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.

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Test issue2761

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  $ hg init

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  $ touch to-be-deleted

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  $ hg add

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  adding to-be-deleted

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  $ hg ci -m first

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  $ echo a > to-be-deleted

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  $ hg ci -m second

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  $ rm to-be-deleted

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  $ hg diff -r 0

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Same issue, different code path

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  $ hg up -C

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  1 files updated, 0 files merged, 0 files removed, 0 files unresolved

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  $ touch does-not-exist-in-1

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  $ hg add

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  adding does-not-exist-in-1

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  $ hg ci -m third

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  $ rm does-not-exist-in-1

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  $ hg diff -r 1