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689ba89d | 1 | /* Perform doloop optimizations |
5624e564 | 2 | Copyright (C) 2004-2015 Free Software Foundation, Inc. |
689ba89d ZD |
3 | Based on code by Michael P. Hayes (m.hayes@elec.canterbury.ac.nz) |
4 | ||
5 | This file is part of GCC. | |
6 | ||
7 | GCC is free software; you can redistribute it and/or modify it under | |
8 | the terms of the GNU General Public License as published by the Free | |
9dcd6f09 | 9 | Software Foundation; either version 3, or (at your option) any later |
689ba89d ZD |
10 | version. |
11 | ||
12 | GCC is distributed in the hope that it will be useful, but WITHOUT ANY | |
13 | WARRANTY; without even the implied warranty of MERCHANTABILITY or | |
14 | FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License | |
15 | for more details. | |
16 | ||
17 | You should have received a copy of the GNU General Public License | |
9dcd6f09 NC |
18 | along with GCC; see the file COPYING3. If not see |
19 | <http://www.gnu.org/licenses/>. */ | |
689ba89d ZD |
20 | |
21 | #include "config.h" | |
22 | #include "system.h" | |
23 | #include "coretypes.h" | |
c7131fb2 | 24 | #include "backend.h" |
9fdcd34e | 25 | #include "cfghooks.h" |
689ba89d ZD |
26 | #include "rtl.h" |
27 | #include "flags.h" | |
36566b39 | 28 | #include "tree.h" |
c7131fb2 | 29 | #include "alias.h" |
36566b39 PK |
30 | #include "insn-config.h" |
31 | #include "expmed.h" | |
32 | #include "dojump.h" | |
33 | #include "explow.h" | |
34 | #include "calls.h" | |
35 | #include "emit-rtl.h" | |
36 | #include "varasm.h" | |
37 | #include "stmt.h" | |
38 | #include "expr.h" | |
718f9c0f | 39 | #include "diagnostic-core.h" |
689ba89d ZD |
40 | #include "tm_p.h" |
41 | #include "cfgloop.h" | |
60393bbc | 42 | #include "cfgrtl.h" |
689ba89d | 43 | #include "params.h" |
a71a498d | 44 | #include "target.h" |
7ee2468b | 45 | #include "dumpfile.h" |
50684f95 | 46 | #include "loop-unroll.h" |
689ba89d ZD |
47 | |
48 | /* This module is used to modify loops with a determinable number of | |
49 | iterations to use special low-overhead looping instructions. | |
50 | ||
51 | It first validates whether the loop is well behaved and has a | |
52 | determinable number of iterations (either at compile or run-time). | |
53 | It then modifies the loop to use a low-overhead looping pattern as | |
54 | follows: | |
55 | ||
56 | 1. A pseudo register is allocated as the loop iteration counter. | |
57 | ||
58 | 2. The number of loop iterations is calculated and is stored | |
59 | in the loop counter. | |
60 | ||
61 | 3. At the end of the loop, the jump insn is replaced by the | |
62 | doloop_end pattern. The compare must remain because it might be | |
63 | used elsewhere. If the loop-variable or condition register are | |
64 | used elsewhere, they will be eliminated by flow. | |
65 | ||
66 | 4. An optional doloop_begin pattern is inserted at the top of the | |
67 | loop. | |
68 | ||
69 | TODO The optimization should only performed when either the biv used for exit | |
70 | condition is unused at all except for the exit test, or if we do not have to | |
71 | change its value, since otherwise we have to add a new induction variable, | |
72 | which usually will not pay up (unless the cost of the doloop pattern is | |
73 | somehow extremely lower than the cost of compare & jump, or unless the bct | |
74 | register cannot be used for anything else but doloop -- ??? detect these | |
75 | cases). */ | |
76 | ||
689ba89d ZD |
77 | /* Return the loop termination condition for PATTERN or zero |
78 | if it is not a decrement and branch jump insn. */ | |
79 | ||
75c70254 | 80 | rtx |
46dc0789 | 81 | doloop_condition_get (rtx doloop_pat) |
689ba89d ZD |
82 | { |
83 | rtx cmp; | |
84 | rtx inc; | |
85 | rtx reg; | |
75c70254 | 86 | rtx inc_src; |
689ba89d | 87 | rtx condition; |
46dc0789 | 88 | rtx pattern; |
ce7b3761 RE |
89 | rtx cc_reg = NULL_RTX; |
90 | rtx reg_orig = NULL_RTX; | |
689ba89d | 91 | |
46dc0789 MN |
92 | /* The canonical doloop pattern we expect has one of the following |
93 | forms: | |
689ba89d | 94 | |
46dc0789 MN |
95 | 1) (parallel [(set (pc) (if_then_else (condition) |
96 | (label_ref (label)) | |
97 | (pc))) | |
98 | (set (reg) (plus (reg) (const_int -1))) | |
99 | (additional clobbers and uses)]) | |
689ba89d | 100 | |
46dc0789 MN |
101 | The branch must be the first entry of the parallel (also required |
102 | by jump.c), and the second entry of the parallel must be a set of | |
103 | the loop counter register. Some targets (IA-64) wrap the set of | |
104 | the loop counter in an if_then_else too. | |
75c70254 | 105 | |
46dc0789 MN |
106 | 2) (set (reg) (plus (reg) (const_int -1)) |
107 | (set (pc) (if_then_else (reg != 0) | |
108 | (label_ref (label)) | |
ce7b3761 RE |
109 | (pc))). |
110 | ||
111 | Some targets (ARM) do the comparison before the branch, as in the | |
112 | following form: | |
113 | ||
114 | 3) (parallel [(set (cc) (compare ((plus (reg) (const_int -1), 0))) | |
115 | (set (reg) (plus (reg) (const_int -1)))]) | |
116 | (set (pc) (if_then_else (cc == NE) | |
117 | (label_ref (label)) | |
118 | (pc))) */ | |
46dc0789 MN |
119 | |
120 | pattern = PATTERN (doloop_pat); | |
689ba89d ZD |
121 | |
122 | if (GET_CODE (pattern) != PARALLEL) | |
46dc0789 MN |
123 | { |
124 | rtx cond; | |
21afc57d | 125 | rtx_insn *prev_insn = prev_nondebug_insn (doloop_pat); |
ce7b3761 RE |
126 | rtx cmp_arg1, cmp_arg2; |
127 | rtx cmp_orig; | |
46dc0789 | 128 | |
ce7b3761 RE |
129 | /* In case the pattern is not PARALLEL we expect two forms |
130 | of doloop which are cases 2) and 3) above: in case 2) the | |
131 | decrement immediately precedes the branch, while in case 3) | |
132 | the compare and decrement instructions immediately precede | |
133 | the branch. */ | |
689ba89d | 134 | |
0be955e7 | 135 | if (prev_insn == NULL_RTX || !INSN_P (prev_insn)) |
46dc0789 MN |
136 | return 0; |
137 | ||
138 | cmp = pattern; | |
ce7b3761 RE |
139 | if (GET_CODE (PATTERN (prev_insn)) == PARALLEL) |
140 | { | |
141 | /* The third case: the compare and decrement instructions | |
142 | immediately precede the branch. */ | |
143 | cmp_orig = XVECEXP (PATTERN (prev_insn), 0, 0); | |
144 | if (GET_CODE (cmp_orig) != SET) | |
145 | return 0; | |
146 | if (GET_CODE (SET_SRC (cmp_orig)) != COMPARE) | |
147 | return 0; | |
148 | cmp_arg1 = XEXP (SET_SRC (cmp_orig), 0); | |
149 | cmp_arg2 = XEXP (SET_SRC (cmp_orig), 1); | |
150 | if (cmp_arg2 != const0_rtx | |
151 | || GET_CODE (cmp_arg1) != PLUS) | |
152 | return 0; | |
153 | reg_orig = XEXP (cmp_arg1, 0); | |
154 | if (XEXP (cmp_arg1, 1) != GEN_INT (-1) | |
155 | || !REG_P (reg_orig)) | |
156 | return 0; | |
157 | cc_reg = SET_DEST (cmp_orig); | |
158 | ||
159 | inc = XVECEXP (PATTERN (prev_insn), 0, 1); | |
160 | } | |
161 | else | |
b8abece3 | 162 | inc = PATTERN (prev_insn); |
46dc0789 MN |
163 | /* We expect the condition to be of the form (reg != 0) */ |
164 | cond = XEXP (SET_SRC (cmp), 0); | |
165 | if (GET_CODE (cond) != NE || XEXP (cond, 1) != const0_rtx) | |
166 | return 0; | |
46dc0789 MN |
167 | } |
168 | else | |
169 | { | |
170 | cmp = XVECEXP (pattern, 0, 0); | |
171 | inc = XVECEXP (pattern, 0, 1); | |
172 | } | |
689ba89d ZD |
173 | |
174 | /* Check for (set (reg) (something)). */ | |
75c70254 | 175 | if (GET_CODE (inc) != SET) |
689ba89d | 176 | return 0; |
689ba89d | 177 | reg = SET_DEST (inc); |
75c70254 SB |
178 | if (! REG_P (reg)) |
179 | return 0; | |
180 | ||
181 | /* Check if something = (plus (reg) (const_int -1)). | |
182 | On IA-64, this decrement is wrapped in an if_then_else. */ | |
183 | inc_src = SET_SRC (inc); | |
184 | if (GET_CODE (inc_src) == IF_THEN_ELSE) | |
185 | inc_src = XEXP (inc_src, 1); | |
186 | if (GET_CODE (inc_src) != PLUS | |
187 | || XEXP (inc_src, 0) != reg | |
188 | || XEXP (inc_src, 1) != constm1_rtx) | |
189 | return 0; | |
689ba89d ZD |
190 | |
191 | /* Check for (set (pc) (if_then_else (condition) | |
192 | (label_ref (label)) | |
193 | (pc))). */ | |
194 | if (GET_CODE (cmp) != SET | |
195 | || SET_DEST (cmp) != pc_rtx | |
196 | || GET_CODE (SET_SRC (cmp)) != IF_THEN_ELSE | |
197 | || GET_CODE (XEXP (SET_SRC (cmp), 1)) != LABEL_REF | |
198 | || XEXP (SET_SRC (cmp), 2) != pc_rtx) | |
199 | return 0; | |
200 | ||
201 | /* Extract loop termination condition. */ | |
202 | condition = XEXP (SET_SRC (cmp), 0); | |
203 | ||
75c70254 SB |
204 | /* We expect a GE or NE comparison with 0 or 1. */ |
205 | if ((GET_CODE (condition) != GE | |
206 | && GET_CODE (condition) != NE) | |
207 | || (XEXP (condition, 1) != const0_rtx | |
208 | && XEXP (condition, 1) != const1_rtx)) | |
689ba89d ZD |
209 | return 0; |
210 | ||
75c70254 | 211 | if ((XEXP (condition, 0) == reg) |
ce7b3761 RE |
212 | /* For the third case: */ |
213 | || ((cc_reg != NULL_RTX) | |
214 | && (XEXP (condition, 0) == cc_reg) | |
215 | && (reg_orig == reg)) | |
75c70254 | 216 | || (GET_CODE (XEXP (condition, 0)) == PLUS |
ce7b3761 | 217 | && XEXP (XEXP (condition, 0), 0) == reg)) |
46dc0789 MN |
218 | { |
219 | if (GET_CODE (pattern) != PARALLEL) | |
ce7b3761 | 220 | /* For the second form we expect: |
46dc0789 MN |
221 | |
222 | (set (reg) (plus (reg) (const_int -1)) | |
223 | (set (pc) (if_then_else (reg != 0) | |
224 | (label_ref (label)) | |
225 | (pc))). | |
226 | ||
227 | is equivalent to the following: | |
228 | ||
229 | (parallel [(set (pc) (if_then_else (reg != 1) | |
230 | (label_ref (label)) | |
231 | (pc))) | |
232 | (set (reg) (plus (reg) (const_int -1))) | |
233 | (additional clobbers and uses)]) | |
234 | ||
ce7b3761 RE |
235 | For the third form we expect: |
236 | ||
237 | (parallel [(set (cc) (compare ((plus (reg) (const_int -1)), 0)) | |
238 | (set (reg) (plus (reg) (const_int -1)))]) | |
239 | (set (pc) (if_then_else (cc == NE) | |
240 | (label_ref (label)) | |
241 | (pc))) | |
242 | ||
243 | which is equivalent to the following: | |
244 | ||
245 | (parallel [(set (cc) (compare (reg, 1)) | |
246 | (set (reg) (plus (reg) (const_int -1))) | |
247 | (set (pc) (if_then_else (NE == cc) | |
248 | (label_ref (label)) | |
249 | (pc))))]) | |
250 | ||
251 | So we return the second form instead for the two cases. | |
252 | ||
46dc0789 MN |
253 | */ |
254 | condition = gen_rtx_fmt_ee (NE, VOIDmode, inc_src, const1_rtx); | |
255 | ||
689ba89d | 256 | return condition; |
46dc0789 | 257 | } |
689ba89d ZD |
258 | |
259 | /* ??? If a machine uses a funny comparison, we could return a | |
1ae58c30 | 260 | canonicalized form here. */ |
689ba89d ZD |
261 | |
262 | return 0; | |
263 | } | |
264 | ||
265 | /* Return nonzero if the loop specified by LOOP is suitable for | |
266 | the use of special low-overhead looping instructions. DESC | |
267 | describes the number of iterations of the loop. */ | |
268 | ||
269 | static bool | |
270 | doloop_valid_p (struct loop *loop, struct niter_desc *desc) | |
271 | { | |
272 | basic_block *body = get_loop_body (loop), bb; | |
871eb193 | 273 | rtx_insn *insn; |
689ba89d | 274 | unsigned i; |
7600f094 | 275 | bool result = true; |
689ba89d ZD |
276 | |
277 | /* Check for loops that may not terminate under special conditions. */ | |
278 | if (!desc->simple_p | |
279 | || desc->assumptions | |
280 | || desc->infinite) | |
281 | { | |
282 | /* There are some cases that would require a special attention. | |
283 | For example if the comparison is LEU and the comparison value | |
284 | is UINT_MAX then the loop will not terminate. Similarly, if the | |
285 | comparison code is GEU and the comparison value is 0, the | |
286 | loop will not terminate. | |
287 | ||
288 | If the absolute increment is not 1, the loop can be infinite | |
289 | even with LTU/GTU, e.g. for (i = 3; i > 0; i -= 2) | |
290 | ||
291 | ??? We could compute these conditions at run-time and have a | |
292 | additional jump around the loop to ensure an infinite loop. | |
293 | However, it is very unlikely that this is the intended | |
294 | behavior of the loop and checking for these rare boundary | |
295 | conditions would pessimize all other code. | |
296 | ||
297 | If the loop is executed only a few times an extra check to | |
298 | restart the loop could use up most of the benefits of using a | |
299 | count register loop. Note however, that normally, this | |
300 | restart branch would never execute, so it could be predicted | |
301 | well by the CPU. We should generate the pessimistic code by | |
302 | default, and have an option, e.g. -funsafe-loops that would | |
303 | enable count-register loops in this case. */ | |
304 | if (dump_file) | |
305 | fprintf (dump_file, "Doloop: Possible infinite iteration case.\n"); | |
7600f094 AP |
306 | result = false; |
307 | goto cleanup; | |
689ba89d ZD |
308 | } |
309 | ||
310 | for (i = 0; i < loop->num_nodes; i++) | |
311 | { | |
312 | bb = body[i]; | |
313 | ||
314 | for (insn = BB_HEAD (bb); | |
315 | insn != NEXT_INSN (BB_END (bb)); | |
316 | insn = NEXT_INSN (insn)) | |
317 | { | |
a71a498d AS |
318 | /* Different targets have different necessities for low-overhead |
319 | looping. Call the back end for each instruction within the loop | |
e7e64a25 AS |
320 | to let it decide whether the insn prohibits a low-overhead loop. |
321 | It will then return the cause for it to emit to the dump file. */ | |
322 | const char * invalid = targetm.invalid_within_doloop (insn); | |
323 | if (invalid) | |
324 | { | |
325 | if (dump_file) | |
326 | fprintf (dump_file, "Doloop: %s\n", invalid); | |
7600f094 AP |
327 | result = false; |
328 | goto cleanup; | |
e7e64a25 | 329 | } |
689ba89d ZD |
330 | } |
331 | } | |
7600f094 AP |
332 | result = true; |
333 | ||
334 | cleanup: | |
689ba89d ZD |
335 | free (body); |
336 | ||
7600f094 | 337 | return result; |
689ba89d ZD |
338 | } |
339 | ||
ed541ddb ZD |
340 | /* Adds test of COND jumping to DEST on edge *E and set *E to the new fallthru |
341 | edge. If the condition is always false, do not do anything. If it is always | |
342 | true, redirect E to DEST and return false. In all other cases, true is | |
343 | returned. */ | |
689ba89d | 344 | |
ed541ddb ZD |
345 | static bool |
346 | add_test (rtx cond, edge *e, basic_block dest) | |
689ba89d | 347 | { |
871eb193 | 348 | rtx_insn *seq, *jump; |
1476d1bd | 349 | rtx_code_label *label; |
ef4bddc2 | 350 | machine_mode mode; |
689ba89d ZD |
351 | rtx op0 = XEXP (cond, 0), op1 = XEXP (cond, 1); |
352 | enum rtx_code code = GET_CODE (cond); | |
ed541ddb | 353 | basic_block bb; |
689ba89d ZD |
354 | |
355 | mode = GET_MODE (XEXP (cond, 0)); | |
356 | if (mode == VOIDmode) | |
357 | mode = GET_MODE (XEXP (cond, 1)); | |
358 | ||
359 | start_sequence (); | |
360 | op0 = force_operand (op0, NULL_RTX); | |
361 | op1 = force_operand (op1, NULL_RTX); | |
362 | label = block_label (dest); | |
1476d1bd | 363 | do_compare_rtx_and_jump (op0, op1, code, 0, mode, NULL_RTX, NULL, label, -1); |
689ba89d ZD |
364 | |
365 | jump = get_last_insn (); | |
7d93d987 | 366 | if (!jump || !JUMP_P (jump)) |
f937df35 | 367 | { |
ed541ddb ZD |
368 | /* The condition is always false and the jump was optimized out. */ |
369 | end_sequence (); | |
370 | return true; | |
f937df35 | 371 | } |
689ba89d ZD |
372 | |
373 | seq = get_insns (); | |
374 | end_sequence (); | |
7d93d987 ZD |
375 | |
376 | /* There always is at least the jump insn in the sequence. */ | |
377 | gcc_assert (seq != NULL_RTX); | |
378 | ||
598ec7bd | 379 | bb = split_edge_and_insert (*e, seq); |
ed541ddb ZD |
380 | *e = single_succ_edge (bb); |
381 | ||
382 | if (any_uncondjump_p (jump)) | |
383 | { | |
384 | /* The condition is always true. */ | |
385 | delete_insn (jump); | |
386 | redirect_edge_and_branch_force (*e, dest); | |
387 | return false; | |
388 | } | |
b8698a0f | 389 | |
ed541ddb ZD |
390 | JUMP_LABEL (jump) = label; |
391 | ||
392 | /* The jump is supposed to handle an unlikely special case. */ | |
e5af9ddd | 393 | add_int_reg_note (jump, REG_BR_PROB, 0); |
65c5f2a6 | 394 | |
ed541ddb ZD |
395 | LABEL_NUSES (label)++; |
396 | ||
397 | make_edge (bb, dest, (*e)->flags & ~EDGE_FALLTHRU); | |
398 | return true; | |
689ba89d ZD |
399 | } |
400 | ||
401 | /* Modify the loop to use the low-overhead looping insn where LOOP | |
402 | describes the loop, DESC describes the number of iterations of the | |
403 | loop, and DOLOOP_INSN is the low-overhead looping insn to emit at the | |
404 | end of the loop. CONDITION is the condition separated from the | |
5f2e30ef | 405 | DOLOOP_SEQ. COUNT is the number of iterations of the LOOP. */ |
689ba89d ZD |
406 | |
407 | static void | |
408 | doloop_modify (struct loop *loop, struct niter_desc *desc, | |
89f7b21f | 409 | rtx_insn *doloop_seq, rtx condition, rtx count) |
689ba89d ZD |
410 | { |
411 | rtx counter_reg; | |
a82bbcbb | 412 | rtx tmp, noloop = NULL_RTX; |
871eb193 DM |
413 | rtx_insn *sequence; |
414 | rtx_insn *jump_insn; | |
1476d1bd | 415 | rtx_code_label *jump_label; |
ed541ddb | 416 | int nonneg = 0; |
689ba89d ZD |
417 | bool increment_count; |
418 | basic_block loop_end = desc->out_edge->src; | |
ef4bddc2 | 419 | machine_mode mode; |
80663107 | 420 | rtx true_prob_val; |
807e902e | 421 | widest_int iterations; |
689ba89d ZD |
422 | |
423 | jump_insn = BB_END (loop_end); | |
424 | ||
425 | if (dump_file) | |
426 | { | |
427 | fprintf (dump_file, "Doloop: Inserting doloop pattern ("); | |
428 | if (desc->const_iter) | |
16998094 | 429 | fprintf (dump_file, "%" PRId64, desc->niter); |
689ba89d ZD |
430 | else |
431 | fputs ("runtime", dump_file); | |
432 | fputs (" iterations).\n", dump_file); | |
433 | } | |
434 | ||
fa10beec | 435 | /* Get the probability of the original branch. If it exists we would |
80663107 MN |
436 | need to update REG_BR_PROB of the new jump_insn. */ |
437 | true_prob_val = find_reg_note (jump_insn, REG_BR_PROB, NULL_RTX); | |
438 | ||
689ba89d ZD |
439 | /* Discard original jump to continue loop. The original compare |
440 | result may still be live, so it cannot be discarded explicitly. */ | |
441 | delete_insn (jump_insn); | |
442 | ||
443 | counter_reg = XEXP (condition, 0); | |
444 | if (GET_CODE (counter_reg) == PLUS) | |
445 | counter_reg = XEXP (counter_reg, 0); | |
a82bbcbb | 446 | mode = GET_MODE (counter_reg); |
689ba89d | 447 | |
689ba89d ZD |
448 | increment_count = false; |
449 | switch (GET_CODE (condition)) | |
450 | { | |
451 | case NE: | |
452 | /* Currently only NE tests against zero and one are supported. */ | |
b5e624c6 NS |
453 | noloop = XEXP (condition, 1); |
454 | if (noloop != const0_rtx) | |
689ba89d | 455 | { |
b5e624c6 | 456 | gcc_assert (noloop == const1_rtx); |
689ba89d | 457 | increment_count = true; |
689ba89d | 458 | } |
689ba89d ZD |
459 | break; |
460 | ||
461 | case GE: | |
462 | /* Currently only GE tests against zero are supported. */ | |
b5e624c6 | 463 | gcc_assert (XEXP (condition, 1) == const0_rtx); |
689ba89d ZD |
464 | |
465 | noloop = constm1_rtx; | |
466 | ||
467 | /* The iteration count does not need incrementing for a GE test. */ | |
468 | increment_count = false; | |
469 | ||
470 | /* Determine if the iteration counter will be non-negative. | |
471 | Note that the maximum value loaded is iterations_max - 1. */ | |
2431114f | 472 | if (get_max_loop_iterations (loop, &iterations) |
807e902e KZ |
473 | && wi::leu_p (iterations, |
474 | wi::set_bit_in_zero <widest_int> | |
475 | (GET_MODE_PRECISION (mode) - 1))) | |
689ba89d ZD |
476 | nonneg = 1; |
477 | break; | |
478 | ||
1c43d3ca | 479 | /* Abort if an invalid doloop pattern has been generated. */ |
8127d0e0 | 480 | default: |
b5e624c6 | 481 | gcc_unreachable (); |
689ba89d ZD |
482 | } |
483 | ||
484 | if (increment_count) | |
5f2e30ef | 485 | count = simplify_gen_binary (PLUS, mode, count, const1_rtx); |
b2a38b1d | 486 | |
689ba89d ZD |
487 | /* Insert initialization of the count register into the loop header. */ |
488 | start_sequence (); | |
489 | tmp = force_operand (count, counter_reg); | |
490 | convert_move (counter_reg, tmp, 1); | |
491 | sequence = get_insns (); | |
492 | end_sequence (); | |
493 | emit_insn_after (sequence, BB_END (loop_preheader_edge (loop)->src)); | |
494 | ||
495 | if (desc->noloop_assumptions) | |
496 | { | |
30d3fc60 | 497 | rtx ass = copy_rtx (desc->noloop_assumptions); |
689ba89d ZD |
498 | basic_block preheader = loop_preheader_edge (loop)->src; |
499 | basic_block set_zero | |
598ec7bd | 500 | = split_edge (loop_preheader_edge (loop)); |
689ba89d | 501 | basic_block new_preheader |
598ec7bd | 502 | = split_edge (loop_preheader_edge (loop)); |
689ba89d | 503 | edge te; |
689ba89d ZD |
504 | |
505 | /* Expand the condition testing the assumptions and if it does not pass, | |
506 | reset the count register to 0. */ | |
ed541ddb | 507 | redirect_edge_and_branch_force (single_succ_edge (preheader), new_preheader); |
689ba89d ZD |
508 | set_immediate_dominator (CDI_DOMINATORS, new_preheader, preheader); |
509 | ||
510 | set_zero->count = 0; | |
511 | set_zero->frequency = 0; | |
512 | ||
ed541ddb ZD |
513 | te = single_succ_edge (preheader); |
514 | for (; ass; ass = XEXP (ass, 1)) | |
515 | if (!add_test (XEXP (ass, 0), &te, set_zero)) | |
516 | break; | |
517 | ||
518 | if (ass) | |
689ba89d | 519 | { |
ed541ddb ZD |
520 | /* We reached a condition that is always true. This is very hard to |
521 | reproduce (such a loop does not roll, and thus it would most | |
522 | likely get optimized out by some of the preceding optimizations). | |
523 | In fact, I do not have any testcase for it. However, it would | |
524 | also be very hard to show that it is impossible, so we must | |
525 | handle this case. */ | |
526 | set_zero->count = preheader->count; | |
527 | set_zero->frequency = preheader->frequency; | |
689ba89d | 528 | } |
b8698a0f | 529 | |
ed541ddb ZD |
530 | if (EDGE_COUNT (set_zero->preds) == 0) |
531 | { | |
532 | /* All the conditions were simplified to false, remove the | |
533 | unreachable set_zero block. */ | |
ed541ddb ZD |
534 | delete_basic_block (set_zero); |
535 | } | |
536 | else | |
537 | { | |
538 | /* Reset the counter to zero in the set_zero block. */ | |
539 | start_sequence (); | |
540 | convert_move (counter_reg, noloop, 0); | |
541 | sequence = get_insns (); | |
542 | end_sequence (); | |
543 | emit_insn_after (sequence, BB_END (set_zero)); | |
b8698a0f | 544 | |
ed541ddb | 545 | set_immediate_dominator (CDI_DOMINATORS, set_zero, |
66f97d31 ZD |
546 | recompute_dominator (CDI_DOMINATORS, |
547 | set_zero)); | |
ed541ddb ZD |
548 | } |
549 | ||
550 | set_immediate_dominator (CDI_DOMINATORS, new_preheader, | |
66f97d31 ZD |
551 | recompute_dominator (CDI_DOMINATORS, |
552 | new_preheader)); | |
689ba89d ZD |
553 | } |
554 | ||
555 | /* Some targets (eg, C4x) need to initialize special looping | |
556 | registers. */ | |
89f7b21f RS |
557 | if (targetm.have_doloop_begin ()) |
558 | if (rtx_insn *seq = targetm.gen_doloop_begin (counter_reg, doloop_seq)) | |
559 | emit_insn_after (seq, BB_END (loop_preheader_edge (loop)->src)); | |
689ba89d ZD |
560 | |
561 | /* Insert the new low-overhead looping insn. */ | |
562 | emit_jump_insn_after (doloop_seq, BB_END (loop_end)); | |
563 | jump_insn = BB_END (loop_end); | |
564 | jump_label = block_label (desc->in_edge->dest); | |
565 | JUMP_LABEL (jump_insn) = jump_label; | |
566 | LABEL_NUSES (jump_label)++; | |
567 | ||
568 | /* Ensure the right fallthru edge is marked, for case we have reversed | |
569 | the condition. */ | |
570 | desc->in_edge->flags &= ~EDGE_FALLTHRU; | |
571 | desc->out_edge->flags |= EDGE_FALLTHRU; | |
572 | ||
573 | /* Add a REG_NONNEG note if the actual or estimated maximum number | |
574 | of iterations is non-negative. */ | |
575 | if (nonneg) | |
65c5f2a6 ILT |
576 | add_reg_note (jump_insn, REG_NONNEG, NULL_RTX); |
577 | ||
80663107 MN |
578 | /* Update the REG_BR_PROB note. */ |
579 | if (true_prob_val) | |
580 | { | |
581 | /* Seems safer to use the branch probability. */ | |
e5af9ddd | 582 | add_int_reg_note (jump_insn, REG_BR_PROB, desc->in_edge->probability); |
80663107 | 583 | } |
689ba89d ZD |
584 | } |
585 | ||
586 | /* Process loop described by LOOP validating that the loop is suitable for | |
587 | conversion to use a low overhead looping instruction, replacing the jump | |
588 | insn where suitable. Returns true if the loop was successfully | |
589 | modified. */ | |
590 | ||
591 | static bool | |
592 | doloop_optimize (struct loop *loop) | |
593 | { | |
ef4bddc2 | 594 | machine_mode mode; |
89f7b21f | 595 | rtx doloop_reg; |
1d0216c8 | 596 | rtx count; |
807e902e | 597 | widest_int iterations, iterations_max; |
1476d1bd | 598 | rtx_code_label *start_label; |
689ba89d | 599 | rtx condition; |
7607bdda AT |
600 | unsigned level, est_niter; |
601 | int max_cost; | |
689ba89d | 602 | struct niter_desc *desc; |
a82bbcbb ZD |
603 | unsigned word_mode_size; |
604 | unsigned HOST_WIDE_INT word_mode_max; | |
2407343c | 605 | int entered_at_top; |
689ba89d ZD |
606 | |
607 | if (dump_file) | |
608 | fprintf (dump_file, "Doloop: Processing loop %d.\n", loop->num); | |
609 | ||
610 | iv_analysis_loop_init (loop); | |
611 | ||
612 | /* Find the simple exit of a LOOP. */ | |
613 | desc = get_simple_loop_desc (loop); | |
614 | ||
615 | /* Check that loop is a candidate for a low-overhead looping insn. */ | |
616 | if (!doloop_valid_p (loop, desc)) | |
617 | { | |
618 | if (dump_file) | |
619 | fprintf (dump_file, | |
620 | "Doloop: The loop is not suitable.\n"); | |
621 | return false; | |
622 | } | |
623 | mode = desc->mode; | |
624 | ||
625 | est_niter = 3; | |
626 | if (desc->const_iter) | |
627 | est_niter = desc->niter; | |
628 | /* If the estimate on number of iterations is reliable (comes from profile | |
629 | feedback), use it. Do not use it normally, since the expected number | |
630 | of iterations of an unrolled loop is 2. */ | |
631 | if (loop->header->count) | |
632 | est_niter = expected_loop_iterations (loop); | |
633 | ||
634 | if (est_niter < 3) | |
635 | { | |
636 | if (dump_file) | |
637 | fprintf (dump_file, | |
638 | "Doloop: Too few iterations (%u) to be profitable.\n", | |
639 | est_niter); | |
640 | return false; | |
641 | } | |
642 | ||
45b9a14b BS |
643 | max_cost |
644 | = COSTS_N_INSNS (PARAM_VALUE (PARAM_MAX_ITERATIONS_COMPUTATION_COST)); | |
e548c9df | 645 | if (set_src_cost (desc->niter_expr, mode, optimize_loop_for_speed_p (loop)) |
f40751dd | 646 | > max_cost) |
45b9a14b BS |
647 | { |
648 | if (dump_file) | |
649 | fprintf (dump_file, | |
405f0587 | 650 | "Doloop: number of iterations too costly to compute.\n"); |
45b9a14b BS |
651 | return false; |
652 | } | |
653 | ||
1d0216c8 | 654 | if (desc->const_iter) |
807e902e KZ |
655 | iterations = widest_int::from (std::make_pair (desc->niter_expr, mode), |
656 | UNSIGNED); | |
e3a8f1fa | 657 | else |
807e902e | 658 | iterations = 0; |
1d0216c8 | 659 | if (!get_max_loop_iterations (loop, &iterations_max)) |
807e902e | 660 | iterations_max = 0; |
689ba89d | 661 | level = get_loop_level (loop) + 1; |
1d0216c8 RS |
662 | entered_at_top = (loop->latch == desc->in_edge->dest |
663 | && contains_no_active_insn_p (loop->latch)); | |
664 | if (!targetm.can_use_doloop_p (iterations, iterations_max, level, | |
665 | entered_at_top)) | |
666 | { | |
667 | if (dump_file) | |
668 | fprintf (dump_file, "Loop rejected by can_use_doloop_p.\n"); | |
669 | return false; | |
670 | } | |
689ba89d ZD |
671 | |
672 | /* Generate looping insn. If the pattern FAILs then give up trying | |
673 | to modify the loop since there is some aspect the back-end does | |
674 | not like. */ | |
1d0216c8 | 675 | count = copy_rtx (desc->niter_expr); |
689ba89d ZD |
676 | start_label = block_label (desc->in_edge->dest); |
677 | doloop_reg = gen_reg_rtx (mode); | |
89f7b21f | 678 | rtx_insn *doloop_seq = targetm.gen_doloop_end (doloop_reg, start_label); |
a82bbcbb | 679 | |
5511bc5a | 680 | word_mode_size = GET_MODE_PRECISION (word_mode); |
a82bbcbb ZD |
681 | word_mode_max |
682 | = ((unsigned HOST_WIDE_INT) 1 << (word_mode_size - 1) << 1) - 1; | |
683 | if (! doloop_seq | |
684 | && mode != word_mode | |
685 | /* Before trying mode different from the one in that # of iterations is | |
686 | computed, we must be sure that the number of iterations fits into | |
687 | the new mode. */ | |
5511bc5a | 688 | && (word_mode_size >= GET_MODE_PRECISION (mode) |
807e902e | 689 | || wi::leu_p (iterations_max, word_mode_max))) |
689ba89d | 690 | { |
5511bc5a | 691 | if (word_mode_size > GET_MODE_PRECISION (mode)) |
1d0216c8 | 692 | count = simplify_gen_unary (ZERO_EXTEND, word_mode, count, mode); |
a82bbcbb | 693 | else |
1d0216c8 | 694 | count = lowpart_subreg (word_mode, count, mode); |
689ba89d | 695 | PUT_MODE (doloop_reg, word_mode); |
89f7b21f | 696 | doloop_seq = targetm.gen_doloop_end (doloop_reg, start_label); |
689ba89d ZD |
697 | } |
698 | if (! doloop_seq) | |
699 | { | |
700 | if (dump_file) | |
701 | fprintf (dump_file, | |
702 | "Doloop: Target unwilling to use doloop pattern!\n"); | |
703 | return false; | |
704 | } | |
705 | ||
706 | /* If multiple instructions were created, the last must be the | |
89f7b21f RS |
707 | jump instruction. */ |
708 | rtx_insn *doloop_insn = doloop_seq; | |
709 | while (NEXT_INSN (doloop_insn) != NULL_RTX) | |
710 | doloop_insn = NEXT_INSN (doloop_insn); | |
711 | if (!JUMP_P (doloop_insn) | |
712 | || !(condition = doloop_condition_get (doloop_insn))) | |
689ba89d ZD |
713 | { |
714 | if (dump_file) | |
715 | fprintf (dump_file, "Doloop: Unrecognizable doloop pattern!\n"); | |
716 | return false; | |
717 | } | |
718 | ||
5f2e30ef | 719 | doloop_modify (loop, desc, doloop_seq, condition, count); |
689ba89d ZD |
720 | return true; |
721 | } | |
722 | ||
d73be268 | 723 | /* This is the main entry point. Process all loops using doloop_optimize. */ |
689ba89d ZD |
724 | |
725 | void | |
d73be268 | 726 | doloop_optimize_loops (void) |
689ba89d | 727 | { |
689ba89d ZD |
728 | struct loop *loop; |
729 | ||
fdbbed34 | 730 | FOR_EACH_LOOP (loop, 0) |
689ba89d | 731 | { |
689ba89d ZD |
732 | doloop_optimize (loop); |
733 | } | |
734 | ||
735 | iv_analysis_done (); | |
736 | ||
737 | #ifdef ENABLE_CHECKING | |
d73be268 | 738 | verify_loop_structure (); |
689ba89d ZD |
739 | #endif |
740 | } |