mirror of
https://github.com/rust-lang/rust.git
synced 2024-11-22 14:55:26 +00:00
57 lines
1.8 KiB
Rust
57 lines
1.8 KiB
Rust
// compile-flags: -O
|
|
// only-x86_64
|
|
// ignore-debug: the debug assertions get in the way
|
|
|
|
#![crate_type = "lib"]
|
|
#![feature(iter_repeat_n)]
|
|
|
|
#[derive(Clone)]
|
|
pub struct NotCopy(u16);
|
|
|
|
impl Drop for NotCopy {
|
|
fn drop(&mut self) {}
|
|
}
|
|
|
|
// For a type where `Drop::drop` doesn't do anything observable and a clone is the
|
|
// same as a move, make sure that the extra case for the last item disappears.
|
|
|
|
#[no_mangle]
|
|
// CHECK-LABEL: @iter_repeat_n_next
|
|
pub fn iter_repeat_n_next(it: &mut std::iter::RepeatN<NotCopy>) -> Option<NotCopy> {
|
|
// CHECK-NEXT: start:
|
|
// CHECK-NOT: br
|
|
// CHECK: %[[COUNT:.+]] = load i64
|
|
// CHECK-NEXT: %[[COUNT_ZERO:.+]] = icmp eq i64 %[[COUNT]], 0
|
|
// CHECK-NEXT: br i1 %[[COUNT_ZERO]], label %[[EMPTY:.+]], label %[[NOT_EMPTY:.+]]
|
|
|
|
// CHECK: [[NOT_EMPTY]]:
|
|
// CHECK-NEXT: %[[DEC:.+]] = add i64 %[[COUNT]], -1
|
|
// CHECK-NEXT: store i64 %[[DEC]]
|
|
// CHECK-NOT: br
|
|
// CHECK: %[[VAL:.+]] = load i16
|
|
// CHECK-NEXT: br label %[[EMPTY]]
|
|
|
|
// CHECK: [[EMPTY]]:
|
|
// CHECK-NOT: br
|
|
// CHECK: phi i16 [ undef, %start ], [ %[[VAL]], %[[NOT_EMPTY]] ]
|
|
// CHECK-NOT: br
|
|
// CHECK: ret
|
|
|
|
it.next()
|
|
}
|
|
|
|
// And as a result, using the iterator can optimize without special cases for
|
|
// the last iteration, like `memset`ing all the items in one call.
|
|
|
|
#[no_mangle]
|
|
// CHECK-LABEL: @vec_extend_via_iter_repeat_n
|
|
pub fn vec_extend_via_iter_repeat_n() -> Vec<u8> {
|
|
// CHECK: %[[ADDR:.+]] = tail call noundef dereferenceable_or_null(1234) ptr @__rust_alloc(i64 noundef 1234, i64 noundef 1)
|
|
// CHECK: tail call void @llvm.memset.p0.i64(ptr noundef nonnull align 1 dereferenceable(1234) %[[ADDR]], i8 42, i64 1234,
|
|
|
|
let n = 1234_usize;
|
|
let mut v = Vec::with_capacity(n);
|
|
v.extend(std::iter::repeat_n(42_u8, n));
|
|
v
|
|
}
|