On Mon, 18 Dec 2023 13:18:14 +0100 Nina Schoetterl-Glausch nsg@linux.ibm.com wrote:
[...]
diff --git a/tools/testing/selftests/kvm/s390x/memop.c b/tools/testing/selftests/kvm/s390x/memop.c index bb3ca9a5d731..2eba9575828e 100644 --- a/tools/testing/selftests/kvm/s390x/memop.c +++ b/tools/testing/selftests/kvm/s390x/memop.c @@ -485,11 +485,13 @@ static bool popcount_eq(__uint128_t a, __uint128_t b) static __uint128_t rotate(int size, __uint128_t val, int amount) {
- unsigned int bits = size * 8;
- unsigned int left, right, bits = size * 8;
...why not just:
if (!amount) return val;
?
That works if you move it one statement down (128 would also trigger UB).
oops, yes it has to be after
% 128 does the trick, is branchless and there is a bit of a symmetry going on between right and left. But I can use an early return if you want.
I think it's more readable, and furthermore...
- amount = (amount + bits) % bits;
- right = (amount + bits) % bits;
- /* % 128 prevents left shift UB if size == 16 && right == 0 */
- left = (bits - right) % 128; val = cut_to_size(size, val);
- return (val << (bits - amount)) | (val >> amount);
...this is a more idiomatic syntax for a rotate operation
- return (val << left) | (val >> right);
} const unsigned int max_block = 16;
base-commit: 305230142ae0637213bf6e04f6d9f10bbcb74af8