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