169 lines
5.7 KiB
C
169 lines
5.7 KiB
C
/*
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* Copyright (C) 2018 Alyssa Rosenzweig
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* Copyright (C) 2019 Collabora, Ltd.
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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 FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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* SOFTWARE.
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*/
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#include "compiler.h"
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#include "util/u_memory.h"
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#include "midgard_ops.h"
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/* SIMD-aware dead code elimination. Perform liveness analysis step-by-step,
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* removing dead components. If an instruction ends up with a zero mask, the
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* instruction in total is dead and should be removed. */
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static bool
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can_cull_mask(compiler_context *ctx, midgard_instruction *ins)
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{
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if (ins->dest >= ctx->temp_count)
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return false;
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if (ins->dest == ctx->blend_src1)
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return false;
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if (ins->type == TAG_LOAD_STORE_4)
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if (load_store_opcode_props[ins->op].props & LDST_SPECIAL_MASK)
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return false;
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return true;
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}
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static bool
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can_dce(midgard_instruction *ins)
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{
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if (ins->mask)
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return false;
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if (ins->compact_branch)
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return false;
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if (ins->type == TAG_LOAD_STORE_4)
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if (load_store_opcode_props[ins->op].props & LDST_SIDE_FX)
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return false;
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if (ins->type == TAG_TEXTURE_4)
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if (ins->op == midgard_tex_op_barrier)
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return false;
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return true;
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}
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static bool
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midgard_opt_dead_code_eliminate_block(compiler_context *ctx, midgard_block *block)
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{
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bool progress = false;
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uint16_t *live = mem_dup(block->base.live_out, ctx->temp_count * sizeof(uint16_t));
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mir_foreach_instr_in_block_rev(block, ins) {
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if (can_cull_mask(ctx, ins)) {
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unsigned type_size = nir_alu_type_get_type_size(ins->dest_type);
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unsigned round_size = type_size;
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unsigned oldmask = ins->mask;
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/* Make sure we're packable */
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if (type_size < 32 && ins->type == TAG_LOAD_STORE_4)
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round_size = 32;
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unsigned rounded = mir_round_bytemask_up(live[ins->dest], round_size);
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unsigned cmask = mir_from_bytemask(rounded, type_size);
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ins->mask &= cmask;
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progress |= (ins->mask != oldmask);
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}
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mir_liveness_ins_update(live, ins, ctx->temp_count);
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}
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mir_foreach_instr_in_block_safe(block, ins) {
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if (can_dce(ins)) {
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mir_remove_instruction(ins);
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progress = true;
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}
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}
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free(live);
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return progress;
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}
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bool
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midgard_opt_dead_code_eliminate(compiler_context *ctx)
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{
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/* We track liveness. In fact, it's ok if we assume more things are
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* live than they actually are, that just reduces the effectiveness of
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* this iterations lightly. And DCE has the effect of strictly reducing
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* liveness, so we can run DCE across all blocks while only computing
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* liveness at the beginning. */
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mir_invalidate_liveness(ctx);
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mir_compute_liveness(ctx);
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bool progress = false;
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mir_foreach_block(ctx, block) {
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progress |= midgard_opt_dead_code_eliminate_block(ctx, (midgard_block *) block);
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}
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return progress;
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}
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/* Removes dead moves, that is, moves with a destination overwritten before
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* being read. Normally handled implicitly as part of DCE, but this has to run
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* after the out-of-SSA pass */
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bool
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midgard_opt_dead_move_eliminate(compiler_context *ctx, midgard_block *block)
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{
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bool progress = false;
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mir_foreach_instr_in_block_safe(block, ins) {
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if (ins->type != TAG_ALU_4) continue;
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if (ins->compact_branch) continue;
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if (!OP_IS_MOVE(ins->op)) continue;
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/* Check if it's overwritten in this block before being read */
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bool overwritten = false;
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mir_foreach_instr_in_block_from(block, q, mir_next_op(ins)) {
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/* Check if used */
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if (mir_has_arg(q, ins->dest))
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break;
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/* Check if overwritten */
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if (q->dest == ins->dest) {
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/* Special case to vec4; component tracking is
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* harder */
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overwritten = (q->mask == 0xF);
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break;
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}
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}
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if (overwritten) {
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mir_remove_instruction(ins);
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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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