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
28static void
29emit_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
34static void
35emit_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
67static void
68emit_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
114static bool
115lower_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
180static bool
181lower_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 */
202bool
203nir_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}
214