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rust/tests/codegen/option-as-slice.rs

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Move `Option::as_slice` to an always-sound implementation This approach depends on CSE to not have any branches or selects when the guessed offset is correct -- which it always will be right now -- but to also be *sound* (just less efficient) if the layout algorithms change such that the guess is incorrect.
2023-03-01 12:57:46 -06:00
// compile-flags: -O -Z randomize-layout=no
Add `Option::as_slice`(`_mut`) 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>>`.
2022-12-18 08:40:46 -06:00
// only-x86_64
ci: add a runner for vanilla LLVM 16 Like #107044, this will let us track compatibility with LLVM 16 going forward, especially after we eventually upgrade our own to the next. This also drops `tidy` here and in `x86_64-gnu-llvm-15`, syncing with that change in #106085.
2023-04-10 18:45:31 -05:00
// ignore-llvm-version: 16.0.0
// ^ needs https://reviews.llvm.org/D146149 in 16.0.1
Add `Option::as_slice`(`_mut`) 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>>`.
2022-12-18 08:40:46 -06:00
#![crate_type = "lib"]
#![feature(option_as_slice)]
extern crate core;
use core::num::NonZeroU64;
use core::option::Option;
// CHECK-LABEL: @u64_opt_as_slice
#[no_mangle]
pub fn u64_opt_as_slice(o: &Option<u64>) -> &[u64] {
// CHECK-NOT: select
Move `Option::as_slice` to an always-sound implementation This approach depends on CSE to not have any branches or selects when the guessed offset is correct -- which it always will be right now -- but to also be *sound* (just less efficient) if the layout algorithms change such that the guess is incorrect.
2023-03-01 12:57:46 -06:00
// CHECK-NOT: br
// CHECK-NOT: switch
// CHECK-NOT: icmp
Add `Option::as_slice`(`_mut`) 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>>`.
2022-12-18 08:40:46 -06:00
o.as_slice()
}
// CHECK-LABEL: @nonzero_u64_opt_as_slice
#[no_mangle]
pub fn nonzero_u64_opt_as_slice(o: &Option<NonZeroU64>) -> &[NonZeroU64] {
// CHECK-NOT: select
Move `Option::as_slice` to an always-sound implementation This approach depends on CSE to not have any branches or selects when the guessed offset is correct -- which it always will be right now -- but to also be *sound* (just less efficient) if the layout algorithms change such that the guess is incorrect.
2023-03-01 12:57:46 -06:00
// CHECK-NOT: br
// CHECK-NOT: switch
// CHECK-NOT: icmp
// CHECK: %[[NZ:.+]] = icmp ne i64 %{{.+}}, 0
// CHECK-NEXT: zext i1 %[[NZ]] to i64
// CHECK-NOT: select
// CHECK-NOT: br
// CHECK-NOT: switch
// CHECK-NOT: icmp
Add `Option::as_slice`(`_mut`) 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>>`.
2022-12-18 08:40:46 -06:00
o.as_slice()
}
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