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/*
* Copyright © 2016 Red Hat
*
* 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_conditional_discard.c
*
* Handles optimization of lowering if (cond) discard to discard_if(cond).
*/
static bool
nir_opt_conditional_discard_block(nir_block *block, void *mem_ctx)
{
nir_builder bld;
if (nir_cf_node_is_first(&block->cf_node))
return false;
nir_cf_node *prev_node = nir_cf_node_prev(&block->cf_node);
if (prev_node->type != nir_cf_node_if)
return false;
nir_if *if_stmt = nir_cf_node_as_if(prev_node);
nir_block *then_block = nir_if_first_then_block(if_stmt);
nir_block *else_block = nir_if_first_else_block(if_stmt);
/* check there is only one else block and it is empty */
if (nir_if_last_else_block(if_stmt) != else_block)
return false;
if (!exec_list_is_empty(&else_block->instr_list))
return false;
/* check there is only one then block and it has only one instruction in it */
if (nir_if_last_then_block(if_stmt) != then_block)
return false;
if (exec_list_is_empty(&then_block->instr_list))
return false;
if (exec_list_length(&then_block->instr_list) > 1)
return false;
/*
* make sure no subsequent phi nodes point at this if.
*/
nir_block *after = nir_cf_node_as_block(nir_cf_node_next(&if_stmt->cf_node));
nir_foreach_instr_safe(instr, after) {
if (instr->type != nir_instr_type_phi)
break;
nir_phi_instr *phi = nir_instr_as_phi(instr);
nir_foreach_phi_src(phi_src, phi) {
if (phi_src->pred == then_block ||
phi_src->pred == else_block)
return false;
}
}
/* Get the first instruction in the then block and confirm it is
* a discard or a discard_if
*/
nir_instr *instr = nir_block_first_instr(then_block);
if (instr->type != nir_instr_type_intrinsic)
return false;
nir_intrinsic_instr *intrin = nir_instr_as_intrinsic(instr);
if (intrin->intrinsic != nir_intrinsic_discard &&
intrin->intrinsic != nir_intrinsic_discard_if)
return false;
nir_src cond;
nir_builder_init(&bld, mem_ctx);
bld.cursor = nir_before_cf_node(prev_node);
if (intrin->intrinsic == nir_intrinsic_discard)
cond = if_stmt->condition;
else
cond = nir_src_for_ssa(nir_iand(&bld,
nir_ssa_for_src(&bld, if_stmt->condition, 1),
nir_ssa_for_src(&bld, intrin->src[0], 1)));
nir_intrinsic_instr *discard_if =
nir_intrinsic_instr_create(mem_ctx, nir_intrinsic_discard_if);
nir_src_copy(&discard_if->src[0], &cond, discard_if);
nir_instr_insert_before_cf(prev_node, &discard_if->instr);
nir_instr_remove(&intrin->instr);
nir_cf_node_remove(&if_stmt->cf_node);
return true;
}
bool
nir_opt_conditional_discard(nir_shader *shader)
{
bool progress = false;
nir_foreach_function(function, shader) {
if (function->impl) {
void *mem_ctx = ralloc_parent(function->impl);
nir_foreach_block_safe(block, function->impl) {
progress |= nir_opt_conditional_discard_block(block, mem_ctx);
}
}
}
return progress;
}
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