1 files changed, 27 insertions, 0 deletions
diff --git a/lib/std/special/compiler_rt/popcountdi2_test.zig b/lib/std/special/compiler_rt/popcountdi2_test.zig
new file mode 100644
index 0000000000..bedcbcd1de
--- /dev/null
+++ b/lib/std/special/compiler_rt/popcountdi2_test.zig
@@ -0,0 +1,27 @@
+const __popcountdi2 = @import("popcountdi2.zig").__popcountdi2;
+const testing = @import("std").testing;
+
+fn naive_popcount(a_param: i64) i32 {
+    var a = a_param;
+    var r: i32 = 0;
+    while (a != 0) : (a = @bitCast(i64, @bitCast(u64, a) >> 1)) {
+        r += @intCast(i32, a & 1);
+    }
+    return r;
+}
+
+fn test__popcountdi2(a: i64) void {
+    const x = __popcountdi2(a);
+    const expected = naive_popcount(a);
+    testing.expect(expected == x);
+}
+
+test "popcountdi2" {
+    test__popcountdi2(0);
+    test__popcountdi2(1);
+    test__popcountdi2(2);
+    test__popcountdi2(@bitCast(i64, u64(0xFFFFFFFFFFFFFFFD)));
+    test__popcountdi2(@bitCast(i64, u64(0xFFFFFFFFFFFFFFFE)));
+    test__popcountdi2(@bitCast(i64, u64(0xFFFFFFFFFFFFFFFF)));
+    // TODO some fuzz testing
+}