------- Comment #1 from dorit at gcc dot gnu dot org 2007-07-19 18:15 -------
...
> Though the last add is extra and does not need to be done, we can get rid of
> it
> by having vect_var_.36 being set initially to {e, 0, 0, 0} .
The problem is that often initializing a vector to {e, 0, 0, 0} is (much?) more
expensive than initializing a vector to {0, 0, 0, 0} and then adding e to the
final scalar result. We actually had both options in the vectorizer for a while
(guarded by ADJUST_IN_EPILOG hard-coded #define), however we didn't know how to
choose between the two options (cost wise), so we just arbitrarily chose one.
Now that we're starting to build a cost model we may try to evaluate which of
the two options to generate.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=32825
