1/*
2 * Copyright © 2014 Broadcom
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 vc4_opt_vpm.c
26 *
27 * This modifies instructions that exclusively consume a value read from the
28 * VPM to directly read the VPM if other operands allow it.
29 */
30
31#include "vc4_qir.h"
32
33bool
34qir_opt_vpm(struct vc4_compile *c)
35{
36        if (c->stage == QSTAGE_FRAG)
37                return false;
38
39        /* For now, only do this pass when we don't have control flow. */
40        struct qblock *block = qir_entry_block(c);
41        if (block != qir_exit_block(c))
42                return false;
43
44        bool progress = false;
45        uint32_t use_count[c->num_temps];
46        memset(&use_count, 0, sizeof(use_count));
47
48        qir_for_each_inst_inorder(inst, c) {
49                for (int i = 0; i < qir_get_nsrc(inst); i++) {
50                        if (inst->src[i].file == QFILE_TEMP) {
51                                uint32_t temp = inst->src[i].index;
52                                use_count[temp]++;
53                        }
54                }
55        }
56
57        /* For instructions reading from a temporary that contains a VPM read
58         * result, try to move the instruction up in place of the VPM read.
59         */
60        qir_for_each_inst_inorder(inst, c) {
61                if (!inst)
62                        continue;
63
64                if (qir_depends_on_flags(inst) || inst->sf)
65                        continue;
66
67                if (qir_has_side_effects(c, inst) ||
68                    qir_has_side_effect_reads(c, inst) ||
69                    qir_is_tex(inst))
70                        continue;
71
72                for (int j = 0; j < qir_get_nsrc(inst); j++) {
73                        if (inst->src[j].file != QFILE_TEMP ||
74                            inst->src[j].pack)
75                                continue;
76
77                        uint32_t temp = inst->src[j].index;
78
79                        /* Since VPM reads pull from a FIFO, we only get to
80                         * read each VPM entry once (unless we reset the read
81                         * pointer).  That means we can't copy-propagate a VPM
82                         * read to multiple locations.
83                         */
84                        if (use_count[temp] != 1)
85                                continue;
86
87                        struct qinst *mov = c->defs[temp];
88                        if (!mov ||
89                            (mov->op != QOP_MOV &&
90                             mov->op != QOP_FMOV &&
91                             mov->op != QOP_MMOV) ||
92                            mov->src[0].file != QFILE_VPM) {
93                                continue;
94                        }
95
96                        uint32_t temps = 0;
97                        for (int k = 0; k < qir_get_nsrc(inst); k++) {
98                                if (inst->src[k].file == QFILE_TEMP)
99                                        temps++;
100                        }
101
102                        /* The instruction is safe to reorder if its other
103                         * sources are independent of previous instructions
104                         */
105                        if (temps == 1) {
106                                inst->src[j] = mov->src[0];
107
108                                list_del(&inst->link);
109                                list_addtail(&inst->link, &mov->link);
110                                qir_remove_instruction(c, mov);
111
112                                progress = true;
113                                break;
114                        }
115                }
116        }
117
118        return progress;
119}
120