On Fri, Sep 06, 2024 at 01:46:01PM +0000, Jennifer Schmitz wrote:
> In the pattern X - (X / Y) * Y to X % Y, this patch guards the
> simplification for vector types by a check for:
> 1) Support of the mod optab for vectors OR
> 2) Application during early gimple passes (using PROP_gimple_any).
> This is to prevent reverting vectorization of modulo to div/mult/sub
> if the target does not support vector mod optab, while still allowing
> the simplification during early gimple passes (as tested, for example,
> in gcc.dg/fold-minus-1.c).
>
> The patch was bootstrapped and regtested on aarch64-linux-gnu, no regression.
> OK for mainline?
>
> Signed-off-by: Jennifer Schmitz <jschm...@nvidia.com>
>
> gcc/
> PR tree-optimization/116569
> * generic-match-head.cc (optimize_early_gimple_p): Add inline
> function with mask for early gimple passes.
> * gimple-match-head.cc (optimize_early_gimple_p): Likewise.
> * match.pd: Guard simplification to trunc_mod with check for
> mod optab support.
>
> gcc/testsuite/
> PR tree-optimization/116569
> * gcc.dg/torture/pr116569.c: New test.
This is certainly wrong.
PROP_gimple_any is set already at the end of gimplification, so certainly
doesn't include any other early gimple passes.
And, not all statements are folded during gimplification, e.g. in OpenMP
regions folding is postponed until the omp lowering pass and folded only
there (at which point PROP_gimple_any is already set).
What exactly are you trying to ensure this optimization goes before?
For non-VL vectors I guess vector lowering, but that is done far later
and we already have a different predicate for that.
For VL vectors, what transforms that if user write % ?
Jakub
