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Do simple unreachable block analysis and dead block removal.

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This commit is contained in:
Bill Currie 2011-01-28 11:44:19 +09:00
parent 90a2738459
commit 9159daf99d
1 changed files with 69 additions and 0 deletions
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69
tools/qfcc/source/statements.c
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@ -776,12 +776,81 @@ statement_slist (sblock_t *sblock, expr_t *e)
return sblock;
}
static void
remove_label_from_dest (ex_label_t *label)
{
sblock_t *sblock;
ex_label_t **l;
if (!label)
return;
sblock = label->dest;
for (l = &sblock->labels; *l; l = &(*l)->next) {
if (*l == label) {
*l = label->next;
label->next = 0;
break;
}
}
}
static void
remove_dead_blocks (sblock_t *blocks)
{
sblock_t *sblock;
int did_something;
if (!blocks)
return;
do {
did_something = 0;
blocks->reachable = 1;
for (sblock = blocks; sblock->next; sblock = sblock->next) {
sblock_t *sb = sblock->next;
statement_t *s;
if (sb->labels) {
sb->reachable = 1;
continue;
}
s = (statement_t *) sblock->tail;
if (strcmp (s->opcode, "<GOTO>")
&& strncmp (s->opcode, "<RETURN", 7)) {
sb->reachable = 1;
continue;
}
sb->reachable = 0;
}
for (sblock = blocks; sblock; sblock = sblock->next) {
while (sblock->next && !sblock->next->reachable) {
sblock_t *sb = sblock->next;
statement_t *s;
ex_label_t *label = 0;
notice (0, "removing dead block %p", sb);
sblock->next = sb->next;
s = (statement_t *) sblock->tail;
if (!strcmp (s->opcode, "<GOTO>"))
label = s->opa->o.label;
else if (!strncmp (s->opcode, "<IF", 3))
label = s->opb->o.label;
remove_label_from_dest (label);
did_something = 1;
}
}
} while (did_something);
}
sblock_t *
make_statements (expr_t *e)
{
sblock_t *sblock = new_sblock ();
// print_expr (e);
statement_slist (sblock, e);
// print_flow (sblock);
remove_dead_blocks (sblock);
// print_flow (sblock);
return sblock;
}