aboutsummaryrefslogtreecommitdiff
path: root/lib/extable.c
diff options
context:
space:
mode:
authorEric Dumazet <dada1@cosmosbay.com>2008-02-06 01:37:49 -0800
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2008-02-06 10:41:08 -0800
commit15ae02baf025750cd79ef3929c28f7083a088bd2 (patch)
tree9c79b44e5ec865ff62a451bb6e4882d3f4d5b060 /lib/extable.c
parentf63fd7e299ee13da071ecfce2b90b58c5e1562b1 (diff)
downloadlinux-15ae02baf025750cd79ef3929c28f7083a088bd2.tar.gz
lib/extable.c: remove an expensive integer divide in search_extable()
Actual code let compiler generates idiv instruction on x86. Using a right shift is OK here and readable as well. Before patch 10: 57 push %edi 11: 56 push %esi 12: 89 d6 mov %edx,%esi 14: 53 push %ebx 15: 89 c3 mov %eax,%ebx 17: eb 22 jmp 3b <search_extable+0x2b> 19: 89 f0 mov %esi,%eax 1b: ba 02 00 00 00 mov $0x2,%edx 20: 29 d8 sub %ebx,%eax 22: 89 d7 mov %edx,%edi 24: c1 f8 03 sar $0x3,%eax 27: 99 cltd 28: f7 ff idiv %edi 2a: 8d 04 c3 lea (%ebx,%eax,8),%eax 2d: 39 08 cmp %ecx,(%eax) ... After patch 00000010 <search_extable>: 10: 53 push %ebx 11: 89 c3 mov %eax,%ebx 13: eb 18 jmp 2d <search_extable+0x1d> 15: 89 d0 mov %edx,%eax 17: 29 d8 sub %ebx,%eax 19: c1 f8 04 sar $0x4,%eax 1c: 8d 04 c3 lea (%ebx,%eax,8),%eax 1f: 39 08 cmp %ecx,(%eax) ... Signed-off-by: Eric Dumazet <dada1@cosmosbay.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'lib/extable.c')
-rw-r--r--lib/extable.c6
1 files changed, 3 insertions, 3 deletions
diff --git a/lib/extable.c b/lib/extable.c
index 463f4560f16..179c0874559 100644
--- a/lib/extable.c
+++ b/lib/extable.c
@@ -57,10 +57,10 @@ search_extable(const struct exception_table_entry *first,
while (first <= last) {
const struct exception_table_entry *mid;
- mid = (last - first) / 2 + first;
+ mid = ((last - first) >> 1) + first;
/*
- * careful, the distance between entries can be
- * larger than 2GB:
+ * careful, the distance between value and insn
+ * can be larger than MAX_LONG:
*/
if (mid->insn < value)
first = mid + 1;