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/*
* Copyright © 2019 Intel 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/nir_builder.h"
#include "nir_constant_expressions.h"
#include "nir_control_flow.h"
#include "nir_loop_analyze.h"
static bool
is_two_src_comparison(const nir_alu_instr *instr)
{
switch (instr->op) {
case nir_op_flt:
case nir_op_flt32:
case nir_op_fge:
case nir_op_fge32:
case nir_op_feq:
case nir_op_feq32:
case nir_op_fne:
case nir_op_fne32:
case nir_op_ilt:
case nir_op_ilt32:
case nir_op_ult:
case nir_op_ult32:
case nir_op_ige:
case nir_op_ige32:
case nir_op_uge:
case nir_op_uge32:
case nir_op_ieq:
case nir_op_ieq32:
case nir_op_ine:
case nir_op_ine32:
return true;
default:
return false;
}
}
static bool
all_srcs_are_ssa(const nir_alu_instr *instr)
{
for (unsigned i = 0; i < nir_op_infos[instr->op].num_inputs; i++) {
if (!instr->src[i].src.is_ssa)
return false;
}
return true;
}
static bool
all_uses_are_bcsel(const nir_alu_instr *instr)
{
if (!instr->dest.dest.is_ssa)
return false;
nir_foreach_use(use, &instr->dest.dest.ssa) {
if (use->parent_instr->type != nir_instr_type_alu)
return false;
nir_alu_instr *const alu = nir_instr_as_alu(use->parent_instr);
if (alu->op != nir_op_bcsel &&
alu->op != nir_op_b32csel)
return false;
/* Not only must the result be used by a bcsel, but it must be used as
* the first source (the condition).
*/
if (alu->src[0].src.ssa != &instr->dest.dest.ssa)
return false;
}
return true;
}
static bool
nir_opt_rematerialize_compares_impl(nir_shader *shader, nir_function_impl *impl)
{
bool progress = false;
nir_foreach_block(block, impl) {
nir_foreach_instr(instr, block) {
if (instr->type != nir_instr_type_alu)
continue;
nir_alu_instr *const alu = nir_instr_as_alu(instr);
if (!is_two_src_comparison(alu))
continue;
if (!all_srcs_are_ssa(alu))
continue;
if (!all_uses_are_bcsel(alu))
continue;
/* At this point it is known that alu is a comparison instruction
* that is only used by nir_op_bcsel and possibly by if-statements
* (though the latter has not been explicitly checked).
*
* Iterate through each use of the comparison. For every use (or use
* by an if-statement) that is in a different block, emit a copy of
* the comparison. Care must be taken here. The original
* instruction must be duplicated only once in each block because CSE
* cannot be run after this pass.
*/
nir_foreach_use_safe(use, &alu->dest.dest.ssa) {
nir_instr *const use_instr = use->parent_instr;
/* If the use is in the same block as the def, don't
* rematerialize.
*/
if (use_instr->block == alu->instr.block)
continue;
nir_alu_instr *clone = nir_alu_instr_clone(shader, alu);
nir_instr_insert_before(use_instr, &clone->instr);
nir_alu_instr *const use_alu = nir_instr_as_alu(use_instr);
for (unsigned i = 0; i < nir_op_infos[use_alu->op].num_inputs; i++) {
if (use_alu->src[i].src.ssa == &alu->dest.dest.ssa) {
nir_instr_rewrite_src(&use_alu->instr,
&use_alu->src[i].src,
nir_src_for_ssa(&clone->dest.dest.ssa));
progress = true;
}
}
}
nir_foreach_if_use_safe(use, &alu->dest.dest.ssa) {
nir_if *const if_stmt = use->parent_if;
nir_block *const prev_block =
nir_cf_node_as_block(nir_cf_node_prev(&if_stmt->cf_node));
/* If the compare is from the previous block, don't
* rematerialize.
*/
if (prev_block == alu->instr.block)
continue;
nir_alu_instr *clone = nir_alu_instr_clone(shader, alu);
nir_instr_insert_after_block(prev_block, &clone->instr);
nir_if_rewrite_condition(if_stmt,
nir_src_for_ssa(&clone->dest.dest.ssa));
progress = true;
}
}
}
if (progress) {
nir_metadata_preserve(impl, nir_metadata_block_index |
nir_metadata_dominance);
}
return progress;
}
bool
nir_opt_rematerialize_compares(nir_shader *shader)
{
bool progress = false;
nir_foreach_function(function, shader) {
if (function->impl == NULL)
continue;
progress = nir_opt_rematerialize_compares_impl(shader, function->impl)
|| progress;
}
return progress;
}
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