core/stdarch/crates/core_arch/src/aarch64/
prefetch.rs

1#[cfg(test)]
2use stdarch_test::assert_instr;
3
4extern "unadjusted" {
5    #[link_name = "llvm.prefetch"]
6    fn prefetch(p: *const i8, rw: i32, loc: i32, ty: i32);
7}
8
9/// See [`prefetch`](fn._prefetch.html).
10#[unstable(feature = "stdarch_aarch64_prefetch", issue = "117217")]
11pub const _PREFETCH_READ: i32 = 0;
12
13/// See [`prefetch`](fn._prefetch.html).
14#[unstable(feature = "stdarch_aarch64_prefetch", issue = "117217")]
15pub const _PREFETCH_WRITE: i32 = 1;
16
17/// See [`prefetch`](fn._prefetch.html).
18#[unstable(feature = "stdarch_aarch64_prefetch", issue = "117217")]
19pub const _PREFETCH_LOCALITY0: i32 = 0;
20
21/// See [`prefetch`](fn._prefetch.html).
22#[unstable(feature = "stdarch_aarch64_prefetch", issue = "117217")]
23pub const _PREFETCH_LOCALITY1: i32 = 1;
24
25/// See [`prefetch`](fn._prefetch.html).
26#[unstable(feature = "stdarch_aarch64_prefetch", issue = "117217")]
27pub const _PREFETCH_LOCALITY2: i32 = 2;
28
29/// See [`prefetch`](fn._prefetch.html).
30#[unstable(feature = "stdarch_aarch64_prefetch", issue = "117217")]
31pub const _PREFETCH_LOCALITY3: i32 = 3;
32
33/// Fetch the cache line that contains address `p` using the given `RW` and `LOCALITY`.
34///
35/// The `RW` must be one of:
36///
37/// * [`_PREFETCH_READ`](constant._PREFETCH_READ.html): the prefetch is preparing
38///   for a read.
39///
40/// * [`_PREFETCH_WRITE`](constant._PREFETCH_WRITE.html): the prefetch is preparing
41///   for a write.
42///
43/// The `LOCALITY` must be one of:
44///
45/// * [`_PREFETCH_LOCALITY0`](constant._PREFETCH_LOCALITY0.html): Streaming or
46///   non-temporal prefetch, for data that is used only once.
47///
48/// * [`_PREFETCH_LOCALITY1`](constant._PREFETCH_LOCALITY1.html): Fetch into level 3 cache.
49///
50/// * [`_PREFETCH_LOCALITY2`](constant._PREFETCH_LOCALITY2.html): Fetch into level 2 cache.
51///
52/// * [`_PREFETCH_LOCALITY3`](constant._PREFETCH_LOCALITY3.html): Fetch into level 1 cache.
53///
54/// The prefetch memory instructions signal to the memory system that memory accesses
55/// from a specified address are likely to occur in the near future. The memory system
56/// can respond by taking actions that are expected to speed up the memory access when
57/// they do occur, such as preloading the specified address into one or more caches.
58/// Because these signals are only hints, it is valid for a particular CPU to treat
59/// any or all prefetch instructions as a NOP.
60///
61///
62/// [Arm's documentation](https://developer.arm.com/documentation/den0024/a/the-a64-instruction-set/memory-access-instructions/prefetching-memory?lang=en)
63#[inline(always)]
64#[cfg_attr(test, assert_instr("prfm pldl1strm", RW = _PREFETCH_READ, LOCALITY = _PREFETCH_LOCALITY0))]
65#[cfg_attr(test, assert_instr("prfm pldl3keep", RW = _PREFETCH_READ, LOCALITY = _PREFETCH_LOCALITY1))]
66#[cfg_attr(test, assert_instr("prfm pldl2keep", RW = _PREFETCH_READ, LOCALITY = _PREFETCH_LOCALITY2))]
67#[cfg_attr(test, assert_instr("prfm pldl1keep", RW = _PREFETCH_READ, LOCALITY = _PREFETCH_LOCALITY3))]
68#[cfg_attr(test, assert_instr("prfm pstl1strm", RW = _PREFETCH_WRITE, LOCALITY = _PREFETCH_LOCALITY0))]
69#[cfg_attr(test, assert_instr("prfm pstl3keep", RW = _PREFETCH_WRITE, LOCALITY = _PREFETCH_LOCALITY1))]
70#[cfg_attr(test, assert_instr("prfm pstl2keep", RW = _PREFETCH_WRITE, LOCALITY = _PREFETCH_LOCALITY2))]
71#[cfg_attr(test, assert_instr("prfm pstl1keep", RW = _PREFETCH_WRITE, LOCALITY = _PREFETCH_LOCALITY3))]
72#[rustc_legacy_const_generics(1, 2)]
73#[unstable(feature = "stdarch_aarch64_prefetch", issue = "117217")]
74// FIXME: Replace this with the standard ACLE __pld/__pldx/__pli/__plix intrinsics
75pub unsafe fn _prefetch<const RW: i32, const LOCALITY: i32>(p: *const i8) {
76    // We use the `llvm.prefetch` intrinsic with `cache type` = 1 (data cache).
77    static_assert_uimm_bits!(RW, 1);
78    static_assert_uimm_bits!(LOCALITY, 2);
79    prefetch(p, RW, LOCALITY, 1);
80}
core/stdarch/crates/core_arch/src/aarch64/prefetch.rs

core/stdarch/crates/core_arch/src/aarch64/
prefetch.rs
