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.
# RelaxNG schema for "xml" log style
# Inspired by Subversion's XML log format.
start = log
node.type = xsd:string {minLength = "40" maxLength = "40"}
log = element log { logentry+ }
logentry = element logentry {
logentry.attlist,
branch*, tag*, hgparent*,
author, date,
msg, paths?, copies?, extra*
}
logentry.attlist =
attribute revision {xsd:nonNegativeInteger}
& attribute node {node.type}
branch = element branch { text }
tag = element tag { text }
hgparent = element parent {hgparent.attlist, text}
hgparent.attlist =
attribute revision {xsd:integer {minInclusive = "-1"} }
& attribute node {node.type}
author = element author { author.attlist, text }
author.attlist =
attribute email {text}
date = element date {xsd:dateTime}
msg = element msg {msg.attlist, text}
msg.attlist =
attribute xml:space {"preserve"}
paths = element paths { path* }
path = element path { path.attlist, text }
path.attlist =
# Action: (A)dd, (M)odify, (R)emove
attribute action {"A"|"M"|"R"}
copies = element copies { copy+ }
copy = element copy { copy.attlist, text }
copy.attlist =
attribute source {text}
extra = element extra {extra.attlist, text}
extra.attlist =
attribute key {text}