diff options
Diffstat (limited to 'src/glsl/nir')
| -rw-r--r-- | src/glsl/nir/nir.h | 2 | ||||
| -rw-r--r-- | src/glsl/nir/nir_opt_dead_cf.c | 155 |
2 files changed, 157 insertions, 0 deletions
diff --git a/src/glsl/nir/nir.h b/src/glsl/nir/nir.h index 9703372fcc0..c65d090eac1 100644 --- a/src/glsl/nir/nir.h +++ b/src/glsl/nir/nir.h @@ -1825,6 +1825,8 @@ bool nir_opt_cse(nir_shader *shader); bool nir_opt_dce_impl(nir_function_impl *impl); bool nir_opt_dce(nir_shader *shader); +bool nir_opt_dead_cf(nir_shader *shader); + void nir_opt_gcm(nir_shader *shader); bool nir_opt_peephole_select(nir_shader *shader); diff --git a/src/glsl/nir/nir_opt_dead_cf.c b/src/glsl/nir/nir_opt_dead_cf.c new file mode 100644 index 00000000000..fca842caedd --- /dev/null +++ b/src/glsl/nir/nir_opt_dead_cf.c @@ -0,0 +1,155 @@ +/* + * Copyright © 2014 Connor Abbott + * + * Permission is hereby granted, free of charge, to any person obtaining a + * copy of this software and associated documentation files (the "Software"), + * to deal in the Software without restriction, including without limitation + * the rights to use, copy, modify, merge, publish, distribute, sublicense, + * and/or sell copies of the Software, and to permit persons to whom the + * Software is furnished to do so, subject to the following conditions: + * + * The above copyright notice and this permission notice (including the next + * paragraph) shall be included in all copies or substantial portions of the + * Software. + * + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL + * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING + * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS + * IN THE SOFTWARE. + * + * Authors: + * Connor Abbott ([email protected]) + * + */ + +#include "nir.h" +#include "nir_control_flow.h" + +/* + * This file implements an optimization that deletes statically unreachable + * code. In NIR, one way this can happen if if an if statement has a constant + * condition: + * + * if (true) { + * ... + * } + * + * We delete the if statement and paste the contents of the always-executed + * branch into the surrounding control flow, possibly removing more code if + * the branch had a jump at the end. + */ + +static void +remove_after_cf_node(nir_cf_node *node) +{ + nir_cf_node *end = node; + while (!nir_cf_node_is_last(end)) + end = nir_cf_node_next(end); + + nir_cf_list list; + nir_cf_extract(&list, nir_after_cf_node(node), nir_after_cf_node(end)); + nir_cf_delete(&list); +} + +static void +opt_constant_if(nir_if *if_stmt, bool condition) +{ + void *mem_ctx = ralloc_parent(if_stmt); + + /* First, we need to remove any phi nodes after the if by rewriting uses to + * point to the correct source. + */ + nir_block *after = nir_cf_node_as_block(nir_cf_node_next(&if_stmt->cf_node)); + nir_block *last_block = + nir_cf_node_as_block(condition ? nir_if_last_then_node(if_stmt) + : nir_if_last_else_node(if_stmt)); + + nir_foreach_instr_safe(after, instr) { + if (instr->type != nir_instr_type_phi) + break; + + nir_phi_instr *phi = nir_instr_as_phi(instr); + nir_ssa_def *def = NULL; + nir_foreach_phi_src(phi, phi_src) { + if (phi_src->pred != last_block) + continue; + + assert(phi_src->src.is_ssa); + def = phi_src->src.ssa; + } + + assert(def); + assert(phi->dest.is_ssa); + nir_ssa_def_rewrite_uses(&phi->dest.ssa, nir_src_for_ssa(def), mem_ctx); + nir_instr_remove(instr); + } + + /* The control flow list we're about to paste in may include a jump at the + * end, and in that case we have to delete the rest of the control flow + * list after the if since it's unreachable and the validator will balk if + * we don't. + */ + + if (!exec_list_is_empty(&last_block->instr_list)) { + nir_instr *last_instr = nir_block_last_instr(last_block); + if (last_instr->type == nir_instr_type_jump) + remove_after_cf_node(&if_stmt->cf_node); + } + + /* Finally, actually paste in the then or else branch and delete the if. */ + struct exec_list *cf_list = condition ? &if_stmt->then_list + : &if_stmt->else_list; + + nir_cf_list list; + nir_cf_extract(&list, nir_before_cf_list(cf_list), + nir_after_cf_list(cf_list)); + nir_cf_reinsert(&list, nir_after_cf_node(&if_stmt->cf_node)); + nir_cf_node_remove(&if_stmt->cf_node); +} + +static bool +dead_cf_cb(nir_block *block, void *state) +{ + bool *progress = state; + + nir_if *following_if = nir_block_get_following_if(block); + if (!following_if) + return true; + + nir_const_value *const_value = + nir_src_as_const_value(following_if->condition); + + if (!const_value) + return true; + + opt_constant_if(following_if, const_value->u[0] != 0); + *progress = true; + return true; +} + +static bool +opt_dead_cf_impl(nir_function_impl *impl) +{ + bool progress = false; + nir_foreach_block(impl, dead_cf_cb, &progress); + + if (progress) + nir_metadata_preserve(impl, nir_metadata_none); + + return progress; +} + +bool +nir_opt_dead_cf(nir_shader *shader) +{ + bool progress = false; + + nir_foreach_overload(shader, overload) + if (overload->impl) + progress |= opt_dead_cf_impl(overload->impl); + + return progress; +} |