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).
  29  *
  30  * Caveats apply: the frcp should be used only once to make this optimization
  31  * worthwhile.
  32  */
  33
  34 #include "compiler.h"
  35
  36 bool
  37 midgard_opt_combine_projection(compiler_context *ctx, midgard_block *block)
  38 {
  39         bool progress = false;
  40
  41         mir_foreach_instr_in_block_safe(block, ins) {
  42                 /* First search for fmul */
  43                 if (ins->type != TAG_ALU_4) continue;
  44                 if (ins->alu.op != midgard_alu_op_fmul) continue;
  45
  46                 /* TODO: Flip */
  47
  48                 /* Check the swizzles */
  49
  50                 midgard_vector_alu_src src1 =
  51                         vector_alu_from_unsigned(ins->alu.src1);
  52
  53                 midgard_vector_alu_src src2 =
  54                         vector_alu_from_unsigned(ins->alu.src2);
  55
  56                 if (!mir_is_simple_swizzle(src1.swizzle, ins->mask)) continue;
  57                 if (src2.swizzle != SWIZZLE_XXXX) continue;
  58
  59                 /* Awesome, we're the right form. Now check where src2 is from */
  60                 unsigned frcp = ins->ssa_args.src1;
  61                 unsigned to = ins->ssa_args.dest;
  62
  63                 if (frcp >= ctx->func->impl->ssa_alloc) continue;
  64                 if (to >= ctx->func->impl->ssa_alloc) continue;
  65
  66                 bool frcp_found = false;
  67                 unsigned frcp_component = 0;
  68                 unsigned frcp_from = 0;
  69
  70                 mir_foreach_instr_in_block_safe(block, sub) {
  71                         if (sub->ssa_args.dest != frcp) continue;
  72
  73                         midgard_vector_alu_src s =
  74                                 vector_alu_from_unsigned(sub->alu.src1);
  75
  76                         frcp_component = s.swizzle & 3;
  77                         frcp_from = sub->ssa_args.src0;
  78
  79                         frcp_found =
  80                                 (sub->type == TAG_ALU_4) &&
  81                                 (sub->alu.op == midgard_alu_op_frcp);
  82                         break;
  83                 }
  84
  85                 if (!frcp_found) continue;
  86                 if (frcp_component != COMPONENT_W && frcp_component != COMPONENT_Z) continue;
  87                 if (!mir_single_use(ctx, frcp)) continue;
  88
  89                 /* Nice, we got the form spot on. Let's convert! */
  90
  91                 midgard_instruction accel = {
  92                         .type = TAG_LOAD_STORE_4,
  93                         .mask = ins->mask,
  94                         .ssa_args = {
  95                                 .dest = to,
  96                                 .src0 = frcp_from,
  97                                 .src1 = -1
  98                         },
  99                         .load_store = {
 100                                 .op = frcp_component == COMPONENT_W ?
 101                                         midgard_op_ldst_perspective_division_w :
 102                                         midgard_op_ldst_perspective_division_z,
 103                                 .swizzle = SWIZZLE_XYZW,
 104                                 .unknown = 0x24,
 105                         }
 106                 };
 107
 108                 mir_insert_instruction_before(ins, accel);
 109                 mir_remove_instruction(ins);
 110
 111                 progress |= true;
 112         }
 113
 114         return progress;
 115 }