* The continue should then be removed by nir_opt_trivial_continues() and the
* loop can potentially be unrolled.
*
- * Note: do_work_2() is only ever blocks and nested loops. We could also nest
- * other if-statments in the branch which would allow further continues to
- * be removed. However in practice this can result in increased register
- * pressure.
+ * Note: Unless the function param aggressive_last_continue==true do_work_2()
+ * is only ever blocks and nested loops. We avoid nesting other if-statments
+ * in the branch as this can result in increased register pressure, and in
+ * the i965 driver it causes a large amount of spilling in shader-db.
+ * For RADV however nesting these if-statements allows further continues to be
+ * remove and provides a significant FPS boost in Doom, which is why we have
+ * opted for this special bool to enable more aggresive optimisations.
+ * TODO: The GCM pass solves most of the spilling regressions in i965, if it
+ * is ever enabled we should consider removing the aggressive_last_continue
+ * param.
*/
static bool
-opt_if_loop_last_continue(nir_loop *loop)
+opt_if_loop_last_continue(nir_loop *loop, bool aggressive_last_continue)
{
- /* Get the last if-stament in the loop */
+ nir_if *nif;
+ bool then_ends_in_continue;
+ bool else_ends_in_continue;
+
+ /* Scan the control flow of the loop from the last to the first node
+ * looking for an if-statement we can optimise.
+ */
nir_block *last_block = nir_loop_last_block(loop);
nir_cf_node *if_node = nir_cf_node_prev(&last_block->cf_node);
while (if_node) {
- if (if_node->type == nir_cf_node_if)
- break;
+ if (if_node->type == nir_cf_node_if) {
+ nif = nir_cf_node_as_if(if_node);
+ nir_block *then_block = nir_if_last_then_block(nif);
+ nir_block *else_block = nir_if_last_else_block(nif);
- if_node = nir_cf_node_prev(if_node);
- }
+ then_ends_in_continue = nir_block_ends_in_continue(then_block);
+ else_ends_in_continue = nir_block_ends_in_continue(else_block);
- if (!if_node || if_node->type != nir_cf_node_if)
- return false;
-
- nir_if *nif = nir_cf_node_as_if(if_node);
- nir_block *then_block = nir_if_last_then_block(nif);
- nir_block *else_block = nir_if_last_else_block(nif);
+ /* If both branches end in a jump do nothing, this should be handled
+ * by nir_opt_dead_cf().
+ */
+ if ((then_ends_in_continue || nir_block_ends_in_break(then_block)) &&
+ (else_ends_in_continue || nir_block_ends_in_break(else_block)))
+ return false;
- bool then_ends_in_continue = nir_block_ends_in_continue(then_block);
- bool else_ends_in_continue = nir_block_ends_in_continue(else_block);
+ /* If continue found stop scanning and attempt optimisation, or
+ */
+ if (then_ends_in_continue || else_ends_in_continue ||
+ !aggressive_last_continue)
+ break;
+ }
- /* If both branches end in a continue do nothing, this should be handled
- * by nir_opt_dead_cf().
- */
- if ((then_ends_in_continue || nir_block_ends_in_break(then_block)) &&
- (else_ends_in_continue || nir_block_ends_in_break(else_block)))
- return false;
+ if_node = nir_cf_node_prev(if_node);
+ }
+ /* If we didn't find an if to optimise return */
if (!then_ends_in_continue && !else_ends_in_continue)
return false;
- /* if the block after the if/else is empty we bail, otherwise we might end
- * up looping forever
- */
+ /* If there is nothing after the if-statement we bail */
if (&nif->cf_node == nir_cf_node_prev(&last_block->cf_node) &&
exec_list_is_empty(&last_block->instr_list))
return false;
}
static bool
-opt_if_cf_list(nir_builder *b, struct exec_list *cf_list)
+opt_if_cf_list(nir_builder *b, struct exec_list *cf_list,
+ bool aggressive_last_continue)
{
bool progress = false;
foreach_list_typed(nir_cf_node, cf_node, node, cf_list) {
case nir_cf_node_if: {
nir_if *nif = nir_cf_node_as_if(cf_node);
- progress |= opt_if_cf_list(b, &nif->then_list);
- progress |= opt_if_cf_list(b, &nif->else_list);
+ progress |= opt_if_cf_list(b, &nif->then_list,
+ aggressive_last_continue);
+ progress |= opt_if_cf_list(b, &nif->else_list,
+ aggressive_last_continue);
progress |= opt_if_loop_terminator(nif);
progress |= opt_if_merge(nif);
progress |= opt_if_simplification(b, nif);
case nir_cf_node_loop: {
nir_loop *loop = nir_cf_node_as_loop(cf_node);
- progress |= opt_if_cf_list(b, &loop->body);
+ progress |= opt_if_cf_list(b, &loop->body,
+ aggressive_last_continue);
progress |= opt_simplify_bcsel_of_phi(b, loop);
progress |= opt_peel_loop_initial_if(loop);
- progress |= opt_if_loop_last_continue(loop);
+ progress |= opt_if_loop_last_continue(loop,
+ aggressive_last_continue);
break;
}
}
bool
-nir_opt_if(nir_shader *shader)
+nir_opt_if(nir_shader *shader, bool aggressive_last_continue)
{
bool progress = false;
nir_metadata_preserve(function->impl, nir_metadata_block_index |
nir_metadata_dominance);
- if (opt_if_cf_list(&b, &function->impl->body)) {
+ if (opt_if_cf_list(&b, &function->impl->body,
+ aggressive_last_continue)) {
nir_metadata_preserve(function->impl, nir_metadata_none);
/* If that made progress, we're no longer really in SSA form. We
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