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Rewrite flow_uninitialized() to use reaching defs.

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Nicely, the use sets from live_variable analysis can be used too, though
there are some problems with the naive implementation. For:

vector foo (float x, float y, float z)
{
	vector v;
	v.x = x;
	v.y = y;
	v.z = z;
	return v;
}

qfcc thinks v is uninitialized, but if "if (x) return nil;" (or any other
basic-block splitter) is put just before the return v; qfcc correctly
detects that v is initialized. The reason is that the inits are in the same
basic block as the return, and thus aren't affecting the reaching
definitions, which are stored per-block.

The naive implementation should be good for a fast-cull before doing a
per-statement check.
This commit is contained in:
Bill Currie 2012-12-10 15:58:51 +09:00
parent c47cb697de
commit aa97979d98
1 changed files with 30 additions and 100 deletions
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130
tools/qfcc/source/flow.c
View file

@ -202,7 +202,7 @@ flowvar_is_param (flowvar_t *var)
return 0;
return 1;
}
#if 0
static int
flowvar_is_initialized (flowvar_t *var)
{
@ -213,7 +213,7 @@ flowvar_is_initialized (flowvar_t *var)
def = var->op->o.def;
return def->initialized;
}
#endif
flowvar_t *
flow_get_var (operand_t *op)
{
@ -603,113 +603,43 @@ flow_live_vars (flowgraph_t *graph)
static void
flow_uninitialized (flowgraph_t *graph)
{
set_t *stuse;
set_t *stdef;
set_t *tmp;
set_t *uninit;
set_t *use;
set_t *def;
set_t *predecessors;
set_iter_t *pred_iter;
set_iter_t *var_iter;
flownode_t *node, *pred;
function_t *func = graph->func;
statement_t *st;
int i;
flownode_t *node;
flowvar_t *var;
set_iter_t *var_i;
set_t *defs;
set_t *uninitialized;
if (!graph->num_nodes)
return;
uninitialized = set_new ();
node = graph->nodes[graph->num_nodes];
set_assign (uninitialized, node->reaching_defs.out);
defs = set_new ();
stuse = set_new ();
stdef = set_new ();
tmp = set_new ();
uninit = set_new ();
predecessors = set_new ();
// in for the inital node contains parameters and global vars
tmp = set_new ();
for (i = 0; i < func->num_vars; i++) {
flowvar_t *var = func->vars[i];
if (flowvar_is_global (var) || flowvar_is_param (var)
|| flowvar_is_initialized (var))
set_add (tmp, i);
}
// first, calculate use and def for each block, and initialize the in and
// out sets.
for (i = 0; i < graph->num_nodes; i++) {
node = graph->nodes[i];
use = set_new ();
def = set_new ();
for (st = node->sblock->statements; st; st = st->next) {
flow_analyze_statement (st, stuse, stdef, 0, 0);
live_set_use (stuse, use, def); // init use uses same rules as live
set_union (def, stdef); // for init, always def a set var
}
node->init_vars.use = use;
node->init_vars.def = def;
node->init_vars.in = set_new ();
node->init_vars.out = set_new ();
}
// flow DOWN the graph in dept-first order
node = graph->nodes[0];
set_assign (node->init_vars.in, tmp);
set_assign (node->init_vars.out, tmp);
set_union (node->init_vars.out, node->init_vars.def);
set_assign (tmp, node->init_vars.use);
set_difference (tmp, node->init_vars.in);
set_union (uninit, tmp);
for (i = 1; i < graph->num_nodes; i++) {
node = graph->nodes[graph->dfo[i]];
set_assign (predecessors, node->predecessors);
// not interested in back edges
for (pred_iter = set_first (predecessors); pred_iter;
pred_iter = set_next (pred_iter)) {
pred = graph->nodes[pred_iter->value];
if (pred->dfn >= node->dfn)
set_remove (predecessors, pred->id);
}
set_empty (tmp);
pred_iter = set_first (predecessors);
if (pred_iter) {
pred = graph->nodes[pred_iter->value];
set_assign (tmp, pred->init_vars.out);
pred_iter = set_next (pred_iter);
}
for ( ; pred_iter; pred_iter = set_next (pred_iter)) {
pred = graph->nodes[pred_iter->value];
set_intersection (tmp, pred->init_vars.out);
}
set_assign (node->init_vars.in, tmp);
set_assign (node->init_vars.out, tmp);
set_union (node->init_vars.out, node->init_vars.def);
set_assign (tmp, node->init_vars.use);
set_difference (tmp, node->init_vars.in);
set_union (uninit, tmp);
}
for (var_iter = set_first (uninit); var_iter;
var_iter = set_next (var_iter)) {
expr_t dummy;
flowvar_t *var = func->vars[var_iter->value];
def_t *def;
for (var_i = set_first (node->live_vars.use); var_i;
var_i = set_next (var_i)) {
var = graph->func->vars[var_i->value];
set_assign (defs, var->define);
set_intersection (defs, node->reaching_defs.in);
if (set_is_intersecting (defs, uninitialized)) {
expr_t dummy;
def_t *def;
if (var->op->op_type == op_temp) {
bug (0, "uninitialized temporary: %s", operand_string (var->op));
} else {
def = flowvar_get_def (var);
dummy.line = def->line;
dummy.file = def->file;
if (type_size (def->type) != 1) {
bug (&dummy, "too hard basket");
} else {
warning (&dummy, "%s may be used uninitialized", def->name);
if (var->op->op_type == op_temp) {
bug (0, "uninitialized temporary: %s",
operand_string (var->op));
} else {
def = flowvar_get_def (var);
dummy.line = def->line;
dummy.file = def->file;
warning (&dummy, "%s may be used uninitialized",
def->name);
}
}
}
}
set_delete (stuse);
set_delete (stdef);
set_delete (tmp);
set_delete (uninit);
set_delete (predecessors);
set_delete (defs);
}
static void