relibc_compiler-builtins/testcrate/tests/count_leading_zeros.rs

#![feature(compiler_builtins_lib)]

extern crate compiler_builtins;

use compiler_builtins::int::__clzsi2;

#[test]
fn __clzsi2_test() {
    let mut i: usize = core::usize::MAX;
    // Check all values above 0
    while i > 0 {
        assert_eq!(__clzsi2(i) as u32, i.leading_zeros());
        i >>= 1;
    }
    // check 0 also
    i = 0;
    assert_eq!(__clzsi2(i) as u32, i.leading_zeros());
    // double check for bit patterns that aren't just solid 1s
    i = 1;
    for _ in 0..63 {
        assert_eq!(__clzsi2(i) as u32, i.leading_zeros());
        i <<= 2;
        i += 1;
    }
}