[patch] (4.1 project list, stage 1.1) vectorizer alignment improvements

[Dorit Naishlos]

Richard Henderson <rth@gcc.gnu.org> wrote on 14/03/2005 16:03:18:
> On Sun, Mar 13, 2005 at 04:36:30PM +0200, Dorit Naishlos wrote:
> >       * tree-vectorizer.h (unknown_alignment_for_access_p): Replaced by
> >       known_alignment_for_access_p.
> >   ...
>
> Ok, except,
>
> > + /* Function vect_determine_vectorization_factor
> > +
> > + */
>
> Might want to be a bit more descriptive here.
>

:-)

ok with this?:

+ /* Function vect_determine_vectorization_factor
+
+    Determine the vectorization factor (VF). VF is the number of data
elements
+    that are operated upon in parallel in a single iteration of the
vectorized
+    loop. For example, when vectorizing a loop that operates on 4byte
elements,
+    on a target with vector size (VS) 16byte, the VF is set to 4, since 4
+    elements can fit in a single vector register.
+
+    We currently support vectorization of loops in which all types
operated upon
+    are of the same size. Therefore this function currently sets VF
according to
+    the size of the types operated upon, and fails if there are multiple
sizes
+    in the loop.
+
+    VF is also the factor by which the loop iterations are strip-mined,
e.g.:
+    original loop:
+         for (i=0; i<N; i++){
+           a[i] = b[i] + c[i];
+         }
+
+    vectorized loop:
+         for (i=0; i<N; i+=VF){
+           a[i:VF] = b[i:VF] + c[i:VF];
+         }
+
+ */


thanks,
dorit

>
> r~