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Mark reads in statements to avoid overlapping assingments.

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This commit is contained in:
Camille Gillot 2025-09-13 18:07:22 +00:00
parent d51aec7781
commit aee7d703c5
6 changed files with 31 additions and 24 deletions
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29
compiler/rustc_mir_transform/src/dest_prop.rs
View file

@ -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);
@ -590,13 +592,20 @@ fn save_as_intervals<'tcx>(
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);
let is_simple_assignment =
matches!(stmt.kind, StatementKind::Assign(box (_, Rvalue::Use(_))));
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);

6
tests/mir-opt/dest-prop/aggregate.rewrap.DestinationPropagation.panic-abort.diff
View file

@ -9,12 +9,10 @@
bb0: {
- (_1.0: u8) = const 0_u8;
- _0 = copy _1;
- _2 = (copy (_0.0: u8),);
- _0 = copy _2;
+ (_0.0: u8) = const 0_u8;
+ nop;
+ _0 = (copy (_0.0: u8),);
+ nop;
_2 = (copy (_0.0: u8),);
_0 = copy _2;
return;
}
}

6
tests/mir-opt/dest-prop/aggregate.rewrap.DestinationPropagation.panic-unwind.diff
View file

@ -9,12 +9,10 @@
bb0: {
- (_1.0: u8) = const 0_u8;
- _0 = copy _1;
- _2 = (copy (_0.0: u8),);
- _0 = copy _2;
+ (_0.0: u8) = const 0_u8;
+ nop;
+ _0 = (copy (_0.0: u8),);
+ nop;
_2 = (copy (_0.0: u8),);
_0 = copy _2;
return;
}
}

6
tests/mir-opt/dest-prop/aggregate.rs
View file

@ -14,7 +14,8 @@ fn dump_var<T>(_: T) {}
fn rewrap() -> (u8,) {
// CHECK-LABEL: fn rewrap(
// CHECK: (_0.0: u8) = const 0_u8;
// CHECK: _0 = (copy (_0.0: u8),);
// CHECK: _2 = (copy (_0.0: u8),);
// CHECK: _0 = copy _2;
mir! {
let _1: (u8,);
let _2: (u8,);
@ -33,7 +34,8 @@ fn rewrap() -> (u8,) {
fn swap() -> (MaybeUninit<[u8; 10]>, MaybeUninit<[u8; 10]>) {
// CHECK-LABEL: fn swap(
// CHECK: _0 = const
// CHECK: _0 = (copy (_0.1: {{.*}}), copy (_0.0: {{.*}}));
// 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]>);

4
tests/mir-opt/dest-prop/aggregate.swap.DestinationPropagation.panic-abort.diff
View file

@ -13,8 +13,8 @@
- _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};
+ nop;
+ _0 = (copy (_0.1: std::mem::MaybeUninit<[u8; 10]>), copy (_0.0: std::mem::MaybeUninit<[u8; 10]>));
+ _2 = copy _0;
+ _0 = (copy (_2.1: std::mem::MaybeUninit<[u8; 10]>), copy (_2.0: std::mem::MaybeUninit<[u8; 10]>));
+ nop;
return;
}

4
tests/mir-opt/dest-prop/aggregate.swap.DestinationPropagation.panic-unwind.diff
View file

@ -13,8 +13,8 @@
- _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};
+ nop;
+ _0 = (copy (_0.1: std::mem::MaybeUninit<[u8; 10]>), copy (_0.0: std::mem::MaybeUninit<[u8; 10]>));
+ _2 = copy _0;
+ _0 = (copy (_2.1: std::mem::MaybeUninit<[u8; 10]>), copy (_2.0: std::mem::MaybeUninit<[u8; 10]>));
+ nop;
return;
}