core/stdarch/crates/core_arch/src/x86_64/
rdrand.rs

1//! RDRAND and RDSEED instructions for returning random numbers from an Intel
2//! on-chip hardware random number generator which has been seeded by an
3//! on-chip entropy source.
4
5#![allow(clippy::module_name_repetitions)]
6
7#[allow(improper_ctypes)]
8unsafe extern "unadjusted" {
9    #[link_name = "llvm.x86.rdrand.64"]
10    fn x86_rdrand64_step() -> (u64, i32);
11    #[link_name = "llvm.x86.rdseed.64"]
12    fn x86_rdseed64_step() -> (u64, i32);
13}
14
15#[cfg(test)]
16use stdarch_test::assert_instr;
17
18/// Read a hardware generated 64-bit random value and store the result in val.
19/// Returns 1 if a random value was generated, and 0 otherwise.
20///
21/// [Intel's documentation](https://www.intel.com/content/www/us/en/docs/intrinsics-guide/index.html#text=_rdrand64_step)
22#[inline]
23#[target_feature(enable = "rdrand")]
24#[cfg_attr(test, assert_instr(rdrand))]
25#[stable(feature = "simd_x86", since = "1.27.0")]
26pub unsafe fn _rdrand64_step(val: &mut u64) -> i32 {
27    let (v, flag) = x86_rdrand64_step();
28    *val = v;
29    flag
30}
31
32/// Read a 64-bit NIST SP800-90B and SP800-90C compliant random value and store
33/// in val. Return 1 if a random value was generated, and 0 otherwise.
34///
35/// [Intel's documentation](https://www.intel.com/content/www/us/en/docs/intrinsics-guide/index.html#text=_rdseed64_step)
36#[inline]
37#[target_feature(enable = "rdseed")]
38#[cfg_attr(test, assert_instr(rdseed))]
39#[stable(feature = "simd_x86", since = "1.27.0")]
40pub unsafe fn _rdseed64_step(val: &mut u64) -> i32 {
41    let (v, flag) = x86_rdseed64_step();
42    *val = v;
43    flag
44}