code generate live lanes in basic-block vectorization

code generate live lanes in basic-block vectorization

The following adds the capability to code-generate live lanes in
basic-block vectorization using lane extracts from vector stmts
rather than keeping the original scalar code around for those.
This eventually makes previously not profitable vectorizations
profitable (the live scalar code was appropriately costed so
are the lane extracts now), without considering the cost model
this patch doesn't add or remove any basic-block vectorization
capabilities.

The patch re/ab-uses STMT_VINFO_LIVE_P in basic-block vectorization
mode to tell whether a live lane is vectorized or whether it is
provided by means of keeping the scalar code live.

The patch is a first step towards vectorizing sequences of
stmts that do not end up in stores or vector constructors though.

Bootstrapped and tested on x86_64-unknown-linux-gnu.

2020-09-04  Richard Biener  <rguenther@suse.de>

	* tree-vectorizer.h (vectorizable_live_operation): Adjust.
	* tree-vect-loop.c (vectorizable_live_operation): Vectorize
	live lanes out of basic-block vectorization nodes.
	* tree-vect-slp.c (vect_bb_slp_mark_live_stmts): New function.
	(vect_slp_analyze_operations): Analyze live lanes and their
	vectorization possibility after the whole SLP graph is final.
	(vect_bb_slp_scalar_cost): Adjust for vectorized live lanes.
	* tree-vect-stmts.c (can_vectorize_live_stmts): Adjust.
	(vect_transform_stmt): Call can_vectorize_live_stmts also for
	basic-block vectorization.

	* gcc.dg/vect/bb-slp-46.c: New testcase.
	* gcc.dg/vect/bb-slp-47.c: Likewise.
	* gcc.dg/vect/bb-slp-32.c: Adjust.