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, 1 insertions, 7 deletions

diff --git a/rts/Sparks.c b/rts/Sparks.c
index a826190941..18d9597ec2 100644
--- a/rts/Sparks.c
+++ b/rts/Sparks.c
@@ -63,13 +63,7 @@ newSpark (StgRegTable *reg, StgClosure *p)
     Capability *cap = regTableToCapability(reg);
     SparkPool *pool = cap->sparks;
 
-    /* I am not sure whether this is the right thing to do.
-     * Maybe it is better to exploit the tag information
-     * instead of throwing it away?
-     */
-    p = UNTAG_CLOSURE(p);
-
-    if (closure_SHOULD_SPARK(p)) {
+    if (!fizzledSpark(p)) {
         pushWSDeque(pool,p);
         cap->sparks_created++;
     } else {