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    assert(arr_parent->child &&
  39           arr_parent->child->deref_type == nir_deref_type_array);
  40    nir_deref_array *arr = nir_deref_as_array(arr_parent->child);
  41    assert(arr->deref_array_type == nir_deref_array_type_indirect);
  42    assert(arr->indirect.is_ssa);
  43
  44    assert(start < end);
  45    if (start == end - 1) {
  46       /* Base case.  Just emit the load/store op */
  47       nir_deref_array direct = *arr;
  48       direct.deref_array_type = nir_deref_array_type_direct;
  49       direct.base_offset += start;
  50       direct.indirect = NIR_SRC_INIT;
  51
  52       arr_parent->child = &direct.deref;
  53       emit_load_store(b, orig_instr, deref, &arr->deref, dest, src);
  54       arr_parent->child = &arr->deref;
  55    } else {
  56       int mid = start + (end - start) / 2;
  57
  58       nir_ssa_def *then_dest, *else_dest;
  59
  60       nir_if *if_stmt = nir_if_create(b->shader);
  61       if_stmt->condition = nir_src_for_ssa(nir_ilt(b, arr->indirect.ssa,
  62                                                       nir_imm_int(b, mid)));
  63       nir_cf_node_insert(b->cursor, &if_stmt->cf_node);
  64
  65       b->cursor = nir_after_cf_list(&if_stmt->then_list);
  66       emit_indirect_load_store(b, orig_instr, deref, arr_parent,
  67                                start, mid, &then_dest, src);
  68
  69       b->cursor = nir_after_cf_list(&if_stmt->else_list);
  70       emit_indirect_load_store(b, orig_instr, deref, arr_parent,
  71                                mid, end, &else_dest, src);
  72
  73       b->cursor = nir_after_cf_node(&if_stmt->cf_node);
  74
  75       if (src == NULL) {
  76          /* We're a load.  We need to insert a phi node */
  77          nir_phi_instr *phi = nir_phi_instr_create(b->shader);
  78          unsigned bit_size = then_dest->bit_size;
  79          nir_ssa_dest_init(&phi->instr, &phi->dest,
  80                            then_dest->num_components, bit_size, NULL);
  81
  82          nir_phi_src *src0 = ralloc(phi, nir_phi_src);
  83          src0->pred = nir_cf_node_as_block(nir_if_last_then_node(if_stmt));
  84          src0->src = nir_src_for_ssa(then_dest);
  85          exec_list_push_tail(&phi->srcs, &src0->node);
  86
  87          nir_phi_src *src1 = ralloc(phi, nir_phi_src);
  88          src1->pred = nir_cf_node_as_block(nir_if_last_else_node(if_stmt));
  89          src1->src = nir_src_for_ssa(else_dest);
  90          exec_list_push_tail(&phi->srcs, &src1->node);
  91
  92          nir_builder_instr_insert(b, &phi->instr);
  93          *dest = &phi->dest.ssa;
  94       }
  95    }
  96 }
  97
  98 static void
  99 emit_load_store(nir_builder *b, nir_intrinsic_instr *orig_instr,
 100                 nir_deref_var *deref, nir_deref *tail,
 101                 nir_ssa_def **dest, nir_ssa_def *src)
 102 {
 103    for (; tail->child; tail = tail->child) {
 104       if (tail->child->deref_type != nir_deref_type_array)
 105          continue;
 106
 107       nir_deref_array *arr = nir_deref_as_array(tail->child);
 108       if (arr->deref_array_type != nir_deref_array_type_indirect)
 109          continue;
 110
 111       int length = glsl_get_length(tail->type);
 112
 113       emit_indirect_load_store(b, orig_instr, deref, tail, -arr->base_offset,
 114                                length - arr->base_offset, dest, src);
 115       return;
 116    }
 117
 118    assert(tail && tail->child == NULL);
 119
 120    /* We reached the end of the deref chain.  Emit the instruction */
 121
 122    if (src == NULL) {
 123       /* This is a load instruction */
 124       nir_intrinsic_instr *load =
 125          nir_intrinsic_instr_create(b->shader, nir_intrinsic_load_var);
 126       load->num_components = orig_instr->num_components;
 127       load->variables[0] =
 128          nir_deref_as_var(nir_copy_deref(load, &deref->deref));
 129       unsigned bit_size = orig_instr->dest.ssa.bit_size;
 130       nir_ssa_dest_init(&load->instr, &load->dest,
 131                         load->num_components, bit_size, NULL);
 132       nir_builder_instr_insert(b, &load->instr);
 133       *dest = &load->dest.ssa;
 134    } else {
 135       /* This is a store instruction */
 136       nir_intrinsic_instr *store =
 137          nir_intrinsic_instr_create(b->shader, nir_intrinsic_store_var);
 138       store->num_components = orig_instr->num_components;
 139       nir_intrinsic_set_write_mask(store, nir_intrinsic_write_mask(orig_instr));
 140       store->variables[0] =
 141          nir_deref_as_var(nir_copy_deref(store, &deref->deref));
 142       store->src[0] = nir_src_for_ssa(src);
 143       nir_builder_instr_insert(b, &store->instr);
 144    }
 145 }
 146
 147 static bool
 148 deref_has_indirect(nir_deref_var *deref)
 149 {
 150    for (nir_deref *tail = deref->deref.child; tail; tail = tail->child) {
 151       if (tail->deref_type != nir_deref_type_array)
 152          continue;
 153
 154       nir_deref_array *arr = nir_deref_as_array(tail);
 155       if (arr->deref_array_type == nir_deref_array_type_indirect)
 156          return true;
 157    }
 158
 159    return false;
 160 }
 161
 162 static bool
 163 lower_indirect_block(nir_block *block, nir_builder *b,
 164                      nir_variable_mode modes)
 165 {
 166    bool progress = false;
 167
 168    nir_foreach_instr_safe(instr, block) {
 169       if (instr->type != nir_instr_type_intrinsic)
 170          continue;
 171
 172       nir_intrinsic_instr *intrin = nir_instr_as_intrinsic(instr);
 173       if (intrin->intrinsic != nir_intrinsic_load_var &&
 174           intrin->intrinsic != nir_intrinsic_store_var)
 175          continue;
 176
 177       if (!deref_has_indirect(intrin->variables[0]))
 178          continue;
 179
 180       /* Only lower variables whose mode is in the mask */
 181       if (!(modes & intrin->variables[0]->var->data.mode))
 182          continue;
 183
 184       b->cursor = nir_before_instr(&intrin->instr);
 185
 186       if (intrin->intrinsic == nir_intrinsic_load_var) {
 187          nir_ssa_def *result;
 188          emit_load_store(b, intrin, intrin->variables[0],
 189                          &intrin->variables[0]->deref, &result, NULL);
 190          nir_ssa_def_rewrite_uses(&intrin->dest.ssa, nir_src_for_ssa(result));
 191       } else {
 192          assert(intrin->src[0].is_ssa);
 193          emit_load_store(b, intrin, intrin->variables[0],
 194                          &intrin->variables[0]->deref, NULL, intrin->src[0].ssa);
 195       }
 196       nir_instr_remove(&intrin->instr);
 197       progress = true;
 198    }
 199
 200    return progress;
 201 }
 202
 203 static bool
 204 lower_indirects_impl(nir_function_impl *impl, nir_variable_mode modes)
 205 {
 206    nir_builder builder;
 207    nir_builder_init(&builder, impl);
 208    bool progress = false;
 209
 210    nir_foreach_block_safe(block, impl) {
 211       progress |= lower_indirect_block(block, &builder, modes);
 212    }
 213
 214    if (progress)
 215       nir_metadata_preserve(impl, nir_metadata_none);
 216
 217    return progress;
 218 }
 219
 220 /** Lowers indirect variable loads/stores to direct loads/stores.
 221  *
 222  * The pass works by replacing any indirect load or store with an if-ladder
 223  * that does a binary search on the array index.
 224  */
 225 bool
 226 nir_lower_indirect_derefs(nir_shader *shader, nir_variable_mode modes)
 227 {
 228    bool progress = false;
 229
 230    nir_foreach_function(function, shader) {
 231       if (function->impl)
 232          progress = lower_indirects_impl(function->impl, modes) || progress;
 233    }
 234
 235    return progress;
 236 }