diff --git a/compiler/rustc_mir_transform/src/dest_prop.rs b/compiler/rustc_mir_transform/src/dest_prop.rs index 9ba2d274691de..c57483a681140 100644 --- a/compiler/rustc_mir_transform/src/dest_prop.rs +++ b/compiler/rustc_mir_transform/src/dest_prop.rs @@ -567,13 +567,15 @@ fn save_as_intervals<'tcx>( // the written-to locals as live in the second half of the statement. // We also ensure that operands read by terminators conflict with writes by that terminator. // For instance a function call may read args after having written to the destination. - VisitPlacesWith(|place, ctxt| match DefUse::for_place(place, ctxt) { - DefUse::Def | DefUse::Use | DefUse::PartialWrite => { - if let Some(relevant) = relevant.shrink[place.local] { - values.insert(relevant, twostep); + VisitPlacesWith(|place: Place<'tcx>, ctxt| { + if let Some(relevant) = relevant.shrink[place.local] { + match DefUse::for_place(place, ctxt) { + DefUse::Def | DefUse::Use | DefUse::PartialWrite => { + values.insert(relevant, twostep); + } + DefUse::NonUse => {} } } - DefUse::NonUse => {} }) .visit_terminator(term, loc); @@ -588,15 +590,32 @@ fn save_as_intervals<'tcx>( twostep = TwoStepIndex::from_u32(twostep.as_u32() + 1); debug_assert_eq!(twostep, two_step_loc(loc, Effect::After)); append_at(&mut values, &state, twostep); - // Ensure we have a non-zero live range even for dead stores. This is done by marking - // all the written-to locals as live in the second half of the statement. - VisitPlacesWith(|place, ctxt| match DefUse::for_place(place, ctxt) { - DefUse::Def | DefUse::PartialWrite => { - if let Some(relevant) = relevant.shrink[place.local] { - values.insert(relevant, twostep); + // Like terminators, ensure we have a non-zero live range even for dead stores. + // Some rvalues interleave reads and writes, for instance `Rvalue::Aggregate`, see + // https://github.com/rust-lang/rust/issues/146383. By precaution, treat statements + // as behaving so by default. + // We make an exception for simple assignments `_a.stuff = {copy|move} _b.stuff`, + // as marking `_b` live here would prevent unification. + let is_simple_assignment = match stmt.kind { + StatementKind::Assign(box ( + lhs, + Rvalue::CopyForDeref(rhs) + | Rvalue::Use(Operand::Copy(rhs) | Operand::Move(rhs)), + )) => lhs.projection == rhs.projection, + _ => false, + }; + VisitPlacesWith(|place: Place<'tcx>, ctxt| { + if let Some(relevant) = relevant.shrink[place.local] { + match DefUse::for_place(place, ctxt) { + DefUse::Def | DefUse::PartialWrite => { + values.insert(relevant, twostep); + } + DefUse::Use if !is_simple_assignment => { + values.insert(relevant, twostep); + } + DefUse::Use | DefUse::NonUse => {} } } - DefUse::Use | DefUse::NonUse => {} }) .visit_statement(stmt, loc); diff --git a/tests/mir-opt/dest-prop/aggregate.rewrap.DestinationPropagation.panic-abort.diff b/tests/mir-opt/dest-prop/aggregate.rewrap.DestinationPropagation.panic-abort.diff new file mode 100644 index 0000000000000..e80660f176b7b --- /dev/null +++ b/tests/mir-opt/dest-prop/aggregate.rewrap.DestinationPropagation.panic-abort.diff @@ -0,0 +1,19 @@ +- // MIR for `rewrap` before DestinationPropagation ++ // MIR for `rewrap` after DestinationPropagation + + fn rewrap() -> (u8,) { + let mut _0: (u8,); + let mut _1: (u8,); + let mut _2: (u8,); + + bb0: { +- (_1.0: u8) = const 0_u8; +- _0 = copy _1; ++ (_0.0: u8) = const 0_u8; ++ nop; + _2 = (copy (_0.0: u8),); + _0 = copy _2; + return; + } + } + diff --git a/tests/mir-opt/dest-prop/aggregate.rewrap.DestinationPropagation.panic-unwind.diff b/tests/mir-opt/dest-prop/aggregate.rewrap.DestinationPropagation.panic-unwind.diff new file mode 100644 index 0000000000000..e80660f176b7b --- /dev/null +++ b/tests/mir-opt/dest-prop/aggregate.rewrap.DestinationPropagation.panic-unwind.diff @@ -0,0 +1,19 @@ +- // MIR for `rewrap` before DestinationPropagation ++ // MIR for `rewrap` after DestinationPropagation + + fn rewrap() -> (u8,) { + let mut _0: (u8,); + let mut _1: (u8,); + let mut _2: (u8,); + + bb0: { +- (_1.0: u8) = const 0_u8; +- _0 = copy _1; ++ (_0.0: u8) = const 0_u8; ++ nop; + _2 = (copy (_0.0: u8),); + _0 = copy _2; + return; + } + } + diff --git a/tests/mir-opt/dest-prop/aggregate.rs b/tests/mir-opt/dest-prop/aggregate.rs new file mode 100644 index 0000000000000..636852159eb4c --- /dev/null +++ b/tests/mir-opt/dest-prop/aggregate.rs @@ -0,0 +1,51 @@ +//@ test-mir-pass: DestinationPropagation +// EMIT_MIR_FOR_EACH_PANIC_STRATEGY + +#![feature(custom_mir, core_intrinsics)] +#![allow(internal_features)] + +use std::intrinsics::mir::*; +use std::mem::MaybeUninit; + +fn dump_var(_: T) {} + +// EMIT_MIR aggregate.rewrap.DestinationPropagation.diff +#[custom_mir(dialect = "runtime")] +fn rewrap() -> (u8,) { + // CHECK-LABEL: fn rewrap( + // CHECK: (_0.0: u8) = const 0_u8; + // CHECK: _2 = (copy (_0.0: u8),); + // CHECK: _0 = copy _2; + mir! { + let _1: (u8,); + let _2: (u8,); + { + _1.0 = 0; + RET = _1; + _2 = (RET.0, ); + RET = _2; + Return() + } + } +} + +// EMIT_MIR aggregate.swap.DestinationPropagation.diff +#[custom_mir(dialect = "runtime")] +fn swap() -> (MaybeUninit<[u8; 10]>, MaybeUninit<[u8; 10]>) { + // CHECK-LABEL: fn swap( + // CHECK: _0 = const + // CHECK: _2 = copy _0; + // CHECK: _0 = (copy (_2.1: {{.*}}), copy (_2.0: {{.*}})); + mir! { + let _1: (MaybeUninit<[u8; 10]>, MaybeUninit<[u8; 10]>); + let _2: (MaybeUninit<[u8; 10]>, MaybeUninit<[u8; 10]>); + let _3: (); + { + _1 = const { (MaybeUninit::new([0; 10]), MaybeUninit::new([1; 10])) }; + _2 = _1; + _1 = (_2.1, _2.0); + RET = _1; + Return() + } + } +} diff --git a/tests/mir-opt/dest-prop/aggregate.swap.DestinationPropagation.panic-abort.diff b/tests/mir-opt/dest-prop/aggregate.swap.DestinationPropagation.panic-abort.diff new file mode 100644 index 0000000000000..3aaad3aaf6920 --- /dev/null +++ b/tests/mir-opt/dest-prop/aggregate.swap.DestinationPropagation.panic-abort.diff @@ -0,0 +1,22 @@ +- // MIR for `swap` before DestinationPropagation ++ // MIR for `swap` after DestinationPropagation + + fn swap() -> (MaybeUninit<[u8; 10]>, MaybeUninit<[u8; 10]>) { + let mut _0: (std::mem::MaybeUninit<[u8; 10]>, std::mem::MaybeUninit<[u8; 10]>); + let mut _1: (std::mem::MaybeUninit<[u8; 10]>, std::mem::MaybeUninit<[u8; 10]>); + let mut _2: (std::mem::MaybeUninit<[u8; 10]>, std::mem::MaybeUninit<[u8; 10]>); + let mut _3: (); + + bb0: { +- _1 = const swap::{constant#6}; +- _2 = copy _1; +- _1 = (copy (_2.1: std::mem::MaybeUninit<[u8; 10]>), copy (_2.0: std::mem::MaybeUninit<[u8; 10]>)); +- _0 = copy _1; ++ _0 = const swap::{constant#6}; ++ _2 = copy _0; ++ _0 = (copy (_2.1: std::mem::MaybeUninit<[u8; 10]>), copy (_2.0: std::mem::MaybeUninit<[u8; 10]>)); ++ nop; + return; + } + } + diff --git a/tests/mir-opt/dest-prop/aggregate.swap.DestinationPropagation.panic-unwind.diff b/tests/mir-opt/dest-prop/aggregate.swap.DestinationPropagation.panic-unwind.diff new file mode 100644 index 0000000000000..3aaad3aaf6920 --- /dev/null +++ b/tests/mir-opt/dest-prop/aggregate.swap.DestinationPropagation.panic-unwind.diff @@ -0,0 +1,22 @@ +- // MIR for `swap` before DestinationPropagation ++ // MIR for `swap` after DestinationPropagation + + fn swap() -> (MaybeUninit<[u8; 10]>, MaybeUninit<[u8; 10]>) { + let mut _0: (std::mem::MaybeUninit<[u8; 10]>, std::mem::MaybeUninit<[u8; 10]>); + let mut _1: (std::mem::MaybeUninit<[u8; 10]>, std::mem::MaybeUninit<[u8; 10]>); + let mut _2: (std::mem::MaybeUninit<[u8; 10]>, std::mem::MaybeUninit<[u8; 10]>); + let mut _3: (); + + bb0: { +- _1 = const swap::{constant#6}; +- _2 = copy _1; +- _1 = (copy (_2.1: std::mem::MaybeUninit<[u8; 10]>), copy (_2.0: std::mem::MaybeUninit<[u8; 10]>)); +- _0 = copy _1; ++ _0 = const swap::{constant#6}; ++ _2 = copy _0; ++ _0 = (copy (_2.1: std::mem::MaybeUninit<[u8; 10]>), copy (_2.0: std::mem::MaybeUninit<[u8; 10]>)); ++ nop; + return; + } + } +