Module: Mesa Branch: main Commit: c20751d61dc237d6786d37a9cf8f4736662d5ee2 URL: http://cgit.freedesktop.org/mesa/mesa/commit/?id=c20751d61dc237d6786d37a9cf8f4736662d5ee2
Author: Daniel Schürmann <[email protected]> Date: Wed Dec 1 17:46:16 2021 +0100 nir: add lowering for Loop Continue Constructs This pass lowers Loop Continue Constructs to the previous solution by inserting it at the beginning of the loop: loop { if (i != 0) { continue construct } loop body } Reviewed-by: Faith Ekstrand <[email protected]> Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/13962> --- src/compiler/nir/meson.build | 1 + src/compiler/nir/nir.h | 1 + src/compiler/nir/nir_lower_continue_constructs.c | 141 +++++++++++++++++++++++ 3 files changed, 143 insertions(+) diff --git a/src/compiler/nir/meson.build b/src/compiler/nir/meson.build index db748c23b0e..1948ba24448 100644 --- a/src/compiler/nir/meson.build +++ b/src/compiler/nir/meson.build @@ -145,6 +145,7 @@ files_libnir = files( 'nir_lower_clip_disable.c', 'nir_lower_clip_halfz.c', 'nir_lower_const_arrays_to_uniforms.c', + 'nir_lower_continue_constructs.c', 'nir_lower_convert_alu_types.c', 'nir_lower_variable_initializers.c', 'nir_lower_discard_if.c', diff --git a/src/compiler/nir/nir.h b/src/compiler/nir/nir.h index 18ede24f8c2..872f5156567 100644 --- a/src/compiler/nir/nir.h +++ b/src/compiler/nir/nir.h @@ -5615,6 +5615,7 @@ bool nir_lower_discard_or_demote(nir_shader *shader, bool nir_lower_memory_model(nir_shader *shader); bool nir_lower_goto_ifs(nir_shader *shader); +bool nir_lower_continue_constructs(nir_shader *shader); bool nir_shader_uses_view_index(nir_shader *shader); bool nir_can_lower_multiview(nir_shader *shader); diff --git a/src/compiler/nir/nir_lower_continue_constructs.c b/src/compiler/nir/nir_lower_continue_constructs.c new file mode 100644 index 00000000000..96114b06a86 --- /dev/null +++ b/src/compiler/nir/nir_lower_continue_constructs.c @@ -0,0 +1,141 @@ +/* + * Copyright © 2021 Valve Corporation + * + * 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. + * + */ + + +#include "nir.h" +#include "nir_builder.h" +#include "nir_control_flow.h" + +static bool +lower_loop_continue_block(nir_builder *b, nir_loop *loop) +{ + if (!nir_loop_has_continue_construct(loop)) + return false; + + nir_block *header = nir_loop_first_block(loop); + nir_block *cont = nir_loop_first_continue_block(loop); + + nir_lower_phis_to_regs_block(header); + nir_lower_phis_to_regs_block(cont); + + /* As control flow has to re-converge before executing the continue + * construct, we insert it at the beginning of the loop with a flag + * to ensure that it doesn't get executed in the first iteration: + * + * loop { + * if (i != 0) { + * continue construct + * } + * loop body + * } + */ + + nir_variable *do_cont = + nir_local_variable_create(b->impl, glsl_bool_type(), "cont"); + + b->cursor = nir_before_cf_node(&loop->cf_node); + nir_store_var(b, do_cont, nir_imm_false(b), 1); + b->cursor = nir_before_block(header); + nir_if *cont_if = nir_push_if(b, nir_load_var(b, do_cont)); + { + nir_cf_list extracted; + nir_cf_list_extract(&extracted, &loop->continue_list); + nir_cf_reinsert(&extracted, nir_before_cf_list(&cont_if->then_list)); + } + nir_pop_if(b, cont_if); + nir_store_var(b, do_cont, nir_imm_true(b), 1); + + nir_loop_remove_continue_construct(loop); + return true; +} + + +static bool +visit_cf_list(nir_builder *b, struct exec_list *list) +{ + bool progress = false; + + foreach_list_typed(nir_cf_node, node, node, list) { + switch (node->type) { + case nir_cf_node_block: + continue; + case nir_cf_node_if: { + nir_if *nif = nir_cf_node_as_if(node); + progress |= visit_cf_list(b, &nif->then_list); + progress |= visit_cf_list(b, &nif->else_list); + break; + } + case nir_cf_node_loop: { + nir_loop *loop = nir_cf_node_as_loop(node); + progress |= visit_cf_list(b, &loop->body); + progress |= visit_cf_list(b, &loop->continue_list); + progress |= lower_loop_continue_block(b, loop); + break; + } + case nir_cf_node_function: + unreachable("Unsupported cf_node type."); + } + } + + return progress; +} + +static bool +lower_continue_constructs_impl(nir_function_impl *impl) +{ + nir_builder b; + nir_builder_init(&b, impl); + bool progress = visit_cf_list(&b, &impl->body); + + if (progress) { + nir_metadata_preserve(impl, nir_metadata_none); + + /* Merge the Phis from Header and Continue Target */ + nir_lower_regs_to_ssa_impl(impl); + + /* Re-inserting the Continue Target at the beginning of the loop + * violates the dominance property if instructions in the continue + * use SSA defs from the loop body. + */ + nir_repair_ssa_impl(impl); + } else { + nir_metadata_preserve(impl, nir_metadata_all); + } + + return progress; +} + +bool +nir_lower_continue_constructs(nir_shader *shader) +{ + bool progress = false; + + nir_foreach_function(function, shader) { + if (function->impl && lower_continue_constructs_impl(function->impl)) + progress = true; + } + + return progress; +} +
