On Tue, Oct 29, 2019 at 6:04 PM Richard Sandiford
<richard.sandif...@arm.com> wrote:
>
> If the statements in an SLP node aren't similar enough to be vectorised,
> or aren't something the vectoriser has code to handle, the BB vectoriser
> tries building the vector from scalars instead. This patch does the
> same thing if we're able to build a viable-looking tree but fail later
> during the analysis phase, e.g. because the target doesn't support a
> particular vector operation.
>
> This is needed to avoid regressions with a later patch.
OK.
Thanks,
Richard.
>
> 2019-10-29 Richard Sandiford <richard.sandif...@arm.com>
>
> gcc/
> * tree-vect-slp.c (vect_contains_pattern_stmt_p): New function.
> (vect_slp_convert_to_external): Likewise.
> (vect_slp_analyze_node_operations): If analysis fails, try building
> the node from scalars instead.
>
> gcc/testsuite/
> * gcc.dg/vect/bb-slp-div-2.c: New test.
>
> Index: gcc/tree-vect-slp.c
> ===================================================================
> --- gcc/tree-vect-slp.c 2019-10-29 17:01:46.000000000 +0000
> +++ gcc/tree-vect-slp.c 2019-10-29 17:02:06.355512105 +0000
> @@ -225,6 +225,19 @@ vect_free_oprnd_info (vec<slp_oprnd_info
> }
>
>
> +/* Return true if STMTS contains a pattern statement. */
> +
> +static bool
> +vect_contains_pattern_stmt_p (vec<stmt_vec_info> stmts)
> +{
> + stmt_vec_info stmt_info;
> + unsigned int i;
> + FOR_EACH_VEC_ELT (stmts, i, stmt_info)
> + if (is_pattern_stmt_p (stmt_info))
> + return true;
> + return false;
> +}
> +
> /* Find the place of the data-ref in STMT_INFO in the interleaving chain
> that starts from FIRST_STMT_INFO. Return -1 if the data-ref is not a part
> of the chain. */
> @@ -2630,6 +2643,39 @@ vect_slp_analyze_node_operations_1 (vec_
> return vect_analyze_stmt (stmt_info, &dummy, node, node_instance,
> cost_vec);
> }
>
> +/* Try to build NODE from scalars, returning true on success.
> + NODE_INSTANCE is the SLP instance that contains NODE. */
> +
> +static bool
> +vect_slp_convert_to_external (vec_info *vinfo, slp_tree node,
> + slp_instance node_instance)
> +{
> + stmt_vec_info stmt_info;
> + unsigned int i;
> +
> + if (!is_a <bb_vec_info> (vinfo)
> + || node == SLP_INSTANCE_TREE (node_instance)
> + || vect_contains_pattern_stmt_p (SLP_TREE_SCALAR_STMTS (node)))
> + return false;
> +
> + if (dump_enabled_p ())
> + dump_printf_loc (MSG_NOTE, vect_location,
> + "Building vector operands from scalars instead\n");
> +
> + /* Don't remove and free the child nodes here, since they could be
> + referenced by other structures. The analysis and scheduling phases
> + (need to) ignore child nodes of anything that isn't vect_internal_def.
> */
> + unsigned int group_size = SLP_TREE_SCALAR_STMTS (node).length ();
> + SLP_TREE_DEF_TYPE (node) = vect_external_def;
> + SLP_TREE_SCALAR_OPS (node).safe_grow (group_size);
> + FOR_EACH_VEC_ELT (SLP_TREE_SCALAR_STMTS (node), i, stmt_info)
> + {
> + tree lhs = gimple_get_lhs (vect_orig_stmt (stmt_info)->stmt);
> + SLP_TREE_SCALAR_OPS (node)[i] = lhs;
> + }
> + return true;
> +}
> +
> /* Analyze statements contained in SLP tree NODE after recursively analyzing
> the subtree. NODE_INSTANCE contains NODE and VINFO contains INSTANCE.
>
> @@ -2656,6 +2702,13 @@ vect_slp_analyze_node_operations (vec_in
> {
> SLP_TREE_NUMBER_OF_VEC_STMTS (node)
> = SLP_TREE_NUMBER_OF_VEC_STMTS (*leader);
> + /* Cope with cases in which we made a late decision to build the
> + node from scalars. */
> + if (SLP_TREE_DEF_TYPE (*leader) == vect_external_def
> + && vect_slp_convert_to_external (vinfo, node, node_instance))
> + ;
> + else
> + gcc_assert (SLP_TREE_DEF_TYPE (node) == SLP_TREE_DEF_TYPE (*leader));
> return true;
> }
>
> @@ -2715,6 +2768,11 @@ vect_slp_analyze_node_operations (vec_in
> if (SLP_TREE_SCALAR_STMTS (child).length () != 0)
> STMT_VINFO_DEF_TYPE (SLP_TREE_SCALAR_STMTS (child)[0]) = dt[j];
>
> + /* If this node can't be vectorized, try pruning the tree here rather
> + than felling the whole thing. */
> + if (!res && vect_slp_convert_to_external (vinfo, node, node_instance))
> + res = true;
> +
> return res;
> }
>
> Index: gcc/testsuite/gcc.dg/vect/bb-slp-div-2.c
> ===================================================================
> --- /dev/null 2019-09-17 11:41:18.176664108 +0100
> +++ gcc/testsuite/gcc.dg/vect/bb-slp-div-2.c 2019-10-29 17:02:06.351512133
> +0000
> @@ -0,0 +1,14 @@
> +/* { dg-do compile } */
> +
> +int x[4], y[4], z[4];
> +
> +void
> +f (void)
> +{
> + x[0] += y[0] / z[0] * 2;
> + x[1] += y[1] / z[1] * 2;
> + x[2] += y[2] / z[2] * 2;
> + x[3] += y[3] / z[3] * 2;
> +}
> +
> +/* { dg-final { scan-tree-dump "basic block vectorized" "slp2" { target
> vect_int } } } */
