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2d49f824 | 1 | /* Perform doloop optimizations |
71e45bc2 | 2 | Copyright (C) 2004, 2005, 2006, 2007, 2008, 2010, 2011, 2012 |
c368b03d | 3 | Free Software Foundation, Inc. |
2d49f824 | 4 | Based on code by Michael P. Hayes (m.hayes@elec.canterbury.ac.nz) |
5 | ||
6 | This file is part of GCC. | |
7 | ||
8 | GCC is free software; you can redistribute it and/or modify it under | |
9 | the terms of the GNU General Public License as published by the Free | |
8c4c00c1 | 10 | Software Foundation; either version 3, or (at your option) any later |
2d49f824 | 11 | version. |
12 | ||
13 | GCC is distributed in the hope that it will be useful, but WITHOUT ANY | |
14 | WARRANTY; without even the implied warranty of MERCHANTABILITY or | |
15 | FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License | |
16 | for more details. | |
17 | ||
18 | You should have received a copy of the GNU General Public License | |
8c4c00c1 | 19 | along with GCC; see the file COPYING3. If not see |
20 | <http://www.gnu.org/licenses/>. */ | |
2d49f824 | 21 | |
22 | #include "config.h" | |
23 | #include "system.h" | |
24 | #include "coretypes.h" | |
25 | #include "tm.h" | |
26 | #include "rtl.h" | |
27 | #include "flags.h" | |
28 | #include "expr.h" | |
29 | #include "hard-reg-set.h" | |
30 | #include "basic-block.h" | |
0b205f4c | 31 | #include "diagnostic-core.h" |
2d49f824 | 32 | #include "tm_p.h" |
33 | #include "cfgloop.h" | |
2d49f824 | 34 | #include "params.h" |
7dfa5ce3 | 35 | #include "target.h" |
b9ed1410 | 36 | #include "dumpfile.h" |
2d49f824 | 37 | |
38 | /* This module is used to modify loops with a determinable number of | |
39 | iterations to use special low-overhead looping instructions. | |
40 | ||
41 | It first validates whether the loop is well behaved and has a | |
42 | determinable number of iterations (either at compile or run-time). | |
43 | It then modifies the loop to use a low-overhead looping pattern as | |
44 | follows: | |
45 | ||
46 | 1. A pseudo register is allocated as the loop iteration counter. | |
47 | ||
48 | 2. The number of loop iterations is calculated and is stored | |
49 | in the loop counter. | |
50 | ||
51 | 3. At the end of the loop, the jump insn is replaced by the | |
52 | doloop_end pattern. The compare must remain because it might be | |
53 | used elsewhere. If the loop-variable or condition register are | |
54 | used elsewhere, they will be eliminated by flow. | |
55 | ||
56 | 4. An optional doloop_begin pattern is inserted at the top of the | |
57 | loop. | |
58 | ||
59 | TODO The optimization should only performed when either the biv used for exit | |
60 | condition is unused at all except for the exit test, or if we do not have to | |
61 | change its value, since otherwise we have to add a new induction variable, | |
62 | which usually will not pay up (unless the cost of the doloop pattern is | |
63 | somehow extremely lower than the cost of compare & jump, or unless the bct | |
64 | register cannot be used for anything else but doloop -- ??? detect these | |
65 | cases). */ | |
66 | ||
67 | #ifdef HAVE_doloop_end | |
68 | ||
69 | /* Return the loop termination condition for PATTERN or zero | |
70 | if it is not a decrement and branch jump insn. */ | |
71 | ||
fc2abfd3 | 72 | rtx |
7bfc9b7c | 73 | doloop_condition_get (rtx doloop_pat) |
2d49f824 | 74 | { |
75 | rtx cmp; | |
76 | rtx inc; | |
77 | rtx reg; | |
fc2abfd3 | 78 | rtx inc_src; |
2d49f824 | 79 | rtx condition; |
7bfc9b7c | 80 | rtx pattern; |
90c2bcf0 | 81 | rtx cc_reg = NULL_RTX; |
82 | rtx reg_orig = NULL_RTX; | |
2d49f824 | 83 | |
7bfc9b7c | 84 | /* The canonical doloop pattern we expect has one of the following |
85 | forms: | |
2d49f824 | 86 | |
7bfc9b7c | 87 | 1) (parallel [(set (pc) (if_then_else (condition) |
88 | (label_ref (label)) | |
89 | (pc))) | |
90 | (set (reg) (plus (reg) (const_int -1))) | |
91 | (additional clobbers and uses)]) | |
2d49f824 | 92 | |
7bfc9b7c | 93 | The branch must be the first entry of the parallel (also required |
94 | by jump.c), and the second entry of the parallel must be a set of | |
95 | the loop counter register. Some targets (IA-64) wrap the set of | |
96 | the loop counter in an if_then_else too. | |
fc2abfd3 | 97 | |
7bfc9b7c | 98 | 2) (set (reg) (plus (reg) (const_int -1)) |
99 | (set (pc) (if_then_else (reg != 0) | |
100 | (label_ref (label)) | |
90c2bcf0 | 101 | (pc))). |
102 | ||
103 | Some targets (ARM) do the comparison before the branch, as in the | |
104 | following form: | |
105 | ||
106 | 3) (parallel [(set (cc) (compare ((plus (reg) (const_int -1), 0))) | |
107 | (set (reg) (plus (reg) (const_int -1)))]) | |
108 | (set (pc) (if_then_else (cc == NE) | |
109 | (label_ref (label)) | |
110 | (pc))) */ | |
7bfc9b7c | 111 | |
112 | pattern = PATTERN (doloop_pat); | |
2d49f824 | 113 | |
114 | if (GET_CODE (pattern) != PARALLEL) | |
7bfc9b7c | 115 | { |
116 | rtx cond; | |
9c868118 | 117 | rtx prev_insn = prev_nondebug_insn (doloop_pat); |
90c2bcf0 | 118 | rtx cmp_arg1, cmp_arg2; |
119 | rtx cmp_orig; | |
7bfc9b7c | 120 | |
90c2bcf0 | 121 | /* In case the pattern is not PARALLEL we expect two forms |
122 | of doloop which are cases 2) and 3) above: in case 2) the | |
123 | decrement immediately precedes the branch, while in case 3) | |
124 | the compare and decrement instructions immediately precede | |
125 | the branch. */ | |
2d49f824 | 126 | |
9c868118 | 127 | if (prev_insn == NULL_RTX || !INSN_P (prev_insn)) |
7bfc9b7c | 128 | return 0; |
129 | ||
130 | cmp = pattern; | |
90c2bcf0 | 131 | if (GET_CODE (PATTERN (prev_insn)) == PARALLEL) |
132 | { | |
133 | /* The third case: the compare and decrement instructions | |
134 | immediately precede the branch. */ | |
135 | cmp_orig = XVECEXP (PATTERN (prev_insn), 0, 0); | |
136 | if (GET_CODE (cmp_orig) != SET) | |
137 | return 0; | |
138 | if (GET_CODE (SET_SRC (cmp_orig)) != COMPARE) | |
139 | return 0; | |
140 | cmp_arg1 = XEXP (SET_SRC (cmp_orig), 0); | |
141 | cmp_arg2 = XEXP (SET_SRC (cmp_orig), 1); | |
142 | if (cmp_arg2 != const0_rtx | |
143 | || GET_CODE (cmp_arg1) != PLUS) | |
144 | return 0; | |
145 | reg_orig = XEXP (cmp_arg1, 0); | |
146 | if (XEXP (cmp_arg1, 1) != GEN_INT (-1) | |
147 | || !REG_P (reg_orig)) | |
148 | return 0; | |
149 | cc_reg = SET_DEST (cmp_orig); | |
150 | ||
151 | inc = XVECEXP (PATTERN (prev_insn), 0, 1); | |
152 | } | |
153 | else | |
29dc3c19 | 154 | inc = PATTERN (prev_insn); |
7bfc9b7c | 155 | /* We expect the condition to be of the form (reg != 0) */ |
156 | cond = XEXP (SET_SRC (cmp), 0); | |
157 | if (GET_CODE (cond) != NE || XEXP (cond, 1) != const0_rtx) | |
158 | return 0; | |
7bfc9b7c | 159 | } |
160 | else | |
161 | { | |
162 | cmp = XVECEXP (pattern, 0, 0); | |
163 | inc = XVECEXP (pattern, 0, 1); | |
164 | } | |
2d49f824 | 165 | |
166 | /* Check for (set (reg) (something)). */ | |
fc2abfd3 | 167 | if (GET_CODE (inc) != SET) |
2d49f824 | 168 | return 0; |
2d49f824 | 169 | reg = SET_DEST (inc); |
fc2abfd3 | 170 | if (! REG_P (reg)) |
171 | return 0; | |
172 | ||
173 | /* Check if something = (plus (reg) (const_int -1)). | |
174 | On IA-64, this decrement is wrapped in an if_then_else. */ | |
175 | inc_src = SET_SRC (inc); | |
176 | if (GET_CODE (inc_src) == IF_THEN_ELSE) | |
177 | inc_src = XEXP (inc_src, 1); | |
178 | if (GET_CODE (inc_src) != PLUS | |
179 | || XEXP (inc_src, 0) != reg | |
180 | || XEXP (inc_src, 1) != constm1_rtx) | |
181 | return 0; | |
2d49f824 | 182 | |
183 | /* Check for (set (pc) (if_then_else (condition) | |
184 | (label_ref (label)) | |
185 | (pc))). */ | |
186 | if (GET_CODE (cmp) != SET | |
187 | || SET_DEST (cmp) != pc_rtx | |
188 | || GET_CODE (SET_SRC (cmp)) != IF_THEN_ELSE | |
189 | || GET_CODE (XEXP (SET_SRC (cmp), 1)) != LABEL_REF | |
190 | || XEXP (SET_SRC (cmp), 2) != pc_rtx) | |
191 | return 0; | |
192 | ||
193 | /* Extract loop termination condition. */ | |
194 | condition = XEXP (SET_SRC (cmp), 0); | |
195 | ||
fc2abfd3 | 196 | /* We expect a GE or NE comparison with 0 or 1. */ |
197 | if ((GET_CODE (condition) != GE | |
198 | && GET_CODE (condition) != NE) | |
199 | || (XEXP (condition, 1) != const0_rtx | |
200 | && XEXP (condition, 1) != const1_rtx)) | |
2d49f824 | 201 | return 0; |
202 | ||
fc2abfd3 | 203 | if ((XEXP (condition, 0) == reg) |
90c2bcf0 | 204 | /* For the third case: */ |
205 | || ((cc_reg != NULL_RTX) | |
206 | && (XEXP (condition, 0) == cc_reg) | |
207 | && (reg_orig == reg)) | |
fc2abfd3 | 208 | || (GET_CODE (XEXP (condition, 0)) == PLUS |
90c2bcf0 | 209 | && XEXP (XEXP (condition, 0), 0) == reg)) |
7bfc9b7c | 210 | { |
211 | if (GET_CODE (pattern) != PARALLEL) | |
90c2bcf0 | 212 | /* For the second form we expect: |
7bfc9b7c | 213 | |
214 | (set (reg) (plus (reg) (const_int -1)) | |
215 | (set (pc) (if_then_else (reg != 0) | |
216 | (label_ref (label)) | |
217 | (pc))). | |
218 | ||
219 | is equivalent to the following: | |
220 | ||
221 | (parallel [(set (pc) (if_then_else (reg != 1) | |
222 | (label_ref (label)) | |
223 | (pc))) | |
224 | (set (reg) (plus (reg) (const_int -1))) | |
225 | (additional clobbers and uses)]) | |
226 | ||
90c2bcf0 | 227 | For the third form we expect: |
228 | ||
229 | (parallel [(set (cc) (compare ((plus (reg) (const_int -1)), 0)) | |
230 | (set (reg) (plus (reg) (const_int -1)))]) | |
231 | (set (pc) (if_then_else (cc == NE) | |
232 | (label_ref (label)) | |
233 | (pc))) | |
234 | ||
235 | which is equivalent to the following: | |
236 | ||
237 | (parallel [(set (cc) (compare (reg, 1)) | |
238 | (set (reg) (plus (reg) (const_int -1))) | |
239 | (set (pc) (if_then_else (NE == cc) | |
240 | (label_ref (label)) | |
241 | (pc))))]) | |
242 | ||
243 | So we return the second form instead for the two cases. | |
244 | ||
7bfc9b7c | 245 | */ |
246 | condition = gen_rtx_fmt_ee (NE, VOIDmode, inc_src, const1_rtx); | |
247 | ||
2d49f824 | 248 | return condition; |
7bfc9b7c | 249 | } |
2d49f824 | 250 | |
251 | /* ??? If a machine uses a funny comparison, we could return a | |
7bd28bba | 252 | canonicalized form here. */ |
2d49f824 | 253 | |
254 | return 0; | |
255 | } | |
256 | ||
257 | /* Return nonzero if the loop specified by LOOP is suitable for | |
258 | the use of special low-overhead looping instructions. DESC | |
259 | describes the number of iterations of the loop. */ | |
260 | ||
261 | static bool | |
262 | doloop_valid_p (struct loop *loop, struct niter_desc *desc) | |
263 | { | |
264 | basic_block *body = get_loop_body (loop), bb; | |
265 | rtx insn; | |
266 | unsigned i; | |
7caa482e | 267 | bool result = true; |
2d49f824 | 268 | |
269 | /* Check for loops that may not terminate under special conditions. */ | |
270 | if (!desc->simple_p | |
271 | || desc->assumptions | |
272 | || desc->infinite) | |
273 | { | |
274 | /* There are some cases that would require a special attention. | |
275 | For example if the comparison is LEU and the comparison value | |
276 | is UINT_MAX then the loop will not terminate. Similarly, if the | |
277 | comparison code is GEU and the comparison value is 0, the | |
278 | loop will not terminate. | |
279 | ||
280 | If the absolute increment is not 1, the loop can be infinite | |
281 | even with LTU/GTU, e.g. for (i = 3; i > 0; i -= 2) | |
282 | ||
283 | ??? We could compute these conditions at run-time and have a | |
284 | additional jump around the loop to ensure an infinite loop. | |
285 | However, it is very unlikely that this is the intended | |
286 | behavior of the loop and checking for these rare boundary | |
287 | conditions would pessimize all other code. | |
288 | ||
289 | If the loop is executed only a few times an extra check to | |
290 | restart the loop could use up most of the benefits of using a | |
291 | count register loop. Note however, that normally, this | |
292 | restart branch would never execute, so it could be predicted | |
293 | well by the CPU. We should generate the pessimistic code by | |
294 | default, and have an option, e.g. -funsafe-loops that would | |
295 | enable count-register loops in this case. */ | |
296 | if (dump_file) | |
297 | fprintf (dump_file, "Doloop: Possible infinite iteration case.\n"); | |
7caa482e | 298 | result = false; |
299 | goto cleanup; | |
2d49f824 | 300 | } |
301 | ||
302 | for (i = 0; i < loop->num_nodes; i++) | |
303 | { | |
304 | bb = body[i]; | |
305 | ||
306 | for (insn = BB_HEAD (bb); | |
307 | insn != NEXT_INSN (BB_END (bb)); | |
308 | insn = NEXT_INSN (insn)) | |
309 | { | |
7dfa5ce3 | 310 | /* Different targets have different necessities for low-overhead |
311 | looping. Call the back end for each instruction within the loop | |
1606e68a | 312 | to let it decide whether the insn prohibits a low-overhead loop. |
313 | It will then return the cause for it to emit to the dump file. */ | |
314 | const char * invalid = targetm.invalid_within_doloop (insn); | |
315 | if (invalid) | |
316 | { | |
317 | if (dump_file) | |
318 | fprintf (dump_file, "Doloop: %s\n", invalid); | |
7caa482e | 319 | result = false; |
320 | goto cleanup; | |
1606e68a | 321 | } |
2d49f824 | 322 | } |
323 | } | |
7caa482e | 324 | result = true; |
325 | ||
326 | cleanup: | |
2d49f824 | 327 | free (body); |
328 | ||
7caa482e | 329 | return result; |
2d49f824 | 330 | } |
331 | ||
a4c7895e | 332 | /* Adds test of COND jumping to DEST on edge *E and set *E to the new fallthru |
333 | edge. If the condition is always false, do not do anything. If it is always | |
334 | true, redirect E to DEST and return false. In all other cases, true is | |
335 | returned. */ | |
2d49f824 | 336 | |
a4c7895e | 337 | static bool |
338 | add_test (rtx cond, edge *e, basic_block dest) | |
2d49f824 | 339 | { |
340 | rtx seq, jump, label; | |
341 | enum machine_mode mode; | |
342 | rtx op0 = XEXP (cond, 0), op1 = XEXP (cond, 1); | |
343 | enum rtx_code code = GET_CODE (cond); | |
a4c7895e | 344 | basic_block bb; |
2d49f824 | 345 | |
346 | mode = GET_MODE (XEXP (cond, 0)); | |
347 | if (mode == VOIDmode) | |
348 | mode = GET_MODE (XEXP (cond, 1)); | |
349 | ||
350 | start_sequence (); | |
351 | op0 = force_operand (op0, NULL_RTX); | |
352 | op1 = force_operand (op1, NULL_RTX); | |
353 | label = block_label (dest); | |
c368b03d | 354 | do_compare_rtx_and_jump (op0, op1, code, 0, mode, NULL_RTX, |
355 | NULL_RTX, label, -1); | |
2d49f824 | 356 | |
357 | jump = get_last_insn (); | |
d6a1bbdb | 358 | if (!jump || !JUMP_P (jump)) |
3c4d0a06 | 359 | { |
a4c7895e | 360 | /* The condition is always false and the jump was optimized out. */ |
361 | end_sequence (); | |
362 | return true; | |
3c4d0a06 | 363 | } |
2d49f824 | 364 | |
365 | seq = get_insns (); | |
366 | end_sequence (); | |
d6a1bbdb | 367 | |
368 | /* There always is at least the jump insn in the sequence. */ | |
369 | gcc_assert (seq != NULL_RTX); | |
370 | ||
88e6f696 | 371 | bb = split_edge_and_insert (*e, seq); |
a4c7895e | 372 | *e = single_succ_edge (bb); |
373 | ||
374 | if (any_uncondjump_p (jump)) | |
375 | { | |
376 | /* The condition is always true. */ | |
377 | delete_insn (jump); | |
378 | redirect_edge_and_branch_force (*e, dest); | |
379 | return false; | |
380 | } | |
48e1416a | 381 | |
a4c7895e | 382 | JUMP_LABEL (jump) = label; |
383 | ||
384 | /* The jump is supposed to handle an unlikely special case. */ | |
a1ddb869 | 385 | add_reg_note (jump, REG_BR_PROB, const0_rtx); |
386 | ||
a4c7895e | 387 | LABEL_NUSES (label)++; |
388 | ||
389 | make_edge (bb, dest, (*e)->flags & ~EDGE_FALLTHRU); | |
390 | return true; | |
2d49f824 | 391 | } |
392 | ||
393 | /* Modify the loop to use the low-overhead looping insn where LOOP | |
394 | describes the loop, DESC describes the number of iterations of the | |
395 | loop, and DOLOOP_INSN is the low-overhead looping insn to emit at the | |
396 | end of the loop. CONDITION is the condition separated from the | |
941f640b | 397 | DOLOOP_SEQ. COUNT is the number of iterations of the LOOP. */ |
2d49f824 | 398 | |
399 | static void | |
400 | doloop_modify (struct loop *loop, struct niter_desc *desc, | |
941f640b | 401 | rtx doloop_seq, rtx condition, rtx count) |
2d49f824 | 402 | { |
403 | rtx counter_reg; | |
cde5a3a0 | 404 | rtx tmp, noloop = NULL_RTX; |
2d49f824 | 405 | rtx sequence; |
406 | rtx jump_insn; | |
407 | rtx jump_label; | |
a4c7895e | 408 | int nonneg = 0; |
2d49f824 | 409 | bool increment_count; |
410 | basic_block loop_end = desc->out_edge->src; | |
cde5a3a0 | 411 | enum machine_mode mode; |
fa7f4c0c | 412 | rtx true_prob_val; |
a9ef9877 | 413 | double_int iterations; |
2d49f824 | 414 | |
415 | jump_insn = BB_END (loop_end); | |
416 | ||
417 | if (dump_file) | |
418 | { | |
419 | fprintf (dump_file, "Doloop: Inserting doloop pattern ("); | |
420 | if (desc->const_iter) | |
421 | fprintf (dump_file, HOST_WIDEST_INT_PRINT_DEC, desc->niter); | |
422 | else | |
423 | fputs ("runtime", dump_file); | |
424 | fputs (" iterations).\n", dump_file); | |
425 | } | |
426 | ||
f0b5f617 | 427 | /* Get the probability of the original branch. If it exists we would |
fa7f4c0c | 428 | need to update REG_BR_PROB of the new jump_insn. */ |
429 | true_prob_val = find_reg_note (jump_insn, REG_BR_PROB, NULL_RTX); | |
430 | ||
2d49f824 | 431 | /* Discard original jump to continue loop. The original compare |
432 | result may still be live, so it cannot be discarded explicitly. */ | |
433 | delete_insn (jump_insn); | |
434 | ||
435 | counter_reg = XEXP (condition, 0); | |
436 | if (GET_CODE (counter_reg) == PLUS) | |
437 | counter_reg = XEXP (counter_reg, 0); | |
cde5a3a0 | 438 | mode = GET_MODE (counter_reg); |
2d49f824 | 439 | |
2d49f824 | 440 | increment_count = false; |
441 | switch (GET_CODE (condition)) | |
442 | { | |
443 | case NE: | |
444 | /* Currently only NE tests against zero and one are supported. */ | |
972e95af | 445 | noloop = XEXP (condition, 1); |
446 | if (noloop != const0_rtx) | |
2d49f824 | 447 | { |
972e95af | 448 | gcc_assert (noloop == const1_rtx); |
2d49f824 | 449 | increment_count = true; |
2d49f824 | 450 | } |
2d49f824 | 451 | break; |
452 | ||
453 | case GE: | |
454 | /* Currently only GE tests against zero are supported. */ | |
972e95af | 455 | gcc_assert (XEXP (condition, 1) == const0_rtx); |
2d49f824 | 456 | |
457 | noloop = constm1_rtx; | |
458 | ||
459 | /* The iteration count does not need incrementing for a GE test. */ | |
460 | increment_count = false; | |
461 | ||
462 | /* Determine if the iteration counter will be non-negative. | |
463 | Note that the maximum value loaded is iterations_max - 1. */ | |
a9ef9877 | 464 | if (max_loop_iterations (loop, &iterations) |
465 | && (iterations.ule (double_int_one.llshift | |
466 | (GET_MODE_PRECISION (mode) - 1, | |
467 | GET_MODE_PRECISION (mode))))) | |
2d49f824 | 468 | nonneg = 1; |
469 | break; | |
470 | ||
b690c0a3 | 471 | /* Abort if an invalid doloop pattern has been generated. */ |
2045cdd4 | 472 | default: |
972e95af | 473 | gcc_unreachable (); |
2d49f824 | 474 | } |
475 | ||
476 | if (increment_count) | |
941f640b | 477 | count = simplify_gen_binary (PLUS, mode, count, const1_rtx); |
560a2fa6 | 478 | |
2d49f824 | 479 | /* Insert initialization of the count register into the loop header. */ |
480 | start_sequence (); | |
481 | tmp = force_operand (count, counter_reg); | |
482 | convert_move (counter_reg, tmp, 1); | |
483 | sequence = get_insns (); | |
484 | end_sequence (); | |
485 | emit_insn_after (sequence, BB_END (loop_preheader_edge (loop)->src)); | |
486 | ||
487 | if (desc->noloop_assumptions) | |
488 | { | |
c30738d0 | 489 | rtx ass = copy_rtx (desc->noloop_assumptions); |
2d49f824 | 490 | basic_block preheader = loop_preheader_edge (loop)->src; |
491 | basic_block set_zero | |
88e6f696 | 492 | = split_edge (loop_preheader_edge (loop)); |
2d49f824 | 493 | basic_block new_preheader |
88e6f696 | 494 | = split_edge (loop_preheader_edge (loop)); |
2d49f824 | 495 | edge te; |
2d49f824 | 496 | |
497 | /* Expand the condition testing the assumptions and if it does not pass, | |
498 | reset the count register to 0. */ | |
a4c7895e | 499 | redirect_edge_and_branch_force (single_succ_edge (preheader), new_preheader); |
2d49f824 | 500 | set_immediate_dominator (CDI_DOMINATORS, new_preheader, preheader); |
501 | ||
502 | set_zero->count = 0; | |
503 | set_zero->frequency = 0; | |
504 | ||
a4c7895e | 505 | te = single_succ_edge (preheader); |
506 | for (; ass; ass = XEXP (ass, 1)) | |
507 | if (!add_test (XEXP (ass, 0), &te, set_zero)) | |
508 | break; | |
509 | ||
510 | if (ass) | |
2d49f824 | 511 | { |
a4c7895e | 512 | /* We reached a condition that is always true. This is very hard to |
513 | reproduce (such a loop does not roll, and thus it would most | |
514 | likely get optimized out by some of the preceding optimizations). | |
515 | In fact, I do not have any testcase for it. However, it would | |
516 | also be very hard to show that it is impossible, so we must | |
517 | handle this case. */ | |
518 | set_zero->count = preheader->count; | |
519 | set_zero->frequency = preheader->frequency; | |
2d49f824 | 520 | } |
48e1416a | 521 | |
a4c7895e | 522 | if (EDGE_COUNT (set_zero->preds) == 0) |
523 | { | |
524 | /* All the conditions were simplified to false, remove the | |
525 | unreachable set_zero block. */ | |
a4c7895e | 526 | delete_basic_block (set_zero); |
527 | } | |
528 | else | |
529 | { | |
530 | /* Reset the counter to zero in the set_zero block. */ | |
531 | start_sequence (); | |
532 | convert_move (counter_reg, noloop, 0); | |
533 | sequence = get_insns (); | |
534 | end_sequence (); | |
535 | emit_insn_after (sequence, BB_END (set_zero)); | |
48e1416a | 536 | |
a4c7895e | 537 | set_immediate_dominator (CDI_DOMINATORS, set_zero, |
3f9439d7 | 538 | recompute_dominator (CDI_DOMINATORS, |
539 | set_zero)); | |
a4c7895e | 540 | } |
541 | ||
542 | set_immediate_dominator (CDI_DOMINATORS, new_preheader, | |
3f9439d7 | 543 | recompute_dominator (CDI_DOMINATORS, |
544 | new_preheader)); | |
2d49f824 | 545 | } |
546 | ||
547 | /* Some targets (eg, C4x) need to initialize special looping | |
548 | registers. */ | |
549 | #ifdef HAVE_doloop_begin | |
550 | { | |
551 | rtx init; | |
552 | unsigned level = get_loop_level (loop) + 1; | |
a9ef9877 | 553 | double_int iter; |
554 | rtx iter_rtx; | |
555 | ||
556 | if (!max_loop_iterations (loop, &iter) | |
557 | || !iter.fits_shwi ()) | |
558 | iter_rtx = const0_rtx; | |
559 | else | |
560 | iter_rtx = GEN_INT (iter.to_shwi()); | |
2d49f824 | 561 | init = gen_doloop_begin (counter_reg, |
562 | desc->const_iter ? desc->niter_expr : const0_rtx, | |
a9ef9877 | 563 | iter_rtx, |
bbdfcf34 | 564 | GEN_INT (level), |
565 | doloop_seq); | |
2d49f824 | 566 | if (init) |
567 | { | |
568 | start_sequence (); | |
569 | emit_insn (init); | |
570 | sequence = get_insns (); | |
571 | end_sequence (); | |
572 | emit_insn_after (sequence, BB_END (loop_preheader_edge (loop)->src)); | |
573 | } | |
574 | } | |
575 | #endif | |
576 | ||
577 | /* Insert the new low-overhead looping insn. */ | |
578 | emit_jump_insn_after (doloop_seq, BB_END (loop_end)); | |
579 | jump_insn = BB_END (loop_end); | |
580 | jump_label = block_label (desc->in_edge->dest); | |
581 | JUMP_LABEL (jump_insn) = jump_label; | |
582 | LABEL_NUSES (jump_label)++; | |
583 | ||
584 | /* Ensure the right fallthru edge is marked, for case we have reversed | |
585 | the condition. */ | |
586 | desc->in_edge->flags &= ~EDGE_FALLTHRU; | |
587 | desc->out_edge->flags |= EDGE_FALLTHRU; | |
588 | ||
589 | /* Add a REG_NONNEG note if the actual or estimated maximum number | |
590 | of iterations is non-negative. */ | |
591 | if (nonneg) | |
a1ddb869 | 592 | add_reg_note (jump_insn, REG_NONNEG, NULL_RTX); |
593 | ||
fa7f4c0c | 594 | /* Update the REG_BR_PROB note. */ |
595 | if (true_prob_val) | |
596 | { | |
597 | /* Seems safer to use the branch probability. */ | |
48e1416a | 598 | add_reg_note (jump_insn, REG_BR_PROB, |
a1ddb869 | 599 | GEN_INT (desc->in_edge->probability)); |
fa7f4c0c | 600 | } |
2d49f824 | 601 | } |
602 | ||
603 | /* Process loop described by LOOP validating that the loop is suitable for | |
604 | conversion to use a low overhead looping instruction, replacing the jump | |
605 | insn where suitable. Returns true if the loop was successfully | |
606 | modified. */ | |
607 | ||
608 | static bool | |
609 | doloop_optimize (struct loop *loop) | |
610 | { | |
611 | enum machine_mode mode; | |
612 | rtx doloop_seq, doloop_pat, doloop_reg; | |
cde5a3a0 | 613 | rtx iterations, count; |
2d49f824 | 614 | rtx iterations_max; |
615 | rtx start_label; | |
616 | rtx condition; | |
9cab63d0 | 617 | unsigned level, est_niter; |
618 | int max_cost; | |
2d49f824 | 619 | struct niter_desc *desc; |
cde5a3a0 | 620 | unsigned word_mode_size; |
621 | unsigned HOST_WIDE_INT word_mode_max; | |
a9ef9877 | 622 | double_int iter; |
bbdfcf34 | 623 | int entered_at_top; |
2d49f824 | 624 | |
625 | if (dump_file) | |
626 | fprintf (dump_file, "Doloop: Processing loop %d.\n", loop->num); | |
627 | ||
628 | iv_analysis_loop_init (loop); | |
629 | ||
630 | /* Find the simple exit of a LOOP. */ | |
631 | desc = get_simple_loop_desc (loop); | |
632 | ||
633 | /* Check that loop is a candidate for a low-overhead looping insn. */ | |
634 | if (!doloop_valid_p (loop, desc)) | |
635 | { | |
636 | if (dump_file) | |
637 | fprintf (dump_file, | |
638 | "Doloop: The loop is not suitable.\n"); | |
639 | return false; | |
640 | } | |
641 | mode = desc->mode; | |
642 | ||
643 | est_niter = 3; | |
644 | if (desc->const_iter) | |
645 | est_niter = desc->niter; | |
646 | /* If the estimate on number of iterations is reliable (comes from profile | |
647 | feedback), use it. Do not use it normally, since the expected number | |
648 | of iterations of an unrolled loop is 2. */ | |
649 | if (loop->header->count) | |
650 | est_niter = expected_loop_iterations (loop); | |
651 | ||
652 | if (est_niter < 3) | |
653 | { | |
654 | if (dump_file) | |
655 | fprintf (dump_file, | |
656 | "Doloop: Too few iterations (%u) to be profitable.\n", | |
657 | est_niter); | |
658 | return false; | |
659 | } | |
660 | ||
883bb2bb | 661 | max_cost |
662 | = COSTS_N_INSNS (PARAM_VALUE (PARAM_MAX_ITERATIONS_COMPUTATION_COST)); | |
7013e87c | 663 | if (set_src_cost (desc->niter_expr, optimize_loop_for_speed_p (loop)) |
f529eb25 | 664 | > max_cost) |
883bb2bb | 665 | { |
666 | if (dump_file) | |
667 | fprintf (dump_file, | |
2ce55c0b | 668 | "Doloop: number of iterations too costly to compute.\n"); |
883bb2bb | 669 | return false; |
670 | } | |
671 | ||
cde5a3a0 | 672 | count = copy_rtx (desc->niter_expr); |
2d49f824 | 673 | iterations = desc->const_iter ? desc->niter_expr : const0_rtx; |
a9ef9877 | 674 | if (!max_loop_iterations (loop, &iter) |
675 | || !iter.fits_shwi ()) | |
676 | iterations_max = const0_rtx; | |
677 | else | |
678 | iterations_max = GEN_INT (iter.to_shwi()); | |
2d49f824 | 679 | level = get_loop_level (loop) + 1; |
680 | ||
681 | /* Generate looping insn. If the pattern FAILs then give up trying | |
682 | to modify the loop since there is some aspect the back-end does | |
683 | not like. */ | |
684 | start_label = block_label (desc->in_edge->dest); | |
685 | doloop_reg = gen_reg_rtx (mode); | |
bbdfcf34 | 686 | entered_at_top = (loop->latch == desc->in_edge->dest |
f35d28da | 687 | && contains_no_active_insn_p (loop->latch)); |
2d49f824 | 688 | doloop_seq = gen_doloop_end (doloop_reg, iterations, iterations_max, |
bbdfcf34 | 689 | GEN_INT (level), start_label, |
690 | GEN_INT (entered_at_top)); | |
cde5a3a0 | 691 | |
ded805e6 | 692 | word_mode_size = GET_MODE_PRECISION (word_mode); |
cde5a3a0 | 693 | word_mode_max |
694 | = ((unsigned HOST_WIDE_INT) 1 << (word_mode_size - 1) << 1) - 1; | |
695 | if (! doloop_seq | |
696 | && mode != word_mode | |
697 | /* Before trying mode different from the one in that # of iterations is | |
698 | computed, we must be sure that the number of iterations fits into | |
699 | the new mode. */ | |
ded805e6 | 700 | && (word_mode_size >= GET_MODE_PRECISION (mode) |
a9ef9877 | 701 | || iter.ule (double_int::from_shwi (word_mode_max)))) |
2d49f824 | 702 | { |
ded805e6 | 703 | if (word_mode_size > GET_MODE_PRECISION (mode)) |
cde5a3a0 | 704 | { |
941f640b | 705 | count = simplify_gen_unary (ZERO_EXTEND, word_mode, |
706 | count, mode); | |
cde5a3a0 | 707 | iterations = simplify_gen_unary (ZERO_EXTEND, word_mode, |
708 | iterations, mode); | |
709 | iterations_max = simplify_gen_unary (ZERO_EXTEND, word_mode, | |
710 | iterations_max, mode); | |
711 | } | |
712 | else | |
713 | { | |
714 | count = lowpart_subreg (word_mode, count, mode); | |
715 | iterations = lowpart_subreg (word_mode, iterations, mode); | |
716 | iterations_max = lowpart_subreg (word_mode, iterations_max, mode); | |
717 | } | |
2d49f824 | 718 | PUT_MODE (doloop_reg, word_mode); |
719 | doloop_seq = gen_doloop_end (doloop_reg, iterations, iterations_max, | |
bbdfcf34 | 720 | GEN_INT (level), start_label, |
721 | GEN_INT (entered_at_top)); | |
2d49f824 | 722 | } |
723 | if (! doloop_seq) | |
724 | { | |
725 | if (dump_file) | |
726 | fprintf (dump_file, | |
727 | "Doloop: Target unwilling to use doloop pattern!\n"); | |
728 | return false; | |
729 | } | |
730 | ||
731 | /* If multiple instructions were created, the last must be the | |
732 | jump instruction. Also, a raw define_insn may yield a plain | |
733 | pattern. */ | |
734 | doloop_pat = doloop_seq; | |
735 | if (INSN_P (doloop_pat)) | |
736 | { | |
737 | while (NEXT_INSN (doloop_pat) != NULL_RTX) | |
738 | doloop_pat = NEXT_INSN (doloop_pat); | |
7bfc9b7c | 739 | if (!JUMP_P (doloop_pat)) |
2d49f824 | 740 | doloop_pat = NULL_RTX; |
741 | } | |
742 | ||
743 | if (! doloop_pat | |
744 | || ! (condition = doloop_condition_get (doloop_pat))) | |
745 | { | |
746 | if (dump_file) | |
747 | fprintf (dump_file, "Doloop: Unrecognizable doloop pattern!\n"); | |
748 | return false; | |
749 | } | |
750 | ||
941f640b | 751 | doloop_modify (loop, desc, doloop_seq, condition, count); |
2d49f824 | 752 | return true; |
753 | } | |
754 | ||
7194de72 | 755 | /* This is the main entry point. Process all loops using doloop_optimize. */ |
2d49f824 | 756 | |
757 | void | |
7194de72 | 758 | doloop_optimize_loops (void) |
2d49f824 | 759 | { |
17519ba0 | 760 | loop_iterator li; |
2d49f824 | 761 | struct loop *loop; |
762 | ||
17519ba0 | 763 | FOR_EACH_LOOP (li, loop, 0) |
2d49f824 | 764 | { |
2d49f824 | 765 | doloop_optimize (loop); |
766 | } | |
767 | ||
768 | iv_analysis_done (); | |
769 | ||
770 | #ifdef ENABLE_CHECKING | |
7194de72 | 771 | verify_loop_structure (); |
2d49f824 | 772 | #endif |
773 | } | |
774 | #endif /* HAVE_doloop_end */ | |
775 |