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41da875fae
This adds the following functions: * `Option<T>::as_slice(&self) -> &[T]` * `Option<T>::as_slice_mut(&mut self) -> &[T]` The `as_slice` and `as_slice_mut` functions benefit from an optimization that makes them completely branch-free. Note that the optimization's soundness hinges on the fact that either the niche optimization makes the offset of the `Some(_)` contents zero or the mempory layout of `Option<T>` is equal to that of `Option<MaybeUninit<T>>`.
29 lines
561 B
Rust
29 lines
561 B
Rust
// compile-flags: -O
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// only-x86_64
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#![crate_type = "lib"]
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#![feature(option_as_slice)]
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extern crate core;
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use core::num::NonZeroU64;
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use core::option::Option;
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// CHECK-LABEL: @u64_opt_as_slice
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#[no_mangle]
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pub fn u64_opt_as_slice(o: &Option<u64>) -> &[u64] {
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// CHECK: start:
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// CHECK-NOT: select
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// CHECK: ret
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o.as_slice()
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}
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// CHECK-LABEL: @nonzero_u64_opt_as_slice
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#[no_mangle]
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pub fn nonzero_u64_opt_as_slice(o: &Option<NonZeroU64>) -> &[NonZeroU64] {
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// CHECK: start:
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// CHECK-NOT: select
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// CHECK: ret
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o.as_slice()
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}
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