Improve the newSpark dud test by using the pointer tag bits

newSpark() checks if the spark is a dud, and if so does not add it to
the spark pool. Previously, newSpark would discard the pointer tag bits
and just check closure_SHOULD_SPARK(p). We can take advantage of the
tag bits which can tell us if the pointer points to a value. If it is,
it's a dud spark and we don't need to add it to the spark pool.

1 files changed, 7 insertions, 0 deletions

diff --git a/rts/Sparks.h b/rts/Sparks.h
index cffe99dd39..d714cb5d09 100644
--- a/rts/Sparks.h
+++ b/rts/Sparks.h
@@ -31,6 +31,8 @@ INLINE_HEADER StgClosure* reclaimSpark(SparkPool *pool);
 INLINE_HEADER rtsBool looksEmpty(SparkPool* deque);
 
 StgClosure * tryStealSpark     (Capability *cap);
+INLINE_HEADER rtsBool      fizzledSpark  (StgClosure *);
+
 void         freeSparkPool     (SparkPool *pool);
 void         createSparkThread (Capability *cap);
 void         traverseSparkQueue(evac_fn evac, void *user, Capability *cap);
@@ -63,6 +65,11 @@ INLINE_HEADER void discardSparks (SparkPool *pool)
     discardElements(pool);
 }
 
+INLINE_HEADER rtsBool fizzledSpark (StgClosure *spark)
+{
+    return (GET_CLOSURE_TAG(spark) != 0 || !closure_SHOULD_SPARK(spark));
+}
+
 #endif // THREADED_RTS
 
 #include "EndPrivate.h"