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

gcc/ChangeLog

+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.
+
 2018-01-12  Richard Biener  <rguenther@suse.de>
 
 	PR debug/83157

gcc/config/i386/i386.c

@@ -4900,6 +4900,11 @@ ix86_option_override_internal (bool main_args_p,
 	(cf_protection_level) (opts->x_flag_cf_protection | CF_SET);
     }
 
+  if (ix86_tune_features [X86_TUNE_AVOID_128FMA_CHAINS])
+    maybe_set_param_value (PARAM_AVOID_FMA_MAX_BITS, 128,
+			   opts->x_param_values,
+			   opts_set->x_param_values);
+
   return true;
 }
 

gcc/config/i386/x86-tune.def

@@ -403,6 +403,10 @@ DEF_TUNE (X86_TUNE_AVOID_4BYTE_PREFIXES, "avoid_4byte_prefixes",
 DEF_TUNE (X86_TUNE_USE_GATHER, "use_gather",
           ~(m_ZNVER1 | m_GENERIC))
 
+/* X86_TUNE_AVOID_128FMA_CHAINS: Avoid creating loops with tight 128bit or
+   smaller FMA chain.  */
+DEF_TUNE (X86_TUNE_AVOID_128FMA_CHAINS, "avoid_fma_chains", m_ZNVER1)
+
 /*****************************************************************************/
 /* AVX instruction selection tuning (some of SSE flags affects AVX, too)     */
 /*****************************************************************************/

gcc/params.def

@@ -1326,6 +1326,11 @@ DEFPARAM(PARAM_UNROLL_JAM_MAX_UNROLL,
 	 "Maximum unroll factor for the unroll-and-jam transformation.",
 	 4, 0, 0)
 
+DEFPARAM(PARAM_AVOID_FMA_MAX_BITS,
+	 "avoid-fma-max-bits",
+	 "Maximum number of bits for which we avoid creating FMAs.",
+	 0, 0, 512)
+
 /*
 
 Local variables: