/*
** Returns `block` on success or NULL on failure
**
** If the given block is used, returns NULL and does nothing.
*/
t_block *egc_defrag_block(t_heap *heap, t_block *block, int clr_left)
{
t_block *last_free_block;
last_free_block = egc_get_last_free_block(heap, block);
if (!last_free_block || block == last_free_block)
return (NULL);
join_blocks(block, last_free_block, clr_left);
LOG("egc_defrag_block()");
LOG_POINTER(block);
LOG("");
return (block);
}
static void generate_control(code_block *parent, control_statement *control) {
loop_statement *target = control->target;
if (target->type == S_DO_WHILE) {
block_node **root = control->type == S_BREAK
? &target->break_node
: &target->continue_node;
block_node *node = xmalloc(sizeof(*node));
node->block = parent;
node->next = *root;
*root = node;
} else {
join_blocks(parent, control->type == S_BREAK
? target->post_block
: target->condition_block);
}
}
static code_block *generate_do_while(code_block *parent, loop_statement *loop) {
size_t body_block = parent->system->block_count;
code_block *body = fork_block(parent), *context = body;
if (loop->body) {
struct generate_loop_trigger_data data = {
.loop = loop,
.done = false,
.prev_block = body,
.context_block = &context
};
body = generate_block(body, loop->body, loop_trigger, &data);
}
// if the body ends, it implicitly continues
if (body) {
block_node *node = xmalloc(sizeof(*node));
node->block = body;
node->next = loop->continue_node;
loop->continue_node = node;
}
// if we ever continue the loop, we'll want to include the available variables
// these variables:
// - need to be in the outermost scope in the loop
// - need to be available from all continue statements (including the final
// implicit continue)
if (loop->continue_node) {
code_block *condition = tangle_blocks(context, loop->continue_node);
condition = generate_expression(condition, loop->condition);
code_block *body_replay, *post;
weave_blocks(parent, loop->break_node, condition, &body_replay, &post);
join_blocks(body_replay, body_block);
return post;
}
// loop only breaks, never continues (effectively not a loop)
if (loop->break_node) {
fprintf(stderr, "do-while condition not reachable\n");
return tangle_blocks(parent, loop->break_node);
}
fprintf(stderr, "infinite loop, do-while condition not reachable\n");
return NULL;
}
static code_block *generate_while(code_block *parent, loop_statement *loop) {
if (loop->condition->operation.type == O_LITERAL &&
loop->condition->type->type == T_BOOL && loop->condition->value_bool) {
loop->type = S_DO_WHILE;
return generate_do_while(parent, loop);
}
size_t condition_block = parent->system->block_count;
code_block *condition = fork_block(parent);
condition = generate_expression(condition, loop->condition);
code_block *body, *post;
branch_into(condition, &body, &post);
// TODO: this is using undocumented behavior
size_t /*body_block = parent->system->block_count - 2,
*/post_block = parent->system->block_count - 1;
loop->condition_block = condition_block;
loop->post_block = post_block;
if (loop->body) {
body = generate_block(body, loop->body, NULL, NULL);
}
if (body) {
join_blocks(body, condition_block);
}
return post;
}
static code_block *generate_loop(code_block *parent, loop_statement *loop) {
return loop->type == S_DO_WHILE
? generate_do_while(parent, loop)
: generate_while(parent, loop);
}
static code_block *generate_if(code_block *parent, if_statement *branch) {
parent = generate_expression(parent, branch->condition);
code_block *first, *second;
branch_into(parent, &first, &second);
first = branch->first ? generate_block(first, branch->first, NULL, NULL)
: first;
second = branch->second ? generate_block(second, branch->second, NULL, NULL)
: second;
switch (((!first) << 1) | (!second)) {
case 0: // both exist
return merge_blocks(parent, first, second);
case 1: // the first block exists
return rejoin_block(parent, first);
case 2: // the second block exists
return rejoin_block(parent, second);
case 3:
return NULL;
}
fprintf(stderr, "if statement generation logical failure\n");
abort();
}
