1 /*
2 * Copyright © 2019 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 v3d_opt_redundant_flags.c
26 *
27 * This eliminates the APF/MPF flags for redundant flags updates. These are
28 * often produced by our channel masking in nonuniform control flow.
29 */
30
31 #include "v3d_compiler.h"
32
33 static bool debug;
34
35 static void
vir_dce_pf(struct v3d_compile * c,struct qinst * inst)36 vir_dce_pf(struct v3d_compile *c, struct qinst *inst)
37 {
38 if (debug) {
39 fprintf(stderr,
40 "Removing flags write from: ");
41 vir_dump_inst(c, inst);
42 fprintf(stderr, "\n");
43 }
44
45 assert(inst->qpu.type == V3D_QPU_INSTR_TYPE_ALU);
46
47 inst->qpu.flags.apf = V3D_QPU_PF_NONE;
48 inst->qpu.flags.mpf = V3D_QPU_PF_NONE;
49 }
50
51 static bool
vir_sources_modified(struct qinst * srcs,struct qinst * write)52 vir_sources_modified(struct qinst *srcs, struct qinst *write)
53 {
54 for (int i = 0; i < vir_get_nsrc(srcs); i++) {
55 if (write->dst.file == QFILE_TEMP &&
56 srcs->src[i].file == QFILE_TEMP &&
57 srcs->src[i].index == write->dst.index) {
58 return true;
59 }
60
61 /* assume magic regs may be modified by basically anything. */
62 if (srcs->src[i].file != QFILE_TEMP &&
63 srcs->src[i].file != QFILE_SMALL_IMM)
64 return true;
65 }
66
67 return false;
68 }
69
70 static bool
vir_instr_flags_op_equal(struct qinst * a,struct qinst * b)71 vir_instr_flags_op_equal(struct qinst *a, struct qinst *b)
72 {
73 for (int i = 0; i < vir_get_nsrc(a); i++) {
74 if (a->src[i].file != b->src[i].file ||
75 a->src[i].index != b->src[i].index) {
76 return false;
77 }
78 }
79
80 if (a->qpu.flags.apf != b->qpu.flags.apf ||
81 a->qpu.flags.mpf != b->qpu.flags.mpf ||
82 a->qpu.alu.add.op != b->qpu.alu.add.op ||
83 a->qpu.alu.mul.op != b->qpu.alu.mul.op ||
84 a->qpu.alu.add.a_unpack != b->qpu.alu.add.a_unpack ||
85 a->qpu.alu.add.b_unpack != b->qpu.alu.add.b_unpack ||
86 a->qpu.alu.add.output_pack != b->qpu.alu.add.output_pack ||
87 a->qpu.alu.mul.a_unpack != b->qpu.alu.mul.a_unpack ||
88 a->qpu.alu.mul.b_unpack != b->qpu.alu.mul.b_unpack ||
89 a->qpu.alu.mul.output_pack != b->qpu.alu.mul.output_pack) {
90 return false;
91 }
92
93 return true;
94 }
95
96 static bool
vir_opt_redundant_flags_block(struct v3d_compile * c,struct qblock * block)97 vir_opt_redundant_flags_block(struct v3d_compile *c, struct qblock *block)
98 {
99 struct qinst *last_flags = NULL;
100 bool progress = false;
101
102 vir_for_each_inst(inst, block) {
103 if (inst->qpu.type != V3D_QPU_INSTR_TYPE_ALU ||
104 inst->qpu.flags.auf != V3D_QPU_UF_NONE ||
105 inst->qpu.flags.muf != V3D_QPU_UF_NONE) {
106 last_flags = NULL;
107 continue;
108 }
109
110 /* Flags aren't preserved across a thrsw.
111 *
112 * In V3D 4.2+ flags are preserved across thread switches.
113 */
114 if (c->devinfo->ver < 42) {
115 if (inst->qpu.sig.thrsw)
116 last_flags = NULL;
117 }
118
119 if (inst->qpu.flags.apf != V3D_QPU_PF_NONE ||
120 inst->qpu.flags.mpf != V3D_QPU_PF_NONE) {
121 if (last_flags &&
122 vir_instr_flags_op_equal(inst, last_flags)) {
123 vir_dce_pf(c, inst);
124 progress = true;
125 } else {
126 last_flags = inst;
127 }
128 }
129
130 if (last_flags && vir_sources_modified(last_flags, inst)) {
131 last_flags = NULL;
132 }
133 }
134
135 return progress;
136 }
137
138 bool
vir_opt_redundant_flags(struct v3d_compile * c)139 vir_opt_redundant_flags(struct v3d_compile *c)
140 {
141 bool progress = false;
142
143 vir_for_each_block(block, c) {
144 progress = vir_opt_redundant_flags_block(c, block) || progress;
145 }
146
147 return progress;
148 }
149