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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" | |
24 | #include "tm.h" | |
25 | #include "rtl.h" | |
26 | #include "flags.h" | |
40e23961 | 27 | #include "symtab.h" |
60393bbc AM |
28 | #include "hashtab.h" |
29 | #include "hash-set.h" | |
36566b39 | 30 | #include "vec.h" |
60393bbc | 31 | #include "machmode.h" |
36566b39 | 32 | #include "hard-reg-set.h" |
60393bbc AM |
33 | #include "input.h" |
34 | #include "function.h" | |
36566b39 PK |
35 | #include "statistics.h" |
36 | #include "double-int.h" | |
37 | #include "real.h" | |
38 | #include "fixed-value.h" | |
39 | #include "alias.h" | |
40 | #include "wide-int.h" | |
41 | #include "inchash.h" | |
42 | #include "tree.h" | |
43 | #include "insn-config.h" | |
44 | #include "expmed.h" | |
45 | #include "dojump.h" | |
46 | #include "explow.h" | |
47 | #include "calls.h" | |
48 | #include "emit-rtl.h" | |
49 | #include "varasm.h" | |
50 | #include "stmt.h" | |
51 | #include "expr.h" | |
718f9c0f | 52 | #include "diagnostic-core.h" |
689ba89d | 53 | #include "tm_p.h" |
60393bbc AM |
54 | #include "predict.h" |
55 | #include "dominance.h" | |
56 | #include "cfg.h" | |
689ba89d | 57 | #include "cfgloop.h" |
60393bbc AM |
58 | #include "cfgrtl.h" |
59 | #include "basic-block.h" | |
689ba89d | 60 | #include "params.h" |
a71a498d | 61 | #include "target.h" |
7ee2468b | 62 | #include "dumpfile.h" |
50684f95 | 63 | #include "loop-unroll.h" |
689ba89d ZD |
64 | |
65 | /* This module is used to modify loops with a determinable number of | |
66 | iterations to use special low-overhead looping instructions. | |
67 | ||
68 | It first validates whether the loop is well behaved and has a | |
69 | determinable number of iterations (either at compile or run-time). | |
70 | It then modifies the loop to use a low-overhead looping pattern as | |
71 | follows: | |
72 | ||
73 | 1. A pseudo register is allocated as the loop iteration counter. | |
74 | ||
75 | 2. The number of loop iterations is calculated and is stored | |
76 | in the loop counter. | |
77 | ||
78 | 3. At the end of the loop, the jump insn is replaced by the | |
79 | doloop_end pattern. The compare must remain because it might be | |
80 | used elsewhere. If the loop-variable or condition register are | |
81 | used elsewhere, they will be eliminated by flow. | |
82 | ||
83 | 4. An optional doloop_begin pattern is inserted at the top of the | |
84 | loop. | |
85 | ||
86 | TODO The optimization should only performed when either the biv used for exit | |
87 | condition is unused at all except for the exit test, or if we do not have to | |
88 | change its value, since otherwise we have to add a new induction variable, | |
89 | which usually will not pay up (unless the cost of the doloop pattern is | |
90 | somehow extremely lower than the cost of compare & jump, or unless the bct | |
91 | register cannot be used for anything else but doloop -- ??? detect these | |
92 | cases). */ | |
93 | ||
94 | #ifdef HAVE_doloop_end | |
95 | ||
96 | /* Return the loop termination condition for PATTERN or zero | |
97 | if it is not a decrement and branch jump insn. */ | |
98 | ||
75c70254 | 99 | rtx |
46dc0789 | 100 | doloop_condition_get (rtx doloop_pat) |
689ba89d ZD |
101 | { |
102 | rtx cmp; | |
103 | rtx inc; | |
104 | rtx reg; | |
75c70254 | 105 | rtx inc_src; |
689ba89d | 106 | rtx condition; |
46dc0789 | 107 | rtx pattern; |
ce7b3761 RE |
108 | rtx cc_reg = NULL_RTX; |
109 | rtx reg_orig = NULL_RTX; | |
689ba89d | 110 | |
46dc0789 MN |
111 | /* The canonical doloop pattern we expect has one of the following |
112 | forms: | |
689ba89d | 113 | |
46dc0789 MN |
114 | 1) (parallel [(set (pc) (if_then_else (condition) |
115 | (label_ref (label)) | |
116 | (pc))) | |
117 | (set (reg) (plus (reg) (const_int -1))) | |
118 | (additional clobbers and uses)]) | |
689ba89d | 119 | |
46dc0789 MN |
120 | The branch must be the first entry of the parallel (also required |
121 | by jump.c), and the second entry of the parallel must be a set of | |
122 | the loop counter register. Some targets (IA-64) wrap the set of | |
123 | the loop counter in an if_then_else too. | |
75c70254 | 124 | |
46dc0789 MN |
125 | 2) (set (reg) (plus (reg) (const_int -1)) |
126 | (set (pc) (if_then_else (reg != 0) | |
127 | (label_ref (label)) | |
ce7b3761 RE |
128 | (pc))). |
129 | ||
130 | Some targets (ARM) do the comparison before the branch, as in the | |
131 | following form: | |
132 | ||
133 | 3) (parallel [(set (cc) (compare ((plus (reg) (const_int -1), 0))) | |
134 | (set (reg) (plus (reg) (const_int -1)))]) | |
135 | (set (pc) (if_then_else (cc == NE) | |
136 | (label_ref (label)) | |
137 | (pc))) */ | |
46dc0789 MN |
138 | |
139 | pattern = PATTERN (doloop_pat); | |
689ba89d ZD |
140 | |
141 | if (GET_CODE (pattern) != PARALLEL) | |
46dc0789 MN |
142 | { |
143 | rtx cond; | |
21afc57d | 144 | rtx_insn *prev_insn = prev_nondebug_insn (doloop_pat); |
ce7b3761 RE |
145 | rtx cmp_arg1, cmp_arg2; |
146 | rtx cmp_orig; | |
46dc0789 | 147 | |
ce7b3761 RE |
148 | /* In case the pattern is not PARALLEL we expect two forms |
149 | of doloop which are cases 2) and 3) above: in case 2) the | |
150 | decrement immediately precedes the branch, while in case 3) | |
151 | the compare and decrement instructions immediately precede | |
152 | the branch. */ | |
689ba89d | 153 | |
0be955e7 | 154 | if (prev_insn == NULL_RTX || !INSN_P (prev_insn)) |
46dc0789 MN |
155 | return 0; |
156 | ||
157 | cmp = pattern; | |
ce7b3761 RE |
158 | if (GET_CODE (PATTERN (prev_insn)) == PARALLEL) |
159 | { | |
160 | /* The third case: the compare and decrement instructions | |
161 | immediately precede the branch. */ | |
162 | cmp_orig = XVECEXP (PATTERN (prev_insn), 0, 0); | |
163 | if (GET_CODE (cmp_orig) != SET) | |
164 | return 0; | |
165 | if (GET_CODE (SET_SRC (cmp_orig)) != COMPARE) | |
166 | return 0; | |
167 | cmp_arg1 = XEXP (SET_SRC (cmp_orig), 0); | |
168 | cmp_arg2 = XEXP (SET_SRC (cmp_orig), 1); | |
169 | if (cmp_arg2 != const0_rtx | |
170 | || GET_CODE (cmp_arg1) != PLUS) | |
171 | return 0; | |
172 | reg_orig = XEXP (cmp_arg1, 0); | |
173 | if (XEXP (cmp_arg1, 1) != GEN_INT (-1) | |
174 | || !REG_P (reg_orig)) | |
175 | return 0; | |
176 | cc_reg = SET_DEST (cmp_orig); | |
177 | ||
178 | inc = XVECEXP (PATTERN (prev_insn), 0, 1); | |
179 | } | |
180 | else | |
b8abece3 | 181 | inc = PATTERN (prev_insn); |
46dc0789 MN |
182 | /* We expect the condition to be of the form (reg != 0) */ |
183 | cond = XEXP (SET_SRC (cmp), 0); | |
184 | if (GET_CODE (cond) != NE || XEXP (cond, 1) != const0_rtx) | |
185 | return 0; | |
46dc0789 MN |
186 | } |
187 | else | |
188 | { | |
189 | cmp = XVECEXP (pattern, 0, 0); | |
190 | inc = XVECEXP (pattern, 0, 1); | |
191 | } | |
689ba89d ZD |
192 | |
193 | /* Check for (set (reg) (something)). */ | |
75c70254 | 194 | if (GET_CODE (inc) != SET) |
689ba89d | 195 | return 0; |
689ba89d | 196 | reg = SET_DEST (inc); |
75c70254 SB |
197 | if (! REG_P (reg)) |
198 | return 0; | |
199 | ||
200 | /* Check if something = (plus (reg) (const_int -1)). | |
201 | On IA-64, this decrement is wrapped in an if_then_else. */ | |
202 | inc_src = SET_SRC (inc); | |
203 | if (GET_CODE (inc_src) == IF_THEN_ELSE) | |
204 | inc_src = XEXP (inc_src, 1); | |
205 | if (GET_CODE (inc_src) != PLUS | |
206 | || XEXP (inc_src, 0) != reg | |
207 | || XEXP (inc_src, 1) != constm1_rtx) | |
208 | return 0; | |
689ba89d ZD |
209 | |
210 | /* Check for (set (pc) (if_then_else (condition) | |
211 | (label_ref (label)) | |
212 | (pc))). */ | |
213 | if (GET_CODE (cmp) != SET | |
214 | || SET_DEST (cmp) != pc_rtx | |
215 | || GET_CODE (SET_SRC (cmp)) != IF_THEN_ELSE | |
216 | || GET_CODE (XEXP (SET_SRC (cmp), 1)) != LABEL_REF | |
217 | || XEXP (SET_SRC (cmp), 2) != pc_rtx) | |
218 | return 0; | |
219 | ||
220 | /* Extract loop termination condition. */ | |
221 | condition = XEXP (SET_SRC (cmp), 0); | |
222 | ||
75c70254 SB |
223 | /* We expect a GE or NE comparison with 0 or 1. */ |
224 | if ((GET_CODE (condition) != GE | |
225 | && GET_CODE (condition) != NE) | |
226 | || (XEXP (condition, 1) != const0_rtx | |
227 | && XEXP (condition, 1) != const1_rtx)) | |
689ba89d ZD |
228 | return 0; |
229 | ||
75c70254 | 230 | if ((XEXP (condition, 0) == reg) |
ce7b3761 RE |
231 | /* For the third case: */ |
232 | || ((cc_reg != NULL_RTX) | |
233 | && (XEXP (condition, 0) == cc_reg) | |
234 | && (reg_orig == reg)) | |
75c70254 | 235 | || (GET_CODE (XEXP (condition, 0)) == PLUS |
ce7b3761 | 236 | && XEXP (XEXP (condition, 0), 0) == reg)) |
46dc0789 MN |
237 | { |
238 | if (GET_CODE (pattern) != PARALLEL) | |
ce7b3761 | 239 | /* For the second form we expect: |
46dc0789 MN |
240 | |
241 | (set (reg) (plus (reg) (const_int -1)) | |
242 | (set (pc) (if_then_else (reg != 0) | |
243 | (label_ref (label)) | |
244 | (pc))). | |
245 | ||
246 | is equivalent to the following: | |
247 | ||
248 | (parallel [(set (pc) (if_then_else (reg != 1) | |
249 | (label_ref (label)) | |
250 | (pc))) | |
251 | (set (reg) (plus (reg) (const_int -1))) | |
252 | (additional clobbers and uses)]) | |
253 | ||
ce7b3761 RE |
254 | For the third form we expect: |
255 | ||
256 | (parallel [(set (cc) (compare ((plus (reg) (const_int -1)), 0)) | |
257 | (set (reg) (plus (reg) (const_int -1)))]) | |
258 | (set (pc) (if_then_else (cc == NE) | |
259 | (label_ref (label)) | |
260 | (pc))) | |
261 | ||
262 | which is equivalent to the following: | |
263 | ||
264 | (parallel [(set (cc) (compare (reg, 1)) | |
265 | (set (reg) (plus (reg) (const_int -1))) | |
266 | (set (pc) (if_then_else (NE == cc) | |
267 | (label_ref (label)) | |
268 | (pc))))]) | |
269 | ||
270 | So we return the second form instead for the two cases. | |
271 | ||
46dc0789 MN |
272 | */ |
273 | condition = gen_rtx_fmt_ee (NE, VOIDmode, inc_src, const1_rtx); | |
274 | ||
689ba89d | 275 | return condition; |
46dc0789 | 276 | } |
689ba89d ZD |
277 | |
278 | /* ??? If a machine uses a funny comparison, we could return a | |
1ae58c30 | 279 | canonicalized form here. */ |
689ba89d ZD |
280 | |
281 | return 0; | |
282 | } | |
283 | ||
284 | /* Return nonzero if the loop specified by LOOP is suitable for | |
285 | the use of special low-overhead looping instructions. DESC | |
286 | describes the number of iterations of the loop. */ | |
287 | ||
288 | static bool | |
289 | doloop_valid_p (struct loop *loop, struct niter_desc *desc) | |
290 | { | |
291 | basic_block *body = get_loop_body (loop), bb; | |
871eb193 | 292 | rtx_insn *insn; |
689ba89d | 293 | unsigned i; |
7600f094 | 294 | bool result = true; |
689ba89d ZD |
295 | |
296 | /* Check for loops that may not terminate under special conditions. */ | |
297 | if (!desc->simple_p | |
298 | || desc->assumptions | |
299 | || desc->infinite) | |
300 | { | |
301 | /* There are some cases that would require a special attention. | |
302 | For example if the comparison is LEU and the comparison value | |
303 | is UINT_MAX then the loop will not terminate. Similarly, if the | |
304 | comparison code is GEU and the comparison value is 0, the | |
305 | loop will not terminate. | |
306 | ||
307 | If the absolute increment is not 1, the loop can be infinite | |
308 | even with LTU/GTU, e.g. for (i = 3; i > 0; i -= 2) | |
309 | ||
310 | ??? We could compute these conditions at run-time and have a | |
311 | additional jump around the loop to ensure an infinite loop. | |
312 | However, it is very unlikely that this is the intended | |
313 | behavior of the loop and checking for these rare boundary | |
314 | conditions would pessimize all other code. | |
315 | ||
316 | If the loop is executed only a few times an extra check to | |
317 | restart the loop could use up most of the benefits of using a | |
318 | count register loop. Note however, that normally, this | |
319 | restart branch would never execute, so it could be predicted | |
320 | well by the CPU. We should generate the pessimistic code by | |
321 | default, and have an option, e.g. -funsafe-loops that would | |
322 | enable count-register loops in this case. */ | |
323 | if (dump_file) | |
324 | fprintf (dump_file, "Doloop: Possible infinite iteration case.\n"); | |
7600f094 AP |
325 | result = false; |
326 | goto cleanup; | |
689ba89d ZD |
327 | } |
328 | ||
329 | for (i = 0; i < loop->num_nodes; i++) | |
330 | { | |
331 | bb = body[i]; | |
332 | ||
333 | for (insn = BB_HEAD (bb); | |
334 | insn != NEXT_INSN (BB_END (bb)); | |
335 | insn = NEXT_INSN (insn)) | |
336 | { | |
a71a498d AS |
337 | /* Different targets have different necessities for low-overhead |
338 | looping. Call the back end for each instruction within the loop | |
e7e64a25 AS |
339 | to let it decide whether the insn prohibits a low-overhead loop. |
340 | It will then return the cause for it to emit to the dump file. */ | |
341 | const char * invalid = targetm.invalid_within_doloop (insn); | |
342 | if (invalid) | |
343 | { | |
344 | if (dump_file) | |
345 | fprintf (dump_file, "Doloop: %s\n", invalid); | |
7600f094 AP |
346 | result = false; |
347 | goto cleanup; | |
e7e64a25 | 348 | } |
689ba89d ZD |
349 | } |
350 | } | |
7600f094 AP |
351 | result = true; |
352 | ||
353 | cleanup: | |
689ba89d ZD |
354 | free (body); |
355 | ||
7600f094 | 356 | return result; |
689ba89d ZD |
357 | } |
358 | ||
ed541ddb ZD |
359 | /* Adds test of COND jumping to DEST on edge *E and set *E to the new fallthru |
360 | edge. If the condition is always false, do not do anything. If it is always | |
361 | true, redirect E to DEST and return false. In all other cases, true is | |
362 | returned. */ | |
689ba89d | 363 | |
ed541ddb ZD |
364 | static bool |
365 | add_test (rtx cond, edge *e, basic_block dest) | |
689ba89d | 366 | { |
871eb193 DM |
367 | rtx_insn *seq, *jump; |
368 | rtx label; | |
ef4bddc2 | 369 | machine_mode mode; |
689ba89d ZD |
370 | rtx op0 = XEXP (cond, 0), op1 = XEXP (cond, 1); |
371 | enum rtx_code code = GET_CODE (cond); | |
ed541ddb | 372 | basic_block bb; |
689ba89d ZD |
373 | |
374 | mode = GET_MODE (XEXP (cond, 0)); | |
375 | if (mode == VOIDmode) | |
376 | mode = GET_MODE (XEXP (cond, 1)); | |
377 | ||
378 | start_sequence (); | |
379 | op0 = force_operand (op0, NULL_RTX); | |
380 | op1 = force_operand (op1, NULL_RTX); | |
381 | label = block_label (dest); | |
2bdd49f4 JJ |
382 | do_compare_rtx_and_jump (op0, op1, code, 0, mode, NULL_RTX, |
383 | NULL_RTX, label, -1); | |
689ba89d ZD |
384 | |
385 | jump = get_last_insn (); | |
7d93d987 | 386 | if (!jump || !JUMP_P (jump)) |
f937df35 | 387 | { |
ed541ddb ZD |
388 | /* The condition is always false and the jump was optimized out. */ |
389 | end_sequence (); | |
390 | return true; | |
f937df35 | 391 | } |
689ba89d ZD |
392 | |
393 | seq = get_insns (); | |
394 | end_sequence (); | |
7d93d987 ZD |
395 | |
396 | /* There always is at least the jump insn in the sequence. */ | |
397 | gcc_assert (seq != NULL_RTX); | |
398 | ||
598ec7bd | 399 | bb = split_edge_and_insert (*e, seq); |
ed541ddb ZD |
400 | *e = single_succ_edge (bb); |
401 | ||
402 | if (any_uncondjump_p (jump)) | |
403 | { | |
404 | /* The condition is always true. */ | |
405 | delete_insn (jump); | |
406 | redirect_edge_and_branch_force (*e, dest); | |
407 | return false; | |
408 | } | |
b8698a0f | 409 | |
ed541ddb ZD |
410 | JUMP_LABEL (jump) = label; |
411 | ||
412 | /* The jump is supposed to handle an unlikely special case. */ | |
e5af9ddd | 413 | add_int_reg_note (jump, REG_BR_PROB, 0); |
65c5f2a6 | 414 | |
ed541ddb ZD |
415 | LABEL_NUSES (label)++; |
416 | ||
417 | make_edge (bb, dest, (*e)->flags & ~EDGE_FALLTHRU); | |
418 | return true; | |
689ba89d ZD |
419 | } |
420 | ||
421 | /* Modify the loop to use the low-overhead looping insn where LOOP | |
422 | describes the loop, DESC describes the number of iterations of the | |
423 | loop, and DOLOOP_INSN is the low-overhead looping insn to emit at the | |
424 | end of the loop. CONDITION is the condition separated from the | |
5f2e30ef | 425 | DOLOOP_SEQ. COUNT is the number of iterations of the LOOP. */ |
689ba89d ZD |
426 | |
427 | static void | |
428 | doloop_modify (struct loop *loop, struct niter_desc *desc, | |
5f2e30ef | 429 | rtx doloop_seq, rtx condition, rtx count) |
689ba89d ZD |
430 | { |
431 | rtx counter_reg; | |
a82bbcbb | 432 | rtx tmp, noloop = NULL_RTX; |
871eb193 DM |
433 | rtx_insn *sequence; |
434 | rtx_insn *jump_insn; | |
689ba89d | 435 | rtx jump_label; |
ed541ddb | 436 | int nonneg = 0; |
689ba89d ZD |
437 | bool increment_count; |
438 | basic_block loop_end = desc->out_edge->src; | |
ef4bddc2 | 439 | machine_mode mode; |
80663107 | 440 | rtx true_prob_val; |
807e902e | 441 | widest_int iterations; |
689ba89d ZD |
442 | |
443 | jump_insn = BB_END (loop_end); | |
444 | ||
445 | if (dump_file) | |
446 | { | |
447 | fprintf (dump_file, "Doloop: Inserting doloop pattern ("); | |
448 | if (desc->const_iter) | |
16998094 | 449 | fprintf (dump_file, "%" PRId64, desc->niter); |
689ba89d ZD |
450 | else |
451 | fputs ("runtime", dump_file); | |
452 | fputs (" iterations).\n", dump_file); | |
453 | } | |
454 | ||
fa10beec | 455 | /* Get the probability of the original branch. If it exists we would |
80663107 MN |
456 | need to update REG_BR_PROB of the new jump_insn. */ |
457 | true_prob_val = find_reg_note (jump_insn, REG_BR_PROB, NULL_RTX); | |
458 | ||
689ba89d ZD |
459 | /* Discard original jump to continue loop. The original compare |
460 | result may still be live, so it cannot be discarded explicitly. */ | |
461 | delete_insn (jump_insn); | |
462 | ||
463 | counter_reg = XEXP (condition, 0); | |
464 | if (GET_CODE (counter_reg) == PLUS) | |
465 | counter_reg = XEXP (counter_reg, 0); | |
a82bbcbb | 466 | mode = GET_MODE (counter_reg); |
689ba89d | 467 | |
689ba89d ZD |
468 | increment_count = false; |
469 | switch (GET_CODE (condition)) | |
470 | { | |
471 | case NE: | |
472 | /* Currently only NE tests against zero and one are supported. */ | |
b5e624c6 NS |
473 | noloop = XEXP (condition, 1); |
474 | if (noloop != const0_rtx) | |
689ba89d | 475 | { |
b5e624c6 | 476 | gcc_assert (noloop == const1_rtx); |
689ba89d | 477 | increment_count = true; |
689ba89d | 478 | } |
689ba89d ZD |
479 | break; |
480 | ||
481 | case GE: | |
482 | /* Currently only GE tests against zero are supported. */ | |
b5e624c6 | 483 | gcc_assert (XEXP (condition, 1) == const0_rtx); |
689ba89d ZD |
484 | |
485 | noloop = constm1_rtx; | |
486 | ||
487 | /* The iteration count does not need incrementing for a GE test. */ | |
488 | increment_count = false; | |
489 | ||
490 | /* Determine if the iteration counter will be non-negative. | |
491 | Note that the maximum value loaded is iterations_max - 1. */ | |
2431114f | 492 | if (get_max_loop_iterations (loop, &iterations) |
807e902e KZ |
493 | && wi::leu_p (iterations, |
494 | wi::set_bit_in_zero <widest_int> | |
495 | (GET_MODE_PRECISION (mode) - 1))) | |
689ba89d ZD |
496 | nonneg = 1; |
497 | break; | |
498 | ||
1c43d3ca | 499 | /* Abort if an invalid doloop pattern has been generated. */ |
8127d0e0 | 500 | default: |
b5e624c6 | 501 | gcc_unreachable (); |
689ba89d ZD |
502 | } |
503 | ||
504 | if (increment_count) | |
5f2e30ef | 505 | count = simplify_gen_binary (PLUS, mode, count, const1_rtx); |
b2a38b1d | 506 | |
689ba89d ZD |
507 | /* Insert initialization of the count register into the loop header. */ |
508 | start_sequence (); | |
509 | tmp = force_operand (count, counter_reg); | |
510 | convert_move (counter_reg, tmp, 1); | |
511 | sequence = get_insns (); | |
512 | end_sequence (); | |
513 | emit_insn_after (sequence, BB_END (loop_preheader_edge (loop)->src)); | |
514 | ||
515 | if (desc->noloop_assumptions) | |
516 | { | |
30d3fc60 | 517 | rtx ass = copy_rtx (desc->noloop_assumptions); |
689ba89d ZD |
518 | basic_block preheader = loop_preheader_edge (loop)->src; |
519 | basic_block set_zero | |
598ec7bd | 520 | = split_edge (loop_preheader_edge (loop)); |
689ba89d | 521 | basic_block new_preheader |
598ec7bd | 522 | = split_edge (loop_preheader_edge (loop)); |
689ba89d | 523 | edge te; |
689ba89d ZD |
524 | |
525 | /* Expand the condition testing the assumptions and if it does not pass, | |
526 | reset the count register to 0. */ | |
ed541ddb | 527 | redirect_edge_and_branch_force (single_succ_edge (preheader), new_preheader); |
689ba89d ZD |
528 | set_immediate_dominator (CDI_DOMINATORS, new_preheader, preheader); |
529 | ||
530 | set_zero->count = 0; | |
531 | set_zero->frequency = 0; | |
532 | ||
ed541ddb ZD |
533 | te = single_succ_edge (preheader); |
534 | for (; ass; ass = XEXP (ass, 1)) | |
535 | if (!add_test (XEXP (ass, 0), &te, set_zero)) | |
536 | break; | |
537 | ||
538 | if (ass) | |
689ba89d | 539 | { |
ed541ddb ZD |
540 | /* We reached a condition that is always true. This is very hard to |
541 | reproduce (such a loop does not roll, and thus it would most | |
542 | likely get optimized out by some of the preceding optimizations). | |
543 | In fact, I do not have any testcase for it. However, it would | |
544 | also be very hard to show that it is impossible, so we must | |
545 | handle this case. */ | |
546 | set_zero->count = preheader->count; | |
547 | set_zero->frequency = preheader->frequency; | |
689ba89d | 548 | } |
b8698a0f | 549 | |
ed541ddb ZD |
550 | if (EDGE_COUNT (set_zero->preds) == 0) |
551 | { | |
552 | /* All the conditions were simplified to false, remove the | |
553 | unreachable set_zero block. */ | |
ed541ddb ZD |
554 | delete_basic_block (set_zero); |
555 | } | |
556 | else | |
557 | { | |
558 | /* Reset the counter to zero in the set_zero block. */ | |
559 | start_sequence (); | |
560 | convert_move (counter_reg, noloop, 0); | |
561 | sequence = get_insns (); | |
562 | end_sequence (); | |
563 | emit_insn_after (sequence, BB_END (set_zero)); | |
b8698a0f | 564 | |
ed541ddb | 565 | set_immediate_dominator (CDI_DOMINATORS, set_zero, |
66f97d31 ZD |
566 | recompute_dominator (CDI_DOMINATORS, |
567 | set_zero)); | |
ed541ddb ZD |
568 | } |
569 | ||
570 | set_immediate_dominator (CDI_DOMINATORS, new_preheader, | |
66f97d31 ZD |
571 | recompute_dominator (CDI_DOMINATORS, |
572 | new_preheader)); | |
689ba89d ZD |
573 | } |
574 | ||
575 | /* Some targets (eg, C4x) need to initialize special looping | |
576 | registers. */ | |
577 | #ifdef HAVE_doloop_begin | |
578 | { | |
579 | rtx init; | |
1d0216c8 RS |
580 | |
581 | init = gen_doloop_begin (counter_reg, doloop_seq); | |
689ba89d ZD |
582 | if (init) |
583 | { | |
584 | start_sequence (); | |
585 | emit_insn (init); | |
586 | sequence = get_insns (); | |
587 | end_sequence (); | |
588 | emit_insn_after (sequence, BB_END (loop_preheader_edge (loop)->src)); | |
589 | } | |
590 | } | |
591 | #endif | |
592 | ||
593 | /* Insert the new low-overhead looping insn. */ | |
594 | emit_jump_insn_after (doloop_seq, BB_END (loop_end)); | |
595 | jump_insn = BB_END (loop_end); | |
596 | jump_label = block_label (desc->in_edge->dest); | |
597 | JUMP_LABEL (jump_insn) = jump_label; | |
598 | LABEL_NUSES (jump_label)++; | |
599 | ||
600 | /* Ensure the right fallthru edge is marked, for case we have reversed | |
601 | the condition. */ | |
602 | desc->in_edge->flags &= ~EDGE_FALLTHRU; | |
603 | desc->out_edge->flags |= EDGE_FALLTHRU; | |
604 | ||
605 | /* Add a REG_NONNEG note if the actual or estimated maximum number | |
606 | of iterations is non-negative. */ | |
607 | if (nonneg) | |
65c5f2a6 ILT |
608 | add_reg_note (jump_insn, REG_NONNEG, NULL_RTX); |
609 | ||
80663107 MN |
610 | /* Update the REG_BR_PROB note. */ |
611 | if (true_prob_val) | |
612 | { | |
613 | /* Seems safer to use the branch probability. */ | |
e5af9ddd | 614 | add_int_reg_note (jump_insn, REG_BR_PROB, desc->in_edge->probability); |
80663107 | 615 | } |
689ba89d ZD |
616 | } |
617 | ||
618 | /* Process loop described by LOOP validating that the loop is suitable for | |
619 | conversion to use a low overhead looping instruction, replacing the jump | |
620 | insn where suitable. Returns true if the loop was successfully | |
621 | modified. */ | |
622 | ||
623 | static bool | |
624 | doloop_optimize (struct loop *loop) | |
625 | { | |
ef4bddc2 | 626 | machine_mode mode; |
689ba89d | 627 | rtx doloop_seq, doloop_pat, doloop_reg; |
1d0216c8 | 628 | rtx count; |
807e902e | 629 | widest_int iterations, iterations_max; |
689ba89d ZD |
630 | rtx start_label; |
631 | rtx condition; | |
7607bdda AT |
632 | unsigned level, est_niter; |
633 | int max_cost; | |
689ba89d | 634 | struct niter_desc *desc; |
a82bbcbb ZD |
635 | unsigned word_mode_size; |
636 | unsigned HOST_WIDE_INT word_mode_max; | |
2407343c | 637 | int entered_at_top; |
689ba89d ZD |
638 | |
639 | if (dump_file) | |
640 | fprintf (dump_file, "Doloop: Processing loop %d.\n", loop->num); | |
641 | ||
642 | iv_analysis_loop_init (loop); | |
643 | ||
644 | /* Find the simple exit of a LOOP. */ | |
645 | desc = get_simple_loop_desc (loop); | |
646 | ||
647 | /* Check that loop is a candidate for a low-overhead looping insn. */ | |
648 | if (!doloop_valid_p (loop, desc)) | |
649 | { | |
650 | if (dump_file) | |
651 | fprintf (dump_file, | |
652 | "Doloop: The loop is not suitable.\n"); | |
653 | return false; | |
654 | } | |
655 | mode = desc->mode; | |
656 | ||
657 | est_niter = 3; | |
658 | if (desc->const_iter) | |
659 | est_niter = desc->niter; | |
660 | /* If the estimate on number of iterations is reliable (comes from profile | |
661 | feedback), use it. Do not use it normally, since the expected number | |
662 | of iterations of an unrolled loop is 2. */ | |
663 | if (loop->header->count) | |
664 | est_niter = expected_loop_iterations (loop); | |
665 | ||
666 | if (est_niter < 3) | |
667 | { | |
668 | if (dump_file) | |
669 | fprintf (dump_file, | |
670 | "Doloop: Too few iterations (%u) to be profitable.\n", | |
671 | est_niter); | |
672 | return false; | |
673 | } | |
674 | ||
45b9a14b BS |
675 | max_cost |
676 | = COSTS_N_INSNS (PARAM_VALUE (PARAM_MAX_ITERATIONS_COMPUTATION_COST)); | |
5e8f01f4 | 677 | if (set_src_cost (desc->niter_expr, optimize_loop_for_speed_p (loop)) |
f40751dd | 678 | > max_cost) |
45b9a14b BS |
679 | { |
680 | if (dump_file) | |
681 | fprintf (dump_file, | |
405f0587 | 682 | "Doloop: number of iterations too costly to compute.\n"); |
45b9a14b BS |
683 | return false; |
684 | } | |
685 | ||
1d0216c8 | 686 | if (desc->const_iter) |
807e902e KZ |
687 | iterations = widest_int::from (std::make_pair (desc->niter_expr, mode), |
688 | UNSIGNED); | |
e3a8f1fa | 689 | else |
807e902e | 690 | iterations = 0; |
1d0216c8 | 691 | if (!get_max_loop_iterations (loop, &iterations_max)) |
807e902e | 692 | iterations_max = 0; |
689ba89d | 693 | level = get_loop_level (loop) + 1; |
1d0216c8 RS |
694 | entered_at_top = (loop->latch == desc->in_edge->dest |
695 | && contains_no_active_insn_p (loop->latch)); | |
696 | if (!targetm.can_use_doloop_p (iterations, iterations_max, level, | |
697 | entered_at_top)) | |
698 | { | |
699 | if (dump_file) | |
700 | fprintf (dump_file, "Loop rejected by can_use_doloop_p.\n"); | |
701 | return false; | |
702 | } | |
689ba89d ZD |
703 | |
704 | /* Generate looping insn. If the pattern FAILs then give up trying | |
705 | to modify the loop since there is some aspect the back-end does | |
706 | not like. */ | |
1d0216c8 | 707 | count = copy_rtx (desc->niter_expr); |
689ba89d ZD |
708 | start_label = block_label (desc->in_edge->dest); |
709 | doloop_reg = gen_reg_rtx (mode); | |
1d0216c8 | 710 | doloop_seq = gen_doloop_end (doloop_reg, start_label); |
a82bbcbb | 711 | |
5511bc5a | 712 | word_mode_size = GET_MODE_PRECISION (word_mode); |
a82bbcbb ZD |
713 | word_mode_max |
714 | = ((unsigned HOST_WIDE_INT) 1 << (word_mode_size - 1) << 1) - 1; | |
715 | if (! doloop_seq | |
716 | && mode != word_mode | |
717 | /* Before trying mode different from the one in that # of iterations is | |
718 | computed, we must be sure that the number of iterations fits into | |
719 | the new mode. */ | |
5511bc5a | 720 | && (word_mode_size >= GET_MODE_PRECISION (mode) |
807e902e | 721 | || wi::leu_p (iterations_max, word_mode_max))) |
689ba89d | 722 | { |
5511bc5a | 723 | if (word_mode_size > GET_MODE_PRECISION (mode)) |
1d0216c8 | 724 | count = simplify_gen_unary (ZERO_EXTEND, word_mode, count, mode); |
a82bbcbb | 725 | else |
1d0216c8 | 726 | count = lowpart_subreg (word_mode, count, mode); |
689ba89d | 727 | PUT_MODE (doloop_reg, word_mode); |
1d0216c8 | 728 | doloop_seq = gen_doloop_end (doloop_reg, start_label); |
689ba89d ZD |
729 | } |
730 | if (! doloop_seq) | |
731 | { | |
732 | if (dump_file) | |
733 | fprintf (dump_file, | |
734 | "Doloop: Target unwilling to use doloop pattern!\n"); | |
735 | return false; | |
736 | } | |
737 | ||
738 | /* If multiple instructions were created, the last must be the | |
739 | jump instruction. Also, a raw define_insn may yield a plain | |
740 | pattern. */ | |
741 | doloop_pat = doloop_seq; | |
742 | if (INSN_P (doloop_pat)) | |
743 | { | |
b32d5189 DM |
744 | rtx_insn *doloop_insn = as_a <rtx_insn *> (doloop_pat); |
745 | while (NEXT_INSN (doloop_insn) != NULL_RTX) | |
746 | doloop_insn = NEXT_INSN (doloop_insn); | |
747 | if (!JUMP_P (doloop_insn)) | |
748 | doloop_insn = NULL; | |
749 | doloop_pat = doloop_insn; | |
689ba89d ZD |
750 | } |
751 | ||
752 | if (! doloop_pat | |
753 | || ! (condition = doloop_condition_get (doloop_pat))) | |
754 | { | |
755 | if (dump_file) | |
756 | fprintf (dump_file, "Doloop: Unrecognizable doloop pattern!\n"); | |
757 | return false; | |
758 | } | |
759 | ||
5f2e30ef | 760 | doloop_modify (loop, desc, doloop_seq, condition, count); |
689ba89d ZD |
761 | return true; |
762 | } | |
763 | ||
d73be268 | 764 | /* This is the main entry point. Process all loops using doloop_optimize. */ |
689ba89d ZD |
765 | |
766 | void | |
d73be268 | 767 | doloop_optimize_loops (void) |
689ba89d | 768 | { |
689ba89d ZD |
769 | struct loop *loop; |
770 | ||
fdbbed34 | 771 | FOR_EACH_LOOP (loop, 0) |
689ba89d | 772 | { |
689ba89d ZD |
773 | doloop_optimize (loop); |
774 | } | |
775 | ||
776 | iv_analysis_done (); | |
777 | ||
778 | #ifdef ENABLE_CHECKING | |
d73be268 | 779 | verify_loop_structure (); |
689ba89d ZD |
780 | #endif |
781 | } | |
782 | #endif /* HAVE_doloop_end */ | |
783 |