| /* |
| * Copyright © 2016 Broadcom |
| * |
| * 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. |
| */ |
| |
| /** |
| * @file vc4_opt_peephole_sf.c |
| * |
| * Quick optimization to eliminate unused or identical SF updates. |
| */ |
| |
| #include "vc4_qir.h" |
| #include "util/u_math.h" |
| |
| static bool debug; |
| |
| static void |
| dump_from(struct vc4_compile *c, struct qinst *inst, const char *type) |
| { |
| if (!debug) |
| return; |
| |
| fprintf(stderr, "optimizing %s: ", type); |
| qir_dump_inst(c, inst); |
| fprintf(stderr, "\n"); |
| } |
| |
| static void |
| dump_to(struct vc4_compile *c, struct qinst *inst) |
| { |
| if (!debug) |
| return; |
| |
| fprintf(stderr, "to: "); |
| qir_dump_inst(c, inst); |
| fprintf(stderr, "\n"); |
| } |
| |
| static bool |
| inst_srcs_updated(struct qinst *inst, struct qinst *writer) |
| { |
| /* If the sources get overwritten, stop tracking the |
| * last instruction writing SF. |
| */ |
| switch (writer->dst.file) { |
| case QFILE_TEMP: |
| for (int i = 0; i < qir_get_nsrc(inst); i++) { |
| if (inst->src[i].file == QFILE_TEMP && |
| inst->src[i].index == writer->dst.index) { |
| return true; |
| } |
| } |
| return false; |
| default: |
| return false; |
| } |
| } |
| |
| static bool |
| src_file_varies_on_reread(struct qreg reg) |
| { |
| switch (reg.file) { |
| case QFILE_VARY: |
| case QFILE_VPM: |
| return true; |
| default: |
| return false; |
| } |
| } |
| |
| static bool |
| inst_result_equals(struct qinst *a, struct qinst *b) |
| { |
| if (a->op != b->op || |
| qir_depends_on_flags(a) || |
| qir_depends_on_flags(b)) { |
| return false; |
| } |
| |
| for (int i = 0; i < qir_get_nsrc(a); i++) { |
| if (!qir_reg_equals(a->src[i], b->src[i]) || |
| src_file_varies_on_reread(a->src[i]) || |
| src_file_varies_on_reread(b->src[i])) { |
| return false; |
| } |
| } |
| |
| return true; |
| } |
| |
| static bool |
| qir_opt_peephole_sf_block(struct vc4_compile *c, struct qblock *block) |
| { |
| bool progress = false; |
| /* We don't have liveness dataflow analysis for flags, but we also |
| * never generate a use of flags across control flow, so just treat |
| * them as unused at block exit. |
| */ |
| bool sf_live = false; |
| struct qinst *last_sf = NULL; |
| |
| /* Walk the block from bottom to top, tracking if the SF is used, and |
| * removing unused or repeated ones. |
| */ |
| qir_for_each_inst_rev(inst, block) { |
| if (inst->sf) { |
| if (!sf_live) { |
| /* Our instruction's SF isn't read, so drop it. |
| */ |
| dump_from(c, inst, "dead SF"); |
| inst->sf = false; |
| dump_to(c, inst); |
| progress = true; |
| } else if (last_sf && |
| inst_result_equals(last_sf, inst)) { |
| /* The last_sf sets up same value as inst, so |
| * just drop the later one. |
| */ |
| dump_from(c, last_sf, "repeated SF"); |
| last_sf->sf = false; |
| dump_to(c, last_sf); |
| progress = true; |
| last_sf = inst; |
| } else { |
| last_sf = inst; |
| } |
| sf_live = false; |
| } |
| |
| if (last_sf) { |
| if (inst_srcs_updated(last_sf, inst)) |
| last_sf = NULL; |
| } |
| |
| if (qir_depends_on_flags(inst)) |
| sf_live = true; |
| } |
| |
| return progress; |
| } |
| |
| bool |
| qir_opt_peephole_sf(struct vc4_compile *c) |
| { |
| bool progress = false; |
| |
| qir_for_each_block(block, c) |
| progress = qir_opt_peephole_sf_block(c, block) || progress; |
| |
| return progress; |
| } |