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Stop propagating to locals that were marks as unpropagatable.

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We used to erase these values immediately after propagation, but some
things slipped through and it caused us to still initialize huge locals.
This commit is contained in:
Oliver Scherer 2020-07-27 15:01:25 +02:00
parent c3454c0007
commit b26a7d5cd9
2 changed files with 13 additions and 9 deletions
Download patch file Download diff file Expand all files Collapse all files

16
src/librustc_mir/transform/const_prop.rs
View file

@ -157,14 +157,19 @@ struct ConstPropMachine<'mir, 'tcx> {
written_only_inside_own_block_locals: FxHashSet<Local>,
/// Locals that need to be cleared after every block terminates.
only_propagate_inside_block_locals: BitSet<Local>,
can_const_prop: IndexVec<Local, ConstPropMode>,
}
impl<'mir, 'tcx> ConstPropMachine<'mir, 'tcx> {
fn new(only_propagate_inside_block_locals: BitSet<Local>) -> Self {
fn new(
only_propagate_inside_block_locals: BitSet<Local>,
can_const_prop: IndexVec<Local, ConstPropMode>,
) -> Self {
Self {
stack: Vec::new(),
written_only_inside_own_block_locals: Default::default(),
only_propagate_inside_block_locals,
can_const_prop,
}
}
}
@ -243,6 +248,9 @@ impl<'mir, 'tcx> interpret::Machine<'mir, 'tcx> for ConstPropMachine<'mir, 'tcx>
local: Local,
) -> InterpResult<'tcx, Result<&'a mut LocalValue<Self::PointerTag>, MemPlace<Self::PointerTag>>>
{
if ecx.machine.can_const_prop[local] == ConstPropMode::NoPropagation {
throw_machine_stop_str!("tried to write to a local that is marked as not propagatable")
}
if frame == 0 && ecx.machine.only_propagate_inside_block_locals.contains(local) {
ecx.machine.written_only_inside_own_block_locals.insert(local);
}
@ -287,7 +295,6 @@ impl<'mir, 'tcx> interpret::Machine<'mir, 'tcx> for ConstPropMachine<'mir, 'tcx>
struct ConstPropagator<'mir, 'tcx> {
ecx: InterpCx<'mir, 'tcx, ConstPropMachine<'mir, 'tcx>>,
tcx: TyCtxt<'tcx>,
can_const_prop: IndexVec<Local, ConstPropMode>,
param_env: ParamEnv<'tcx>,
// FIXME(eddyb) avoid cloning these two fields more than once,
// by accessing them through `ecx` instead.
@ -347,7 +354,7 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
tcx,
span,
param_env,
ConstPropMachine::new(only_propagate_inside_block_locals),
ConstPropMachine::new(only_propagate_inside_block_locals, can_const_prop),
(),
);
@ -373,7 +380,6 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
ecx,
tcx,
param_env,
can_const_prop,
// FIXME(eddyb) avoid cloning these two fields more than once,
// by accessing them through `ecx` instead.
source_scopes: body.source_scopes.clone(),
@ -1031,7 +1037,7 @@ impl<'mir, 'tcx> MutVisitor<'tcx> for ConstPropagator<'mir, 'tcx> {
let source_info = statement.source_info;
self.source_info = Some(source_info);
if let StatementKind::Assign(box (place, ref mut rval)) = statement.kind {
let can_const_prop = self.can_const_prop[place.local];
let can_const_prop = self.ecx.machine.can_const_prop[place.local];
if let Some(()) = self.const_prop(rval, source_info, place) {
// This will return None if the above `const_prop` invocation only "wrote" a
// type whose creation requires no write. E.g. a generator whose initial state

6
src/test/mir-opt/const_prop/mutable_variable_aggregate_mut_ref.main.ConstProp.diff
View file

@ -23,15 +23,13 @@
// + ty: i32
// + val: Value(Scalar(0x0000002a))
// mir::Constant
- // + span: $DIR/mutable_variable_aggregate_mut_ref.rs:5:18: 5:20
+ // + span: $DIR/mutable_variable_aggregate_mut_ref.rs:5:17: 5:25
// + span: $DIR/mutable_variable_aggregate_mut_ref.rs:5:18: 5:20
// + literal: Const { ty: i32, val: Value(Scalar(0x0000002a)) }
// ty::Const
// + ty: i32
// + val: Value(Scalar(0x0000002b))
// mir::Constant
- // + span: $DIR/mutable_variable_aggregate_mut_ref.rs:5:22: 5:24
+ // + span: $DIR/mutable_variable_aggregate_mut_ref.rs:5:17: 5:25
// + span: $DIR/mutable_variable_aggregate_mut_ref.rs:5:22: 5:24
// + literal: Const { ty: i32, val: Value(Scalar(0x0000002b)) }
StorageLive(_2); // scope 1 at $DIR/mutable_variable_aggregate_mut_ref.rs:6:9: 6:10
_2 = &mut _1; // scope 1 at $DIR/mutable_variable_aggregate_mut_ref.rs:6:13: 6:19