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reassoc: Do not bias loop-carried PHIs early

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Biasing loop-carried PHIs during the 1st reassociation pass interferes
with reduction chains and does not bring measurable benefits, so do it
only during the 2nd reassociation pass.

gcc/ChangeLog:

	* passes.def (pass_reassoc): Rename parameter to early_p.
	* tree-ssa-reassoc.c (reassoc_bias_loop_carried_phi_ranks_p):
	New variable.
	(phi_rank): Don't bias loop-carried phi ranks
	before vectorization pass.
	(execute_reassoc): Add bias_loop_carried_phi_ranks_p parameter.
	(pass_reassoc::pass_reassoc): Add bias_loop_carried_phi_ranks_p
	initializer.
	(pass_reassoc::set_param): Set bias_loop_carried_phi_ranks_p
	value.
	(pass_reassoc::execute): Pass bias_loop_carried_phi_ranks_p to
	execute_reassoc.
	(pass_reassoc::bias_loop_carried_phi_ranks_p): New member.
This commit is contained in:
Ilya Leoshkevich 2021-09-14 20:41:18 +02:00
parent 3b7041e834
commit 99c106e695
2 changed files with 16 additions and 4 deletions
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4
gcc/passes.def
View file

@ -243,7 +243,7 @@ along with GCC; see the file COPYING3. If not see
/* Identify paths that should never be executed in a conforming
program and isolate those paths. */
NEXT_PASS (pass_isolate_erroneous_paths);
NEXT_PASS (pass_reassoc, true /* insert_powi_p */);
NEXT_PASS (pass_reassoc, true /* early_p */);
NEXT_PASS (pass_dce);
NEXT_PASS (pass_forwprop);
NEXT_PASS (pass_phiopt, false /* early_p */);
@ -326,7 +326,7 @@ along with GCC; see the file COPYING3. If not see
NEXT_PASS (pass_lower_vector_ssa);
NEXT_PASS (pass_lower_switch);
NEXT_PASS (pass_cse_reciprocals);
NEXT_PASS (pass_reassoc, false /* insert_powi_p */);
NEXT_PASS (pass_reassoc, false /* early_p */);
NEXT_PASS (pass_strength_reduction);
NEXT_PASS (pass_split_paths);
NEXT_PASS (pass_tracer);

16
gcc/tree-ssa-reassoc.c
View file

@ -180,6 +180,10 @@ along with GCC; see the file COPYING3. If not see
point 3a in the pass header comment. */
static bool reassoc_insert_powi_p;
/* Enable biasing ranks of loop accumulators. We don't want this before
vectorization, since it interferes with reduction chains. */
static bool reassoc_bias_loop_carried_phi_ranks_p;
/* Statistics */
static struct
{
@ -269,6 +273,9 @@ phi_rank (gimple *stmt)
use_operand_p use;
gimple *use_stmt;
if (!reassoc_bias_loop_carried_phi_ranks_p)
return bb_rank[bb->index];
/* We only care about real loops (those with a latch). */
if (!father->latch)
return bb_rank[bb->index];
@ -6940,9 +6947,10 @@ fini_reassoc (void)
optimization of a gimple conditional. Otherwise returns zero. */
static unsigned int
execute_reassoc (bool insert_powi_p)
execute_reassoc (bool insert_powi_p, bool bias_loop_carried_phi_ranks_p)
{
reassoc_insert_powi_p = insert_powi_p;
reassoc_bias_loop_carried_phi_ranks_p = bias_loop_carried_phi_ranks_p;
init_reassoc ();
@ -6983,15 +6991,19 @@ public:
{
gcc_assert (n == 0);
insert_powi_p = param;
bias_loop_carried_phi_ranks_p = !param;
}
virtual bool gate (function *) { return flag_tree_reassoc != 0; }
virtual unsigned int execute (function *)
{ return execute_reassoc (insert_powi_p); }
{
return execute_reassoc (insert_powi_p, bias_loop_carried_phi_ranks_p);
}
private:
/* Enable insertion of __builtin_powi calls during execute_reassoc. See
point 3a in the pass header comment. */
bool insert_powi_p;
bool bias_loop_carried_phi_ranks_p;
}; // class pass_reassoc
} // anon namespace