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_constant_expressions.h"
29 #include <math.h>
30
31 /*
32 * Implements SSA-based constant folding.
33 */
34
35 struct constant_fold_state {
36 void *mem_ctx;
37 nir_function_impl *impl;
38 bool progress;
39 };
40
41 static bool
constant_fold_alu_instr(nir_alu_instr * instr,void * mem_ctx)42 constant_fold_alu_instr(nir_alu_instr *instr, void *mem_ctx)
43 {
44 nir_const_value src[4];
45
46 if (!instr->dest.dest.is_ssa)
47 return false;
48
49 /* In the case that any outputs/inputs have unsized types, then we need to
50 * guess the bit-size. In this case, the validator ensures that all
51 * bit-sizes match so we can just take the bit-size from first
52 * output/input with an unsized type. If all the outputs/inputs are sized
53 * then we don't need to guess the bit-size at all because the code we
54 * generate for constant opcodes in this case already knows the sizes of
55 * the types involved and does not need the provided bit-size for anything
56 * (although it still requires to receive a valid bit-size).
57 */
58 unsigned bit_size = 0;
59 if (!nir_alu_type_get_type_size(nir_op_infos[instr->op].output_type))
60 bit_size = instr->dest.dest.ssa.bit_size;
61
62 for (unsigned i = 0; i < nir_op_infos[instr->op].num_inputs; i++) {
63 if (!instr->src[i].src.is_ssa)
64 return false;
65
66 if (bit_size == 0 &&
67 !nir_alu_type_get_type_size(nir_op_infos[instr->op].input_sizes[i])) {
68 bit_size = instr->src[i].src.ssa->bit_size;
69 }
70
71 nir_instr *src_instr = instr->src[i].src.ssa->parent_instr;
72
73 if (src_instr->type != nir_instr_type_load_const)
74 return false;
75 nir_load_const_instr* load_const = nir_instr_as_load_const(src_instr);
76
77 for (unsigned j = 0; j < nir_ssa_alu_instr_src_components(instr, i);
78 j++) {
79 if (load_const->def.bit_size == 64)
80 src[i].u64[j] = load_const->value.u64[instr->src[i].swizzle[j]];
81 else
82 src[i].u32[j] = load_const->value.u32[instr->src[i].swizzle[j]];
83 }
84
85 /* We shouldn't have any source modifiers in the optimization loop. */
86 assert(!instr->src[i].abs && !instr->src[i].negate);
87 }
88
89 if (bit_size == 0)
90 bit_size = 32;
91
92 /* We shouldn't have any saturate modifiers in the optimization loop. */
93 assert(!instr->dest.saturate);
94
95 nir_const_value dest =
96 nir_eval_const_opcode(instr->op, instr->dest.dest.ssa.num_components,
97 bit_size, src);
98
99 nir_load_const_instr *new_instr =
100 nir_load_const_instr_create(mem_ctx,
101 instr->dest.dest.ssa.num_components,
102 instr->dest.dest.ssa.bit_size);
103
104 new_instr->value = dest;
105
106 nir_instr_insert_before(&instr->instr, &new_instr->instr);
107
108 nir_ssa_def_rewrite_uses(&instr->dest.dest.ssa,
109 nir_src_for_ssa(&new_instr->def));
110
111 nir_instr_remove(&instr->instr);
112 ralloc_free(instr);
113
114 return true;
115 }
116
117 static bool
constant_fold_deref(nir_instr * instr,nir_deref_var * deref)118 constant_fold_deref(nir_instr *instr, nir_deref_var *deref)
119 {
120 bool progress = false;
121
122 for (nir_deref *tail = deref->deref.child; tail; tail = tail->child) {
123 if (tail->deref_type != nir_deref_type_array)
124 continue;
125
126 nir_deref_array *arr = nir_deref_as_array(tail);
127
128 if (arr->deref_array_type == nir_deref_array_type_indirect &&
129 arr->indirect.is_ssa &&
130 arr->indirect.ssa->parent_instr->type == nir_instr_type_load_const) {
131 nir_load_const_instr *indirect =
132 nir_instr_as_load_const(arr->indirect.ssa->parent_instr);
133
134 arr->base_offset += indirect->value.u32[0];
135
136 /* Clear out the source */
137 nir_instr_rewrite_src(instr, &arr->indirect, nir_src_for_ssa(NULL));
138
139 arr->deref_array_type = nir_deref_array_type_direct;
140
141 progress = true;
142 }
143 }
144
145 return progress;
146 }
147
148 static bool
constant_fold_intrinsic_instr(nir_intrinsic_instr * instr)149 constant_fold_intrinsic_instr(nir_intrinsic_instr *instr)
150 {
151 bool progress = false;
152
153 unsigned num_vars = nir_intrinsic_infos[instr->intrinsic].num_variables;
154 for (unsigned i = 0; i < num_vars; i++) {
155 progress |= constant_fold_deref(&instr->instr, instr->variables[i]);
156 }
157
158 if (instr->intrinsic == nir_intrinsic_discard_if) {
159 nir_const_value *src_val = nir_src_as_const_value(instr->src[0]);
160 if (src_val && src_val->u32[0] == 0) {
161 nir_instr_remove(&instr->instr);
162 progress = true;
163 }
164 }
165
166 return progress;
167 }
168
169 static bool
constant_fold_tex_instr(nir_tex_instr * instr)170 constant_fold_tex_instr(nir_tex_instr *instr)
171 {
172 bool progress = false;
173
174 if (instr->texture)
175 progress |= constant_fold_deref(&instr->instr, instr->texture);
176
177 if (instr->sampler)
178 progress |= constant_fold_deref(&instr->instr, instr->sampler);
179
180 return progress;
181 }
182
183 static bool
constant_fold_block(nir_block * block,void * mem_ctx)184 constant_fold_block(nir_block *block, void *mem_ctx)
185 {
186 bool progress = false;
187
188 nir_foreach_instr_safe(instr, block) {
189 switch (instr->type) {
190 case nir_instr_type_alu:
191 progress |= constant_fold_alu_instr(nir_instr_as_alu(instr), mem_ctx);
192 break;
193 case nir_instr_type_intrinsic:
194 progress |=
195 constant_fold_intrinsic_instr(nir_instr_as_intrinsic(instr));
196 break;
197 case nir_instr_type_tex:
198 progress |= constant_fold_tex_instr(nir_instr_as_tex(instr));
199 break;
200 default:
201 /* Don't know how to constant fold */
202 break;
203 }
204 }
205
206 return progress;
207 }
208
209 static bool
nir_opt_constant_folding_impl(nir_function_impl * impl)210 nir_opt_constant_folding_impl(nir_function_impl *impl)
211 {
212 void *mem_ctx = ralloc_parent(impl);
213 bool progress = false;
214
215 nir_foreach_block(block, impl) {
216 progress |= constant_fold_block(block, mem_ctx);
217 }
218
219 if (progress)
220 nir_metadata_preserve(impl, nir_metadata_block_index |
221 nir_metadata_dominance);
222
223 return progress;
224 }
225
226 bool
nir_opt_constant_folding(nir_shader * shader)227 nir_opt_constant_folding(nir_shader *shader)
228 {
229 bool progress = false;
230
231 nir_foreach_function(function, shader) {
232 if (function->impl)
233 progress |= nir_opt_constant_folding_impl(function->impl);
234 }
235
236 return progress;
237 }
238