#include "irflag_t.h"
#include "firmstat.h"
#include "irpass.h"
+#include "irphase_t.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);
}
+/** check if a block has the removable property set. */
static bool is_Block_removable(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(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);
*/
static void collect_nodes(ir_node *n, void *ctx)
{
- merge_env *env = (merge_env*)ctx;
+ ir_node ***switch_conds = (ir_node***)ctx;
if (is_Phi(n)) {
/* Collect Phi nodes to compact ins along with block's ins. */
set_irn_link(n, get_irn_link(block));
set_irn_link(block, n);
} else if (is_Block(n)) {
- if (has_Block_entity(n))
+ if (has_Block_entity(n)) {
+ /* block with a jump label attached cannot be removed. */
set_Block_removable(n, false);
+ }
return;
} else if (!is_Jmp(n)) { /* Check for non-empty block. */
ir_node *block = get_nodes_block(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);
- }
+ } else if (is_Cond(n) && is_switch_Cond(n)) {
+ /* found a switch-Cond, collect */
+ ARR_APP1(ir_node*, *switch_conds, n);
}
}
}
-/** Returns true if pred is predecessor of block. */
+/** Returns true if pred is predecessor of block b. */
static bool is_pred_of(ir_node *pred, ir_node *b)
{
int i;
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;
pred = get_Block_cfgpred_block(b, i);
if (is_Bad(pred)) {
- in[q_preds++] = pred;
+ 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;
} 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;
/* 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
+ * So the only case left to handle here is 1 defaultProj + 1 case
* (this one case should be the one taken) */
if (get_irn_link(proj2) == NULL) {
ir_tarval *tv = value_of(sel);
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.
+/**
+ * Optimize boolean Conds, where true and false jump to the same block into a Jmp
+ * Block must contain no Phi nodes.
*
- * We use the mark flag to mark removable blocks in the first phase.
+ * Cond
+ * / \
+ * projA projB => Jmp Bad
+ * \ / \ /
+ * block block
+ */
+static bool optimize_pred_cond(ir_node *block, int i, int j)
+{
+ 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;
+}
+
+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_phase_flag(ir_phase *block_info, ir_node *block, int flag)
+{
+ return PTR_TO_INT(phase_get_irn_data(block_info, block)) & flag;
+}
+
+static void set_phase_flag(ir_phase *block_info, ir_node *block,
+ block_flags_t flag)
+{
+ int data = PTR_TO_INT(phase_get_irn_data(block_info, block));
+ data |= flag;
+ phase_set_irn_data(block_info, block, INT_TO_PTR(data));
+}
+
+static bool has_operations(ir_phase *block_info, ir_node *block)
+{
+ return get_phase_flag(block_info, block, BF_HAS_OPERATIONS);
+}
+
+static void set_has_operations(ir_phase *block_info, ir_node *block)
+{
+ set_phase_flag(block_info, block, BF_HAS_OPERATIONS);
+}
+
+static bool has_phis(ir_phase *block_info, ir_node *block)
+{
+ return get_phase_flag(block_info, block, BF_HAS_PHIS);
+}
+
+static void set_has_phis(ir_phase *block_info, ir_node *block)
+{
+ set_phase_flag(block_info, block, BF_HAS_PHIS);
+}
+
+static bool is_unknown_jump_target(ir_phase *block_info, ir_node *block)
+{
+ return get_phase_flag(block_info, block, BF_IS_UNKNOWN_JUMP_TARGET);
+}
+
+static void set_is_unknown_jump_target(ir_phase *block_info, ir_node *block)
+{
+ set_phase_flag(block_info, block, BF_IS_UNKNOWN_JUMP_TARGET);
+}
+
+/**
+ * Walker: fill block info information.
*/
+static void compute_block_info(ir_node *n, void *x)
+{
+ ir_phase *block_info = (ir_phase *)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(block_info, n);
+ }
+ }
+ } else if (is_Phi(n)) {
+ ir_node *block = get_nodes_block(n);
+ set_has_phis(block_info, block);
+ } else if (is_Jmp(n) || is_Cond(n) || is_Cmp(n) || is_Proj(n)) {
+ /* ignore */
+ } else {
+ ir_node *block = get_nodes_block(n);
+ set_has_operations(block_info, block);
+ }
+}
+
+typedef struct skip_env {
+ bool changed;
+ ir_phase *phase;
+} skip_env;
+
+/**
+ * Post-Block-walker: Optimize useless if's (boolean Cond nodes
+ * with same true/false target)
+ * away.
+ */
+static void optimize_ifs(ir_node *block, void *x)
+{
+ skip_env *env = (skip_env*)x;
+ int i, j;
+ int n_preds = get_Block_n_cfgpreds(block);
+
+ if (has_phis(env->phase, 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);
+ }
+ }
+}
+
+/**
+ * Pre-Block walker: remove empty blocks that are
+ * 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, *pred, *pred_block;
+
+ jmp = get_Block_cfgpred(block, i);
+ if (!is_Jmp(jmp))
+ continue;
+ jmp_block = get_nodes_block(jmp);
+ if (is_unknown_jump_target(env->phase, jmp_block))
+ continue;
+ if (has_operations(env->phase,jmp_block))
+ continue;
+ /* jmp_block is an empty block! */
+
+ if (get_Block_n_cfgpreds(jmp_block) != 1)
+ continue;
+ pred = get_Block_cfgpred(jmp_block, 0);
+ exchange(jmp, pred);
+ env->changed = true;
+
+ /* cleanup: jmp_block might have a Keep edge! */
+ pred_block = get_nodes_block(pred);
+ exchange(jmp_block, pred_block);
+ }
+}
+
+/*
+ * Some cfg optimizations, which do not touch Phi nodes
+ */
+static void cfgopt_ignoring_phis(ir_graph *irg)
+{
+ ir_phase *block_info = new_phase(irg, NULL);
+ skip_env env = { false, block_info };
+
+ irg_walk_graph(irg, compute_block_info, NULL, block_info);
+
+ for (;;) {
+ env.changed = false;
+
+ /* optimize useless ifs: will not touch empty blocks */
+ irg_block_walk_graph(irg, NULL, optimize_ifs, &env);
+
+ /* Remove empty blocks */
+ irg_block_walk_graph(irg, remove_empty_blocks, NULL, &env);
+ if (env.changed) {
+ set_irg_doms_inconsistent(irg);
+ /* Removing blocks might enable more useless-if optimizations */
+ continue;
+ } else {
+ break;
+ }
+ }
+
+ phase_free(block_info);
+}
+
+/* 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;
+ env.changed = false;
+ env.phis_moved = false;
+
assert(get_irg_phase_state(irg) != phase_building);
/* if the graph is not pinned, we cannot determine empty blocks */
* here. Fix the edges! */
edges_deactivate(irg);
+ cfgopt_ignoring_phis(irg);
+
/* we use the mark flag to mark removable blocks */
ir_reserve_resources(irg, IR_RESOURCE_BLOCK_MARK | IR_RESOURCE_IRN_LINK);
- /* The Cond optimization might expose unreachable code, so we loop */
+ /* The switch Cond optimization might expose unreachable code, so we loop */
for (;;) {
int length;
- env.changed = false;
- env.phis_moved = false;
+ ir_node **switch_conds = NULL;
+ bool changed = false;
assure_doms(irg);
- env.switch_conds = NEW_ARR_F(ir_node*, 0);
- irg_walk(end, clear_link, collect_nodes, &env);
+ /*
+ * 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.
+ */
+ switch_conds = NEW_ARR_F(ir_node*, 0);
+ irg_walk(end, clear_link_and_mark_blocks_removable, collect_nodes, &switch_conds);
/* handle all collected switch-Conds */
- length = ARR_LEN(env.switch_conds);
+ length = ARR_LEN(switch_conds);
for (i = 0; i < length; ++i) {
- ir_node *cond = env.switch_conds[i];
- env.changed |= handle_switch_cond(cond);
+ ir_node *cond = switch_conds[i];
+ changed |= handle_switch_cond(cond);
}
- DEL_ARR_F(env.switch_conds);
+ DEL_ARR_F(switch_conds);
- if (!env.changed) break;
+ if (!changed)
+ break;
set_irg_doms_inconsistent(irg);
set_irg_extblk_inconsistent(irg);
* 2. phi lists are up to date
*/
- /* Optimize the standard code. */
+ /* 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_doms(irg);
irg_block_walk_graph(irg, optimize_blocks, NULL, &env);
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) {
projects / libfirm / blobdiff