Mesa (master): nir/repair_ssa: Repair dominance for unreachable blocks
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Fri Sep 6 23:39:23 UTC 2019
Module: Mesa
Branch: master
Commit: a3268599f3c9bb1d92571e15df95750a06114811
URL: http://cgit.freedesktop.org/mesa/mesa/commit/?id=a3268599f3c9bb1d92571e15df95750a06114811
Author: Jason Ekstrand <jason at jlekstrand.net>
Date: Mon Sep 2 12:54:31 2019 -0500
nir/repair_ssa: Repair dominance for unreachable blocks
NIR currently assumes that unreachable blocks are trivially dominated by
everything. However, when considering well-formed SSA, there is no path
from any block to an unreachable block. Therefore, we can break any
use-def chains where the use is in an unreachable block. This removes
any dependencies on code created by uses in unreachable blocks and lets
DCE do a better job of cleaning it up.
Cc: mesa-stable at lists.freedesktop.org
Reviewed-by: Caio Marcelo de Oliveira Filho <caio.oliveira at intel.com>
---
src/compiler/nir/nir_repair_ssa.c | 12 ++++++++----
1 file changed, 8 insertions(+), 4 deletions(-)
diff --git a/src/compiler/nir/nir_repair_ssa.c b/src/compiler/nir/nir_repair_ssa.c
index f182818374d..b6ec1038843 100644
--- a/src/compiler/nir/nir_repair_ssa.c
+++ b/src/compiler/nir/nir_repair_ssa.c
@@ -71,7 +71,8 @@ repair_ssa_def(nir_ssa_def *def, void *void_state)
bool is_valid = true;
nir_foreach_use(src, def) {
- if (!nir_block_dominates(def->parent_instr->block, get_src_block(src))) {
+ if (nir_block_is_unreachable(get_src_block(src)) ||
+ !nir_block_dominates(def->parent_instr->block, get_src_block(src))) {
is_valid = false;
break;
}
@@ -80,7 +81,8 @@ repair_ssa_def(nir_ssa_def *def, void *void_state)
nir_foreach_if_use(src, def) {
nir_block *block_before_if =
nir_cf_node_as_block(nir_cf_node_prev(&src->parent_if->cf_node));
- if (!nir_block_dominates(def->parent_instr->block, block_before_if)) {
+ if (nir_block_is_unreachable(block_before_if) ||
+ !nir_block_dominates(def->parent_instr->block, block_before_if)) {
is_valid = false;
break;
}
@@ -101,7 +103,8 @@ repair_ssa_def(nir_ssa_def *def, void *void_state)
nir_foreach_use_safe(src, def) {
nir_block *src_block = get_src_block(src);
- if (!nir_block_dominates(def->parent_instr->block, src_block)) {
+ if (nir_block_is_unreachable(src_block) ||
+ !nir_block_dominates(def->parent_instr->block, src_block)) {
nir_instr_rewrite_src(src->parent_instr, src, nir_src_for_ssa(
nir_phi_builder_value_get_block_def(val, src_block)));
}
@@ -110,7 +113,8 @@ repair_ssa_def(nir_ssa_def *def, void *void_state)
nir_foreach_if_use_safe(src, def) {
nir_block *block_before_if =
nir_cf_node_as_block(nir_cf_node_prev(&src->parent_if->cf_node));
- if (!nir_block_dominates(def->parent_instr->block, block_before_if)) {
+ if (nir_block_is_unreachable(block_before_if) ||
+ !nir_block_dominates(def->parent_instr->block, block_before_if)) {
nir_if_rewrite_condition(src->parent_if, nir_src_for_ssa(
nir_phi_builder_value_get_block_def(val, block_before_if)));
}
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