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.
https://bz.mercurial-scm.org/672
# 0-2-4
# \ \ \
# 1-3-5
#
# rename in #1, content change in #4.
$ hg init
$ touch 1
$ touch 2
$ hg commit -Am init # 0
adding 1
adding 2
$ hg rename 1 1a
$ hg commit -m rename # 1
$ hg co -C 0
1 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ echo unrelated >> 2
$ hg ci -m unrelated1 # 2
created new head
$ hg merge --debug 1
searching for copies back to rev 1
unmatched files in other:
1a
all copies found (* = to merge, ! = divergent, % = renamed and deleted):
src: '1' -> dst: '1a'
checking for directory renames
resolving manifests
branchmerge: True, force: False, partial: False
ancestor: 81f4b099af3d, local: c64f439569a9+, remote: c12dcd37c90a
1: other deleted -> r
removing 1
1a: remote created -> g
getting 1a
2: remote unchanged -> k
1 files updated, 0 files merged, 1 files removed, 0 files unresolved
(branch merge, don't forget to commit)
$ hg ci -m merge1 # 3
$ hg co -C 2
1 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ echo hello >> 1
$ hg ci -m unrelated2 # 4
created new head
$ hg co -C 3
1 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ hg merge -y --debug 4
searching for copies back to rev 1
unmatched files in local:
1a
all copies found (* = to merge, ! = divergent, % = renamed and deleted):
src: '1' -> dst: '1a' *
checking for directory renames
resolving manifests
branchmerge: True, force: False, partial: False
ancestor: c64f439569a9, local: e327dca35ac8+, remote: 746e9549ea96
preserving 1a for resolve of 1a
starting 4 threads for background file closing (?)
1a: local copied/moved from 1 -> m (premerge)
picked tool ':merge' for 1a (binary False symlink False changedelete False)
merging 1a and 1 to 1a
my 1a@e327dca35ac8+ other 1@746e9549ea96 ancestor 1@c64f439569a9
premerge successful
0 files updated, 1 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)
$ hg co -C 4
1 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ hg merge -y --debug 3
searching for copies back to rev 1
unmatched files in other:
1a
all copies found (* = to merge, ! = divergent, % = renamed and deleted):
src: '1' -> dst: '1a' *
checking for directory renames
resolving manifests
branchmerge: True, force: False, partial: False
ancestor: c64f439569a9, local: 746e9549ea96+, remote: e327dca35ac8
preserving 1 for resolve of 1a
removing 1
starting 4 threads for background file closing (?)
1a: remote moved from 1 -> m (premerge)
picked tool ':merge' for 1a (binary False symlink False changedelete False)
merging 1 and 1a to 1a
my 1a@746e9549ea96+ other 1a@e327dca35ac8 ancestor 1@c64f439569a9
premerge successful
0 files updated, 1 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)