1 /*
2 * Copyright 2013 Vadim Girlin <vadimgirlin@gmail.com>
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 * on the rights to use, copy, modify, merge, publish, distribute, sub
8 * license, and/or sell copies of the Software, and to permit persons to whom
9 * the 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 NON-INFRINGEMENT. IN NO EVENT SHALL
18 * THE AUTHOR(S) AND/OR THEIR SUPPLIERS BE LIABLE FOR ANY CLAIM,
19 * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
20 * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
21 * USE OR OTHER DEALINGS IN THE SOFTWARE.
22 *
23 * Authors:
24 * Vadim Girlin
25 */
26
27 #define IFC_DEBUG 0
28
29 #if IFC_DEBUG
30 #define IFC_DUMP(q) do { q } while (0)
31 #else
32 #define IFC_DUMP(q)
33 #endif
34
35 #include "sb_shader.h"
36 #include "sb_pass.h"
37
38 namespace r600_sb {
39
run()40 int if_conversion::run() {
41
42 regions_vec &rv = sh.get_regions();
43
44 unsigned converted = 0;
45 for (regions_vec::reverse_iterator I = rv.rbegin(); I != rv.rend(); ) {
46 region_node *r = *I;
47 if (run_on(r)) {
48 I = regions_vec::reverse_iterator(rv.erase((++I).base()));
49 ++converted;
50 } else
51 ++I;
52 }
53 return 0;
54 }
55
convert_kill_instructions(region_node * r,value * em,bool branch,container_node * c)56 void if_conversion::convert_kill_instructions(region_node *r,
57 value *em, bool branch,
58 container_node *c) {
59 value *cnd = NULL;
60
61 for (node_iterator I = c->begin(), E = c->end(), N; I != E; I = N) {
62 N = I + 1;
63
64 if (!I->is_alu_inst())
65 continue;
66
67 alu_node *a = static_cast<alu_node*>(*I);
68 unsigned flags = a->bc.op_ptr->flags;
69
70 if (!(flags & AF_KILL))
71 continue;
72
73 // ignore predicated or non-const kill instructions
74 if (a->pred || !a->src[0]->is_const() || !a->src[1]->is_const())
75 continue;
76
77 literal l0 = a->src[0]->literal_value;
78 literal l1 = a->src[1]->literal_value;
79
80 expr_handler::apply_alu_src_mod(a->bc, 0, l0);
81 expr_handler::apply_alu_src_mod(a->bc, 1, l1);
82
83 if (expr_handler::evaluate_condition(flags, l0, l1)) {
84 // kill with constant 'true' condition, we'll convert it to the
85 // conditional kill outside of the if-then-else block
86
87 a->remove();
88
89 if (!cnd) {
90 cnd = get_select_value_for_em(sh, em);
91 } else {
92 // more than one kill with the same condition, just remove it
93 continue;
94 }
95
96 r->insert_before(a);
97 a->bc.set_op(branch ? ALU_OP2_KILLE_INT : ALU_OP2_KILLNE_INT);
98
99 a->src[0] = cnd;
100 a->src[1] = sh.get_const_value(0);
101 // clear modifiers
102 a->bc.src[0].clear();
103 a->bc.src[1].clear();
104 } else {
105 // kill with constant 'false' condition, this shouldn't happen
106 // but remove it anyway
107 a->remove();
108 }
109 }
110 }
111
check_and_convert(region_node * r)112 bool if_conversion::check_and_convert(region_node *r) {
113
114 depart_node *nd1 = static_cast<depart_node*>(r->first);
115 if (!nd1->is_depart() || nd1->target != r)
116 return false;
117 if_node *nif = static_cast<if_node*>(nd1->first);
118 if (!nif->is_if())
119 return false;
120 depart_node *nd2 = static_cast<depart_node*>(nif->first);
121 if (!nd2->is_depart() || nd2->target != r)
122 return false;
123
124 value* &em = nif->cond;
125
126 node_stats s;
127
128 r->collect_stats(s);
129
130 IFC_DUMP(
131 sblog << "ifcvt: region " << r->region_id << " :\n";
132 s.dump();
133 );
134
135 if (s.region_count || s.fetch_count || s.alu_kill_count ||
136 s.if_count != 1 || s.repeat_count || s.uses_ar)
137 return false;
138
139 unsigned real_alu_count = s.alu_count - s.alu_copy_mov_count;
140
141 // if_conversion allows to eliminate JUMP-ALU_POP_AFTER or
142 // JUMP-ALU-ELSE-ALU_POP_AFTER, for now let's assume that 3 CF instructions
143 // are eliminated. According to the docs, cost of CF instruction is
144 // equal to ~40 ALU VLIW instructions (instruction groups),
145 // so we have eliminated cost equal to ~120 groups in total.
146 // Let's also assume that we have avg 3 ALU instructions per group,
147 // This means that potential eliminated cost is about 360 single alu inst.
148 // On the other hand, we are speculatively executing conditional code now,
149 // so we are increasing the cost in some cases. In the worst case, we'll
150 // have to execute real_alu_count additional alu instructions instead of
151 // jumping over them. Let's assume for now that average added cost is
152 //
153 // (0.9 * real_alu_count)
154 //
155 // So we should perform if_conversion if
156 //
157 // (0.9 * real_alu_count) < 360, or
158 //
159 // real_alu_count < 400
160 //
161 // So if real_alu_count is more than 400, than we think that if_conversion
162 // doesn't make sense.
163
164 // FIXME: We can use more precise heuristic, taking into account sizes of
165 // the branches and their probability instead of total size.
166 // Another way to improve this is to consider the number of the groups
167 // instead of the number of instructions (taking into account actual VLIW
168 // packing).
169 // (Currently we don't know anything about packing at this stage, but
170 // probably we can make some more precise estimations anyway)
171
172 if (real_alu_count > 400)
173 return false;
174
175 IFC_DUMP( sblog << "if_cvt: processing...\n"; );
176
177 value *select = get_select_value_for_em(sh, em);
178
179 if (!select)
180 return false;
181
182 for (node_iterator I = r->phi->begin(), E = r->phi->end(); I != E; ++I) {
183 node *n = *I;
184
185 alu_node *ns = convert_phi(select, n);
186
187 if (ns)
188 r->insert_after(ns);
189 }
190
191 nd2->expand();
192 nif->expand();
193 nd1->expand();
194 r->expand();
195
196 return true;
197 }
198
run_on(region_node * r)199 bool if_conversion::run_on(region_node* r) {
200
201 if (r->dep_count() != 2 || r->rep_count() != 1)
202 return false;
203
204 depart_node *nd1 = static_cast<depart_node*>(r->first);
205 if (!nd1->is_depart())
206 return false;
207 if_node *nif = static_cast<if_node*>(nd1->first);
208 if (!nif->is_if())
209 return false;
210 depart_node *nd2 = static_cast<depart_node*>(nif->first);
211 if (!nd2->is_depart())
212 return false;
213
214 value* &em = nif->cond;
215
216 convert_kill_instructions(r, em, true, nd2);
217 convert_kill_instructions(r, em, false, nd1);
218
219 if (check_and_convert(r))
220 return true;
221
222 if (nd2->empty() && nif->next) {
223 // empty true branch, non-empty false branch
224 // we'll invert it to get rid of 'else'
225
226 assert(em && em->def);
227
228 alu_node *predset = static_cast<alu_node*>(em->def);
229
230 // create clone of PREDSET instruction with inverted condition.
231 // PREDSET has 3 dst operands in our IR (value written to gpr,
232 // predicate value and exec mask value), we'll split it such that
233 // new PREDSET will define exec mask value only, and two others will
234 // be defined in the old PREDSET (if they are not used then DCE will
235 // simply remove old PREDSET).
236
237 alu_node *newpredset = sh.clone(predset);
238 predset->insert_after(newpredset);
239
240 predset->dst[2] = NULL;
241
242 newpredset->dst[0] = NULL;
243 newpredset->dst[1] = NULL;
244
245 em->def = newpredset;
246
247 unsigned cc = newpredset->bc.op_ptr->flags & AF_CC_MASK;
248 unsigned cmptype = newpredset->bc.op_ptr->flags & AF_CMP_TYPE_MASK;
249 bool swapargs = false;
250
251 cc = invert_setcc_condition(cc, swapargs);
252
253 if (swapargs) {
254 std::swap(newpredset->src[0], newpredset->src[1]);
255 std::swap(newpredset->bc.src[0], newpredset->bc.src[1]);
256 }
257
258 unsigned newopcode = get_predsetcc_op(cc, cmptype);
259 newpredset->bc.set_op(newopcode);
260
261 // move the code from the 'false' branch ('else') to the 'true' branch
262 nd2->move(nif->next, NULL);
263
264 // swap phi operands
265 for (node_iterator I = r->phi->begin(), E = r->phi->end(); I != E;
266 ++I) {
267 node *p = *I;
268 assert(p->src.size() == 2);
269 std::swap(p->src[0], p->src[1]);
270 }
271 }
272
273 return false;
274 }
275
convert_phi(value * select,node * phi)276 alu_node* if_conversion::convert_phi(value* select, node* phi) {
277 assert(phi->dst.size() == 1 || phi->src.size() == 2);
278
279 value *d = phi->dst[0];
280 value *v1 = phi->src[0];
281 value *v2 = phi->src[1];
282
283 assert(d);
284
285 if (!d->is_any_gpr())
286 return NULL;
287
288 if (v1->is_undef()) {
289 if (v2->is_undef()) {
290 return NULL;
291 } else {
292 return sh.create_mov(d, v2);
293 }
294 } else if (v2->is_undef())
295 return sh.create_mov(d, v1);
296
297 alu_node* n = sh.create_alu();
298
299 n->bc.set_op(ALU_OP3_CNDE_INT);
300 n->dst.push_back(d);
301 n->src.push_back(select);
302 n->src.push_back(v1);
303 n->src.push_back(v2);
304
305 return n;
306 }
307
308 } // namespace r600_sb
309