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 */
43static uint8_t
44get_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 */
66static bool
67src_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
86static bool
87analyze_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_b32all_fequal2:
113         case nir_op_b32all_iequal2:
114         case nir_op_b32all_fequal3:
115         case nir_op_b32all_iequal3:
116         case nir_op_b32all_fequal4:
117         case nir_op_b32all_iequal4:
118         case nir_op_b32any_fnequal2:
119         case nir_op_b32any_inequal2:
120         case nir_op_b32any_fnequal3:
121         case nir_op_b32any_inequal3:
122         case nir_op_b32any_fnequal4:
123         case nir_op_b32any_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[0].u32 == NIR_TRUE || load->value[0].u32 == 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
254static void
255analyze_boolean_resolves_impl(nir_function_impl *impl)
256{
257   nir_foreach_block(block, impl) {
258      analyze_boolean_resolves_block(block);
259   }
260}
261
262void
263brw_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