nontemporal_store: make sure that the intrinsic is truly just a hint · patricklam/verify-rust-std@e6aede2 (original) (raw)

`@@ -2386,12 +2386,12 @@ extern "rust-intrinsic" {

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`#[rustc_nounwind]

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`pub fn catch_unwind(try_fn: fn(*mut u8), data: *mut u8, catch_fn: fn(*mut u8, *mut u8)) -> i32;

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`` -

/// Emits a !nontemporal store according to LLVM (see their docs).

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/// Probably will never become stable.

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`` +

/// Emits a nontemporal store, which gives a hint to the CPU that the data should not be held

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`` +

/// in cache. Except for performance, this is fully equivalent to ptr.write(val).

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`///

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/// Do NOT use this intrinsic; "nontemporal" operations do not exist in our memory model!

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/// It exists to support current stdarch, but the plan is to change stdarch and remove this intrinsic.

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`` +

/// Not all architectures provide such an operation. For instance, x86 does not: while MOVNT

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`` +

/// exists, that operation is not equivalent to ptr.write(val) (MOVNT writes can be reordered

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/// in ways that are not allowed for regular writes).

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`#[rustc_nounwind]

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`pub fn nontemporal_store(ptr: *mut T, val: T);

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