src/compiler/nir/nir_lower_indirect_derefs.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 DEALINGS
  21  * IN THE SOFTWARE.
  22  */
  23
  24 #include "nir.h"
  25 #include "nir_builder.h"
  26
  27 static void
  28 emit_load_store(nir_builder *b, nir_intrinsic_instr *orig_instr,
  29                 nir_deref_var *deref, nir_deref *tail,
  30                 nir_ssa_def **dest, nir_ssa_def *src);
  31
  32 static void
  33 emit_indirect_load_store(nir_builder *b, nir_intrinsic_instr *orig_instr,
  34                          nir_deref_var *deref, nir_deref *arr_parent,
  35                          int start, int end,
  36                          nir_ssa_def **dest, nir_ssa_def *src)
  37 {
  38    nir_deref_array *arr = nir_deref_as_array(arr_parent->child);
  39    assert(arr->deref_array_type == nir_deref_array_type_indirect);
  40    assert(arr->indirect.is_ssa);
  41
  42    assert(start < end);
  43    if (start == end - 1) {
  44       /* Base case.  Just emit the load/store op */
  45       nir_deref_array direct = *arr;
  46       direct.deref_array_type = nir_deref_array_type_direct;
  47       direct.base_offset += start;
  48       direct.indirect = NIR_SRC_INIT;
  49
  50       arr_parent->child = &direct.deref;
  51       emit_load_store(b, orig_instr, deref, &direct.deref, dest, src);
  52       arr_parent->child = &arr->deref;
  53    } else {
  54       int mid = start + (end - start) / 2;
  55
  56       nir_ssa_def *then_dest, *else_dest;
  57
  58       nir_push_if(b, nir_ilt(b, arr->indirect.ssa, nir_imm_int(b, mid)));
  59       emit_indirect_load_store(b, orig_instr, deref, arr_parent,
  60                                start, mid, &then_dest, src);
  61       nir_push_else(b, NULL);
  62       emit_indirect_load_store(b, orig_instr, deref, arr_parent,
  63                                mid, end, &else_dest, src);
  64       nir_pop_if(b, NULL);
  65
  66       if (src == NULL)
  67          *dest = nir_if_phi(b, then_dest, else_dest);
  68    }
  69 }
  70
  71 static void
  72 emit_load_store(nir_builder *b, nir_intrinsic_instr *orig_instr,
  73                 nir_deref_var *deref, nir_deref *tail,
  74                 nir_ssa_def **dest, nir_ssa_def *src)
  75 {
  76    for (; tail->child; tail = tail->child) {
  77       if (tail->child->deref_type != nir_deref_type_array)
  78          continue;
  79
  80       nir_deref_array *arr = nir_deref_as_array(tail->child);
  81       if (arr->deref_array_type != nir_deref_array_type_indirect)
  82          continue;
  83
  84       int length = glsl_get_length(tail->type);
  85
  86       emit_indirect_load_store(b, orig_instr, deref, tail, -arr->base_offset,
  87                                length - arr->base_offset, dest, src);
  88       return;
  89    }
  90
  91    assert(tail && tail->child == NULL);
  92
  93    /* We reached the end of the deref chain.  Emit the instruction */
  94
  95    if (src == NULL) {
  96       /* This is a load instruction */
  97       nir_intrinsic_instr *load =
  98          nir_intrinsic_instr_create(b->shader, orig_instr->intrinsic);
  99       load->num_components = orig_instr->num_components;
 100       load->variables[0] = nir_deref_var_clone(deref, load);
 101
 102       /* Copy over any sources.  This is needed for interp_var_at */
 103       for (unsigned i = 0;
 104            i < nir_intrinsic_infos[orig_instr->intrinsic].num_srcs; i++)
 105          nir_src_copy(&load->src[i], &orig_instr->src[i], load);
 106
 107       unsigned bit_size = orig_instr->dest.ssa.bit_size;
 108       nir_ssa_dest_init(&load->instr, &load->dest,
 109                         load->num_components, bit_size, NULL);
 110       nir_builder_instr_insert(b, &load->instr);
 111       *dest = &load->dest.ssa;
 112    } else {
 113       /* This is a store instruction */
 114       nir_intrinsic_instr *store =
 115          nir_intrinsic_instr_create(b->shader, nir_intrinsic_store_var);
 116       store->num_components = orig_instr->num_components;
 117       nir_intrinsic_set_write_mask(store, nir_intrinsic_write_mask(orig_instr));
 118       store->variables[0] = nir_deref_var_clone(deref, store);
 119       store->src[0] = nir_src_for_ssa(src);
 120       nir_builder_instr_insert(b, &store->instr);
 121    }
 122 }
 123
 124 static bool
 125 deref_has_indirect(nir_deref_var *deref)
 126 {
 127    for (nir_deref *tail = deref->deref.child; tail; tail = tail->child) {
 128       if (tail->deref_type != nir_deref_type_array)
 129          continue;
 130
 131       nir_deref_array *arr = nir_deref_as_array(tail);
 132       if (arr->deref_array_type == nir_deref_array_type_indirect)
 133          return true;
 134    }
 135
 136    return false;
 137 }
 138
 139 static bool
 140 lower_indirect_block(nir_block *block, nir_builder *b,
 141                      nir_variable_mode modes)
 142 {
 143    bool progress = false;
 144
 145    nir_foreach_instr_safe(instr, block) {
 146       if (instr->type != nir_instr_type_intrinsic)
 147          continue;
 148
 149       nir_intrinsic_instr *intrin = nir_instr_as_intrinsic(instr);
 150       if (intrin->intrinsic != nir_intrinsic_load_var &&
 151           intrin->intrinsic != nir_intrinsic_interp_var_at_centroid &&
 152           intrin->intrinsic != nir_intrinsic_interp_var_at_sample &&
 153           intrin->intrinsic != nir_intrinsic_interp_var_at_offset &&
 154           intrin->intrinsic != nir_intrinsic_store_var)
 155          continue;
 156
 157       if (!deref_has_indirect(intrin->variables[0]))
 158          continue;
 159
 160       /* Only lower variables whose mode is in the mask, or compact
 161        * array variables.  (We can't handle indirects on tightly packed
 162        * scalar arrays, so we need to lower them regardless.)
 163        */
 164       if (!(modes & intrin->variables[0]->var->data.mode) &&
 165           !intrin->variables[0]->var->data.compact)
 166          continue;
 167
 168       b->cursor = nir_before_instr(&intrin->instr);
 169
 170       if (intrin->intrinsic != nir_intrinsic_store_var) {
 171          nir_ssa_def *result;
 172          emit_load_store(b, intrin, intrin->variables[0],
 173                          &intrin->variables[0]->deref, &result, NULL);
 174          nir_ssa_def_rewrite_uses(&intrin->dest.ssa, nir_src_for_ssa(result));
 175       } else {
 176          assert(intrin->src[0].is_ssa);
 177          emit_load_store(b, intrin, intrin->variables[0],
 178                          &intrin->variables[0]->deref, NULL, intrin->src[0].ssa);
 179       }
 180       nir_instr_remove(&intrin->instr);
 181       progress = true;
 182    }
 183
 184    return progress;
 185 }
 186
 187 static bool
 188 lower_indirects_impl(nir_function_impl *impl, nir_variable_mode modes)
 189 {
 190    nir_builder builder;
 191    nir_builder_init(&builder, impl);
 192    bool progress = false;
 193
 194    nir_foreach_block_safe(block, impl) {
 195       progress |= lower_indirect_block(block, &builder, modes);
 196    }
 197
 198    if (progress)
 199       nir_metadata_preserve(impl, nir_metadata_none);
 200
 201    return progress;
 202 }
 203
 204 /** Lowers indirect variable loads/stores to direct loads/stores.
 205  *
 206  * The pass works by replacing any indirect load or store with an if-ladder
 207  * that does a binary search on the array index.
 208  */
 209 bool
 210 nir_lower_indirect_derefs(nir_shader *shader, nir_variable_mode modes)
 211 {
 212    bool progress = false;
 213
 214    nir_foreach_function(function, shader) {
 215       if (function->impl)
 216          progress = lower_indirects_impl(function->impl, modes) || progress;
 217    }
 218
 219    return progress;
 220 }