*/
#ifdef HAVE_CONFIG_H
-# include <config.h>
+# include "config.h"
#endif
#include <assert.h>
+#include "xmalloc.h"
#include "irnode_t.h"
#include "irgraph_t.h"
#include "irprog_t.h"
#include "ircons.h"
#include "iropt_t.h"
#include "irgwalk.h"
+#include "irgmod.h"
+#include "irdump.h"
#include "irvrfy.h"
#include "array.h"
/*------------------------------------------------------------------*/
/* Control flow optimization. */
+/* */
/* Removes Bad control flow predecessors and empty blocks. A block */
/* is empty if it contains only a Jmp node. */
/* Blocks can only be removed if they are not needed for the */
/* semantics of Phi nodes. */
/*------------------------------------------------------------------*/
+
+static void remove_senseless_conds(ir_node *bl, void *data)
+{
+ int i, j;
+ int n = get_irn_arity(bl);
+
+ assert(is_Block(bl));
+
+ for(i = 0; i < n; ++i) {
+ ir_node *pred_i = get_irn_n(bl, i);
+ ir_node *cond_i = skip_Proj(pred_i);
+
+ for(j = i + 1; j < n; ++j) {
+ ir_node *pred_j = get_irn_n(bl, j);
+ ir_node *cond_j = skip_Proj(pred_j);
+
+ if(cond_j == cond_i
+ && get_irn_opcode(cond_i) == iro_Cond
+ && get_irn_mode(get_Cond_selector(cond_i)) == mode_b) {
+
+ ir_node *jmp = new_r_Jmp(current_ir_graph, get_nodes_block(cond_i));
+ set_irn_n(bl, i, jmp);
+ set_irn_n(bl, j, new_Bad());
+
+ break;
+ }
+ }
+ }
+}
+
+
/**
* Removes Tuples from Block control flow predecessors.
* Optimizes blocks with equivalent_node(). This is tricky,
int i;
ir_node *new_block;
+ /* clear the link field for ALL nodes first */
set_irn_link(n, NULL);
if (get_irn_op(n) == op_Block) {
if (get_opt_normalize())
set_Block_cfgpred(n, i, skip_Tuple(get_Block_cfgpred(n, i)));
}
+
+ /* see below */
new_block = equivalent_node(n);
- if (new_block != n)
+ if (new_block != n && ! is_Bad(new_block))
exchange (n, new_block);
} else if (get_opt_optimize() && (get_irn_mode(n) == mode_X)) {
/* We will soon visit a block. Optimize it before visiting! */
- ir_node *b = get_nodes_block(n);
+ ir_node *b = get_nodes_block(skip_Proj(n));
if (!is_Bad(b)) {
new_block = equivalent_node(b);
while (irn_not_visited(b) && (!is_Bad(new_block)) && (new_block != b)) {
/* We would have to run gigo if new is bad, so we
- promote it directly below. Nevertheless, we somtimes reach a block
+ promote it directly below. Nevertheless, we sometimes reach a block
the first time through a dataflow node. In this case we optimized the
block as such and have to promote the Bad here. */
- assert(((b == new_block) ||
- get_opt_control_flow_straightening() ||
- get_opt_control_flow_weak_simplification()) &&
- ("strange flag setting"));
+ assert((get_opt_control_flow_straightening() ||
+ get_opt_control_flow_weak_simplification()) &&
+ ("strange flag setting"));
exchange (b, new_block);
b = new_block;
new_block = equivalent_node(b);
}
- b = new_block;
+
+ /* normally, we would create a Bad block here, but this must be
+ * prevented, so just set it's cf to Bad.
+ */
+ if (is_Bad(new_block))
+ exchange(n, new_Bad());
}
+ }
+}
+
+/**
+ * Remove cf from dead block by inspecting dominance info
+ * Do not replace blocks by Bad. This optimization shall
+ * ensure, that all Bad cfg preds are removed, and no new
+ * other Bads are introduced.
+ *
+ * Must be run in the post walker.
+ */
+static void remove_dead_block_cf(ir_node *block, void *env)
+{
+ int i, n;
+
+ /* check block predecessors and turn control flow into bad */
+ for (i = 0, n = get_Block_n_cfgpreds(block); i < n; ++i) {
+ ir_node *pred_X = get_Block_cfgpred(block, i);
- /*
- * BEWARE: do not kill floating notes here as they might be needed in
- * valid blocks because of global CSE.
- */
- if (is_Bad(b) && get_opt_normalize() &&
- get_op_pinned(get_irn_op(n)) == op_pin_state_pinned)
- exchange(n, new_Bad());
+ if (! is_Bad(pred_X)) {
+ ir_node *pred_bl = get_nodes_block(skip_Proj(pred_X));
+
+ if (is_Bad(pred_bl) || (get_Block_dom_depth(pred_bl) == -1))
+ exchange (pred_X, new_Bad());
+ }
}
}
* in the post walker, so we catch all blocks.
*/
static void collect_nodes(ir_node *n, void *env) {
- irg_dom_state *dom_state = env;
-
if (is_no_Block(n)) {
ir_node *b = get_nodes_block(n);
- /*
- * BEWARE: do not kill floating notes here as they might be needed in
- * valid blocks because of global CSE.
- */
- if (is_Bad(b) &&
- get_op_pinned(get_irn_op(n)) == op_pin_state_pinned) {
- /* previous merge_blocks() may have killed dead blocks */
- exchange(n, new_Bad());
- }
- else if ((get_irn_op(n) == op_Phi)) {
+ if ((get_irn_op(n) == op_Phi)) {
/* Collect Phi nodes to compact ins along with block's ins. */
set_irn_link(n, get_irn_link(b));
set_irn_link(b, n);
- } else if ((get_irn_op(n) != op_Jmp) && !is_Bad(b)) { /* Check for non empty block. */
- mark_Block_block_visited(b);
}
- }
- else {
- /* delete dead blocks: if we have dominator information, this can easily be detected
- * BEWARE: don't kill the end block */
- if (*dom_state == dom_consistent &&
- n != get_irg_end_block(current_ir_graph) &&
- get_Block_dom_depth(n) == -1 &&
- get_opt_unreachable_code()) {
- exchange (n, new_Bad());
+ else if ((get_irn_op(n) != op_Jmp) && !is_Bad(b)) { /* Check for non empty block. */
+ mark_Block_block_visited(b);
}
}
}
/** Returns true if pred is predecessor of block. */
static int is_pred_of(ir_node *pred, ir_node *b) {
- int i;
- for (i = 0; i < get_Block_n_cfgpreds(b); i++) {
+ int i, n;
+
+ for (i = 0, n = get_Block_n_cfgpreds(b); i < n; ++i) {
ir_node *b_pred = get_nodes_block(get_Block_cfgpred(b, i));
if (b_pred == pred) return 1;
}
}
+/** Test wether we can optimize away pred block pos of b.
+ *
+ * @param b A block node.
+ * @param pos The position of the predecessor block to judge about.
+ *
+ * @returns The number of predecessors
+ *
+ * The test is rather tricky.
+ *
+ * The situation is something like the following:
+ *
+ * if-block
+ * / \
+ * then-b else-b
+ * \ /
+ * b
+ *
+ * b merges the control flow of an if-then-else. We may not remove
+ * the 'then' _and_ the 'else' block of an 'if' if there is a Phi
+ * node in b, even if both are empty. The destruction of this Phi
+ * requires that a copy is added before the merge. We have to
+ * keep one of the case blocks to place the copies in.
+ *
+ * To perform the test for pos, we must regard preds before pos
+ * as already removed.
+ **/
static int test_whether_dispensable(ir_node *b, int pos) {
int i, j, n_preds = 1;
int dispensable = 1;
ir_node *cfop = get_Block_cfgpred(b, pos);
ir_node *pred = get_nodes_block(cfop);
+ /* Bad blocks will be optimized away, so we don't need space for them */
+ if (is_Bad(pred))
+ return 0;
+
if (get_Block_block_visited(pred) + 1
< get_irg_block_visited(current_ir_graph)) {
+
if (!get_opt_optimize() || !get_opt_control_flow_strong_simplification()) {
- /* Mark block so that is will not be removed. */
+ /* Mark block so that is will not be removed: optimization is turned off. */
set_Block_block_visited(pred, get_irg_block_visited(current_ir_graph)-1);
return 1;
}
- /* Seems to be empty. */
+
+ /* Seems to be empty. At least we detected this in collect_nodes. */
if (!get_irn_link(b)) {
- /* There are no Phi nodes ==> dispensable. */
+ /* There are no Phi nodes ==> all predecessors are dispensable. */
n_preds = get_Block_n_cfgpreds(pred);
} else {
/* b's pred blocks and pred's pred blocks must be pairwise disjunct.
return n_preds;
}
+
+/**
+ * This method removed Bad cf preds from Blocks and Phis, and removes
+ * empty blocks. A block is empty if it only contains Phi and Jmp nodes.
+ *
+ * We first adapt Phi nodes, then Block nodes, as we need the old ins
+ * of the Block to adapt the Phi nodes. We do this by computing new
+ * in arrays, and then replacing the old ones. So far we compute new in arrays
+ * for all nodes, not regarding whether there is a possibility for optimization.
+ *
+ * For each predecessor p of a Block b there are three cases:
+ * 1. The predecessor p is a Bad node: just skip it. The in array of b shrinks by one.
+ * 2. The predecessor p is empty. Remove p. All predecessors of p are now
+ * predecessors of b.
+ * 3. The predecessor p is a block containing useful code. Just keep p as is.
+ *
+ * For Phi nodes f we have to check the conditions at the Block of f.
+ * For cases 1 and 3 we proceed as for Blocks. For case 2 we can have two
+ * cases:
+ * 2a: The old precessor of the Phi f is a Phi pred_f IN THE BLOCK REMOVED. In this
+ * case we proceed as for blocks. We remove pred_f. All
+ * predecessors of pred_f now are predecessors of f.
+ * 2b: The old predecessor of f is NOT in the block removed. It might be a Phi, too.
+ * We have to replicate f for each predecessor of the removed block. Or, with
+ * other words, the removed predecessor block has exactly one predecessor.
+ *
+ * Further there is a special case for self referencing blocks:
+ *
+ * then_b else_b then_b else_b
+ * \ / \ /
+ * \ / | /
+ * pred_b | /
+ * | ____ | /
+ * | | | | | | |
+ * | | | === optimized to ===> \ | | |
+ * loop_b | loop_b |
+ * | | | | | |
+ * | |____| | |____|
+ * | |
+ *
+ * If there is a Phi in pred_b, but we remove pred_b, we have to generate a
+ * Phi in loop_b, that has the ins of the Phi in pred_b and a self referencing
+ * backedge.
+ * @@@ It is negotiable whether we should do this ... there might end up a copy
+ * from the Phi in the loop when removing the Phis.
+ */
static void optimize_blocks(ir_node *b, void *env) {
- int i, j, k, max_preds, n_preds;
+ int i, j, k, n, max_preds, n_preds, p_preds;
ir_node *pred, *phi;
ir_node **in;
/* Count the number of predecessor if this block is merged with pred blocks
that are empty. */
max_preds = 0;
- for (i = 0; i < get_Block_n_cfgpreds(b); i++) {
+ for (i = 0, k = get_Block_n_cfgpreds(b); i < k; ++i) {
max_preds += test_whether_dispensable(b, i);
}
- in = (ir_node **) malloc(max_preds * sizeof(ir_node *));
+ in = xmalloc(max_preds * sizeof(*in));
/*-
printf(" working on "); DDMN(b);
}
* end Debug output -*/
- /*- Fix the Phi nodes -*/
- phi = get_irn_link(b);
- while (phi) {
+ /*- Fix the Phi nodes of the current block -*/
+ for (phi = get_irn_link(b); phi; ) {
assert(get_irn_op(phi) == op_Phi);
+
/* Find the new predecessors for the Phi */
- n_preds = 0;
- for (i = 0; i < get_Block_n_cfgpreds(b); i++) {
+ p_preds = 0;
+ for (i = 0, n = get_Block_n_cfgpreds(b); i < n; ++i) {
pred = get_nodes_block(get_Block_cfgpred(b, i));
+
if (is_Bad(get_Block_cfgpred(b, i))) {
- /* Do nothing */
- } else if (get_Block_block_visited(pred) + 1
+ /* case Phi 1: Do nothing */
+ }
+ else if (get_Block_block_visited(pred) + 1
< get_irg_block_visited(current_ir_graph)) {
- /* It's an empty block and not yet visited. */
+ /* case Phi 2: It's an empty block and not yet visited. */
ir_node *phi_pred = get_Phi_pred(phi, i);
- for (j = 0; j < get_Block_n_cfgpreds(pred); j++) {
- if (get_nodes_block(phi_pred) == pred) {
- assert(get_irn_op(phi_pred) == op_Phi); /* Block is empty!! */
- in[n_preds] = get_Phi_pred(phi_pred, j);
- } else {
- in[n_preds] = phi_pred;
+ for (j = 0, k = get_Block_n_cfgpreds(pred); j < k; j++) {
+ /* because of breaking loops, not all predecessors are Bad-clean,
+ * so we must check this here again */
+ if (! is_Bad(get_Block_cfgpred(pred, j))) {
+ if (get_nodes_block(phi_pred) == pred) {
+ /* case Phi 2a: */
+ assert(get_irn_op(phi_pred) == op_Phi); /* Block is empty!! */
+
+ in[p_preds++] = get_Phi_pred(phi_pred, j);
+ } else {
+ /* case Phi 2b: */
+ in[p_preds++] = phi_pred;
+ }
}
- n_preds++;
}
+
/* The Phi_pred node is replaced now if it is a Phi.
- In Schleifen kann offenbar der entfernte Phi Knoten legal verwendet werden.
- Daher muss der Phiknoten durch den neuen ersetzt werden.
- Weiter muss der alte Phiknoten entfernt werden (durch ersetzen oder
- durch einen Bad) damit er aus den keep_alive verschwinden kann.
- Man sollte also, falls keine Schleife vorliegt, exchange mit new_Bad
- aufrufen. */
+
+ Somehow the removed Phi node can be used legally in loops.
+ Therefore we replace the old phi by the new one.
+
+ Further we have to remove the old Phi node by replacing it
+ by Bad. Else it will remain in the keepalive array of End
+ and cause illegal situations. So if there is no loop, we should
+ replace it by Bad.
+ */
if (get_nodes_block(phi_pred) == pred) {
/* remove the Phi as it might be kept alive. Further there
might be other users. */
exchange(phi_pred, phi); /* geht, ist aber doch semantisch falsch! Warum?? */
}
} else {
- in[n_preds] = get_Phi_pred(phi, i);
- n_preds ++;
+ /* case Phi 3: */
+ in[p_preds++] = get_Phi_pred(phi, i);
}
}
+ assert(p_preds <= max_preds);
+
/* Fix the node */
- if (n_preds == 1)
+ if (p_preds == 1)
+ /* By removal of Bad ins the Phi might be degenerated. */
exchange(phi, in[0]);
else
- set_irn_in(phi, n_preds, in);
+ set_irn_in(phi, p_preds, in);
phi = get_irn_link(phi);
}
- /*- This happens only if merge between loop backedge and single loop entry. -*/
- for (k = 0; k < get_Block_n_cfgpreds(b); k++) {
+ /*- This happens only if merge between loop backedge and single loop entry.
+ See special case above. -*/
+ for (k = 0, n = get_Block_n_cfgpreds(b); k < n; ++k) {
pred = get_nodes_block(get_Block_cfgpred(b, k));
- if (get_Block_block_visited(pred)+1 < get_irg_block_visited(current_ir_graph)) {
- phi = get_irn_link(pred);
- while (phi) {
+
+ if (get_Block_block_visited(pred) + 1 < get_irg_block_visited(current_ir_graph)) {
+ /* we found a predecessor block at position k that will be removed */
+ for (phi = get_irn_link(pred); phi;) {
+ /*
+ * the previous phase may already changed the phi, and even
+ * removed it at all, so check here if this node is still a phi
+ */
if (get_irn_op(phi) == op_Phi) {
+ int q_preds = 0;
+
+ /* move this phi from the predecessor into the block b */
set_nodes_block(phi, b);
- n_preds = 0;
+ /* first, copy all 0..k-1 predecessors */
for (i = 0; i < k; i++) {
pred = get_nodes_block(get_Block_cfgpred(b, i));
+
if (is_Bad(get_Block_cfgpred(b, i))) {
/* Do nothing */
- } else if (get_Block_block_visited(pred) +1
+ } else if (get_Block_block_visited(pred) + 1
< get_irg_block_visited(current_ir_graph)) {
/* It's an empty block and not yet visited. */
for (j = 0; j < get_Block_n_cfgpreds(pred); j++) {
/* @@@ Hier brauche ich Schleifeninformation!!! Kontrollflusskante
- muss Rueckwaertskante sein! (An allen vier in[n_preds] = phi
+ muss Rueckwaertskante sein! (An allen vier in[q_preds] = phi
Anweisungen.) Trotzdem tuts bisher!! */
- in[n_preds] = phi;
- n_preds++;
+ if (! is_Bad(get_Block_cfgpred(pred, j)))
+ in[q_preds++] = phi;
}
} else {
- in[n_preds] = phi;
- n_preds++;
+ in[q_preds++] = phi;
}
}
+
+ /* now we are at k, copy the phi predecessors */
+ pred = get_nodes_block(get_Block_cfgpred(b, k));
for (i = 0; i < get_Phi_n_preds(phi); i++) {
- in[n_preds] = get_Phi_pred(phi, i);
- n_preds++;
+ if (! is_Bad(get_Block_cfgpred(pred, i)))
+ in[q_preds++] = get_Phi_pred(phi, i);
}
+
+ /* and now all the rest */
for (i = k+1; i < get_Block_n_cfgpreds(b); i++) {
pred = get_nodes_block(get_Block_cfgpred(b, i));
+
if (is_Bad(get_Block_cfgpred(b, i))) {
/* Do nothing */
} else if (get_Block_block_visited(pred) +1
< get_irg_block_visited(current_ir_graph)) {
/* It's an empty block and not yet visited. */
for (j = 0; j < get_Block_n_cfgpreds(pred); j++) {
- in[n_preds] = phi;
- n_preds++;
+ if (! is_Bad(get_Block_cfgpred(pred, j)))
+ in[q_preds++] = phi;
}
} else {
- in[n_preds] = phi;
- n_preds++;
+ in[q_preds++] = phi;
}
}
- if (n_preds == 1)
+
+ /* Fix the node */
+ if (q_preds == 1)
exchange(phi, in[0]);
else
- set_irn_in(phi, n_preds, in);
+ set_irn_in(phi, q_preds, in);
+
+ assert(q_preds <= max_preds);
+// assert(p_preds == q_preds && "Wrong Phi Fix");
}
phi = get_irn_link(phi);
}
n_preds = 0;
for (i = 0; i < get_Block_n_cfgpreds(b); i++) {
pred = get_nodes_block(get_Block_cfgpred(b, i));
+
if (is_Bad(get_Block_cfgpred(b, i))) {
- /* Do nothing */
+ /* case 1: Do nothing */
} else if (get_Block_block_visited(pred) +1
< get_irg_block_visited(current_ir_graph)) {
- /* It's an empty block and not yet visited. */
+ /* case 2: It's an empty block and not yet visited. */
assert(get_Block_n_cfgpreds(b) > 1);
/* Else it should be optimized by equivalent_node. */
for (j = 0; j < get_Block_n_cfgpreds(pred); j++) {
- in[n_preds] = get_Block_cfgpred(pred, j);
- n_preds++;
+ ir_node *pred_block = get_Block_cfgpred(pred, j);
+
+ /* because of breaking loops, not all predecessors are Bad-clean,
+ * so we must check this here again */
+ if (! is_Bad(pred_block))
+ in[n_preds++] = pred_block;
}
/* Remove block as it might be kept alive. */
exchange(pred, b/*new_Bad()*/);
} else {
- in[n_preds] = get_Block_cfgpred(b, i);
- n_preds ++;
+ /* case 3: */
+ in[n_preds++] = get_Block_cfgpred(b, i);
}
}
+ assert(n_preds <= max_preds);
+
set_irn_in(b, n_preds, in);
- free(in);
+
+ assert(get_irn_link(b) == NULL || (n_preds == p_preds && "Wrong Phi Fix"));
+
+ xfree(in);
}
+
+/* Optimizations of the control flow that also require changes of Phi nodes.
+ *
+ * This optimization performs two passes over the graph.
+ *
+ * The first pass collects all Phi nodes in a link list in the block
+ * nodes. Further it performs simple control flow optimizations.
+ * Finally it marks all blocks that do not contain useful
+ * computations, i.e., these blocks might be removed.
+ *
+ * The second pass performs the optimizations intended by this algorithm.
+ * It walks only over block nodes and adapts these and the Phi nodes in these blocks,
+ * which it finds in a linked list computed by the first pass.
+ *
+ * We use the block_visited flag to mark empty blocks in the first
+ * phase.
+ * @@@ It would be better to add a struct in the link field
+ * that keeps the Phi list and the mark. Place it on an obstack, as
+ * we will lose blocks and thereby generate mem leaks.
+ */
void optimize_cf(ir_graph *irg) {
- int i;
+ int i, n;
ir_node **in;
ir_node *end = get_irg_end(irg);
ir_graph *rem = current_ir_graph;
if (get_irg_dom_state(current_ir_graph) == dom_consistent)
set_irg_dom_inconsistent(current_ir_graph);
+ if (dom_state == dom_consistent && get_opt_optimize() && get_opt_unreachable_code()) {
+ ir_node *end = get_irg_end(irg);
+
+ /* we have dominace info, we can kill dead block */
+ irg_block_walk_graph(irg, NULL, remove_dead_block_cf, NULL);
+
+ /* fix the keep-alives */
+ for (i = 0, n = get_End_n_keepalives(end); i < n; ++i) {
+ ir_node *ka = get_End_keepalive(end, i);
+
+ if (is_Block(ka) && (get_Block_dom_depth(ka) == -1))
+ set_End_keepalive(end, i, new_Bad());
+ if (is_Phi(ka) && (get_Block_dom_depth(get_nodes_block(ka)) == -1))
+ set_End_keepalive(end, i, new_Bad());
+ }
+ }
+
+ irg_block_walk_graph(current_ir_graph, NULL, remove_senseless_conds, NULL);
/* Use block visited flag to mark non-empty blocks. */
inc_irg_block_visited(irg);
- irg_walk(end, merge_blocks, collect_nodes, &dom_state);
+ irg_walk(end, merge_blocks, collect_nodes, NULL);
/* Optimize the standard code. */
irg_block_walk(get_irg_end_block(irg), optimize_blocks, NULL, NULL);
in = NEW_ARR_F (ir_node *, 1);
in[0] = get_nodes_block(end);
inc_irg_visited(current_ir_graph);
- for(i = 0; i < get_End_n_keepalives(end); i++) {
+
+ for (i = 0; i < get_End_n_keepalives(end); i++) {
ir_node *ka = get_End_keepalive(end, i);
+
if (irn_not_visited(ka)) {
if ((get_irn_op(ka) == op_Block) && Block_not_block_visited(ka)) {
set_irg_block_visited(current_ir_graph, /* Don't walk all the way to Start. */
/* DEL_ARR_F(end->in); GL @@@ tut nicht ! */
end->in = in;
- /* after optimize_cf(), only Bad data flow may remain. */
- if (irg_vrfy_bads(irg, BAD_DF | BAD_BLOCK | TUPLE)) {
- dump_ir_block_graph(irg, "-vrfy-cf");
- dump_ir_graph(irg, "-vrfy-cf");
- fprintf(stderr, "VRFY_BAD in optimize_cf()\n");
+
+ /* the verifyer doesn't work yet with floating nodes */
+ if (get_irg_pinned(irg) == op_pin_state_pinned) {
+ /* after optimize_cf(), only Bad data flow may remain. */
+ if (irg_vrfy_bads(irg, BAD_DF | BAD_BLOCK | TUPLE)) {
+ dump_ir_block_graph(irg, "-vrfy-cf");
+ dump_ir_graph(irg, "-vrfy-cf");
+ fprintf(stderr, "VRFY_BAD in optimize_cf()\n");
+ }
}
current_ir_graph = rem;
projects / libfirm / blobdiff