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Commit 8ea5207a authored by Matthias Braun's avatar Matthias Braun
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cfopt: fix countless bugs introduced when changing unreachable code elimination

parent 385ddac3
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ir/opt/cfopt.c
View file @ 8ea5207a
......@@ -101,6 +101,8 @@ static void collect_nodes(ir_node *n, void *ctx)
set_irn_link(n, get_irn_link(block));
set_irn_link(block, n);
} else if (is_Block(n)) {
if (has_Block_entity(n))
set_Block_removable(n, false);
return;
} else if (!is_Jmp(n)) { /* Check for non-empty block. */
ir_node *block = get_nodes_block(n);
......@@ -134,6 +136,20 @@ static bool is_pred_of(ir_node *pred, ir_node *b)
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.
......@@ -163,48 +179,61 @@ static bool is_pred_of(ir_node *pred, ir_node *b)
**/
static unsigned test_whether_dispensable(ir_node *b, int pos)
{
int i, j, n_preds = 1;
ir_node *pred = get_Block_cfgpred_block(b, 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(pred)) {
/* Seems to be empty. At least we detected this in collect_nodes. */
if (get_irn_link(b) == NULL) {
/* 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.
Handle all pred blocks with preds < pos as if they were already removed. */
for (i = 0; i < pos; i++) {
ir_node *b_pred = get_Block_cfgpred_block(b, i);
if (! is_Bad(b_pred) && is_Block_removable(b_pred)) {
for (j = get_Block_n_cfgpreds(b_pred) - 1; j >= 0; --j) {
ir_node *b_pred_pred = get_Block_cfgpred_block(b_pred, j);
if (is_pred_of(b_pred_pred, pred))
goto non_dispensable;
}
} else {
if (is_pred_of(b_pred, pred))
if (!is_Block_removable(predb))
return 1;
/* can't remove self-loops */
if (predb == b)
goto non_dispensable;
if (is_unknown_jump(pred))
goto non_dispensable;
/* Seems to be empty. At least we detected this in collect_nodes. */
if (get_irn_link(b) != NULL) {
int n_cfgpreds = get_Block_n_cfgpreds(b);
int i;
/* there are Phi nodes */
/* b's pred blocks and pred's pred blocks must be pairwise disjunct.
* Handle all pred blocks with preds < pos as if they were already
* removed. */
for (i = 0; i < pos; i++) {
ir_node *other_pred = get_Block_cfgpred(b, i);
ir_node *other_predb = get_nodes_block(other_pred);
if (is_Bad(other_pred))
continue;
if (is_Block_removable(other_predb)
&& !Block_block_visited(other_predb)) {
int j;
for (j = get_Block_n_cfgpreds(other_predb) - 1; j >= 0; --j) {
ir_node *other_predpred
= get_Block_cfgpred_block(other_predb, j);
if (is_pred_of(other_predpred, predb))
goto non_dispensable;
}
} else if (is_pred_of(other_predb, predb)) {
goto non_dispensable;
}
for (i = pos +1; i < get_Block_n_cfgpreds(b); i++) {
ir_node *b_pred = get_Block_cfgpred_block(b, i);
if (is_pred_of(b_pred, pred))
goto non_dispensable;
}
/* if we get here, the block is dispensable */
n_preds = get_Block_n_cfgpreds(pred);
}
for (i = pos+1; i < n_cfgpreds; i++) {
ir_node *other_predb = get_Block_cfgpred_block(b, i);
if (is_pred_of(other_predb, predb))
goto non_dispensable;
}
}
return n_preds;
/* we will not dispense already visited blocks */
if (Block_block_visited(predb))
return 1;
/* if we get here, the block is dispensable, count useful preds */
return count_non_bad_inputs(predb);
non_dispensable:
set_Block_removable(pred, false);
set_Block_removable(predb, false);
return 1;
}
......@@ -287,18 +316,20 @@ static void optimize_blocks(ir_node *b, void *ctx)
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(get_Block_cfgpred(pred, j))) {
if (get_nodes_block(phi_pred) == pred) {
/* case Phi 2a: */
assert(is_Phi(phi_pred)); /* Block is empty!! */
if (is_Bad(pred_pred))
continue;
in[p_preds++] = get_Phi_pred(phi_pred, j);
} else {
/* case Phi 2b: */
in[p_preds++] = phi_pred;
}
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: */
in[p_preds++] = phi_pred;
}
}
} else {
......@@ -306,7 +337,7 @@ static void optimize_blocks(ir_node *b, void *ctx)
in[p_preds++] = get_Phi_pred(phi, i);
}
}
assert(p_preds <= max_preds);
assert(p_preds == max_preds);
/* Fix the node */
if (p_preds == 1)
......@@ -321,9 +352,9 @@ static void optimize_blocks(ir_node *b, void *ctx)
Moreover, it is only needed if predb is the direct dominator of b,
else there can be no uses of the Phi's in predb ... -*/
for (k = 0, n = get_Block_n_cfgpreds(b); k < n; ++k) {
ir_node *predb = get_nodes_block(get_Block_cfgpred(b, k));
if (is_Bad(predb))
ir_node *pred = get_Block_cfgpred(b, k);
ir_node *predb = get_nodes_block(pred);
if (is_Bad(pred))
continue;
if (is_Block_removable(predb) && !Block_block_visited(predb)) {
......@@ -406,35 +437,38 @@ static void optimize_blocks(ir_node *b, void *ctx)
/*- Fix the block -*/
n_preds = 0;
for (i = 0; i < get_Block_n_cfgpreds(b); i++) {
pred = get_Block_cfgpred_block(b, i);
ir_node *pred = get_Block_cfgpred(b, i);
ir_node *predb = get_nodes_block(pred);
if (is_Bad(pred)) {
/* case 1: Do nothing */
} else if (is_Block_removable(pred) && !Block_block_visited(pred)) {
/* case 1: Do nothing */
if (is_Bad(pred))
continue;
if (is_Block_removable(predb) && !Block_block_visited(predb)) {
/* case 2: It's an empty block and not yet visited. */
assert(get_Block_n_cfgpreds(b) > 1 || has_Block_entity(b));
/* Else it should be optimized by equivalent_node. */
for (j = 0; j < get_Block_n_cfgpreds(pred); j++) {
ir_node *pred_X = 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_X))
in[n_preds++] = pred_X;
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))
continue;
in[n_preds++] = predpred;
}
/* Remove block as it might be kept alive. */
exchange(pred, b/*get_irg_bad(irg)*/);
/* 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)));
} else {
/* case 3: */
in[n_preds++] = get_Block_cfgpred(b, i);
in[n_preds++] = pred;
}
}
assert(n_preds <= max_preds);
assert(n_preds == max_preds);
set_irn_in(b, n_preds, in);
env->changed = true;
assert(get_irn_link(b) == NULL || p_preds == -1 || (n_preds == p_preds && "Wrong Phi Fix"));
/* see if phi-fix was correct */
assert(get_irn_link(b) == NULL || p_preds == -1 || (n_preds == p_preds));
xfree(in);
}
......
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