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compiler_rt: fix rare case in udivei4

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Unsigned integers are never less than zero, and so zig
helpfully deleted the entire case. :D

Closes #14816
This commit is contained in:
Jacob Young
2023-03-07 02:11:49 -05:00
parent 6218e40046
commit c1d16a2b80
2 changed files with 26 additions and 6 deletions
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12
lib/compiler_rt/udivmodei4.zig
View File

@@ -79,16 +79,16 @@ fn divmod(q: ?[]u32, r: ?[]u32, u: []const u32, v: []const u32) !void {
}
break;
}
var carry: u64 = 0;
var carry: i64 = 0;
i = 0;
while (i <= n) : (i += 1) {
const p = qhat * limb(&vn, i);
const t = limb(&un, i + j) - carry - @truncate(u32, p);
limb_set(&un, i + j, @truncate(u32, t));
carry = @intCast(u64, p >> 32) - @intCast(u64, t >> 32);
limb_set(&un, i + j, @truncate(u32, @bitCast(u64, t)));
carry = @intCast(i64, p >> 32) - @intCast(i64, t >> 32);
}
const t = limb(&un, j + n + 1) - carry;
limb_set(&un, j + n + 1, @truncate(u32, t));
const t = limb(&un, j + n + 1) -% carry;
limb_set(&un, j + n + 1, @truncate(u32, @bitCast(u64, t)));
if (q) |q_| limb_set(q_, j, @truncate(u32, qhat));
if (t < 0) {
if (q) |q_| limb_set(q_, j, limb(q_, j) - 1);
@@ -99,7 +99,7 @@ fn divmod(q: ?[]u32, r: ?[]u32, u: []const u32, v: []const u32) !void {
limb_set(&un, i + j, @truncate(u32, t2));
carry2 = t2 >> 32;
}
limb_set(un, j + n + 1, @truncate(u32, limb(&un, j + n + 1) + carry2));
limb_set(&un, j + n + 1, @truncate(u32, limb(&un, j + n + 1) + carry2));
}
if (j == 0) break;
}

20
test/behavior/int_div.zig
View File

@@ -91,3 +91,23 @@ fn mod(comptime T: type, a: T, b: T) T {
fn rem(comptime T: type, a: T, b: T) T {
return @rem(a, b);
}
test "large integer division" {
if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest;
if (builtin.zig_backend == .stage2_arm) return error.SkipZigTest;
if (builtin.zig_backend == .stage2_c) return error.SkipZigTest;
if (builtin.zig_backend == .stage2_sparc64) return error.SkipZigTest;
if (builtin.zig_backend == .stage2_wasm) return error.SkipZigTest;
if (builtin.zig_backend == .stage2_x86_64) return error.SkipZigTest;
{
var numerator: u256 = 99999999999999999997315645440;
var divisor: u256 = 10000000000000000000000000000;
try expect(numerator / divisor == 9);
}
{
var numerator: u256 = 99999999999999999999000000000000000000000;
var divisor: u256 = 10000000000000000000000000000000000000000;
try expect(numerator / divisor == 9);
}
}