luaur-code-gen 0.1.0

Native (A64/X64) code generation for Luau (Rust).
Documentation 
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pub fn get_fmov_imm_fp_64(value: f64) -> i32 {
    let u = value.to_bits();

    // positive 0 is encodable via movi
    if u == 0 {
        return 256;
    }

    // early out: fmov can only encode doubles with 48 least significant zeros
    if (u & ((1u64 << 48) - 1)) != 0 {
        return -1;
    }

    // f64 expansion is abcdfegh => aBbbbbbb bbcdefgh 00000000 00000000 00000000 00000000 00000000 00000000
    let imm = (((u >> 56) as i32) & 0x80) | (((u >> 48) as i32) & 0x7f);
    let dec = ((imm & 0x80) << 8)
        | (if (imm & 0x40) != 0 {
            0b00111111_11000000
        } else {
            0b01000000_00000000
        })
        | (imm & 0x3f);

    if dec == ((u >> 48) as i32) {
        imm
    } else {
        -1
    }
}