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Add additional trace statements to the const propagator #61184

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merged 1 commit into from
May 26, 2019
+11 −1
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Add additional trace statements to the const propagator #61184

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12 changes: 11 additions & 1 deletion src/librustc_mir/transform/const_prop.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -295,6 +295,7 @@ impl<'a, 'mir, 'tcx> ConstPropagator<'a, 'mir, 'tcx> {
}

fn eval_place(&mut self, place: &Place<'tcx>, source_info: SourceInfo) -> Option<Const<'tcx>> {
trace!("eval_place(place={:?})", place);
match *place {
Place::Base(PlaceBase::Local(loc)) => self.places[loc].clone(),
Place::Projection(ref proj) => match proj.elem {
Expand Down Expand Up @@ -515,6 +516,7 @@ impl<'a, 'mir, 'tcx> ConstPropagator<'a, 'mir, 'tcx> {
}

fn replace_with_const(&self, rval: &mut Rvalue<'tcx>, value: Const<'tcx>, span: Span) {
trace!("attepting to replace {:?} with {:?}", rval, value);
self.ecx.validate_operand(
value,
vec![],
Expand Down Expand Up @@ -578,6 +580,10 @@ impl CanConstProp {
// FIXME(oli-obk): lint variables until they are used in a condition
// FIXME(oli-obk): lint if return value is constant
*val = mir.local_kind(local) == LocalKind::Temp;

if !*val {
trace!("local {:?} can't be propagated because it's not a temporary", local);
}
}
cpv.visit_mir(mir);
cpv.can_const_prop
Expand All @@ -597,6 +603,7 @@ impl<'tcx> Visitor<'tcx> for CanConstProp {
// FIXME(oli-obk): we could be more powerful here, if the multiple writes
// only occur in independent execution paths
MutatingUse(MutatingUseContext::Store) => if self.found_assignment[local] {
trace!("local {:?} can't be propagated because of multiple assignments", local);
self.can_const_prop[local] = false;
} else {
self.found_assignment[local] = true
Expand All @@ -608,7 +615,10 @@ impl<'tcx> Visitor<'tcx> for CanConstProp {
NonMutatingUse(NonMutatingUseContext::Projection) |
MutatingUse(MutatingUseContext::Projection) |
NonUse(_) => {},
_ => self.can_const_prop[local] = false,
_ => {
trace!("local {:?} can't be propagaged because it's used: {:?}", local, context);
self.can_const_prop[local] = false;
},
}
}
}
Expand Down