On Tue, Oct 29, 2024 at 9:24 AM Kugan Vivekanandarajah
<kvivekana...@nvidia.com> wrote:
>
> Hi Richard,
> Thanks for the review.
>
> > On 28 Oct 2024, at 9:18 pm, Richard Biener <richard.guent...@gmail.com>
> > wrote:
> >
> > External email: Use caution opening links or attachments
> >
> >
> > On Mon, Oct 28, 2024 at 9:35 AM Kugan Vivekanandarajah
> > <kvivekana...@nvidia.com> wrote:
> >>
> >> Hi,
> >>
> >> When ifcvt version a loop, it sets dont_vectorize to the scalar loop. If
> >> the
> >> vector loop is not vectorized and removed, the scalar loop is still left
> >> with
> >> dont_vectorize. As a result, BB vectorization will not happen.
> >>
> >> This patch adds a new attribute called dont_loop_vectorize (that is
> >> different
> >> from general dont_vectorize) specifically for loops versioned. BB
> >> vectorization
> >> does not need to honour this and still can vectorize.
> >>
> >> Bootstrapped and regression tested on aarch64-linux-gnu with no new
> >> regressions.
> >>
> >> Is this OK?
> >
> > I believe if-conversion never versions a loop that has
> > ->dont_vectorize set so when
> > the vectorizer elides the .LOOP_VECTORIZED test it can simply clear
> > the flag again.
> >
> > I don't like adding a new flag, instead if the above doesn't work, the
> > vectorizer
> > should be changed how it identifies loop candidates, not relying on this
> > flag.
>
> Here is a version where I am resetting dont_vectorize while folding
> ffold_loop_internal_call with false.
>
> Bootstrapped and regression tested on aarch64-linux-gnu. Is this OK?
Hmm, I'm not sure this way is super reliable given taken_edge->dest
could be a preheader
block. I see we have many calls to fold_loop_internal_call - one is
even suspicious to break
with your patch:
/* If we are going to vectorize outer loop, prevent vectorization
of the inner loop in the scalar loop - either the scalar loop is
thrown away, so it is a wasted work, or is used only for
a few iterations. */
if (scalar_loop->inner)
{
gimple *g = vect_loop_vectorized_call (scalar_loop->inner);
if (g)
{
arg = gimple_call_arg (g, 0);
get_loop (fun, tree_to_shwi (arg))->dont_vectorize = true;
fold_loop_internal_call (g, boolean_false_node);
does it work if you just do
diff --git a/gcc/tree-vectorizer.cc b/gcc/tree-vectorizer.cc
index af112f212fe..16fa0ec1bb7 100644
--- a/gcc/tree-vectorizer.cc
+++ b/gcc/tree-vectorizer.cc
@@ -1326,6 +1326,7 @@ pass_vectorize::execute (function *fun)
if (g)
{
fold_loop_internal_call (g, boolean_false_node);
+ loop->dont_vectorize = false;
ret |= TODO_cleanup_cfg;
g = NULL;
}
@@ -1335,6 +1336,7 @@ pass_vectorize::execute (function *fun)
if (g)
{
fold_loop_internal_call (g, boolean_false_node);
+ loop->dont_vectorize = false;
ret |= TODO_cleanup_cfg;
}
}
?
> Thanks,
> Kugan
>
>
> >
> > Richard.
> >
> >> Thanks,
> >> Kugan
> >>
>
