#include "pointer-set.h"
#include "cfgloop.h"
#include "flags.h"
+#include "target.h"
+#include "params.h"
/* This is a simple global reassociation pass. It is, in part, based
on the LLVM pass of the same name (They do some things more/less
}
}
+/* This function checks three consequtive operands in
+ passed operands vector OPS starting from OPINDEX and
+ swaps two operands if it is profitable for binary operation
+ consuming OPINDEX + 1 abnd OPINDEX + 2 operands.
+
+ We pair ops with the same rank if possible.
+
+ The alternative we try is to see if STMT is a destructive
+ update style statement, which is like:
+ b = phi (a, ...)
+ a = c + b;
+ In that case, we want to use the destructive update form to
+ expose the possible vectorizer sum reduction opportunity.
+ In that case, the third operand will be the phi node. This
+ check is not performed if STMT is null.
+
+ We could, of course, try to be better as noted above, and do a
+ lot of work to try to find these opportunities in >3 operand
+ cases, but it is unlikely to be worth it. */
+
+static void
+swap_ops_for_binary_stmt (VEC(operand_entry_t, heap) * ops,
+ unsigned int opindex, gimple stmt)
+{
+ operand_entry_t oe1, oe2, oe3;
+
+ oe1 = VEC_index (operand_entry_t, ops, opindex);
+ oe2 = VEC_index (operand_entry_t, ops, opindex + 1);
+ oe3 = VEC_index (operand_entry_t, ops, opindex + 2);
+
+ if ((oe1->rank == oe2->rank
+ && oe2->rank != oe3->rank)
+ || (stmt && is_phi_for_stmt (stmt, oe3->op)
+ && !is_phi_for_stmt (stmt, oe1->op)
+ && !is_phi_for_stmt (stmt, oe2->op)))
+ {
+ struct operand_entry temp = *oe3;
+ oe3->op = oe1->op;
+ oe3->rank = oe1->rank;
+ oe1->op = temp.op;
+ oe1->rank= temp.rank;
+ }
+ else if ((oe1->rank == oe3->rank
+ && oe2->rank != oe3->rank)
+ || (stmt && is_phi_for_stmt (stmt, oe2->op)
+ && !is_phi_for_stmt (stmt, oe1->op)
+ && !is_phi_for_stmt (stmt, oe3->op)))
+ {
+ struct operand_entry temp = *oe2;
+ oe2->op = oe1->op;
+ oe2->rank = oe1->rank;
+ oe1->op = temp.op;
+ oe1->rank= temp.rank;
+ }
+}
+
/* Recursively rewrite our linearized statements so that the operators
match those in OPS[OPINDEX], putting the computation in rank
order. */
tree rhs2 = gimple_assign_rhs2 (stmt);
operand_entry_t oe;
- /* If we have three operands left, then we want to make sure the one
- that gets the double binary op are the ones with the same rank.
-
- The alternative we try is to see if this is a destructive
- update style statement, which is like:
- b = phi (a, ...)
- a = c + b;
- In that case, we want to use the destructive update form to
- expose the possible vectorizer sum reduction opportunity.
- In that case, the third operand will be the phi node.
-
- We could, of course, try to be better as noted above, and do a
- lot of work to try to find these opportunities in >3 operand
- cases, but it is unlikely to be worth it. */
+ /* If we have three operands left, then we want to make sure the ones
+ that get the double binary op are chosen wisely. */
if (opindex + 3 == VEC_length (operand_entry_t, ops))
- {
- operand_entry_t oe1, oe2, oe3;
-
- oe1 = VEC_index (operand_entry_t, ops, opindex);
- oe2 = VEC_index (operand_entry_t, ops, opindex + 1);
- oe3 = VEC_index (operand_entry_t, ops, opindex + 2);
-
- if ((oe1->rank == oe2->rank
- && oe2->rank != oe3->rank)
- || (is_phi_for_stmt (stmt, oe3->op)
- && !is_phi_for_stmt (stmt, oe1->op)
- && !is_phi_for_stmt (stmt, oe2->op)))
- {
- struct operand_entry temp = *oe3;
- oe3->op = oe1->op;
- oe3->rank = oe1->rank;
- oe1->op = temp.op;
- oe1->rank= temp.rank;
- }
- else if ((oe1->rank == oe3->rank
- && oe2->rank != oe3->rank)
- || (is_phi_for_stmt (stmt, oe2->op)
- && !is_phi_for_stmt (stmt, oe1->op)
- && !is_phi_for_stmt (stmt, oe3->op)))
- {
- struct operand_entry temp = *oe2;
- oe2->op = oe1->op;
- oe2->rank = oe1->rank;
- oe1->op = temp.op;
- oe1->rank= temp.rank;
- }
- }
+ swap_ops_for_binary_stmt (ops, opindex, stmt);
/* The final recursion case for this function is that you have
exactly two operations left.
rewrite_expr_tree (SSA_NAME_DEF_STMT (rhs1), opindex + 1, ops, moved);
}
+/* Find out how many cycles we need to compute statements chain.
+ OPS_NUM holds number os statements in a chain. CPU_WIDTH is a
+ maximum number of independent statements we may execute per cycle. */
+
+static int
+get_required_cycles (int ops_num, int cpu_width)
+{
+ int res;
+ int elog;
+ unsigned int rest;
+
+ /* While we have more than 2 * cpu_width operands
+ we may reduce number of operands by cpu_width
+ per cycle. */
+ res = ops_num / (2 * cpu_width);
+
+ /* Remained operands count may be reduced twice per cycle
+ until we have only one operand. */
+ rest = (unsigned)(ops_num - res * cpu_width);
+ elog = exact_log2 (rest);
+ if (elog >= 0)
+ res += elog;
+ else
+ res += floor_log2 (rest) + 1;
+
+ return res;
+}
+
+/* Returns an optimal number of registers to use for computation of
+ given statements. */
+
+static int
+get_reassociation_width (int ops_num, enum tree_code opc,
+ enum machine_mode mode)
+{
+ int param_width = PARAM_VALUE (PARAM_TREE_REASSOC_WIDTH);
+ int width;
+ int width_min;
+ int cycles_best;
+
+ if (param_width > 0)
+ width = param_width;
+ else
+ width = targetm.sched.reassociation_width (opc, mode);
+
+ if (width == 1)
+ return width;
+
+ /* Get the minimal time required for sequence computation. */
+ cycles_best = get_required_cycles (ops_num, width);
+
+ /* Check if we may use less width and still compute sequence for
+ the same time. It will allow us to reduce registers usage.
+ get_required_cycles is monotonically increasing with lower width
+ so we can perform a binary search for the minimal width that still
+ results in the optimal cycle count. */
+ width_min = 1;
+ while (width > width_min)
+ {
+ int width_mid = (width + width_min) / 2;
+
+ if (get_required_cycles (ops_num, width_mid) == cycles_best)
+ width = width_mid;
+ else if (width_min < width_mid)
+ width_min = width_mid;
+ else
+ break;
+ }
+
+ return width;
+}
+
+/* Recursively rewrite our linearized statements so that the operators
+ match those in OPS[OPINDEX], putting the computation in rank
+ order and trying to allow operations to be executed in
+ parallel. */
+
+static void
+rewrite_expr_tree_parallel (gimple stmt, int width,
+ VEC(operand_entry_t, heap) * ops)
+{
+ enum tree_code opcode = gimple_assign_rhs_code (stmt);
+ int op_num = VEC_length (operand_entry_t, ops);
+ int stmt_num = op_num - 1;
+ gimple *stmts = XALLOCAVEC (gimple, stmt_num);
+ int op_index = op_num - 1;
+ int stmt_index = 0;
+ int ready_stmts_end = 0;
+ int i = 0;
+ tree last_rhs1 = gimple_assign_rhs1 (stmt);
+ tree lhs_var;
+
+ /* We start expression rewriting from the top statements.
+ So, in this loop we create a full list of statements
+ we will work with. */
+ stmts[stmt_num - 1] = stmt;
+ for (i = stmt_num - 2; i >= 0; i--)
+ stmts[i] = SSA_NAME_DEF_STMT (gimple_assign_rhs1 (stmts[i+1]));
+
+ lhs_var = create_tmp_reg (TREE_TYPE (last_rhs1), NULL);
+ add_referenced_var (lhs_var);
+
+ for (i = 0; i < stmt_num; i++)
+ {
+ tree op1, op2;
+
+ /* Determine whether we should use results of
+ already handled statements or not. */
+ if (ready_stmts_end == 0
+ && (i - stmt_index >= width || op_index < 1))
+ ready_stmts_end = i;
+
+ /* Now we choose operands for the next statement. Non zero
+ value in ready_stmts_end means here that we should use
+ the result of already generated statements as new operand. */
+ if (ready_stmts_end > 0)
+ {
+ op1 = gimple_assign_lhs (stmts[stmt_index++]);
+ if (ready_stmts_end > stmt_index)
+ op2 = gimple_assign_lhs (stmts[stmt_index++]);
+ else if (op_index >= 0)
+ op2 = VEC_index (operand_entry_t, ops, op_index--)->op;
+ else
+ {
+ gcc_assert (stmt_index < i);
+ op2 = gimple_assign_lhs (stmts[stmt_index++]);
+ }
+
+ if (stmt_index >= ready_stmts_end)
+ ready_stmts_end = 0;
+ }
+ else
+ {
+ if (op_index > 1)
+ swap_ops_for_binary_stmt (ops, op_index - 2, NULL);
+ op2 = VEC_index (operand_entry_t, ops, op_index--)->op;
+ op1 = VEC_index (operand_entry_t, ops, op_index--)->op;
+ }
+
+ /* If we emit the last statement then we should put
+ operands into the last statement. It will also
+ break the loop. */
+ if (op_index < 0 && stmt_index == i)
+ i = stmt_num - 1;
+
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ {
+ fprintf (dump_file, "Transforming ");
+ print_gimple_stmt (dump_file, stmts[i], 0, 0);
+ }
+
+ /* We keep original statement only for the last one. All
+ others are recreated. */
+ if (i == stmt_num - 1)
+ {
+ gimple_assign_set_rhs1 (stmts[i], op1);
+ gimple_assign_set_rhs2 (stmts[i], op2);
+ update_stmt (stmts[i]);
+ }
+ else
+ stmts[i] = build_and_add_sum (lhs_var, op1, op2, opcode);
+
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ {
+ fprintf (dump_file, " into ");
+ print_gimple_stmt (dump_file, stmts[i], 0, 0);
+ }
+ }
+
+ remove_visited_stmt_chain (last_rhs1);
+}
+
/* Transform STMT, which is really (A +B) + (C + D) into the left
linear form, ((A+B)+C)+D.
Recurse on D if necessary. */
}
}
else
- rewrite_expr_tree (stmt, 0, ops, false);
+ {
+ enum machine_mode mode = TYPE_MODE (TREE_TYPE (lhs));
+ int ops_num = VEC_length (operand_entry_t, ops);
+ int width = get_reassociation_width (ops_num, rhs_code, mode);
+
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ fprintf (dump_file,
+ "Width = %d was chosen for reassociation\n", width);
+
+ if (width > 1
+ && VEC_length (operand_entry_t, ops) > 3)
+ rewrite_expr_tree_parallel (stmt, width, ops);
+ else
+ rewrite_expr_tree (stmt, 0, ops, false);
+ }
VEC_free (operand_entry_t, heap, ops);
}
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