crates/core_arch/src/arm/sat.rs

//! # References:
//!
//! - Section 8.4 "Saturating intrinsics"

#[cfg(test)]
use stdarch_test::assert_instr;

/// Saturates a 32-bit signed integer to a signed integer with a given
/// bit width.
#[unstable(feature = "stdarch_arm_sat", issue = "none")]
#[inline]
#[cfg_attr(test, assert_instr("ssat", WIDTH = 8))]
#[rustc_legacy_const_generics(1)]
pub unsafe fn __ssat<const WIDTH: u32>(x: i32) -> i32 {
    static_assert!(matches!(WIDTH, 1..=32));
    arm_ssat(x, WIDTH as i32)
}

/// Saturates a 32-bit signed integer to an unsigned integer with a given
/// bit width.
#[unstable(feature = "stdarch_arm_sat", issue = "none")]
#[inline]
#[cfg_attr(test, assert_instr("usat", WIDTH = 8))]
#[rustc_legacy_const_generics(1)]
pub unsafe fn __usat<const WIDTH: u32>(x: i32) -> u32 {
    static_assert!(matches!(WIDTH, 1..=32));
    arm_usat(x, WIDTH as i32)
}

unsafe extern "unadjusted" {
    #[link_name = "llvm.arm.ssat"]
    fn arm_ssat(x: i32, y: i32) -> i32;

    #[link_name = "llvm.arm.usat"]
    fn arm_usat(x: i32, y: i32) -> u32;
}

#[cfg(test)]
mod tests {
    use super::*;
    use stdarch_test::simd_test;

    #[test]
    fn test_ssat() {
        unsafe {
            assert_eq!(__ssat::<8>(1), 1);
            assert_eq!(__ssat::<8>(1000), 127);
            assert_eq!(__ssat::<8>(-1), -1);
            assert_eq!(__ssat::<8>(-1000), -128);
        }
    }

    #[test]
    fn test_usat() {
        unsafe {
            assert_eq!(__usat::<8>(1), 1);
            assert_eq!(__usat::<8>(1000), 255);
            assert_eq!(__usat::<8>(-1), 0);
            assert_eq!(__usat::<8>(-1000), 0);
        }
    }
}