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/*
* Copyright © 2016 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"
static bool
instr_is_continue(nir_instr *instr)
{
if (instr->type != nir_instr_type_jump)
return false;
return nir_instr_as_jump(instr)->type == nir_jump_continue;
}
static bool
lower_trivial_continues_block(nir_block *block, nir_loop *loop)
{
bool progress = false;
nir_instr *first_instr = nir_block_first_instr(block);
if (!first_instr || instr_is_continue(first_instr)) {
/* The block contains only a continue if anything */
nir_cf_node *prev_node = nir_cf_node_prev(&block->cf_node);
if (prev_node && prev_node->type == nir_cf_node_if) {
nir_if *prev_if = nir_cf_node_as_if(prev_node);
progress |= lower_trivial_continues_block(
nir_if_last_then_block(prev_if), loop);
progress |= lower_trivial_continues_block(
nir_if_last_else_block(prev_if), loop);
}
/* The lower_phis_to_regs helper is smart enough to push phi sources as
* far up if-ladders as it possibly can. In other words, the recursive
* calls above shouldn't be adding instructions to this block since it
* follows an if statement.
*/
first_instr = nir_block_first_instr(block);
assert(!first_instr || instr_is_continue(first_instr));
}
nir_instr *last_instr = nir_block_last_instr(block);
if (!last_instr || !instr_is_continue(last_instr))
return progress;
/* We're at the end of a block that goes straight through to the end of the
* loop and continues to the top. We can exit normally instead of jump.
*/
nir_lower_phis_to_regs_block(nir_loop_first_block(loop));
nir_instr_remove(last_instr);
return true;
}
static bool
lower_trivial_continues_list(struct exec_list *cf_list,
bool list_ends_at_loop_tail,
nir_loop *loop)
{
bool progress = false;
foreach_list_typed(nir_cf_node, cf_node, node, cf_list) {
bool at_loop_tail = list_ends_at_loop_tail &&
&cf_node->node == exec_list_get_tail(cf_list);
switch (cf_node->type) {
case nir_cf_node_block:
break;
case nir_cf_node_if: {
nir_if *nif = nir_cf_node_as_if(cf_node);
if (lower_trivial_continues_list(&nif->then_list, at_loop_tail, loop))
progress = true;
if (lower_trivial_continues_list(&nif->else_list, at_loop_tail, loop))
progress = true;
break;
}
case nir_cf_node_loop: {
nir_loop *loop = nir_cf_node_as_loop(cf_node);
if (lower_trivial_continues_list(&loop->body, true, loop))
progress = true;
if (lower_trivial_continues_block(nir_loop_last_block(loop), loop))
progress = true;
break;
}
case nir_cf_node_function:
unreachable("Invalid cf type");
}
}
return progress;
}
/**
* This simple pass gets rid of any "trivial" continues, i.e. those that are
* at the tail of a loop where we can just delete the continue instruction and
* control-flow will naturally and harmlessly take us back to the top of the
* loop.
*/
bool
nir_opt_trivial_continues(nir_shader *shader)
{
bool progress = false;
nir_foreach_function(function, shader) {
if (function->impl == NULL)
continue;
/* First we run the simple pass to get rid of pesky continues */
if (lower_trivial_continues_list(&function->impl->body, false, NULL)) {
nir_metadata_preserve(function->impl, nir_metadata_none);
/* If that made progress, we're no longer really in SSA form. */
nir_lower_regs_to_ssa_impl(function->impl);
progress = true;
}
}
return progress;
}
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