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matthiaskrgrmatthiaskrgr
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Rollup merge of #119052 - cjgillot:gvn-index-overflow, r=compiler-errors
Avoid overflow in GVN constant indexing. Fixes #118992 Fixes #119008
2 parents 677bb6c + 8022057 commit 39fe059

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4 files changed

+229
-5
lines changed

4 files changed

+229
-5
lines changed

‎compiler/rustc_mir_transform/src/gvn.rs

+3-5
Original file line numberDiff line numberDiff line change
@@ -644,12 +644,10 @@ impl<'body, 'tcx> VnState<'body, 'tcx> {
644644
{
645645
if let Some(offset) = self.evaluated[idx].as_ref()
646646
&& let Ok(offset) = self.ecx.read_target_usize(offset)
647+
&& let Some(min_length) = offset.checked_add(1)
647648
{
648-
projection.to_mut()[i] = ProjectionElem::ConstantIndex {
649-
offset,
650-
min_length: offset + 1,
651-
from_end: false,
652-
};
649+
projection.to_mut()[i] =
650+
ProjectionElem::ConstantIndex { offset, min_length, from_end: false };
653651
} else if let Some(new_idx) = self.try_as_local(idx, location) {
654652
projection.to_mut()[i] = ProjectionElem::Index(new_idx);
655653
self.reused_locals.insert(new_idx);

‎tests/mir-opt/gvn.constant_index_overflow.GVN.panic-abort.diff

+104
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,104 @@
1+
- // MIR for `constant_index_overflow` before GVN
2+
+ // MIR for `constant_index_overflow` after GVN
3+
4+
fn constant_index_overflow(_1: &[T]) -> () {
5+
debug x => _1;
6+
let mut _0: ();
7+
let _2: usize;
8+
let mut _4: bool;
9+
let mut _5: usize;
10+
let mut _6: usize;
11+
let mut _7: &[T];
12+
let _8: usize;
13+
let mut _9: usize;
14+
let mut _10: bool;
15+
let _11: usize;
16+
let mut _12: usize;
17+
let mut _13: bool;
18+
let mut _14: T;
19+
scope 1 {
20+
debug a => _2;
21+
let _3: T;
22+
scope 2 {
23+
debug b => _3;
24+
}
25+
}
26+
27+
bb0: {
28+
- StorageLive(_2);
29+
- _2 = const _ as usize (IntToInt);
30+
+ nop;
31+
+ _2 = const usize::MAX;
32+
StorageLive(_3);
33+
StorageLive(_4);
34+
StorageLive(_5);
35+
- _5 = _2;
36+
+ _5 = const usize::MAX;
37+
StorageLive(_6);
38+
StorageLive(_7);
39+
_7 = &(*_1);
40+
_6 = core::slice::<impl [T]>::len(move _7) -> [return: bb1, unwind unreachable];
41+
}
42+
43+
bb1: {
44+
StorageDead(_7);
45+
- _4 = Lt(move _5, move _6);
46+
+ _4 = Lt(const usize::MAX, move _6);
47+
switchInt(move _4) -> [0: bb4, otherwise: bb2];
48+
}
49+
50+
bb2: {
51+
StorageDead(_6);
52+
StorageDead(_5);
53+
StorageLive(_8);
54+
- _8 = _2;
55+
+ _8 = const usize::MAX;
56+
_9 = Len((*_1));
57+
- _10 = Lt(_8, _9);
58+
- assert(move _10, "index out of bounds: the length is {} but the index is {}", move _9, _8) -> [success: bb3, unwind unreachable];
59+
+ _10 = Lt(const usize::MAX, _9);
60+
+ assert(move _10, "index out of bounds: the length is {} but the index is {}", move _9, const usize::MAX) -> [success: bb3, unwind unreachable];
61+
}
62+
63+
bb3: {
64+
- _3 = (*_1)[_8];
65+
+ _3 = (*_1)[_2];
66+
StorageDead(_8);
67+
goto -> bb6;
68+
}
69+
70+
bb4: {
71+
StorageDead(_6);
72+
StorageDead(_5);
73+
StorageLive(_11);
74+
_11 = const 0_usize;
75+
_12 = Len((*_1));
76+
- _13 = Lt(_11, _12);
77+
- assert(move _13, "index out of bounds: the length is {} but the index is {}", move _12, _11) -> [success: bb5, unwind unreachable];
78+
+ _13 = Lt(const 0_usize, _12);
79+
+ assert(move _13, "index out of bounds: the length is {} but the index is {}", move _12, const 0_usize) -> [success: bb5, unwind unreachable];
80+
}
81+
82+
bb5: {
83+
- _3 = (*_1)[_11];
84+
+ _3 = (*_1)[0 of 1];
85+
StorageDead(_11);
86+
goto -> bb6;
87+
}
88+
89+
bb6: {
90+
StorageDead(_4);
91+
StorageLive(_14);
92+
_14 = _3;
93+
_0 = opaque::<T>(move _14) -> [return: bb7, unwind unreachable];
94+
}
95+
96+
bb7: {
97+
StorageDead(_14);
98+
StorageDead(_3);
99+
- StorageDead(_2);
100+
+ nop;
101+
return;
102+
}
103+
}
104+

‎tests/mir-opt/gvn.constant_index_overflow.GVN.panic-unwind.diff

+104
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,104 @@
1+
- // MIR for `constant_index_overflow` before GVN
2+
+ // MIR for `constant_index_overflow` after GVN
3+
4+
fn constant_index_overflow(_1: &[T]) -> () {
5+
debug x => _1;
6+
let mut _0: ();
7+
let _2: usize;
8+
let mut _4: bool;
9+
let mut _5: usize;
10+
let mut _6: usize;
11+
let mut _7: &[T];
12+
let _8: usize;
13+
let mut _9: usize;
14+
let mut _10: bool;
15+
let _11: usize;
16+
let mut _12: usize;
17+
let mut _13: bool;
18+
let mut _14: T;
19+
scope 1 {
20+
debug a => _2;
21+
let _3: T;
22+
scope 2 {
23+
debug b => _3;
24+
}
25+
}
26+
27+
bb0: {
28+
- StorageLive(_2);
29+
- _2 = const _ as usize (IntToInt);
30+
+ nop;
31+
+ _2 = const usize::MAX;
32+
StorageLive(_3);
33+
StorageLive(_4);
34+
StorageLive(_5);
35+
- _5 = _2;
36+
+ _5 = const usize::MAX;
37+
StorageLive(_6);
38+
StorageLive(_7);
39+
_7 = &(*_1);
40+
_6 = core::slice::<impl [T]>::len(move _7) -> [return: bb1, unwind continue];
41+
}
42+
43+
bb1: {
44+
StorageDead(_7);
45+
- _4 = Lt(move _5, move _6);
46+
+ _4 = Lt(const usize::MAX, move _6);
47+
switchInt(move _4) -> [0: bb4, otherwise: bb2];
48+
}
49+
50+
bb2: {
51+
StorageDead(_6);
52+
StorageDead(_5);
53+
StorageLive(_8);
54+
- _8 = _2;
55+
+ _8 = const usize::MAX;
56+
_9 = Len((*_1));
57+
- _10 = Lt(_8, _9);
58+
- assert(move _10, "index out of bounds: the length is {} but the index is {}", move _9, _8) -> [success: bb3, unwind continue];
59+
+ _10 = Lt(const usize::MAX, _9);
60+
+ assert(move _10, "index out of bounds: the length is {} but the index is {}", move _9, const usize::MAX) -> [success: bb3, unwind continue];
61+
}
62+
63+
bb3: {
64+
- _3 = (*_1)[_8];
65+
+ _3 = (*_1)[_2];
66+
StorageDead(_8);
67+
goto -> bb6;
68+
}
69+
70+
bb4: {
71+
StorageDead(_6);
72+
StorageDead(_5);
73+
StorageLive(_11);
74+
_11 = const 0_usize;
75+
_12 = Len((*_1));
76+
- _13 = Lt(_11, _12);
77+
- assert(move _13, "index out of bounds: the length is {} but the index is {}", move _12, _11) -> [success: bb5, unwind continue];
78+
+ _13 = Lt(const 0_usize, _12);
79+
+ assert(move _13, "index out of bounds: the length is {} but the index is {}", move _12, const 0_usize) -> [success: bb5, unwind continue];
80+
}
81+
82+
bb5: {
83+
- _3 = (*_1)[_11];
84+
+ _3 = (*_1)[0 of 1];
85+
StorageDead(_11);
86+
goto -> bb6;
87+
}
88+
89+
bb6: {
90+
StorageDead(_4);
91+
StorageLive(_14);
92+
_14 = _3;
93+
_0 = opaque::<T>(move _14) -> [return: bb7, unwind continue];
94+
}
95+
96+
bb7: {
97+
StorageDead(_14);
98+
StorageDead(_3);
99+
- StorageDead(_2);
100+
+ nop;
101+
return;
102+
}
103+
}
104+

‎tests/mir-opt/gvn.rs

+18
Original file line numberDiff line numberDiff line change
@@ -609,6 +609,22 @@ fn indirect_static() {
609609
})
610610
}
611611

612+
/// Verify that having constant index `u64::MAX` does not yield to an overflow in rustc.
613+
fn constant_index_overflow<T: Copy>(x: &[T]) {
614+
// CHECK-LABEL: fn constant_index_overflow(
615+
// CHECK: debug a => [[a:_.*]];
616+
// CHECK: debug b => [[b:_.*]];
617+
// CHECK: [[a]] = const usize::MAX;
618+
// CHECK-NOT: = (*_1)[{{.*}} of 0];
619+
// CHECK: [[b]] = (*_1)[[[a]]];
620+
// CHECK-NOT: = (*_1)[{{.*}} of 0];
621+
// CHECK: [[b]] = (*_1)[0 of 1];
622+
// CHECK-NOT: = (*_1)[{{.*}} of 0];
623+
let a = u64::MAX as usize;
624+
let b = if a < x.len() { x[a] } else { x[0] };
625+
opaque(b)
626+
}
627+
612628
fn main() {
613629
subexpression_elimination(2, 4, 5);
614630
wrap_unwrap(5);
@@ -627,6 +643,7 @@ fn main() {
627643
repeat();
628644
fn_pointers();
629645
indirect_static();
646+
constant_index_overflow(&[5, 3]);
630647
}
631648

632649
#[inline(never)]
@@ -653,3 +670,4 @@ fn identity<T>(x: T) -> T {
653670
// EMIT_MIR gvn.repeat.GVN.diff
654671
// EMIT_MIR gvn.fn_pointers.GVN.diff
655672
// EMIT_MIR gvn.indirect_static.GVN.diff
673+
// EMIT_MIR gvn.constant_index_overflow.GVN.diff

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