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 */
24
25/** @file brw_vec4_cmod_propagation.cpp
26 *
27 * Really similar to brw_fs_cmod_propagation but adapted to vec4 needs. Check
28 * brw_fs_cmod_propagation for further details on the rationale behind this
29 * optimization.
30 */
31
32#include "brw_vec4.h"
33#include "brw_cfg.h"
34#include "brw_eu.h"
35
36namespace brw {
37
38static bool
39opt_cmod_propagation_local(bblock_t *block)
40{
41   bool progress = false;
42   int ip = block->end_ip + 1;
43
44   foreach_inst_in_block_reverse_safe(vec4_instruction, inst, block) {
45      ip--;
46
47      if ((inst->opcode != BRW_OPCODE_AND &&
48           inst->opcode != BRW_OPCODE_CMP &&
49           inst->opcode != BRW_OPCODE_MOV) ||
50          inst->predicate != BRW_PREDICATE_NONE ||
51          !inst->dst.is_null() ||
52          inst->src[0].file != VGRF ||
53          inst->src[0].abs)
54         continue;
55
56      if (inst->opcode == BRW_OPCODE_AND &&
57          !(inst->src[1].is_one() &&
58            inst->conditional_mod == BRW_CONDITIONAL_NZ &&
59            !inst->src[0].negate))
60         continue;
61
62      if (inst->opcode == BRW_OPCODE_CMP && !inst->src[1].is_zero())
63         continue;
64
65      if (inst->opcode == BRW_OPCODE_MOV &&
66          inst->conditional_mod != BRW_CONDITIONAL_NZ)
67         continue;
68
69      bool read_flag = false;
70      foreach_inst_in_block_reverse_starting_from(vec4_instruction, scan_inst, inst) {
71         if (regions_overlap(inst->src[0], inst->size_read(0),
72                             scan_inst->dst, scan_inst->size_written)) {
73            if ((scan_inst->predicate && scan_inst->opcode != BRW_OPCODE_SEL) ||
74                scan_inst->dst.offset != inst->src[0].offset ||
75                (scan_inst->dst.writemask != WRITEMASK_X &&
76                 scan_inst->dst.writemask != WRITEMASK_XYZW) ||
77                (scan_inst->dst.writemask == WRITEMASK_XYZW &&
78                 inst->src[0].swizzle != BRW_SWIZZLE_XYZW) ||
79                (inst->dst.writemask & ~scan_inst->dst.writemask) != 0 ||
80                scan_inst->exec_size != inst->exec_size ||
81                scan_inst->group != inst->group) {
82               break;
83            }
84
85            /* CMP's result is the same regardless of dest type. */
86            if (inst->conditional_mod == BRW_CONDITIONAL_NZ &&
87                scan_inst->opcode == BRW_OPCODE_CMP &&
88                (inst->dst.type == BRW_REGISTER_TYPE_D ||
89                 inst->dst.type == BRW_REGISTER_TYPE_UD)) {
90               inst->remove(block);
91               progress = true;
92               break;
93            }
94
95            /* If the AND wasn't handled by the previous case, it isn't safe
96             * to remove it.
97             */
98            if (inst->opcode == BRW_OPCODE_AND)
99               break;
100
101            /* Comparisons operate differently for ints and floats */
102            if (scan_inst->dst.type != inst->dst.type &&
103                (scan_inst->dst.type == BRW_REGISTER_TYPE_F ||
104                 inst->dst.type == BRW_REGISTER_TYPE_F))
105               break;
106
107            /* If the instruction generating inst's source also wrote the
108             * flag, and inst is doing a simple .nz comparison, then inst
109             * is redundant - the appropriate value is already in the flag
110             * register.  Delete inst.
111             */
112            if (inst->conditional_mod == BRW_CONDITIONAL_NZ &&
113                !inst->src[0].negate &&
114                scan_inst->writes_flag()) {
115               inst->remove(block);
116               progress = true;
117               break;
118            }
119
120            /* The conditional mod of the CMP/CMPN instructions behaves
121             * specially because the flag output is not calculated from the
122             * result of the instruction, but the other way around, which
123             * means that even if the condmod to propagate and the condmod
124             * from the CMP instruction are the same they will in general give
125             * different results because they are evaluated based on different
126             * inputs.
127             */
128            if (scan_inst->opcode == BRW_OPCODE_CMP ||
129                scan_inst->opcode == BRW_OPCODE_CMPN)
130               break;
131
132            /* Otherwise, try propagating the conditional. */
133            enum brw_conditional_mod cond =
134               inst->src[0].negate ? brw_swap_cmod(inst->conditional_mod)
135                                   : inst->conditional_mod;
136
137            if (scan_inst->can_do_cmod() &&
138                ((!read_flag && scan_inst->conditional_mod == BRW_CONDITIONAL_NONE) ||
139                 scan_inst->conditional_mod == cond)) {
140               scan_inst->conditional_mod = cond;
141               inst->remove(block);
142               progress = true;
143            }
144            break;
145         }
146
147         if (scan_inst->writes_flag())
148            break;
149
150         read_flag = read_flag || scan_inst->reads_flag();
151      }
152   }
153
154   return progress;
155}
156
157bool
158vec4_visitor::opt_cmod_propagation()
159{
160   bool progress = false;
161
162   foreach_block_reverse(block, cfg) {
163      progress = opt_cmod_propagation_local(block) || progress;
164   }
165
166   if (progress)
167      invalidate_live_intervals();
168
169   return progress;
170}
171
172} /* namespace brw */
173