Mercurial > hg > CbC > CbC_gcc
annotate gcc/tree-tailcall.c @ 58:3aaf117db171
error at dwarf2out.c
author | ryoma <e075725@ie.u-ryukyu.ac.jp> |
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date | Mon, 15 Feb 2010 14:58:24 +0900 |
parents | 77e2b8dfacca |
children | b7f97abdc517 |
rev | line source |
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0 | 1 /* Tail call optimization on trees. |
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2 Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009 |
0 | 3 Free Software Foundation, Inc. |
4 | |
5 This file is part of GCC. | |
6 | |
7 GCC is free software; you can redistribute it and/or modify | |
8 it under the terms of the GNU General Public License as published by | |
9 the Free Software Foundation; either version 3, or (at your option) | |
10 any later version. | |
11 | |
12 GCC is distributed in the hope that it will be useful, | |
13 but WITHOUT ANY WARRANTY; without even the implied warranty of | |
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
15 GNU General Public License for more details. | |
16 | |
17 You should have received a copy of the GNU General Public License | |
18 along with GCC; see the file COPYING3. If not see | |
19 <http://www.gnu.org/licenses/>. */ | |
20 | |
21 #include "config.h" | |
22 #include "system.h" | |
23 #include "coretypes.h" | |
24 #include "tm.h" | |
25 #include "tree.h" | |
26 #include "rtl.h" | |
27 #include "tm_p.h" | |
28 #include "hard-reg-set.h" | |
29 #include "basic-block.h" | |
30 #include "function.h" | |
31 #include "tree-flow.h" | |
32 #include "tree-dump.h" | |
33 #include "diagnostic.h" | |
34 #include "except.h" | |
35 #include "tree-pass.h" | |
36 #include "flags.h" | |
37 #include "langhooks.h" | |
38 #include "dbgcnt.h" | |
39 | |
40 /* The file implements the tail recursion elimination. It is also used to | |
41 analyze the tail calls in general, passing the results to the rtl level | |
42 where they are used for sibcall optimization. | |
43 | |
44 In addition to the standard tail recursion elimination, we handle the most | |
45 trivial cases of making the call tail recursive by creating accumulators. | |
46 For example the following function | |
47 | |
48 int sum (int n) | |
49 { | |
50 if (n > 0) | |
51 return n + sum (n - 1); | |
52 else | |
53 return 0; | |
54 } | |
55 | |
56 is transformed into | |
57 | |
58 int sum (int n) | |
59 { | |
60 int acc = 0; | |
61 | |
62 while (n > 0) | |
63 acc += n--; | |
64 | |
65 return acc; | |
66 } | |
67 | |
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68 To do this, we maintain two accumulators (a_acc and m_acc) that indicate |
0 | 69 when we reach the return x statement, we should return a_acc + x * m_acc |
70 instead. They are initially initialized to 0 and 1, respectively, | |
71 so the semantics of the function is obviously preserved. If we are | |
72 guaranteed that the value of the accumulator never change, we | |
73 omit the accumulator. | |
74 | |
75 There are three cases how the function may exit. The first one is | |
76 handled in adjust_return_value, the other two in adjust_accumulator_values | |
77 (the second case is actually a special case of the third one and we | |
78 present it separately just for clarity): | |
79 | |
80 1) Just return x, where x is not in any of the remaining special shapes. | |
81 We rewrite this to a gimple equivalent of return m_acc * x + a_acc. | |
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82 |
0 | 83 2) return f (...), where f is the current function, is rewritten in a |
84 classical tail-recursion elimination way, into assignment of arguments | |
85 and jump to the start of the function. Values of the accumulators | |
86 are unchanged. | |
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87 |
0 | 88 3) return a + m * f(...), where a and m do not depend on call to f. |
89 To preserve the semantics described before we want this to be rewritten | |
90 in such a way that we finally return | |
91 | |
92 a_acc + (a + m * f(...)) * m_acc = (a_acc + a * m_acc) + (m * m_acc) * f(...). | |
93 | |
94 I.e. we increase a_acc by a * m_acc, multiply m_acc by m and | |
95 eliminate the tail call to f. Special cases when the value is just | |
96 added or just multiplied are obtained by setting a = 0 or m = 1. | |
97 | |
98 TODO -- it is possible to do similar tricks for other operations. */ | |
99 | |
100 /* A structure that describes the tailcall. */ | |
101 | |
102 struct tailcall | |
103 { | |
104 /* The iterator pointing to the call statement. */ | |
105 gimple_stmt_iterator call_gsi; | |
106 | |
107 /* True if it is a call to the current function. */ | |
108 bool tail_recursion; | |
109 | |
110 /* The return value of the caller is mult * f + add, where f is the return | |
111 value of the call. */ | |
112 tree mult, add; | |
113 | |
114 /* Next tailcall in the chain. */ | |
115 struct tailcall *next; | |
116 }; | |
117 | |
118 /* The variables holding the value of multiplicative and additive | |
119 accumulator. */ | |
120 static tree m_acc, a_acc; | |
121 | |
122 static bool suitable_for_tail_opt_p (void); | |
123 static bool optimize_tail_call (struct tailcall *, bool); | |
124 static void eliminate_tail_call (struct tailcall *); | |
125 static void find_tail_calls (basic_block, struct tailcall **); | |
126 | |
127 /* Returns false when the function is not suitable for tail call optimization | |
128 from some reason (e.g. if it takes variable number of arguments). */ | |
129 | |
130 static bool | |
131 suitable_for_tail_opt_p (void) | |
132 { | |
133 referenced_var_iterator rvi; | |
134 tree var; | |
135 | |
136 if (cfun->stdarg) | |
137 return false; | |
138 | |
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139 /* No local variable nor structure field should be call-used. */ |
0 | 140 FOR_EACH_REFERENCED_VAR (var, rvi) |
141 { | |
142 if (!is_global_var (var) | |
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143 && is_call_used (var)) |
0 | 144 return false; |
145 } | |
146 | |
147 return true; | |
148 } | |
149 /* Returns false when the function is not suitable for tail call optimization | |
150 from some reason (e.g. if it takes variable number of arguments). | |
151 This test must pass in addition to suitable_for_tail_opt_p in order to make | |
152 tail call discovery happen. */ | |
153 | |
154 static bool | |
155 suitable_for_tail_call_opt_p (void) | |
156 { | |
157 tree param; | |
158 | |
159 /* alloca (until we have stack slot life analysis) inhibits | |
160 sibling call optimizations, but not tail recursion. */ | |
161 if (cfun->calls_alloca) | |
162 return false; | |
163 | |
164 /* If we are using sjlj exceptions, we may need to add a call to | |
165 _Unwind_SjLj_Unregister at exit of the function. Which means | |
166 that we cannot do any sibcall transformations. */ | |
167 if (USING_SJLJ_EXCEPTIONS && current_function_has_exception_handlers ()) | |
168 return false; | |
169 | |
170 /* Any function that calls setjmp might have longjmp called from | |
171 any called function. ??? We really should represent this | |
172 properly in the CFG so that this needn't be special cased. */ | |
173 if (cfun->calls_setjmp) | |
174 return false; | |
175 | |
176 /* ??? It is OK if the argument of a function is taken in some cases, | |
177 but not in all cases. See PR15387 and PR19616. Revisit for 4.1. */ | |
178 for (param = DECL_ARGUMENTS (current_function_decl); | |
179 param; | |
180 param = TREE_CHAIN (param)) | |
181 if (TREE_ADDRESSABLE (param)) | |
182 return false; | |
183 | |
184 return true; | |
185 } | |
186 | |
187 /* Checks whether the expression EXPR in stmt AT is independent of the | |
188 statement pointed to by GSI (in a sense that we already know EXPR's value | |
189 at GSI). We use the fact that we are only called from the chain of | |
190 basic blocks that have only single successor. Returns the expression | |
191 containing the value of EXPR at GSI. */ | |
192 | |
193 static tree | |
194 independent_of_stmt_p (tree expr, gimple at, gimple_stmt_iterator gsi) | |
195 { | |
196 basic_block bb, call_bb, at_bb; | |
197 edge e; | |
198 edge_iterator ei; | |
199 | |
200 if (is_gimple_min_invariant (expr)) | |
201 return expr; | |
202 | |
203 if (TREE_CODE (expr) != SSA_NAME) | |
204 return NULL_TREE; | |
205 | |
206 /* Mark the blocks in the chain leading to the end. */ | |
207 at_bb = gimple_bb (at); | |
208 call_bb = gimple_bb (gsi_stmt (gsi)); | |
209 for (bb = call_bb; bb != at_bb; bb = single_succ (bb)) | |
210 bb->aux = &bb->aux; | |
211 bb->aux = &bb->aux; | |
212 | |
213 while (1) | |
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214 { |
0 | 215 at = SSA_NAME_DEF_STMT (expr); |
216 bb = gimple_bb (at); | |
217 | |
218 /* The default definition or defined before the chain. */ | |
219 if (!bb || !bb->aux) | |
220 break; | |
221 | |
222 if (bb == call_bb) | |
223 { | |
224 for (; !gsi_end_p (gsi); gsi_next (&gsi)) | |
225 if (gsi_stmt (gsi) == at) | |
226 break; | |
227 | |
228 if (!gsi_end_p (gsi)) | |
229 expr = NULL_TREE; | |
230 break; | |
231 } | |
232 | |
233 if (gimple_code (at) != GIMPLE_PHI) | |
234 { | |
235 expr = NULL_TREE; | |
236 break; | |
237 } | |
238 | |
239 FOR_EACH_EDGE (e, ei, bb->preds) | |
240 if (e->src->aux) | |
241 break; | |
242 gcc_assert (e); | |
243 | |
244 expr = PHI_ARG_DEF_FROM_EDGE (at, e); | |
245 if (TREE_CODE (expr) != SSA_NAME) | |
246 { | |
247 /* The value is a constant. */ | |
248 break; | |
249 } | |
250 } | |
251 | |
252 /* Unmark the blocks. */ | |
253 for (bb = call_bb; bb != at_bb; bb = single_succ (bb)) | |
254 bb->aux = NULL; | |
255 bb->aux = NULL; | |
256 | |
257 return expr; | |
258 } | |
259 | |
260 /* Simulates the effect of an assignment STMT on the return value of the tail | |
261 recursive CALL passed in ASS_VAR. M and A are the multiplicative and the | |
262 additive factor for the real return value. */ | |
263 | |
264 static bool | |
265 process_assignment (gimple stmt, gimple_stmt_iterator call, tree *m, | |
266 tree *a, tree *ass_var) | |
267 { | |
268 tree op0, op1, non_ass_var; | |
269 tree dest = gimple_assign_lhs (stmt); | |
270 enum tree_code code = gimple_assign_rhs_code (stmt); | |
271 enum gimple_rhs_class rhs_class = get_gimple_rhs_class (code); | |
272 tree src_var = gimple_assign_rhs1 (stmt); | |
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273 |
0 | 274 /* See if this is a simple copy operation of an SSA name to the function |
275 result. In that case we may have a simple tail call. Ignore type | |
276 conversions that can never produce extra code between the function | |
277 call and the function return. */ | |
278 if ((rhs_class == GIMPLE_SINGLE_RHS || gimple_assign_cast_p (stmt)) | |
279 && (TREE_CODE (src_var) == SSA_NAME)) | |
280 { | |
281 /* Reject a tailcall if the type conversion might need | |
282 additional code. */ | |
283 if (gimple_assign_cast_p (stmt) | |
284 && TYPE_MODE (TREE_TYPE (dest)) != TYPE_MODE (TREE_TYPE (src_var))) | |
285 return false; | |
286 | |
287 if (src_var != *ass_var) | |
288 return false; | |
289 | |
290 *ass_var = dest; | |
291 return true; | |
292 } | |
293 | |
294 if (rhs_class != GIMPLE_BINARY_RHS) | |
295 return false; | |
296 | |
297 /* Accumulator optimizations will reverse the order of operations. | |
298 We can only do that for floating-point types if we're assuming | |
299 that addition and multiplication are associative. */ | |
300 if (!flag_associative_math) | |
301 if (FLOAT_TYPE_P (TREE_TYPE (DECL_RESULT (current_function_decl)))) | |
302 return false; | |
303 | |
304 /* We only handle the code like | |
305 | |
306 x = call (); | |
307 y = m * x; | |
308 z = y + a; | |
309 return z; | |
310 | |
311 TODO -- Extend it for cases where the linear transformation of the output | |
312 is expressed in a more complicated way. */ | |
313 | |
314 op0 = gimple_assign_rhs1 (stmt); | |
315 op1 = gimple_assign_rhs2 (stmt); | |
316 | |
317 if (op0 == *ass_var | |
318 && (non_ass_var = independent_of_stmt_p (op1, stmt, call))) | |
319 ; | |
320 else if (op1 == *ass_var | |
321 && (non_ass_var = independent_of_stmt_p (op0, stmt, call))) | |
322 ; | |
323 else | |
324 return false; | |
325 | |
326 switch (code) | |
327 { | |
328 case PLUS_EXPR: | |
329 *a = non_ass_var; | |
330 *ass_var = dest; | |
331 return true; | |
332 | |
333 case MULT_EXPR: | |
334 *m = non_ass_var; | |
335 *ass_var = dest; | |
336 return true; | |
337 | |
338 /* TODO -- Handle other codes (NEGATE_EXPR, MINUS_EXPR, | |
339 POINTER_PLUS_EXPR). */ | |
340 | |
341 default: | |
342 return false; | |
343 } | |
344 } | |
345 | |
346 /* Propagate VAR through phis on edge E. */ | |
347 | |
348 static tree | |
349 propagate_through_phis (tree var, edge e) | |
350 { | |
351 basic_block dest = e->dest; | |
352 gimple_stmt_iterator gsi; | |
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353 |
0 | 354 for (gsi = gsi_start_phis (dest); !gsi_end_p (gsi); gsi_next (&gsi)) |
355 { | |
356 gimple phi = gsi_stmt (gsi); | |
357 if (PHI_ARG_DEF_FROM_EDGE (phi, e) == var) | |
358 return PHI_RESULT (phi); | |
359 } | |
360 return var; | |
361 } | |
362 | |
363 /* Finds tailcalls falling into basic block BB. The list of found tailcalls is | |
364 added to the start of RET. */ | |
365 | |
366 static void | |
367 find_tail_calls (basic_block bb, struct tailcall **ret) | |
368 { | |
369 tree ass_var = NULL_TREE, ret_var, func, param; | |
370 gimple stmt, call = NULL; | |
371 gimple_stmt_iterator gsi, agsi; | |
372 bool tail_recursion; | |
373 struct tailcall *nw; | |
374 edge e; | |
375 tree m, a; | |
376 basic_block abb; | |
377 size_t idx; | |
378 | |
379 if (!single_succ_p (bb)) | |
380 return; | |
381 | |
382 for (gsi = gsi_last_bb (bb); !gsi_end_p (gsi); gsi_prev (&gsi)) | |
383 { | |
384 stmt = gsi_stmt (gsi); | |
385 | |
386 /* Ignore labels. */ | |
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387 if (gimple_code (stmt) == GIMPLE_LABEL || is_gimple_debug (stmt)) |
0 | 388 continue; |
389 | |
390 /* Check for a call. */ | |
391 if (is_gimple_call (stmt)) | |
392 { | |
393 call = stmt; | |
394 ass_var = gimple_call_lhs (stmt); | |
395 break; | |
396 } | |
397 | |
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398 /* If the statement references memory or volatile operands, fail. */ |
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399 if (gimple_references_memory_p (stmt) |
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400 || gimple_has_volatile_ops (stmt)) |
0 | 401 return; |
402 } | |
403 | |
404 if (gsi_end_p (gsi)) | |
405 { | |
406 edge_iterator ei; | |
407 /* Recurse to the predecessors. */ | |
408 FOR_EACH_EDGE (e, ei, bb->preds) | |
409 find_tail_calls (e->src, ret); | |
410 | |
411 return; | |
412 } | |
413 | |
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414 /* If the LHS of our call is not just a simple register, we can't |
0 | 415 transform this into a tail or sibling call. This situation happens, |
416 in (e.g.) "*p = foo()" where foo returns a struct. In this case | |
417 we won't have a temporary here, but we need to carry out the side | |
418 effect anyway, so tailcall is impossible. | |
419 | |
420 ??? In some situations (when the struct is returned in memory via | |
421 invisible argument) we could deal with this, e.g. by passing 'p' | |
422 itself as that argument to foo, but it's too early to do this here, | |
423 and expand_call() will not handle it anyway. If it ever can, then | |
424 we need to revisit this here, to allow that situation. */ | |
425 if (ass_var && !is_gimple_reg (ass_var)) | |
426 return; | |
427 | |
428 /* We found the call, check whether it is suitable. */ | |
429 tail_recursion = false; | |
430 func = gimple_call_fndecl (call); | |
431 if (func == current_function_decl) | |
432 { | |
433 tree arg; | |
434 for (param = DECL_ARGUMENTS (func), idx = 0; | |
435 param && idx < gimple_call_num_args (call); | |
436 param = TREE_CHAIN (param), idx ++) | |
437 { | |
438 arg = gimple_call_arg (call, idx); | |
439 if (param != arg) | |
440 { | |
441 /* Make sure there are no problems with copying. The parameter | |
442 have a copyable type and the two arguments must have reasonably | |
443 equivalent types. The latter requirement could be relaxed if | |
444 we emitted a suitable type conversion statement. */ | |
445 if (!is_gimple_reg_type (TREE_TYPE (param)) | |
446 || !useless_type_conversion_p (TREE_TYPE (param), | |
447 TREE_TYPE (arg))) | |
448 break; | |
449 | |
450 /* The parameter should be a real operand, so that phi node | |
451 created for it at the start of the function has the meaning | |
452 of copying the value. This test implies is_gimple_reg_type | |
453 from the previous condition, however this one could be | |
454 relaxed by being more careful with copying the new value | |
455 of the parameter (emitting appropriate GIMPLE_ASSIGN and | |
456 updating the virtual operands). */ | |
457 if (!is_gimple_reg (param)) | |
458 break; | |
459 } | |
460 } | |
461 if (idx == gimple_call_num_args (call) && !param) | |
462 tail_recursion = true; | |
463 } | |
464 | |
465 /* Now check the statements after the call. None of them has virtual | |
466 operands, so they may only depend on the call through its return | |
467 value. The return value should also be dependent on each of them, | |
468 since we are running after dce. */ | |
469 m = NULL_TREE; | |
470 a = NULL_TREE; | |
471 | |
472 abb = bb; | |
473 agsi = gsi; | |
474 while (1) | |
475 { | |
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476 tree tmp_a = NULL_TREE; |
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477 tree tmp_m = NULL_TREE; |
0 | 478 gsi_next (&agsi); |
479 | |
480 while (gsi_end_p (agsi)) | |
481 { | |
482 ass_var = propagate_through_phis (ass_var, single_succ_edge (abb)); | |
483 abb = single_succ (abb); | |
484 agsi = gsi_start_bb (abb); | |
485 } | |
486 | |
487 stmt = gsi_stmt (agsi); | |
488 | |
489 if (gimple_code (stmt) == GIMPLE_LABEL) | |
490 continue; | |
491 | |
492 if (gimple_code (stmt) == GIMPLE_RETURN) | |
493 break; | |
494 | |
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495 if (is_gimple_debug (stmt)) |
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496 continue; |
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497 |
0 | 498 if (gimple_code (stmt) != GIMPLE_ASSIGN) |
499 return; | |
500 | |
501 /* This is a gimple assign. */ | |
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502 if (! process_assignment (stmt, gsi, &tmp_m, &tmp_a, &ass_var)) |
0 | 503 return; |
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504 |
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505 if (tmp_a) |
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506 { |
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507 if (a) |
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508 a = fold_build2 (PLUS_EXPR, TREE_TYPE (tmp_a), a, tmp_a); |
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509 else |
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510 a = tmp_a; |
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511 } |
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512 if (tmp_m) |
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513 { |
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514 if (m) |
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515 m = fold_build2 (MULT_EXPR, TREE_TYPE (tmp_m), m, tmp_m); |
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516 else |
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517 m = tmp_m; |
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518 |
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519 if (a) |
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520 a = fold_build2 (MULT_EXPR, TREE_TYPE (tmp_m), a, tmp_m); |
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521 } |
0 | 522 } |
523 | |
524 /* See if this is a tail call we can handle. */ | |
525 ret_var = gimple_return_retval (stmt); | |
526 | |
527 /* We may proceed if there either is no return value, or the return value | |
528 is identical to the call's return. */ | |
529 if (ret_var | |
530 && (ret_var != ass_var)) | |
531 return; | |
532 | |
533 /* If this is not a tail recursive call, we cannot handle addends or | |
534 multiplicands. */ | |
535 if (!tail_recursion && (m || a)) | |
536 return; | |
537 | |
538 nw = XNEW (struct tailcall); | |
539 | |
540 nw->call_gsi = gsi; | |
541 | |
542 nw->tail_recursion = tail_recursion; | |
543 | |
544 nw->mult = m; | |
545 nw->add = a; | |
546 | |
547 nw->next = *ret; | |
548 *ret = nw; | |
549 } | |
550 | |
551 /* Helper to insert PHI_ARGH to the phi of VAR in the destination of edge E. */ | |
552 | |
553 static void | |
554 add_successor_phi_arg (edge e, tree var, tree phi_arg) | |
555 { | |
556 gimple_stmt_iterator gsi; | |
557 | |
558 for (gsi = gsi_start_phis (e->dest); !gsi_end_p (gsi); gsi_next (&gsi)) | |
559 if (PHI_RESULT (gsi_stmt (gsi)) == var) | |
560 break; | |
561 | |
562 gcc_assert (!gsi_end_p (gsi)); | |
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563 add_phi_arg (gsi_stmt (gsi), phi_arg, e, UNKNOWN_LOCATION); |
0 | 564 } |
565 | |
566 /* Creates a GIMPLE statement which computes the operation specified by | |
567 CODE, OP0 and OP1 to a new variable with name LABEL and inserts the | |
568 statement in the position specified by GSI and UPDATE. Returns the | |
569 tree node of the statement's result. */ | |
570 | |
571 static tree | |
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572 adjust_return_value_with_ops (enum tree_code code, const char *label, |
0 | 573 tree op0, tree op1, gimple_stmt_iterator gsi, |
574 enum gsi_iterator_update update) | |
575 { | |
576 | |
577 tree ret_type = TREE_TYPE (DECL_RESULT (current_function_decl)); | |
578 tree tmp = create_tmp_var (ret_type, label); | |
579 gimple stmt = gimple_build_assign_with_ops (code, tmp, op0, op1); | |
580 tree result; | |
581 | |
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582 if (TREE_CODE (ret_type) == COMPLEX_TYPE |
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583 || TREE_CODE (ret_type) == VECTOR_TYPE) |
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584 DECL_GIMPLE_REG_P (tmp) = 1; |
0 | 585 add_referenced_var (tmp); |
586 result = make_ssa_name (tmp, stmt); | |
587 gimple_assign_set_lhs (stmt, result); | |
588 update_stmt (stmt); | |
589 gsi_insert_before (&gsi, stmt, update); | |
590 return result; | |
591 } | |
592 | |
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593 /* Creates a new GIMPLE statement that adjusts the value of accumulator ACC by |
0 | 594 the computation specified by CODE and OP1 and insert the statement |
595 at the position specified by GSI as a new statement. Returns new SSA name | |
596 of updated accumulator. */ | |
597 | |
598 static tree | |
599 update_accumulator_with_ops (enum tree_code code, tree acc, tree op1, | |
600 gimple_stmt_iterator gsi) | |
601 { | |
602 gimple stmt = gimple_build_assign_with_ops (code, SSA_NAME_VAR (acc), acc, | |
603 op1); | |
604 tree var = make_ssa_name (SSA_NAME_VAR (acc), stmt); | |
605 gimple_assign_set_lhs (stmt, var); | |
606 update_stmt (stmt); | |
607 gsi_insert_after (&gsi, stmt, GSI_NEW_STMT); | |
608 return var; | |
609 } | |
610 | |
611 /* Adjust the accumulator values according to A and M after GSI, and update | |
612 the phi nodes on edge BACK. */ | |
613 | |
614 static void | |
615 adjust_accumulator_values (gimple_stmt_iterator gsi, tree m, tree a, edge back) | |
616 { | |
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617 tree var, a_acc_arg, m_acc_arg; |
0 | 618 |
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619 if (m) |
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620 m = force_gimple_operand_gsi (&gsi, m, true, NULL, true, GSI_SAME_STMT); |
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621 if (a) |
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622 a = force_gimple_operand_gsi (&gsi, a, true, NULL, true, GSI_SAME_STMT); |
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623 |
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624 a_acc_arg = a_acc; |
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625 m_acc_arg = m_acc; |
0 | 626 if (a) |
627 { | |
628 if (m_acc) | |
629 { | |
630 if (integer_onep (a)) | |
631 var = m_acc; | |
632 else | |
633 var = adjust_return_value_with_ops (MULT_EXPR, "acc_tmp", m_acc, | |
634 a, gsi, GSI_NEW_STMT); | |
635 } | |
636 else | |
637 var = a; | |
638 | |
639 a_acc_arg = update_accumulator_with_ops (PLUS_EXPR, a_acc, var, gsi); | |
640 } | |
641 | |
642 if (m) | |
643 m_acc_arg = update_accumulator_with_ops (MULT_EXPR, m_acc, m, gsi); | |
644 | |
645 if (a_acc) | |
646 add_successor_phi_arg (back, a_acc, a_acc_arg); | |
647 | |
648 if (m_acc) | |
649 add_successor_phi_arg (back, m_acc, m_acc_arg); | |
650 } | |
651 | |
652 /* Adjust value of the return at the end of BB according to M and A | |
653 accumulators. */ | |
654 | |
655 static void | |
656 adjust_return_value (basic_block bb, tree m, tree a) | |
657 { | |
658 tree retval; | |
659 gimple ret_stmt = gimple_seq_last_stmt (bb_seq (bb)); | |
660 gimple_stmt_iterator gsi = gsi_last_bb (bb); | |
661 | |
662 gcc_assert (gimple_code (ret_stmt) == GIMPLE_RETURN); | |
663 | |
664 retval = gimple_return_retval (ret_stmt); | |
665 if (!retval || retval == error_mark_node) | |
666 return; | |
667 | |
668 if (m) | |
669 retval = adjust_return_value_with_ops (MULT_EXPR, "mul_tmp", m_acc, retval, | |
670 gsi, GSI_SAME_STMT); | |
671 if (a) | |
672 retval = adjust_return_value_with_ops (PLUS_EXPR, "acc_tmp", a_acc, retval, | |
673 gsi, GSI_SAME_STMT); | |
674 gimple_return_set_retval (ret_stmt, retval); | |
675 update_stmt (ret_stmt); | |
676 } | |
677 | |
678 /* Subtract COUNT and FREQUENCY from the basic block and it's | |
679 outgoing edge. */ | |
680 static void | |
681 decrease_profile (basic_block bb, gcov_type count, int frequency) | |
682 { | |
683 edge e; | |
684 bb->count -= count; | |
685 if (bb->count < 0) | |
686 bb->count = 0; | |
687 bb->frequency -= frequency; | |
688 if (bb->frequency < 0) | |
689 bb->frequency = 0; | |
690 if (!single_succ_p (bb)) | |
691 { | |
692 gcc_assert (!EDGE_COUNT (bb->succs)); | |
693 return; | |
694 } | |
695 e = single_succ_edge (bb); | |
696 e->count -= count; | |
697 if (e->count < 0) | |
698 e->count = 0; | |
699 } | |
700 | |
701 /* Returns true if argument PARAM of the tail recursive call needs to be copied | |
702 when the call is eliminated. */ | |
703 | |
704 static bool | |
705 arg_needs_copy_p (tree param) | |
706 { | |
707 tree def; | |
708 | |
709 if (!is_gimple_reg (param) || !var_ann (param)) | |
710 return false; | |
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711 |
0 | 712 /* Parameters that are only defined but never used need not be copied. */ |
713 def = gimple_default_def (cfun, param); | |
714 if (!def) | |
715 return false; | |
716 | |
717 return true; | |
718 } | |
719 | |
720 /* Eliminates tail call described by T. TMP_VARS is a list of | |
721 temporary variables used to copy the function arguments. */ | |
722 | |
723 static void | |
724 eliminate_tail_call (struct tailcall *t) | |
725 { | |
726 tree param, rslt; | |
727 gimple stmt, call; | |
728 tree arg; | |
729 size_t idx; | |
730 basic_block bb, first; | |
731 edge e; | |
732 gimple phi; | |
733 gimple_stmt_iterator gsi; | |
734 gimple orig_stmt; | |
735 | |
736 stmt = orig_stmt = gsi_stmt (t->call_gsi); | |
737 bb = gsi_bb (t->call_gsi); | |
738 | |
739 if (dump_file && (dump_flags & TDF_DETAILS)) | |
740 { | |
741 fprintf (dump_file, "Eliminated tail recursion in bb %d : ", | |
742 bb->index); | |
743 print_gimple_stmt (dump_file, stmt, 0, TDF_SLIM); | |
744 fprintf (dump_file, "\n"); | |
745 } | |
746 | |
747 gcc_assert (is_gimple_call (stmt)); | |
748 | |
749 first = single_succ (ENTRY_BLOCK_PTR); | |
750 | |
751 /* Remove the code after call_gsi that will become unreachable. The | |
752 possibly unreachable code in other blocks is removed later in | |
753 cfg cleanup. */ | |
754 gsi = t->call_gsi; | |
755 gsi_next (&gsi); | |
756 while (!gsi_end_p (gsi)) | |
757 { | |
758 gimple t = gsi_stmt (gsi); | |
759 /* Do not remove the return statement, so that redirect_edge_and_branch | |
760 sees how the block ends. */ | |
761 if (gimple_code (t) == GIMPLE_RETURN) | |
762 break; | |
763 | |
764 gsi_remove (&gsi, true); | |
765 release_defs (t); | |
766 } | |
767 | |
768 /* Number of executions of function has reduced by the tailcall. */ | |
769 e = single_succ_edge (gsi_bb (t->call_gsi)); | |
770 decrease_profile (EXIT_BLOCK_PTR, e->count, EDGE_FREQUENCY (e)); | |
771 decrease_profile (ENTRY_BLOCK_PTR, e->count, EDGE_FREQUENCY (e)); | |
772 if (e->dest != EXIT_BLOCK_PTR) | |
773 decrease_profile (e->dest, e->count, EDGE_FREQUENCY (e)); | |
774 | |
775 /* Replace the call by a jump to the start of function. */ | |
776 e = redirect_edge_and_branch (single_succ_edge (gsi_bb (t->call_gsi)), | |
777 first); | |
778 gcc_assert (e); | |
779 PENDING_STMT (e) = NULL; | |
780 | |
781 /* Add phi node entries for arguments. The ordering of the phi nodes should | |
782 be the same as the ordering of the arguments. */ | |
783 for (param = DECL_ARGUMENTS (current_function_decl), | |
784 idx = 0, gsi = gsi_start_phis (first); | |
785 param; | |
786 param = TREE_CHAIN (param), idx++) | |
787 { | |
788 if (!arg_needs_copy_p (param)) | |
789 continue; | |
790 | |
791 arg = gimple_call_arg (stmt, idx); | |
792 phi = gsi_stmt (gsi); | |
793 gcc_assert (param == SSA_NAME_VAR (PHI_RESULT (phi))); | |
794 | |
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795 add_phi_arg (phi, arg, e, gimple_location (stmt)); |
0 | 796 gsi_next (&gsi); |
797 } | |
798 | |
799 /* Update the values of accumulators. */ | |
800 adjust_accumulator_values (t->call_gsi, t->mult, t->add, e); | |
801 | |
802 call = gsi_stmt (t->call_gsi); | |
803 rslt = gimple_call_lhs (call); | |
804 if (rslt != NULL_TREE) | |
805 { | |
806 /* Result of the call will no longer be defined. So adjust the | |
807 SSA_NAME_DEF_STMT accordingly. */ | |
808 SSA_NAME_DEF_STMT (rslt) = gimple_build_nop (); | |
809 } | |
810 | |
811 gsi_remove (&t->call_gsi, true); | |
812 release_defs (call); | |
813 } | |
814 | |
815 /* Add phi nodes for the virtual operands defined in the function to the | |
816 header of the loop created by tail recursion elimination. | |
817 | |
818 Originally, we used to add phi nodes only for call clobbered variables, | |
819 as the value of the non-call clobbered ones obviously cannot be used | |
820 or changed within the recursive call. However, the local variables | |
821 from multiple calls now share the same location, so the virtual ssa form | |
822 requires us to say that the location dies on further iterations of the loop, | |
823 which requires adding phi nodes. | |
824 */ | |
825 static void | |
826 add_virtual_phis (void) | |
827 { | |
828 referenced_var_iterator rvi; | |
829 tree var; | |
830 | |
831 /* The problematic part is that there is no way how to know what | |
832 to put into phi nodes (there in fact does not have to be such | |
833 ssa name available). A solution would be to have an artificial | |
834 use/kill for all virtual operands in EXIT node. Unless we have | |
835 this, we cannot do much better than to rebuild the ssa form for | |
836 possibly affected virtual ssa names from scratch. */ | |
837 | |
838 FOR_EACH_REFERENCED_VAR (var, rvi) | |
839 { | |
840 if (!is_gimple_reg (var) && gimple_default_def (cfun, var) != NULL_TREE) | |
841 mark_sym_for_renaming (var); | |
842 } | |
843 } | |
844 | |
845 /* Optimizes the tailcall described by T. If OPT_TAILCALLS is true, also | |
846 mark the tailcalls for the sibcall optimization. */ | |
847 | |
848 static bool | |
849 optimize_tail_call (struct tailcall *t, bool opt_tailcalls) | |
850 { | |
851 if (t->tail_recursion) | |
852 { | |
853 eliminate_tail_call (t); | |
854 return true; | |
855 } | |
856 | |
857 if (opt_tailcalls) | |
858 { | |
859 gimple stmt = gsi_stmt (t->call_gsi); | |
860 | |
861 gimple_call_set_tail (stmt, true); | |
862 if (dump_file && (dump_flags & TDF_DETAILS)) | |
863 { | |
864 fprintf (dump_file, "Found tail call "); | |
865 print_gimple_stmt (dump_file, stmt, 0, dump_flags); | |
866 fprintf (dump_file, " in bb %i\n", (gsi_bb (t->call_gsi))->index); | |
867 } | |
868 } | |
869 | |
870 return false; | |
871 } | |
872 | |
873 /* Creates a tail-call accumulator of the same type as the return type of the | |
874 current function. LABEL is the name used to creating the temporary | |
875 variable for the accumulator. The accumulator will be inserted in the | |
876 phis of a basic block BB with single predecessor with an initial value | |
877 INIT converted to the current function return type. */ | |
878 | |
879 static tree | |
880 create_tailcall_accumulator (const char *label, basic_block bb, tree init) | |
881 { | |
882 tree ret_type = TREE_TYPE (DECL_RESULT (current_function_decl)); | |
883 tree tmp = create_tmp_var (ret_type, label); | |
884 gimple phi; | |
885 | |
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886 if (TREE_CODE (ret_type) == COMPLEX_TYPE |
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887 || TREE_CODE (ret_type) == VECTOR_TYPE) |
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888 DECL_GIMPLE_REG_P (tmp) = 1; |
0 | 889 add_referenced_var (tmp); |
890 phi = create_phi_node (tmp, bb); | |
891 /* RET_TYPE can be a float when -ffast-maths is enabled. */ | |
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892 add_phi_arg (phi, fold_convert (ret_type, init), single_pred_edge (bb), |
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893 UNKNOWN_LOCATION); |
0 | 894 return PHI_RESULT (phi); |
895 } | |
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896 |
0 | 897 /* Optimizes tail calls in the function, turning the tail recursion |
898 into iteration. */ | |
899 | |
900 static unsigned int | |
901 tree_optimize_tail_calls_1 (bool opt_tailcalls) | |
902 { | |
903 edge e; | |
904 bool phis_constructed = false; | |
905 struct tailcall *tailcalls = NULL, *act, *next; | |
906 bool changed = false; | |
907 basic_block first = single_succ (ENTRY_BLOCK_PTR); | |
908 tree param; | |
909 gimple stmt; | |
910 edge_iterator ei; | |
911 | |
912 if (!suitable_for_tail_opt_p ()) | |
913 return 0; | |
914 if (opt_tailcalls) | |
915 opt_tailcalls = suitable_for_tail_call_opt_p (); | |
916 | |
917 FOR_EACH_EDGE (e, ei, EXIT_BLOCK_PTR->preds) | |
918 { | |
919 /* Only traverse the normal exits, i.e. those that end with return | |
920 statement. */ | |
921 stmt = last_stmt (e->src); | |
922 | |
923 if (stmt | |
924 && gimple_code (stmt) == GIMPLE_RETURN) | |
925 find_tail_calls (e->src, &tailcalls); | |
926 } | |
927 | |
928 /* Construct the phi nodes and accumulators if necessary. */ | |
929 a_acc = m_acc = NULL_TREE; | |
930 for (act = tailcalls; act; act = act->next) | |
931 { | |
932 if (!act->tail_recursion) | |
933 continue; | |
934 | |
935 if (!phis_constructed) | |
936 { | |
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937 /* Ensure that there is only one predecessor of the block |
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938 or if there are existing degenerate PHI nodes. */ |
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939 if (!single_pred_p (first) |
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940 || !gimple_seq_empty_p (phi_nodes (first))) |
0 | 941 first = split_edge (single_succ_edge (ENTRY_BLOCK_PTR)); |
942 | |
943 /* Copy the args if needed. */ | |
944 for (param = DECL_ARGUMENTS (current_function_decl); | |
945 param; | |
946 param = TREE_CHAIN (param)) | |
947 if (arg_needs_copy_p (param)) | |
948 { | |
949 tree name = gimple_default_def (cfun, param); | |
950 tree new_name = make_ssa_name (param, SSA_NAME_DEF_STMT (name)); | |
951 gimple phi; | |
952 | |
953 set_default_def (param, new_name); | |
954 phi = create_phi_node (name, first); | |
955 SSA_NAME_DEF_STMT (name) = phi; | |
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956 add_phi_arg (phi, new_name, single_pred_edge (first), |
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957 EXPR_LOCATION (param)); |
0 | 958 } |
959 phis_constructed = true; | |
960 } | |
961 | |
962 if (act->add && !a_acc) | |
963 a_acc = create_tailcall_accumulator ("add_acc", first, | |
964 integer_zero_node); | |
965 | |
966 if (act->mult && !m_acc) | |
967 m_acc = create_tailcall_accumulator ("mult_acc", first, | |
968 integer_one_node); | |
969 } | |
970 | |
971 for (; tailcalls; tailcalls = next) | |
972 { | |
973 next = tailcalls->next; | |
974 changed |= optimize_tail_call (tailcalls, opt_tailcalls); | |
975 free (tailcalls); | |
976 } | |
977 | |
978 if (a_acc || m_acc) | |
979 { | |
980 /* Modify the remaining return statements. */ | |
981 FOR_EACH_EDGE (e, ei, EXIT_BLOCK_PTR->preds) | |
982 { | |
983 stmt = last_stmt (e->src); | |
984 | |
985 if (stmt | |
986 && gimple_code (stmt) == GIMPLE_RETURN) | |
987 adjust_return_value (e->src, m_acc, a_acc); | |
988 } | |
989 } | |
990 | |
991 if (changed) | |
992 free_dominance_info (CDI_DOMINATORS); | |
993 | |
994 if (phis_constructed) | |
995 add_virtual_phis (); | |
996 if (changed) | |
997 return TODO_cleanup_cfg | TODO_update_ssa_only_virtuals; | |
998 return 0; | |
999 } | |
1000 | |
1001 static unsigned int | |
1002 execute_tail_recursion (void) | |
1003 { | |
1004 return tree_optimize_tail_calls_1 (false); | |
1005 } | |
1006 | |
1007 static bool | |
1008 gate_tail_calls (void) | |
1009 { | |
1010 return flag_optimize_sibling_calls != 0 && dbg_cnt (tail_call); | |
1011 } | |
1012 | |
1013 static unsigned int | |
1014 execute_tail_calls (void) | |
1015 { | |
1016 return tree_optimize_tail_calls_1 (true); | |
1017 } | |
1018 | |
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1019 struct gimple_opt_pass pass_tail_recursion = |
0 | 1020 { |
1021 { | |
1022 GIMPLE_PASS, | |
1023 "tailr", /* name */ | |
1024 gate_tail_calls, /* gate */ | |
1025 execute_tail_recursion, /* execute */ | |
1026 NULL, /* sub */ | |
1027 NULL, /* next */ | |
1028 0, /* static_pass_number */ | |
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1029 TV_NONE, /* tv_id */ |
0 | 1030 PROP_cfg | PROP_ssa, /* properties_required */ |
1031 0, /* properties_provided */ | |
1032 0, /* properties_destroyed */ | |
1033 0, /* todo_flags_start */ | |
1034 TODO_dump_func | TODO_verify_ssa /* todo_flags_finish */ | |
1035 } | |
1036 }; | |
1037 | |
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1038 struct gimple_opt_pass pass_tail_calls = |
0 | 1039 { |
1040 { | |
1041 GIMPLE_PASS, | |
1042 "tailc", /* name */ | |
1043 gate_tail_calls, /* gate */ | |
1044 execute_tail_calls, /* execute */ | |
1045 NULL, /* sub */ | |
1046 NULL, /* next */ | |
1047 0, /* static_pass_number */ | |
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1048 TV_NONE, /* tv_id */ |
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1049 PROP_cfg | PROP_ssa, /* properties_required */ |
0 | 1050 0, /* properties_provided */ |
1051 0, /* properties_destroyed */ | |
1052 0, /* todo_flags_start */ | |
1053 TODO_dump_func | TODO_verify_ssa /* todo_flags_finish */ | |
1054 } | |
1055 }; |