): lint if return value is constant
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*val = mir.local_kind(local) == LocalKind::Temp;
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if !*val {
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trace!("local {:?} can't be propagated because it's not a temporary", local);
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}
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}
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cpv.visit_mir(mir);
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cpv.can_const_prop
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@ -597,6 +603,7 @@ impl<'tcx> Visitor<'tcx> for CanConstProp {
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// FIXME(oli-obk): we could be more powerful here, if the multiple writes
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// only occur in independent execution paths
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MutatingUse(MutatingUseContext::Store) => if self.found_assignment[local] {
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trace!("local {:?} can't be propagated because of multiple assignments", local);
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self.can_const_prop[local] = false;
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} else {
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self.found_assignment[local] = true
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@ -608,7 +615,10 @@ impl<'tcx> Visitor<'tcx> for CanConstProp {
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NonMutatingUse(NonMutatingUseContext::Projection) |
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MutatingUse(MutatingUseContext::Projection) |
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NonUse(_) => {},
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_ => self.can_const_prop[local] = false,
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_ => {
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trace!("local {:?} can't be propagaged because it's used: {:?}", local, context);
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self.can_const_prop[local] = false;
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},
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}
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}
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}
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