[commit: ghc] master: comments only (9894f6a)

[git at git.haskell.org]

Repository : ssh://git@git.haskell.org/ghc

On branch  : master
Link       : http://ghc.haskell.org/trac/ghc/changeset/9894f6a5b4883ea87fd5f280a2eb4a8abfbd2a6b/ghc

>---------------------------------------------------------------

commit 9894f6a5b4883ea87fd5f280a2eb4a8abfbd2a6b
Author: Simon Marlow <marlowsd at gmail.com>
Date:   Wed Jan 14 08:45:07 2015 +0000

    comments only


>---------------------------------------------------------------

9894f6a5b4883ea87fd5f280a2eb4a8abfbd2a6b
 rts/sm/Scav.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/rts/sm/Scav.c b/rts/sm/Scav.c
index 2ecb23b..781840c 100644
--- a/rts/sm/Scav.c
+++ b/rts/sm/Scav.c
@@ -285,6 +285,8 @@ scavenge_large_srt_bitmap( StgLargeSRT *large_srt )
 
     for (i = 0; i < size / BITS_IN(W_); i++) {
         bitmap = large_srt->l.bitmap[i];
+        // skip zero words: bitmaps can be very sparse, and this helps
+        // performance a lot in some cases.
         if (bitmap != 0) {
             for (j = 0; j < BITS_IN(W_); j++) {
                 if ((bitmap & 1) != 0) {