1const compiler_rt = @import("../compiler_rt.zig");
2const symbol = compiler_rt.symbol;
3const testing = @import("std").testing;
4
5comptime {
6 symbol(&__subvsi3, "__subvsi3");
7}
8
9pub fn __subvsi3(a: i32, b: i32) callconv(.c) i32 {
10 const sum = a -% b;
11 // Overflow occurred iff the operands have opposite signs, and the sign of the
12 // sum is the opposite of the lhs sign.
13 if (((a ^ b) & (sum ^ a)) < 0) @panic("integer overflow");
14 return sum;
15}
16
17test "subvsi3" {
18 // min i32 = -2147483648
19 // max i32 = 2147483647
20 // TODO write panic handler for testing panics
21 // try test__subvsi3(-2147483648, -1, -1); // panic
22 // try test__subvsi3(2147483647, 1, 1); // panic
23 try testing.expectEqual(-2147483648, __subvsi3(-2147483647, 1));
24 try testing.expectEqual(2147483647, __subvsi3(2147483646, -1));
25}