[rust-lang/rust] Tracking Issue for `stdarch_aarch64_rand`

### ROOT CAUSE The issue is tracking the stabilization of the `stdarch_aarch64_rand` feature, which provides intrinsics for ARMv8.5's random number generation. The root cause is that these intrinsics are not yet part of the Rust standard library and require coordination for stabilization, including implementation, review, and final comment periods. ### CODE FIX To stabilize this feature, implement the intrinsics by adding the following code to the Rust standard library, conditionally compiled with `#[target_feature(enable = "rand")]`: ```rust #[target_feature(enable = "rand")] pub unsafe fn __rndr(value: *mut u64) -> i32 { // Implementation based on ARMv8.5 assembly intrinsics // Example: asm!("rndr {0}, {1}", out(reg) $result, in(reg) *value); // This is a placeholder; actual implementation must match the ARMv8.5 specification. unimplemented!() } #[target_feature(enable = "rand")] pub unsafe fn __rndrrs(value: *mut u64) -> i32 { // Similarly, implement based on ARMv8.5 assembly intrinsics // Example: asm!("rndrrs {0}, {1}", out(reg) $result, in(reg) *value); unimplemented!() } ``` Additionally, update the stabilization checklist: - [ ] ACP: rust-lang/libs-team#... - [ ] Implementation: #... - [ ] Final comment period (FCP) - [ ] Stabilization PR This approach mirrors the conditional compilation pattern for other target features (e.g., AVX2) in Rust, ensuring safety and proper feature gating. The stabilization process must follow Rust's RFC and stabilization guidelines.