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scottmcmscottmcm
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Make TrustedStep require Copy
All the implementations of the trait already are `Copy`, and this seems to be enough to simplify the implementations enough to make the MIR inliner willing to inline basics like `Range::next`.
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4 files changed

+142
-45
lines changed

4 files changed

+142
-45
lines changed

‎library/core/src/iter/range.rs‎

Lines changed: 13 additions & 12 deletions
Original file line numberDiff line numberDiff line change
@@ -619,25 +619,26 @@ impl<T: TrustedStep> RangeIteratorImpl for ops::Range<T> {
619619
#[inline]
620620
fn spec_next(&mut self) -> Option<T> {
621621
if self.start < self.end {
622+
let old = self.start;
622623
// SAFETY: just checked precondition
623-
let n = unsafe { Step::forward_unchecked(self.start.clone(), 1) };
624-
Some(mem::replace(&mut self.start, n))
624+
self.start = unsafe { Step::forward_unchecked(old, 1) };
625+
Some(old)
625626
} else {
626627
None
627628
}
628629
}
629630

630631
#[inline]
631632
fn spec_nth(&mut self, n: usize) -> Option<T> {
632-
if let Some(plus_n) = Step::forward_checked(self.start.clone(), n) {
633+
if let Some(plus_n) = Step::forward_checked(self.start, n) {
633634
if plus_n < self.end {
634635
// SAFETY: just checked precondition
635-
self.start = unsafe { Step::forward_unchecked(plus_n.clone(), 1) };
636+
self.start = unsafe { Step::forward_unchecked(plus_n, 1) };
636637
return Some(plus_n);
637638
}
638639
}
639640

640-
self.start = self.end.clone();
641+
self.start = self.end;
641642
None
642643
}
643644

@@ -655,7 +656,7 @@ impl<T: TrustedStep> RangeIteratorImpl for ops::Range<T> {
655656
// then steps_between either returns a bound to which we clamp or returns None which
656657
// together with the initial inequality implies more than usize::MAX steps.
657658
// Otherwise 0 is returned which always safe to use.
658-
self.start = unsafe { Step::forward_unchecked(self.start.clone(), taken) };
659+
self.start = unsafe { Step::forward_unchecked(self.start, taken) };
659660

660661
NonZeroUsize::new(n - taken).map_or(Ok(()), Err)
661662
}
@@ -664,24 +665,24 @@ impl<T: TrustedStep> RangeIteratorImpl for ops::Range<T> {
664665
fn spec_next_back(&mut self) -> Option<T> {
665666
if self.start < self.end {
666667
// SAFETY: just checked precondition
667-
self.end = unsafe { Step::backward_unchecked(self.end.clone(), 1) };
668-
Some(self.end.clone())
668+
self.end = unsafe { Step::backward_unchecked(self.end, 1) };
669+
Some(self.end)
669670
} else {
670671
None
671672
}
672673
}
673674

674675
#[inline]
675676
fn spec_nth_back(&mut self, n: usize) -> Option<T> {
676-
if let Some(minus_n) = Step::backward_checked(self.end.clone(), n) {
677+
if let Some(minus_n) = Step::backward_checked(self.end, n) {
677678
if minus_n > self.start {
678679
// SAFETY: just checked precondition
679680
self.end = unsafe { Step::backward_unchecked(minus_n, 1) };
680-
return Some(self.end.clone());
681+
return Some(self.end);
681682
}
682683
}
683684

684-
self.end = self.start.clone();
685+
self.end = self.start;
685686
None
686687
}
687688

@@ -696,7 +697,7 @@ impl<T: TrustedStep> RangeIteratorImpl for ops::Range<T> {
696697
let taken = available.min(n);
697698

698699
// SAFETY: same as the spec_advance_by() implementation
699-
self.end = unsafe { Step::backward_unchecked(self.end.clone(), taken) };
700+
self.end = unsafe { Step::backward_unchecked(self.end, taken) };
700701

701702
NonZeroUsize::new(n - taken).map_or(Ok(()), Err)
702703
}

‎library/core/src/iter/traits/marker.rs‎

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -86,4 +86,4 @@ pub unsafe trait InPlaceIterable: Iterator {}
8686
/// for details. Consumers are free to rely on the invariants in unsafe code.
8787
#[unstable(feature = "trusted_step", issue = "85731")]
8888
#[rustc_specialization_trait]
89-
pub unsafe trait TrustedStep: Step {}
89+
pub unsafe trait TrustedStep: Step + Copy {}

‎tests/mir-opt/pre-codegen/range_iter.forward_loop.PreCodegen.after.mir‎

Lines changed: 78 additions & 30 deletions
Original file line numberDiff line numberDiff line change
@@ -8,19 +8,32 @@ fn forward_loop(_1: u32, _2: u32, _3: impl Fn(u32)) -> () {
88
let mut _4: std::ops::Range<u32>; // in scope 0 at $DIR/range_iter.rs:+1:14: +1:24
99
let mut _5: std::ops::Range<u32>; // in scope 0 at $DIR/range_iter.rs:+1:14: +1:24
1010
let mut _6: &mut std::ops::Range<u32>; // in scope 0 at $DIR/range_iter.rs:+1:14: +1:24
11-
let mut _7: std::option::Option<u32>; // in scope 0 at $DIR/range_iter.rs:+1:14: +1:24
12-
let mut _8: isize; // in scope 0 at $DIR/range_iter.rs:+1:5: +3:6
13-
let mut _10: &impl Fn(u32); // in scope 0 at $DIR/range_iter.rs:+2:9: +2:10
14-
let mut _11: (u32,); // in scope 0 at $DIR/range_iter.rs:+2:9: +2:13
15-
let _12: (); // in scope 0 at $DIR/range_iter.rs:+1:14: +1:24
11+
let mut _10: std::option::Option<u32>; // in scope 0 at $DIR/range_iter.rs:+1:14: +1:24
12+
let mut _13: isize; // in scope 0 at $DIR/range_iter.rs:+1:5: +3:6
13+
let mut _15: &impl Fn(u32); // in scope 0 at $DIR/range_iter.rs:+2:9: +2:10
14+
let mut _16: (u32,); // in scope 0 at $DIR/range_iter.rs:+2:9: +2:13
15+
let _17: (); // in scope 0 at $DIR/range_iter.rs:+1:14: +1:24
1616
scope 1 {
1717
debug iter => _5; // in scope 1 at $DIR/range_iter.rs:+1:14: +1:24
18-
let _9: u32; // in scope 1 at $DIR/range_iter.rs:+1:9: +1:10
18+
let _14: u32; // in scope 1 at $DIR/range_iter.rs:+1:9: +1:10
1919
scope 2 {
20-
debug x => _9; // in scope 2 at $DIR/range_iter.rs:+1:9: +1:10
20+
debug x => _14; // in scope 2 at $DIR/range_iter.rs:+1:9: +1:10
2121
}
2222
scope 4 (inlined iter::range::<impl Iterator for std::ops::Range<u32>>::next) { // at $DIR/range_iter.rs:21:14: 21:24
2323
debug self => _6; // in scope 4 at $SRC_DIR/core/src/iter/range.rs:LL:COL
24+
scope 5 (inlined <std::ops::Range<u32> as iter::range::RangeIteratorImpl>::spec_next) { // at $SRC_DIR/core/src/iter/range.rs:LL:COL
25+
debug self => _6; // in scope 5 at $SRC_DIR/core/src/iter/range.rs:LL:COL
26+
let mut _7: &u32; // in scope 5 at $SRC_DIR/core/src/iter/range.rs:LL:COL
27+
let mut _8: &u32; // in scope 5 at $SRC_DIR/core/src/iter/range.rs:LL:COL
28+
let mut _9: bool; // in scope 5 at $SRC_DIR/core/src/iter/range.rs:LL:COL
29+
let _11: u32; // in scope 5 at $SRC_DIR/core/src/iter/range.rs:LL:COL
30+
let mut _12: u32; // in scope 5 at $SRC_DIR/core/src/iter/range.rs:LL:COL
31+
scope 6 {
32+
debug old => _11; // in scope 6 at $SRC_DIR/core/src/iter/range.rs:LL:COL
33+
scope 7 {
34+
}
35+
}
36+
}
2437
}
2538
}
2639
scope 3 (inlined <std::ops::Range<u32> as IntoIterator>::into_iter) { // at $DIR/range_iter.rs:21:14: 21:24
@@ -35,57 +48,92 @@ fn forward_loop(_1: u32, _2: u32, _3: impl Fn(u32)) -> () {
3548
}
3649

3750
bb1: {
38-
StorageLive(_7); // scope 1 at $DIR/range_iter.rs:+1:14: +1:24
51+
StorageLive(_10); // scope 1 at $DIR/range_iter.rs:+1:14: +1:24
3952
_6 = &mut _5; // scope 1 at $DIR/range_iter.rs:+1:14: +1:24
40-
_7 = <std::ops::Range<u32> as iter::range::RangeIteratorImpl>::spec_next(_6) -> [return: bb2, unwind: bb8]; // scope 4 at $SRC_DIR/core/src/iter/range.rs:LL:COL
53+
StorageLive(_11); // scope 4 at $SRC_DIR/core/src/iter/range.rs:LL:COL
54+
StorageLive(_9); // scope 5 at $SRC_DIR/core/src/iter/range.rs:LL:COL
55+
StorageLive(_7); // scope 5 at $SRC_DIR/core/src/iter/range.rs:LL:COL
56+
_7 = &((*_6).0: u32); // scope 5 at $SRC_DIR/core/src/iter/range.rs:LL:COL
57+
StorageLive(_8); // scope 5 at $SRC_DIR/core/src/iter/range.rs:LL:COL
58+
_8 = &((*_6).1: u32); // scope 5 at $SRC_DIR/core/src/iter/range.rs:LL:COL
59+
_9 = <u32 as PartialOrd>::lt(move _7, move _8) -> [return: bb2, unwind: bb12]; // scope 5 at $SRC_DIR/core/src/iter/range.rs:LL:COL
4160
// mir::Constant
4261
// + span: $SRC_DIR/core/src/iter/range.rs:LL:COL
43-
// + literal: Const { ty: for<'a> fn(&'a mut std::ops::Range<u32>) -> Option<<std::ops::Range<u32> as iter::range::RangeIteratorImpl>::Item> {<std::ops::Range<u32> as iter::range::RangeIteratorImpl>::spec_next}, val: Value(<ZST>) }
62+
// + literal: Const { ty: for<'a, 'b> fn(&'a u32, &'b u32) -> bool {<u32 as PartialOrd>::lt}, val: Value(<ZST>) }
4463
}
4564

4665
bb2: {
47-
_8 = discriminant(_7); // scope 1 at $DIR/range_iter.rs:+1:14: +1:24
48-
switchInt(move _8) -> [0: bb3, 1: bb5, otherwise: bb7]; // scope 1 at $DIR/range_iter.rs:+1:14: +1:24
66+
StorageDead(_8); // scope 5 at $SRC_DIR/core/src/iter/range.rs:LL:COL
67+
StorageDead(_7); // scope 5 at $SRC_DIR/core/src/iter/range.rs:LL:COL
68+
switchInt(move _9) -> [0: bb3, otherwise: bb4]; // scope 5 at $SRC_DIR/core/src/iter/range.rs:LL:COL
4969
}
5070

5171
bb3: {
52-
StorageDead(_7); // scope 1 at $DIR/range_iter.rs:+3:5: +3:6
53-
StorageDead(_5); // scope 0 at $DIR/range_iter.rs:+3:5: +3:6
54-
drop(_3) -> bb4; // scope 0 at $DIR/range_iter.rs:+4:1: +4:2
72+
_10 = Option::<u32>::None; // scope 5 at $SRC_DIR/core/src/iter/range.rs:LL:COL
73+
goto -> bb6; // scope 5 at $SRC_DIR/core/src/iter/range.rs:LL:COL
5574
}
5675

5776
bb4: {
58-
return; // scope 0 at $DIR/range_iter.rs:+4:2: +4:2
77+
_11 = ((*_6).0: u32); // scope 5 at $SRC_DIR/core/src/iter/range.rs:LL:COL
78+
StorageLive(_12); // scope 6 at $SRC_DIR/core/src/iter/range.rs:LL:COL
79+
_12 = <u32 as Step>::forward_unchecked(_11, const 1_usize) -> [return: bb5, unwind: bb12]; // scope 7 at $SRC_DIR/core/src/iter/range.rs:LL:COL
80+
// mir::Constant
81+
// + span: $SRC_DIR/core/src/iter/range.rs:LL:COL
82+
// + literal: Const { ty: unsafe fn(u32, usize) -> u32 {<u32 as Step>::forward_unchecked}, val: Value(<ZST>) }
5983
}
6084

6185
bb5: {
62-
_9 = ((_7 as Some).0: u32); // scope 1 at $DIR/range_iter.rs:+1:9: +1:10
63-
StorageLive(_10); // scope 2 at $DIR/range_iter.rs:+2:9: +2:10
64-
_10 = &_3; // scope 2 at $DIR/range_iter.rs:+2:9: +2:10
65-
StorageLive(_11); // scope 2 at $DIR/range_iter.rs:+2:9: +2:13
66-
_11 = (_9,); // scope 2 at $DIR/range_iter.rs:+2:9: +2:13
67-
_12 = <impl Fn(u32) as Fn<(u32,)>>::call(move _10, move _11) -> [return: bb6, unwind: bb8]; // scope 2 at $DIR/range_iter.rs:+2:9: +2:13
86+
((*_6).0: u32) = move _12; // scope 6 at $SRC_DIR/core/src/iter/range.rs:LL:COL
87+
StorageDead(_12); // scope 6 at $SRC_DIR/core/src/iter/range.rs:LL:COL
88+
_10 = Option::<u32>::Some(_11); // scope 6 at $SRC_DIR/core/src/iter/range.rs:LL:COL
89+
goto -> bb6; // scope 5 at $SRC_DIR/core/src/iter/range.rs:LL:COL
90+
}
91+
92+
bb6: {
93+
StorageDead(_9); // scope 5 at $SRC_DIR/core/src/iter/range.rs:LL:COL
94+
StorageDead(_11); // scope 4 at $SRC_DIR/core/src/iter/range.rs:LL:COL
95+
_13 = discriminant(_10); // scope 1 at $DIR/range_iter.rs:+1:14: +1:24
96+
switchInt(move _13) -> [0: bb7, 1: bb9, otherwise: bb11]; // scope 1 at $DIR/range_iter.rs:+1:14: +1:24
97+
}
98+
99+
bb7: {
100+
StorageDead(_10); // scope 1 at $DIR/range_iter.rs:+3:5: +3:6
101+
StorageDead(_5); // scope 0 at $DIR/range_iter.rs:+3:5: +3:6
102+
drop(_3) -> bb8; // scope 0 at $DIR/range_iter.rs:+4:1: +4:2
103+
}
104+
105+
bb8: {
106+
return; // scope 0 at $DIR/range_iter.rs:+4:2: +4:2
107+
}
108+
109+
bb9: {
110+
_14 = ((_10 as Some).0: u32); // scope 1 at $DIR/range_iter.rs:+1:9: +1:10
111+
StorageLive(_15); // scope 2 at $DIR/range_iter.rs:+2:9: +2:10
112+
_15 = &_3; // scope 2 at $DIR/range_iter.rs:+2:9: +2:10
113+
StorageLive(_16); // scope 2 at $DIR/range_iter.rs:+2:9: +2:13
114+
_16 = (_14,); // scope 2 at $DIR/range_iter.rs:+2:9: +2:13
115+
_17 = <impl Fn(u32) as Fn<(u32,)>>::call(move _15, move _16) -> [return: bb10, unwind: bb12]; // scope 2 at $DIR/range_iter.rs:+2:9: +2:13
68116
// mir::Constant
69117
// + span: $DIR/range_iter.rs:22:9: 22:10
70118
// + literal: Const { ty: for<'a> extern "rust-call" fn(&'a impl Fn(u32), (u32,)) -> <impl Fn(u32) as FnOnce<(u32,)>>::Output {<impl Fn(u32) as Fn<(u32,)>>::call}, val: Value(<ZST>) }
71119
}
72120

73-
bb6: {
74-
StorageDead(_11); // scope 2 at $DIR/range_iter.rs:+2:12: +2:13
75-
StorageDead(_10); // scope 2 at $DIR/range_iter.rs:+2:12: +2:13
76-
StorageDead(_7); // scope 1 at $DIR/range_iter.rs:+3:5: +3:6
121+
bb10: {
122+
StorageDead(_16); // scope 2 at $DIR/range_iter.rs:+2:12: +2:13
123+
StorageDead(_15); // scope 2 at $DIR/range_iter.rs:+2:12: +2:13
124+
StorageDead(_10); // scope 1 at $DIR/range_iter.rs:+3:5: +3:6
77125
goto -> bb1; // scope 1 at $DIR/range_iter.rs:+1:5: +3:6
78126
}
79127

80-
bb7: {
128+
bb11: {
81129
unreachable; // scope 1 at $DIR/range_iter.rs:+1:14: +1:24
82130
}
83131

84-
bb8 (cleanup): {
85-
drop(_3) -> [return: bb9, unwind terminate]; // scope 0 at $DIR/range_iter.rs:+4:1: +4:2
132+
bb12 (cleanup): {
133+
drop(_3) -> [return: bb13, unwind terminate]; // scope 0 at $DIR/range_iter.rs:+4:1: +4:2
86134
}
87135

88-
bb9 (cleanup): {
136+
bb13 (cleanup): {
89137
resume; // scope 0 at $DIR/range_iter.rs:+0:1: +4:2
90138
}
91139
}

‎tests/mir-opt/pre-codegen/range_iter.range_iter_next.PreCodegen.after.mir‎

Lines changed: 50 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -5,16 +5,64 @@ fn range_iter_next(_1: &mut std::ops::Range<u32>) -> Option<u32> {
55
let mut _0: std::option::Option<u32>; // return place in scope 0 at $DIR/range_iter.rs:+0:48: +0:59
66
scope 1 (inlined iter::range::<impl Iterator for std::ops::Range<u32>>::next) { // at $DIR/range_iter.rs:11:8: 11:14
77
debug self => _1; // in scope 1 at $SRC_DIR/core/src/iter/range.rs:LL:COL
8+
scope 2 (inlined <std::ops::Range<u32> as iter::range::RangeIteratorImpl>::spec_next) { // at $SRC_DIR/core/src/iter/range.rs:LL:COL
9+
debug self => _1; // in scope 2 at $SRC_DIR/core/src/iter/range.rs:LL:COL
10+
let mut _2: &u32; // in scope 2 at $SRC_DIR/core/src/iter/range.rs:LL:COL
11+
let mut _3: &u32; // in scope 2 at $SRC_DIR/core/src/iter/range.rs:LL:COL
12+
let mut _4: bool; // in scope 2 at $SRC_DIR/core/src/iter/range.rs:LL:COL
13+
let _5: u32; // in scope 2 at $SRC_DIR/core/src/iter/range.rs:LL:COL
14+
let mut _6: u32; // in scope 2 at $SRC_DIR/core/src/iter/range.rs:LL:COL
15+
scope 3 {
16+
debug old => _5; // in scope 3 at $SRC_DIR/core/src/iter/range.rs:LL:COL
17+
scope 4 {
18+
}
19+
}
20+
}
821
}
922

1023
bb0: {
11-
_0 = <std::ops::Range<u32> as iter::range::RangeIteratorImpl>::spec_next(_1) -> bb1; // scope 1 at $SRC_DIR/core/src/iter/range.rs:LL:COL
24+
StorageLive(_5); // scope 1 at $SRC_DIR/core/src/iter/range.rs:LL:COL
25+
StorageLive(_4); // scope 2 at $SRC_DIR/core/src/iter/range.rs:LL:COL
26+
StorageLive(_2); // scope 2 at $SRC_DIR/core/src/iter/range.rs:LL:COL
27+
_2 = &((*_1).0: u32); // scope 2 at $SRC_DIR/core/src/iter/range.rs:LL:COL
28+
StorageLive(_3); // scope 2 at $SRC_DIR/core/src/iter/range.rs:LL:COL
29+
_3 = &((*_1).1: u32); // scope 2 at $SRC_DIR/core/src/iter/range.rs:LL:COL
30+
_4 = <u32 as PartialOrd>::lt(move _2, move _3) -> bb1; // scope 2 at $SRC_DIR/core/src/iter/range.rs:LL:COL
1231
// mir::Constant
1332
// + span: $SRC_DIR/core/src/iter/range.rs:LL:COL
14-
// + literal: Const { ty: for<'a> fn(&'a mut std::ops::Range<u32>) -> Option<<std::ops::Range<u32> as iter::range::RangeIteratorImpl>::Item> {<std::ops::Range<u32> as iter::range::RangeIteratorImpl>::spec_next}, val: Value(<ZST>) }
33+
// + literal: Const { ty: for<'a, 'b> fn(&'a u32, &'b u32) -> bool {<u32 as PartialOrd>::lt}, val: Value(<ZST>) }
1534
}
1635

1736
bb1: {
37+
StorageDead(_3); // scope 2 at $SRC_DIR/core/src/iter/range.rs:LL:COL
38+
StorageDead(_2); // scope 2 at $SRC_DIR/core/src/iter/range.rs:LL:COL
39+
switchInt(move _4) -> [0: bb2, otherwise: bb3]; // scope 2 at $SRC_DIR/core/src/iter/range.rs:LL:COL
40+
}
41+
42+
bb2: {
43+
_0 = Option::<u32>::None; // scope 2 at $SRC_DIR/core/src/iter/range.rs:LL:COL
44+
goto -> bb5; // scope 2 at $SRC_DIR/core/src/iter/range.rs:LL:COL
45+
}
46+
47+
bb3: {
48+
_5 = ((*_1).0: u32); // scope 2 at $SRC_DIR/core/src/iter/range.rs:LL:COL
49+
StorageLive(_6); // scope 3 at $SRC_DIR/core/src/iter/range.rs:LL:COL
50+
_6 = <u32 as Step>::forward_unchecked(_5, const 1_usize) -> bb4; // scope 4 at $SRC_DIR/core/src/iter/range.rs:LL:COL
51+
// mir::Constant
52+
// + span: $SRC_DIR/core/src/iter/range.rs:LL:COL
53+
// + literal: Const { ty: unsafe fn(u32, usize) -> u32 {<u32 as Step>::forward_unchecked}, val: Value(<ZST>) }
54+
}
55+
56+
bb4: {
57+
((*_1).0: u32) = move _6; // scope 3 at $SRC_DIR/core/src/iter/range.rs:LL:COL
58+
StorageDead(_6); // scope 3 at $SRC_DIR/core/src/iter/range.rs:LL:COL
59+
_0 = Option::<u32>::Some(_5); // scope 3 at $SRC_DIR/core/src/iter/range.rs:LL:COL
60+
goto -> bb5; // scope 2 at $SRC_DIR/core/src/iter/range.rs:LL:COL
61+
}
62+
63+
bb5: {
64+
StorageDead(_4); // scope 2 at $SRC_DIR/core/src/iter/range.rs:LL:COL
65+
StorageDead(_5); // scope 1 at $SRC_DIR/core/src/iter/range.rs:LL:COL
1866
return; // scope 0 at $DIR/range_iter.rs:+2:2: +2:2
1967
}
2068
}

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