src/panfrost/midgard/midgard_opt_perspective.c

   1 /*
   2  * Copyright (C) 2019 Collabora, Ltd.
   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 FROM,
  20  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  21  * SOFTWARE.
  22  */
  23
  24 /* Midgard has some accelerated support for perspective projection on the
  25  * load/store pipes. So the first perspective projection pass looks for
  26  * lowered/open-coded perspective projection of the form "fmul (A.xyz,
  27  * frcp(A.w))" or "fmul (A.xy, frcp(A.z))" and rewrite with a native
  28  * perspective division opcode (on the load/store pipe). Caveats apply: the
  29  * frcp should be used only once to make this optimization worthwhile. And the
  30  * source of the frcp ought to be a varying to make it worthwhile...
  31  *
  32  * The second pass in this file is a step #2 of sorts: fusing that load/store
  33  * projection into a varying load instruction (they can be done together
  34  * implicitly). This depends on the combination pass. Again caveat: the vary
  35  * should only be used once to make this worthwhile.
  36  */
  37
  38 #include "compiler.h"
  39
  40 static bool
  41 is_swizzle_0(unsigned *swizzle)
  42 {
  43         for (unsigned c = 0; c < MIR_VEC_COMPONENTS; ++c)
  44                 if (swizzle[c])
  45                         return false;
  46
  47         return true;
  48 }
  49
  50 bool
  51 midgard_opt_combine_projection(compiler_context *ctx, midgard_block *block)
  52 {
  53         bool progress = false;
  54
  55         mir_foreach_instr_in_block_safe(block, ins) {
  56                 /* First search for fmul */
  57                 if (ins->type != TAG_ALU_4) continue;
  58                 if (ins->alu.op != midgard_alu_op_fmul) continue;
  59
  60                 /* TODO: Flip */
  61
  62                 /* Check the swizzles */
  63
  64                 if (!mir_is_simple_swizzle(ins->swizzle[0], ins->mask)) continue;
  65                 if (!is_swizzle_0(ins->swizzle[1])) continue;
  66
  67                 /* Awesome, we're the right form. Now check where src2 is from */
  68                 unsigned frcp = ins->src[1];
  69                 unsigned to = ins->dest;
  70
  71                 if (frcp & PAN_IS_REG) continue;
  72                 if (to & PAN_IS_REG) continue;
  73
  74                 bool frcp_found = false;
  75                 unsigned frcp_component = 0;
  76                 unsigned frcp_from = 0;
  77
  78                 mir_foreach_instr_in_block_safe(block, sub) {
  79                         if (sub->dest != frcp) continue;
  80
  81                         frcp_component = sub->swizzle[0][0];
  82                         frcp_from = sub->src[0];
  83
  84                         frcp_found =
  85                                 (sub->type == TAG_ALU_4) &&
  86                                 (sub->alu.op == midgard_alu_op_frcp);
  87                         break;
  88                 }
  89
  90                 if (!frcp_found) continue;
  91                 if (frcp_component != COMPONENT_W && frcp_component != COMPONENT_Z) continue;
  92                 if (!mir_single_use(ctx, frcp)) continue;
  93
  94                 /* Heuristic: check if the frcp is from a single-use varying */
  95
  96                 bool ok = false;
  97
  98                 /* One for frcp and one for fmul */
  99                 if (mir_use_count(ctx, frcp_from) > 2) continue;
 100
 101                 mir_foreach_instr_in_block_safe(block, v) {
 102                         if (v->dest != frcp_from) continue;
 103                         if (v->type != TAG_LOAD_STORE_4) break;
 104                         if (!OP_IS_LOAD_VARY_F(v->load_store.op)) break;
 105
 106                         ok = true;
 107                         break;
 108                 }
 109
 110                 if (!ok)
 111                         continue;
 112
 113                 /* Nice, we got the form spot on. Let's convert! */
 114
 115                 midgard_instruction accel = {
 116                         .type = TAG_LOAD_STORE_4,
 117                         .mask = ins->mask,
 118                         .dest = to,
 119                         .src = { frcp_from, ~0, ~0, ~0 },
 120                         .swizzle = SWIZZLE_IDENTITY_4,
 121                         .load_store = {
 122                                 .op = frcp_component == COMPONENT_W ?
 123                                         midgard_op_ldst_perspective_division_w :
 124                                         midgard_op_ldst_perspective_division_z,
 125                                 .arg_1 = 0x20
 126                         }
 127                 };
 128
 129                 mir_insert_instruction_before(ctx, ins, accel);
 130                 mir_remove_instruction(ins);
 131
 132                 progress |= true;
 133         }
 134
 135         return progress;
 136 }
 137
 138 bool
 139 midgard_opt_varying_projection(compiler_context *ctx, midgard_block *block)
 140 {
 141         bool progress = false;
 142
 143         mir_foreach_instr_in_block_safe(block, ins) {
 144                 /* Search for a projection */
 145                 if (ins->type != TAG_LOAD_STORE_4) continue;
 146                 if (!OP_IS_PROJECTION(ins->load_store.op)) continue;
 147
 148                 unsigned vary = ins->src[0];
 149                 unsigned to = ins->dest;
 150
 151                 if (vary & PAN_IS_REG) continue;
 152                 if (to & PAN_IS_REG) continue;
 153                 if (!mir_single_use(ctx, vary)) continue;
 154
 155                 /* Check for a varying source. If we find it, we rewrite */
 156
 157                 bool rewritten = false;
 158
 159                 mir_foreach_instr_in_block_safe(block, v) {
 160                         if (v->dest != vary) continue;
 161                         if (v->type != TAG_LOAD_STORE_4) break;
 162                         if (!OP_IS_LOAD_VARY_F(v->load_store.op)) break;
 163
 164                         /* We found it, so rewrite it to project. Grab the
 165                          * modifier */
 166
 167                         unsigned param = v->load_store.varying_parameters;
 168                         midgard_varying_parameter p;
 169                         memcpy(&p, &param, sizeof(p));
 170
 171                         if (p.modifier != midgard_varying_mod_none)
 172                                 break;
 173
 174                         bool projects_w =
 175                                 ins->load_store.op == midgard_op_ldst_perspective_division_w;
 176
 177                         p.modifier = projects_w ?
 178                                 midgard_varying_mod_perspective_w :
 179                                 midgard_varying_mod_perspective_z;
 180
 181                         /* Aliasing rules are annoying */
 182                         memcpy(&param, &p, sizeof(p));
 183                         v->load_store.varying_parameters = param;
 184
 185                         /* Use the new destination */
 186                         v->dest = to;
 187
 188                         rewritten = true;
 189                         break;
 190                 }
 191
 192                 if (rewritten)
 193                         mir_remove_instruction(ins);
 194
 195                 progress |= rewritten;
 196         }
 197
 198         return progress;
 199 }