void foo (double * __restrict a, long * __restrict b, double * c)
for (int i = 0; i < 1024; ++i)
a[2*i] = c[b[2*i]];
a[2*i + 1] = c[b[2*i + 1]];
is not SLP vectorized.
"easiest" to do with the IFN scheme since then SLP discovery already sees IFN_GATHERs as discovered by pattern recog.
Created attachment 51504 [details]
A start, lacks adjustment of the code generation part which doesn't expect SLP at the moment.
The master branch has been updated by Richard Sandiford <email@example.com>:
Author: Richard Sandiford <firstname.lastname@example.org>
Date: Tue Nov 30 09:52:29 2021 +0000
vect: Support gather loads with SLP
This patch adds SLP support for IFN_GATHER_LOAD. Like the SLP
support for IFN_MASK_LOAD, it works by treating only some of the
arguments as child nodes. Unlike IFN_MASK_LOAD, it requires the
other arguments (base, scale, and extension type) to be the same
for all calls in the group. It does not require/expect the loads
to be in a group (which probably wouldn't make sense for gathers).
I was worried about the possible alias effect of moving gathers
around to be part of the same SLP group. The patch therefore
makes vect_analyze_data_ref_dependence treat gathers and scatters
as a top-level concern, punting if the accesses aren't completely
independent and if the user hasn't told us that a particular
VF is safe. I think in practice we already punted in the same
circumstances; the idea is just to make it more explicit.
* doc/sourcebuild.texi (vect_gather_load_ifn): Document.
* tree-vect-data-refs.c (vect_analyze_data_ref_dependence):
Commonize safelen handling. Punt for anything involving
gathers and scatters unless safelen says otherwise.
* tree-vect-slp.c (arg1_map): New variable.
(vect_get_operand_map): Handle IFN_GATHER_LOAD.
(compatible_calls_p): If vect_get_operand_map returns nonnull,
check that any skipped arguments are equal.
(vect_slp_analyze_node_operations_1): Tighten reduction check.
* tree-vect-stmts.c (check_load_store_for_partial_vectors): Take
an ncopies argument.
(vect_get_gather_scatter_ops): Take slp_node and ncopies arguments.
Handle SLP nodes.
(vectorizable_store, vectorizable_load): Adjust accordingly.
(check_effective_target_vect_gather_load_ifn): New target test.
* gcc.dg/vect/vect-gather-1.c: New test.
* gcc.dg/vect/vect-gather-2.c: Likewise.
* gcc.target/aarch64/sve/gather_load_11.c: Likewise.
Fixed for IFNs. Not sure whether we want to keep this open for
the built-in route too.
On Tue, 30 Nov 2021, rsandifo at gcc dot gnu.org wrote:
> rsandifo at gcc dot gnu.org <rsandifo at gcc dot gnu.org> changed:
> What |Removed |Added
> CC| |rsandifo at gcc dot gnu.org
> --- Comment #5 from rsandifo at gcc dot gnu.org <rsandifo at gcc dot gnu.org> ---
> Fixed for IFNs. Not sure whether we want to keep this open for
> the built-in route too.
I don't think so. The fix for the built-in route is to get rid of it.
Of course I miserably failed at that - meh :/
OK, closing as fixed then :-)