Zig 0.17.0-dev (Split by item)

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cos

cos.cos

pub fn cos(x: f64) callconv(.c) f64

File

lib/compiler_rt/cos.zig:97

Code

pub fn cos(x: f64) callconv(.c) f64 {
    var ix = @as(u64, @bitCast(x)) >> 32;
    ix &= 0x7fffffff;

    // |x| ~< pi/4
    if (ix <= 0x3fe921fb) {
        if (ix < 0x3e46a09e) { // |x| < 2**-27 * sqrt(2)
            // raise inexact if x!=0
            if (compiler_rt.want_float_exceptions) mem.doNotOptimizeAway(x + 0x1p120);
            return 1.0;
        }
        return trig.cos(x, 0);
    }

    // cos(Inf or NaN) is NaN
    if (ix >= 0x7ff00000) {
        return x - x;
    }

    var y: [2]f64 = undefined;
    const n = rem_pio2(x, &y);
    return switch (n & 3) {
        0 => trig.cos(y[0], y[1]),
        1 => -trig.sin(y[0], y[1], 1),
        2 => -trig.cos(y[0], y[1]),
        else => trig.sin(y[0], y[1], 1),
    };
}