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/*
* Copyright © 2014 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.
*
* Authors:
* Connor Abbott (cwabbott0@gmail.com)
*
*/
#include "nir.h"
/* SSA-based mark-and-sweep dead code elimination */
typedef struct {
struct exec_node node;
nir_instr *instr;
} worklist_elem;
static void
worklist_push(struct exec_list *worklist, nir_instr *instr)
{
worklist_elem *elem = ralloc(worklist, worklist_elem);
elem->instr = instr;
instr->pass_flags = 1;
exec_list_push_tail(worklist, &elem->node);
}
static nir_instr *
worklist_pop(struct exec_list *worklist)
{
struct exec_node *node = exec_list_pop_head(worklist);
worklist_elem *elem = exec_node_data(worklist_elem, node, node);
return elem->instr;
}
static bool
mark_live_cb(nir_src *src, void *_state)
{
struct exec_list *worklist = (struct exec_list *) _state;
if (src->is_ssa && !src->ssa->parent_instr->pass_flags) {
worklist_push(worklist, src->ssa->parent_instr);
}
return true;
}
static void
init_instr(nir_instr *instr, struct exec_list *worklist)
{
nir_alu_instr *alu_instr;
nir_intrinsic_instr *intrin_instr;
nir_tex_instr *tex_instr;
/* We use the pass_flags to store the live/dead information. In DCE, we
* just treat it as a zero/non-zerl boolean for whether or not the
* instruction is live.
*/
instr->pass_flags = 0;
switch (instr->type) {
case nir_instr_type_call:
case nir_instr_type_jump:
worklist_push(worklist, instr);
break;
case nir_instr_type_alu:
alu_instr = nir_instr_as_alu(instr);
if (!alu_instr->dest.dest.is_ssa)
worklist_push(worklist, instr);
break;
case nir_instr_type_intrinsic:
intrin_instr = nir_instr_as_intrinsic(instr);
if (nir_intrinsic_infos[intrin_instr->intrinsic].flags &
NIR_INTRINSIC_CAN_ELIMINATE) {
if (nir_intrinsic_infos[intrin_instr->intrinsic].has_dest &&
!intrin_instr->dest.is_ssa) {
worklist_push(worklist, instr);
}
} else {
worklist_push(worklist, instr);
}
break;
case nir_instr_type_tex:
tex_instr = nir_instr_as_tex(instr);
if (!tex_instr->dest.is_ssa)
worklist_push(worklist, instr);
break;
default:
break;
}
}
static bool
init_block_cb(nir_block *block, void *_state)
{
struct exec_list *worklist = (struct exec_list *) _state;
nir_foreach_instr(block, instr)
init_instr(instr, worklist);
nir_if *following_if = nir_block_get_following_if(block);
if (following_if) {
if (following_if->condition.is_ssa &&
!following_if->condition.ssa->parent_instr->pass_flags)
worklist_push(worklist, following_if->condition.ssa->parent_instr);
}
return true;
}
static bool
delete_block_cb(nir_block *block, void *_state)
{
bool *progress = (bool *) _state;
nir_foreach_instr_safe(block, instr) {
if (!instr->pass_flags) {
nir_instr_remove(instr);
*progress = true;
}
}
return true;
}
bool
nir_opt_dce_impl(nir_function_impl *impl)
{
struct exec_list *worklist = ralloc(NULL, struct exec_list);
exec_list_make_empty(worklist);
nir_foreach_block(impl, init_block_cb, worklist);
while (!exec_list_is_empty(worklist)) {
nir_instr *instr = worklist_pop(worklist);
nir_foreach_src(instr, mark_live_cb, worklist);
}
ralloc_free(worklist);
bool progress = false;
nir_foreach_block(impl, delete_block_cb, &progress);
if (progress)
nir_metadata_preserve(impl, nir_metadata_block_index |
nir_metadata_dominance);
return progress;
}
bool
nir_opt_dce(nir_shader *shader)
{
bool progress = false;
nir_foreach_overload(shader, overload) {
if (overload->impl && nir_opt_dce_impl(overload->impl))
progress = true;
}
return progress;
}
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