src/compiler/nir/nir_propagate_invariant.c

   1 /*
   2  * Copyright © 2016 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
  21  * DEALINGS IN THE SOFTWARE.
  22  */
  23
  24 #include "nir.h"
  25
  26 static void
  27 add_src(nir_src *src, struct set *invariants)
  28 {
  29    if (src->is_ssa) {
  30       _mesa_set_add(invariants, src->ssa);
  31    } else {
  32       _mesa_set_add(invariants, src->reg.reg);
  33    }
  34 }
  35
  36 static bool
  37 add_src_cb(nir_src *src, void *state)
  38 {
  39    add_src(src, state);
  40    return true;
  41 }
  42
  43 static bool
  44 dest_is_invariant(nir_dest *dest, struct set *invariants)
  45 {
  46    if (dest->is_ssa) {
  47       return _mesa_set_search(invariants, &dest->ssa);
  48    } else {
  49       return _mesa_set_search(invariants, dest->reg.reg);
  50    }
  51 }
  52
  53 static void
  54 add_cf_node(nir_cf_node *cf, struct set *invariants)
  55 {
  56    if (cf->type == nir_cf_node_if) {
  57       nir_if *if_stmt = nir_cf_node_as_if(cf);
  58       add_src(&if_stmt->condition, invariants);
  59    }
  60
  61    if (cf->parent)
  62       add_cf_node(cf->parent, invariants);
  63 }
  64
  65 static void
  66 add_var(nir_variable *var, struct set *invariants)
  67 {
  68    _mesa_set_add(invariants, var);
  69 }
  70
  71 static bool
  72 var_is_invariant(nir_variable *var, struct set * invariants)
  73 {
  74    return var->data.invariant || _mesa_set_search(invariants, var);
  75 }
  76
  77 static nir_variable *
  78 intrinsic_get_var(nir_intrinsic_instr *intrin, unsigned i)
  79 {
  80    return nir_deref_instr_get_variable(nir_src_as_deref(intrin->src[i]));
  81 }
  82
  83 static void
  84 propagate_invariant_instr(nir_instr *instr, struct set *invariants)
  85 {
  86    switch (instr->type) {
  87    case nir_instr_type_alu: {
  88       nir_alu_instr *alu = nir_instr_as_alu(instr);
  89       if (!dest_is_invariant(&alu->dest.dest, invariants))
  90          break;
  91
  92       alu->exact = true;
  93       nir_foreach_src(instr, add_src_cb, invariants);
  94       break;
  95    }
  96
  97    case nir_instr_type_tex: {
  98       nir_tex_instr *tex = nir_instr_as_tex(instr);
  99       if (dest_is_invariant(&tex->dest, invariants))
 100          nir_foreach_src(instr, add_src_cb, invariants);
 101       break;
 102    }
 103
 104    case nir_instr_type_intrinsic: {
 105       nir_intrinsic_instr *intrin = nir_instr_as_intrinsic(instr);
 106       switch (intrin->intrinsic) {
 107       case nir_intrinsic_copy_deref:
 108          /* If the destination is invariant then so is the source */
 109          if (var_is_invariant(intrinsic_get_var(intrin, 0), invariants))
 110             add_var(intrinsic_get_var(intrin, 1), invariants);
 111          break;
 112
 113       case nir_intrinsic_load_deref:
 114          if (dest_is_invariant(&intrin->dest, invariants))
 115             add_var(intrinsic_get_var(intrin, 0), invariants);
 116          break;
 117
 118       case nir_intrinsic_store_deref:
 119          if (var_is_invariant(intrinsic_get_var(intrin, 0), invariants))
 120             add_src(&intrin->src[1], invariants);
 121          break;
 122
 123       default:
 124          /* Nothing to do */
 125          break;
 126       }
 127    }
 128
 129    case nir_instr_type_deref:
 130    case nir_instr_type_jump:
 131    case nir_instr_type_ssa_undef:
 132    case nir_instr_type_load_const:
 133       break; /* Nothing to do */
 134
 135    case nir_instr_type_phi: {
 136       nir_phi_instr *phi = nir_instr_as_phi(instr);
 137       if (!dest_is_invariant(&phi->dest, invariants))
 138          break;
 139
 140       nir_foreach_phi_src(src, phi) {
 141          add_src(&src->src, invariants);
 142          add_cf_node(&src->pred->cf_node, invariants);
 143       }
 144       break;
 145    }
 146
 147    case nir_instr_type_call:
 148       unreachable("This pass must be run after function inlining");
 149
 150    case nir_instr_type_parallel_copy:
 151    default:
 152       unreachable("Cannot have this instruction type");
 153    }
 154 }
 155
 156 static bool
 157 propagate_invariant_impl(nir_function_impl *impl, struct set *invariants)
 158 {
 159    bool progress = false;
 160
 161    while (true) {
 162       uint32_t prev_entries = invariants->entries;
 163
 164       nir_foreach_block_reverse(block, impl) {
 165          nir_foreach_instr_reverse(instr, block)
 166             propagate_invariant_instr(instr, invariants);
 167       }
 168
 169       /* Keep running until we make no more progress. */
 170       if (invariants->entries > prev_entries) {
 171          progress = true;
 172          continue;
 173       } else {
 174          break;
 175       }
 176    }
 177
 178    if (progress) {
 179       nir_metadata_preserve(impl, nir_metadata_block_index |
 180                                   nir_metadata_dominance |
 181                                   nir_metadata_live_ssa_defs);
 182    }
 183
 184    return progress;
 185 }
 186
 187 bool
 188 nir_propagate_invariant(nir_shader *shader)
 189 {
 190    /* Hash set of invariant things */
 191    struct set *invariants = _mesa_set_create(NULL, _mesa_hash_pointer,
 192                                              _mesa_key_pointer_equal);
 193
 194    nir_assert_unlowered_derefs(shader, nir_lower_load_store_derefs);
 195
 196    bool progress = false;
 197    nir_foreach_function(function, shader) {
 198       if (function->impl && propagate_invariant_impl(function->impl, invariants))
 199          progress = true;
 200    }
 201
 202    _mesa_set_destroy(invariants, NULL);
 203
 204    return progress;
 205 }