sctp: improve how SSN, TSN and ASCONF serial are compared
Make it similar to time_before() macros:
- easier to understand
- make use of typecheck() to avoid working on unexpected variable types
(made the issue on previous patch visible)
- for _[lg]te versions, slighly faster, as the compiler used to generate
a sequence of cmp/je/cmp/js instructions and now it's sub/test/jle
(for _lte):
Before, for sctp_outq_sack:
if (primary->cacc.changeover_active) {
1f01: 80 b9 84 02 00 00 00 cmpb $0x0,0x284(%rcx)
1f08: 74 6e je 1f78 <sctp_outq_sack+0xe8>
u8 clear_cycling = 0;
if (TSN_lte(primary->cacc.next_tsn_at_change, sack_ctsn)) {
1f0a: 8b 81 80 02 00 00 mov 0x280(%rcx),%eax
return ((s) - (t)) & TSN_SIGN_BIT;
}
static inline int TSN_lte(__u32 s, __u32 t)
{
return ((s) == (t)) || (((s) - (t)) & TSN_SIGN_BIT);
1f10: 8b 7d bc mov -0x44(%rbp),%edi
1f13: 39 c7 cmp %eax,%edi
1f15: 74 25 je 1f3c <sctp_outq_sack+0xac>
1f17: 39 f8 cmp %edi,%eax
1f19: 78 21 js 1f3c <sctp_outq_sack+0xac>
primary->cacc.changeover_active = 0;
After:
if (primary->cacc.changeover_active) {
1ee7: 80 b9 84 02 00 00 00 cmpb $0x0,0x284(%rcx)
1eee: 74 73 je 1f63 <sctp_outq_sack+0xf3>
u8 clear_cycling = 0;
if (TSN_lte(primary->cacc.next_tsn_at_change, sack_ctsn)) {
1ef0: 8b 81 80 02 00 00 mov 0x280(%rcx),%eax
1ef6: 2b 45 b4 sub -0x4c(%rbp),%eax
1ef9: 85 c0 test %eax,%eax
1efb: 7e 26 jle 1f23 <sctp_outq_sack+0xb3>
primary->cacc.changeover_active = 0;
*_lt() generated pretty much the same code.
Tested with gcc (GCC) 6.1.1 20160621.
This patch also removes SSN_lte as it is not used and cleanups some
comments.
Signed-off-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
1 file changed