diff options
| -rw-r--r-- | src/librustc_mir/transform/const_prop.rs | 20 | ||||
| -rw-r--r-- | src/test/mir-opt/const_prop/mutable_variable_aggregate_partial_read/rustc.main.ConstProp.diff | 15 |
2 files changed, 31 insertions, 4 deletions
diff --git a/src/librustc_mir/transform/const_prop.rs b/src/librustc_mir/transform/const_prop.rs index e898f22ec23..d66c909fe6c 100644 --- a/src/librustc_mir/transform/const_prop.rs +++ b/src/librustc_mir/transform/const_prop.rs @@ -775,6 +775,10 @@ impl<'tcx> Visitor<'tcx> for CanConstProp { // 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) + // Actual store that can possibly even propagate a value | MutatingUse(MutatingUseContext::Store) => { if !self.found_assignment.insert(local) { match &mut self.can_const_prop[local] { @@ -799,7 +803,21 @@ impl<'tcx> Visitor<'tcx> for CanConstProp { | NonMutatingUse(NonMutatingUseContext::Inspect) | NonMutatingUse(NonMutatingUseContext::Projection) | NonUse(_) => {} - _ => { + + // These could be propagated with a smarter analysis or just some careful thinking about + // whether they'd be fine right now. + MutatingUse(MutatingUseContext::AsmOutput) + | MutatingUse(MutatingUseContext::Yield) + | MutatingUse(MutatingUseContext::Drop) + | MutatingUse(MutatingUseContext::Retag) + // These can't ever be propagated under any scheme, as we can't reason about indirect + // mutation. + | NonMutatingUse(NonMutatingUseContext::SharedBorrow) + | NonMutatingUse(NonMutatingUseContext::ShallowBorrow) + | NonMutatingUse(NonMutatingUseContext::UniqueBorrow) + | NonMutatingUse(NonMutatingUseContext::AddressOf) + | MutatingUse(MutatingUseContext::Borrow) + | MutatingUse(MutatingUseContext::AddressOf) => { trace!("local {:?} can't be propagaged because it's used: {:?}", local, context); self.can_const_prop[local] = ConstPropMode::NoPropagation; } diff --git a/src/test/mir-opt/const_prop/mutable_variable_aggregate_partial_read/rustc.main.ConstProp.diff b/src/test/mir-opt/const_prop/mutable_variable_aggregate_partial_read/rustc.main.ConstProp.diff index b88bb9b4915..3cf05f13578 100644 --- a/src/test/mir-opt/const_prop/mutable_variable_aggregate_partial_read/rustc.main.ConstProp.diff +++ b/src/test/mir-opt/const_prop/mutable_variable_aggregate_partial_read/rustc.main.ConstProp.diff @@ -29,17 +29,26 @@ // + ty: i32 // + val: Value(Scalar(0x00000063)) // mir::Constant - // + span: $DIR/mutable_variable_aggregate_partial_read.rs:6:11: 6:13 +- // + span: $DIR/mutable_variable_aggregate_partial_read.rs:6:11: 6:13 ++ // + span: $DIR/mutable_variable_aggregate_partial_read.rs:6:5: 6:13 // + literal: Const { ty: i32, val: Value(Scalar(0x00000063)) } (_1.0: i32) = const 42i32; // scope 1 at $DIR/mutable_variable_aggregate_partial_read.rs:7:5: 7:13 // ty::Const // + ty: i32 // + val: Value(Scalar(0x0000002a)) // mir::Constant - // + span: $DIR/mutable_variable_aggregate_partial_read.rs:7:11: 7:13 +- // + span: $DIR/mutable_variable_aggregate_partial_read.rs:7:11: 7:13 ++ // + span: $DIR/mutable_variable_aggregate_partial_read.rs:7:5: 7:13 // + literal: Const { ty: i32, val: Value(Scalar(0x0000002a)) } StorageLive(_2); // scope 1 at $DIR/mutable_variable_aggregate_partial_read.rs:8:9: 8:10 - _2 = (_1.1: i32); // scope 1 at $DIR/mutable_variable_aggregate_partial_read.rs:8:13: 8:16 +- _2 = (_1.1: i32); // scope 1 at $DIR/mutable_variable_aggregate_partial_read.rs:8:13: 8:16 ++ _2 = const 99i32; // scope 1 at $DIR/mutable_variable_aggregate_partial_read.rs:8:13: 8:16 ++ // ty::Const ++ // + ty: i32 ++ // + val: Value(Scalar(0x00000063)) ++ // mir::Constant ++ // + span: $DIR/mutable_variable_aggregate_partial_read.rs:8:13: 8:16 ++ // + literal: Const { ty: i32, val: Value(Scalar(0x00000063)) } _0 = const (); // scope 0 at $DIR/mutable_variable_aggregate_partial_read.rs:4:11: 9:2 // ty::Const // + ty: () |