[PATCH] backend: compare word-at-a-time in bcTruelen

Signed-off-by: Jeremy Kerr <jk(at)ozlabs(dot)org>

---
src/backend/utils/adt/varchar.c | 24 +++++++++++++++++++++---
1 file changed, 21 insertions(+), 3 deletions(-)

diff --git a/src/backend/utils/adt/varchar.c b/src/backend/utils/adt/varchar.c
index 5f3c658..6889dff 100644
--- a/src/backend/utils/adt/varchar.c
+++ b/src/backend/utils/adt/varchar.c
@@ -624,16 +624,34 @@ varchartypmodout(PG_FUNCTION_ARGS)
static int
bcTruelen(BpChar *arg)
{
+ const unsigned int spaces = 0x20202020;
+ const int wordsize = sizeof(spaces);
char *s = VARDATA_ANY(arg);
int i;
- int len;

- len = VARSIZE_ANY_EXHDR(arg);
- for (i = len - 1; i >= 0; i--)
+ i = VARSIZE_ANY_EXHDR(arg) - 1;
+
+ /* compare down to an aligned boundary */
+ for (; i >= 0 && i % wordsize != wordsize - 1; i--)
{
if (s[i] != ' ')
+ return i + 1;
+ }
+
+ /* now that we're aligned, compare word at a time */
+ for (; i >= wordsize - 1; i -= wordsize)
+ {
+ if (*(unsigned int *)(s + i - (wordsize - 1)) != spaces)
break;
}
+
+ /* check within the last non-matching word */
+ for (; i >= 0; i--)
+ {
+ if (s[i] != ' ')
+ break;
+ }
+
return i + 1;
}