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Auto merge of #147804 - tmiasko:move-copy, r=<try>
Turn moves into copies after copy propagation
2 parents f464759 + 9921d20 commit 09003ac

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91 files changed

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‎compiler/rustc_mir_transform/src/copy_prop.rs‎

Lines changed: 1 addition & 39 deletions
Original file line numberDiff line numberDiff line change
@@ -46,10 +46,7 @@ impl<'tcx> crate::MirPass<'tcx> for CopyProp {
4646
return;
4747
}
4848

49-
let fully_moved = fully_moved_locals(&ssa, body);
50-
debug!(?fully_moved);
51-
52-
Replacer { tcx, copy_classes: ssa.copy_classes(), fully_moved, storage_to_remove }
49+
Replacer { tcx, copy_classes: ssa.copy_classes(), storage_to_remove }
5350
.visit_body_preserves_cfg(body);
5451

5552
crate::simplify::remove_unused_definitions(body);
@@ -60,43 +57,9 @@ impl<'tcx> crate::MirPass<'tcx> for CopyProp {
6057
}
6158
}
6259

63-
/// `SsaLocals` computed equivalence classes between locals considering copy/move assignments.
64-
///
65-
/// This function also returns whether all the `move?` in the pattern are `move` and not copies.
66-
/// A local which is in the bitset can be replaced by `move _a`. Otherwise, it must be
67-
/// replaced by `copy _a`, as we cannot move multiple times from `_a`.
68-
///
69-
/// If an operand copies `_c`, it must happen before the assignment `_d = _c`, otherwise it is UB.
70-
/// This means that replacing it by a copy of `_a` if ok, since this copy happens before `_c` is
71-
/// moved, and therefore that `_d` is moved.
72-
#[instrument(level = "trace", skip(ssa, body))]
73-
fn fully_moved_locals(ssa: &SsaLocals, body: &Body<'_>) -> DenseBitSet<Local> {
74-
let mut fully_moved = DenseBitSet::new_filled(body.local_decls.len());
75-
76-
for (_, rvalue, _) in ssa.assignments(body) {
77-
let Rvalue::Use(Operand::Copy(place) | Operand::Move(place)) = rvalue else {
78-
continue;
79-
};
80-
81-
let Some(rhs) = place.as_local() else { continue };
82-
if !ssa.is_ssa(rhs) {
83-
continue;
84-
}
85-
86-
if let Rvalue::Use(Operand::Copy(_)) = rvalue {
87-
fully_moved.remove(rhs);
88-
}
89-
}
90-
91-
ssa.meet_copy_equivalence(&mut fully_moved);
92-
93-
fully_moved
94-
}
95-
9660
/// Utility to help performing substitution of `*pattern` by `target`.
9761
struct Replacer<'a, 'tcx> {
9862
tcx: TyCtxt<'tcx>,
99-
fully_moved: DenseBitSet<Local>,
10063
storage_to_remove: DenseBitSet<Local>,
10164
copy_classes: &'a IndexSlice<Local, Local>,
10265
}
@@ -123,7 +86,6 @@ impl<'tcx> MutVisitor<'tcx> for Replacer<'_, 'tcx> {
12386
// A move out of a projection of a copy is equivalent to a copy of the original
12487
// projection.
12588
&& !place.is_indirect_first_projection()
126-
&& !self.fully_moved.contains(place.local)
12789
{
12890
*operand = Operand::Copy(place);
12991
}

‎tests/mir-opt/copy-prop/borrowed_local.borrow_in_loop.CopyProp.panic-abort.diff‎

Lines changed: 8 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -46,12 +46,14 @@
4646
- StorageLive(_6);
4747
StorageLive(_7);
4848
_7 = copy (*_2);
49-
_6 = Not(move _7);
49+
- _6 = Not(move _7);
50+
+ _6 = Not(copy _7);
5051
StorageDead(_7);
5152
- StorageLive(_8);
5253
StorageLive(_9);
5354
_9 = copy (*_2);
54-
_8 = Not(move _9);
55+
- _8 = Not(move _9);
56+
+ _8 = Not(copy _9);
5557
StorageDead(_9);
5658
- StorageLive(_10);
5759
- _10 = copy _6;
@@ -62,7 +64,8 @@
6264
StorageLive(_12);
6365
_12 = &_1;
6466
_11 = &(*_12);
65-
_2 = move _11;
67+
- _2 = move _11;
68+
+ _2 = copy _11;
6669
StorageDead(_11);
6770
StorageDead(_12);
6871
StorageLive(_13);
@@ -71,8 +74,9 @@
7174
- StorageLive(_15);
7275
- _15 = copy _8;
7376
- _13 = Ne(move _14, move _15);
77+
- switchInt(move _13) -> [0: bb3, otherwise: bb2];
7478
+ _13 = Ne(copy _6, copy _8);
75-
switchInt(move _13) -> [0: bb3, otherwise: bb2];
79+
+ switchInt(copy _13) -> [0: bb3, otherwise: bb2];
7680
}
7781

7882
bb2: {

‎tests/mir-opt/copy-prop/borrowed_local.borrow_in_loop.CopyProp.panic-unwind.diff‎

Lines changed: 8 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -46,12 +46,14 @@
4646
- StorageLive(_6);
4747
StorageLive(_7);
4848
_7 = copy (*_2);
49-
_6 = Not(move _7);
49+
- _6 = Not(move _7);
50+
+ _6 = Not(copy _7);
5051
StorageDead(_7);
5152
- StorageLive(_8);
5253
StorageLive(_9);
5354
_9 = copy (*_2);
54-
_8 = Not(move _9);
55+
- _8 = Not(move _9);
56+
+ _8 = Not(copy _9);
5557
StorageDead(_9);
5658
- StorageLive(_10);
5759
- _10 = copy _6;
@@ -62,7 +64,8 @@
6264
StorageLive(_12);
6365
_12 = &_1;
6466
_11 = &(*_12);
65-
_2 = move _11;
67+
- _2 = move _11;
68+
+ _2 = copy _11;
6669
StorageDead(_11);
6770
StorageDead(_12);
6871
StorageLive(_13);
@@ -71,8 +74,9 @@
7174
- StorageLive(_15);
7275
- _15 = copy _8;
7376
- _13 = Ne(move _14, move _15);
77+
- switchInt(move _13) -> [0: bb3, otherwise: bb2];
7478
+ _13 = Ne(copy _6, copy _8);
75-
switchInt(move _13) -> [0: bb3, otherwise: bb2];
79+
+ switchInt(copy _13) -> [0: bb3, otherwise: bb2];
7680
}
7781

7882
bb2: {

‎tests/mir-opt/copy-prop/cycle.main.CopyProp.panic-abort.diff‎

Lines changed: 2 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -38,7 +38,8 @@
3838
StorageLive(_5);
3939
StorageLive(_6);
4040
_6 = copy _1;
41-
_5 = std::mem::drop::<i32>(move _6) -> [return: bb2, unwind unreachable];
41+
- _5 = std::mem::drop::<i32>(move _6) -> [return: bb2, unwind unreachable];
42+
+ _5 = std::mem::drop::<i32>(copy _6) -> [return: bb2, unwind unreachable];
4243
}
4344

4445
bb2: {

‎tests/mir-opt/copy-prop/cycle.main.CopyProp.panic-unwind.diff‎

Lines changed: 2 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -38,7 +38,8 @@
3838
StorageLive(_5);
3939
StorageLive(_6);
4040
_6 = copy _1;
41-
_5 = std::mem::drop::<i32>(move _6) -> [return: bb2, unwind continue];
41+
- _5 = std::mem::drop::<i32>(move _6) -> [return: bb2, unwind continue];
42+
+ _5 = std::mem::drop::<i32>(copy _6) -> [return: bb2, unwind continue];
4243
}
4344

4445
bb2: {

‎tests/mir-opt/copy-prop/dead_stores_79191.f.CopyProp.after.panic-abort.mir‎

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -16,7 +16,7 @@ fn f(_1: usize) -> usize {
1616
_1 = copy _2;
1717
StorageLive(_4);
1818
_4 = copy _1;
19-
_0 = id::<usize>(move _4) -> [return: bb1, unwind unreachable];
19+
_0 = id::<usize>(copy _4) -> [return: bb1, unwind unreachable];
2020
}
2121

2222
bb1: {

‎tests/mir-opt/copy-prop/dead_stores_79191.f.CopyProp.after.panic-unwind.mir‎

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -16,7 +16,7 @@ fn f(_1: usize) -> usize {
1616
_1 = copy _2;
1717
StorageLive(_4);
1818
_4 = copy _1;
19-
_0 = id::<usize>(move _4) -> [return: bb1, unwind continue];
19+
_0 = id::<usize>(copy _4) -> [return: bb1, unwind continue];
2020
}
2121

2222
bb1: {

‎tests/mir-opt/copy-prop/dead_stores_better.f.CopyProp.after.panic-abort.mir‎

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -16,7 +16,7 @@ fn f(_1: usize) -> usize {
1616
_1 = copy _2;
1717
StorageLive(_4);
1818
_4 = copy _1;
19-
_0 = id::<usize>(move _4) -> [return: bb1, unwind unreachable];
19+
_0 = id::<usize>(copy _4) -> [return: bb1, unwind unreachable];
2020
}
2121

2222
bb1: {

‎tests/mir-opt/copy-prop/dead_stores_better.f.CopyProp.after.panic-unwind.mir‎

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -16,7 +16,7 @@ fn f(_1: usize) -> usize {
1616
_1 = copy _2;
1717
StorageLive(_4);
1818
_4 = copy _1;
19-
_0 = id::<usize>(move _4) -> [return: bb1, unwind continue];
19+
_0 = id::<usize>(copy _4) -> [return: bb1, unwind continue];
2020
}
2121

2222
bb1: {

‎tests/mir-opt/copy-prop/issue_107511.main.CopyProp.panic-abort.diff‎

Lines changed: 17 additions & 9 deletions
Original file line numberDiff line numberDiff line change
@@ -46,22 +46,27 @@
4646
StorageLive(_6);
4747
StorageLive(_7);
4848
_7 = &_2;
49-
_6 = move _7 as &[i32] (PointerCoercion(Unsize, Implicit));
49+
- _6 = move _7 as &[i32] (PointerCoercion(Unsize, Implicit));
50+
+ _6 = copy _7 as &[i32] (PointerCoercion(Unsize, Implicit));
5051
StorageDead(_7);
51-
_5 = core::slice::<impl [i32]>::len(move _6) -> [return: bb1, unwind unreachable];
52+
- _5 = core::slice::<impl [i32]>::len(move _6) -> [return: bb1, unwind unreachable];
53+
+ _5 = core::slice::<impl [i32]>::len(copy _6) -> [return: bb1, unwind unreachable];
5254
}
5355

5456
bb1: {
5557
StorageDead(_6);
56-
_4 = std::ops::Range::<usize> { start: const 0_usize, end: move _5 };
58+
- _4 = std::ops::Range::<usize> { start: const 0_usize, end: move _5 };
59+
+ _4 = std::ops::Range::<usize> { start: const 0_usize, end: copy _5 };
5760
StorageDead(_5);
58-
_3 = <std::ops::Range<usize> as IntoIterator>::into_iter(move _4) -> [return: bb2, unwind unreachable];
61+
- _3 = <std::ops::Range<usize> as IntoIterator>::into_iter(move _4) -> [return: bb2, unwind unreachable];
62+
+ _3 = <std::ops::Range<usize> as IntoIterator>::into_iter(copy _4) -> [return: bb2, unwind unreachable];
5963
}
6064

6165
bb2: {
6266
StorageDead(_4);
6367
StorageLive(_8);
64-
_8 = move _3;
68+
- _8 = move _3;
69+
+ _8 = copy _3;
6570
goto -> bb3;
6671
}
6772

@@ -72,13 +77,15 @@
7277
StorageLive(_13);
7378
_13 = &mut _8;
7479
_12 = &mut (*_13);
75-
_11 = <std::ops::Range<usize> as Iterator>::next(move _12) -> [return: bb4, unwind unreachable];
80+
- _11 = <std::ops::Range<usize> as Iterator>::next(move _12) -> [return: bb4, unwind unreachable];
81+
+ _11 = <std::ops::Range<usize> as Iterator>::next(copy _12) -> [return: bb4, unwind unreachable];
7682
}
7783

7884
bb4: {
7985
StorageDead(_12);
8086
_14 = discriminant(_11);
81-
switchInt(move _14) -> [0: bb7, 1: bb6, otherwise: bb5];
87+
- switchInt(move _14) -> [0: bb7, 1: bb6, otherwise: bb5];
88+
+ switchInt(copy _14) -> [0: bb7, 1: bb6, otherwise: bb5];
8289
}
8390

8491
bb5: {
@@ -94,7 +101,7 @@
94101
- _19 = Lt(copy _18, const 4_usize);
95102
- assert(move _19, "index out of bounds: the length is {} but the index is {}", const 4_usize, copy _18) -> [success: bb8, unwind unreachable];
96103
+ _19 = Lt(copy _16, const 4_usize);
97-
+ assert(move _19, "index out of bounds: the length is {} but the index is {}", const 4_usize, copy _16) -> [success: bb8, unwind unreachable];
104+
+ assert(copy _19, "index out of bounds: the length is {} but the index is {}", const 4_usize, copy _16) -> [success: bb8, unwind unreachable];
98105
}
99106

100107
bb7: {
@@ -111,8 +118,9 @@
111118

112119
bb8: {
113120
- _17 = copy _2[_18];
121+
- _1 = Add(copy _1, move _17);
114122
+ _17 = copy _2[_16];
115-
_1 = Add(copy _1, move _17);
123+
+ _1 = Add(copy _1, copy _17);
116124
StorageDead(_17);
117125
- StorageDead(_18);
118126
- _10 = const ();

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