holey-bytes/vm/src/float/x86_64.rs

use {
    core::arch::{asm, x86_64 as arin},
    hbbytecode::RoundingMode,
};

macro_rules! gen_op {
    [$($ty:ident => $reg:ident),* $(,)?] => {
        macro_rules! op {
            $(
                ($ins:literal, $in:expr, $out:expr => $ty) => {
                    asm!(concat!($ins, " {}, {}"), out($reg) $out, in(xmm_reg) $in)
                };
            )*
        }
    };
}

gen_op![
    f32 => xmm_reg,
    f64 => xmm_reg,
    i64 => reg,
];

macro_rules! fnsdef {
    {$(
        $(#[$attr:meta])*
        $vis:vis fn $name:ident($from:ident -> $to:ident): $ins:literal;
    )*} => {$(
        $(#[$attr])*
        $vis fn $name(val: $from, mode: RoundingMode) -> $to {
            let result: $to;
            unsafe {
                let mut mxcsr = 0_u32;
                'a: {
                    asm!("stmxcsr [{}]", in(reg) &mut mxcsr);
                    asm!(
                        "ldmxcsr [{}]",
                        in(reg) &(mxcsr & !arin::_MM_ROUND_MASK | match mode {
                            RoundingMode::NearestEven => break 'a,
                            RoundingMode::Truncate => arin::_MM_ROUND_TOWARD_ZERO,
                            RoundingMode::Up => arin::_MM_ROUND_UP,
                            RoundingMode::Down => arin::_MM_ROUND_DOWN,
                        })
                    );
                }

                op!($ins, val, result => $to);

                // Set MXCSR to original value
                asm!("ldmxcsr [{}]", in(reg) &mxcsr);
            }
            result
        }
    )*};
}

fnsdef! {
    /// Convert [`f64`] to [`f32`] with chosen rounding mode
    pub fn conv64to32(f64 -> f32): "cvtsd2ss";
    /// Convert [`f32`] to [`i64`] with chosen rounding mode
    pub fn f32toint(f32 -> i64): "cvttss2si";
    /// Convert [`f64`] to [`i64`] with chosen rounding mode
    pub fn f64toint(f64 -> i64): "cvttsd2si";
}