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Reject borrows of projections in ConstProp.

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This commit is contained in:
Camille GILLOT 2023-04-28 16:57:40 +00:00
parent e2caebc4a6
commit 1ffe9059c3
4 changed files with 22 additions and 19 deletions
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20
compiler/rustc_mir_transform/src/const_prop.rs
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@ -714,13 +714,22 @@ impl CanConstProp {
}
}
impl Visitor<'_> for CanConstProp {
impl<'tcx> Visitor<'tcx> for CanConstProp {
fn visit_place(&mut self, place: &Place<'tcx>, mut context: PlaceContext, loc: Location) {
use rustc_middle::mir::visit::PlaceContext::*;
// Dereferencing just read the addess of `place.local`.
if place.projection.first() == Some(&PlaceElem::Deref) {
context = NonMutatingUse(NonMutatingUseContext::Copy);
}
self.visit_local(place.local, context, loc);
self.visit_projection(place.as_ref(), context, loc);
}
fn visit_local(&mut self, local: Local, context: PlaceContext, _: Location) {
use rustc_middle::mir::visit::PlaceContext::*;
match context {
// Projections are fine, because `&mut foo.x` will be caught by
// `MutatingUseContext::Borrow` elsewhere.
MutatingUse(MutatingUseContext::Projection)
// These are just stores, where the storing is not propagatable, but there may be later
// mutations of the same local via `Store`
| MutatingUse(MutatingUseContext::Call)
@ -751,7 +760,6 @@ impl Visitor<'_> for CanConstProp {
NonMutatingUse(NonMutatingUseContext::Copy)
| NonMutatingUse(NonMutatingUseContext::Move)
| NonMutatingUse(NonMutatingUseContext::Inspect)
| NonMutatingUse(NonMutatingUseContext::Projection)
| NonMutatingUse(NonMutatingUseContext::PlaceMention)
| NonUse(_) => {}
@ -771,6 +779,8 @@ impl Visitor<'_> for CanConstProp {
trace!("local {:?} can't be propagated because it's used: {:?}", local, context);
self.can_const_prop[local] = ConstPropMode::NoPropagation;
}
MutatingUse(MutatingUseContext::Projection)
| NonMutatingUse(NonMutatingUseContext::Projection) => bug!("visit_place should not pass {context:?} for {local:?}"),
}
}
}

15
tests/mir-opt/const_prop/address_of_pair.fn0.ConstProp.diff
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@ -23,25 +23,20 @@
bb0: {
StorageLive(_2); // scope 0 at $DIR/address_of_pair.rs:+1:9: +1:17
- _2 = (const 1_i32, const false); // scope 0 at $DIR/address_of_pair.rs:+1:20: +1:30
+ _2 = const (1_i32, false); // scope 0 at $DIR/address_of_pair.rs:+1:20: +1:30
_2 = (const 1_i32, const false); // scope 0 at $DIR/address_of_pair.rs:+1:20: +1:30
StorageLive(_3); // scope 1 at $DIR/address_of_pair.rs:+2:9: +2:12
_3 = &raw mut (_2.1: bool); // scope 1 at $SRC_DIR/core/src/ptr/mod.rs:LL:COL
- _2 = (const 1_i32, const false); // scope 2 at $DIR/address_of_pair.rs:+3:5: +3:22
+ _2 = const (1_i32, false); // scope 2 at $DIR/address_of_pair.rs:+3:5: +3:22
_2 = (const 1_i32, const false); // scope 2 at $DIR/address_of_pair.rs:+3:5: +3:22
StorageLive(_4); // scope 2 at $DIR/address_of_pair.rs:+4:5: +6:6
(*_3) = const true; // scope 3 at $DIR/address_of_pair.rs:+5:9: +5:20
_4 = const (); // scope 3 at $DIR/address_of_pair.rs:+4:5: +6:6
StorageDead(_4); // scope 2 at $DIR/address_of_pair.rs:+6:5: +6:6
StorageLive(_5); // scope 2 at $DIR/address_of_pair.rs:+7:9: +7:12
StorageLive(_6); // scope 2 at $DIR/address_of_pair.rs:+7:16: +7:22
- _6 = (_2.1: bool); // scope 2 at $DIR/address_of_pair.rs:+7:16: +7:22
- _5 = Not(move _6); // scope 2 at $DIR/address_of_pair.rs:+7:15: +7:22
+ _6 = const false; // scope 2 at $DIR/address_of_pair.rs:+7:16: +7:22
+ _5 = const true; // scope 2 at $DIR/address_of_pair.rs:+7:15: +7:22
_6 = (_2.1: bool); // scope 2 at $DIR/address_of_pair.rs:+7:16: +7:22
_5 = Not(move _6); // scope 2 at $DIR/address_of_pair.rs:+7:15: +7:22
StorageDead(_6); // scope 2 at $DIR/address_of_pair.rs:+7:21: +7:22
- _0 = _5; // scope 4 at $DIR/address_of_pair.rs:+8:12: +8:15
+ _0 = const true; // scope 4 at $DIR/address_of_pair.rs:+8:12: +8:15
_0 = _5; // scope 4 at $DIR/address_of_pair.rs:+8:12: +8:15
StorageDead(_5); // scope 2 at $DIR/address_of_pair.rs:+9:1: +9:2
StorageDead(_3); // scope 1 at $DIR/address_of_pair.rs:+9:1: +9:2
StorageDead(_2); // scope 0 at $DIR/address_of_pair.rs:+9:1: +9:2

3
tests/mir-opt/const_prop_miscompile.bar.ConstProp.diff
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@ -19,8 +19,7 @@
bb0: {
StorageLive(_1); // scope 0 at $DIR/const_prop_miscompile.rs:+1:9: +1:14
- _1 = (const 1_i32,); // scope 0 at $DIR/const_prop_miscompile.rs:+1:17: +1:21
+ _1 = const (1_i32,); // scope 0 at $DIR/const_prop_miscompile.rs:+1:17: +1:21
_1 = (const 1_i32,); // scope 0 at $DIR/const_prop_miscompile.rs:+1:17: +1:21
StorageLive(_2); // scope 1 at $DIR/const_prop_miscompile.rs:+2:5: +4:6
StorageLive(_3); // scope 2 at $DIR/const_prop_miscompile.rs:+3:10: +3:22
_3 = &raw mut (_1.0: i32); // scope 2 at $DIR/const_prop_miscompile.rs:+3:10: +3:22

3
tests/mir-opt/const_prop_miscompile.foo.ConstProp.diff
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@ -16,8 +16,7 @@
bb0: {
StorageLive(_1); // scope 0 at $DIR/const_prop_miscompile.rs:+1:9: +1:14
- _1 = (const 1_i32,); // scope 0 at $DIR/const_prop_miscompile.rs:+1:17: +1:21
+ _1 = const (1_i32,); // scope 0 at $DIR/const_prop_miscompile.rs:+1:17: +1:21
_1 = (const 1_i32,); // scope 0 at $DIR/const_prop_miscompile.rs:+1:17: +1:21
StorageLive(_2); // scope 1 at $DIR/const_prop_miscompile.rs:+2:6: +2:14
_2 = &mut (_1.0: i32); // scope 1 at $DIR/const_prop_miscompile.rs:+2:6: +2:14
(*_2) = const 5_i32; // scope 1 at $DIR/const_prop_miscompile.rs:+2:5: +2:18