src/glsl/nir/nir_opt_copy_propagate.c

   1 /*
   2  * Copyright © 2014 Intel Corporation
   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  * Authors:
  24  *    Connor Abbott (cwabbott0@gmail.com)
  25  *
  26  */
  27
  28 #include "nir.h"
  29 #include <main/imports.h>
  30
  31 /**
  32  * SSA-based copy propagation
  33  */
  34
  35 static bool is_move(nir_alu_instr *instr)
  36 {
  37    if (instr->op != nir_op_fmov &&
  38        instr->op != nir_op_imov)
  39       return false;
  40
  41    if (instr->dest.saturate)
  42       return false;
  43
  44    /* we handle modifiers in a separate pass */
  45
  46    if (instr->src[0].abs || instr->src[0].negate)
  47       return false;
  48
  49    if (!instr->src[0].src.is_ssa)
  50       return false;
  51
  52    return true;
  53
  54 }
  55
  56 static bool is_vec(nir_alu_instr *instr)
  57 {
  58    for (unsigned i = 0; i < nir_op_infos[instr->op].num_inputs; i++)
  59       if (!instr->src[i].src.is_ssa)
  60          return false;
  61
  62    return instr->op == nir_op_vec2 ||
  63           instr->op == nir_op_vec3 ||
  64           instr->op == nir_op_vec4;
  65 }
  66
  67 static bool
  68 is_swizzleless_move(nir_alu_instr *instr)
  69 {
  70    if (is_move(instr)) {
  71       for (unsigned i = 0; i < 4; i++) {
  72          if (!((instr->dest.write_mask >> i) & 1))
  73             break;
  74          if (instr->src[0].swizzle[i] != i)
  75             return false;
  76       }
  77       return true;
  78    } else if (is_vec(instr)) {
  79       nir_ssa_def *def = NULL;
  80       for (unsigned i = 0; i < nir_op_infos[instr->op].num_inputs; i++) {
  81          if (instr->src[i].swizzle[0] != i)
  82             return false;
  83
  84          if (def == NULL) {
  85             def = instr->src[i].src.ssa;
  86          } else if (instr->src[i].src.ssa != def) {
  87             return false;
  88          }
  89       }
  90       return true;
  91    } else {
  92       return false;
  93    }
  94 }
  95
  96 static bool
  97 copy_prop_src(nir_src *src, nir_instr *parent_instr, nir_if *parent_if)
  98 {
  99    if (!src->is_ssa) {
 100       if (src->reg.indirect)
 101          return copy_prop_src(src, parent_instr, parent_if);
 102       return false;
 103    }
 104
 105    nir_instr *src_instr = src->ssa->parent_instr;
 106    if (src_instr->type != nir_instr_type_alu)
 107       return false;
 108
 109    nir_alu_instr *alu_instr = nir_instr_as_alu(src_instr);
 110    if (!is_swizzleless_move(alu_instr))
 111       return false;
 112
 113    /* Don't let copy propagation land us with a phi that has more
 114     * components in its source than it has in its destination.  That badly
 115     * messes up out-of-ssa.
 116     */
 117    if (parent_instr && parent_instr->type == nir_instr_type_phi) {
 118       nir_phi_instr *phi = nir_instr_as_phi(parent_instr);
 119       assert(phi->dest.is_ssa);
 120       if (phi->dest.ssa.num_components !=
 121           alu_instr->src[0].src.ssa->num_components)
 122          return false;
 123    }
 124
 125    if (parent_instr) {
 126       nir_instr_rewrite_src(parent_instr, src,
 127                             nir_src_for_ssa(alu_instr->src[0].src.ssa));
 128    } else {
 129       assert(src == &parent_if->condition);
 130       nir_if_rewrite_condition(parent_if,
 131                                nir_src_for_ssa(alu_instr->src[0].src.ssa));
 132    }
 133
 134    return true;
 135 }
 136
 137 static bool
 138 copy_prop_alu_src(nir_alu_instr *parent_alu_instr, unsigned index)
 139 {
 140    nir_alu_src *src = &parent_alu_instr->src[index];
 141    if (!src->src.is_ssa) {
 142       if (src->src.reg.indirect)
 143          return copy_prop_src(src->src.reg.indirect, &parent_alu_instr->instr,
 144                               NULL);
 145       return false;
 146    }
 147
 148    nir_instr *src_instr =  src->src.ssa->parent_instr;
 149    if (src_instr->type != nir_instr_type_alu)
 150       return false;
 151
 152    nir_alu_instr *alu_instr = nir_instr_as_alu(src_instr);
 153    if (!is_move(alu_instr) && !is_vec(alu_instr))
 154       return false;
 155
 156    nir_ssa_def *def;
 157    unsigned new_swizzle[4] = {0, 0, 0, 0};
 158
 159    if (alu_instr->op == nir_op_fmov ||
 160        alu_instr->op == nir_op_imov) {
 161       for (unsigned i = 0; i < 4; i++)
 162          new_swizzle[i] = alu_instr->src[0].swizzle[src->swizzle[i]];
 163       def = alu_instr->src[0].src.ssa;
 164    } else {
 165       def = NULL;
 166
 167       for (unsigned i = 0; i < 4; i++) {
 168          if (!nir_alu_instr_channel_used(parent_alu_instr, index, i))
 169             continue;
 170
 171          nir_ssa_def *new_def = alu_instr->src[src->swizzle[i]].src.ssa;
 172          if (def == NULL)
 173             def = new_def;
 174          else {
 175             if (def != new_def)
 176                return false;
 177          }
 178          new_swizzle[i] = alu_instr->src[src->swizzle[i]].swizzle[0];
 179       }
 180    }
 181
 182    for (unsigned i = 0; i < 4; i++)
 183       src->swizzle[i] = new_swizzle[i];
 184
 185    nir_instr_rewrite_src(&parent_alu_instr->instr, &src->src,
 186                          nir_src_for_ssa(def));
 187
 188    return true;
 189 }
 190
 191 typedef struct {
 192    nir_instr *parent_instr;
 193    bool progress;
 194 } copy_prop_state;
 195
 196 static bool
 197 copy_prop_src_cb(nir_src *src, void *_state)
 198 {
 199    copy_prop_state *state = (copy_prop_state *) _state;
 200    while (copy_prop_src(src, state->parent_instr, NULL))
 201       state->progress = true;
 202
 203    return true;
 204 }
 205
 206 static bool
 207 copy_prop_instr(nir_instr *instr)
 208 {
 209    if (instr->type == nir_instr_type_alu) {
 210       nir_alu_instr *alu_instr = nir_instr_as_alu(instr);
 211       bool progress = false;
 212
 213       for (unsigned i = 0; i < nir_op_infos[alu_instr->op].num_inputs; i++)
 214          while (copy_prop_alu_src(alu_instr, i))
 215             progress = true;
 216
 217       if (!alu_instr->dest.dest.is_ssa && alu_instr->dest.dest.reg.indirect)
 218          while (copy_prop_src(alu_instr->dest.dest.reg.indirect, instr, NULL))
 219             progress = true;
 220
 221       return progress;
 222    }
 223
 224    copy_prop_state state;
 225    state.parent_instr = instr;
 226    state.progress = false;
 227    nir_foreach_src(instr, copy_prop_src_cb, &state);
 228
 229    return state.progress;
 230 }
 231
 232 static bool
 233 copy_prop_if(nir_if *if_stmt)
 234 {
 235    return copy_prop_src(&if_stmt->condition, NULL, if_stmt);
 236 }
 237
 238 static bool
 239 copy_prop_block(nir_block *block, void *_state)
 240 {
 241    bool *progress = (bool *) _state;
 242
 243    nir_foreach_instr(block, instr) {
 244       if (copy_prop_instr(instr))
 245          *progress = true;
 246    }
 247
 248    if (block->cf_node.node.next != NULL && /* check that we aren't the end node */
 249        !nir_cf_node_is_last(&block->cf_node) &&
 250        nir_cf_node_next(&block->cf_node)->type == nir_cf_node_if) {
 251       nir_if *if_stmt = nir_cf_node_as_if(nir_cf_node_next(&block->cf_node));
 252       if (copy_prop_if(if_stmt))
 253          *progress = true;
 254    }
 255
 256    return true;
 257 }
 258
 259 bool
 260 nir_copy_prop_impl(nir_function_impl *impl)
 261 {
 262    bool progress = false;
 263
 264    nir_foreach_block(impl, copy_prop_block, &progress);
 265    return progress;
 266 }
 267
 268 bool
 269 nir_copy_prop(nir_shader *shader)
 270 {
 271    bool progress = false;
 272
 273    nir_foreach_overload(shader, overload) {
 274       if (overload->impl && nir_copy_prop_impl(overload->impl))
 275          progress = true;
 276    }
 277
 278    return progress;
 279 }