src/broadcom/compiler/vir_opt_redundant_flags.c

   1 /*
   2  * Copyright © 2019 Broadcom
   3  *
   4  * Permission is hereby granted, free of charge, to any person obtaining a
   5  * copy of this software and associated documentation files (the "Software"),
   6  * to deal in the Software without restriction, including without limitation
   7  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
   8  * and/or sell copies of the Software, and to permit persons to whom the
   9  * Software is furnished to do so, subject to the following conditions:
  10  *
  11  * The above copyright notice and this permission notice (including the next
  12  * paragraph) shall be included in all copies or substantial portions of the
  13  * Software.
  14  *
  15  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  16  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  17  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
  18  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  19  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  20  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
  21  * IN THE SOFTWARE.
  22  */
  23
  24 /**
  25  * @file v3d_opt_redundant_flags.c
  26  *
  27  * This eliminates the APF/MPF flags for redundant flags updates.  These are
  28  * often produced by our channel masking in nonuniform control flow.
  29  */
  30
  31 #include "v3d_compiler.h"
  32
  33 static bool debug;
  34
  35 static void
  36 vir_dce_pf(struct v3d_compile *c, struct qinst *inst)
  37 {
  38         if (debug) {
  39                 fprintf(stderr,
  40                         "Removing flags write from: ");
  41                 vir_dump_inst(c, inst);
  42                 fprintf(stderr, "\n");
  43         }
  44
  45         assert(inst->qpu.type == V3D_QPU_INSTR_TYPE_ALU);
  46
  47         inst->qpu.flags.apf = V3D_QPU_PF_NONE;
  48         inst->qpu.flags.mpf = V3D_QPU_PF_NONE;
  49 }
  50
  51 static bool
  52 vir_sources_modified(struct qinst *srcs, struct qinst *write)
  53 {
  54         for (int i = 0; i < vir_get_nsrc(srcs); i++) {
  55                 if (write->dst.file == QFILE_TEMP &&
  56                     srcs->src[i].file == QFILE_TEMP &&
  57                     srcs->src[i].index == write->dst.index) {
  58                         return true;
  59                 }
  60
  61                 /* assume magic regs may be modified by basically anything. */
  62                 if (srcs->src[i].file != QFILE_TEMP &&
  63                     srcs->src[i].file != QFILE_SMALL_IMM)
  64                         return true;
  65         }
  66
  67         return false;
  68 }
  69
  70 static bool
  71 vir_instr_flags_op_equal(struct qinst *a, struct qinst *b)
  72 {
  73         for (int i = 0; i < vir_get_nsrc(a); i++) {
  74                 if (a->src[i].file != b->src[i].file ||
  75                     a->src[i].index != b->src[i].index) {
  76                         return false;
  77                 }
  78         }
  79
  80         if (a->qpu.flags.apf != b->qpu.flags.apf ||
  81             a->qpu.flags.mpf != b->qpu.flags.mpf ||
  82             a->qpu.alu.add.op != b->qpu.alu.add.op ||
  83             a->qpu.alu.mul.op != b->qpu.alu.mul.op ||
  84             a->qpu.alu.add.a_unpack != b->qpu.alu.add.a_unpack ||
  85             a->qpu.alu.add.b_unpack != b->qpu.alu.add.b_unpack ||
  86             a->qpu.alu.add.output_pack != b->qpu.alu.add.output_pack ||
  87             a->qpu.alu.mul.a_unpack != b->qpu.alu.mul.a_unpack ||
  88             a->qpu.alu.mul.b_unpack != b->qpu.alu.mul.b_unpack ||
  89             a->qpu.alu.mul.output_pack != b->qpu.alu.mul.output_pack) {
  90                 return false;
  91         }
  92
  93         return true;
  94 }
  95
  96 static bool
  97 vir_opt_redundant_flags_block(struct v3d_compile *c, struct qblock *block)
  98 {
  99         struct qinst *last_flags = NULL;
 100         bool progress = false;
 101
 102         vir_for_each_inst(inst, block) {
 103                 if (inst->qpu.type != V3D_QPU_INSTR_TYPE_ALU ||
 104                     inst->qpu.flags.auf != V3D_QPU_UF_NONE ||
 105                     inst->qpu.flags.muf != V3D_QPU_UF_NONE) {
 106                         last_flags = NULL;
 107                         continue;
 108                 }
 109
 110                 /* Flags aren't preserved across a thrsw. */
 111                 if (inst->qpu.sig.thrsw)
 112                         last_flags = NULL;
 113
 114                 if (inst->qpu.flags.apf != V3D_QPU_PF_NONE ||
 115                     inst->qpu.flags.mpf != V3D_QPU_PF_NONE) {
 116                         if (last_flags &&
 117                             vir_instr_flags_op_equal(inst, last_flags)) {
 118                                 vir_dce_pf(c, inst);
 119                                 progress = true;
 120                         } else {
 121                                 last_flags = inst;
 122                         }
 123                 }
 124
 125                 if (last_flags && vir_sources_modified(last_flags, inst)) {
 126                         last_flags = NULL;
 127                 }
 128         }
 129
 130         return progress;
 131 }
 132
 133 bool
 134 vir_opt_redundant_flags(struct v3d_compile *c)
 135 {
 136         bool progress = false;
 137
 138         vir_for_each_block(block, c) {
 139                 progress = vir_opt_redundant_flags_block(c, block) || progress;
 140         }
 141
 142         return progress;
 143 }