Mercurial > hg > CbC > CbC_gcc
annotate gcc/tree-tailcall.c @ 158:494b0b89df80 default tip
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| author | Shinji KONO <kono@ie.u-ryukyu.ac.jp> |
|---|---|
| date | Mon, 25 May 2020 18:13:55 +0900 |
| parents | 1830386684a0 |
| children |
| rev | line source |
|---|---|
| 0 | 1 /* Tail call optimization on trees. |
| 145 | 2 Copyright (C) 2003-2020 Free Software Foundation, Inc. |
| 0 | 3 |
| 4 This file is part of GCC. | |
| 5 | |
| 6 GCC is free software; you can redistribute it and/or modify | |
| 7 it under the terms of the GNU General Public License as published by | |
| 8 the Free Software Foundation; either version 3, or (at your option) | |
| 9 any later version. | |
| 10 | |
| 11 GCC is distributed in the hope that it will be useful, | |
| 12 but WITHOUT ANY WARRANTY; without even the implied warranty of | |
| 13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
| 14 GNU General Public License for more details. | |
| 15 | |
| 16 You should have received a copy of the GNU General Public License | |
| 17 along with GCC; see the file COPYING3. If not see | |
| 18 <http://www.gnu.org/licenses/>. */ | |
| 19 | |
| 20 #include "config.h" | |
| 21 #include "system.h" | |
| 22 #include "coretypes.h" | |
| 111 | 23 #include "backend.h" |
| 24 #include "rtl.h" | |
| 0 | 25 #include "tree.h" |
| 111 | 26 #include "gimple.h" |
| 27 #include "cfghooks.h" | |
| 28 #include "tree-pass.h" | |
| 29 #include "ssa.h" | |
| 30 #include "cgraph.h" | |
|
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31 #include "gimple-pretty-print.h" |
| 111 | 32 #include "fold-const.h" |
| 33 #include "stor-layout.h" | |
| 34 #include "gimple-iterator.h" | |
| 35 #include "gimplify-me.h" | |
| 36 #include "tree-cfg.h" | |
| 37 #include "tree-into-ssa.h" | |
| 38 #include "tree-dfa.h" | |
| 0 | 39 #include "except.h" |
| 145 | 40 #include "tree-eh.h" |
| 0 | 41 #include "dbgcnt.h" |
| 111 | 42 #include "cfgloop.h" |
| 43 #include "common/common-target.h" | |
| 44 #include "ipa-utils.h" | |
| 145 | 45 #include "tree-ssa-live.h" |
| 0 | 46 |
| 47 /* The file implements the tail recursion elimination. It is also used to | |
| 48 analyze the tail calls in general, passing the results to the rtl level | |
| 49 where they are used for sibcall optimization. | |
| 50 | |
| 51 In addition to the standard tail recursion elimination, we handle the most | |
| 52 trivial cases of making the call tail recursive by creating accumulators. | |
| 53 For example the following function | |
| 54 | |
| 55 int sum (int n) | |
| 56 { | |
| 57 if (n > 0) | |
| 58 return n + sum (n - 1); | |
| 59 else | |
| 60 return 0; | |
| 61 } | |
| 62 | |
| 63 is transformed into | |
| 64 | |
| 65 int sum (int n) | |
| 66 { | |
| 67 int acc = 0; | |
| 68 | |
| 69 while (n > 0) | |
| 70 acc += n--; | |
| 71 | |
| 72 return acc; | |
| 73 } | |
| 74 | |
|
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75 To do this, we maintain two accumulators (a_acc and m_acc) that indicate |
| 0 | 76 when we reach the return x statement, we should return a_acc + x * m_acc |
| 77 instead. They are initially initialized to 0 and 1, respectively, | |
| 78 so the semantics of the function is obviously preserved. If we are | |
| 79 guaranteed that the value of the accumulator never change, we | |
| 80 omit the accumulator. | |
| 81 | |
| 82 There are three cases how the function may exit. The first one is | |
| 83 handled in adjust_return_value, the other two in adjust_accumulator_values | |
| 84 (the second case is actually a special case of the third one and we | |
| 85 present it separately just for clarity): | |
| 86 | |
| 87 1) Just return x, where x is not in any of the remaining special shapes. | |
| 88 We rewrite this to a gimple equivalent of return m_acc * x + a_acc. | |
|
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89 |
| 0 | 90 2) return f (...), where f is the current function, is rewritten in a |
| 91 classical tail-recursion elimination way, into assignment of arguments | |
| 92 and jump to the start of the function. Values of the accumulators | |
| 93 are unchanged. | |
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94 |
| 0 | 95 3) return a + m * f(...), where a and m do not depend on call to f. |
| 96 To preserve the semantics described before we want this to be rewritten | |
| 97 in such a way that we finally return | |
| 98 | |
| 99 a_acc + (a + m * f(...)) * m_acc = (a_acc + a * m_acc) + (m * m_acc) * f(...). | |
| 100 | |
| 101 I.e. we increase a_acc by a * m_acc, multiply m_acc by m and | |
| 102 eliminate the tail call to f. Special cases when the value is just | |
| 103 added or just multiplied are obtained by setting a = 0 or m = 1. | |
| 104 | |
| 105 TODO -- it is possible to do similar tricks for other operations. */ | |
| 106 | |
| 107 /* A structure that describes the tailcall. */ | |
| 108 | |
| 109 struct tailcall | |
| 110 { | |
| 111 /* The iterator pointing to the call statement. */ | |
| 112 gimple_stmt_iterator call_gsi; | |
| 113 | |
| 114 /* True if it is a call to the current function. */ | |
| 115 bool tail_recursion; | |
| 116 | |
| 117 /* The return value of the caller is mult * f + add, where f is the return | |
| 118 value of the call. */ | |
| 119 tree mult, add; | |
| 120 | |
| 121 /* Next tailcall in the chain. */ | |
| 122 struct tailcall *next; | |
| 123 }; | |
| 124 | |
| 125 /* The variables holding the value of multiplicative and additive | |
| 126 accumulator. */ | |
| 127 static tree m_acc, a_acc; | |
| 128 | |
| 145 | 129 /* Bitmap with a bit for each function parameter which is set to true if we |
| 130 have to copy the parameter for conversion of tail-recursive calls. */ | |
| 131 | |
| 132 static bitmap tailr_arg_needs_copy; | |
| 133 | |
| 0 | 134 static bool optimize_tail_call (struct tailcall *, bool); |
| 135 static void eliminate_tail_call (struct tailcall *); | |
| 136 | |
| 137 /* Returns false when the function is not suitable for tail call optimization | |
| 138 from some reason (e.g. if it takes variable number of arguments). */ | |
| 139 | |
| 140 static bool | |
| 141 suitable_for_tail_opt_p (void) | |
| 142 { | |
| 143 if (cfun->stdarg) | |
| 144 return false; | |
| 145 | |
| 146 return true; | |
| 147 } | |
| 145 | 148 |
| 0 | 149 /* Returns false when the function is not suitable for tail call optimization |
| 111 | 150 for some reason (e.g. if it takes variable number of arguments). |
| 0 | 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. */ | |
| 111 | 167 if (targetm_common.except_unwind_info (&global_options) == UI_SJLJ |
|
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168 && current_function_has_exception_handlers ()) |
| 0 | 169 return false; |
| 170 | |
| 171 /* Any function that calls setjmp might have longjmp called from | |
| 172 any called function. ??? We really should represent this | |
| 173 properly in the CFG so that this needn't be special cased. */ | |
| 174 if (cfun->calls_setjmp) | |
| 175 return false; | |
| 176 | |
| 145 | 177 /* Various targets don't handle tail calls correctly in functions |
| 178 that call __builtin_eh_return. */ | |
| 179 if (cfun->calls_eh_return) | |
| 180 return false; | |
| 181 | |
| 0 | 182 /* ??? It is OK if the argument of a function is taken in some cases, |
| 183 but not in all cases. See PR15387 and PR19616. Revisit for 4.1. */ | |
| 184 for (param = DECL_ARGUMENTS (current_function_decl); | |
| 185 param; | |
|
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186 param = DECL_CHAIN (param)) |
| 0 | 187 if (TREE_ADDRESSABLE (param)) |
| 188 return false; | |
| 189 | |
| 190 return true; | |
| 191 } | |
| 192 | |
| 193 /* Checks whether the expression EXPR in stmt AT is independent of the | |
| 194 statement pointed to by GSI (in a sense that we already know EXPR's value | |
| 195 at GSI). We use the fact that we are only called from the chain of | |
| 196 basic blocks that have only single successor. Returns the expression | |
| 197 containing the value of EXPR at GSI. */ | |
| 198 | |
| 199 static tree | |
| 111 | 200 independent_of_stmt_p (tree expr, gimple *at, gimple_stmt_iterator gsi, |
| 201 bitmap to_move) | |
| 0 | 202 { |
| 203 basic_block bb, call_bb, at_bb; | |
| 204 edge e; | |
| 205 edge_iterator ei; | |
| 206 | |
| 207 if (is_gimple_min_invariant (expr)) | |
| 208 return expr; | |
| 209 | |
| 210 if (TREE_CODE (expr) != SSA_NAME) | |
| 211 return NULL_TREE; | |
| 212 | |
| 111 | 213 if (bitmap_bit_p (to_move, SSA_NAME_VERSION (expr))) |
| 214 return expr; | |
| 215 | |
| 0 | 216 /* Mark the blocks in the chain leading to the end. */ |
| 217 at_bb = gimple_bb (at); | |
| 218 call_bb = gimple_bb (gsi_stmt (gsi)); | |
| 219 for (bb = call_bb; bb != at_bb; bb = single_succ (bb)) | |
| 220 bb->aux = &bb->aux; | |
| 221 bb->aux = &bb->aux; | |
| 222 | |
| 223 while (1) | |
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224 { |
| 0 | 225 at = SSA_NAME_DEF_STMT (expr); |
| 226 bb = gimple_bb (at); | |
| 227 | |
| 228 /* The default definition or defined before the chain. */ | |
| 229 if (!bb || !bb->aux) | |
| 230 break; | |
| 231 | |
| 232 if (bb == call_bb) | |
| 233 { | |
| 234 for (; !gsi_end_p (gsi); gsi_next (&gsi)) | |
| 235 if (gsi_stmt (gsi) == at) | |
| 236 break; | |
| 237 | |
| 238 if (!gsi_end_p (gsi)) | |
| 239 expr = NULL_TREE; | |
| 240 break; | |
| 241 } | |
| 242 | |
| 243 if (gimple_code (at) != GIMPLE_PHI) | |
| 244 { | |
| 245 expr = NULL_TREE; | |
| 246 break; | |
| 247 } | |
| 248 | |
| 249 FOR_EACH_EDGE (e, ei, bb->preds) | |
| 250 if (e->src->aux) | |
| 251 break; | |
| 252 gcc_assert (e); | |
| 253 | |
| 254 expr = PHI_ARG_DEF_FROM_EDGE (at, e); | |
| 255 if (TREE_CODE (expr) != SSA_NAME) | |
| 256 { | |
| 257 /* The value is a constant. */ | |
| 258 break; | |
| 259 } | |
| 260 } | |
| 261 | |
| 262 /* Unmark the blocks. */ | |
| 263 for (bb = call_bb; bb != at_bb; bb = single_succ (bb)) | |
| 264 bb->aux = NULL; | |
| 265 bb->aux = NULL; | |
| 266 | |
| 267 return expr; | |
| 268 } | |
| 269 | |
| 111 | 270 enum par { FAIL, OK, TRY_MOVE }; |
| 271 | |
| 0 | 272 /* Simulates the effect of an assignment STMT on the return value of the tail |
| 273 recursive CALL passed in ASS_VAR. M and A are the multiplicative and the | |
| 274 additive factor for the real return value. */ | |
| 275 | |
| 111 | 276 static par |
| 277 process_assignment (gassign *stmt, | |
| 278 gimple_stmt_iterator call, tree *m, | |
| 279 tree *a, tree *ass_var, bitmap to_move) | |
| 0 | 280 { |
|
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281 tree op0, op1 = NULL_TREE, non_ass_var = NULL_TREE; |
| 0 | 282 tree dest = gimple_assign_lhs (stmt); |
| 283 enum tree_code code = gimple_assign_rhs_code (stmt); | |
| 284 enum gimple_rhs_class rhs_class = get_gimple_rhs_class (code); | |
| 285 tree src_var = gimple_assign_rhs1 (stmt); | |
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286 |
| 0 | 287 /* See if this is a simple copy operation of an SSA name to the function |
| 288 result. In that case we may have a simple tail call. Ignore type | |
| 289 conversions that can never produce extra code between the function | |
| 290 call and the function return. */ | |
| 291 if ((rhs_class == GIMPLE_SINGLE_RHS || gimple_assign_cast_p (stmt)) | |
| 111 | 292 && src_var == *ass_var) |
| 0 | 293 { |
| 294 /* Reject a tailcall if the type conversion might need | |
| 295 additional code. */ | |
| 111 | 296 if (gimple_assign_cast_p (stmt)) |
| 297 { | |
| 298 if (TYPE_MODE (TREE_TYPE (dest)) != TYPE_MODE (TREE_TYPE (src_var))) | |
| 299 return FAIL; | |
| 0 | 300 |
| 111 | 301 /* Even if the type modes are the same, if the precision of the |
| 302 type is smaller than mode's precision, | |
| 303 reduce_to_bit_field_precision would generate additional code. */ | |
| 304 if (INTEGRAL_TYPE_P (TREE_TYPE (dest)) | |
| 305 && !type_has_mode_precision_p (TREE_TYPE (dest))) | |
| 306 return FAIL; | |
| 307 } | |
| 0 | 308 |
| 309 *ass_var = dest; | |
| 111 | 310 return OK; |
| 0 | 311 } |
| 312 | |
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313 switch (rhs_class) |
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314 { |
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315 case GIMPLE_BINARY_RHS: |
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316 op1 = gimple_assign_rhs2 (stmt); |
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317 |
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318 /* Fall through. */ |
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319 |
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320 case GIMPLE_UNARY_RHS: |
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321 op0 = gimple_assign_rhs1 (stmt); |
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322 break; |
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323 |
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324 default: |
| 111 | 325 return FAIL; |
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326 } |
| 0 | 327 |
| 328 /* Accumulator optimizations will reverse the order of operations. | |
| 329 We can only do that for floating-point types if we're assuming | |
| 330 that addition and multiplication are associative. */ | |
| 331 if (!flag_associative_math) | |
| 332 if (FLOAT_TYPE_P (TREE_TYPE (DECL_RESULT (current_function_decl)))) | |
| 111 | 333 return FAIL; |
| 0 | 334 |
| 111 | 335 if (rhs_class == GIMPLE_UNARY_RHS |
| 336 && op0 == *ass_var) | |
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337 ; |
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338 else if (op0 == *ass_var |
| 111 | 339 && (non_ass_var = independent_of_stmt_p (op1, stmt, call, |
| 340 to_move))) | |
| 0 | 341 ; |
| 342 else if (op1 == *ass_var | |
| 111 | 343 && (non_ass_var = independent_of_stmt_p (op0, stmt, call, |
| 344 to_move))) | |
| 0 | 345 ; |
| 346 else | |
| 111 | 347 return TRY_MOVE; |
| 0 | 348 |
| 349 switch (code) | |
| 350 { | |
| 351 case PLUS_EXPR: | |
| 352 *a = non_ass_var; | |
| 353 *ass_var = dest; | |
| 111 | 354 return OK; |
| 355 | |
| 356 case POINTER_PLUS_EXPR: | |
| 357 if (op0 != *ass_var) | |
| 358 return FAIL; | |
| 359 *a = non_ass_var; | |
| 360 *ass_var = dest; | |
| 361 return OK; | |
| 0 | 362 |
| 363 case MULT_EXPR: | |
| 364 *m = non_ass_var; | |
| 365 *ass_var = dest; | |
| 111 | 366 return OK; |
| 0 | 367 |
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368 case NEGATE_EXPR: |
| 111 | 369 *m = build_minus_one_cst (TREE_TYPE (op0)); |
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370 *ass_var = dest; |
| 111 | 371 return OK; |
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372 |
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373 case MINUS_EXPR: |
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374 if (*ass_var == op0) |
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375 *a = fold_build1 (NEGATE_EXPR, TREE_TYPE (non_ass_var), non_ass_var); |
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376 else |
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377 { |
| 111 | 378 *m = build_minus_one_cst (TREE_TYPE (non_ass_var)); |
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379 *a = fold_build1 (NEGATE_EXPR, TREE_TYPE (non_ass_var), non_ass_var); |
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380 } |
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381 |
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382 *ass_var = dest; |
| 111 | 383 return OK; |
| 0 | 384 |
| 385 default: | |
| 111 | 386 return FAIL; |
| 0 | 387 } |
| 388 } | |
| 389 | |
| 390 /* Propagate VAR through phis on edge E. */ | |
| 391 | |
| 392 static tree | |
| 393 propagate_through_phis (tree var, edge e) | |
| 394 { | |
| 395 basic_block dest = e->dest; | |
| 111 | 396 gphi_iterator gsi; |
|
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397 |
| 0 | 398 for (gsi = gsi_start_phis (dest); !gsi_end_p (gsi); gsi_next (&gsi)) |
| 399 { | |
| 111 | 400 gphi *phi = gsi.phi (); |
| 0 | 401 if (PHI_ARG_DEF_FROM_EDGE (phi, e) == var) |
| 402 return PHI_RESULT (phi); | |
| 403 } | |
| 404 return var; | |
| 405 } | |
| 406 | |
| 145 | 407 /* Argument for compute_live_vars/live_vars_at_stmt and what compute_live_vars |
| 408 returns. Computed lazily, but just once for the function. */ | |
| 409 static live_vars_map *live_vars; | |
| 410 static vec<bitmap_head> live_vars_vec; | |
| 411 | |
| 0 | 412 /* Finds tailcalls falling into basic block BB. The list of found tailcalls is |
| 413 added to the start of RET. */ | |
| 414 | |
| 415 static void | |
| 416 find_tail_calls (basic_block bb, struct tailcall **ret) | |
| 417 { | |
| 418 tree ass_var = NULL_TREE, ret_var, func, param; | |
| 111 | 419 gimple *stmt; |
| 420 gcall *call = NULL; | |
| 0 | 421 gimple_stmt_iterator gsi, agsi; |
| 422 bool tail_recursion; | |
| 423 struct tailcall *nw; | |
| 424 edge e; | |
| 425 tree m, a; | |
| 426 basic_block abb; | |
| 427 size_t idx; | |
|
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428 tree var; |
| 0 | 429 |
| 430 if (!single_succ_p (bb)) | |
| 431 return; | |
| 432 | |
| 433 for (gsi = gsi_last_bb (bb); !gsi_end_p (gsi); gsi_prev (&gsi)) | |
| 434 { | |
| 435 stmt = gsi_stmt (gsi); | |
| 436 | |
| 111 | 437 /* Ignore labels, returns, nops, clobbers and debug stmts. */ |
| 438 if (gimple_code (stmt) == GIMPLE_LABEL | |
| 439 || gimple_code (stmt) == GIMPLE_RETURN | |
| 440 || gimple_code (stmt) == GIMPLE_NOP | |
| 441 || gimple_code (stmt) == GIMPLE_PREDICT | |
| 442 || gimple_clobber_p (stmt) | |
| 443 || is_gimple_debug (stmt)) | |
| 0 | 444 continue; |
| 445 | |
| 446 /* Check for a call. */ | |
| 447 if (is_gimple_call (stmt)) | |
| 448 { | |
| 111 | 449 call = as_a <gcall *> (stmt); |
| 450 ass_var = gimple_call_lhs (call); | |
| 0 | 451 break; |
| 452 } | |
| 453 | |
| 111 | 454 /* Allow simple copies between local variables, even if they're |
| 455 aggregates. */ | |
| 456 if (is_gimple_assign (stmt) | |
| 457 && auto_var_in_fn_p (gimple_assign_lhs (stmt), cfun->decl) | |
| 458 && auto_var_in_fn_p (gimple_assign_rhs1 (stmt), cfun->decl)) | |
| 459 continue; | |
| 460 | |
|
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461 /* If the statement references memory or volatile operands, fail. */ |
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462 if (gimple_references_memory_p (stmt) |
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463 || gimple_has_volatile_ops (stmt)) |
| 0 | 464 return; |
| 465 } | |
| 466 | |
| 467 if (gsi_end_p (gsi)) | |
| 468 { | |
| 469 edge_iterator ei; | |
| 470 /* Recurse to the predecessors. */ | |
| 471 FOR_EACH_EDGE (e, ei, bb->preds) | |
| 472 find_tail_calls (e->src, ret); | |
| 473 | |
| 474 return; | |
| 475 } | |
| 476 | |
| 111 | 477 /* If the LHS of our call is not just a simple register or local |
| 478 variable, we can't transform this into a tail or sibling call. | |
| 479 This situation happens, in (e.g.) "*p = foo()" where foo returns a | |
| 480 struct. In this case we won't have a temporary here, but we need | |
| 481 to carry out the side effect anyway, so tailcall is impossible. | |
| 0 | 482 |
| 483 ??? In some situations (when the struct is returned in memory via | |
| 484 invisible argument) we could deal with this, e.g. by passing 'p' | |
| 485 itself as that argument to foo, but it's too early to do this here, | |
| 486 and expand_call() will not handle it anyway. If it ever can, then | |
| 487 we need to revisit this here, to allow that situation. */ | |
| 111 | 488 if (ass_var |
| 489 && !is_gimple_reg (ass_var) | |
| 490 && !auto_var_in_fn_p (ass_var, cfun->decl)) | |
| 0 | 491 return; |
| 492 | |
| 145 | 493 /* If the call might throw an exception that wouldn't propagate out of |
| 494 cfun, we can't transform to a tail or sibling call (82081). */ | |
| 495 if (stmt_could_throw_p (cfun, stmt) | |
| 496 && !stmt_can_throw_external (cfun, stmt)) | |
| 497 return; | |
| 498 | |
| 499 /* If the function returns a value, then at present, the tail call | |
| 500 must return the same type of value. There is conceptually a copy | |
| 501 between the object returned by the tail call candidate and the | |
| 502 object returned by CFUN itself. | |
| 503 | |
| 504 This means that if we have: | |
| 505 | |
| 506 lhs = f (&<retval>); // f reads from <retval> | |
| 507 // (lhs is usually also <retval>) | |
| 508 | |
| 509 there is a copy between the temporary object returned by f and lhs, | |
| 510 meaning that any use of <retval> in f occurs before the assignment | |
| 511 to lhs begins. Thus the <retval> that is live on entry to the call | |
| 512 to f is really an independent local variable V that happens to be | |
| 513 stored in the RESULT_DECL rather than a local VAR_DECL. | |
| 514 | |
| 515 Turning this into a tail call would remove the copy and make the | |
| 516 lifetimes of the return value and V overlap. The same applies to | |
| 517 tail recursion, since if f can read from <retval>, we have to assume | |
| 518 that CFUN might already have written to <retval> before the call. | |
| 519 | |
| 520 The problem doesn't apply when <retval> is passed by value, but that | |
| 521 isn't a case we handle anyway. */ | |
| 522 tree result_decl = DECL_RESULT (cfun->decl); | |
| 523 if (result_decl | |
| 524 && may_be_aliased (result_decl) | |
| 525 && ref_maybe_used_by_stmt_p (call, result_decl)) | |
| 526 return; | |
| 527 | |
| 0 | 528 /* We found the call, check whether it is suitable. */ |
| 529 tail_recursion = false; | |
| 530 func = gimple_call_fndecl (call); | |
| 111 | 531 if (func |
| 131 | 532 && !fndecl_built_in_p (func) |
| 111 | 533 && recursive_call_p (current_function_decl, func)) |
| 0 | 534 { |
| 535 tree arg; | |
|
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536 |
| 131 | 537 for (param = DECL_ARGUMENTS (current_function_decl), idx = 0; |
| 0 | 538 param && idx < gimple_call_num_args (call); |
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539 param = DECL_CHAIN (param), idx ++) |
| 0 | 540 { |
| 541 arg = gimple_call_arg (call, idx); | |
| 542 if (param != arg) | |
| 543 { | |
| 544 /* Make sure there are no problems with copying. The parameter | |
| 545 have a copyable type and the two arguments must have reasonably | |
| 546 equivalent types. The latter requirement could be relaxed if | |
| 547 we emitted a suitable type conversion statement. */ | |
| 548 if (!is_gimple_reg_type (TREE_TYPE (param)) | |
| 549 || !useless_type_conversion_p (TREE_TYPE (param), | |
| 550 TREE_TYPE (arg))) | |
| 551 break; | |
| 552 | |
| 553 /* The parameter should be a real operand, so that phi node | |
| 554 created for it at the start of the function has the meaning | |
| 555 of copying the value. This test implies is_gimple_reg_type | |
| 556 from the previous condition, however this one could be | |
| 557 relaxed by being more careful with copying the new value | |
| 558 of the parameter (emitting appropriate GIMPLE_ASSIGN and | |
| 559 updating the virtual operands). */ | |
| 560 if (!is_gimple_reg (param)) | |
| 561 break; | |
| 562 } | |
| 563 } | |
| 564 if (idx == gimple_call_num_args (call) && !param) | |
| 565 tail_recursion = true; | |
| 566 } | |
| 567 | |
| 145 | 568 /* Compute live vars if not computed yet. */ |
| 569 if (live_vars == NULL) | |
| 570 { | |
| 571 unsigned int cnt = 0; | |
| 572 FOR_EACH_LOCAL_DECL (cfun, idx, var) | |
| 573 if (VAR_P (var) | |
| 574 && auto_var_in_fn_p (var, cfun->decl) | |
| 575 && may_be_aliased (var)) | |
| 576 { | |
| 577 if (live_vars == NULL) | |
| 578 live_vars = new live_vars_map; | |
| 579 live_vars->put (DECL_UID (var), cnt++); | |
| 580 } | |
| 581 if (live_vars) | |
| 582 live_vars_vec = compute_live_vars (cfun, live_vars); | |
| 583 } | |
| 584 | |
| 585 /* Determine a bitmap of variables which are still in scope after the | |
| 586 call. */ | |
| 587 bitmap local_live_vars = NULL; | |
| 588 if (live_vars) | |
| 589 local_live_vars = live_vars_at_stmt (live_vars_vec, live_vars, call); | |
| 590 | |
| 111 | 591 /* Make sure the tail invocation of this function does not indirectly |
| 592 refer to local variables. (Passing variables directly by value | |
| 593 is OK.) */ | |
| 594 FOR_EACH_LOCAL_DECL (cfun, idx, var) | |
|
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595 { |
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596 if (TREE_CODE (var) != PARM_DECL |
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597 && auto_var_in_fn_p (var, cfun->decl) |
| 111 | 598 && may_be_aliased (var) |
|
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599 && (ref_maybe_used_by_stmt_p (call, var) |
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600 || call_may_clobber_ref_p (call, var))) |
| 145 | 601 { |
| 602 if (!VAR_P (var)) | |
| 603 { | |
| 604 if (local_live_vars) | |
| 605 BITMAP_FREE (local_live_vars); | |
| 606 return; | |
| 607 } | |
| 608 else | |
| 609 { | |
| 610 unsigned int *v = live_vars->get (DECL_UID (var)); | |
| 611 if (bitmap_bit_p (local_live_vars, *v)) | |
| 612 { | |
| 613 BITMAP_FREE (local_live_vars); | |
| 614 return; | |
| 615 } | |
| 616 } | |
| 617 } | |
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618 } |
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619 |
| 145 | 620 if (local_live_vars) |
| 621 BITMAP_FREE (local_live_vars); | |
| 622 | |
| 0 | 623 /* Now check the statements after the call. None of them has virtual |
| 624 operands, so they may only depend on the call through its return | |
| 625 value. The return value should also be dependent on each of them, | |
| 626 since we are running after dce. */ | |
| 627 m = NULL_TREE; | |
| 628 a = NULL_TREE; | |
| 111 | 629 auto_bitmap to_move_defs; |
| 630 auto_vec<gimple *> to_move_stmts; | |
| 0 | 631 |
| 632 abb = bb; | |
| 633 agsi = gsi; | |
| 634 while (1) | |
| 635 { | |
|
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636 tree tmp_a = NULL_TREE; |
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637 tree tmp_m = NULL_TREE; |
| 0 | 638 gsi_next (&agsi); |
| 639 | |
| 640 while (gsi_end_p (agsi)) | |
| 641 { | |
| 642 ass_var = propagate_through_phis (ass_var, single_succ_edge (abb)); | |
| 643 abb = single_succ (abb); | |
| 644 agsi = gsi_start_bb (abb); | |
| 645 } | |
| 646 | |
| 647 stmt = gsi_stmt (agsi); | |
| 648 if (gimple_code (stmt) == GIMPLE_RETURN) | |
| 649 break; | |
| 650 | |
| 111 | 651 if (gimple_code (stmt) == GIMPLE_LABEL |
| 652 || gimple_code (stmt) == GIMPLE_NOP | |
| 653 || gimple_code (stmt) == GIMPLE_PREDICT | |
| 654 || gimple_clobber_p (stmt) | |
| 655 || is_gimple_debug (stmt)) | |
|
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656 continue; |
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657 |
| 0 | 658 if (gimple_code (stmt) != GIMPLE_ASSIGN) |
| 659 return; | |
| 660 | |
| 661 /* This is a gimple assign. */ | |
| 111 | 662 par ret = process_assignment (as_a <gassign *> (stmt), gsi, |
| 663 &tmp_m, &tmp_a, &ass_var, to_move_defs); | |
| 664 if (ret == FAIL) | |
| 0 | 665 return; |
| 111 | 666 else if (ret == TRY_MOVE) |
| 667 { | |
| 668 if (! tail_recursion) | |
| 669 return; | |
| 670 /* Do not deal with checking dominance, the real fix is to | |
| 671 do path isolation for the transform phase anyway, removing | |
| 672 the need to compute the accumulators with new stmts. */ | |
| 673 if (abb != bb) | |
| 674 return; | |
| 675 for (unsigned opno = 1; opno < gimple_num_ops (stmt); ++opno) | |
| 676 { | |
| 677 tree op = gimple_op (stmt, opno); | |
| 678 if (independent_of_stmt_p (op, stmt, gsi, to_move_defs) != op) | |
| 679 return; | |
| 680 } | |
| 681 bitmap_set_bit (to_move_defs, | |
| 682 SSA_NAME_VERSION (gimple_assign_lhs (stmt))); | |
| 683 to_move_stmts.safe_push (stmt); | |
| 684 continue; | |
| 685 } | |
|
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686 |
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687 if (tmp_a) |
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688 { |
|
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689 tree type = TREE_TYPE (tmp_a); |
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690 if (a) |
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691 a = fold_build2 (PLUS_EXPR, type, fold_convert (type, a), tmp_a); |
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692 else |
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693 a = tmp_a; |
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694 } |
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695 if (tmp_m) |
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696 { |
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697 tree type = TREE_TYPE (tmp_m); |
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698 if (m) |
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699 m = fold_build2 (MULT_EXPR, type, fold_convert (type, m), tmp_m); |
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700 else |
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701 m = tmp_m; |
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702 |
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703 if (a) |
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704 a = fold_build2 (MULT_EXPR, type, fold_convert (type, a), tmp_m); |
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705 } |
| 0 | 706 } |
| 707 | |
| 708 /* See if this is a tail call we can handle. */ | |
| 111 | 709 ret_var = gimple_return_retval (as_a <greturn *> (stmt)); |
| 0 | 710 |
| 711 /* We may proceed if there either is no return value, or the return value | |
| 712 is identical to the call's return. */ | |
| 713 if (ret_var | |
| 714 && (ret_var != ass_var)) | |
| 715 return; | |
| 716 | |
| 717 /* If this is not a tail recursive call, we cannot handle addends or | |
| 718 multiplicands. */ | |
| 719 if (!tail_recursion && (m || a)) | |
| 720 return; | |
| 721 | |
| 111 | 722 /* For pointers only allow additions. */ |
| 723 if (m && POINTER_TYPE_P (TREE_TYPE (DECL_RESULT (current_function_decl)))) | |
| 724 return; | |
| 725 | |
| 726 /* Move queued defs. */ | |
| 727 if (tail_recursion) | |
| 728 { | |
| 729 unsigned i; | |
| 730 FOR_EACH_VEC_ELT (to_move_stmts, i, stmt) | |
| 731 { | |
| 732 gimple_stmt_iterator mgsi = gsi_for_stmt (stmt); | |
| 733 gsi_move_before (&mgsi, &gsi); | |
| 734 } | |
| 145 | 735 if (!tailr_arg_needs_copy) |
| 736 tailr_arg_needs_copy = BITMAP_ALLOC (NULL); | |
| 737 for (param = DECL_ARGUMENTS (current_function_decl), idx = 0; | |
| 738 param; | |
| 739 param = DECL_CHAIN (param), idx++) | |
| 740 { | |
| 741 tree ddef, arg = gimple_call_arg (call, idx); | |
| 742 if (is_gimple_reg (param) | |
| 743 && (ddef = ssa_default_def (cfun, param)) | |
| 744 && (arg != ddef)) | |
| 745 bitmap_set_bit (tailr_arg_needs_copy, idx); | |
| 746 } | |
| 111 | 747 } |
| 748 | |
| 0 | 749 nw = XNEW (struct tailcall); |
| 750 | |
| 751 nw->call_gsi = gsi; | |
| 752 | |
| 753 nw->tail_recursion = tail_recursion; | |
| 754 | |
| 755 nw->mult = m; | |
| 756 nw->add = a; | |
| 757 | |
| 758 nw->next = *ret; | |
| 759 *ret = nw; | |
| 760 } | |
| 761 | |
| 762 /* Helper to insert PHI_ARGH to the phi of VAR in the destination of edge E. */ | |
| 763 | |
| 764 static void | |
| 765 add_successor_phi_arg (edge e, tree var, tree phi_arg) | |
| 766 { | |
| 111 | 767 gphi_iterator gsi; |
| 0 | 768 |
| 769 for (gsi = gsi_start_phis (e->dest); !gsi_end_p (gsi); gsi_next (&gsi)) | |
| 111 | 770 if (PHI_RESULT (gsi.phi ()) == var) |
| 0 | 771 break; |
| 772 | |
| 773 gcc_assert (!gsi_end_p (gsi)); | |
| 111 | 774 add_phi_arg (gsi.phi (), phi_arg, e, UNKNOWN_LOCATION); |
| 0 | 775 } |
| 776 | |
| 777 /* Creates a GIMPLE statement which computes the operation specified by | |
| 111 | 778 CODE, ACC and OP1 to a new variable with name LABEL and inserts the |
| 779 statement in the position specified by GSI. Returns the | |
| 0 | 780 tree node of the statement's result. */ |
| 781 | |
| 782 static tree | |
|
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783 adjust_return_value_with_ops (enum tree_code code, const char *label, |
|
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784 tree acc, tree op1, gimple_stmt_iterator gsi) |
| 0 | 785 { |
| 786 | |
| 787 tree ret_type = TREE_TYPE (DECL_RESULT (current_function_decl)); | |
| 111 | 788 tree result = make_temp_ssa_name (ret_type, NULL, label); |
| 789 gassign *stmt; | |
| 0 | 790 |
| 111 | 791 if (POINTER_TYPE_P (ret_type)) |
| 792 { | |
| 793 gcc_assert (code == PLUS_EXPR && TREE_TYPE (acc) == sizetype); | |
| 794 code = POINTER_PLUS_EXPR; | |
| 795 } | |
| 796 if (types_compatible_p (TREE_TYPE (acc), TREE_TYPE (op1)) | |
| 797 && code != POINTER_PLUS_EXPR) | |
| 798 stmt = gimple_build_assign (result, code, acc, op1); | |
|
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799 else |
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800 { |
| 111 | 801 tree tem; |
| 802 if (code == POINTER_PLUS_EXPR) | |
| 803 tem = fold_build2 (code, TREE_TYPE (op1), op1, acc); | |
| 804 else | |
| 805 tem = fold_build2 (code, TREE_TYPE (op1), | |
| 806 fold_convert (TREE_TYPE (op1), acc), op1); | |
| 807 tree rhs = fold_convert (ret_type, tem); | |
|
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808 rhs = force_gimple_operand_gsi (&gsi, rhs, |
| 111 | 809 false, NULL, true, GSI_SAME_STMT); |
| 810 stmt = gimple_build_assign (result, rhs); | |
|
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811 } |
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812 |
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813 gsi_insert_before (&gsi, stmt, GSI_NEW_STMT); |
| 0 | 814 return result; |
| 815 } | |
| 816 | |
|
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817 /* Creates a new GIMPLE statement that adjusts the value of accumulator ACC by |
| 0 | 818 the computation specified by CODE and OP1 and insert the statement |
| 819 at the position specified by GSI as a new statement. Returns new SSA name | |
| 820 of updated accumulator. */ | |
| 821 | |
| 822 static tree | |
| 823 update_accumulator_with_ops (enum tree_code code, tree acc, tree op1, | |
| 824 gimple_stmt_iterator gsi) | |
| 825 { | |
| 111 | 826 gassign *stmt; |
| 827 tree var = copy_ssa_name (acc); | |
|
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828 if (types_compatible_p (TREE_TYPE (acc), TREE_TYPE (op1))) |
| 111 | 829 stmt = gimple_build_assign (var, code, acc, op1); |
|
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830 else |
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831 { |
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832 tree rhs = fold_convert (TREE_TYPE (acc), |
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833 fold_build2 (code, |
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834 TREE_TYPE (op1), |
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835 fold_convert (TREE_TYPE (op1), acc), |
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836 op1)); |
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837 rhs = force_gimple_operand_gsi (&gsi, rhs, |
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838 false, NULL, false, GSI_CONTINUE_LINKING); |
| 111 | 839 stmt = gimple_build_assign (var, rhs); |
|
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840 } |
| 0 | 841 gsi_insert_after (&gsi, stmt, GSI_NEW_STMT); |
| 842 return var; | |
| 843 } | |
| 844 | |
| 845 /* Adjust the accumulator values according to A and M after GSI, and update | |
| 846 the phi nodes on edge BACK. */ | |
| 847 | |
| 848 static void | |
| 849 adjust_accumulator_values (gimple_stmt_iterator gsi, tree m, tree a, edge back) | |
| 850 { | |
|
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851 tree var, a_acc_arg, m_acc_arg; |
| 0 | 852 |
|
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853 if (m) |
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854 m = force_gimple_operand_gsi (&gsi, m, true, NULL, true, GSI_SAME_STMT); |
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855 if (a) |
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856 a = force_gimple_operand_gsi (&gsi, a, true, NULL, true, GSI_SAME_STMT); |
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857 |
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858 a_acc_arg = a_acc; |
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859 m_acc_arg = m_acc; |
| 0 | 860 if (a) |
| 861 { | |
| 862 if (m_acc) | |
| 863 { | |
| 864 if (integer_onep (a)) | |
| 865 var = m_acc; | |
| 866 else | |
| 867 var = adjust_return_value_with_ops (MULT_EXPR, "acc_tmp", m_acc, | |
|
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868 a, gsi); |
| 0 | 869 } |
| 870 else | |
| 871 var = a; | |
| 872 | |
| 873 a_acc_arg = update_accumulator_with_ops (PLUS_EXPR, a_acc, var, gsi); | |
| 874 } | |
| 875 | |
| 876 if (m) | |
| 877 m_acc_arg = update_accumulator_with_ops (MULT_EXPR, m_acc, m, gsi); | |
| 878 | |
| 879 if (a_acc) | |
| 880 add_successor_phi_arg (back, a_acc, a_acc_arg); | |
| 881 | |
| 882 if (m_acc) | |
| 883 add_successor_phi_arg (back, m_acc, m_acc_arg); | |
| 884 } | |
| 885 | |
| 886 /* Adjust value of the return at the end of BB according to M and A | |
| 887 accumulators. */ | |
| 888 | |
| 889 static void | |
| 890 adjust_return_value (basic_block bb, tree m, tree a) | |
| 891 { | |
| 892 tree retval; | |
| 111 | 893 greturn *ret_stmt = as_a <greturn *> (gimple_seq_last_stmt (bb_seq (bb))); |
| 0 | 894 gimple_stmt_iterator gsi = gsi_last_bb (bb); |
| 895 | |
| 896 gcc_assert (gimple_code (ret_stmt) == GIMPLE_RETURN); | |
| 897 | |
| 898 retval = gimple_return_retval (ret_stmt); | |
| 899 if (!retval || retval == error_mark_node) | |
| 900 return; | |
| 901 | |
| 902 if (m) | |
| 903 retval = adjust_return_value_with_ops (MULT_EXPR, "mul_tmp", m_acc, retval, | |
|
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904 gsi); |
| 0 | 905 if (a) |
| 906 retval = adjust_return_value_with_ops (PLUS_EXPR, "acc_tmp", a_acc, retval, | |
|
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907 gsi); |
| 0 | 908 gimple_return_set_retval (ret_stmt, retval); |
| 909 update_stmt (ret_stmt); | |
| 910 } | |
| 911 | |
| 912 /* Subtract COUNT and FREQUENCY from the basic block and it's | |
| 913 outgoing edge. */ | |
| 914 static void | |
| 131 | 915 decrease_profile (basic_block bb, profile_count count) |
| 0 | 916 { |
| 111 | 917 bb->count = bb->count - count; |
| 0 | 918 if (!single_succ_p (bb)) |
| 919 { | |
| 920 gcc_assert (!EDGE_COUNT (bb->succs)); | |
| 921 return; | |
| 922 } | |
| 923 } | |
| 924 | |
| 925 /* Eliminates tail call described by T. TMP_VARS is a list of | |
| 926 temporary variables used to copy the function arguments. */ | |
| 927 | |
| 928 static void | |
| 929 eliminate_tail_call (struct tailcall *t) | |
| 930 { | |
| 931 tree param, rslt; | |
| 111 | 932 gimple *stmt, *call; |
| 0 | 933 tree arg; |
| 934 size_t idx; | |
| 935 basic_block bb, first; | |
| 936 edge e; | |
| 111 | 937 gphi *phi; |
| 938 gphi_iterator gpi; | |
| 0 | 939 gimple_stmt_iterator gsi; |
| 111 | 940 gimple *orig_stmt; |
| 0 | 941 |
| 942 stmt = orig_stmt = gsi_stmt (t->call_gsi); | |
| 943 bb = gsi_bb (t->call_gsi); | |
| 944 | |
| 945 if (dump_file && (dump_flags & TDF_DETAILS)) | |
| 946 { | |
| 947 fprintf (dump_file, "Eliminated tail recursion in bb %d : ", | |
| 948 bb->index); | |
| 949 print_gimple_stmt (dump_file, stmt, 0, TDF_SLIM); | |
| 950 fprintf (dump_file, "\n"); | |
| 951 } | |
| 952 | |
| 953 gcc_assert (is_gimple_call (stmt)); | |
| 954 | |
| 111 | 955 first = single_succ (ENTRY_BLOCK_PTR_FOR_FN (cfun)); |
| 0 | 956 |
| 957 /* Remove the code after call_gsi that will become unreachable. The | |
| 958 possibly unreachable code in other blocks is removed later in | |
| 959 cfg cleanup. */ | |
| 960 gsi = t->call_gsi; | |
| 111 | 961 gimple_stmt_iterator gsi2 = gsi_last_bb (gimple_bb (gsi_stmt (gsi))); |
| 962 while (gsi_stmt (gsi2) != gsi_stmt (gsi)) | |
| 0 | 963 { |
| 111 | 964 gimple *t = gsi_stmt (gsi2); |
| 0 | 965 /* Do not remove the return statement, so that redirect_edge_and_branch |
| 966 sees how the block ends. */ | |
| 111 | 967 if (gimple_code (t) != GIMPLE_RETURN) |
| 968 { | |
| 969 gimple_stmt_iterator gsi3 = gsi2; | |
| 970 gsi_prev (&gsi2); | |
| 971 gsi_remove (&gsi3, true); | |
| 972 release_defs (t); | |
| 973 } | |
| 974 else | |
| 975 gsi_prev (&gsi2); | |
| 0 | 976 } |
| 977 | |
| 978 /* Number of executions of function has reduced by the tailcall. */ | |
| 979 e = single_succ_edge (gsi_bb (t->call_gsi)); | |
| 131 | 980 |
| 981 profile_count count = e->count (); | |
| 982 | |
| 983 /* When profile is inconsistent and the recursion edge is more frequent | |
| 984 than number of executions of functions, scale it down, so we do not end | |
| 985 up with 0 executions of entry block. */ | |
| 986 if (count >= ENTRY_BLOCK_PTR_FOR_FN (cfun)->count) | |
| 987 count = ENTRY_BLOCK_PTR_FOR_FN (cfun)->count.apply_scale (7, 8); | |
| 988 decrease_profile (EXIT_BLOCK_PTR_FOR_FN (cfun), count); | |
| 989 decrease_profile (ENTRY_BLOCK_PTR_FOR_FN (cfun), count); | |
| 111 | 990 if (e->dest != EXIT_BLOCK_PTR_FOR_FN (cfun)) |
| 131 | 991 decrease_profile (e->dest, count); |
| 0 | 992 |
| 993 /* Replace the call by a jump to the start of function. */ | |
| 994 e = redirect_edge_and_branch (single_succ_edge (gsi_bb (t->call_gsi)), | |
| 995 first); | |
| 996 gcc_assert (e); | |
| 997 PENDING_STMT (e) = NULL; | |
| 998 | |
| 999 /* Add phi node entries for arguments. The ordering of the phi nodes should | |
| 1000 be the same as the ordering of the arguments. */ | |
| 1001 for (param = DECL_ARGUMENTS (current_function_decl), | |
| 111 | 1002 idx = 0, gpi = gsi_start_phis (first); |
| 0 | 1003 param; |
|
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1004 param = DECL_CHAIN (param), idx++) |
| 0 | 1005 { |
| 145 | 1006 if (!bitmap_bit_p (tailr_arg_needs_copy, idx)) |
| 0 | 1007 continue; |
| 1008 | |
| 1009 arg = gimple_call_arg (stmt, idx); | |
| 111 | 1010 phi = gpi.phi (); |
| 0 | 1011 gcc_assert (param == SSA_NAME_VAR (PHI_RESULT (phi))); |
| 1012 | |
|
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1013 add_phi_arg (phi, arg, e, gimple_location (stmt)); |
| 111 | 1014 gsi_next (&gpi); |
| 0 | 1015 } |
| 1016 | |
| 1017 /* Update the values of accumulators. */ | |
| 1018 adjust_accumulator_values (t->call_gsi, t->mult, t->add, e); | |
| 1019 | |
| 1020 call = gsi_stmt (t->call_gsi); | |
| 1021 rslt = gimple_call_lhs (call); | |
| 111 | 1022 if (rslt != NULL_TREE && TREE_CODE (rslt) == SSA_NAME) |
| 0 | 1023 { |
| 1024 /* Result of the call will no longer be defined. So adjust the | |
| 1025 SSA_NAME_DEF_STMT accordingly. */ | |
| 1026 SSA_NAME_DEF_STMT (rslt) = gimple_build_nop (); | |
| 1027 } | |
| 1028 | |
| 1029 gsi_remove (&t->call_gsi, true); | |
| 1030 release_defs (call); | |
| 1031 } | |
| 1032 | |
| 1033 /* Optimizes the tailcall described by T. If OPT_TAILCALLS is true, also | |
| 1034 mark the tailcalls for the sibcall optimization. */ | |
| 1035 | |
| 1036 static bool | |
| 1037 optimize_tail_call (struct tailcall *t, bool opt_tailcalls) | |
| 1038 { | |
| 1039 if (t->tail_recursion) | |
| 1040 { | |
| 1041 eliminate_tail_call (t); | |
| 1042 return true; | |
| 1043 } | |
| 1044 | |
| 1045 if (opt_tailcalls) | |
| 1046 { | |
| 111 | 1047 gcall *stmt = as_a <gcall *> (gsi_stmt (t->call_gsi)); |
| 0 | 1048 |
| 1049 gimple_call_set_tail (stmt, true); | |
| 111 | 1050 cfun->tail_call_marked = true; |
| 0 | 1051 if (dump_file && (dump_flags & TDF_DETAILS)) |
| 1052 { | |
| 1053 fprintf (dump_file, "Found tail call "); | |
| 1054 print_gimple_stmt (dump_file, stmt, 0, dump_flags); | |
| 1055 fprintf (dump_file, " in bb %i\n", (gsi_bb (t->call_gsi))->index); | |
| 1056 } | |
| 1057 } | |
| 1058 | |
| 1059 return false; | |
| 1060 } | |
| 1061 | |
| 1062 /* Creates a tail-call accumulator of the same type as the return type of the | |
| 1063 current function. LABEL is the name used to creating the temporary | |
| 1064 variable for the accumulator. The accumulator will be inserted in the | |
| 1065 phis of a basic block BB with single predecessor with an initial value | |
| 1066 INIT converted to the current function return type. */ | |
| 1067 | |
| 1068 static tree | |
| 1069 create_tailcall_accumulator (const char *label, basic_block bb, tree init) | |
| 1070 { | |
| 1071 tree ret_type = TREE_TYPE (DECL_RESULT (current_function_decl)); | |
| 111 | 1072 if (POINTER_TYPE_P (ret_type)) |
| 1073 ret_type = sizetype; | |
| 0 | 1074 |
| 111 | 1075 tree tmp = make_temp_ssa_name (ret_type, NULL, label); |
| 1076 gphi *phi; | |
| 1077 | |
| 0 | 1078 phi = create_phi_node (tmp, bb); |
| 1079 /* RET_TYPE can be a float when -ffast-maths is enabled. */ | |
|
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1080 add_phi_arg (phi, fold_convert (ret_type, init), single_pred_edge (bb), |
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1081 UNKNOWN_LOCATION); |
| 0 | 1082 return PHI_RESULT (phi); |
| 1083 } | |
|
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1084 |
| 0 | 1085 /* Optimizes tail calls in the function, turning the tail recursion |
| 1086 into iteration. */ | |
| 1087 | |
| 1088 static unsigned int | |
| 1089 tree_optimize_tail_calls_1 (bool opt_tailcalls) | |
| 1090 { | |
| 1091 edge e; | |
| 1092 bool phis_constructed = false; | |
| 1093 struct tailcall *tailcalls = NULL, *act, *next; | |
| 1094 bool changed = false; | |
| 111 | 1095 basic_block first = single_succ (ENTRY_BLOCK_PTR_FOR_FN (cfun)); |
| 0 | 1096 tree param; |
| 111 | 1097 gimple *stmt; |
| 0 | 1098 edge_iterator ei; |
| 1099 | |
| 1100 if (!suitable_for_tail_opt_p ()) | |
| 1101 return 0; | |
| 1102 if (opt_tailcalls) | |
| 1103 opt_tailcalls = suitable_for_tail_call_opt_p (); | |
| 1104 | |
| 111 | 1105 FOR_EACH_EDGE (e, ei, EXIT_BLOCK_PTR_FOR_FN (cfun)->preds) |
| 0 | 1106 { |
| 1107 /* Only traverse the normal exits, i.e. those that end with return | |
| 1108 statement. */ | |
| 1109 stmt = last_stmt (e->src); | |
| 1110 | |
| 1111 if (stmt | |
| 1112 && gimple_code (stmt) == GIMPLE_RETURN) | |
| 1113 find_tail_calls (e->src, &tailcalls); | |
| 1114 } | |
| 1115 | |
| 145 | 1116 if (live_vars) |
| 1117 { | |
| 1118 destroy_live_vars (live_vars_vec); | |
| 1119 delete live_vars; | |
| 1120 live_vars = NULL; | |
| 1121 } | |
| 1122 | |
| 0 | 1123 /* Construct the phi nodes and accumulators if necessary. */ |
| 1124 a_acc = m_acc = NULL_TREE; | |
| 1125 for (act = tailcalls; act; act = act->next) | |
| 1126 { | |
| 1127 if (!act->tail_recursion) | |
| 1128 continue; | |
| 1129 | |
| 1130 if (!phis_constructed) | |
| 1131 { | |
|
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parents:
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|
1132 /* Ensure that there is only one predecessor of the block |
|
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update it from 4.4.2 to 4.4.3.
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parents:
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|
1133 or if there are existing degenerate PHI nodes. */ |
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parents:
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|
1134 if (!single_pred_p (first) |
|
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update it from 4.4.2 to 4.4.3.
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parents:
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changeset
|
1135 || !gimple_seq_empty_p (phi_nodes (first))) |
| 111 | 1136 first = |
| 1137 split_edge (single_succ_edge (ENTRY_BLOCK_PTR_FOR_FN (cfun))); | |
| 0 | 1138 |
| 1139 /* Copy the args if needed. */ | |
| 145 | 1140 unsigned idx; |
| 1141 for (param = DECL_ARGUMENTS (current_function_decl), idx = 0; | |
| 0 | 1142 param; |
| 145 | 1143 param = DECL_CHAIN (param), idx++) |
| 1144 if (bitmap_bit_p (tailr_arg_needs_copy, idx)) | |
| 0 | 1145 { |
| 111 | 1146 tree name = ssa_default_def (cfun, param); |
| 0 | 1147 tree new_name = make_ssa_name (param, SSA_NAME_DEF_STMT (name)); |
| 111 | 1148 gphi *phi; |
| 0 | 1149 |
| 111 | 1150 set_ssa_default_def (cfun, param, new_name); |
| 0 | 1151 phi = create_phi_node (name, first); |
|
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ryoma <e075725@ie.u-ryukyu.ac.jp>
parents:
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changeset
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1152 add_phi_arg (phi, new_name, single_pred_edge (first), |
|
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update it from 4.4.3 to 4.5.0
ryoma <e075725@ie.u-ryukyu.ac.jp>
parents:
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diff
changeset
|
1153 EXPR_LOCATION (param)); |
| 0 | 1154 } |
| 1155 phis_constructed = true; | |
| 1156 } | |
| 1157 | |
| 1158 if (act->add && !a_acc) | |
| 1159 a_acc = create_tailcall_accumulator ("add_acc", first, | |
| 1160 integer_zero_node); | |
| 1161 | |
| 1162 if (act->mult && !m_acc) | |
| 1163 m_acc = create_tailcall_accumulator ("mult_acc", first, | |
| 1164 integer_one_node); | |
| 1165 } | |
| 1166 | |
| 111 | 1167 if (a_acc || m_acc) |
| 1168 { | |
| 1169 /* When the tail call elimination using accumulators is performed, | |
| 1170 statements adding the accumulated value are inserted at all exits. | |
| 1171 This turns all other tail calls to non-tail ones. */ | |
| 1172 opt_tailcalls = false; | |
| 1173 } | |
| 1174 | |
| 0 | 1175 for (; tailcalls; tailcalls = next) |
| 1176 { | |
| 1177 next = tailcalls->next; | |
| 1178 changed |= optimize_tail_call (tailcalls, opt_tailcalls); | |
| 1179 free (tailcalls); | |
| 1180 } | |
| 1181 | |
| 1182 if (a_acc || m_acc) | |
| 1183 { | |
| 1184 /* Modify the remaining return statements. */ | |
| 111 | 1185 FOR_EACH_EDGE (e, ei, EXIT_BLOCK_PTR_FOR_FN (cfun)->preds) |
| 0 | 1186 { |
| 1187 stmt = last_stmt (e->src); | |
| 1188 | |
| 1189 if (stmt | |
| 1190 && gimple_code (stmt) == GIMPLE_RETURN) | |
| 1191 adjust_return_value (e->src, m_acc, a_acc); | |
| 1192 } | |
| 1193 } | |
| 1194 | |
| 1195 if (changed) | |
| 111 | 1196 { |
| 1197 /* We may have created new loops. Make them magically appear. */ | |
| 1198 loops_state_set (LOOPS_NEED_FIXUP); | |
| 1199 free_dominance_info (CDI_DOMINATORS); | |
| 1200 } | |
| 0 | 1201 |
| 111 | 1202 /* Add phi nodes for the virtual operands defined in the function to the |
| 1203 header of the loop created by tail recursion elimination. Do so | |
| 1204 by triggering the SSA renamer. */ | |
| 0 | 1205 if (phis_constructed) |
| 111 | 1206 mark_virtual_operands_for_renaming (cfun); |
| 1207 | |
| 145 | 1208 if (tailr_arg_needs_copy) |
| 1209 BITMAP_FREE (tailr_arg_needs_copy); | |
| 1210 | |
| 0 | 1211 if (changed) |
| 1212 return TODO_cleanup_cfg | TODO_update_ssa_only_virtuals; | |
| 1213 return 0; | |
| 1214 } | |
| 1215 | |
| 1216 static bool | |
| 1217 gate_tail_calls (void) | |
| 1218 { | |
| 1219 return flag_optimize_sibling_calls != 0 && dbg_cnt (tail_call); | |
| 1220 } | |
| 1221 | |
| 1222 static unsigned int | |
| 1223 execute_tail_calls (void) | |
| 1224 { | |
| 1225 return tree_optimize_tail_calls_1 (true); | |
| 1226 } | |
| 1227 | |
| 111 | 1228 namespace { |
| 1229 | |
| 1230 const pass_data pass_data_tail_recursion = | |
| 0 | 1231 { |
| 111 | 1232 GIMPLE_PASS, /* type */ |
| 1233 "tailr", /* name */ | |
| 1234 OPTGROUP_NONE, /* optinfo_flags */ | |
| 1235 TV_NONE, /* tv_id */ | |
| 1236 ( PROP_cfg | PROP_ssa ), /* properties_required */ | |
| 1237 0, /* properties_provided */ | |
| 1238 0, /* properties_destroyed */ | |
| 1239 0, /* todo_flags_start */ | |
| 1240 0, /* todo_flags_finish */ | |
| 0 | 1241 }; |
| 1242 | |
| 111 | 1243 class pass_tail_recursion : public gimple_opt_pass |
| 1244 { | |
| 1245 public: | |
| 1246 pass_tail_recursion (gcc::context *ctxt) | |
| 1247 : gimple_opt_pass (pass_data_tail_recursion, ctxt) | |
| 1248 {} | |
| 1249 | |
| 1250 /* opt_pass methods: */ | |
| 1251 opt_pass * clone () { return new pass_tail_recursion (m_ctxt); } | |
| 1252 virtual bool gate (function *) { return gate_tail_calls (); } | |
| 1253 virtual unsigned int execute (function *) | |
| 1254 { | |
| 1255 return tree_optimize_tail_calls_1 (false); | |
| 1256 } | |
| 1257 | |
| 1258 }; // class pass_tail_recursion | |
| 1259 | |
| 1260 } // anon namespace | |
| 1261 | |
| 1262 gimple_opt_pass * | |
| 1263 make_pass_tail_recursion (gcc::context *ctxt) | |
| 1264 { | |
| 1265 return new pass_tail_recursion (ctxt); | |
| 1266 } | |
| 1267 | |
| 1268 namespace { | |
| 1269 | |
| 1270 const pass_data pass_data_tail_calls = | |
| 0 | 1271 { |
| 111 | 1272 GIMPLE_PASS, /* type */ |
| 1273 "tailc", /* name */ | |
| 1274 OPTGROUP_NONE, /* optinfo_flags */ | |
| 1275 TV_NONE, /* tv_id */ | |
| 1276 ( PROP_cfg | PROP_ssa ), /* properties_required */ | |
| 1277 0, /* properties_provided */ | |
| 1278 0, /* properties_destroyed */ | |
| 1279 0, /* todo_flags_start */ | |
| 1280 0, /* todo_flags_finish */ | |
| 0 | 1281 }; |
| 111 | 1282 |
| 1283 class pass_tail_calls : public gimple_opt_pass | |
| 1284 { | |
| 1285 public: | |
| 1286 pass_tail_calls (gcc::context *ctxt) | |
| 1287 : gimple_opt_pass (pass_data_tail_calls, ctxt) | |
| 1288 {} | |
| 1289 | |
| 1290 /* opt_pass methods: */ | |
| 1291 virtual bool gate (function *) { return gate_tail_calls (); } | |
| 1292 virtual unsigned int execute (function *) { return execute_tail_calls (); } | |
| 1293 | |
| 1294 }; // class pass_tail_calls | |
| 1295 | |
| 1296 } // anon namespace | |
| 1297 | |
| 1298 gimple_opt_pass * | |
| 1299 make_pass_tail_calls (gcc::context *ctxt) | |
| 1300 { | |
| 1301 return new pass_tail_calls (ctxt); | |
| 1302 } |