* @file
* @brief Control flow optimizations.
* @author Goetz Lindenmaier, Michael Beck, Sebastian Hack
- * @version $Id$
*
* 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
#include "irflag_t.h"
#include "firmstat.h"
#include "irpass.h"
+#include "irnodehashmap.h"
+#include "irtools.h"
#include "iropt_dbg.h"
typedef struct merge_env {
bool changed; /**< Set if the graph was changed. */
bool phis_moved; /**< Set if Phi nodes were moved. */
- ir_node **switch_conds; /**< Helper list for all found Switch Conds. */
} merge_env;
+/** set or reset the removable property of a block. */
static void set_Block_removable(ir_node *block, bool removable)
{
set_Block_mark(block, removable);
}
-static bool is_Block_removable(ir_node *block)
+/** check if a block has the removable property set. */
+static bool is_Block_removable(const ir_node *block)
{
return get_Block_mark(block);
}
-static void clear_link(ir_node *node, void *ctx)
+/** checks if a given Cond node is a switch Cond. */
+static bool is_switch_Cond(const ir_node *cond)
+{
+ ir_node *sel = get_Cond_selector(cond);
+ return get_irn_mode(sel) != mode_b;
+}
+
+/** Walker: clear link fields and mark all blocks as removable. */
+static void clear_link_and_mark_blocks_removable(ir_node *node, void *ctx)
{
(void) ctx;
set_irn_link(node, NULL);
- if (is_Block(node))
+ if (is_Block(node)) {
set_Block_removable(node, true);
+ set_Block_phis(node, NULL);
+ } else if (is_Phi(node)) {
+ set_Phi_next(node, NULL);
+ }
}
/**
*/
static void collect_nodes(ir_node *n, void *ctx)
{
- merge_env *env = (merge_env*)ctx;
-
+ (void) ctx;
if (is_Phi(n)) {
/* Collect Phi nodes to compact ins along with block's ins. */
ir_node *block = get_nodes_block(n);
- set_irn_link(n, get_irn_link(block));
- set_irn_link(block, n);
+ add_Block_phi(block, n);
} else if (is_Block(n)) {
- if (has_Block_entity(n))
+ if (get_Block_entity(n) != NULL) {
+ /* block with a jump label attached cannot be removed. */
set_Block_removable(n, false);
+ }
+ } else if (is_Bad(n) || is_Jmp(n)) {
+ /* ignore these */
return;
- } else if (!is_Jmp(n)) { /* Check for non-empty block. */
+ } else {
+ /* Check for non-empty block. */
ir_node *block = get_nodes_block(n);
+
set_Block_removable(block, false);
if (is_Proj(n)) {
ir_node *pred = get_Proj_pred(n);
set_irn_link(n, get_irn_link(pred));
set_irn_link(pred, n);
- } else if (is_Cond(n)) {
- ir_node *sel = get_Cond_selector(n);
- if (get_irn_mode(sel) != mode_b) {
- /* found a switch-Cond, collect */
- ARR_APP1(ir_node*, env->switch_conds, n);
- }
}
}
}
-/** Returns true if pred is predecessor of block. */
-static bool is_pred_of(ir_node *pred, ir_node *b)
+/** Returns true if pred is predecessor of block b. */
+static bool is_pred_of(const ir_node *pred, const ir_node *b)
{
int i;
return false;
}
-static unsigned count_non_bad_inputs(const ir_node *node)
-{
- int arity = get_irn_arity(node);
- unsigned result = 0;
- int i;
-
- for (i = 0; i < arity; ++i) {
- ir_node *in = get_irn_n(node, i);
- if (!is_Bad(in))
- ++result;
- }
- return result;
-}
-
/** Test whether we can optimize away pred block pos of b.
*
* @param b A block node.
* To perform the test for pos, we must regard predecessors before pos
* as already removed.
**/
-static unsigned test_whether_dispensable(ir_node *b, int pos)
+static unsigned test_whether_dispensable(const ir_node *b, int pos)
{
ir_node *pred = get_Block_cfgpred(b, pos);
ir_node *predb = get_nodes_block(pred);
- /* Bad blocks will be optimized away, so we don't need space for them */
- if (is_Bad(pred))
- return 0;
- if (!is_Block_removable(predb))
+ if (is_Bad(pred) || !is_Block_removable(predb))
return 1;
+
/* can't remove self-loops */
if (predb == b)
goto non_dispensable;
goto non_dispensable;
/* Seems to be empty. At least we detected this in collect_nodes. */
- if (get_irn_link(b) != NULL) {
+ if (get_Block_phis(b) != NULL) {
int n_cfgpreds = get_Block_n_cfgpreds(b);
int i;
/* there are Phi nodes */
if (Block_block_visited(predb))
return 1;
/* if we get here, the block is dispensable, count useful preds */
- return count_non_bad_inputs(predb);
+ return get_irn_arity(predb);
non_dispensable:
set_Block_removable(predb, false);
}
/**
- * This method removed Bad cf predecessors from Blocks and Phis, and removes
- * empty blocks. A block is empty if it only contains Phi and Jmp nodes.
+ * This method merges blocks. A block is applicable to be merged, if it
+ * has only one predecessor with an unconditional jump to this block;
+ * and if this block does not contain any phis.
+ */
+static void merge_blocks(ir_node *b, void *env)
+{
+ (void) env;
+
+ if (get_Block_n_cfgpreds(b) == 1) {
+ ir_node* pred = get_Block_cfgpred(b, 0);
+ if (is_Jmp(pred)) {
+ ir_node* pred_block = get_nodes_block(pred);
+ if (get_Block_phis(b) == NULL) {
+ exchange(b, pred_block);
+ }
+ }
+ }
+}
+
+/**
+ * This method 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
static void optimize_blocks(ir_node *b, void *ctx)
{
int i, j, k, n, max_preds, n_preds, p_preds = -1;
- ir_node *pred, *phi, *next;
+ ir_node *phi;
+ ir_node *next;
ir_node **in;
merge_env *env = (merge_env*)ctx;
+ if (get_Block_dom_depth(b) < 0) {
+ /* ignore unreachable blocks */
+ return;
+ }
+
/* Count the number of predecessor if this block is merged with pred blocks
that are empty. */
max_preds = 0;
in = XMALLOCN(ir_node*, max_preds);
/*- Fix the Phi nodes of the current block -*/
- for (phi = (ir_node*)get_irn_link(b); phi != NULL; phi = (ir_node*)next) {
- assert(is_Phi(phi));
- next = (ir_node*)get_irn_link(phi);
+ for (phi = get_Block_phis(b); phi != NULL; phi = next) {
+ next = get_Phi_next(phi);
/* Find the new predecessors for the Phi */
p_preds = 0;
for (i = 0, n = get_Block_n_cfgpreds(b); i < n; ++i) {
- pred = get_Block_cfgpred_block(b, i);
+ ir_graph *irg = get_irn_irg(b);
+ ir_node *predx = get_Block_cfgpred(b, i);
+ ir_node *pred;
+
+ /* case Phi 1: maintain Bads, as somebody else is responsible to
+ * remove them */
+ if (is_Bad(predx)) {
+ in[p_preds++] = new_r_Bad(irg, get_irn_mode(phi));
+ continue;
+ }
- if (is_Bad(pred)) {
- /* case Phi 1: Do nothing */
- } else if (is_Block_removable(pred) && !Block_block_visited(pred)) {
- /* case Phi 2: It's an empty block and not yet visited. */
+ pred = get_nodes_block(predx);
+
+ /* case Phi 2: It's an empty block and not yet visited. */
+ if (is_Block_removable(pred) && !Block_block_visited(pred)) {
ir_node *phi_pred = get_Phi_pred(phi, i);
for (j = 0, k = get_Block_n_cfgpreds(pred); j < k; j++) {
ir_node *pred_pred = 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_pred))
+
+ if (is_Bad(pred_pred)) {
+ in[p_preds++] = new_r_Bad(irg, get_irn_mode(phi));
continue;
+ }
if (get_nodes_block(phi_pred) == pred) {
/* case Phi 2a: */
- assert(is_Phi(phi_pred)); /* Block is empty!! */
-
in[p_preds++] = get_Phi_pred(phi_pred, j);
} else {
/* case Phi 2b: */
assert(p_preds == max_preds);
/* Fix the node */
- if (p_preds == 1)
- /* By removal of Bad ins the Phi might be degenerated. */
+ if (p_preds == 1) {
exchange(phi, in[0]);
- else
+ } else {
set_irn_in(phi, p_preds, in);
+ }
env->changed = true;
}
ir_node *next_phi;
/* we found a predecessor block at position k that will be removed */
- for (phi = (ir_node*)get_irn_link(predb); phi; phi = next_phi) {
+ for (phi = get_Block_phis(predb); phi != NULL; phi = next_phi) {
int q_preds = 0;
- next_phi = (ir_node*)get_irn_link(phi);
-
- assert(is_Phi(phi));
+ next_phi = get_Phi_next(phi);
if (get_Block_idom(b) != predb) {
- /* predb is not the dominator. There can't be uses of pred's Phi nodes, kill them .*/
- ir_graph *irg = get_irn_irg(b);
- exchange(phi, get_irg_bad(irg));
+ /* predb is not the dominator. There can't be uses of
+ * pred's Phi nodes, kill them .*/
+ ir_graph *irg = get_irn_irg(b);
+ ir_mode *mode = get_irn_mode(phi);
+ exchange(phi, new_r_Bad(irg, mode));
} else {
- /* predb is the direct dominator of b. There might be uses of the Phi nodes from
- predb in further block, so move this phi from the predecessor into the block b */
+ /* predb is the direct dominator of b. There might be uses
+ * of the Phi nodes from predb in further block, so move
+ * this phi from the predecessor into the block b */
set_nodes_block(phi, b);
- set_irn_link(phi, get_irn_link(b));
- set_irn_link(b, phi);
+ set_Phi_next(phi, get_Block_phis(b));
+ set_Block_phis(b, phi);
env->phis_moved = true;
/* first, copy all 0..k-1 predecessors */
for (i = 0; i < k; i++) {
- pred = get_Block_cfgpred_block(b, i);
-
- if (is_Bad(pred)) {
- /* Do nothing */
- } else if (is_Block_removable(pred) && !Block_block_visited(pred)) {
+ ir_node *predx = get_Block_cfgpred(b, i);
+ ir_node *pred_block;
+
+ if (is_Bad(predx)) {
+ ir_graph *irg = get_irn_irg(b);
+ ir_mode *mode = get_irn_mode(phi);
+ in[q_preds++] = new_r_Bad(irg, mode);
+ continue;
+ }
+ pred_block = get_nodes_block(predx);
+ if (is_Block_removable(pred_block)
+ && !Block_block_visited(pred_block)) {
+ int n_cfgpreds = get_Block_n_cfgpreds(pred_block);
/* It's an empty block and not yet visited. */
- for (j = 0; j < get_Block_n_cfgpreds(pred); j++) {
- if (! is_Bad(get_Block_cfgpred(pred, j)))
+ for (j = 0; j < n_cfgpreds; j++) {
+ if (!is_Bad(get_Block_cfgpred(pred_block, j))) {
in[q_preds++] = phi;
+ } else {
+ ir_graph *irg = get_irn_irg(b);
+ ir_mode *mode = get_irn_mode(phi);
+ in[q_preds++] = new_r_Bad(irg, mode);
+ }
}
} else {
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++) {
- if (! is_Bad(get_Block_cfgpred(pred, i)))
- in[q_preds++] = get_Phi_pred(phi, i);
+ in[q_preds++] = get_Phi_pred(phi, i);
}
/* and now all the rest */
pred = get_Block_cfgpred_block(b, i);
if (is_Bad(pred)) {
- /* Do nothing */
+ ir_graph *irg = get_irn_irg(b);
+ ir_mode *mode = get_irn_mode(phi);
+ in[q_preds++] = new_r_Bad(irg, mode);
} else if (is_Block_removable(pred) && !Block_block_visited(pred)) {
/* It's an empty block and not yet visited. */
for (j = 0; j < get_Block_n_cfgpreds(pred); j++) {
- if (! is_Bad(get_Block_cfgpred(pred, j)))
+ if (! is_Bad(get_Block_cfgpred(pred, j))) {
in[q_preds++] = phi;
+ } else {
+ ir_graph *irg = get_irn_irg(b);
+ ir_mode *mode = get_irn_mode(phi);
+ in[q_preds++] = new_r_Bad(irg, mode);
+ }
}
} else {
in[q_preds++] = phi;
for (i = 0; i < get_Block_n_cfgpreds(b); i++) {
ir_node *pred = get_Block_cfgpred(b, i);
ir_node *predb = get_nodes_block(pred);
+ ir_graph *irg = get_irn_irg(pred);
- /* case 1: Do nothing */
- if (is_Bad(pred))
+ /* case 1: Bad predecessor */
+ if (is_Bad(pred)) {
+ in[n_preds++] = new_r_Bad(irg, mode_X);
continue;
+ }
if (is_Block_removable(predb) && !Block_block_visited(predb)) {
/* case 2: It's an empty block and not yet visited. */
for (j = 0; j < get_Block_n_cfgpreds(predb); j++) {
ir_node *predpred = get_Block_cfgpred(predb, j);
- /* because of breaking loops, not all predecessors are
- * Bad-clean, so we must check this here again */
- if (is_Bad(predpred))
+ if (is_Bad(predpred)) {
+ in[n_preds++] = new_r_Bad(irg, mode_X);
continue;
+ }
+
in[n_preds++] = predpred;
}
/* Remove block+jump as it might be kept alive. */
- exchange(pred, get_irg_bad(get_irn_irg(b)));
- exchange(predb, get_irg_bad(get_irn_irg(b)));
+ exchange(pred, new_r_Bad(get_irn_irg(b), mode_X));
+ exchange(predb, new_r_Bad(get_irn_irg(b), mode_BB));
} else {
/* case 3: */
in[n_preds++] = pred;
env->changed = true;
/* see if phi-fix was correct */
- assert(get_irn_link(b) == NULL || p_preds == -1 || (n_preds == p_preds));
+ assert(get_Block_phis(b) == NULL || p_preds == -1 || (n_preds == p_preds));
xfree(in);
}
/**
- * Block walker: optimize all blocks using the default optimizations.
- * This removes Blocks with only a Jmp predecessor.
+ * Optimize boolean Conds, where true and false jump to the same block into a Jmp
+ * Block must contain no Phi nodes.
+ *
+ * Cond
+ * / \
+ * projA projB => Jmp Bad
+ * \ / \ /
+ * block block
*/
-static void remove_simple_blocks(ir_node *block, void *ctx)
+static bool optimize_pred_cond(ir_node *block, int i, int j)
{
- merge_env *env = (merge_env*)ctx;
- ir_node *new_blk = equivalent_node(block);
+ ir_node *projA, *projB, *cond, *pred_block, *jmp, *bad;
+ assert(i != j);
+
+ projA = get_Block_cfgpred(block, i);
+ if (!is_Proj(projA)) return false;
+ projB = get_Block_cfgpred(block, j);
+ if (!is_Proj(projB)) return false;
+ cond = get_Proj_pred(projA);
+ if (!is_Cond(cond)) return false;
+
+ if (cond != get_Proj_pred(projB)) return false;
+ if (is_switch_Cond(cond)) return false;
+
+ /* cond should actually be a Jmp */
+ pred_block = get_nodes_block(cond);
+ jmp = new_r_Jmp(pred_block);
+ bad = new_r_Bad(get_irn_irg(block), mode_X);
+
+ assert(projA != projB);
+ exchange(projA, jmp);
+ exchange(projB, bad);
+ return true;
+}
- if (new_blk != block) {
- exchange(block, new_blk);
- env->changed = true;
+typedef enum block_flags_t {
+ BF_HAS_OPERATIONS = 1 << 0,
+ BF_HAS_PHIS = 1 << 1,
+ BF_IS_UNKNOWN_JUMP_TARGET = 1 << 2,
+} block_flags_t;
+
+static bool get_block_flag(const ir_nodehashmap_t *infos, const ir_node *block,
+ int flag)
+{
+ return PTR_TO_INT(ir_nodehashmap_get(void, infos, block)) & flag;
+}
+
+static void set_block_flag(ir_nodehashmap_t *infos, ir_node *block,
+ block_flags_t flag)
+{
+ int data = PTR_TO_INT(ir_nodehashmap_get(void, infos, block));
+ data |= flag;
+ ir_nodehashmap_insert(infos, block, INT_TO_PTR(data));
+}
+
+static void clear_block_flag(ir_nodehashmap_t *infos, const ir_node *block)
+{
+ ir_nodehashmap_remove(infos, block);
+}
+
+static bool has_operations(ir_nodehashmap_t *infos, const ir_node *block)
+{
+ return get_block_flag(infos, block, BF_HAS_OPERATIONS);
+}
+
+static void set_has_operations(ir_nodehashmap_t *infos, ir_node *block)
+{
+ set_block_flag(infos, block, BF_HAS_OPERATIONS);
+}
+
+static bool has_phis(ir_nodehashmap_t *infos, const ir_node *block)
+{
+ return get_block_flag(infos, block, BF_HAS_PHIS);
+}
+
+static void set_has_phis(ir_nodehashmap_t *infos, ir_node *block)
+{
+ set_block_flag(infos, block, BF_HAS_PHIS);
+}
+
+static bool is_unknown_jump_target(ir_nodehashmap_t *infos, const ir_node *block)
+{
+ return get_block_flag(infos, block, BF_IS_UNKNOWN_JUMP_TARGET);
+}
+
+static void set_is_unknown_jump_target(ir_nodehashmap_t *infos, ir_node *block)
+{
+ set_block_flag(infos, block, BF_IS_UNKNOWN_JUMP_TARGET);
+}
+
+/**
+ * Pre-Walker: fill block info information.
+ */
+static void compute_block_info(ir_node *n, void *x)
+{
+ ir_nodehashmap_t *infos = (ir_nodehashmap_t*)x;
+
+ if (is_Block(n)) {
+ int i, max = get_Block_n_cfgpreds(n);
+ for (i=0; i<max; i++) {
+ ir_node *pred = get_Block_cfgpred(n,i);
+ if (is_unknown_jump(pred)) {
+ set_is_unknown_jump_target(infos, n);
+ }
+ }
+ } else if (is_Phi(n)) {
+ ir_node *block = get_nodes_block(n);
+ set_has_phis(infos, block);
+ } else if (is_Jmp(n) || is_Cond(n) || is_Proj(n)) {
+ /* ignore */
+ } else {
+ ir_node *block = get_nodes_block(n);
+ set_has_operations(infos, block);
}
}
+static void clear_block_info(ir_node *block, void *x)
+{
+ ir_nodehashmap_t *infos = (ir_nodehashmap_t*)x;
+ clear_block_flag(infos, block);
+}
+
+typedef struct skip_env {
+ bool changed;
+ ir_nodehashmap_t block_infos;
+} skip_env;
+
/**
- * Optimize table-switch Conds.
- *
- * @param cond the switch-Cond
- * @return true if the switch-Cond was optimized
+ * Post-Block-walker: Optimize useless if's (boolean Cond nodes
+ * with same true/false target) away.
*/
-static bool handle_switch_cond(ir_node *cond)
+static void optimize_ifs(ir_node *block, void *x)
{
- ir_node *sel = get_Cond_selector(cond);
- ir_node *proj1 = (ir_node*)get_irn_link(cond);
- ir_node *proj2 = (ir_node*)get_irn_link(proj1);
- ir_node *blk = get_nodes_block(cond);
-
- /* exactly 1 Proj on the Cond node: must be the defaultProj */
- if (proj2 == NULL) {
- ir_node *jmp = new_r_Jmp(blk);
- assert(get_Cond_default_proj(cond) == get_Proj_proj(proj1));
- /* convert it into a Jmp */
- exchange(proj1, jmp);
- return true;
+ skip_env *env = (skip_env*)x;
+ int i, j;
+ int n_preds = get_Block_n_cfgpreds(block);
+
+ if (has_phis(&env->block_infos, block))
+ return;
+
+ /* optimize Cond predecessors (might produce Bad predecessors) */
+ for (i = 0; i < n_preds; ++i) {
+ for (j = i+1; j < n_preds; ++j) {
+ optimize_pred_cond(block, i, j);
+ }
}
+}
- /* handle Cond nodes with constant argument. In this case the localopt rules
- * should have killed all obviously impossible cases.
- * So the only case left to handle here is 1 defaultProj + 1case
- * (this one case should be the one taken) */
- if (get_irn_link(proj2) == NULL) {
- ir_tarval *tv = value_of(sel);
-
- if (tv != tarval_bad) {
- /* we have a constant switch */
- long num = get_tarval_long(tv);
- long def_num = get_Cond_default_proj(cond);
- ir_graph *irg = get_irn_irg(cond);
- ir_node *bad = get_irg_bad(irg);
-
- if (def_num == get_Proj_proj(proj1)) {
- /* first one is the defProj */
- if (num == get_Proj_proj(proj2)) {
- ir_node *jmp = new_r_Jmp(blk);
- exchange(proj2, jmp);
- exchange(proj1, bad);
- return true;
- }
- } else if (def_num == get_Proj_proj(proj2)) {
- /* second one is the defProj */
- if (num == get_Proj_proj(proj1)) {
- ir_node *jmp = new_r_Jmp(blk);
- exchange(proj1, jmp);
- exchange(proj2, bad);
- return true;
- }
- } else {
- /* neither: strange, Cond was not optimized so far */
- if (num == get_Proj_proj(proj1)) {
- ir_node *jmp = new_r_Jmp(blk);
- exchange(proj1, jmp);
- exchange(proj2, bad);
- return true;
- } else if (num == get_Proj_proj(proj2)) {
- ir_node *jmp = new_r_Jmp(blk);
- exchange(proj2, jmp);
- exchange(proj1, bad);
- return true;
- }
+/**
+ * Pre-Block walker: remove empty blocks (only contain a Jmp)
+ * that are control flow predecessors of the current block.
+ */
+static void remove_empty_blocks(ir_node *block, void *x)
+{
+ skip_env *env = (skip_env*)x;
+ int i;
+ int n_preds = get_Block_n_cfgpreds(block);
+
+ for (i = 0; i < n_preds; ++i) {
+ ir_node *jmp, *jmp_block;
+ int n_jpreds = 0;
+
+ jmp = get_Block_cfgpred(block, i);
+ if (!is_Jmp(jmp))
+ continue;
+ jmp_block = get_nodes_block(jmp);
+ if (jmp_block == block)
+ continue; /* this infinite loop cannot be optimized any further */
+ if (is_unknown_jump_target(&env->block_infos, jmp_block))
+ continue; /* unknown jump target must not be optimized */
+ if (has_phis(&env->block_infos,jmp_block))
+ continue; /* this block contains Phis and is not skipped */
+ if (Block_block_visited(jmp_block)) {
+ continue;
+ /* otherwise we could break the walker,
+ * if block was reached via
+ * KeepAlive edge -> jmp_block -> A ---> block,
+ * because the walker cannot handle Id nodes.
+ *
+ * A B
+ * \ /
+ * jmp_block
+ * / \
+ * block End
+ */
+ }
+
+ /* jmp_block is an empty block and can be optimized! */
+
+ n_jpreds = get_Block_n_cfgpreds(jmp_block);
+ /**
+ * If the jmp block has only one predecessor this is straightforward.
+ * However, if there are more predecessors, we only handle this,
+ * if block has no Phis.
+ */
+ if (n_jpreds == 1) {
+ ir_node *pred = get_Block_cfgpred(jmp_block, 0);
+ ir_node *pred_block = get_nodes_block(pred);
+ if (has_operations(&env->block_infos,jmp_block)) {
+ if (get_irg_start_block(get_irn_irg(pred_block)) == pred_block)
+ continue; /* must not merge operations into start block */
+ if (!is_Jmp(pred))
+ continue; /* must not create partially dead code, especially when it is mode_M */
+ }
+
+ /* skip jmp block by rerouting its predecessor to block
+ *
+ * A A
+ * | |
+ * jmp_block => |
+ * | |
+ * block block
+ */
+ exchange(jmp, pred);
+
+ /* cleanup: jmp_block might have a Keep edge! */
+ exchange(jmp_block, pred_block);
+ env->changed = true;
+ } else if ( !has_phis(&env->block_infos, block) &&
+ !has_operations(&env->block_infos,jmp_block))
+ {
+ /* all predecessors can skip the jmp block, so block gets some new
+ * predecessors
+ *
+ * A B A B
+ * \ / | |
+ * jmp_block C => Bad C | |
+ * \ / \ | | /
+ * block block
+ */
+ ir_node **ins = ALLOCAN(ir_node*, n_preds+n_jpreds);
+ int j;
+ /* first copy the old predecessors, because the outer loop (i)
+ * still walks over them */
+ for (j = 0; j < n_preds; ++j) {
+ ins[j] = get_Block_cfgpred(block, j);
+ }
+ /* now append the new predecessors */
+ for (j = 0; j < n_jpreds; ++j) {
+ ir_node *pred = get_Block_cfgpred(jmp_block, j);
+ ins[n_preds+j] = pred;
}
+ set_irn_in(block, n_preds+n_jpreds, ins);
+ /* convert the jmp_block to Bad */
+ ir_graph *irg = get_irn_irg(block);
+ exchange(jmp_block, new_r_Bad(irg, mode_BB));
+ exchange(jmp, new_r_Bad(irg, mode_X));
+ /* let the outer loop walk over the new predecessors as well */
+ n_preds += n_jpreds;
+ env->changed = true;
+ // TODO What if jmp_block had a KeepAlive edge?
+ } else {
+ /* This would involve Phis ... */
}
}
- return false;
}
-/* 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.
+/*
+ * All cfg optimizations, which do not touch Phi nodes.
*
- * We use the mark flag to mark removable blocks in the first phase.
+ * Note that this might create critical edges.
*/
+static void cfgopt_ignoring_phis(ir_graph *irg)
+{
+ skip_env env;
+
+ env.changed = true;
+ ir_nodehashmap_init(&env.block_infos);
+
+ while (env.changed) {
+ irg_walk_graph(irg, compute_block_info, NULL, &env.block_infos);
+ env.changed = false;
+
+ /* Remove blocks, which only consist of a Jmp */
+ irg_block_walk_graph(irg, remove_empty_blocks, NULL, &env);
+
+ /* Optimize Cond->Jmp, where then- and else-block are the same. */
+ irg_block_walk_graph(irg, NULL, optimize_ifs, &env);
+
+ if (env.changed) {
+ confirm_irg_properties(irg, IR_GRAPH_PROPERTIES_NONE);
+ /* clear block info, because it must be recomputed */
+ irg_block_walk_graph(irg, clear_block_info, NULL, &env.block_infos);
+ /* Removing blocks and Conds might enable more optimizations */
+ continue;
+ } else {
+ confirm_irg_properties(irg, IR_GRAPH_PROPERTIES_ALL);
+ break;
+ }
+ }
+
+ ir_nodehashmap_destroy(&env.block_infos);
+}
+
+/* Optimizations of the control flow that also require changes of Phi nodes. */
void optimize_cf(ir_graph *irg)
{
int i, j, n;
ir_node *new_end;
merge_env env;
- assert(get_irg_phase_state(irg) != phase_building);
+ env.changed = false;
+ env.phis_moved = false;
/* if the graph is not pinned, we cannot determine empty blocks */
assert(get_irg_pinned(irg) != op_pin_state_floats &&
"Control flow optimization need a pinned graph");
- /* FIXME: control flow opt destroys block edges. So edges are deactivated
- * here. Fix the edges! */
- edges_deactivate(irg);
-
- /* we use the mark flag to mark removable blocks */
- ir_reserve_resources(irg, IR_RESOURCE_BLOCK_MARK | IR_RESOURCE_IRN_LINK);
-restart:
- env.changed = false;
- env.phis_moved = false;
-
- assure_doms(irg);
+ assure_irg_properties(irg, IR_GRAPH_PROPERTY_NO_UNREACHABLE_CODE);
- env.switch_conds = NEW_ARR_F(ir_node*, 0);
- irg_walk(end, clear_link, collect_nodes, &env);
+ /* First the "simple" optimizations, which do not touch Phis */
+ cfgopt_ignoring_phis(irg);
- /* handle all collected switch-Conds */
- n = ARR_LEN(env.switch_conds);
- for (i = 0; i < n; ++i) {
- ir_node *cond = env.switch_conds[i];
- env.changed |= handle_switch_cond(cond);
- }
- DEL_ARR_F(env.switch_conds);
-
- if (env.changed) {
- /* Handle graph state if was changed. */
- set_irg_outs_inconsistent(irg);
- set_irg_doms_inconsistent(irg);
- set_irg_extblk_inconsistent(irg);
- set_irg_loopinfo_inconsistent(irg);
- set_irg_entity_usage_state(irg, ir_entity_usage_not_computed);
-
- /* The Cond optimization might generate unreachable code, so restart if
- it happens. */
- goto restart;
- }
-
- /* Optimize the standard code. */
- assure_doms(irg);
- irg_block_walk_graph(irg, optimize_blocks, remove_simple_blocks, &env);
+ /* we use the mark flag to mark removable blocks */
+ ir_reserve_resources(irg, IR_RESOURCE_BLOCK_MARK | IR_RESOURCE_IRN_LINK
+ | IR_RESOURCE_PHI_LIST);
+
+ /*
+ * This 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.
+ */
+ irg_walk(end, clear_link_and_mark_blocks_removable, collect_nodes, NULL);
+
+ /* assert due to collect_nodes:
+ * 1. removable blocks are now marked as such
+ * 2. phi lists are up to date
+ */
+
+ /* Optimize the standard code.
+ * It walks only over block nodes and adapts these and the Phi nodes in
+ * these blocks, which it finds in a linked list computed before.
+ */
+ assure_irg_properties(irg, IR_GRAPH_PROPERTY_CONSISTENT_DOMINANCE);
+ irg_block_walk_graph(irg, optimize_blocks, merge_blocks, &env);
new_end = optimize_in_place(end);
if (new_end != end) {
}
remove_End_Bads_and_doublets(end);
- ir_free_resources(irg, IR_RESOURCE_BLOCK_MARK | IR_RESOURCE_IRN_LINK);
+ ir_free_resources(irg, IR_RESOURCE_BLOCK_MARK | IR_RESOURCE_IRN_LINK
+ | IR_RESOURCE_PHI_LIST);
if (env.phis_moved) {
/* Bad: when we moved Phi's, we might produce dead Phi nodes
that are kept-alive.
- Some other phases cannot copy with this, so will them.
+ Some other phases cannot copy with this, so kill them.
*/
n = get_End_n_keepalives(end);
if (n > 0) {
NEW_ARR_A(ir_node *, in, n);
- if (env.changed) {
- /* Handle graph state if was changed. */
- set_irg_outs_inconsistent(irg);
- }
assure_irg_outs(irg);
for (i = j = 0; i < n; ++i) {
}
}
- if (env.changed) {
- /* Handle graph state if was changed. */
- set_irg_outs_inconsistent(irg);
- set_irg_doms_inconsistent(irg);
- set_irg_extblk_inconsistent(irg);
- set_irg_loopinfo_inconsistent(irg);
- set_irg_entity_usage_state(irg, ir_entity_usage_not_computed);
- }
-
- /* the verifier 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_verify_bads(irg, BAD_DF | BAD_BLOCK | TUPLE)) {
- dump_ir_graph(irg, "-verify-cf");
- fprintf(stderr, "VERIFY_BAD in optimize_cf()\n");
- }
- }
+ confirm_irg_properties(irg,
+ env.changed ? IR_GRAPH_PROPERTIES_NONE : IR_GRAPH_PROPERTIES_ALL);
}
/* Creates an ir_graph pass for optimize_cf. */
projects / libfirm / blobdiff