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/*
* Copyright © 2018 Red Hat
* Copyright © 2019 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.
*
* Authors:
* Rob Clark (robdclark@gmail.com>
* Daniel Schürmann (daniel.schuermann@campus.tu-berlin.de)
* Rhys Perry (pendingchaos02@gmail.com)
*
*/
#include "nir.h"
/*
* A simple pass that moves some instructions into the least common
* anscestor of consuming instructions.
*/
bool
nir_can_move_instr(nir_instr *instr, nir_move_options options)
{
if ((options & nir_move_const_undef) && instr->type == nir_instr_type_load_const) {
return true;
}
if (instr->type == nir_instr_type_intrinsic) {
nir_intrinsic_instr *intrin = nir_instr_as_intrinsic(instr);
if ((options & nir_move_load_ubo) && intrin->intrinsic == nir_intrinsic_load_ubo)
return true;
if ((options & nir_move_load_input) &&
(intrin->intrinsic == nir_intrinsic_load_interpolated_input ||
intrin->intrinsic == nir_intrinsic_load_input))
return true;
}
if ((options & nir_move_const_undef) && instr->type == nir_instr_type_ssa_undef) {
return true;
}
if ((options & nir_move_comparisons) && instr->type == nir_instr_type_alu &&
nir_alu_instr_is_comparison(nir_instr_as_alu(instr))) {
return true;
}
return false;
}
static nir_loop *
get_innermost_loop(nir_cf_node *node)
{
for (; node != NULL; node = node->parent) {
if (node->type == nir_cf_node_loop)
return (nir_loop*)node;
}
return NULL;
}
/* return last block not after use_block with def_loop as it's innermost loop */
static nir_block *
adjust_block_for_loops(nir_block *use_block, nir_loop *def_loop)
{
nir_loop *use_loop = NULL;
for (nir_cf_node *node = &use_block->cf_node; node != NULL; node = node->parent) {
if (def_loop && node == &def_loop->cf_node)
break;
if (node->type == nir_cf_node_loop)
use_loop = nir_cf_node_as_loop(node);
}
if (use_loop) {
return nir_block_cf_tree_prev(nir_loop_first_block(use_loop));
} else {
return use_block;
}
}
/* iterate a ssa def's use's and try to find a more optimal block to
* move it to, using the dominance tree. In short, if all of the uses
* are contained in a single block, the load will be moved there,
* otherwise it will be move to the least common ancestor block of all
* the uses
*/
static nir_block *
get_preferred_block(nir_ssa_def *def, bool sink_into_loops)
{
nir_block *lca = NULL;
nir_loop *def_loop = NULL;
if (!sink_into_loops)
def_loop = get_innermost_loop(&def->parent_instr->block->cf_node);
nir_foreach_use(use, def) {
nir_instr *instr = use->parent_instr;
nir_block *use_block = instr->block;
/*
* Kind of an ugly special-case, but phi instructions
* need to appear first in the block, so by definition
* we can't move an instruction into a block where it is
* consumed by a phi instruction. We could conceivably
* move it into a dominator block.
*/
if (instr->type == nir_instr_type_phi) {
nir_phi_instr *phi = nir_instr_as_phi(instr);
nir_block *phi_lca = NULL;
nir_foreach_phi_src(src, phi) {
if (&src->src == use)
phi_lca = nir_dominance_lca(phi_lca, src->pred);
}
use_block = phi_lca;
}
/* If we're moving a load_ubo or load_interpolated_input, we don't want to
* sink it down into loops, which may result in accessing memory or shared
* functions multiple times. Sink it just above the start of the loop
* where it's used. For load_consts, undefs, and comparisons, we expect
* the driver to be able to emit them as simple ALU ops, so sinking as far
* in as we can go is probably worth it for register pressure.
*/
if (!sink_into_loops) {
use_block = adjust_block_for_loops(use_block, def_loop);
assert(nir_block_dominates(def->parent_instr->block, use_block));
}
lca = nir_dominance_lca(lca, use_block);
}
nir_foreach_if_use(use, def) {
nir_block *use_block =
nir_cf_node_as_block(nir_cf_node_prev(&use->parent_if->cf_node));
if (!sink_into_loops) {
use_block = adjust_block_for_loops(use_block, def_loop);
assert(nir_block_dominates(def->parent_instr->block, use_block));
}
lca = nir_dominance_lca(lca, use_block);
}
return lca;
}
/* insert before first non-phi instruction: */
static void
insert_after_phi(nir_instr *instr, nir_block *block)
{
nir_foreach_instr(instr2, block) {
if (instr2->type == nir_instr_type_phi)
continue;
exec_node_insert_node_before(&instr2->node,
&instr->node);
return;
}
/* if haven't inserted it, push to tail (ie. empty block or possibly
* a block only containing phi's?)
*/
exec_list_push_tail(&block->instr_list, &instr->node);
}
bool
nir_opt_sink(nir_shader *shader, nir_move_options options)
{
bool progress = false;
nir_foreach_function(function, shader) {
if (!function->impl)
continue;
nir_metadata_require(function->impl,
nir_metadata_block_index | nir_metadata_dominance);
nir_foreach_block_reverse(block, function->impl) {
nir_foreach_instr_reverse_safe(instr, block) {
if (!nir_can_move_instr(instr, options))
continue;
nir_ssa_def *def = nir_instr_ssa_def(instr);
nir_block *use_block =
get_preferred_block(def, instr->type != nir_instr_type_intrinsic);
if (!use_block || use_block == instr->block)
continue;
exec_node_remove(&instr->node);
insert_after_phi(instr, use_block);
instr->block = use_block;
progress = true;
}
}
nir_metadata_preserve(function->impl,
nir_metadata_block_index | nir_metadata_dominance);
}
return progress;
}
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