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 copy_prop_src(nir_src *src, nir_instr *parent_instr, nir_if *parent_if)
 103 {
 104    if (!src->is_ssa) {
 105       if (src->reg.indirect)
 106          return copy_prop_src(src, parent_instr, parent_if);
 107       return false;
 108    }
 109
 110    nir_instr *src_instr = src->ssa->parent_instr;
 111    if (src_instr->type != nir_instr_type_alu)
 112       return false;
 113
 114    nir_alu_instr *alu_instr = nir_instr_as_alu(src_instr);
 115    if (!is_swizzleless_move(alu_instr))
 116       return false;
 117
 118    /* Don't let copy propagation land us with a phi that has more
 119     * components in its source than it has in its destination.  That badly
 120     * messes up out-of-ssa.
 121     */
 122    if (parent_instr && parent_instr->type == nir_instr_type_phi) {
 123       nir_phi_instr *phi = nir_instr_as_phi(parent_instr);
 124       assert(phi->dest.is_ssa);
 125       if (phi->dest.ssa.num_components !=
 126           alu_instr->src[0].src.ssa->num_components)
 127          return false;
 128    }
 129
 130    if (parent_instr) {
 131       nir_instr_rewrite_src(parent_instr, src,
 132                             nir_src_for_ssa(alu_instr->src[0].src.ssa));
 133    } else {
 134       assert(src == &parent_if->condition);
 135       nir_if_rewrite_condition(parent_if,
 136                                nir_src_for_ssa(alu_instr->src[0].src.ssa));
 137    }
 138
 139    return true;
 140 }
 141
 142 static bool
 143 copy_prop_alu_src(nir_alu_instr *parent_alu_instr, unsigned index)
 144 {
 145    nir_alu_src *src = &parent_alu_instr->src[index];
 146    if (!src->src.is_ssa) {
 147       if (src->src.reg.indirect)
 148          return copy_prop_src(src->src.reg.indirect, &parent_alu_instr->instr,
 149                               NULL);
 150       return false;
 151    }
 152
 153    nir_instr *src_instr =  src->src.ssa->parent_instr;
 154    if (src_instr->type != nir_instr_type_alu)
 155       return false;
 156
 157    nir_alu_instr *alu_instr = nir_instr_as_alu(src_instr);
 158    if (!is_move(alu_instr) && !is_vec(alu_instr))
 159       return false;
 160
 161    nir_ssa_def *def;
 162    unsigned new_swizzle[4] = {0, 0, 0, 0};
 163
 164    if (alu_instr->op == nir_op_fmov ||
 165        alu_instr->op == nir_op_imov) {
 166       for (unsigned i = 0; i < 4; i++)
 167          new_swizzle[i] = alu_instr->src[0].swizzle[src->swizzle[i]];
 168       def = alu_instr->src[0].src.ssa;
 169    } else {
 170       def = NULL;
 171
 172       for (unsigned i = 0; i < 4; i++) {
 173          if (!nir_alu_instr_channel_used(parent_alu_instr, index, i))
 174             continue;
 175
 176          nir_ssa_def *new_def = alu_instr->src[src->swizzle[i]].src.ssa;
 177          if (def == NULL)
 178             def = new_def;
 179          else {
 180             if (def != new_def)
 181                return false;
 182          }
 183          new_swizzle[i] = alu_instr->src[src->swizzle[i]].swizzle[0];
 184       }
 185    }
 186
 187    for (unsigned i = 0; i < 4; i++)
 188       src->swizzle[i] = new_swizzle[i];
 189
 190    nir_instr_rewrite_src(&parent_alu_instr->instr, &src->src,
 191                          nir_src_for_ssa(def));
 192
 193    return true;
 194 }
 195
 196 typedef struct {
 197    nir_instr *parent_instr;
 198    bool progress;
 199 } copy_prop_state;
 200
 201 static bool
 202 copy_prop_src_cb(nir_src *src, void *_state)
 203 {
 204    copy_prop_state *state = (copy_prop_state *) _state;
 205    while (copy_prop_src(src, state->parent_instr, NULL))
 206       state->progress = true;
 207
 208    return true;
 209 }
 210
 211 static bool
 212 copy_prop_instr(nir_instr *instr)
 213 {
 214    if (instr->type == nir_instr_type_alu) {
 215       nir_alu_instr *alu_instr = nir_instr_as_alu(instr);
 216       bool progress = false;
 217
 218       for (unsigned i = 0; i < nir_op_infos[alu_instr->op].num_inputs; i++)
 219          while (copy_prop_alu_src(alu_instr, i))
 220             progress = true;
 221
 222       if (!alu_instr->dest.dest.is_ssa && alu_instr->dest.dest.reg.indirect)
 223          while (copy_prop_src(alu_instr->dest.dest.reg.indirect, instr, NULL))
 224             progress = true;
 225
 226       return progress;
 227    }
 228
 229    copy_prop_state state;
 230    state.parent_instr = instr;
 231    state.progress = false;
 232    nir_foreach_src(instr, copy_prop_src_cb, &state);
 233
 234    return state.progress;
 235 }
 236
 237 static bool
 238 copy_prop_if(nir_if *if_stmt)
 239 {
 240    return copy_prop_src(&if_stmt->condition, NULL, if_stmt);
 241 }
 242
 243 static bool
 244 copy_prop_block(nir_block *block, void *_state)
 245 {
 246    bool *progress = (bool *) _state;
 247
 248    nir_foreach_instr(block, instr) {
 249       if (copy_prop_instr(instr))
 250          *progress = true;
 251    }
 252
 253    if (block->cf_node.node.next != NULL && /* check that we aren't the end node */
 254        !nir_cf_node_is_last(&block->cf_node) &&
 255        nir_cf_node_next(&block->cf_node)->type == nir_cf_node_if) {
 256       nir_if *if_stmt = nir_cf_node_as_if(nir_cf_node_next(&block->cf_node));
 257       if (copy_prop_if(if_stmt))
 258          *progress = true;
 259    }
 260
 261    return true;
 262 }
 263
 264 static bool
 265 nir_copy_prop_impl(nir_function_impl *impl)
 266 {
 267    bool progress = false;
 268
 269    nir_foreach_block(impl, copy_prop_block, &progress);
 270
 271    if (progress) {
 272       nir_metadata_preserve(impl, nir_metadata_block_index |
 273                                   nir_metadata_dominance);
 274    }
 275
 276    return progress;
 277 }
 278
 279 bool
 280 nir_copy_prop(nir_shader *shader)
 281 {
 282    bool progress = false;
 283
 284    nir_foreach_function(shader, function) {
 285       if (function->impl && nir_copy_prop_impl(function->impl))
 286          progress = true;
 287    }
 288
 289    return progress;
 290 }