diff options
| -rw-r--r-- | src/compiler/nir/nir_opt_dead_cf.c | 60 |
1 files changed, 39 insertions, 21 deletions
diff --git a/src/compiler/nir/nir_opt_dead_cf.c b/src/compiler/nir/nir_opt_dead_cf.c index 2c61ed521ca..e796e6e85e3 100644 --- a/src/compiler/nir/nir_opt_dead_cf.c +++ b/src/compiler/nir/nir_opt_dead_cf.c @@ -133,11 +133,34 @@ opt_constant_if(nir_if *if_stmt, bool condition) } static bool -def_not_live_out(nir_ssa_def *def, void *state) +def_only_used_in_cf_node(nir_ssa_def *def, void *_node) { - nir_block *after = state; + nir_cf_node *node = _node; + assert(node->type == nir_cf_node_loop || node->type == nir_cf_node_if); + + nir_block *before = nir_cf_node_as_block(nir_cf_node_prev(node)); + nir_block *after = nir_cf_node_as_block(nir_cf_node_next(node)); + + nir_foreach_use(use, def) { + /* Because NIR is structured, we can easily determine whether or not a + * value escapes a CF node by looking at the block indices of its uses + * to see if they lie outside the bounds of the CF node. + * + * Note: Normally, the uses of a phi instruction are considered to be + * used in the block that is the predecessor of the phi corresponding to + * that use. If we were computing liveness or something similar, that + * would mean a special case here for phis. However, we're trying here + * to determine if the SSA def ever escapes the loop. If it's used by a + * phi that lives outside the loop then it doesn't matter if the + * corresponding predecessor is inside the loop or not because the value + * can go through the phi into the outside world and escape the loop. + */ + if (use->parent_instr->block->index <= before->index || + use->parent_instr->block->index >= after->index) + return false; + } - return !BITSET_TEST(after->live_in, def->live_index); + return true; } /* @@ -161,13 +184,18 @@ node_is_dead(nir_cf_node *node) { assert(node->type == nir_cf_node_loop || node->type == nir_cf_node_if); - nir_block *before = nir_cf_node_as_block(nir_cf_node_prev(node)); nir_block *after = nir_cf_node_as_block(nir_cf_node_next(node)); + /* Quick check if there are any phis that follow this CF node. If there + * are, then we automatically know it isn't dead. + */ if (!exec_list_is_empty(&after->instr_list) && nir_block_first_instr(after)->type == nir_instr_type_phi) return false; + nir_function_impl *impl = nir_cf_node_get_function(node); + nir_metadata_require(impl, nir_metadata_block_index); + nir_foreach_block_in_cf_node(block, node) { bool inside_loop = node->type == nir_cf_node_loop; for (nir_cf_node *n = &block->cf_node; @@ -191,24 +219,14 @@ node_is_dead(nir_cf_node *node) (!inside_loop || nir_instr_as_jump(instr)->type == nir_jump_return)) return false; - if (instr->type != nir_instr_type_intrinsic) - continue; - - nir_intrinsic_instr *intrin = nir_instr_as_intrinsic(instr); - if (!(nir_intrinsic_infos[intrin->intrinsic].flags & - NIR_INTRINSIC_CAN_ELIMINATE)) - return false; - } - } - - nir_function_impl *impl = nir_cf_node_get_function(node); - nir_metadata_require(impl, nir_metadata_live_ssa_defs | - nir_metadata_dominance); + if (instr->type == nir_instr_type_intrinsic) { + nir_intrinsic_instr *intrin = nir_instr_as_intrinsic(instr); + if (!(nir_intrinsic_infos[intrin->intrinsic].flags & + NIR_INTRINSIC_CAN_ELIMINATE)) + return false; + } - for (nir_block *cur = after->imm_dom; cur && cur != before; - cur = cur->imm_dom) { - nir_foreach_instr(instr, cur) { - if (!nir_foreach_ssa_def(instr, def_not_live_out, after)) + if (!nir_foreach_ssa_def(instr, def_only_used_in_cf_node, node)) return false; } } |