/**
* @file
- * @brief Code Placement. Pins all floating nodes to a block where they
- * will be executed only if needed.
+ * @brief Move nodes to a block where they will be executed the least
+ * often.
* @author Christian Schaefer, Goetz Lindenmaier, Sebastian Felis,
* Michael Beck
- * @version $Id$
+ *
+ * The idea here is to push nodes as deep into the dominance tree as their
+ * dependencies allow. After pushing them back up out of as many loops as
+ * possible.
*/
#include "config.h"
+#include <stdbool.h>
+
#include "iroptimize.h"
#include "adt/pdeq.h"
#include "irnode_t.h"
#include "irgopt.h"
#include "irpass.h"
-/**
- * Returns non-zero, is a block is not reachable from Start.
- *
- * @param block the block to test
- */
-static int is_Block_unreachable(ir_node *block)
+static bool is_block_reachable(ir_node *block)
{
- return is_Block_dead(block) || get_Block_dom_depth(block) < 0;
+ return get_Block_dom_depth(block) >= 0;
}
/**
* Find the earliest correct block for node n. --- Place n into the
* same Block as its dominance-deepest Input.
*
- * We have to avoid calls to get_nodes_block() here
- * because the graph is floating.
- *
* move_out_of_loops() expects that place_floats_early() have placed
* all "living" nodes into a living block. That's why we must
* move nodes in dead block with "live" successors into a valid
* in case of a Phi into the effective use block). For Phi successors,
* this may still be a dead block, but then there is no real use, as
* the control flow will be dead later.
- *
- * @param n the node to be placed
- * @param worklist a worklist, predecessors of non-floating nodes are placed here
*/
static void place_floats_early(ir_node *n, waitq *worklist)
{
- int i, irn_arity;
+ int i;
+ int arity;
+ ir_node *block;
+ int new_depth;
+ ir_graph *irg;
+ ir_node *start_block;
+ ir_node *new_block;
/* we must not run into an infinite loop */
- assert(!irn_visited(n));
- mark_irn_visited(n);
-
- /* Place floating nodes. */
- if (get_irn_pinned(n) == op_pin_state_floats) {
- ir_node *curr_block = get_nodes_block(n);
- int in_dead_block = is_Block_unreachable(curr_block);
- int depth = 0;
- ir_node *b = NULL; /* The block to place this node in */
- ir_graph *irg = get_irn_irg(n);
-
- assert(!is_Block(n));
-
- if (is_irn_start_block_placed(n)) {
- /* These nodes will not be placed by the loop below. */
- b = get_irg_start_block(irg);
- depth = 1;
- }
-
- /* find the block for this node. */
- irn_arity = get_irn_arity(n);
- for (i = 0; i < irn_arity; i++) {
+ if (irn_visited_else_mark(n))
+ return;
+
+ /* The algorithm relies on the fact that all predecessors of a block are
+ * moved up after a call to place_float_early of the predecessors
+ * (see the loop below).
+ * However we have to break cycles somewhere. Relying on the visited flag
+ * will result in nodes not being moved up despite their place_floats_early
+ * call.
+ * Instead we break cycles at pinned nodes which won't move anyway:
+ * This works because in firm each cycle contains a Phi or Block node
+ * (which are pinned)
+ */
+ if (get_irn_pinned(n) != op_pin_state_floats) {
+ /* we can't move pinned nodes */
+ arity = get_irn_arity(n);
+ for (i = 0; i < arity; ++i) {
ir_node *pred = get_irn_n(n, i);
- ir_node *pred_block;
-
- if (!irn_visited(pred)
- && (get_irn_pinned(pred) == op_pin_state_floats)) {
-
- /*
- * If the current node is NOT in a dead block, but one of its
- * predecessors is, we must move the predecessor to a live
- * block.
- * Such thing can happen, if global CSE chose a node from a
- * dead block. We move it simply to our block.
- * Note that neither Phi nor End nodes are floating, so we don't
- * need to handle them here.
- */
- if (! in_dead_block) {
- if (get_irn_pinned(pred) == op_pin_state_floats &&
- is_Block_unreachable(get_nodes_block(pred)))
- set_nodes_block(pred, curr_block);
- }
- place_floats_early(pred, worklist);
- }
-
- /*
- * A node in the Bad block must stay in the bad block,
- * so don't compute a new block for it.
- */
- if (in_dead_block)
- continue;
-
- /* Because all loops contain at least one op_pin_state_pinned node,
- now all our inputs are either op_pin_state_pinned or
- place_early() has already been finished on them.
- We do not have any unfinished inputs! */
- pred_block = get_nodes_block(pred);
- if ((!is_Block_dead(pred_block)) &&
- (get_Block_dom_depth(pred_block) > depth)) {
- b = pred_block;
- depth = get_Block_dom_depth(pred_block);
- }
- /* Avoid that the node is placed in the Start block if we are not
- in the backend phase. */
- if (depth == 1 &&
- get_Block_dom_depth(get_nodes_block(n)) > 1 &&
- get_irg_phase_state(irg) != phase_backend) {
- b = get_Block_cfg_out(get_irg_start_block(irg), 0);
- assert(b != get_irg_start_block(irg));
- depth = 2;
- }
+ pdeq_putr(worklist, pred);
}
- if (b)
- set_nodes_block(n, b);
+ if (!is_Block(n))
+ pdeq_putr(worklist, get_nodes_block(n));
+ return;
}
- /*
- * Add predecessors of non floating nodes and non-floating predecessors
- * of floating nodes to worklist and fix their blocks if the are in dead
- * block.
- */
- irn_arity = get_irn_arity(n);
-
- if (is_End(n)) {
- /*
- * Simplest case: End node. Predecessors are keep-alives,
- * no need to move out of dead block.
- */
- for (i = -1; i < irn_arity; ++i) {
- ir_node *pred = get_irn_n(n, i);
- if (!irn_visited(pred))
- waitq_put(worklist, pred);
- }
- } else if (is_Block(n)) {
- /*
- * Blocks: Predecessors are control flow, no need to move
- * them out of dead block.
- */
- for (i = irn_arity - 1; i >= 0; --i) {
- ir_node *pred = get_irn_n(n, i);
- if (!irn_visited(pred))
- waitq_put(worklist, pred);
- }
- } else if (is_Phi(n)) {
- ir_node *pred;
- ir_node *curr_block = get_nodes_block(n);
- int in_dead_block = is_Block_unreachable(curr_block);
-
- /*
- * Phi nodes: move nodes from dead blocks into the effective use
- * of the Phi-input if the Phi is not in a bad block.
- */
- pred = get_nodes_block(n);
- if (!irn_visited(pred))
- waitq_put(worklist, pred);
-
- for (i = irn_arity - 1; i >= 0; --i) {
- ir_node *pred = get_irn_n(n, i);
+ block = get_nodes_block(n);
- if (!irn_visited(pred)) {
- if (! in_dead_block &&
- get_irn_pinned(pred) == op_pin_state_floats &&
- is_Block_unreachable(get_nodes_block(pred))) {
- set_nodes_block(pred, get_Block_cfgpred_block(curr_block, i));
- }
- waitq_put(worklist, pred);
- }
- }
- } else {
- ir_node *pred;
- ir_node *curr_block = get_nodes_block(n);
- int in_dead_block = is_Block_unreachable(curr_block);
-
- /*
- * All other nodes: move nodes from dead blocks into the same block.
- */
- pred = get_nodes_block(n);
- if (!irn_visited(pred))
- waitq_put(worklist, pred);
-
- for (i = irn_arity - 1; i >= 0; --i) {
- ir_node *pred = get_irn_n(n, i);
+ /* first move predecessors up */
+ arity = get_irn_arity(n);
+ place_floats_early(block, worklist);
+ for (i = 0; i < arity; ++i) {
+ ir_node *pred = get_irn_n(n, i);
+ place_floats_early(pred, worklist);
+ }
- if (!irn_visited(pred)) {
- if (! in_dead_block &&
- get_irn_pinned(pred) == op_pin_state_floats &&
- is_Block_unreachable(get_nodes_block(pred))) {
- set_nodes_block(pred, curr_block);
- }
- waitq_put(worklist, pred);
- }
+ /* determine earliest point */
+ new_block = NULL;
+ new_depth = 0;
+ for (i = 0; i < arity; ++i) {
+ ir_node *pred = get_irn_n(n, i);
+ ir_node *pred_block = get_nodes_block(pred);
+ int pred_depth = get_Block_dom_depth(pred_block);
+ if (pred_depth > new_depth) {
+ new_depth = pred_depth;
+ new_block = pred_block;
}
}
+
+ /* avoid moving nodes into the start block if we are not in the backend */
+ irg = get_irn_irg(n);
+ start_block = get_irg_start_block(irg);
+ if (new_block == start_block && block != start_block &&
+ get_irg_phase_state(irg) != phase_backend) {
+ assert(get_Block_n_cfg_outs(start_block) == 1);
+ new_block = get_Block_cfg_out(start_block, 0);
+ }
+
+ /* Set the new block */
+ if (new_block != NULL)
+ set_nodes_block(n, new_block);
}
/**
{
assert(block != NULL);
- /* we do not want to place nodes in dead blocks */
- if (is_Block_dead(block))
- return dca;
-
/* We found a first legal placement. */
- if (!dca) return block;
+ if (!dca)
+ return block;
/* Find a placement that is dominates both, dca and block. */
while (get_Block_dom_depth(block) > get_Block_dom_depth(dca))
* I.e., DCA is the block where we might place PRODUCER.
* A data flow edge points from producer to consumer.
*/
-static ir_node *consumer_dom_dca(ir_node *dca, ir_node *consumer, ir_node *producer)
+static ir_node *consumer_dom_dca(ir_node *dca, ir_node *consumer,
+ ir_node *producer)
{
/* Compute the last block into which we can place a node so that it is
before consumer. */
for (i = 0; i < arity; i++) {
if (get_Phi_pred(consumer, i) == producer) {
ir_node *new_block = get_Block_cfgpred_block(phi_block, i);
+ if (is_Bad(new_block))
+ continue;
- if (!is_Block_unreachable(new_block))
- dca = calc_dom_dca(dca, new_block);
+ assert(is_block_reachable(new_block));
+ dca = calc_dom_dca(dca, new_block);
}
}
} else {
*/
static void move_out_of_loops(ir_node *n, ir_node *early)
{
- ir_node *best, *dca;
- assert(n && early);
-
+ ir_node *block = get_nodes_block(n);
+ ir_node *best = block;
+ int best_depth = get_block_loop_depth(best);
/* Find the region deepest in the dominator tree dominating
dca with the least loop nesting depth, but still dominated
by our early placement. */
- dca = get_nodes_block(n);
-
- best = dca;
- while (dca != early) {
- dca = get_Block_idom(dca);
- if (!dca || is_Bad(dca)) break; /* may be Bad if not reachable from Start */
- if (get_block_loop_depth(dca) < get_block_loop_depth(best)) {
- best = dca;
+ while (block != early) {
+ ir_node *idom = get_Block_idom(block);
+ int idom_depth = get_block_loop_depth(idom);
+ if (idom_depth < best_depth) {
+ best = idom;
+ best_depth = idom_depth;
}
+ block = idom;
}
if (best != get_nodes_block(n))
set_nodes_block(n, best);
for (i = get_irn_n_outs(node) - 1; i >= 0; --i) {
ir_node *succ = get_irn_out(node, i);
- if (is_End(succ)) {
- /*
- * This consumer is the End node, a keep alive edge.
- * This is not a real consumer, so we ignore it
- */
+ /* keepalive edges are special and don't respect the dominance */
+ if (is_End(succ))
continue;
- }
if (is_Proj(succ)) {
/* Proj nodes are in the same block as node, so
* the users of Proj are our users. */
dca = get_deepest_common_dom_ancestor(succ, dca);
} else {
- /* ignore if succ is in dead code */
- ir_node *succ_blk = get_nodes_block(succ);
- if (is_Block_unreachable(succ_blk))
- continue;
+ assert(is_block_reachable(get_nodes_block(succ)));
dca = consumer_dom_dca(dca, succ, node);
}
}
* with the least loop-nesting-depth. This places N out of as many
* loops as possible and then makes it as control dependent as
* possible.
- *
- * @param n the node to be placed
- * @param worklist a worklist, all successors of non-floating nodes are
- * placed here
*/
static void place_floats_late(ir_node *n, pdeq *worklist)
{
- int i, n_outs;
- ir_node *early_blk;
-
- assert(!irn_visited(n)); /* no multiple placement */
-
- mark_irn_visited(n);
-
- /* no need to place block nodes, control nodes are already placed. */
- if (!is_Block(n) &&
- (!is_cfop(n)) &&
- (get_irn_mode(n) != mode_X)) {
- /* Remember the early_blk placement of this block to move it
- out of loop no further than the early_blk placement. */
- early_blk = get_nodes_block(n);
-
- /*
- * BEWARE: Here we also get code, that is live, but
- * was in a dead block. If the node is life, but because
- * of CSE in a dead block, we still might need it.
- */
-
- /* Assure that our users are all placed, except the Phi-nodes.
- --- Each data flow cycle contains at least one Phi-node. We
- have to break the `user has to be placed before the
- producer' dependence cycle and the Phi-nodes are the
- place to do so, because we need to base our placement on the
- final region of our users, which is OK with Phi-nodes, as they
- are op_pin_state_pinned, and they never have to be placed after a
- producer of one of their inputs in the same block anyway. */
- for (i = get_irn_n_outs(n) - 1; i >= 0; --i) {
- ir_node *succ = get_irn_out(n, i);
- if (!irn_visited(succ) && !is_Phi(succ))
- place_floats_late(succ, worklist);
- }
+ int n_outs;
+ int i;
+ ir_node *block;
+ ir_node *dca;
- if (! is_Block_dead(early_blk)) {
- /* do only move things that where not dead */
- ir_op *op = get_irn_op(n);
-
- /* We have to determine the final block of this node... except for
- constants and Projs */
- if ((get_irn_pinned(n) == op_pin_state_floats) &&
- (op != op_Const) &&
- (op != op_SymConst) &&
- (op != op_Proj))
- {
- /* deepest common ancestor in the dominator tree of all nodes'
- blocks depending on us; our final placement has to dominate
- DCA. */
- ir_node *dca = get_deepest_common_dom_ancestor(n, NULL);
- if (dca != NULL) {
- set_nodes_block(n, dca);
- move_out_of_loops(n, early_blk);
- if (get_irn_mode(n) == mode_T) {
- set_projs_block(n, get_nodes_block(n));
- }
- }
- }
+ if (irn_visited_else_mark(n))
+ return;
+
+ n_outs = get_irn_n_outs(n);
+ /* break cycles at pinned nodes (see place place_floats_early) as to why */
+ if (get_irn_pinned(n) != op_pin_state_floats) {
+ for (i = 0; i < n_outs; ++i) {
+ ir_node *succ = get_irn_out(n, i);
+ pdeq_putr(worklist, succ);
}
+ return;
}
- /* Add successors of all non-floating nodes on list. (Those of floating
- nodes are placed already and therefore are marked.) */
- n_outs = get_irn_n_outs(n);
- for (i = 0; i < n_outs; i++) {
+ /* place our users */
+ for (i = 0; i < n_outs; ++i) {
ir_node *succ = get_irn_out(n, i);
- if (!irn_visited(succ)) {
- pdeq_putr(worklist, succ);
+ place_floats_late(succ, worklist);
+ }
+
+ /* no point in moving Projs around, they are moved with their predecessor */
+ if (is_Proj(n))
+ return;
+ /* some nodes should simply stay in the startblock */
+ if (is_irn_start_block_placed(n)) {
+ assert(get_nodes_block(n) == get_irg_start_block(get_irn_irg(n)));
+ return;
+ }
+
+ block = get_nodes_block(n);
+ assert(is_block_reachable(block));
+
+ /* deepest common ancestor in the dominator tree of all nodes'
+ blocks depending on us; our final placement has to dominate
+ DCA. */
+ dca = get_deepest_common_dom_ancestor(n, NULL);
+ if (dca != NULL) {
+ set_nodes_block(n, dca);
+ move_out_of_loops(n, block);
+ if (get_irn_mode(n) == mode_T) {
+ set_projs_block(n, get_nodes_block(n));
}
}
}
}
}
+/* Code Placement. */
void place_code(ir_graph *irg)
{
waitq *worklist;
- /* perform gcse which currently only works immediately before performing
- * code placement (we should fix this) */
- set_opt_global_cse(1);
- optimize_graph_df(irg);
- set_opt_global_cse(0);
-
- remove_critical_cf_edges(irg);
-
/* Handle graph state */
assert(get_irg_phase_state(irg) != phase_building);
- assure_irg_outs(irg);
- assure_doms(irg);
- assure_cf_loop(irg);
+ assure_irg_properties(irg,
+ IR_GRAPH_PROPERTY_NO_CRITICAL_EDGES |
+ IR_GRAPH_PROPERTY_NO_UNREACHABLE_CODE |
+ IR_GRAPH_PROPERTY_CONSISTENT_OUTS |
+ IR_GRAPH_PROPERTY_CONSISTENT_DOMINANCE |
+ IR_GRAPH_PROPERTY_CONSISTENT_LOOPINFO);
/* Place all floating nodes as early as possible. This guarantees
a legal code placement. */
worklist = new_waitq();
place_early(irg, worklist);
+ /* While GCSE might place nodes in unreachable blocks,
+ * these are now placed in reachable blocks. */
+
/* Note: place_early changes only blocks, no data edges. So, the
* data out edges are still valid, no need to recalculate them here. */
unnecessary executions of the node. */
place_late(irg, worklist);
- set_irg_outs_inconsistent(irg);
- set_irg_loopinfo_inconsistent(irg);
del_waitq(worklist);
+ confirm_irg_properties(irg, IR_GRAPH_PROPERTIES_NONE);
}
/**
*/
static void place_code_wrapper(ir_graph *irg)
{
+ set_opt_global_cse(1);
+ optimize_graph_df(irg);
place_code(irg);
+ set_opt_global_cse(0);
}
ir_graph_pass_t *place_code_pass(const char *name)
projects / libfirm / blobdiff