1//! Ported from:
 2//!
 3//! https://github.com/llvm/llvm-project/blob/2ffb1b0413efa9a24eb3c49e710e36f92e2cb50b/compiler-rt/lib/builtins/modti3.c
 4
 5const std = @import("std");
 6const builtin = @import("builtin");
 7const udivmod = @import("udivmod.zig").udivmod;
 8const common = @import("common.zig");
 9
10pub const panic = common.panic;
11
12comptime {
13    if (common.want_windows_v2u64_abi) {
14        @export(&__modti3_windows_x86_64, .{ .name = "__modti3", .linkage = common.linkage, .visibility = common.visibility });
15    } else {
16        @export(&__modti3, .{ .name = "__modti3", .linkage = common.linkage, .visibility = common.visibility });
17    }
18}
19
20pub fn __modti3(a: i128, b: i128) callconv(.c) i128 {
21    return mod(a, b);
22}
23
24const v2u64 = @Vector(2, u64);
25
26fn __modti3_windows_x86_64(a: v2u64, b: v2u64) callconv(.c) v2u64 {
27    return @bitCast(mod(@as(i128, @bitCast(a)), @as(i128, @bitCast(b))));
28}
29
30inline fn mod(a: i128, b: i128) i128 {
31    const s_a = a >> (128 - 1); // s = a < 0 ? -1 : 0
32    const s_b = b >> (128 - 1); // s = b < 0 ? -1 : 0
33
34    const an = (a ^ s_a) -% s_a; // negate if s == -1
35    const bn = (b ^ s_b) -% s_b; // negate if s == -1
36
37    var r: u128 = undefined;
38    _ = udivmod(u128, @as(u128, @bitCast(an)), @as(u128, @bitCast(bn)), &r);
39    return (@as(i128, @bitCast(r)) ^ s_a) -% s_a; // negate if s == -1
40}
41
42test {
43    _ = @import("modti3_test.zig");
44}