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