1 /*
2 * Copyright © 2015 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 #include "brw_nir.h"
28
29 /*
30 * This file implements an analysis pass that determines when we have to do
31 * a boolean resolve on Gen <= 5. Instructions that need a boolean resolve
32 * will have the booleans portion of the instr->pass_flags field set to
33 * BRW_NIR_BOOLEAN_NEEDS_RESOLVE.
34 */
35
36
37 /** Returns the resolve status for the given source
38 *
39 * If the source has a parent instruction then the resolve status is the
40 * status of the parent instruction. If the source does not have a parent
41 * instruction then we don't know so we return NON_BOOLEAN.
42 */
43 static uint8_t
get_resolve_status_for_src(nir_src * src)44 get_resolve_status_for_src(nir_src *src)
45 {
46 if (src->is_ssa) {
47 nir_instr *src_instr = src->ssa->parent_instr;
48 uint8_t resolve_status = src_instr->pass_flags & BRW_NIR_BOOLEAN_MASK;
49
50 /* If the source instruction needs resolve, then from the perspective
51 * of the user, it's a true boolean.
52 */
53 if (resolve_status == BRW_NIR_BOOLEAN_NEEDS_RESOLVE)
54 resolve_status = BRW_NIR_BOOLEAN_NO_RESOLVE;
55 return resolve_status;
56 } else {
57 return BRW_NIR_NON_BOOLEAN;
58 }
59 }
60
61 /** Marks the given source as needing a resolve
62 *
63 * If the given source corresponds to an unresolved boolean it marks it as
64 * needing a resolve. Otherwise, we leave it alone.
65 */
66 static bool
src_mark_needs_resolve(nir_src * src,void * void_state)67 src_mark_needs_resolve(nir_src *src, void *void_state)
68 {
69 if (src->is_ssa) {
70 nir_instr *src_instr = src->ssa->parent_instr;
71 uint8_t resolve_status = src_instr->pass_flags & BRW_NIR_BOOLEAN_MASK;
72
73 /* If the source instruction is unresolved, then mark it as needing
74 * to be resolved.
75 */
76 if (resolve_status == BRW_NIR_BOOLEAN_UNRESOLVED) {
77 src_instr->pass_flags &= ~BRW_NIR_BOOLEAN_MASK;
78 src_instr->pass_flags |= BRW_NIR_BOOLEAN_NEEDS_RESOLVE;
79 }
80
81 }
82
83 return true;
84 }
85
86 static bool
analyze_boolean_resolves_block(nir_block * block)87 analyze_boolean_resolves_block(nir_block *block)
88 {
89 nir_foreach_instr(instr, block) {
90 switch (instr->type) {
91 case nir_instr_type_alu: {
92 /* For ALU instructions, the resolve status is handled in a
93 * three-step process.
94 *
95 * 1) Look at the instruction type and sources and determine if it
96 * can be left unresolved.
97 *
98 * 2) Look at the destination and see if we have to resolve
99 * anyway. (This is the case if this instruction is not the
100 * only instruction writing to a given register.)
101 *
102 * 3) If the instruction has a resolve status other than
103 * BOOL_UNRESOLVED or BOOL_NEEDS_RESOLVE then we walk through
104 * the sources and ensure that they are also resolved. This
105 * ensures that we don't end up with any stray unresolved
106 * booleans going into ADDs or something like that.
107 */
108
109 uint8_t resolve_status;
110 nir_alu_instr *alu = nir_instr_as_alu(instr);
111 switch (alu->op) {
112 case nir_op_ball_fequal2:
113 case nir_op_ball_iequal2:
114 case nir_op_ball_fequal3:
115 case nir_op_ball_iequal3:
116 case nir_op_ball_fequal4:
117 case nir_op_ball_iequal4:
118 case nir_op_bany_fnequal2:
119 case nir_op_bany_inequal2:
120 case nir_op_bany_fnequal3:
121 case nir_op_bany_inequal3:
122 case nir_op_bany_fnequal4:
123 case nir_op_bany_inequal4:
124 /* These are only implemented by the vec4 backend and its
125 * implementation emits resolved booleans. At some point in the
126 * future, this may change and we'll have to remove some of the
127 * above cases.
128 */
129 resolve_status = BRW_NIR_BOOLEAN_NO_RESOLVE;
130 break;
131
132 case nir_op_imov:
133 case nir_op_inot:
134 /* This is a single-source instruction. Just copy the resolve
135 * status from the source.
136 */
137 resolve_status = get_resolve_status_for_src(&alu->src[0].src);
138 break;
139
140 case nir_op_iand:
141 case nir_op_ior:
142 case nir_op_ixor: {
143 uint8_t src0_status = get_resolve_status_for_src(&alu->src[0].src);
144 uint8_t src1_status = get_resolve_status_for_src(&alu->src[1].src);
145
146 if (src0_status == src1_status) {
147 resolve_status = src0_status;
148 } else if (src0_status == BRW_NIR_NON_BOOLEAN ||
149 src1_status == BRW_NIR_NON_BOOLEAN) {
150 /* If one of the sources is a non-boolean then the whole
151 * thing is a non-boolean.
152 */
153 resolve_status = BRW_NIR_NON_BOOLEAN;
154 } else {
155 /* At this point one of them is a true boolean and one is a
156 * boolean that needs a resolve. We could either resolve the
157 * unresolved source or we could resolve here. If we resolve
158 * the unresolved source then we get two resolves for the price
159 * of one. Just set this one to BOOLEAN_NO_RESOLVE and we'll
160 * let the code below force a resolve on the unresolved source.
161 */
162 resolve_status = BRW_NIR_BOOLEAN_NO_RESOLVE;
163 }
164 break;
165 }
166
167 default:
168 if (nir_alu_type_get_base_type(nir_op_infos[alu->op].output_type) == nir_type_bool) {
169 /* This instructions will turn into a CMP when we actually emit
170 * them so the result will have to be resolved before it can be
171 * used.
172 */
173 resolve_status = BRW_NIR_BOOLEAN_UNRESOLVED;
174
175 /* Even though the destination is allowed to be left
176 * unresolved, the sources are treated as regular integers or
177 * floats so they need to be resolved.
178 */
179 nir_foreach_src(instr, src_mark_needs_resolve, NULL);
180 } else {
181 resolve_status = BRW_NIR_NON_BOOLEAN;
182 }
183 }
184
185 /* If the destination is SSA, go ahead allow unresolved booleans.
186 * If the destination register doesn't have a well-defined parent_instr
187 * we need to resolve immediately.
188 */
189 if (!alu->dest.dest.is_ssa &&
190 resolve_status == BRW_NIR_BOOLEAN_UNRESOLVED) {
191 resolve_status = BRW_NIR_BOOLEAN_NEEDS_RESOLVE;
192 }
193
194 instr->pass_flags = (instr->pass_flags & ~BRW_NIR_BOOLEAN_MASK) |
195 resolve_status;
196
197 /* Finally, resolve sources if it's needed */
198 switch (resolve_status) {
199 case BRW_NIR_BOOLEAN_NEEDS_RESOLVE:
200 case BRW_NIR_BOOLEAN_UNRESOLVED:
201 /* This instruction is either unresolved or we're doing the
202 * resolve here; leave the sources alone.
203 */
204 break;
205
206 case BRW_NIR_BOOLEAN_NO_RESOLVE:
207 case BRW_NIR_NON_BOOLEAN:
208 nir_foreach_src(instr, src_mark_needs_resolve, NULL);
209 break;
210
211 default:
212 unreachable("Invalid boolean flag");
213 }
214
215 break;
216 }
217
218 case nir_instr_type_load_const: {
219 nir_load_const_instr *load = nir_instr_as_load_const(instr);
220
221 /* For load_const instructions, it's a boolean exactly when it holds
222 * one of the values NIR_TRUE or NIR_FALSE.
223 *
224 * Since load_const instructions don't have any sources, we don't
225 * have to worry about resolving them.
226 */
227 instr->pass_flags &= ~BRW_NIR_BOOLEAN_MASK;
228 if (load->value.u32[0] == NIR_TRUE || load->value.u32[0] == NIR_FALSE) {
229 instr->pass_flags |= BRW_NIR_BOOLEAN_NO_RESOLVE;
230 } else {
231 instr->pass_flags |= BRW_NIR_NON_BOOLEAN;
232 }
233 continue;
234 }
235
236 default:
237 /* Everything else is an unknown non-boolean value and needs to
238 * have all sources resolved.
239 */
240 instr->pass_flags = (instr->pass_flags & ~BRW_NIR_BOOLEAN_MASK) |
241 BRW_NIR_NON_BOOLEAN;
242 nir_foreach_src(instr, src_mark_needs_resolve, NULL);
243 continue;
244 }
245 }
246
247 nir_if *following_if = nir_block_get_following_if(block);
248 if (following_if)
249 src_mark_needs_resolve(&following_if->condition, NULL);
250
251 return true;
252 }
253
254 static void
analyze_boolean_resolves_impl(nir_function_impl * impl)255 analyze_boolean_resolves_impl(nir_function_impl *impl)
256 {
257 nir_foreach_block(block, impl) {
258 analyze_boolean_resolves_block(block);
259 }
260 }
261
262 void
brw_nir_analyze_boolean_resolves(nir_shader * shader)263 brw_nir_analyze_boolean_resolves(nir_shader *shader)
264 {
265 nir_foreach_function(function, shader) {
266 if (function->impl)
267 analyze_boolean_resolves_impl(function->impl);
268 }
269 }
270