Re: Strange vect.exp test results

[Ira Rosen <IRAR at il dot ibm dot com>]

gcc-owner@gcc.gnu.org wrote on 30/05/2011 06:36:36 PM:

>
> Hi,
>
> I've been playing with the vectorizer for my port, and of course I use
> the testsuite to check the generated code. I fail to understand some
> of the FAILs I get. For example, in slp-3.c, the test contains:
>
> /* { dg-final { scan-tree-dump-times "vectorized 3 loops" 1 "vect" {
> xfail vect_no_align } } } */
>
> This test fails for me because I get 4 vectorized loops instead of 3.
> There are multiple other tests that generate more vectorization then
> expected. I'd like to understand the reason for these failures, but I
> can't see what motivates the choice of only 3 vectorized loops among
> the 4 vectorizable loops of the test. Can someone enlighten me?

The fourth loop (line 104) has only 3 scalar iterations, too few to
vectorize unless your target has vectors of 2 shorts.

Ira

>
> Many thanks,
> Fred