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.

gcc/
	PR tree-optimization/102467
	* 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.
	(vect_build_slp_tree_1): Likewise.
	(vect_build_slp_tree_2): Likewise.
	(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.

gcc/testsuite/
	* lib/target-supports.exp
	(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.

1 files changed, 14 insertions, 12 deletions

diff --git a/gcc/tree-vect-stmts.c b/gcc/tree-vect-stmts.c
index 101f61f..06da5a9 100644
--- a/gcc/tree-vect-stmts.c
+++ b/gcc/tree-vect-stmts.c
@@ -1674,6 +1674,7 @@ check_load_store_for_partial_vectors (loop_vec_info loop_vinfo, tree vectype,
 				      int group_size,
 				      vect_memory_access_type
 				      memory_access_type,
+				      unsigned int ncopies,
 				      gather_scatter_info *gs_info,
 				      tree scalar_mask)
 {
@@ -1698,7 +1699,6 @@ check_load_store_for_partial_vectors (loop_vec_info loop_vinfo, tree vectype,
 	  LOOP_VINFO_CAN_USE_PARTIAL_VECTORS_P (loop_vinfo) = false;
 	  return;
 	}
-      unsigned int ncopies = vect_get_num_copies (loop_vinfo, vectype);
       vect_record_loop_mask (loop_vinfo, masks, ncopies, vectype, scalar_mask);
       return;
     }
@@ -1721,7 +1721,6 @@ check_load_store_for_partial_vectors (loop_vec_info loop_vinfo, tree vectype,
 	  LOOP_VINFO_CAN_USE_PARTIAL_VECTORS_P (loop_vinfo) = false;
 	  return;
 	}
-      unsigned int ncopies = vect_get_num_copies (loop_vinfo, vectype);
       vect_record_loop_mask (loop_vinfo, masks, ncopies, vectype, scalar_mask);
       return;
     }
@@ -2963,6 +2962,7 @@ vect_build_gather_load_calls (vec_info *vinfo, stmt_vec_info stmt_info,
 static void
 vect_get_gather_scatter_ops (loop_vec_info loop_vinfo,
 			     class loop *loop, stmt_vec_info stmt_info,
+			     slp_tree slp_node, unsigned int ncopies,
 			     gather_scatter_info *gs_info,
 			     tree *dataref_ptr, vec<tree> *vec_offset)
 {
@@ -2975,10 +2975,12 @@ vect_get_gather_scatter_ops (loop_vec_info loop_vinfo,
       new_bb = gsi_insert_seq_on_edge_immediate (pe, stmts);
       gcc_assert (!new_bb);
     }
-  unsigned ncopies = vect_get_num_copies (loop_vinfo, gs_info->offset_vectype);
-  vect_get_vec_defs_for_operand (loop_vinfo, stmt_info, ncopies,
-				 gs_info->offset, vec_offset,
-				 gs_info->offset_vectype);
+  if (slp_node)
+    vect_get_slp_defs (SLP_TREE_CHILDREN (slp_node)[0], vec_offset);
+  else
+    vect_get_vec_defs_for_operand (loop_vinfo, stmt_info, ncopies,
+				   gs_info->offset, vec_offset,
+				   gs_info->offset_vectype);
 }
 
 /* Prepare to implement a grouped or strided load or store using
@@ -7484,7 +7486,7 @@ vectorizable_store (vec_info *vinfo,
 	  && LOOP_VINFO_CAN_USE_PARTIAL_VECTORS_P (loop_vinfo))
 	check_load_store_for_partial_vectors (loop_vinfo, vectype, vls_type,
 					      group_size, memory_access_type,
-					      &gs_info, mask);
+					      ncopies, &gs_info, mask);
 
       if (slp_node
 	  && !vect_maybe_update_slp_op_vectype (SLP_TREE_CHILDREN (slp_node)[0],
@@ -8147,8 +8149,8 @@ vectorizable_store (vec_info *vinfo,
 	  else if (STMT_VINFO_GATHER_SCATTER_P (stmt_info))
 	    {
 	      vect_get_gather_scatter_ops (loop_vinfo, loop, stmt_info,
-					   &gs_info, &dataref_ptr,
-					   &vec_offsets);
+					   slp_node, ncopies, &gs_info,
+					   &dataref_ptr, &vec_offsets);
 	      vec_offset = vec_offsets[0];
 	    }
 	  else
@@ -8827,7 +8829,7 @@ vectorizable_load (vec_info *vinfo,
 	  && LOOP_VINFO_CAN_USE_PARTIAL_VECTORS_P (loop_vinfo))
 	check_load_store_for_partial_vectors (loop_vinfo, vectype, VLS_LOAD,
 					      group_size, memory_access_type,
-					      &gs_info, mask);
+					      ncopies, &gs_info, mask);
 
       if (dump_enabled_p ()
 	  && memory_access_type != VMAT_ELEMENTWISE
@@ -9445,8 +9447,8 @@ vectorizable_load (vec_info *vinfo,
 	  else if (STMT_VINFO_GATHER_SCATTER_P (stmt_info))
 	    {
 	      vect_get_gather_scatter_ops (loop_vinfo, loop, stmt_info,
-					   &gs_info, &dataref_ptr,
-					   &vec_offsets);
+					   slp_node, ncopies, &gs_info,
+					   &dataref_ptr, &vec_offsets);
 	    }
 	  else
 	    dataref_ptr