Re: [PATCH][RFC] tree-optimization/92335 - Improve sinking heuristics for vectorization

[Jeff Law <jeffreyalaw@gmail.com>]

On 7/28/23 01:05, Richard Biener via Gcc-patches wrote:
> The following delays sinking of loads within the same innermost
> loop when it was unconditional before.  That's a not uncommon
> issue preventing vectorization when masked loads are not available.
> 
> Bootstrapped and tested on x86_64-unknown-linux-gnu.
> 
> I have a followup patch improving sinking that without this would
> cause more of the problematic sinking - now that we have a second
> sink pass after loop opts this looks like a reasonable approach?
> 
> OK?
> 
> Thanks,
> Richard.
> 
> 	PR tree-optimization/92335
> 	* tree-ssa-sink.cc (select_best_block): Before loop
> 	optimizations avoid sinking unconditional loads/stores
> 	in innermost loops to conditional executed places.
> 
> 	* gcc.dg/tree-ssa/ssa-sink-10.c: Disable vectorizing.
> 	* gcc.dg/tree-ssa/predcom-9.c: Clone from ssa-sink-10.c,
> 	expect predictive commoning to happen instead of sinking.
> 	* gcc.dg/vect/pr65947-3.c: Adjust.
I think it's reasonable -- there's probably going to be cases where it's 
not great, but more often than not I think it's going to be a reasonable 
heuristic.

If there is undesirable fallout, better to find it over the coming 
months than next spring.  So I'd suggest we go forward now to give more 
time to find any pathological cases (if they exist).

Jeff