On 22/07/18 19:50, Jason Ekstrand wrote:
On Tue, Jul 10, 2018 at 11:49 PM Timothy Arceri <tarc...@itsqueeze.com
<mailto:tarc...@itsqueeze.com>> wrote:
This adds support for unrolling the classic
do {
// ...
} while (false)
that is used to wrap multi-line macros. GLSL IR also wraps switch
statements in a loop like this.
shader-db results IVB:
total loops in shared programs: 2515 -> 2512 (-0.12%)
loops in affected programs: 33 -> 30 (-9.09%)
helped: 3
HURT: 0
---
src/compiler/nir/nir_opt_loop_unroll.c | 63 ++++++++++++++++++++++++++
1 file changed, 63 insertions(+)
diff --git a/src/compiler/nir/nir_opt_loop_unroll.c
b/src/compiler/nir/nir_opt_loop_unroll.c
index 38901470f96..f715fc8ebda 100644
--- a/src/compiler/nir/nir_opt_loop_unroll.c
+++ b/src/compiler/nir/nir_opt_loop_unroll.c
@@ -516,6 +516,69 @@ process_loops(nir_shader *sh, nir_cf_node
*cf_node, bool *has_nested_loop)
*/
if (!progress) {
+ /* Check for the the classic
+ *
+ * do {
+ * // ...
+ * } while (false)
+ *
+ * that is used to wrap multi-line macros. GLSL IR also wraps
switch
+ * statements in a loop like this.
+ */
+ if (loop->info->limiting_terminator == NULL &&
+ list_empty(&loop->info->loop_terminator_list) &&
+ !loop->info->complex_loop) {
+
Mind putting all the code below in a "wrapper_unroll" or
"trivial_unroll" helper?
Sure.
+ nir_block *blk_after_loop =
+
nir_cursor_current_block(nir_after_cf_node(&loop->cf_node));
+
+ /* There may still be some single src phis following the
loop that
+ * have not yet been cleaned up by another pass. Tidy
those up before
+ * unrolling the loop.
+ */
+ nir_foreach_instr_safe(instr, blk_after_loop) {
+ if (instr->type != nir_instr_type_phi)
+ break;
+
+ nir_phi_instr *phi = nir_instr_as_phi(instr);
+ assert(exec_list_length(&phi->srcs) == 1);
+
+ nir_phi_src *phi_src =
+ exec_node_data(nir_phi_src,
+ exec_list_get_head(&phi->srcs),
+ node);
+
+ nir_ssa_def_rewrite_uses(&phi->dest.ssa, phi_src->src);
+ nir_instr_remove(instr);
+
+ progress = true;
+ }
+
+ nir_block *last_loop_blk = nir_loop_last_block(loop);
+ if (nir_block_ends_in_break(last_loop_blk)) {
This confuses me. Above, you assert that all phis have exactly one
source and here you have an if (nir_block_ends_in_break(last_block));
which one is it? Either our loop terminator check above guarantees that
we're in the "do { } while (true)" case where we can assume a single
exit at the end of the loop or it doesn't. Which one is it?
Yeah I think this logic slipped in too early and belongs in the
following patch only.
+
+ /* Remove break at end of the loop */
+ nir_instr *break_instr =
nir_block_last_instr(last_loop_blk);
+ nir_instr_remove(break_instr);
+
+ /* Pluck out the loop body. */
+ nir_cf_list loop_body;
+ nir_cf_extract(&loop_body,
+
nir_before_block(nir_loop_first_block(loop)),
+ nir_after_block(nir_loop_last_block(loop)));
+
+ /* Reinsert loop body after the loop */
+ nir_cf_reinsert(&loop_body,
nir_after_cf_node(&loop->cf_node));
+
+ /* The loop has been unrolled so remove it. */
+ nir_cf_node_remove(&loop->cf_node);
+
+ progress = true;
+ }
+
+ goto exit;
+ }
+
if (*has_nested_loop || loop->info->limiting_terminator == NULL)
goto exit;
--
2.17.1
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