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/*
* Copyright © 2015 Broadcom
*
* 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"
/** @file nir_opt_undef.c
*
* Handles optimization of operations involving ssa_undef.
*/
/**
* Turn conditional selects between an undef and some other value into a move
* of that other value (on the assumption that the condition's going to be
* choosing the defined value). This reduces work after if flattening when
* each side of the if is defining a variable.
*/
static bool
opt_undef_csel(nir_alu_instr *instr)
{
if (instr->op != nir_op_bcsel && instr->op != nir_op_fcsel)
return false;
assert(instr->dest.dest.is_ssa);
for (int i = 1; i <= 2; i++) {
if (!instr->src[i].src.is_ssa)
continue;
nir_instr *parent = instr->src[i].src.ssa->parent_instr;
if (parent->type != nir_instr_type_ssa_undef)
continue;
/* We can't just use nir_alu_src_copy, because we need the def/use
* updated.
*/
nir_instr_rewrite_src(&instr->instr, &instr->src[0].src,
instr->src[i == 1 ? 2 : 1].src);
nir_alu_src_copy(&instr->src[0], &instr->src[i == 1 ? 2 : 1],
ralloc_parent(instr));
nir_src empty_src;
memset(&empty_src, 0, sizeof(empty_src));
nir_instr_rewrite_src(&instr->instr, &instr->src[1].src, empty_src);
nir_instr_rewrite_src(&instr->instr, &instr->src[2].src, empty_src);
instr->op = nir_op_imov;
return true;
}
return false;
}
/**
* Replace vecN(undef, undef, ...) with a single undef.
*/
static bool
opt_undef_vecN(nir_builder *b, nir_alu_instr *alu)
{
if (alu->op != nir_op_vec2 &&
alu->op != nir_op_vec3 &&
alu->op != nir_op_vec4)
return false;
assert(alu->dest.dest.is_ssa);
unsigned num_components = nir_op_infos[alu->op].num_inputs;
for (unsigned i = 0; i < num_components; i++) {
if (!alu->src[i].src.is_ssa ||
alu->src[i].src.ssa->parent_instr->type != nir_instr_type_ssa_undef)
return false;
}
b->cursor = nir_before_instr(&alu->instr);
nir_ssa_def *undef =
nir_ssa_undef(b, num_components, nir_dest_bit_size(alu->dest.dest));
nir_ssa_def_rewrite_uses(&alu->dest.dest.ssa, nir_src_for_ssa(undef));
return true;
}
/**
* Remove any store intrinsics whose value is undefined (the existing
* value is a fine representation of "undefined").
*/
static bool
opt_undef_store(nir_intrinsic_instr *intrin)
{
switch (intrin->intrinsic) {
case nir_intrinsic_store_var:
case nir_intrinsic_store_output:
case nir_intrinsic_store_per_vertex_output:
case nir_intrinsic_store_ssbo:
case nir_intrinsic_store_shared:
break;
default:
return false;
}
if (!intrin->src[0].is_ssa ||
intrin->src[0].ssa->parent_instr->type != nir_instr_type_ssa_undef)
return false;
nir_instr_remove(&intrin->instr);
return true;
}
bool
nir_opt_undef(nir_shader *shader)
{
nir_builder b;
bool progress = false;
nir_foreach_function(function, shader) {
if (function->impl) {
nir_builder_init(&b, function->impl);
nir_foreach_block(block, function->impl) {
nir_foreach_instr_safe(instr, block) {
if (instr->type == nir_instr_type_alu) {
nir_alu_instr *alu = nir_instr_as_alu(instr);
progress = opt_undef_csel(alu) || progress;
progress = opt_undef_vecN(&b, alu) || progress;
} else if (instr->type == nir_instr_type_intrinsic) {
nir_intrinsic_instr *intrin = nir_instr_as_intrinsic(instr);
progress = opt_undef_store(intrin) || progress;
}
}
}
if (progress)
nir_metadata_preserve(function->impl,
nir_metadata_block_index |
nir_metadata_dominance);
}
}
return progress;
}
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