fmax.zig

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Code

const std = @import("std");
const builtin = @import("builtin");
const math = std.math;
const arch = builtin.cpu.arch;
const compiler_rt = @import("../compiler_rt.zig");
const symbol = compiler_rt.symbol;

comptime {
    symbol(&__fmaxh, "__fmaxh");
    symbol(&fmaxf, "fmaxf");
    symbol(&fmax, "fmax");
    symbol(&__fmaxx, "__fmaxx");
    if (compiler_rt.want_ppc_abi) {
        symbol(&fmaxq, "fmaxf128");
    }
    symbol(&fmaxq, "fmaxq");
    symbol(&fmaxl, "fmaxl");
}

pub fn __fmaxh(x: f16, y: f16) callconv(.c) f16 {
    return generic_fmax(f16, x, y);
}

pub fn fmaxf(x: f32, y: f32) callconv(.c) f32 {
    return generic_fmax(f32, x, y);
}

pub fn fmax(x: f64, y: f64) callconv(.c) f64 {
    return generic_fmax(f64, x, y);
}

pub fn __fmaxx(x: f80, y: f80) callconv(.c) f80 {
    return generic_fmax(f80, x, y);
}

pub fn fmaxq(x: f128, y: f128) callconv(.c) f128 {
    return generic_fmax(f128, x, y);
}

pub fn fmaxl(x: c_longdouble, y: c_longdouble) callconv(.c) c_longdouble {
    switch (@typeInfo(c_longdouble).float.bits) {
        64 => return fmax(x, y),
        80 => return __fmaxx(x, y),
        128 => return fmaxq(x, y),
        else => @compileError("unreachable"),
    }
}

inline fn generic_fmax(comptime T: type, x: T, y: T) T {
    if (math.isNan(x))
        return y;
    if (math.isNan(y))
        return x;
    if (math.signbit(x) != math.signbit(y))
        return if (math.signbit(x)) y else x;
    return if (x < y) y else x;
}

test "generic_fmax" {
    inline for ([_]type{ f32, f64, c_longdouble, f80, f128 }) |T| {
        const nan_val = math.nan(T);
        const Int = @Int(.unsigned, @bitSizeOf(T));

        try std.testing.expect(math.isNan(generic_fmax(T, nan_val, nan_val)));
        try std.testing.expectEqual(@as(T, 1.0), generic_fmax(T, nan_val, 1.0));
        try std.testing.expectEqual(@as(T, 1.0), generic_fmax(T, 1.0, nan_val));

        try std.testing.expectEqual(@as(T, 10.0), generic_fmax(T, 1.0, 10.0));
        try std.testing.expectEqual(@as(T, 1.0), generic_fmax(T, 1.0, -1.0));

        try std.testing.expectEqual(@as(Int, @bitCast(@as(T, 0.0))), @as(Int, @bitCast(generic_fmax(T, 0.0, -0.0))));
        try std.testing.expectEqual(@as(Int, @bitCast(@as(T, 0.0))), @as(Int, @bitCast(generic_fmax(T, -0.0, 0.0))));
    }
}