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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"
/** @file nir_opt_undef.c
*
* Handles optimization of operations involving ssa_undef. For now, we just
* make sure that csels between undef and some other value just give the 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.
*
* Some day, we may find some use for making other operations consuming an
* undef arg output undef, but I don't know of any cases currently.
*/
static bool
opt_undef_alu(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;
}
static bool
opt_undef_block(nir_block *block, void *data)
{
bool *progress = data;
nir_foreach_instr_safe(block, instr) {
if (instr->type == nir_instr_type_alu)
if (opt_undef_alu(nir_instr_as_alu(instr)))
(*progress) = true;
}
return true;
}
bool
nir_opt_undef(nir_shader *shader)
{
bool progress = false;
nir_foreach_overload(shader, overload) {
if (overload->impl) {
nir_foreach_block(overload->impl, opt_undef_block, &progress);
if (progress)
nir_metadata_preserve(overload->impl,
nir_metadata_block_index |
nir_metadata_dominance);
}
}
return progress;
}
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