src/gallium/drivers/vc4/vc4_opt_algebraic.c

   1 /*
   2  * Copyright © 2014 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 vc4_opt_algebraic.c
  26  *
  27  * This is the optimization pass for miscellaneous changes to instructions
  28  * where we can simplify the operation by some knowledge about the specific
  29  * operations.
  30  *
  31  * Mostly this will be a matter of turning things into MOVs so that they can
  32  * later be copy-propagated out.
  33  */
  34
  35 #include "vc4_qir.h"
  36
  37 static bool debug;
  38
  39 static void
  40 dump_from(struct vc4_compile *c, struct qinst *inst)
  41 {
  42         if (!debug)
  43                 return;
  44
  45         fprintf(stderr, "optimizing: ");
  46         qir_dump_inst(c, inst);
  47         fprintf(stderr, "\n");
  48 }
  49
  50 static void
  51 dump_to(struct vc4_compile *c, struct qinst *inst)
  52 {
  53         if (!debug)
  54                 return;
  55
  56         fprintf(stderr, "to: ");
  57         qir_dump_inst(c, inst);
  58         fprintf(stderr, "\n");
  59 }
  60
  61 static struct qreg
  62 follow_movs(struct qinst **defs, struct qreg reg)
  63 {
  64         while (reg.file == QFILE_TEMP && defs[reg.index]->op == QOP_MOV)
  65                 reg = defs[reg.index]->src[0];
  66
  67         return reg;
  68 }
  69
  70 static bool
  71 is_zero(struct vc4_compile *c, struct qinst **defs, struct qreg reg)
  72 {
  73         reg = follow_movs(defs, reg);
  74
  75         return (reg.file == QFILE_UNIF &&
  76                 c->uniform_contents[reg.index] == QUNIFORM_CONSTANT &&
  77                 c->uniform_data[reg.index] == 0);
  78 }
  79
  80 static void
  81 replace_with_mov(struct vc4_compile *c, struct qinst *inst, struct qreg arg)
  82 {
  83         dump_from(c, inst);
  84         inst->op = QOP_MOV;
  85         inst->src[0] = arg;
  86         inst->src[1] = c->undef;
  87         dump_to(c, inst);
  88 }
  89
  90 bool
  91 qir_opt_algebraic(struct vc4_compile *c)
  92 {
  93         bool progress = false;
  94         struct simple_node *node;
  95         struct qinst *defs[c->num_temps];
  96
  97         foreach(node, &c->instructions) {
  98                 struct qinst *inst = (struct qinst *)node;
  99
 100                 if (inst->dst.file == QFILE_TEMP)
 101                         defs[inst->dst.index] = inst;
 102
 103                 switch (inst->op) {
 104                 case QOP_SF:
 105                         /* SF just looks at the sign bit, or whether all the
 106                          * bits are 0.  This is preserved across an itof
 107                          * transformation.
 108                          */
 109                         if (inst->src[0].file == QFILE_TEMP &&
 110                             defs[inst->src[0].index]->op == QOP_ITOF) {
 111                                 dump_from(c, inst);
 112                                 inst->src[0] =
 113                                         defs[inst->src[0].index]->src[0];
 114                                 progress =  true;
 115                                 dump_to(c, inst);
 116                                 break;
 117                         }
 118                         break;
 119
 120                 case QOP_SEL_X_Y_ZS:
 121                 case QOP_SEL_X_Y_ZC:
 122                 case QOP_SEL_X_Y_NS:
 123                 case QOP_SEL_X_Y_NC:
 124                         if (qir_reg_equals(inst->src[0], inst->src[1])) {
 125                                 /* Turn "dst = (sf == x) ? a : a)" into
 126                                  * "dst = a"
 127                                  */
 128                                 replace_with_mov(c, inst, inst->src[1]);
 129                                 progress = true;
 130                         } else if (is_zero(c, defs, inst->src[1])) {
 131                                 /* Replace references to a 0 uniform value
 132                                  * with the SEL_X_0 equivalent.
 133                                  */
 134                                 dump_from(c, inst);
 135                                 inst->op -= (QOP_SEL_X_Y_ZS - QOP_SEL_X_0_ZS);
 136                                 inst->src[1] = c->undef;
 137                                 progress = true;
 138                                 dump_to(c, inst);
 139                         }
 140                         break;
 141
 142                 case QOP_FSUB:
 143                 case QOP_SUB:
 144                         if (is_zero(c, defs, inst->src[1])) {
 145                                 replace_with_mov(c, inst, inst->src[0]);
 146                         }
 147                         break;
 148
 149                 case QOP_FADD:
 150                         /* FADD(a, FSUB(0, b)) -> FSUB(a, b) */
 151                         if (inst->src[1].file == QFILE_TEMP &&
 152                             defs[inst->src[1].index]->op == QOP_FSUB) {
 153                                 struct qinst *fsub = defs[inst->src[1].index];
 154                                 if (is_zero(c, defs, fsub->src[0])) {
 155                                         dump_from(c, inst);
 156                                         inst->op = QOP_FSUB;
 157                                         inst->src[1] = fsub->src[1];
 158                                         progress = true;
 159                                         dump_to(c, inst);
 160                                         break;
 161                                 }
 162                         }
 163
 164                         /* FADD(FSUB(0, b), a) -> FSUB(a, b) */
 165                         if (inst->src[0].file == QFILE_TEMP &&
 166                             defs[inst->src[0].index]->op == QOP_FSUB) {
 167                                 struct qinst *fsub = defs[inst->src[0].index];
 168                                 if (is_zero(c, defs, fsub->src[0])) {
 169                                         dump_from(c, inst);
 170                                         inst->op = QOP_FSUB;
 171                                         inst->src[0] = inst->src[1];
 172                                         inst->src[1] = fsub->src[1];
 173                                         dump_to(c, inst);
 174                                         progress = true;
 175                                         break;
 176                                 }
 177                         }
 178                         break;
 179
 180                 default:
 181                         break;
 182                 }
 183         }
 184
 185         return progress;
 186 }