https://gcc.gnu.org/g:f647d4f58a968079c342a0a3f7e71444d3836614
commit r16-3284-gf647d4f58a968079c342a0a3f7e71444d3836614
Author: Richard Biener <rguent...@suse.de>
Date: Tue Aug 19 13:38:58 2025 +0200
Remove reduction chain detection from parloops
Historically SLP reduction chains were the only multi-stmt reductions
supported. But since we have check_reduction_path more complicated
cases are handled. As parloops doesn't do any specific chain
processing it can solely rely on that functionality instead.
* tree-parloops.cc (parloops_is_slp_reduction): Remove.
(parloops_is_simple_reduction): Do not call it.
Diff:
---
gcc/tree-parloops.cc | 177 ---------------------------------------------------
1 file changed, 177 deletions(-)
diff --git a/gcc/tree-parloops.cc b/gcc/tree-parloops.cc
index 6e2f7dfb6cfb..388f903a942a 100644
--- a/gcc/tree-parloops.cc
+++ b/gcc/tree-parloops.cc
@@ -205,170 +205,6 @@ parloops_valid_reduction_input_p (stmt_vec_info
def_stmt_info)
&& !is_loop_header_bb_p (gimple_bb (def_stmt_info->stmt))));
}
-/* Detect SLP reduction of the form:
-
- #a1 = phi <a5, a0>
- a2 = operation (a1)
- a3 = operation (a2)
- a4 = operation (a3)
- a5 = operation (a4)
-
- #a = phi <a5>
-
- PHI is the reduction phi node (#a1 = phi <a5, a0> above)
- FIRST_STMT is the first reduction stmt in the chain
- (a2 = operation (a1)).
-
- Return TRUE if a reduction chain was detected. */
-
-static bool
-parloops_is_slp_reduction (loop_vec_info loop_info, gimple *phi,
- gimple *first_stmt)
-{
- class loop *loop = (gimple_bb (phi))->loop_father;
- class loop *vect_loop = LOOP_VINFO_LOOP (loop_info);
- enum tree_code code;
- gimple *loop_use_stmt = NULL;
- stmt_vec_info use_stmt_info;
- tree lhs;
- imm_use_iterator imm_iter;
- use_operand_p use_p;
- int nloop_uses, size = 0, n_out_of_loop_uses;
- bool found = false;
-
- if (loop != vect_loop)
- return false;
-
- auto_vec<stmt_vec_info, 8> reduc_chain;
- lhs = PHI_RESULT (phi);
- code = gimple_assign_rhs_code (first_stmt);
- while (1)
- {
- nloop_uses = 0;
- n_out_of_loop_uses = 0;
- FOR_EACH_IMM_USE_FAST (use_p, imm_iter, lhs)
- {
- gimple *use_stmt = USE_STMT (use_p);
- if (is_gimple_debug (use_stmt))
- continue;
-
- /* Check if we got back to the reduction phi. */
- if (use_stmt == phi)
- {
- loop_use_stmt = use_stmt;
- found = true;
- break;
- }
-
- if (flow_bb_inside_loop_p (loop, gimple_bb (use_stmt)))
- {
- loop_use_stmt = use_stmt;
- nloop_uses++;
- }
- else
- n_out_of_loop_uses++;
-
- /* There are can be either a single use in the loop or two uses in
- phi nodes. */
- if (nloop_uses > 1 || (n_out_of_loop_uses && nloop_uses))
- return false;
- }
-
- if (found)
- break;
-
- /* We reached a statement with no loop uses. */
- if (nloop_uses == 0)
- return false;
-
- /* This is a loop exit phi, and we haven't reached the reduction phi. */
- if (gimple_code (loop_use_stmt) == GIMPLE_PHI)
- return false;
-
- if (!is_gimple_assign (loop_use_stmt)
- || code != gimple_assign_rhs_code (loop_use_stmt)
- || !flow_bb_inside_loop_p (loop, gimple_bb (loop_use_stmt)))
- return false;
-
- /* Insert USE_STMT into reduction chain. */
- use_stmt_info = loop_info->lookup_stmt (loop_use_stmt);
- reduc_chain.safe_push (use_stmt_info);
-
- lhs = gimple_assign_lhs (loop_use_stmt);
- size++;
- }
-
- if (!found || loop_use_stmt != phi || size < 2)
- return false;
-
- /* Swap the operands, if needed, to make the reduction operand be the second
- operand. */
- lhs = PHI_RESULT (phi);
- for (unsigned i = 0; i < reduc_chain.length (); ++i)
- {
- gassign *next_stmt = as_a <gassign *> (reduc_chain[i]->stmt);
- if (gimple_assign_rhs2 (next_stmt) == lhs)
- {
- tree op = gimple_assign_rhs1 (next_stmt);
- stmt_vec_info def_stmt_info = loop_info->lookup_def (op);
-
- /* Check that the other def is either defined in the loop
- ("vect_internal_def"), or it's an induction (defined by a
- loop-header phi-node). */
- if (def_stmt_info
- && flow_bb_inside_loop_p (loop, gimple_bb (def_stmt_info->stmt))
- && parloops_valid_reduction_input_p (def_stmt_info))
- {
- lhs = gimple_assign_lhs (next_stmt);
- continue;
- }
-
- return false;
- }
- else
- {
- tree op = gimple_assign_rhs2 (next_stmt);
- stmt_vec_info def_stmt_info = loop_info->lookup_def (op);
-
- /* Check that the other def is either defined in the loop
- ("vect_internal_def"), or it's an induction (defined by a
- loop-header phi-node). */
- if (def_stmt_info
- && flow_bb_inside_loop_p (loop, gimple_bb (def_stmt_info->stmt))
- && parloops_valid_reduction_input_p (def_stmt_info))
- {
- if (dump_enabled_p ())
- dump_printf_loc (MSG_NOTE, vect_location,
- "swapping oprnds: %G", (gimple *) next_stmt);
-
- swap_ssa_operands (next_stmt,
- gimple_assign_rhs1_ptr (next_stmt),
- gimple_assign_rhs2_ptr (next_stmt));
- update_stmt (next_stmt);
- }
- else
- return false;
- }
-
- lhs = gimple_assign_lhs (next_stmt);
- }
-
- /* Build up the actual chain. */
- for (unsigned i = 0; i < reduc_chain.length () - 1; ++i)
- {
- REDUC_GROUP_FIRST_ELEMENT (reduc_chain[i]) = reduc_chain[0];
- REDUC_GROUP_NEXT_ELEMENT (reduc_chain[i]) = reduc_chain[i+1];
- }
- REDUC_GROUP_FIRST_ELEMENT (reduc_chain.last ()) = reduc_chain[0];
- REDUC_GROUP_NEXT_ELEMENT (reduc_chain.last ()) = NULL;
-
- /* Save the chain for further analysis in SLP detection. */
- LOOP_VINFO_REDUCTION_CHAINS (loop_info).safe_push (reduc_chain[0]);
- REDUC_GROUP_SIZE (reduc_chain[0]) = size;
-
- return true;
-}
-
/* Return true if we need an in-order reduction for operation CODE
on type TYPE. NEED_WRAPPING_INTEGRAL_OVERFLOW is true if integer
overflow must wrap. */
@@ -836,19 +672,6 @@ parloops_is_simple_reduction (loop_vec_info loop_info,
stmt_vec_info phi_info,
return def_stmt_info;
}
- /* Try to find SLP reduction chain. */
- if (! nested_in_vect_loop
- && code != COND_EXPR
- && orig_code != MINUS_EXPR
- && parloops_is_slp_reduction (loop_info, phi, def_stmt))
- {
- if (dump_enabled_p ())
- report_ploop_op (MSG_NOTE, def_stmt,
- "reduction: detected reduction chain: ");
-
- return def_stmt_info;
- }
-
/* Look for the expression computing loop_arg from loop PHI result. */
if (check_reduction_path (vect_location, loop, phi, loop_arg, code))
return def_stmt_info;
