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Constify is_aligned via align_offset #102795

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Merged
merged 20 commits into from
Nov 19, 2022
Merged

Constify is_aligned via align_offset #102795

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f13c4f4
constify `exact_div` intrinsic
Oct 7, 2022
f770fec
unify inherent impls of `CompileTimeEvalContext`
Oct 20, 2022
211743b
make const `align_offset` useful
Oct 7, 2022
8cf6b16
add coretests for const `align_offset`
Oct 7, 2022
6f6320a
constify `pointer::is_aligned{,_to}`
Oct 7, 2022
2ef9a8a
add coretests for `is_aligned`
Oct 7, 2022
24e8806
mark `align_offset` as `#[must_use]`
Oct 20, 2022
a906f6c
don't call `align_offset` during const eval, ever
Oct 22, 2022
093c02e
document `is_aligned{,_to}`
Oct 22, 2022
df0bcfe
address more review comments
Oct 22, 2022
4696e89
Schrödinger's pointer
Oct 22, 2022
daccb8c
always use `align_offset` in `is_aligned_to` + add assembly test
Oct 23, 2022
8a60536
docs cleanup
Nov 9, 2022
60f352f
replace potential ICE with graceful error (`no_core` only)
Nov 11, 2022
8717455
fix assembly test on windows
Nov 11, 2022
9e5d497
fix const `align_offset` implementation
Nov 15, 2022
3d7e9c4
Revert "don't call `align_offset` during const eval, ever"
Nov 16, 2022
e90d15b
Update comment on pointer-to-usize transmute
lukas-code Nov 16, 2022
53c2ee8
fix assembly test on apple
Nov 16, 2022
c9c017d
update provenance test
Nov 18, 2022
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update provenance test 
* fix allocation alignment for 16bit platforms
* add edge case where `stride % align != 0` on pointers with provenance
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Lukas Markeffsky committed Nov 19, 2022
commit c9c017dfb55e375800c3e424311939a7ba3d4deb
48 changes: 46 additions & 2 deletions library/core/tests/ptr.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -564,9 +564,15 @@ fn align_offset_various_strides_const() {
#[cfg(not(bootstrap))]
fn align_offset_with_provenance_const() {
const {
let data = 42;
// On some platforms (e.g. msp430-none-elf), the alignment of `i32` is less than 4.
#[repr(align(4))]
struct AlignedI32(i32);

let ptr: *const i32 = &data;
let data = AlignedI32(42);

// `stride % align == 0` (usual case)

let ptr: *const i32 = &data.0;
assert!(ptr.align_offset(1) == 0);
assert!(ptr.align_offset(2) == 0);
assert!(ptr.align_offset(4) == 0);
Expand Down Expand Up @@ -621,6 +627,44 @@ fn align_offset_with_provenance_const() {
assert!(ptr3.align_offset(8) == usize::MAX);
assert!(ptr3.wrapping_byte_add(1).align_offset(1) == 0);
assert!(ptr3.wrapping_byte_add(1).align_offset(2) == usize::MAX);

// `stride % align != 0` (edge case)

let ptr4: *const [u8; 3] = ptr.cast();
assert!(ptr4.align_offset(1) == 0);
assert!(ptr4.align_offset(2) == 0);
assert!(ptr4.align_offset(4) == 0);
assert!(ptr4.align_offset(8) == usize::MAX);
assert!(ptr4.wrapping_byte_add(1).align_offset(1) == 0);
assert!(ptr4.wrapping_byte_add(1).align_offset(2) == 1);
assert!(ptr4.wrapping_byte_add(1).align_offset(4) == 1);
assert!(ptr4.wrapping_byte_add(1).align_offset(8) == usize::MAX);
assert!(ptr4.wrapping_byte_add(2).align_offset(1) == 0);
assert!(ptr4.wrapping_byte_add(2).align_offset(2) == 0);
assert!(ptr4.wrapping_byte_add(2).align_offset(4) == 2);
assert!(ptr4.wrapping_byte_add(2).align_offset(8) == usize::MAX);
assert!(ptr4.wrapping_byte_add(3).align_offset(1) == 0);
assert!(ptr4.wrapping_byte_add(3).align_offset(2) == 1);
assert!(ptr4.wrapping_byte_add(3).align_offset(4) == 3);
assert!(ptr4.wrapping_byte_add(3).align_offset(8) == usize::MAX);

let ptr5: *const [u8; 5] = ptr.cast();
assert!(ptr5.align_offset(1) == 0);
assert!(ptr5.align_offset(2) == 0);
assert!(ptr5.align_offset(4) == 0);
assert!(ptr5.align_offset(8) == usize::MAX);
assert!(ptr5.wrapping_byte_add(1).align_offset(1) == 0);
assert!(ptr5.wrapping_byte_add(1).align_offset(2) == 1);
assert!(ptr5.wrapping_byte_add(1).align_offset(4) == 3);
assert!(ptr5.wrapping_byte_add(1).align_offset(8) == usize::MAX);
assert!(ptr5.wrapping_byte_add(2).align_offset(1) == 0);
assert!(ptr5.wrapping_byte_add(2).align_offset(2) == 0);
assert!(ptr5.wrapping_byte_add(2).align_offset(4) == 2);
assert!(ptr5.wrapping_byte_add(2).align_offset(8) == usize::MAX);
assert!(ptr5.wrapping_byte_add(3).align_offset(1) == 0);
assert!(ptr5.wrapping_byte_add(3).align_offset(2) == 1);
assert!(ptr5.wrapping_byte_add(3).align_offset(4) == 1);
assert!(ptr5.wrapping_byte_add(3).align_offset(8) == usize::MAX);
}
}

Expand Down