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/*
* Copyright (C) 2018 Alyssa Rosenzweig
* Copyright (C) 2019 Collabora, Ltd.
*
* 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 "compiler.h"
/* Basic dead code elimination on the MIR itself */
bool
midgard_opt_dead_code_eliminate(compiler_context *ctx, midgard_block *block)
{
bool progress = false;
mir_foreach_instr_in_block_safe(block, ins) {
if (ins->type != TAG_ALU_4) continue;
if (ins->compact_branch) continue;
if (ins->dest >= SSA_FIXED_MINIMUM) continue;
if (mir_is_live_after(ctx, block, ins, ins->dest)) continue;
mir_remove_instruction(ins);
progress = true;
}
return progress;
}
/* Removes dead moves, that is, moves with a destination overwritten before
* being read. Normally handled implicitly as part of DCE, but this has to run
* after the out-of-SSA pass */
bool
midgard_opt_dead_move_eliminate(compiler_context *ctx, midgard_block *block)
{
bool progress = false;
mir_foreach_instr_in_block_safe(block, ins) {
if (ins->type != TAG_ALU_4) continue;
if (ins->compact_branch) continue;
if (!OP_IS_MOVE(ins->alu.op)) continue;
/* Check if it's overwritten in this block before being read */
bool overwritten = false;
mir_foreach_instr_in_block_from(block, q, mir_next_op(ins)) {
/* Check if used */
if (mir_has_arg(q, ins->dest))
break;
/* Check if overwritten */
if (q->dest == ins->dest) {
/* Special case to vec4; component tracking is
* harder */
overwritten = (q->mask == 0xF);
break;
}
}
if (overwritten) {
mir_remove_instruction(ins);
progress = true;
}
}
return progress;
}
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