1 /*
2 * Copyright © 2010 Intel Corporation
3 * Copyright © 2018 Broadcom
4 *
5 * Permission is hereby granted, free of charge, to any person obtaining a
6 * copy of this software and associated documentation files (the "Software"),
7 * to deal in the Software without restriction, including without limitation
8 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
9 * and/or sell copies of the Software, and to permit persons to whom the
10 * Software is furnished to do so, subject to the following conditions:
11 *
12 * The above copyright notice and this permission notice (including the next
13 * paragraph) shall be included in all copies or substantial portions of the
14 * Software.
15 *
16 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
17 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
18 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
19 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
20 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
21 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
22 * DEALINGS IN THE SOFTWARE.
23 */
24
25 #include "nir.h"
26 #include "nir_builder.h"
27
28 /** nir_lower_alu.c
29 *
30 * NIR's home for miscellaneous ALU operation lowering implementations.
31 *
32 * Most NIR ALU lowering occurs in nir_opt_algebraic.py, since it's generally
33 * easy to write them there. However, if terms appear multiple times in the
34 * lowered code, it can get very verbose and cause a lot of work for CSE, so
35 * it may end up being easier to write out in C code.
36 *
37 * The shader must be in SSA for this pass.
38 */
39
40 #define LOWER_MUL_HIGH (1 << 0)
41
42 static bool
lower_alu_instr(nir_alu_instr * instr,nir_builder * b)43 lower_alu_instr(nir_alu_instr *instr, nir_builder *b)
44 {
45 nir_ssa_def *lowered = NULL;
46
47 assert(instr->dest.dest.is_ssa);
48
49 b->cursor = nir_before_instr(&instr->instr);
50 b->exact = instr->exact;
51
52 switch (instr->op) {
53 case nir_op_bitfield_reverse:
54 if (b->shader->options->lower_bitfield_reverse) {
55 /* For more details, see:
56 *
57 * http://graphics.stanford.edu/~seander/bithacks.html#ReverseParallel
58 */
59 nir_ssa_def *c1 = nir_imm_int(b, 1);
60 nir_ssa_def *c2 = nir_imm_int(b, 2);
61 nir_ssa_def *c4 = nir_imm_int(b, 4);
62 nir_ssa_def *c8 = nir_imm_int(b, 8);
63 nir_ssa_def *c16 = nir_imm_int(b, 16);
64 nir_ssa_def *c33333333 = nir_imm_int(b, 0x33333333);
65 nir_ssa_def *c55555555 = nir_imm_int(b, 0x55555555);
66 nir_ssa_def *c0f0f0f0f = nir_imm_int(b, 0x0f0f0f0f);
67 nir_ssa_def *c00ff00ff = nir_imm_int(b, 0x00ff00ff);
68
69 lowered = nir_ssa_for_alu_src(b, instr, 0);
70
71 /* Swap odd and even bits. */
72 lowered = nir_ior(b,
73 nir_iand(b, nir_ushr(b, lowered, c1), c55555555),
74 nir_ishl(b, nir_iand(b, lowered, c55555555), c1));
75
76 /* Swap consecutive pairs. */
77 lowered = nir_ior(b,
78 nir_iand(b, nir_ushr(b, lowered, c2), c33333333),
79 nir_ishl(b, nir_iand(b, lowered, c33333333), c2));
80
81 /* Swap nibbles. */
82 lowered = nir_ior(b,
83 nir_iand(b, nir_ushr(b, lowered, c4), c0f0f0f0f),
84 nir_ishl(b, nir_iand(b, lowered, c0f0f0f0f), c4));
85
86 /* Swap bytes. */
87 lowered = nir_ior(b,
88 nir_iand(b, nir_ushr(b, lowered, c8), c00ff00ff),
89 nir_ishl(b, nir_iand(b, lowered, c00ff00ff), c8));
90
91 lowered = nir_ior(b,
92 nir_ushr(b, lowered, c16),
93 nir_ishl(b, lowered, c16));
94 }
95 break;
96
97 case nir_op_bit_count:
98 if (b->shader->options->lower_bit_count) {
99 /* For more details, see:
100 *
101 * http://graphics.stanford.edu/~seander/bithacks.html#CountBitsSetParallel
102 */
103 nir_ssa_def *c1 = nir_imm_int(b, 1);
104 nir_ssa_def *c2 = nir_imm_int(b, 2);
105 nir_ssa_def *c4 = nir_imm_int(b, 4);
106 nir_ssa_def *c24 = nir_imm_int(b, 24);
107 nir_ssa_def *c33333333 = nir_imm_int(b, 0x33333333);
108 nir_ssa_def *c55555555 = nir_imm_int(b, 0x55555555);
109 nir_ssa_def *c0f0f0f0f = nir_imm_int(b, 0x0f0f0f0f);
110 nir_ssa_def *c01010101 = nir_imm_int(b, 0x01010101);
111
112 lowered = nir_ssa_for_alu_src(b, instr, 0);
113
114 lowered = nir_isub(b, lowered,
115 nir_iand(b, nir_ushr(b, lowered, c1), c55555555));
116
117 lowered = nir_iadd(b,
118 nir_iand(b, lowered, c33333333),
119 nir_iand(b, nir_ushr(b, lowered, c2), c33333333));
120
121 lowered = nir_ushr(b,
122 nir_imul(b,
123 nir_iand(b,
124 nir_iadd(b,
125 lowered,
126 nir_ushr(b, lowered, c4)),
127 c0f0f0f0f),
128 c01010101),
129 c24);
130 }
131 break;
132
133 case nir_op_imul_high:
134 case nir_op_umul_high:
135 if (b->shader->options->lower_mul_high) {
136 nir_ssa_def *src0 = nir_ssa_for_alu_src(b, instr, 0);
137 nir_ssa_def *src1 = nir_ssa_for_alu_src(b, instr, 1);
138 if (src0->bit_size < 32) {
139 /* Just do the math in 32-bit space and shift the result */
140 nir_alu_type base_type = nir_op_infos[instr->op].output_type;
141 nir_op upcast_op = nir_type_conversion_op(base_type | src0->bit_size, base_type | 32, nir_rounding_mode_undef);
142 nir_op downscast_op = nir_type_conversion_op(base_type | 32, base_type | src0->bit_size, nir_rounding_mode_undef);
143
144 nir_ssa_def *src0_32 = nir_build_alu(b, upcast_op, src0, NULL, NULL, NULL);
145 nir_ssa_def *src1_32 = nir_build_alu(b, upcast_op, src1, NULL, NULL, NULL);
146 nir_ssa_def *dest_32 = nir_imul(b, src0_32, src1_32);
147 nir_ssa_def *dest_shifted = nir_ishr(b, dest_32, nir_imm_int(b, src0->bit_size));
148 lowered = nir_build_alu(b, downscast_op, dest_shifted, NULL, NULL, NULL);
149 } else {
150 nir_ssa_def *c1 = nir_imm_intN_t(b, 1, src0->bit_size);
151 nir_ssa_def *cshift = nir_imm_int(b, src0->bit_size / 2);
152 nir_ssa_def *cmask = nir_imm_intN_t(b, (1ull << (src0->bit_size / 2)) - 1, src0->bit_size);
153 nir_ssa_def *different_signs = NULL;
154 if (instr->op == nir_op_imul_high) {
155 nir_ssa_def *c0 = nir_imm_intN_t(b, 0, src0->bit_size);
156 different_signs = nir_ixor(b,
157 nir_ilt(b, src0, c0),
158 nir_ilt(b, src1, c0));
159 src0 = nir_iabs(b, src0);
160 src1 = nir_iabs(b, src1);
161 }
162
163 /* ABCD
164 * * EFGH
165 * ======
166 * (GH * CD) + (GH * AB) << 16 + (EF * CD) << 16 + (EF * AB) << 32
167 *
168 * Start by splitting into the 4 multiplies.
169 */
170 nir_ssa_def *src0l = nir_iand(b, src0, cmask);
171 nir_ssa_def *src1l = nir_iand(b, src1, cmask);
172 nir_ssa_def *src0h = nir_ushr(b, src0, cshift);
173 nir_ssa_def *src1h = nir_ushr(b, src1, cshift);
174
175 nir_ssa_def *lo = nir_imul(b, src0l, src1l);
176 nir_ssa_def *m1 = nir_imul(b, src0l, src1h);
177 nir_ssa_def *m2 = nir_imul(b, src0h, src1l);
178 nir_ssa_def *hi = nir_imul(b, src0h, src1h);
179
180 nir_ssa_def *tmp;
181
182 tmp = nir_ishl(b, m1, cshift);
183 hi = nir_iadd(b, hi, nir_iand(b, nir_uadd_carry(b, lo, tmp), c1));
184 lo = nir_iadd(b, lo, tmp);
185 hi = nir_iadd(b, hi, nir_ushr(b, m1, cshift));
186
187 tmp = nir_ishl(b, m2, cshift);
188 hi = nir_iadd(b, hi, nir_iand(b, nir_uadd_carry(b, lo, tmp), c1));
189 lo = nir_iadd(b, lo, tmp);
190 hi = nir_iadd(b, hi, nir_ushr(b, m2, cshift));
191
192 if (instr->op == nir_op_imul_high) {
193 /* For channels where different_signs is set we have to perform a
194 * 64-bit negation. This is *not* the same as just negating the
195 * high 32-bits. Consider -3 * 2. The high 32-bits is 0, but the
196 * desired result is -1, not -0! Recall -x == ~x + 1.
197 */
198 hi = nir_bcsel(b, different_signs,
199 nir_iadd(b,
200 nir_inot(b, hi),
201 nir_iand(b,
202 nir_uadd_carry(b,
203 nir_inot(b, lo),
204 c1),
205 nir_imm_intN_t(b, 1, src0->bit_size))),
206 hi);
207 }
208
209 lowered = hi;
210 }
211 }
212 break;
213
214 default:
215 break;
216 }
217
218 if (lowered) {
219 nir_ssa_def_rewrite_uses(&instr->dest.dest.ssa, lowered);
220 nir_instr_remove(&instr->instr);
221 return true;
222 } else {
223 return false;
224 }
225 }
226
227 bool
nir_lower_alu(nir_shader * shader)228 nir_lower_alu(nir_shader *shader)
229 {
230 bool progress = false;
231
232 if (!shader->options->lower_bitfield_reverse &&
233 !shader->options->lower_mul_high)
234 return false;
235
236 nir_foreach_function(function, shader) {
237 if (function->impl) {
238 nir_builder builder;
239 nir_builder_init(&builder, function->impl);
240
241 nir_foreach_block(block, function->impl) {
242 nir_foreach_instr_safe(instr, block) {
243 if (instr->type == nir_instr_type_alu) {
244 progress = lower_alu_instr(nir_instr_as_alu(instr),
245 &builder) || progress;
246 }
247 }
248 }
249
250 if (progress) {
251 nir_metadata_preserve(function->impl,
252 nir_metadata_block_index |
253 nir_metadata_dominance);
254 }
255 }
256 }
257
258 return progress;
259 }
260