On Thu, Sep 12, 2013 at 10:31 PM, Xinliang David Li <davi...@google.com> wrote:
> Currently -ftree-vectorize turns on both loop and slp vectorizations,
> but there is no simple way to turn on loop vectorization alone. The
> logic for default O3 setting is also complicated.
>
> In this patch, two new options are introduced:
>
> 1) -ftree-loop-vectorize
>
> This option is used to turn on loop vectorization only. option
> -ftree-slp-vectorize also becomes a first class citizen, and no funny
> business of Init(2) is needed. With this change, -ftree-vectorize
> becomes a simple alias to -ftree-loop-vectorize +
> -ftree-slp-vectorize.
>
> For instance, to turn on only slp vectorize at O3, the old way is:
>
> -O3 -fno-tree-vectorize -ftree-slp-vectorize
>
> With the new change it becomes:
>
> -O3 -fno-loop-vectorize
>
>
> To turn on only loop vectorize at O2, the old way is
>
> -O2 -ftree-vectorize -fno-slp-vectorize
>
> The new way is
>
> -O2 -ftree-loop-vectorize
>
>
>
> 2) -ftree-vect-loop-peeling
>
> This option is used to turn on/off loop peeling for alignment. In the
> long run, this should be folded into the cheap cost model proposed by
> Richard. This option is also useful in scenarios where peeling can
> introduce runtime problems:
> http://gcc.gnu.org/ml/gcc/2005-12/msg00390.html which happens to be
> common in practice.
>
>
>
> Patch attached. Compiler boostrapped. Ok after testing?
I'd like you to split 1) and 2), mainly because I agree on 1) but not on 2).
I've stopped a quick try doing 1) myself because
@@ -1691,6 +1695,12 @@ common_handle_option (struct gcc_options
opts->x_flag_ipa_reference = false;
break;
+ case OPT_ftree_vectorize:
+ if (!opts_set->x_flag_tree_loop_vectorize)
+ opts->x_flag_tree_loop_vectorize = value;
+ if (!opts_set->x_flag_tree_slp_vectorize)
+ opts->x_flag_tree_slp_vectorize = value;
+ break;
doesn't look obviously correct. Does that handle
-ftree-vectorize -fno-tree-loop-vectorize -ftree-vectorize
or
-ftree-loop-vectorize -fno-tree-vectorize
properly? Currently at least
-ftree-slp-vectorize -fno-tree-vectorize
doesn't "work".
That said, the option machinery doesn't handle an option being an alias
for two other options, so it's mechanism to contract positives/negatives
doesn't work here and the override hooks do not work reliably for
repeated options.
Or am I wrong here? Should we care at all? Joseph?
Thanks,
Richard.
>
> thanks,
>
> David
