re PR target/91522 (STV is slow)

re PR target/91522 (STV is slow)

2019-08-26  Richard Biener  <rguenther@suse.de>

	PR target/91522
	PR target/91527
	* config/i386/i386-features.h (general_scalar_chain::defs_map):
	New member.
	(general_scalar_chain::replace_with_subreg): Remove.
	(general_scalar_chain::replace_with_subreg_in_insn): Likewise.
	(general_scalar_chain::convert_reg): Adjust signature.
	* config/i386/i386-features.c (scalar_chain::add_insn): Do not
	iterate over all defs of a reg.
	(general_scalar_chain::replace_with_subreg): Remove.
	(general_scalar_chain::replace_with_subreg_in_insn): Likewise.
	(general_scalar_chain::make_vector_copies): Populate defs_map,
	place copy only after defs that are used as vectors in the chain.
	(general_scalar_chain::convert_reg): Emit a copy for a specific
	def in a specific instruction.
	(general_scalar_chain::convert_op): All reg uses are converted here.
	(general_scalar_chain::convert_insn): Emit copies for scalar
	uses of defs here.  Replace uses with the copies we created.
	Replace and convert the def.  Adjust REG_DEAD notes, remove
	REG_EQUIV/EQUAL notes.
	(general_scalar_chain::convert_registers): Only handle copies
	into the chain here.

From-SVN: r274926