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4ee9c684 | 1 | /* Generic routines for manipulating PHIs |
f1717362 | 2 | Copyright (C) 2003-2016 Free Software Foundation, Inc. |
de5f9bd2 | 3 | |
4ee9c684 | 4 | This file is part of GCC. |
de5f9bd2 | 5 | |
4ee9c684 | 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 | |
8c4c00c1 | 8 | the Free Software Foundation; either version 3, or (at your option) |
4ee9c684 | 9 | any later version. |
de5f9bd2 | 10 | |
4ee9c684 | 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. | |
de5f9bd2 | 15 | |
4ee9c684 | 16 | You should have received a copy of the GNU General Public License |
8c4c00c1 | 17 | along with GCC; see the file COPYING3. If not see |
18 | <http://www.gnu.org/licenses/>. */ | |
de5f9bd2 | 19 | |
4ee9c684 | 20 | #include "config.h" |
21 | #include "system.h" | |
22 | #include "coretypes.h" | |
9ef16211 | 23 | #include "backend.h" |
b20a8bb4 | 24 | #include "tree.h" |
9ef16211 | 25 | #include "gimple.h" |
9ef16211 | 26 | #include "ssa.h" |
9ef16211 | 27 | #include "fold-const.h" |
dcf1a1ec | 28 | #include "gimple-iterator.h" |
69ee5dbb | 29 | #include "tree-ssa.h" |
4ee9c684 | 30 | |
31 | /* Rewriting a function into SSA form can create a huge number of PHIs | |
32 | many of which may be thrown away shortly after their creation if jumps | |
de5f9bd2 | 33 | were threaded through PHI nodes. |
4ee9c684 | 34 | |
35 | While our garbage collection mechanisms will handle this situation, it | |
36 | is extremely wasteful to create nodes and throw them away, especially | |
37 | when the nodes can be reused. | |
38 | ||
39 | For PR 8361, we can significantly reduce the number of nodes allocated | |
40 | and thus the total amount of memory allocated by managing PHIs a | |
41 | little. This additionally helps reduce the amount of work done by the | |
42 | garbage collector. Similar results have been seen on a wider variety | |
43 | of tests (such as the compiler itself). | |
44 | ||
4ee9c684 | 45 | PHI nodes have different sizes, so we can't have a single list of all |
46 | the PHI nodes as it would be too expensive to walk down that list to | |
47 | find a PHI of a suitable size. | |
48 | ||
49 | Instead we have an array of lists of free PHI nodes. The array is | |
50 | indexed by the number of PHI alternatives that PHI node can hold. | |
51 | Except for the last array member, which holds all remaining PHI | |
52 | nodes. | |
53 | ||
54 | So to find a free PHI node, we compute its index into the free PHI | |
55 | node array and see if there are any elements with an exact match. | |
56 | If so, then we are done. Otherwise, we test the next larger size | |
57 | up and continue until we are in the last array element. | |
58 | ||
59 | We do not actually walk members of the last array element. While it | |
60 | might allow us to pick up a few reusable PHI nodes, it could potentially | |
61 | be very expensive if the program has released a bunch of large PHI nodes, | |
62 | but keeps asking for even larger PHI nodes. Experiments have shown that | |
63 | walking the elements of the last array entry would result in finding less | |
de5f9bd2 | 64 | than .1% additional reusable PHI nodes. |
4ee9c684 | 65 | |
66 | Note that we can never have less than two PHI argument slots. Thus, | |
67 | the -2 on all the calculations below. */ | |
68 | ||
69 | #define NUM_BUCKETS 10 | |
42acab1c | 70 | static GTY ((deletable (""))) vec<gimple *, va_gc> *free_phinodes[NUM_BUCKETS - 2]; |
4ee9c684 | 71 | static unsigned long free_phinode_count; |
72 | ||
73 | static int ideal_phi_node_len (int); | |
4ee9c684 | 74 | |
4ee9c684 | 75 | unsigned int phi_nodes_reused; |
76 | unsigned int phi_nodes_created; | |
4ee9c684 | 77 | |
4ee9c684 | 78 | /* Dump some simple statistics regarding the re-use of PHI nodes. */ |
79 | ||
4ee9c684 | 80 | void |
81 | phinodes_print_statistics (void) | |
82 | { | |
83 | fprintf (stderr, "PHI nodes allocated: %u\n", phi_nodes_created); | |
84 | fprintf (stderr, "PHI nodes reused: %u\n", phi_nodes_reused); | |
85 | } | |
4ee9c684 | 86 | |
c1ba1d09 | 87 | /* Allocate a PHI node with at least LEN arguments. If the free list |
88 | happens to contain a PHI node with LEN arguments or more, return | |
89 | that one. */ | |
90 | ||
1a91d914 | 91 | static inline gphi * |
75a70cf9 | 92 | allocate_phi_node (size_t len) |
c1ba1d09 | 93 | { |
1a91d914 | 94 | gphi *phi; |
75a70cf9 | 95 | size_t bucket = NUM_BUCKETS - 2; |
1a91d914 | 96 | size_t size = sizeof (struct gphi) |
75a70cf9 | 97 | + (len - 1) * sizeof (struct phi_arg_d); |
c1ba1d09 | 98 | |
99 | if (free_phinode_count) | |
100 | for (bucket = len - 2; bucket < NUM_BUCKETS - 2; bucket++) | |
101 | if (free_phinodes[bucket]) | |
102 | break; | |
103 | ||
104 | /* If our free list has an element, then use it. */ | |
105 | if (bucket < NUM_BUCKETS - 2 | |
f1f41a6c | 106 | && gimple_phi_capacity ((*free_phinodes[bucket])[0]) >= len) |
c1ba1d09 | 107 | { |
108 | free_phinode_count--; | |
1a91d914 | 109 | phi = as_a <gphi *> (free_phinodes[bucket]->pop ()); |
f1f41a6c | 110 | if (free_phinodes[bucket]->is_empty ()) |
111 | vec_free (free_phinodes[bucket]); | |
ecd52ea9 | 112 | if (GATHER_STATISTICS) |
113 | phi_nodes_reused++; | |
c1ba1d09 | 114 | } |
115 | else | |
116 | { | |
1a91d914 | 117 | phi = static_cast <gphi *> (ggc_internal_alloc (size)); |
ecd52ea9 | 118 | if (GATHER_STATISTICS) |
75a70cf9 | 119 | { |
120 | enum gimple_alloc_kind kind = gimple_alloc_kind (GIMPLE_PHI); | |
ecd52ea9 | 121 | phi_nodes_created++; |
122 | gimple_alloc_counts[(int) kind]++; | |
123 | gimple_alloc_sizes[(int) kind] += size; | |
75a70cf9 | 124 | } |
c1ba1d09 | 125 | } |
126 | ||
127 | return phi; | |
128 | } | |
129 | ||
4ee9c684 | 130 | /* Given LEN, the original number of requested PHI arguments, return |
131 | a new, "ideal" length for the PHI node. The "ideal" length rounds | |
132 | the total size of the PHI node up to the next power of two bytes. | |
133 | ||
134 | Rounding up will not result in wasting any memory since the size request | |
135 | will be rounded up by the GC system anyway. [ Note this is not entirely | |
136 | true since the original length might have fit on one of the special | |
137 | GC pages. ] By rounding up, we may avoid the need to reallocate the | |
138 | PHI node later if we increase the number of arguments for the PHI. */ | |
139 | ||
140 | static int | |
141 | ideal_phi_node_len (int len) | |
142 | { | |
143 | size_t size, new_size; | |
144 | int log2, new_len; | |
145 | ||
146 | /* We do not support allocations of less than two PHI argument slots. */ | |
147 | if (len < 2) | |
148 | len = 2; | |
149 | ||
150 | /* Compute the number of bytes of the original request. */ | |
1a91d914 | 151 | size = sizeof (struct gphi) |
75a70cf9 | 152 | + (len - 1) * sizeof (struct phi_arg_d); |
4ee9c684 | 153 | |
154 | /* Round it up to the next power of two. */ | |
155 | log2 = ceil_log2 (size); | |
156 | new_size = 1 << log2; | |
de5f9bd2 | 157 | |
158 | /* Now compute and return the number of PHI argument slots given an | |
4ee9c684 | 159 | ideal size allocation. */ |
160 | new_len = len + (new_size - size) / sizeof (struct phi_arg_d); | |
161 | return new_len; | |
162 | } | |
163 | ||
88dbf20f | 164 | /* Return a PHI node with LEN argument slots for variable VAR. */ |
4ee9c684 | 165 | |
1a91d914 | 166 | static gphi * |
4ee9c684 | 167 | make_phi_node (tree var, int len) |
168 | { | |
1a91d914 | 169 | gphi *phi; |
22aa74c4 | 170 | int capacity, i; |
4ee9c684 | 171 | |
08d1df96 | 172 | capacity = ideal_phi_node_len (len); |
4ee9c684 | 173 | |
08d1df96 | 174 | phi = allocate_phi_node (capacity); |
4ee9c684 | 175 | |
cc890649 | 176 | /* We need to clear the entire PHI node, including the argument |
177 | portion, because we represent a "missing PHI argument" by placing | |
178 | NULL_TREE in PHI_ARG_DEF. */ | |
1a91d914 | 179 | memset (phi, 0, (sizeof (struct gphi) |
75a70cf9 | 180 | - sizeof (struct phi_arg_d) |
cc890649 | 181 | + sizeof (struct phi_arg_d) * len)); |
de6bd75e | 182 | phi->code = GIMPLE_PHI; |
e3a19533 | 183 | gimple_init_singleton (phi); |
de6bd75e | 184 | phi->nargs = len; |
185 | phi->capacity = capacity; | |
9c06f260 | 186 | if (!var) |
187 | ; | |
188 | else if (TREE_CODE (var) == SSA_NAME) | |
75a70cf9 | 189 | gimple_phi_set_result (phi, var); |
4ee9c684 | 190 | else |
75a70cf9 | 191 | gimple_phi_set_result (phi, make_ssa_name (var, phi)); |
4ee9c684 | 192 | |
22aa74c4 | 193 | for (i = 0; i < capacity; i++) |
194 | { | |
b66731e8 | 195 | use_operand_p imm; |
efbcb6de | 196 | |
197 | gimple_phi_arg_set_location (phi, i, UNKNOWN_LOCATION); | |
75a70cf9 | 198 | imm = gimple_phi_arg_imm_use_ptr (phi, i); |
199 | imm->use = gimple_phi_arg_def_ptr (phi, i); | |
22aa74c4 | 200 | imm->prev = NULL; |
201 | imm->next = NULL; | |
75a70cf9 | 202 | imm->loc.stmt = phi; |
22aa74c4 | 203 | } |
17889f9d | 204 | |
4ee9c684 | 205 | return phi; |
206 | } | |
207 | ||
208 | /* We no longer need PHI, release it so that it may be reused. */ | |
209 | ||
210 | void | |
42acab1c | 211 | release_phi_node (gimple *phi) |
4ee9c684 | 212 | { |
75a70cf9 | 213 | size_t bucket; |
214 | size_t len = gimple_phi_capacity (phi); | |
215 | size_t x; | |
22aa74c4 | 216 | |
75a70cf9 | 217 | for (x = 0; x < gimple_phi_num_args (phi); x++) |
22aa74c4 | 218 | { |
b66731e8 | 219 | use_operand_p imm; |
75a70cf9 | 220 | imm = gimple_phi_arg_imm_use_ptr (phi, x); |
22aa74c4 | 221 | delink_imm_use (imm); |
222 | } | |
4ee9c684 | 223 | |
224 | bucket = len > NUM_BUCKETS - 1 ? NUM_BUCKETS - 1 : len; | |
225 | bucket -= 2; | |
f1f41a6c | 226 | vec_safe_push (free_phinodes[bucket], phi); |
4ee9c684 | 227 | free_phinode_count++; |
228 | } | |
229 | ||
75a70cf9 | 230 | |
4ee9c684 | 231 | /* Resize an existing PHI node. The only way is up. Return the |
232 | possibly relocated phi. */ | |
de5f9bd2 | 233 | |
1a91d914 | 234 | static gphi * |
235 | resize_phi_node (gphi *phi, size_t len) | |
4ee9c684 | 236 | { |
75a70cf9 | 237 | size_t old_size, i; |
1a91d914 | 238 | gphi *new_phi; |
8c0963c4 | 239 | |
e3a19533 | 240 | gcc_assert (len > gimple_phi_capacity (phi)); |
8c0963c4 | 241 | |
ee98f167 | 242 | /* The garbage collector will not look at the PHI node beyond the |
243 | first PHI_NUM_ARGS elements. Therefore, all we have to copy is a | |
244 | portion of the PHI node currently in use. */ | |
1a91d914 | 245 | old_size = sizeof (struct gphi) |
e3a19533 | 246 | + (gimple_phi_num_args (phi) - 1) * sizeof (struct phi_arg_d); |
4ee9c684 | 247 | |
c1ba1d09 | 248 | new_phi = allocate_phi_node (len); |
4ee9c684 | 249 | |
e3a19533 | 250 | memcpy (new_phi, phi, old_size); |
4ee9c684 | 251 | |
75a70cf9 | 252 | for (i = 0; i < gimple_phi_num_args (new_phi); i++) |
22aa74c4 | 253 | { |
b66731e8 | 254 | use_operand_p imm, old_imm; |
75a70cf9 | 255 | imm = gimple_phi_arg_imm_use_ptr (new_phi, i); |
e3a19533 | 256 | old_imm = gimple_phi_arg_imm_use_ptr (phi, i); |
75a70cf9 | 257 | imm->use = gimple_phi_arg_def_ptr (new_phi, i); |
22aa74c4 | 258 | relink_imm_use_stmt (imm, old_imm, new_phi); |
259 | } | |
260 | ||
de6bd75e | 261 | new_phi->capacity = len; |
de5f9bd2 | 262 | |
75a70cf9 | 263 | for (i = gimple_phi_num_args (new_phi); i < len; i++) |
22aa74c4 | 264 | { |
b66731e8 | 265 | use_operand_p imm; |
efbcb6de | 266 | |
267 | gimple_phi_arg_set_location (new_phi, i, UNKNOWN_LOCATION); | |
75a70cf9 | 268 | imm = gimple_phi_arg_imm_use_ptr (new_phi, i); |
269 | imm->use = gimple_phi_arg_def_ptr (new_phi, i); | |
22aa74c4 | 270 | imm->prev = NULL; |
271 | imm->next = NULL; | |
75a70cf9 | 272 | imm->loc.stmt = new_phi; |
22aa74c4 | 273 | } |
274 | ||
e3a19533 | 275 | return new_phi; |
4ee9c684 | 276 | } |
277 | ||
a77b4cde | 278 | /* Reserve PHI arguments for a new edge to basic block BB. */ |
279 | ||
280 | void | |
281 | reserve_phi_args_for_new_edge (basic_block bb) | |
282 | { | |
75a70cf9 | 283 | size_t len = EDGE_COUNT (bb->preds); |
284 | size_t cap = ideal_phi_node_len (len + 4); | |
1a91d914 | 285 | gphi_iterator gsi; |
a77b4cde | 286 | |
75a70cf9 | 287 | for (gsi = gsi_start_phis (bb); !gsi_end_p (gsi); gsi_next (&gsi)) |
a77b4cde | 288 | { |
1a91d914 | 289 | gphi *stmt = gsi.phi (); |
75a70cf9 | 290 | |
e3a19533 | 291 | if (len > gimple_phi_capacity (stmt)) |
a77b4cde | 292 | { |
1a91d914 | 293 | gphi *new_phi = resize_phi_node (stmt, cap); |
a77b4cde | 294 | |
75a70cf9 | 295 | /* The result of the PHI is defined by this PHI node. */ |
e3a19533 | 296 | SSA_NAME_DEF_STMT (gimple_phi_result (new_phi)) = new_phi; |
297 | gsi_set_stmt (&gsi, new_phi); | |
a77b4cde | 298 | |
e3a19533 | 299 | release_phi_node (stmt); |
300 | stmt = new_phi; | |
a77b4cde | 301 | } |
cc890649 | 302 | |
303 | /* We represent a "missing PHI argument" by placing NULL_TREE in | |
304 | the corresponding slot. If PHI arguments were added | |
305 | immediately after an edge is created, this zeroing would not | |
306 | be necessary, but unfortunately this is not the case. For | |
307 | example, the loop optimizer duplicates several basic blocks, | |
308 | redirects edges, and then fixes up PHI arguments later in | |
309 | batch. */ | |
e3a19533 | 310 | SET_PHI_ARG_DEF (stmt, len - 1, NULL_TREE); |
16f02f09 | 311 | gimple_phi_arg_set_location (stmt, len - 1, UNKNOWN_LOCATION); |
cc890649 | 312 | |
de6bd75e | 313 | stmt->nargs++; |
a77b4cde | 314 | } |
315 | } | |
316 | ||
255b6be7 | 317 | /* Adds PHI to BB. */ |
17889f9d | 318 | |
48e1416a | 319 | void |
1a91d914 | 320 | add_phi_node_to_bb (gphi *phi, basic_block bb) |
4ee9c684 | 321 | { |
e3a19533 | 322 | gimple_seq seq = phi_nodes (bb); |
4ee9c684 | 323 | /* Add the new PHI node to the list of PHI nodes for block BB. */ |
e3a19533 | 324 | if (seq == NULL) |
325 | set_phi_nodes (bb, gimple_seq_alloc_with_stmt (phi)); | |
326 | else | |
327 | { | |
328 | gimple_seq_add_stmt (&seq, phi); | |
329 | gcc_assert (seq == phi_nodes (bb)); | |
330 | } | |
4ee9c684 | 331 | |
332 | /* Associate BB to the PHI node. */ | |
75a70cf9 | 333 | gimple_set_bb (phi, bb); |
4ee9c684 | 334 | |
255b6be7 | 335 | } |
336 | ||
337 | /* Create a new PHI node for variable VAR at basic block BB. */ | |
338 | ||
1a91d914 | 339 | gphi * |
255b6be7 | 340 | create_phi_node (tree var, basic_block bb) |
341 | { | |
1a91d914 | 342 | gphi *phi = make_phi_node (var, EDGE_COUNT (bb->preds)); |
255b6be7 | 343 | |
344 | add_phi_node_to_bb (phi, bb); | |
4ee9c684 | 345 | return phi; |
346 | } | |
347 | ||
17889f9d | 348 | |
4ee9c684 | 349 | /* Add a new argument to PHI node PHI. DEF is the incoming reaching |
350 | definition and E is the edge through which DEF reaches PHI. The new | |
351 | argument is added at the end of the argument list. | |
352 | If PHI has reached its maximum capacity, add a few slots. In this case, | |
353 | PHI points to the reallocated phi node when we return. */ | |
354 | ||
355 | void | |
1a91d914 | 356 | add_phi_arg (gphi *phi, tree def, edge e, source_location locus) |
4ee9c684 | 357 | { |
2a6e956a | 358 | basic_block bb = e->dest; |
4ee9c684 | 359 | |
75a70cf9 | 360 | gcc_assert (bb == gimple_bb (phi)); |
2a6e956a | 361 | |
a77b4cde | 362 | /* We resize PHI nodes upon edge creation. We should always have |
363 | enough room at this point. */ | |
75a70cf9 | 364 | gcc_assert (gimple_phi_num_args (phi) <= gimple_phi_capacity (phi)); |
cc890649 | 365 | |
366 | /* We resize PHI nodes upon edge creation. We should always have | |
367 | enough room at this point. */ | |
75a70cf9 | 368 | gcc_assert (e->dest_idx < gimple_phi_num_args (phi)); |
4ee9c684 | 369 | |
370 | /* Copy propagation needs to know what object occur in abnormal | |
371 | PHI nodes. This is a convenient place to record such information. */ | |
372 | if (e->flags & EDGE_ABNORMAL) | |
373 | { | |
374 | SSA_NAME_OCCURS_IN_ABNORMAL_PHI (def) = 1; | |
04cd6268 | 375 | SSA_NAME_OCCURS_IN_ABNORMAL_PHI (PHI_RESULT (phi)) = 1; |
4ee9c684 | 376 | } |
377 | ||
04cd6268 | 378 | SET_PHI_ARG_DEF (phi, e->dest_idx, def); |
efbcb6de | 379 | gimple_phi_arg_set_location (phi, e->dest_idx, locus); |
4ee9c684 | 380 | } |
381 | ||
17889f9d | 382 | |
519d40d1 | 383 | /* Remove the Ith argument from PHI's argument list. This routine |
384 | implements removal by swapping the last alternative with the | |
385 | alternative we want to delete and then shrinking the vector, which | |
386 | is consistent with how we remove an edge from the edge vector. */ | |
4ee9c684 | 387 | |
a632e132 | 388 | static void |
1a91d914 | 389 | remove_phi_arg_num (gphi *phi, int i) |
4ee9c684 | 390 | { |
75a70cf9 | 391 | int num_elem = gimple_phi_num_args (phi); |
4ee9c684 | 392 | |
13e51728 | 393 | gcc_assert (i < num_elem); |
394 | ||
66c8f3a9 | 395 | /* Delink the item which is being removed. */ |
75a70cf9 | 396 | delink_imm_use (gimple_phi_arg_imm_use_ptr (phi, i)); |
66c8f3a9 | 397 | |
398 | /* If it is not the last element, move the last element | |
399 | to the element we want to delete, resetting all the links. */ | |
4ee9c684 | 400 | if (i != num_elem - 1) |
401 | { | |
66c8f3a9 | 402 | use_operand_p old_p, new_p; |
75a70cf9 | 403 | old_p = gimple_phi_arg_imm_use_ptr (phi, num_elem - 1); |
404 | new_p = gimple_phi_arg_imm_use_ptr (phi, i); | |
9fdf9cf6 | 405 | /* Set use on new node, and link into last element's place. */ |
66c8f3a9 | 406 | *(new_p->use) = *(old_p->use); |
407 | relink_imm_use (new_p, old_p); | |
efbcb6de | 408 | /* Move the location as well. */ |
48e1416a | 409 | gimple_phi_arg_set_location (phi, i, |
efbcb6de | 410 | gimple_phi_arg_location (phi, num_elem - 1)); |
4ee9c684 | 411 | } |
412 | ||
36fddb4b | 413 | /* Shrink the vector and return. Note that we do not have to clear |
6b34676b | 414 | PHI_ARG_DEF because the garbage collector will not look at those |
415 | elements beyond the first PHI_NUM_ARGS elements of the array. */ | |
de6bd75e | 416 | phi->nargs--; |
4ee9c684 | 417 | } |
418 | ||
17889f9d | 419 | |
1af6dc83 | 420 | /* Remove all PHI arguments associated with edge E. */ |
421 | ||
422 | void | |
423 | remove_phi_args (edge e) | |
424 | { | |
1a91d914 | 425 | gphi_iterator gsi; |
1af6dc83 | 426 | |
75a70cf9 | 427 | for (gsi = gsi_start_phis (e->dest); !gsi_end_p (gsi); gsi_next (&gsi)) |
1a91d914 | 428 | remove_phi_arg_num (gsi.phi (), |
de6bd75e | 429 | e->dest_idx); |
1af6dc83 | 430 | } |
431 | ||
17889f9d | 432 | |
75a70cf9 | 433 | /* Remove the PHI node pointed-to by iterator GSI from basic block BB. After |
434 | removal, iterator GSI is updated to point to the next PHI node in the | |
435 | sequence. If RELEASE_LHS_P is true, the LHS of this PHI node is released | |
436 | into the free pool of SSA names. */ | |
4ee9c684 | 437 | |
438 | void | |
75a70cf9 | 439 | remove_phi_node (gimple_stmt_iterator *gsi, bool release_lhs_p) |
4ee9c684 | 440 | { |
42acab1c | 441 | gimple *phi = gsi_stmt (*gsi); |
41ad616d | 442 | |
443 | if (release_lhs_p) | |
444 | insert_debug_temps_for_defs (gsi); | |
445 | ||
75a70cf9 | 446 | gsi_remove (gsi, false); |
1e49fef2 | 447 | |
448 | /* If we are deleting the PHI node, then we should release the | |
449 | SSA_NAME node so that it can be reused. */ | |
1e49fef2 | 450 | release_phi_node (phi); |
17889f9d | 451 | if (release_lhs_p) |
75a70cf9 | 452 | release_ssa_name (gimple_phi_result (phi)); |
214ed29c | 453 | } |
4ee9c684 | 454 | |
899e6126 | 455 | /* Remove all the phi nodes from BB. */ |
456 | ||
457 | void | |
458 | remove_phi_nodes (basic_block bb) | |
459 | { | |
1a91d914 | 460 | gphi_iterator gsi; |
899e6126 | 461 | |
462 | for (gsi = gsi_start_phis (bb); !gsi_end_p (gsi); ) | |
463 | remove_phi_node (&gsi, true); | |
464 | ||
465 | set_phi_nodes (bb, NULL); | |
466 | } | |
467 | ||
424a4a92 | 468 | /* Given PHI, return its RHS if the PHI is a degenerate, otherwise return |
469 | NULL. */ | |
470 | ||
471 | tree | |
1a91d914 | 472 | degenerate_phi_result (gphi *phi) |
424a4a92 | 473 | { |
474 | tree lhs = gimple_phi_result (phi); | |
475 | tree val = NULL; | |
476 | size_t i; | |
477 | ||
478 | /* Ignoring arguments which are the same as LHS, if all the remaining | |
479 | arguments are the same, then the PHI is a degenerate and has the | |
480 | value of that common argument. */ | |
481 | for (i = 0; i < gimple_phi_num_args (phi); i++) | |
482 | { | |
483 | tree arg = gimple_phi_arg_def (phi, i); | |
484 | ||
485 | if (arg == lhs) | |
486 | continue; | |
487 | else if (!arg) | |
488 | break; | |
489 | else if (!val) | |
490 | val = arg; | |
491 | else if (arg == val) | |
492 | continue; | |
493 | /* We bring in some of operand_equal_p not only to speed things | |
494 | up, but also to avoid crashing when dereferencing the type of | |
495 | a released SSA name. */ | |
496 | else if (TREE_CODE (val) != TREE_CODE (arg) | |
497 | || TREE_CODE (val) == SSA_NAME | |
498 | || !operand_equal_p (arg, val, 0)) | |
499 | break; | |
500 | } | |
501 | return (i == gimple_phi_num_args (phi) ? val : NULL); | |
502 | } | |
503 | ||
dcf1a1ec | 504 | /* Set PHI nodes of a basic block BB to SEQ. */ |
505 | ||
506 | void | |
507 | set_phi_nodes (basic_block bb, gimple_seq seq) | |
508 | { | |
509 | gimple_stmt_iterator i; | |
510 | ||
511 | gcc_checking_assert (!(bb->flags & BB_RTL)); | |
512 | bb->il.gimple.phi_nodes = seq; | |
513 | if (seq) | |
514 | for (i = gsi_start (seq); !gsi_end_p (i); gsi_next (&i)) | |
515 | gimple_set_bb (gsi_stmt (i), bb); | |
516 | } | |
424a4a92 | 517 | |
4ee9c684 | 518 | #include "gt-tree-phinodes.h" |