bdiff: don't check border condition in loop This is pretty much a copy of d500ddae7494, just to a different loop. The condition `p == plast` (`plast == a + len - 1`) was only true on the final iteration of the loop. So it was wasteful to check for it on every iteration. We decrease the iteration count by 1 and add an explicit check for `p == plast` after the loop. Again, we see modest wins. From the mozilla-unified repository: $ perfbdiff -m 3041e4d59df2 ! wall 0.035502 comb 0.040000 user 0.040000 sys 0.000000 (best of 100) ! wall 0.030480 comb 0.030000 user 0.030000 sys 0.000000 (best of 100) $ perfbdiff 0e9928989e9c --alldata --count 100 ! wall 4.097394 comb 4.100000 user 4.100000 sys 0.000000 (best of 3) ! wall 3.597798 comb 3.600000 user 3.600000 sys 0.000000 (best of 3) The 2nd example throws a total of ~3.3GB of data at bdiff. This change increases the throughput from ~811 MB/s to ~924 MB/s.

#!/usr/bin/env python
from __future__ import absolute_import, print_function

from mercurial import (
    commands,
    localrepo,
    ui as uimod,
)

u = uimod.ui()

print('% creating repo')
repo = localrepo.localrepository(u, '.', create=True)

f = open('test.py', 'w')
try:
    f.write('foo\n')
finally:
    f.close

print('% add and commit')
commands.add(u, repo, 'test.py')
commands.commit(u, repo, message='*')
commands.status(u, repo, clean=True)


print('% change')
f = open('test.py', 'w')
try:
    f.write('bar\n')
finally:
    f.close()

# this would return clean instead of changed before the fix
commands.status(u, repo, clean=True, modified=True)