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Update ptr::Alignment to go through transmuting

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This commit is contained in:
Scott McMurray 2026-01-25 17:05:09 -08:00
parent 3a33ab0595
commit 929e280973
6 changed files with 54 additions and 52 deletions
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5
library/core/src/ptr/alignment.rs
View file

@ -166,7 +166,10 @@ impl Alignment {
#[unstable(feature = "ptr_alignment_type", issue = "102070")]
#[inline]
pub const fn as_usize(self) -> usize {
self.0 as usize
// Going through `as_nonzero` helps this be more clearly the inverse of
// `new_unchecked`, letting MIR optimizations fold it away.
self.as_nonzero().get()
}
/// Returns the alignment as a <code>[NonZero]<[usize]></code>.

24
tests/mir-opt/pre-codegen/drop_boxed_slice.generic_in_place.PreCodegen.after.32bit.panic-abort.mir
View file

@ -8,9 +8,8 @@ fn generic_in_place(_1: *mut Box<[T]>) -> () {
let _2: std::ptr::NonNull<[T]>;
let mut _3: *mut [T];
let mut _4: *const [T];
let _11: ();
let _10: ();
scope 3 {
let _8: std::ptr::alignment::AlignmentEnum;
scope 4 {
scope 17 (inlined Layout::size) {
}
@ -27,17 +26,21 @@ fn generic_in_place(_1: *mut Box<[T]>) -> () {
scope 23 (inlined <std::alloc::Global as Allocator>::deallocate) {
scope 24 (inlined std::alloc::Global::deallocate_impl) {
scope 25 (inlined std::alloc::Global::deallocate_impl_runtime) {
let mut _9: *mut u8;
let mut _8: *mut u8;
scope 26 (inlined Layout::size) {
}
scope 27 (inlined NonNull::<u8>::as_ptr) {
}
scope 28 (inlined std::alloc::dealloc) {
let mut _10: usize;
let mut _9: usize;
scope 29 (inlined Layout::size) {
}
scope 30 (inlined Layout::align) {
scope 31 (inlined std::ptr::Alignment::as_usize) {
scope 32 (inlined std::ptr::Alignment::as_nonzero) {
}
scope 33 (inlined NonZero::<usize>::get) {
}
}
}
}
@ -82,7 +85,6 @@ fn generic_in_place(_1: *mut Box<[T]>) -> () {
StorageLive(_4);
_3 = copy _2 as *mut [T] (Transmute);
_4 = copy _2 as *const [T] (Transmute);
StorageLive(_7);
_5 = std::intrinsics::size_of_val::<[T]>(move _4) -> [return: bb1, unwind unreachable];
}
@ -91,23 +93,21 @@ fn generic_in_place(_1: *mut Box<[T]>) -> () {
_6 = const <T as std::mem::SizedTypeProperties>::ALIGN;
_7 = copy _6 as std::ptr::Alignment (Transmute);
StorageDead(_6);
_8 = copy (_7.0: std::ptr::alignment::AlignmentEnum);
StorageDead(_7);
StorageDead(_4);
switchInt(copy _5) -> [0: bb4, otherwise: bb2];
}
bb2: {
StorageLive(_8);
_8 = copy _3 as *mut u8 (PtrToPtr);
StorageLive(_9);
_9 = copy _3 as *mut u8 (PtrToPtr);
StorageLive(_10);
_10 = discriminant(_8);
_11 = alloc::alloc::__rust_dealloc(move _9, move _5, move _10) -> [return: bb3, unwind unreachable];
_9 = copy _7 as usize (Transmute);
_10 = alloc::alloc::__rust_dealloc(move _8, move _5, move _9) -> [return: bb3, unwind unreachable];
}
bb3: {
StorageDead(_10);
StorageDead(_9);
StorageDead(_8);
goto -> bb4;
}

24
tests/mir-opt/pre-codegen/drop_boxed_slice.generic_in_place.PreCodegen.after.32bit.panic-unwind.mir
View file

@ -8,9 +8,8 @@ fn generic_in_place(_1: *mut Box<[T]>) -> () {
let _2: std::ptr::NonNull<[T]>;
let mut _3: *mut [T];
let mut _4: *const [T];
let _11: ();
let _10: ();
scope 3 {
let _8: std::ptr::alignment::AlignmentEnum;
scope 4 {
scope 17 (inlined Layout::size) {
}
@ -27,17 +26,21 @@ fn generic_in_place(_1: *mut Box<[T]>) -> () {
scope 23 (inlined <std::alloc::Global as Allocator>::deallocate) {
scope 24 (inlined std::alloc::Global::deallocate_impl) {
scope 25 (inlined std::alloc::Global::deallocate_impl_runtime) {
let mut _9: *mut u8;
let mut _8: *mut u8;
scope 26 (inlined Layout::size) {
}
scope 27 (inlined NonNull::<u8>::as_ptr) {
}
scope 28 (inlined std::alloc::dealloc) {
let mut _10: usize;
let mut _9: usize;
scope 29 (inlined Layout::size) {
}
scope 30 (inlined Layout::align) {
scope 31 (inlined std::ptr::Alignment::as_usize) {
scope 32 (inlined std::ptr::Alignment::as_nonzero) {
}
scope 33 (inlined NonZero::<usize>::get) {
}
}
}
}
@ -82,7 +85,6 @@ fn generic_in_place(_1: *mut Box<[T]>) -> () {
StorageLive(_4);
_3 = copy _2 as *mut [T] (Transmute);
_4 = copy _2 as *const [T] (Transmute);
StorageLive(_7);
_5 = std::intrinsics::size_of_val::<[T]>(move _4) -> [return: bb1, unwind unreachable];
}
@ -91,23 +93,21 @@ fn generic_in_place(_1: *mut Box<[T]>) -> () {
_6 = const <T as std::mem::SizedTypeProperties>::ALIGN;
_7 = copy _6 as std::ptr::Alignment (Transmute);
StorageDead(_6);
_8 = copy (_7.0: std::ptr::alignment::AlignmentEnum);
StorageDead(_7);
StorageDead(_4);
switchInt(copy _5) -> [0: bb4, otherwise: bb2];
}
bb2: {
StorageLive(_8);
_8 = copy _3 as *mut u8 (PtrToPtr);
StorageLive(_9);
_9 = copy _3 as *mut u8 (PtrToPtr);
StorageLive(_10);
_10 = discriminant(_8);
_11 = alloc::alloc::__rust_dealloc(move _9, move _5, move _10) -> [return: bb3, unwind unreachable];
_9 = copy _7 as usize (Transmute);
_10 = alloc::alloc::__rust_dealloc(move _8, move _5, move _9) -> [return: bb3, unwind unreachable];
}
bb3: {
StorageDead(_10);
StorageDead(_9);
StorageDead(_8);
goto -> bb4;
}

24
tests/mir-opt/pre-codegen/drop_boxed_slice.generic_in_place.PreCodegen.after.64bit.panic-abort.mir
View file

@ -8,9 +8,8 @@ fn generic_in_place(_1: *mut Box<[T]>) -> () {
let _2: std::ptr::NonNull<[T]>;
let mut _3: *mut [T];
let mut _4: *const [T];
let _11: ();
let _10: ();
scope 3 {
let _8: std::ptr::alignment::AlignmentEnum;
scope 4 {
scope 17 (inlined Layout::size) {
}
@ -27,17 +26,21 @@ fn generic_in_place(_1: *mut Box<[T]>) -> () {
scope 23 (inlined <std::alloc::Global as Allocator>::deallocate) {
scope 24 (inlined std::alloc::Global::deallocate_impl) {
scope 25 (inlined std::alloc::Global::deallocate_impl_runtime) {
let mut _9: *mut u8;
let mut _8: *mut u8;
scope 26 (inlined Layout::size) {
}
scope 27 (inlined NonNull::<u8>::as_ptr) {
}
scope 28 (inlined std::alloc::dealloc) {
let mut _10: usize;
let mut _9: usize;
scope 29 (inlined Layout::size) {
}
scope 30 (inlined Layout::align) {
scope 31 (inlined std::ptr::Alignment::as_usize) {
scope 32 (inlined std::ptr::Alignment::as_nonzero) {
}
scope 33 (inlined NonZero::<usize>::get) {
}
}
}
}
@ -82,7 +85,6 @@ fn generic_in_place(_1: *mut Box<[T]>) -> () {
StorageLive(_4);
_3 = copy _2 as *mut [T] (Transmute);
_4 = copy _2 as *const [T] (Transmute);
StorageLive(_7);
_5 = std::intrinsics::size_of_val::<[T]>(move _4) -> [return: bb1, unwind unreachable];
}
@ -91,23 +93,21 @@ fn generic_in_place(_1: *mut Box<[T]>) -> () {
_6 = const <T as std::mem::SizedTypeProperties>::ALIGN;
_7 = copy _6 as std::ptr::Alignment (Transmute);
StorageDead(_6);
_8 = copy (_7.0: std::ptr::alignment::AlignmentEnum);
StorageDead(_7);
StorageDead(_4);
switchInt(copy _5) -> [0: bb4, otherwise: bb2];
}
bb2: {
StorageLive(_8);
_8 = copy _3 as *mut u8 (PtrToPtr);
StorageLive(_9);
_9 = copy _3 as *mut u8 (PtrToPtr);
StorageLive(_10);
_10 = discriminant(_8);
_11 = alloc::alloc::__rust_dealloc(move _9, move _5, move _10) -> [return: bb3, unwind unreachable];
_9 = copy _7 as usize (Transmute);
_10 = alloc::alloc::__rust_dealloc(move _8, move _5, move _9) -> [return: bb3, unwind unreachable];
}
bb3: {
StorageDead(_10);
StorageDead(_9);
StorageDead(_8);
goto -> bb4;
}

24
tests/mir-opt/pre-codegen/drop_boxed_slice.generic_in_place.PreCodegen.after.64bit.panic-unwind.mir
View file

@ -8,9 +8,8 @@ fn generic_in_place(_1: *mut Box<[T]>) -> () {
let _2: std::ptr::NonNull<[T]>;
let mut _3: *mut [T];
let mut _4: *const [T];
let _11: ();
let _10: ();
scope 3 {
let _8: std::ptr::alignment::AlignmentEnum;
scope 4 {
scope 17 (inlined Layout::size) {
}
@ -27,17 +26,21 @@ fn generic_in_place(_1: *mut Box<[T]>) -> () {
scope 23 (inlined <std::alloc::Global as Allocator>::deallocate) {
scope 24 (inlined std::alloc::Global::deallocate_impl) {
scope 25 (inlined std::alloc::Global::deallocate_impl_runtime) {
let mut _9: *mut u8;
let mut _8: *mut u8;
scope 26 (inlined Layout::size) {
}
scope 27 (inlined NonNull::<u8>::as_ptr) {
}
scope 28 (inlined std::alloc::dealloc) {
let mut _10: usize;
let mut _9: usize;
scope 29 (inlined Layout::size) {
}
scope 30 (inlined Layout::align) {
scope 31 (inlined std::ptr::Alignment::as_usize) {
scope 32 (inlined std::ptr::Alignment::as_nonzero) {
}
scope 33 (inlined NonZero::<usize>::get) {
}
}
}
}
@ -82,7 +85,6 @@ fn generic_in_place(_1: *mut Box<[T]>) -> () {
StorageLive(_4);
_3 = copy _2 as *mut [T] (Transmute);
_4 = copy _2 as *const [T] (Transmute);
StorageLive(_7);
_5 = std::intrinsics::size_of_val::<[T]>(move _4) -> [return: bb1, unwind unreachable];
}
@ -91,23 +93,21 @@ fn generic_in_place(_1: *mut Box<[T]>) -> () {
_6 = const <T as std::mem::SizedTypeProperties>::ALIGN;
_7 = copy _6 as std::ptr::Alignment (Transmute);
StorageDead(_6);
_8 = copy (_7.0: std::ptr::alignment::AlignmentEnum);
StorageDead(_7);
StorageDead(_4);
switchInt(copy _5) -> [0: bb4, otherwise: bb2];
}
bb2: {
StorageLive(_8);
_8 = copy _3 as *mut u8 (PtrToPtr);
StorageLive(_9);
_9 = copy _3 as *mut u8 (PtrToPtr);
StorageLive(_10);
_10 = discriminant(_8);
_11 = alloc::alloc::__rust_dealloc(move _9, move _5, move _10) -> [return: bb3, unwind unreachable];
_9 = copy _7 as usize (Transmute);
_10 = alloc::alloc::__rust_dealloc(move _8, move _5, move _9) -> [return: bb3, unwind unreachable];
}
bb3: {
StorageDead(_10);
StorageDead(_9);
StorageDead(_8);
goto -> bb4;
}

5
tests/mir-opt/pre-codegen/drop_boxed_slice.rs
View file

@ -11,8 +11,7 @@ pub unsafe fn generic_in_place<T: Copy>(ptr: *mut Box<[T]>) {
// CHECK: [[SIZE:_.+]] = std::intrinsics::size_of_val::<[T]>
// CHECK: [[ALIGN:_.+]] = const <T as std::mem::SizedTypeProperties>::ALIGN;
// CHECK: [[B:_.+]] = copy [[ALIGN]] as std::ptr::Alignment (Transmute);
// CHECK: [[C:_.+]] = copy ([[B]].0: std::ptr::alignment::AlignmentEnum);
// CHECK: [[D:_.+]] = discriminant([[C]]);
// CHECK: = alloc::alloc::__rust_dealloc({{.+}}, move [[SIZE]], move [[D]]) ->
// CHECK: [[C:_.+]] = copy [[B]] as usize (Transmute);
// CHECK: = alloc::alloc::__rust_dealloc({{.+}}, move [[SIZE]], move [[C]]) ->
std::ptr::drop_in_place(ptr)
}