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Remove useless assumes from slice::iter(_mut) #111447

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May 13, 2023
Merged

Remove useless assumes from slice::iter(_mut) #111447

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4 changes: 0 additions & 4 deletions library/core/src/slice/iter.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -90,8 +90,6 @@ impl<'a, T> Iter<'a, T> {
let ptr = slice.as_ptr();
// SAFETY: Similar to `IterMut::new`.
unsafe {
assume(!ptr.is_null());

let end = if T::IS_ZST { invalid(slice.len()) } else { ptr.add(slice.len()) };

Self { ptr: NonNull::new_unchecked(ptr as *mut T), end, _marker: PhantomData }
Expand Down Expand Up @@ -228,8 +226,6 @@ impl<'a, T> IterMut<'a, T> {
// See the `next_unchecked!` and `is_empty!` macros as well as the
// `post_inc_start` method for more information.
unsafe {
assume(!ptr.is_null());

let end = if T::IS_ZST { invalid_mut(slice.len()) } else { ptr.add(slice.len()) };

Self { ptr: NonNull::new_unchecked(ptr), end, _marker: PhantomData }
Expand Down
35 changes: 35 additions & 0 deletions tests/codegen/slice-iter-nonnull.rs
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Expand Up @@ -40,3 +40,38 @@ pub fn slice_iter_next_back<'a>(it: &mut std::slice::Iter<'a, u32>) -> Option<&'

it.next_back()
}

// The slice iterator `new` methods used to `assume` that the pointer is non-null,
// but passing slices already requires that, to the extent that LLVM actually
// removed the `call @llvm.assume` anyway. These tests just demonstrate that the
// attribute is there, and confirms adding the assume back doesn't do anything.

// CHECK-LABEL: @slice_iter_new
// CHECK-SAME: (ptr noalias noundef nonnull {{.+}} %slice.0, {{.+}} noundef %slice.1)
#[no_mangle]
pub fn slice_iter_new(slice: &[u32]) -> std::slice::Iter<'_, u32> {
// CHECK-NOT: slice
// CHECK: %[[END:.+]] = getelementptr inbounds i32{{.+}} %slice.0{{.+}} %slice.1
// CHECK-NOT: slice
// CHECK: insertvalue {{.+}} ptr %slice.0, 0
// CHECK-NOT: slice
// CHECK: insertvalue {{.+}} ptr %[[END]], 1
// CHECK-NOT: slice
// CHECK: }
slice.iter()
}

// CHECK-LABEL: @slice_iter_mut_new
// CHECK-SAME: (ptr noalias noundef nonnull {{.+}} %slice.0, {{.+}} noundef %slice.1)
#[no_mangle]
pub fn slice_iter_mut_new(slice: &mut [u32]) -> std::slice::IterMut<'_, u32> {
// CHECK-NOT: slice
// CHECK: %[[END:.+]] = getelementptr inbounds i32{{.+}} %slice.0{{.+}} %slice.1
// CHECK-NOT: slice
// CHECK: insertvalue {{.+}} ptr %slice.0, 0
// CHECK-NOT: slice
// CHECK: insertvalue {{.+}} ptr %[[END]], 1
// CHECK-NOT: slice
// CHECK: }
slice.iter_mut()
}
178 changes: 139 additions & 39 deletions tests/mir-opt/pre-codegen/slice_iter.forward_loop.PreCodegen.after.mir
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Expand Up @@ -6,58 +6,120 @@ fn forward_loop(_1: &[T], _2: impl Fn(&T)) -> () {
let mut _0: (); // return place in scope 0 at $DIR/slice_iter.rs:+0:60: +0:60
let mut _3: std::slice::Iter<'_, T>; // in scope 0 at $DIR/slice_iter.rs:+1:14: +1:26
let mut _4: std::slice::Iter<'_, T>; // in scope 0 at $DIR/slice_iter.rs:+1:14: +1:26
let mut _5: std::slice::Iter<'_, T>; // in scope 0 at $DIR/slice_iter.rs:+1:14: +1:26
let _6: (); // in scope 0 at $DIR/slice_iter.rs:+1:14: +1:26
let mut _7: std::option::Option<&T>; // in scope 0 at $DIR/slice_iter.rs:+1:14: +1:26
let mut _8: &mut std::slice::Iter<'_, T>; // in scope 0 at $DIR/slice_iter.rs:+1:14: +1:26
let mut _9: isize; // in scope 0 at $DIR/slice_iter.rs:+1:5: +3:6
let mut _11: &impl Fn(&T); // in scope 0 at $DIR/slice_iter.rs:+2:9: +2:10
let mut _12: (&T,); // in scope 0 at $DIR/slice_iter.rs:+2:9: +2:13
let _5: (); // in scope 0 at $DIR/slice_iter.rs:+1:14: +1:26
let mut _6: std::option::Option<&T>; // in scope 0 at $DIR/slice_iter.rs:+1:14: +1:26
let mut _7: &mut std::slice::Iter<'_, T>; // in scope 0 at $DIR/slice_iter.rs:+1:14: +1:26
let mut _8: isize; // in scope 0 at $DIR/slice_iter.rs:+1:5: +3:6
let mut _10: &impl Fn(&T); // in scope 0 at $DIR/slice_iter.rs:+2:9: +2:10
let mut _11: (&T,); // in scope 0 at $DIR/slice_iter.rs:+2:9: +2:13
scope 1 {
debug iter => _5; // in scope 1 at $DIR/slice_iter.rs:+1:14: +1:26
let _10: &T; // in scope 1 at $DIR/slice_iter.rs:+1:9: +1:10
debug iter => _4; // in scope 1 at $DIR/slice_iter.rs:+1:14: +1:26
let _9: &T; // in scope 1 at $DIR/slice_iter.rs:+1:9: +1:10
scope 2 {
debug x => _10; // in scope 2 at $DIR/slice_iter.rs:+1:9: +1:10
debug x => _9; // in scope 2 at $DIR/slice_iter.rs:+1:9: +1:10
}
}
scope 3 (inlined core::slice::<impl [T]>::iter) { // at $DIR/slice_iter.rs:28:20: 28:26
debug self => _1; // in scope 3 at $SRC_DIR/core/src/slice/mod.rs:LL:COL
scope 4 (inlined std::slice::Iter::<'_, T>::new) { // at $SRC_DIR/core/src/slice/mod.rs:LL:COL
debug slice => _1; // in scope 4 at $SRC_DIR/core/src/slice/iter.rs:LL:COL
let _12: *const T; // in scope 4 at $SRC_DIR/core/src/slice/iter.rs:LL:COL
let mut _14: bool; // in scope 4 at $SRC_DIR/core/src/slice/iter.rs:LL:COL
let mut _15: usize; // in scope 4 at $SRC_DIR/core/src/slice/iter.rs:LL:COL
let mut _16: usize; // in scope 4 at $SRC_DIR/core/src/slice/iter.rs:LL:COL
let mut _17: std::ptr::NonNull<T>; // in scope 4 at $SRC_DIR/core/src/slice/iter.rs:LL:COL
let mut _18: *mut T; // in scope 4 at $SRC_DIR/core/src/slice/iter.rs:LL:COL
let mut _19: *const T; // in scope 4 at $SRC_DIR/core/src/slice/iter.rs:LL:COL
scope 5 {
debug ptr => _12; // in scope 5 at $SRC_DIR/core/src/slice/iter.rs:LL:COL
scope 6 {
let _13: *const T; // in scope 6 at $SRC_DIR/core/src/slice/iter.rs:LL:COL
scope 7 {
debug end => _13; // in scope 7 at $SRC_DIR/core/src/slice/iter.rs:LL:COL
scope 13 (inlined NonNull::<T>::new_unchecked) { // at $SRC_DIR/core/src/slice/iter.rs:LL:COL
debug ptr => _18; // in scope 13 at $SRC_DIR/core/src/ptr/non_null.rs:LL:COL
let mut _21: *const T; // in scope 13 at $SRC_DIR/core/src/ptr/non_null.rs:LL:COL
let mut _22: *mut T; // in scope 13 at $SRC_DIR/core/src/intrinsics.rs:LL:COL
scope 14 {
scope 15 (inlined NonNull::<T>::new_unchecked::runtime::<T>) { // at $SRC_DIR/core/src/intrinsics.rs:LL:COL
debug ptr => _22; // in scope 15 at $SRC_DIR/core/src/intrinsics.rs:LL:COL
scope 16 (inlined ptr::mut_ptr::<impl *mut T>::is_null) { // at $SRC_DIR/core/src/ptr/non_null.rs:LL:COL
debug self => _22; // in scope 16 at $SRC_DIR/core/src/ptr/mut_ptr.rs:LL:COL
let mut _23: *mut u8; // in scope 16 at $SRC_DIR/core/src/ptr/mut_ptr.rs:LL:COL
scope 17 {
scope 18 (inlined ptr::mut_ptr::<impl *mut T>::is_null::runtime_impl) { // at $SRC_DIR/core/src/ptr/mut_ptr.rs:LL:COL
debug ptr => _23; // in scope 18 at $SRC_DIR/core/src/ptr/mut_ptr.rs:LL:COL
scope 19 (inlined ptr::mut_ptr::<impl *mut u8>::addr) { // at $SRC_DIR/core/src/ptr/mut_ptr.rs:LL:COL
debug self => _23; // in scope 19 at $SRC_DIR/core/src/ptr/mut_ptr.rs:LL:COL
scope 20 {
scope 21 (inlined ptr::mut_ptr::<impl *mut u8>::cast::<()>) { // at $SRC_DIR/core/src/ptr/mut_ptr.rs:LL:COL
debug self => _23; // in scope 21 at $SRC_DIR/core/src/ptr/mut_ptr.rs:LL:COL
}
}
}
}
}
}
}
}
}
}
scope 9 (inlined invalid::<T>) { // at $SRC_DIR/core/src/slice/iter.rs:LL:COL
debug addr => _15; // in scope 9 at $SRC_DIR/core/src/ptr/mod.rs:LL:COL
scope 10 {
}
}
scope 11 (inlined ptr::const_ptr::<impl *const T>::add) { // at $SRC_DIR/core/src/slice/iter.rs:LL:COL
debug self => _12; // in scope 11 at $SRC_DIR/core/src/ptr/const_ptr.rs:LL:COL
debug count => _16; // in scope 11 at $SRC_DIR/core/src/ptr/const_ptr.rs:LL:COL
scope 12 {
}
}
}
}
scope 8 (inlined core::slice::<impl [T]>::as_ptr) { // at $SRC_DIR/core/src/slice/iter.rs:LL:COL
debug self => _1; // in scope 8 at $SRC_DIR/core/src/slice/mod.rs:LL:COL
let mut _20: *const [T]; // in scope 8 at $SRC_DIR/core/src/slice/mod.rs:LL:COL
}
}
}
scope 4 (inlined <std::slice::Iter<'_, T> as IntoIterator>::into_iter) { // at $DIR/slice_iter.rs:28:14: 28:26
debug self => _4; // in scope 4 at $SRC_DIR/core/src/iter/traits/collect.rs:LL:COL
scope 22 (inlined <std::slice::Iter<'_, T> as IntoIterator>::into_iter) { // at $DIR/slice_iter.rs:28:14: 28:26
debug self => _3; // in scope 22 at $SRC_DIR/core/src/iter/traits/collect.rs:LL:COL
}

bb0: {
StorageLive(_3); // scope 0 at $DIR/slice_iter.rs:+1:14: +1:26
StorageLive(_4); // scope 0 at $DIR/slice_iter.rs:+1:14: +1:26
_4 = std::slice::Iter::<'_, T>::new(_1) -> [return: bb10, unwind: bb8]; // scope 3 at $SRC_DIR/core/src/slice/mod.rs:LL:COL
// mir::Constant
// + span: $SRC_DIR/core/src/slice/mod.rs:LL:COL
// + user_ty: UserType(0)
// + literal: Const { ty: fn(&[T]) -> std::slice::Iter<'_, T> {std::slice::Iter::<'_, T>::new}, val: Value(<ZST>) }
StorageLive(_12); // scope 3 at $SRC_DIR/core/src/slice/mod.rs:LL:COL
StorageLive(_20); // scope 8 at $SRC_DIR/core/src/slice/mod.rs:LL:COL
_20 = &raw const (*_1); // scope 8 at $SRC_DIR/core/src/slice/mod.rs:LL:COL
_12 = move _20 as *const T (PtrToPtr); // scope 8 at $SRC_DIR/core/src/slice/mod.rs:LL:COL
StorageDead(_20); // scope 8 at $SRC_DIR/core/src/slice/mod.rs:LL:COL
StorageLive(_13); // scope 6 at $SRC_DIR/core/src/slice/iter.rs:LL:COL
StorageLive(_14); // scope 6 at $SRC_DIR/core/src/slice/iter.rs:LL:COL
_14 = const _; // scope 6 at $SRC_DIR/core/src/slice/iter.rs:LL:COL
switchInt(move _14) -> [0: bb11, otherwise: bb10]; // scope 6 at $SRC_DIR/core/src/slice/iter.rs:LL:COL
}

bb1: {
StorageLive(_7); // scope 1 at $DIR/slice_iter.rs:+1:14: +1:26
_8 = &mut _5; // scope 1 at $DIR/slice_iter.rs:+1:14: +1:26
_7 = <std::slice::Iter<'_, T> as Iterator>::next(_8) -> [return: bb2, unwind: bb8]; // scope 1 at $DIR/slice_iter.rs:+1:14: +1:26
StorageLive(_6); // scope 1 at $DIR/slice_iter.rs:+1:14: +1:26
_7 = &mut _4; // scope 1 at $DIR/slice_iter.rs:+1:14: +1:26
_6 = <std::slice::Iter<'_, T> as Iterator>::next(_7) -> [return: bb2, unwind: bb8]; // scope 1 at $DIR/slice_iter.rs:+1:14: +1:26
// mir::Constant
// + span: $DIR/slice_iter.rs:28:14: 28:26
// + literal: Const { ty: for<'a> fn(&'a mut std::slice::Iter<'_, T>) -> Option<<std::slice::Iter<'_, T> as Iterator>::Item> {<std::slice::Iter<'_, T> as Iterator>::next}, val: Value(<ZST>) }
}

bb2: {
_9 = discriminant(_7); // scope 1 at $DIR/slice_iter.rs:+1:14: +1:26
switchInt(move _9) -> [0: bb5, 1: bb3, otherwise: bb4]; // scope 1 at $DIR/slice_iter.rs:+1:14: +1:26
_8 = discriminant(_6); // scope 1 at $DIR/slice_iter.rs:+1:14: +1:26
switchInt(move _8) -> [0: bb5, 1: bb3, otherwise: bb4]; // scope 1 at $DIR/slice_iter.rs:+1:14: +1:26
}

bb3: {
_10 = ((_7 as Some).0: &T); // scope 1 at $DIR/slice_iter.rs:+1:9: +1:10
StorageLive(_11); // scope 2 at $DIR/slice_iter.rs:+2:9: +2:10
_11 = &_2; // scope 2 at $DIR/slice_iter.rs:+2:9: +2:10
StorageLive(_12); // scope 2 at $DIR/slice_iter.rs:+2:9: +2:13
_12 = (_10,); // scope 2 at $DIR/slice_iter.rs:+2:9: +2:13
_6 = <impl Fn(&T) as Fn<(&T,)>>::call(move _11, move _12) -> [return: bb6, unwind: bb8]; // scope 2 at $DIR/slice_iter.rs:+2:9: +2:13
_9 = ((_6 as Some).0: &T); // scope 1 at $DIR/slice_iter.rs:+1:9: +1:10
StorageLive(_10); // scope 2 at $DIR/slice_iter.rs:+2:9: +2:10
_10 = &_2; // scope 2 at $DIR/slice_iter.rs:+2:9: +2:10
StorageLive(_11); // scope 2 at $DIR/slice_iter.rs:+2:9: +2:13
_11 = (_9,); // scope 2 at $DIR/slice_iter.rs:+2:9: +2:13
_5 = <impl Fn(&T) as Fn<(&T,)>>::call(move _10, move _11) -> [return: bb6, unwind: bb8]; // scope 2 at $DIR/slice_iter.rs:+2:9: +2:13
// mir::Constant
// + span: $DIR/slice_iter.rs:29:9: 29:10
// + literal: Const { ty: for<'a> extern "rust-call" fn(&'a impl Fn(&T), (&T,)) -> <impl Fn(&T) as FnOnce<(&T,)>>::Output {<impl Fn(&T) as Fn<(&T,)>>::call}, val: Value(<ZST>) }
Expand All @@ -68,16 +130,15 @@ fn forward_loop(_1: &[T], _2: impl Fn(&T)) -> () {
}

bb5: {
StorageDead(_7); // scope 1 at $DIR/slice_iter.rs:+3:5: +3:6
StorageDead(_5); // scope 0 at $DIR/slice_iter.rs:+3:5: +3:6
StorageDead(_3); // scope 0 at $DIR/slice_iter.rs:+3:5: +3:6
StorageDead(_6); // scope 1 at $DIR/slice_iter.rs:+3:5: +3:6
StorageDead(_4); // scope 0 at $DIR/slice_iter.rs:+3:5: +3:6
drop(_2) -> bb7; // scope 0 at $DIR/slice_iter.rs:+4:1: +4:2
}

bb6: {
StorageDead(_12); // scope 2 at $DIR/slice_iter.rs:+2:12: +2:13
StorageDead(_11); // scope 2 at $DIR/slice_iter.rs:+2:12: +2:13
StorageDead(_7); // scope 1 at $DIR/slice_iter.rs:+3:5: +3:6
StorageDead(_10); // scope 2 at $DIR/slice_iter.rs:+2:12: +2:13
StorageDead(_6); // scope 1 at $DIR/slice_iter.rs:+3:5: +3:6
goto -> bb1; // scope 1 at $DIR/slice_iter.rs:+1:5: +3:6
}

Expand All @@ -94,10 +155,49 @@ fn forward_loop(_1: &[T], _2: impl Fn(&T)) -> () {
}

bb10: {
_3 = move _4; // scope 4 at $SRC_DIR/core/src/iter/traits/collect.rs:LL:COL
StorageDead(_4); // scope 0 at $DIR/slice_iter.rs:+1:25: +1:26
StorageLive(_5); // scope 0 at $DIR/slice_iter.rs:+1:14: +1:26
_5 = move _3; // scope 0 at $DIR/slice_iter.rs:+1:14: +1:26
StorageLive(_15); // scope 6 at $SRC_DIR/core/src/slice/iter.rs:LL:COL
_15 = Len((*_1)); // scope 6 at $SRC_DIR/core/src/slice/iter.rs:LL:COL
_13 = _15 as *const T (Transmute); // scope 10 at $SRC_DIR/core/src/ptr/mod.rs:LL:COL
StorageDead(_15); // scope 6 at $SRC_DIR/core/src/slice/iter.rs:LL:COL
goto -> bb12; // scope 6 at $SRC_DIR/core/src/slice/iter.rs:LL:COL
}

bb11: {
StorageLive(_16); // scope 6 at $SRC_DIR/core/src/slice/iter.rs:LL:COL
_16 = Len((*_1)); // scope 6 at $SRC_DIR/core/src/slice/iter.rs:LL:COL
_13 = Offset(_12, _16); // scope 12 at $SRC_DIR/core/src/ptr/const_ptr.rs:LL:COL
StorageDead(_16); // scope 6 at $SRC_DIR/core/src/slice/iter.rs:LL:COL
goto -> bb12; // scope 6 at $SRC_DIR/core/src/slice/iter.rs:LL:COL
}

bb12: {
StorageDead(_14); // scope 6 at $SRC_DIR/core/src/slice/iter.rs:LL:COL
StorageLive(_17); // scope 7 at $SRC_DIR/core/src/slice/iter.rs:LL:COL
StorageLive(_18); // scope 7 at $SRC_DIR/core/src/slice/iter.rs:LL:COL
_18 = _12 as *mut T (PtrToPtr); // scope 7 at $SRC_DIR/core/src/slice/iter.rs:LL:COL
StorageLive(_21); // scope 7 at $SRC_DIR/core/src/slice/iter.rs:LL:COL
StorageLive(_22); // scope 7 at $SRC_DIR/core/src/slice/iter.rs:LL:COL
StorageLive(_23); // scope 7 at $SRC_DIR/core/src/slice/iter.rs:LL:COL
_21 = _18 as *const T (Pointer(MutToConstPointer)); // scope 14 at $SRC_DIR/core/src/ptr/non_null.rs:LL:COL
_17 = NonNull::<T> { pointer: _21 }; // scope 14 at $SRC_DIR/core/src/ptr/non_null.rs:LL:COL
StorageDead(_23); // scope 7 at $SRC_DIR/core/src/slice/iter.rs:LL:COL
StorageDead(_22); // scope 7 at $SRC_DIR/core/src/slice/iter.rs:LL:COL
StorageDead(_21); // scope 7 at $SRC_DIR/core/src/slice/iter.rs:LL:COL
StorageDead(_18); // scope 7 at $SRC_DIR/core/src/slice/iter.rs:LL:COL
StorageLive(_19); // scope 7 at $SRC_DIR/core/src/slice/iter.rs:LL:COL
_19 = _13; // scope 7 at $SRC_DIR/core/src/slice/iter.rs:LL:COL
_3 = std::slice::Iter::<'_, T> { ptr: move _17, end: move _19, _marker: const ZeroSized: PhantomData<&T> }; // scope 7 at $SRC_DIR/core/src/slice/iter.rs:LL:COL
// mir::Constant
// + span: no-location
// + literal: Const { ty: PhantomData<&T>, val: Value(<ZST>) }
// adt
// + user_ty: UserType(1)
StorageDead(_19); // scope 7 at $SRC_DIR/core/src/slice/iter.rs:LL:COL
StorageDead(_17); // scope 7 at $SRC_DIR/core/src/slice/iter.rs:LL:COL
StorageDead(_13); // scope 6 at $SRC_DIR/core/src/slice/iter.rs:LL:COL
StorageDead(_12); // scope 3 at $SRC_DIR/core/src/slice/mod.rs:LL:COL
StorageLive(_4); // scope 0 at $DIR/slice_iter.rs:+1:14: +1:26
_4 = move _3; // scope 0 at $DIR/slice_iter.rs:+1:14: +1:26
goto -> bb1; // scope 1 at $DIR/slice_iter.rs:+1:5: +3:6
}
}
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