vect: Add bias parameter for partial vectorization

This introduces a bias parameter for the len_load/len_store ifns as well as
optabs that is meant to distinguish between Power and s390 variants.
PowerPC's instructions require a bias of 0, while in s390's case
vll/vstl do not support lengths of zero bytes and a bias of -1 must be used.

gcc/ChangeLog:

	* internal-fn.c (expand_partial_load_optab_fn): Add bias.
	(expand_partial_store_optab_fn): Likewise.
	(internal_len_load_store_bias): New function.
	* internal-fn.h (VECT_PARTIAL_BIAS_UNSUPPORTED): New define.
	(internal_len_load_store_bias): New function.
	* tree-vect-loop-manip.c (vect_set_loop_controls_directly): Set bias.
	(vect_set_loop_condition_partial_vectors): Add header_seq parameter.
	* tree-vect-loop.c (vect_verify_loop_lens): Verify bias.
	(vect_estimate_min_profitable_iters): Account for bias.
	(vect_get_loop_len): Add bias-adjusted length.
	* tree-vect-stmts.c (vectorizable_store): Use.
	(vectorizable_load): Use.
	* tree-vectorizer.h (struct rgroup_controls): Add bias-adjusted length.
	(LOOP_VINFO_PARTIAL_LOAD_STORE_BIAS): New macro.
	* config/rs6000/vsx.md: Use const0 bias predicate.
	* doc/md.texi: Document bias value.

1 files changed, 15 insertions, 0 deletions

diff --git a/gcc/tree-vect-loop-manip.c b/gcc/tree-vect-loop-manip.c
index cdb8789..a7bbc91 100644
--- a/gcc/tree-vect-loop-manip.c
+++ b/gcc/tree-vect-loop-manip.c
@@ -421,6 +421,7 @@ vect_maybe_permute_loop_masks (gimple_seq *seq, rgroup_controls *dest_rgm,
 static tree
 vect_set_loop_controls_directly (class loop *loop, loop_vec_info loop_vinfo,
 				 gimple_seq *preheader_seq,
+				 gimple_seq *header_seq,
 				 gimple_stmt_iterator loop_cond_gsi,
 				 rgroup_controls *rgc, tree niters,
 				 tree niters_skip, bool might_wrap_p)
@@ -664,6 +665,19 @@ vect_set_loop_controls_directly (class loop *loop, loop_vec_info loop_vinfo,
 
       vect_set_loop_control (loop, ctrl, init_ctrl, next_ctrl);
     }
+
+  int partial_load_bias = LOOP_VINFO_PARTIAL_LOAD_STORE_BIAS (loop_vinfo);
+  if (partial_load_bias != 0)
+    {
+      tree adjusted_len = rgc->bias_adjusted_ctrl;
+      gassign *minus = gimple_build_assign (adjusted_len, PLUS_EXPR,
+					    rgc->controls[0],
+					    build_int_cst
+					    (TREE_TYPE (rgc->controls[0]),
+					     partial_load_bias));
+      gimple_seq_add_stmt (header_seq, minus);
+    }
+
   return next_ctrl;
 }
 
@@ -744,6 +758,7 @@ vect_set_loop_condition_partial_vectors (class loop *loop,
 	/* Set up all controls for this group.  */
 	test_ctrl = vect_set_loop_controls_directly (loop, loop_vinfo,
 						     &preheader_seq,
+						     &header_seq,
 						     loop_cond_gsi, rgc,
 						     niters, niters_skip,
 						     might_wrap_p);