https://gcc.gnu.org/bugzilla/show_bug.cgi?id=117379
Avinash Jayakar <avinashd at gcc dot gnu.org> changed:
What |Removed |Added
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CC| |rguenth at gcc dot gnu.org
--- Comment #6 from Avinash Jayakar <avinashd at gcc dot gnu.org> ---
(In reply to Richard Biener from comment #5)
> Yes, we currently are not set up to vectorize multiple pieces of the
> reduction separately (and we still don't handle the MINUS, also not if
> that were uniform). Both is not difficult, it just requires some extra
> bookkeeping.
>
> For the case above, rather than two .REDUC_PLUS I'd do
>
> vector_a = *a;
> vector_b = *b;
> sum = vector_a + vector_b;
> .REDUC_PLUS (sum);
>
> so handle it similar as to how we'd vectorize a 8 lane reduction. The
> 'sum' would be a SLP node with a PLUS operation created by SLP reduction
> discovery when it discovers more than one (same size!) reduction part.
> Having two separate .REDUC_PLUS requires more surgery - like creating
> more than one SLP instance and using separate root stmts which would
> be an 'alternate' scalar input for the other SLP reduction instance.
Trying it with option 1, with one .REDUC_PLUS (sum).
As this improvement was added in
https://gcc.gnu.org/cgit/gcc/commit/?id=3adb3325954177939d59031055fc08a81ae21be3
In similar lines is it possible to recursively call vect_build_slp_instance for
the rest of the statements instead of pushing it to scalar remain. For e.g.,
If the n_matching array is
4 0 0 0 4 0 0 0
for
_4 = MEM[(u32 *)a_10(D) + 12B];
_3 = MEM[(u32 *)a_10(D) + 8B];
_2 = MEM[(u32 *)a_10(D) + 4B];
_1 = *a_10(D);
_8 = MEM[(u32 *)b_14(D) + 12B];
_7 = MEM[(u32 *)b_14(D) + 8B];
_5 = *b_14(D);
_6 = MEM[(u32 *)b_14(D) + 4B];
try vect_build_slp_instance for both groups instead of largest (since they are
same size)?
