src/compiler/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       /* we handle modifiers in a separate pass */
  63       if (instr->src[i].abs || instr->src[i].negate)
  64          return false;
  65    }
  66
  67    return instr->op == nir_op_vec2 ||
  68           instr->op == nir_op_vec3 ||
  69           instr->op == nir_op_vec4;
  70 }
  71
  72 static bool
  73 is_swizzleless_move(nir_alu_instr *instr)
  74 {
  75    if (is_move(instr)) {
  76       for (unsigned i = 0; i < 4; i++) {
  77          if (!((instr->dest.write_mask >> i) & 1))
  78             break;
  79          if (instr->src[0].swizzle[i] != i)
  80             return false;
  81       }
  82       return true;
  83    } else if (is_vec(instr)) {
  84       nir_ssa_def *def = NULL;
  85       for (unsigned i = 0; i < nir_op_infos[instr->op].num_inputs; i++) {
  86          if (instr->src[i].swizzle[0] != i)
  87             return false;
  88
  89          if (def == NULL) {
  90             def = instr->src[i].src.ssa;
  91          } else if (instr->src[i].src.ssa != def) {
  92             return false;
  93          }
  94       }
  95       return true;
  96    } else {
  97       return false;
  98    }
  99 }
 100
 101 static bool
 102 is_trivial_deref_cast(nir_deref_instr *cast)
 103 {
 104    if (cast->deref_type != nir_deref_type_cast)
 105       return false;
 106
 107    nir_deref_instr *parent = nir_src_as_deref(cast->parent);
 108    if (!parent)
 109       return false;
 110
 111    return cast->mode == parent->mode &&
 112           cast->type == parent->type &&
 113           cast->dest.ssa.num_components == parent->dest.ssa.num_components &&
 114           cast->dest.ssa.bit_size == parent->dest.ssa.bit_size;
 115 }
 116
 117 static bool
 118 copy_prop_src(nir_src *src, nir_instr *parent_instr, nir_if *parent_if,
 119               unsigned num_components)
 120 {
 121    if (!src->is_ssa) {
 122       if (src->reg.indirect)
 123          return copy_prop_src(src->reg.indirect, parent_instr, parent_if, 1);
 124       return false;
 125    }
 126
 127    nir_instr *src_instr = src->ssa->parent_instr;
 128    nir_ssa_def *copy_def;
 129    if (src_instr->type == nir_instr_type_alu) {
 130       nir_alu_instr *alu_instr = nir_instr_as_alu(src_instr);
 131       if (!is_swizzleless_move(alu_instr))
 132          return false;
 133
 134       if (alu_instr->src[0].src.ssa->num_components != num_components)
 135          return false;
 136
 137       copy_def= alu_instr->src[0].src.ssa;
 138    } else if (src_instr->type == nir_instr_type_deref) {
 139       nir_deref_instr *deref_instr = nir_instr_as_deref(src_instr);
 140       if (!is_trivial_deref_cast(deref_instr))
 141          return false;
 142
 143       copy_def = deref_instr->parent.ssa;
 144    } else {
 145       return false;
 146    }
 147
 148    if (parent_instr) {
 149       nir_instr_rewrite_src(parent_instr, src, nir_src_for_ssa(copy_def));
 150    } else {
 151       assert(src == &parent_if->condition);
 152       nir_if_rewrite_condition(parent_if, nir_src_for_ssa(copy_def));
 153    }
 154
 155    return true;
 156 }
 157
 158 static bool
 159 copy_prop_alu_src(nir_alu_instr *parent_alu_instr, unsigned index)
 160 {
 161    nir_alu_src *src = &parent_alu_instr->src[index];
 162    if (!src->src.is_ssa) {
 163       if (src->src.reg.indirect)
 164          return copy_prop_src(src->src.reg.indirect, &parent_alu_instr->instr,
 165                               NULL, 1);
 166       return false;
 167    }
 168
 169    nir_instr *src_instr =  src->src.ssa->parent_instr;
 170    if (src_instr->type != nir_instr_type_alu)
 171       return false;
 172
 173    nir_alu_instr *alu_instr = nir_instr_as_alu(src_instr);
 174    if (!is_move(alu_instr) && !is_vec(alu_instr))
 175       return false;
 176
 177    nir_ssa_def *def;
 178    unsigned new_swizzle[4] = {0, 0, 0, 0};
 179
 180    if (alu_instr->op == nir_op_fmov ||
 181        alu_instr->op == nir_op_imov) {
 182       for (unsigned i = 0; i < 4; i++)
 183          new_swizzle[i] = alu_instr->src[0].swizzle[src->swizzle[i]];
 184       def = alu_instr->src[0].src.ssa;
 185    } else {
 186       def = NULL;
 187
 188       for (unsigned i = 0; i < 4; i++) {
 189          if (!nir_alu_instr_channel_used(parent_alu_instr, index, i))
 190             continue;
 191
 192          nir_ssa_def *new_def = alu_instr->src[src->swizzle[i]].src.ssa;
 193          if (def == NULL)
 194             def = new_def;
 195          else {
 196             if (def != new_def)
 197                return false;
 198          }
 199          new_swizzle[i] = alu_instr->src[src->swizzle[i]].swizzle[0];
 200       }
 201    }
 202
 203    for (unsigned i = 0; i < 4; i++)
 204       src->swizzle[i] = new_swizzle[i];
 205
 206    nir_instr_rewrite_src(&parent_alu_instr->instr, &src->src,
 207                          nir_src_for_ssa(def));
 208
 209    return true;
 210 }
 211
 212 static bool
 213 copy_prop_dest(nir_dest *dest, nir_instr *instr)
 214 {
 215    if (!dest->is_ssa && dest->reg.indirect)
 216       return copy_prop_src(dest->reg.indirect, instr, NULL, 1);
 217
 218    return false;
 219 }
 220
 221 static bool
 222 copy_prop_instr(nir_instr *instr)
 223 {
 224    bool progress = false;
 225    switch (instr->type) {
 226    case nir_instr_type_alu: {
 227       nir_alu_instr *alu_instr = nir_instr_as_alu(instr);
 228
 229       for (unsigned i = 0; i < nir_op_infos[alu_instr->op].num_inputs; i++)
 230          while (copy_prop_alu_src(alu_instr, i))
 231             progress = true;
 232
 233       while (copy_prop_dest(&alu_instr->dest.dest, instr))
 234          progress = true;
 235
 236       return progress;
 237    }
 238
 239    case nir_instr_type_deref: {
 240       nir_deref_instr *deref = nir_instr_as_deref(instr);
 241
 242       if (deref->deref_type != nir_deref_type_var) {
 243          assert(deref->dest.is_ssa);
 244          const unsigned comps = deref->dest.ssa.num_components;
 245          while (copy_prop_src(&deref->parent, instr, NULL, comps))
 246             progress = true;
 247       }
 248
 249       if (deref->deref_type == nir_deref_type_array) {
 250          while (copy_prop_src(&deref->arr.index, instr, NULL, 1))
 251             progress = true;
 252       }
 253
 254       return progress;
 255    }
 256
 257    case nir_instr_type_tex: {
 258       nir_tex_instr *tex = nir_instr_as_tex(instr);
 259       for (unsigned i = 0; i < tex->num_srcs; i++) {
 260          unsigned num_components = nir_tex_instr_src_size(tex, i);
 261          while (copy_prop_src(&tex->src[i].src, instr, NULL, num_components))
 262             progress = true;
 263       }
 264
 265       while (copy_prop_dest(&tex->dest, instr))
 266          progress = true;
 267
 268       return progress;
 269    }
 270
 271    case nir_instr_type_intrinsic: {
 272       nir_intrinsic_instr *intrin = nir_instr_as_intrinsic(instr);
 273       for (unsigned i = 0;
 274            i < nir_intrinsic_infos[intrin->intrinsic].num_srcs; i++) {
 275          unsigned num_components = nir_intrinsic_src_components(intrin, i);
 276
 277          while (copy_prop_src(&intrin->src[i], instr, NULL, num_components))
 278             progress = true;
 279       }
 280
 281       if (nir_intrinsic_infos[intrin->intrinsic].has_dest) {
 282          while (copy_prop_dest(&intrin->dest, instr))
 283             progress = true;
 284       }
 285
 286       return progress;
 287    }
 288
 289    case nir_instr_type_phi: {
 290       nir_phi_instr *phi = nir_instr_as_phi(instr);
 291       assert(phi->dest.is_ssa);
 292       unsigned num_components = phi->dest.ssa.num_components;
 293       nir_foreach_phi_src(src, phi) {
 294          while (copy_prop_src(&src->src, instr, NULL, num_components))
 295             progress = true;
 296       }
 297
 298       return progress;
 299    }
 300
 301    default:
 302       return false;
 303    }
 304 }
 305
 306 static bool
 307 copy_prop_if(nir_if *if_stmt)
 308 {
 309    return copy_prop_src(&if_stmt->condition, NULL, if_stmt, 1);
 310 }
 311
 312 static bool
 313 nir_copy_prop_impl(nir_function_impl *impl)
 314 {
 315    bool progress = false;
 316
 317    nir_foreach_block(block, impl) {
 318       nir_foreach_instr(instr, block) {
 319          if (copy_prop_instr(instr))
 320             progress = true;
 321       }
 322
 323       nir_if *if_stmt = nir_block_get_following_if(block);
 324       if (if_stmt && copy_prop_if(if_stmt))
 325          progress = true;
 326       }
 327
 328    if (progress) {
 329       nir_metadata_preserve(impl, nir_metadata_block_index |
 330                                   nir_metadata_dominance);
 331    }
 332
 333    return progress;
 334 }
 335
 336 bool
 337 nir_copy_prop(nir_shader *shader)
 338 {
 339    bool progress = false;
 340
 341    nir_foreach_function(function, shader) {
 342       if (function->impl && nir_copy_prop_impl(function->impl))
 343          progress = true;
 344    }
 345
 346    return progress;
 347 }