Fix the code to properly detect overflow; the 128 bit signed
product must have all zeroes or all ones in the first 65 bits
otherwise OV should be set.
Example:
R3
45F086A5D5887509
R4
0000000000000002
mulldo 3,3,4
Should set XER[OV].
Signed-off-by: Tom Musta <tommusta@gmail.com>
Signed-off-by: Alexander Graf <agraf@suse.de>
uint64_t tl;
muls64(&tl, (uint64_t *)&th, arg1, arg2);
- /* If th != 0 && th != -1, then we had an overflow */
- if (likely((uint64_t)(th + 1) <= 1)) {
+
+ /* th should either contain all 1 bits or all 0 bits and should
+ * match the sign bit of tl; otherwise we have overflowed. */
+
+ if ((int64_t)tl < 0) {
+ if (likely(th == -1LL)) {
+ env->ov = 0;
+ } else {
+ env->so = env->ov = 1;
+ }
+ } else if (likely(th == 0LL)) {
env->ov = 0;
} else {
env->so = env->ov = 1;
}
+
return (int64_t)tl;
}
#endif