Deferring FMA transformations in tight loops

Deferring FMA transformations in tight loops

2018-01-12  Martin Jambor  <mjambor@suse.cz>

	PR target/81616
	* params.def: New parameter PARAM_AVOID_FMA_MAX_BITS.
	* tree-ssa-math-opts.c: Include domwalk.h.
	(convert_mult_to_fma_1): New function.
	(fma_transformation_info): New type.
	(fma_deferring_state): Likewise.
	(cancel_fma_deferring): New function.
	(result_of_phi): Likewise.
	(last_fma_candidate_feeds_initial_phi): Likewise.
	(convert_mult_to_fma): Added deferring logic, split actual
	transformation to convert_mult_to_fma_1.
	(math_opts_dom_walker): New type.
	(math_opts_dom_walker::after_dom_children): New method, body moved
	here from pass_optimize_widening_mul::execute, added deferring logic
	bits.
	(pass_optimize_widening_mul::execute): Moved most of code to
	math_opts_dom_walker::after_dom_children.
	* config/i386/x86-tune.def (X86_TUNE_AVOID_128FMA_CHAINS): New.
	* config/i386/i386.c (ix86_option_override_internal): Added
	maybe_setting of PARAM_AVOID_FMA_MAX_BITS.

From-SVN: r256581