1 /*
2  * Copyright © 2014 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  * Authors:
24  *    Jason Ekstrand (jason@jlekstrand.net)
25  *
26  */
27 
28 #include "nir.h"
29 #include "nir_builder.h"
30 
31 struct locals_to_regs_state {
32    nir_builder builder;
33 
34    /* A hash table mapping derefs to registers */
35    struct hash_table *regs_table;
36 
37    bool progress;
38 };
39 
40 /* The following two functions implement a hash and equality check for
41  * variable dreferences.  When the hash or equality function encounters an
42  * array, it ignores the offset and whether it is direct or indirect
43  * entirely.
44  */
45 static uint32_t
hash_deref(const void * void_deref)46 hash_deref(const void *void_deref)
47 {
48    uint32_t hash = 0;
49 
50    for (const nir_deref_instr *deref = void_deref; deref;
51         deref = nir_deref_instr_parent(deref)) {
52       switch (deref->deref_type) {
53       case nir_deref_type_var:
54          return XXH32(&deref->var, sizeof(deref->var), hash);
55 
56       case nir_deref_type_array:
57          continue; /* Do nothing */
58 
59       case nir_deref_type_struct:
60          hash = XXH32(&deref->strct.index, sizeof(deref->strct.index), hash);
61          continue;
62 
63       default:
64          unreachable("Invalid deref type");
65       }
66    }
67 
68    unreachable("We should have hit a variable dereference");
69 }
70 
71 static bool
derefs_equal(const void * void_a,const void * void_b)72 derefs_equal(const void *void_a, const void *void_b)
73 {
74    for (const nir_deref_instr *a = void_a, *b = void_b; a || b;
75         a = nir_deref_instr_parent(a), b = nir_deref_instr_parent(b)) {
76       if (a->deref_type != b->deref_type)
77          return false;
78 
79       switch (a->deref_type) {
80       case nir_deref_type_var:
81          return a->var == b->var;
82 
83       case nir_deref_type_array:
84          continue; /* Do nothing */
85 
86       case nir_deref_type_struct:
87          if (a->strct.index != b->strct.index)
88             return false;
89          continue;
90 
91       default:
92          unreachable("Invalid deref type");
93       }
94    }
95 
96    unreachable("We should have hit a variable dereference");
97 }
98 
99 static nir_register *
get_reg_for_deref(nir_deref_instr * deref,struct locals_to_regs_state * state)100 get_reg_for_deref(nir_deref_instr *deref, struct locals_to_regs_state *state)
101 {
102    uint32_t hash = hash_deref(deref);
103 
104    assert(nir_deref_instr_get_variable(deref)->constant_initializer == NULL &&
105           nir_deref_instr_get_variable(deref)->pointer_initializer == NULL);
106 
107    struct hash_entry *entry =
108       _mesa_hash_table_search_pre_hashed(state->regs_table, hash, deref);
109    if (entry)
110       return entry->data;
111 
112    unsigned array_size = 1;
113    for (nir_deref_instr *d = deref; d; d = nir_deref_instr_parent(d)) {
114       if (d->deref_type == nir_deref_type_array)
115          array_size *= glsl_get_length(nir_deref_instr_parent(d)->type);
116    }
117 
118    assert(glsl_type_is_vector_or_scalar(deref->type));
119 
120    nir_register *reg = nir_local_reg_create(state->builder.impl);
121    reg->num_components = glsl_get_vector_elements(deref->type);
122    reg->num_array_elems = array_size > 1 ? array_size : 0;
123    reg->bit_size = glsl_get_bit_size(deref->type);
124 
125    _mesa_hash_table_insert_pre_hashed(state->regs_table, hash, deref, reg);
126 
127    return reg;
128 }
129 
130 static nir_src
get_deref_reg_src(nir_deref_instr * deref,struct locals_to_regs_state * state)131 get_deref_reg_src(nir_deref_instr *deref, struct locals_to_regs_state *state)
132 {
133    nir_builder *b = &state->builder;
134 
135    nir_src src;
136 
137    src.is_ssa = false;
138    src.reg.reg = get_reg_for_deref(deref, state);
139    src.reg.base_offset = 0;
140    src.reg.indirect = NULL;
141 
142    /* It is possible for a user to create a shader that has an array with a
143     * single element and then proceed to access it indirectly.  Indirectly
144     * accessing a non-array register is not allowed in NIR.  In order to
145     * handle this case we just convert it to a direct reference.
146     */
147    if (src.reg.reg->num_array_elems == 0)
148       return src;
149 
150    unsigned inner_array_size = 1;
151    for (const nir_deref_instr *d = deref; d; d = nir_deref_instr_parent(d)) {
152       if (d->deref_type != nir_deref_type_array)
153          continue;
154 
155       if (nir_src_is_const(d->arr.index) && !src.reg.indirect) {
156          src.reg.base_offset += nir_src_as_uint(d->arr.index) *
157                                 inner_array_size;
158       } else {
159          if (src.reg.indirect) {
160             assert(src.reg.base_offset == 0);
161          } else {
162             src.reg.indirect = ralloc(b->shader, nir_src);
163             *src.reg.indirect =
164                nir_src_for_ssa(nir_imm_int(b, src.reg.base_offset));
165             src.reg.base_offset = 0;
166          }
167 
168          assert(src.reg.indirect->is_ssa);
169          nir_ssa_def *index = nir_i2i(b, nir_ssa_for_src(b, d->arr.index, 1), 32);
170          src.reg.indirect->ssa =
171             nir_iadd(b, src.reg.indirect->ssa,
172                         nir_imul(b, index, nir_imm_int(b, inner_array_size)));
173       }
174 
175       inner_array_size *= glsl_get_length(nir_deref_instr_parent(d)->type);
176    }
177 
178    return src;
179 }
180 
181 static bool
lower_locals_to_regs_block(nir_block * block,struct locals_to_regs_state * state)182 lower_locals_to_regs_block(nir_block *block,
183                            struct locals_to_regs_state *state)
184 {
185    nir_builder *b = &state->builder;
186 
187    nir_foreach_instr_safe(instr, block) {
188       if (instr->type != nir_instr_type_intrinsic)
189          continue;
190 
191       nir_intrinsic_instr *intrin = nir_instr_as_intrinsic(instr);
192 
193       switch (intrin->intrinsic) {
194       case nir_intrinsic_load_deref: {
195          nir_deref_instr *deref = nir_src_as_deref(intrin->src[0]);
196          if (!nir_deref_mode_is(deref, nir_var_function_temp))
197             continue;
198 
199          b->cursor = nir_before_instr(&intrin->instr);
200 
201          nir_alu_instr *mov = nir_alu_instr_create(b->shader, nir_op_mov);
202          mov->src[0].src = get_deref_reg_src(deref, state);
203          mov->dest.write_mask = (1 << intrin->num_components) - 1;
204          if (intrin->dest.is_ssa) {
205             nir_ssa_dest_init(&mov->instr, &mov->dest.dest,
206                               intrin->num_components,
207                               intrin->dest.ssa.bit_size, NULL);
208             nir_ssa_def_rewrite_uses(&intrin->dest.ssa,
209                                      nir_src_for_ssa(&mov->dest.dest.ssa));
210          } else {
211             nir_dest_copy(&mov->dest.dest, &intrin->dest, &mov->instr);
212          }
213          nir_builder_instr_insert(b, &mov->instr);
214 
215          nir_instr_remove(&intrin->instr);
216          state->progress = true;
217          break;
218       }
219 
220       case nir_intrinsic_store_deref: {
221          nir_deref_instr *deref = nir_src_as_deref(intrin->src[0]);
222          if (!nir_deref_mode_is(deref, nir_var_function_temp))
223             continue;
224 
225          b->cursor = nir_before_instr(&intrin->instr);
226 
227          nir_src reg_src = get_deref_reg_src(deref, state);
228 
229          nir_alu_instr *mov = nir_alu_instr_create(b->shader, nir_op_mov);
230          nir_src_copy(&mov->src[0].src, &intrin->src[1], mov);
231          mov->dest.write_mask = nir_intrinsic_write_mask(intrin);
232          mov->dest.dest.is_ssa = false;
233          mov->dest.dest.reg.reg = reg_src.reg.reg;
234          mov->dest.dest.reg.base_offset = reg_src.reg.base_offset;
235          mov->dest.dest.reg.indirect = reg_src.reg.indirect;
236 
237          nir_builder_instr_insert(b, &mov->instr);
238 
239          nir_instr_remove(&intrin->instr);
240          state->progress = true;
241          break;
242       }
243 
244       case nir_intrinsic_copy_deref:
245          unreachable("There should be no copies whatsoever at this point");
246          break;
247 
248       default:
249          continue;
250       }
251    }
252 
253    return true;
254 }
255 
256 static bool
nir_lower_locals_to_regs_impl(nir_function_impl * impl)257 nir_lower_locals_to_regs_impl(nir_function_impl *impl)
258 {
259    struct locals_to_regs_state state;
260 
261    nir_builder_init(&state.builder, impl);
262    state.progress = false;
263    state.regs_table = _mesa_hash_table_create(NULL, hash_deref, derefs_equal);
264 
265    nir_metadata_require(impl, nir_metadata_dominance);
266 
267    nir_foreach_block(block, impl) {
268       lower_locals_to_regs_block(block, &state);
269    }
270 
271    nir_metadata_preserve(impl, nir_metadata_block_index |
272                                nir_metadata_dominance);
273 
274    _mesa_hash_table_destroy(state.regs_table, NULL);
275 
276    return state.progress;
277 }
278 
279 bool
nir_lower_locals_to_regs(nir_shader * shader)280 nir_lower_locals_to_regs(nir_shader *shader)
281 {
282    bool progress = false;
283 
284    nir_foreach_function(function, shader) {
285       if (function->impl)
286          progress = nir_lower_locals_to_regs_impl(function->impl) || progress;
287    }
288 
289    return progress;
290 }
291