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Rollup merge of #61184 - wesleywiser:const_prop_tracing, r=oli-obk 

Add additional trace statements to the const propagator

This makes it easier to figure out when const propagation fails.
This commit is contained in:
Mazdak Farrokhzad 2019-05-26 02:13:32 +02:00 committed by GitHub
parent f530f90b56 9bfbbd2a78
commit d8b828beea
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GPG Key ID: 4AEE18F83AFDEB23
1 changed files with 11 additions and 1 deletions
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12
src/librustc_mir/transform/const_prop.rs
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@ -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 {
@ -516,6 +517,7 @@ 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![],
@ -579,6 +581,10 @@ 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
@ -598,6 +604,7 @@ 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
@ -609,7 +616,10 @@ 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;
},
}
}
}