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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 
33 bool
qir_opt_vpm(struct vc4_compile * c)34 qir_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