Mesa (master): nir: unroll some loops with a variable limit
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gitlab-mirror at kemper.freedesktop.org
Tue Mar 12 01:37:13 UTC 2019
Module: Mesa
Branch: master
Commit: 7571de8eaa50bca1e0162ce212c47a6f9e927120
URL: http://cgit.freedesktop.org/mesa/mesa/commit/?id=7571de8eaa50bca1e0162ce212c47a6f9e927120
Author: Timothy Arceri <tarceri at itsqueeze.com>
Date: Tue Nov 20 15:23:45 2018 +1100
nir: unroll some loops with a variable limit
For some loops can have a single terminator but the exact trip
count is still unknown. For example:
for (int i = 0; i < imin(x, 4); i++)
...
Shader-db results radeonsi (all affected are from Tropico 5):
Totals from affected shaders:
SGPRS: 144 -> 152 (5.56 %)
VGPRS: 124 -> 108 (-12.90 %)
Spilled SGPRs: 0 -> 0 (0.00 %)
Spilled VGPRs: 0 -> 0 (0.00 %)
Private memory VGPRs: 0 -> 0 (0.00 %)
Scratch size: 0 -> 0 (0.00 %) dwords per thread
Code Size: 5180 -> 6640 (28.19 %) bytes
LDS: 0 -> 0 (0.00 %) blocks
Max Waves: 17 -> 21 (23.53 %)
Wait states: 0 -> 0 (0.00 %)
Shader-db results i965 (SKL):
total loops in shared programs: 3808 -> 3802 (-0.16%)
loops in affected programs: 6 -> 0
helped: 6
HURT: 0
vkpipeline-db results RADV (Unrolls some Skyrim VR shaders):
Totals from affected shaders:
SGPRS: 304 -> 304 (0.00 %)
VGPRS: 296 -> 292 (-1.35 %)
Spilled SGPRs: 0 -> 0 (0.00 %)
Spilled VGPRs: 0 -> 0 (0.00 %)
Private memory VGPRs: 0 -> 0 (0.00 %)
Scratch size: 0 -> 0 (0.00 %) dwords per thread
Code Size: 15756 -> 25884 (64.28 %) bytes
LDS: 0 -> 0 (0.00 %) blocks
Max Waves: 29 -> 29 (0.00 %)
Wait states: 0 -> 0 (0.00 %)
v2: fix bug where last iteration would get optimised away by
mistake.
Reviewed-by: Ian Romanick <ian.d.romanick at intel.com>
---
src/compiler/nir/nir_opt_loop_unroll.c | 55 ++++++++++++++++++++++++++++++++++
1 file changed, 55 insertions(+)
diff --git a/src/compiler/nir/nir_opt_loop_unroll.c b/src/compiler/nir/nir_opt_loop_unroll.c
index a5a5ca3deee..9ab0a924c82 100644
--- a/src/compiler/nir/nir_opt_loop_unroll.c
+++ b/src/compiler/nir/nir_opt_loop_unroll.c
@@ -456,6 +456,55 @@ complex_unroll(nir_loop *loop, nir_loop_terminator *unlimit_term,
_mesa_hash_table_destroy(remap_table, NULL);
}
+/**
+ * Unroll loops where we only have a single terminator but the exact trip
+ * count is unknown. For example:
+ *
+ * for (int i = 0; i < imin(x, 4); i++)
+ * ...
+ */
+static void
+complex_unroll_single_terminator(nir_loop *loop)
+{
+ assert(list_length(&loop->info->loop_terminator_list) == 1);
+ assert(loop->info->limiting_terminator);
+ assert(nir_is_trivial_loop_if(loop->info->limiting_terminator->nif,
+ loop->info->limiting_terminator->break_block));
+
+ nir_loop_terminator *terminator = loop->info->limiting_terminator;
+
+ loop_prepare_for_unroll(loop);
+
+ /* Pluck out the loop header */
+ nir_cf_list lp_header;
+ nir_cf_extract(&lp_header, nir_before_block(nir_loop_first_block(loop)),
+ nir_before_cf_node(&terminator->nif->cf_node));
+
+ struct hash_table *remap_table =
+ _mesa_hash_table_create(NULL, _mesa_hash_pointer,
+ _mesa_key_pointer_equal);
+
+ /* We need to clone the loop one extra time in order to clone the lcssa
+ * vars for the last iteration (they are inside the following ifs break
+ * branch). We leave other passes to clean up this redundant if.
+ */
+ unsigned num_times_to_clone = loop->info->max_trip_count + 1;
+
+ nir_cf_list lp_body;
+ nir_cf_node *unroll_loc =
+ complex_unroll_loop_body(loop, terminator, &lp_header, &lp_body,
+ remap_table, num_times_to_clone);
+
+ /* Delete the original loop header and body */
+ nir_cf_delete(&lp_header);
+ nir_cf_delete(&lp_body);
+
+ /* The original loop has been replaced so remove it. */
+ nir_cf_node_remove(&loop->cf_node);
+
+ _mesa_hash_table_destroy(remap_table, NULL);
+}
+
/* Unrolls the classic wrapper loops e.g
*
* do {
@@ -853,6 +902,12 @@ process_loops(nir_shader *sh, nir_cf_node *cf_node, bool *has_nested_loop_out)
}
progress = true;
}
+
+ if (num_lt == 1) {
+ assert(loop->info->limiting_terminator->exact_trip_count_unknown);
+ complex_unroll_single_terminator(loop);
+ progress = true;
+ }
}
}
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