Hi,
On 28.11.2018 5.25, Timothy Arceri wrote:
This adds allows loop analysis to detect inductions varibales that
are incremented in both branches of an if rather than in a main
loop block. For example:
[...]> Unfortunatly GCM could move the addition out of the if for us
(making this patch unrequired) but we still cannot enable the GCM
pass without regressions.
Maybe there should be a TODO comment about removing this code when GCM
is added?
- Eero
This unrolls a loop in Rise of The Tomb Raider.
vkpipeline-db results (VEGA):
Totals from affected shaders:
SGPRS: 88 -> 96 (9.09 %)
VGPRS: 56 -> 52 (-7.14 %)
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: 2168 -> 4560 (110.33 %) bytes
LDS: 0 -> 0 (0.00 %) blocks
Max Waves: 4 -> 4 (0.00 %)
Wait states: 0 -> 0 (0.00 %)
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=32211
---
src/compiler/nir/nir_loop_analyze.c | 36 +++++++++++++++++++++++++++++
1 file changed, 36 insertions(+)
diff --git a/src/compiler/nir/nir_loop_analyze.c
b/src/compiler/nir/nir_loop_analyze.c
index 8903e15105..cf97d6bf06 100644
--- a/src/compiler/nir/nir_loop_analyze.c
+++ b/src/compiler/nir/nir_loop_analyze.c
@@ -245,6 +245,42 @@ compute_induction_information(loop_info_state *state)
if (src_var->in_if_branch || src_var->in_nested_loop)
break;
+ /* Detect inductions varibales that are incremented in both branches
+ * of an unnested if rather than in a loop block.
+ */
+ if (is_var_phi(src_var)) {
+ nir_phi_instr *src_phi =
+ nir_instr_as_phi(src_var->def->parent_instr);
+
+ nir_op alu_op;
+ nir_ssa_def *alu_srcs[2] = {0};
+ nir_foreach_phi_src(src2, src_phi) {
+ nir_loop_variable *src_var2 =
+ get_loop_var(src2->src.ssa, state);
+
+ if (!src_var2->in_if_branch || !is_var_alu(src_var2))
+ break;
+
+ nir_alu_instr *alu =
+ nir_instr_as_alu(src_var2->def->parent_instr);
+ if (nir_op_infos[alu->op].num_inputs != 2)
+ break;
+
+ if (alu->src[0].src.ssa == alu_srcs[0] &&
+ alu->src[1].src.ssa == alu_srcs[1] &&
+ alu->op == alu_op) {
+ /* Both branches perform the same calculation so we can use
+ * one of them to find the induction variable.
+ */
+ src_var = src_var2;
+ } else {
+ alu_srcs[0] = alu->src[0].src.ssa;
+ alu_srcs[1] = alu->src[1].src.ssa;
+ alu_op = alu->op;
+ }
+ }
+ }
+
if (!src_var->in_loop) {
biv->def_outside_loop = src_var;
} else if (is_var_alu(src_var)) {
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