138 lines
4.8 KiB
C
138 lines
4.8 KiB
C
/*
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* Copyright © 2016 Intel Corporation
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*
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* Permission is hereby granted, free of charge, to any person obtaining a
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* copy of this software and associated documentation files (the "Software"),
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* to deal in the Software without restriction, including without limitation
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* the rights to use, copy, modify, merge, publish, distribute, sublicense,
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* and/or sell copies of the Software, and to permit persons to whom the
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* Software is furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice (including the next
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* paragraph) shall be included in all copies or substantial portions of the
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* Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
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* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
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* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
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* IN THE SOFTWARE.
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*/
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#include "nir.h"
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static bool
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instr_is_continue(nir_instr *instr)
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{
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if (instr->type != nir_instr_type_jump)
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return false;
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return nir_instr_as_jump(instr)->type == nir_jump_continue;
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}
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static bool
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lower_trivial_continues_block(nir_block *block, nir_loop *loop)
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{
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bool progress = false;
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nir_instr *first_instr = nir_block_first_instr(block);
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if (!first_instr || instr_is_continue(first_instr)) {
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/* The block contains only a continue if anything */
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nir_cf_node *prev_node = nir_cf_node_prev(&block->cf_node);
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if (prev_node && prev_node->type == nir_cf_node_if) {
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nir_if *prev_if = nir_cf_node_as_if(prev_node);
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progress |= lower_trivial_continues_block(
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nir_if_last_then_block(prev_if), loop);
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progress |= lower_trivial_continues_block(
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nir_if_last_else_block(prev_if), loop);
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}
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/* The lower_phis_to_regs helper is smart enough to push phi sources as
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* far up if-ladders as it possibly can. In other words, the recursive
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* calls above shouldn't be adding instructions to this block since it
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* follows an if statement.
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*/
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first_instr = nir_block_first_instr(block);
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assert(!first_instr || instr_is_continue(first_instr));
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}
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nir_instr *last_instr = nir_block_last_instr(block);
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if (!last_instr || !instr_is_continue(last_instr))
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return progress;
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/* We're at the end of a block that goes straight through to the end of the
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* loop and continues to the top. We can exit normally instead of jump.
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*/
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nir_lower_phis_to_regs_block(nir_loop_first_block(loop));
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nir_instr_remove(last_instr);
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return true;
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}
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static bool
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lower_trivial_continues_list(struct exec_list *cf_list,
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bool list_ends_at_loop_tail,
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nir_loop *loop)
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{
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bool progress = false;
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foreach_list_typed(nir_cf_node, cf_node, node, cf_list) {
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bool at_loop_tail = list_ends_at_loop_tail &&
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&cf_node->node == exec_list_get_tail(cf_list);
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switch (cf_node->type) {
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case nir_cf_node_block:
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break;
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case nir_cf_node_if: {
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nir_if *nif = nir_cf_node_as_if(cf_node);
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if (lower_trivial_continues_list(&nif->then_list, at_loop_tail, loop))
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progress = true;
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if (lower_trivial_continues_list(&nif->else_list, at_loop_tail, loop))
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progress = true;
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break;
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}
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case nir_cf_node_loop: {
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nir_loop *loop = nir_cf_node_as_loop(cf_node);
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if (lower_trivial_continues_list(&loop->body, true, loop))
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progress = true;
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if (lower_trivial_continues_block(nir_loop_last_block(loop), loop))
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progress = true;
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break;
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}
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case nir_cf_node_function:
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unreachable("Invalid cf type");
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}
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}
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return progress;
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}
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/**
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* This simple pass gets rid of any "trivial" continues, i.e. those that are
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* at the tail of a loop where we can just delete the continue instruction and
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* control-flow will naturally and harmlessly take us back to the top of the
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* loop.
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*/
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bool
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nir_opt_trivial_continues(nir_shader *shader)
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{
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bool progress = false;
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nir_foreach_function(function, shader) {
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if (function->impl == NULL)
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continue;
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/* First we run the simple pass to get rid of pesky continues */
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if (lower_trivial_continues_list(&function->impl->body, false, NULL)) {
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nir_metadata_preserve(function->impl, nir_metadata_none);
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/* If that made progress, we're no longer really in SSA form. */
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nir_lower_regs_to_ssa_impl(function->impl);
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progress = true;
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}
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}
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return progress;
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}
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