]>
Commit | Line | Data |
---|---|---|
67514449 | 1 | /* Backward propagation of indirect loads through PHIs. |
d1e082c2 | 2 | Copyright (C) 2007-2013 Free Software Foundation, Inc. |
67514449 RG |
3 | Contributed by Richard Guenther <rguenther@suse.de> |
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" | |
67514449 | 25 | #include "tree.h" |
67514449 RG |
26 | #include "tm_p.h" |
27 | #include "basic-block.h" | |
cf835838 | 28 | #include "gimple-pretty-print.h" |
18f429e2 | 29 | #include "gimple.h" |
45b0be94 | 30 | #include "gimplify.h" |
5be5c238 | 31 | #include "gimple-iterator.h" |
442b4905 AM |
32 | #include "gimple-ssa.h" |
33 | #include "tree-phinodes.h" | |
34 | #include "ssa-iterators.h" | |
d8a2d370 | 35 | #include "stringpool.h" |
442b4905 | 36 | #include "tree-ssanames.h" |
67514449 | 37 | #include "tree-pass.h" |
67514449 RG |
38 | #include "langhooks.h" |
39 | #include "flags.h" | |
40 | ||
41 | /* This pass propagates indirect loads through the PHI node for its | |
fa10beec | 42 | address to make the load source possibly non-addressable and to |
67514449 RG |
43 | allow for PHI optimization to trigger. |
44 | ||
45 | For example the pass changes | |
46 | ||
47 | # addr_1 = PHI <&a, &b> | |
48 | tmp_1 = *addr_1; | |
49 | ||
50 | to | |
51 | ||
52 | # tmp_1 = PHI <a, b> | |
53 | ||
fa10beec | 54 | but also handles more complex scenarios like |
67514449 RG |
55 | |
56 | D.2077_2 = &this_1(D)->a1; | |
57 | ... | |
58 | ||
59 | # b_12 = PHI <&c(2), D.2077_2(3)> | |
60 | D.2114_13 = *b_12; | |
61 | ... | |
62 | ||
63 | # b_15 = PHI <b_12(4), &b(5)> | |
64 | D.2080_5 = &this_1(D)->a0; | |
65 | ... | |
66 | ||
67 | # b_18 = PHI <D.2080_5(6), &c(7)> | |
68 | ... | |
69 | ||
70 | # b_21 = PHI <b_15(8), b_18(9)> | |
71 | D.2076_8 = *b_21; | |
72 | ||
73 | where the addresses loaded are defined by PHIs itself. | |
74 | The above happens for | |
75 | ||
76 | std::max(std::min(a0, c), std::min(std::max(a1, c), b)) | |
77 | ||
78 | where this pass transforms it to a form later PHI optimization | |
79 | recognizes and transforms it to the simple | |
80 | ||
81 | D.2109_10 = this_1(D)->a1; | |
82 | D.2110_11 = c; | |
83 | D.2114_31 = MAX_EXPR <D.2109_10, D.2110_11>; | |
84 | D.2115_14 = b; | |
85 | D.2125_17 = MIN_EXPR <D.2115_14, D.2114_31>; | |
86 | D.2119_16 = this_1(D)->a0; | |
87 | D.2124_32 = MIN_EXPR <D.2110_11, D.2119_16>; | |
88 | D.2076_33 = MAX_EXPR <D.2125_17, D.2124_32>; | |
89 | ||
90 | The pass does a dominator walk processing loads using a basic-block | |
91 | local analysis and stores the result for use by transformations on | |
92 | dominated basic-blocks. */ | |
93 | ||
94 | ||
95 | /* Structure to keep track of the value of a dereferenced PHI result | |
7f8fdb9f | 96 | and the virtual operand used for that dereference. */ |
67514449 RG |
97 | |
98 | struct phiprop_d | |
99 | { | |
100 | tree value; | |
7f8fdb9f | 101 | tree vuse; |
67514449 RG |
102 | }; |
103 | ||
104 | /* Verify if the value recorded for NAME in PHIVN is still valid at | |
105 | the start of basic block BB. */ | |
106 | ||
107 | static bool | |
108 | phivn_valid_p (struct phiprop_d *phivn, tree name, basic_block bb) | |
109 | { | |
7f8fdb9f RG |
110 | tree vuse = phivn[SSA_NAME_VERSION (name)].vuse; |
111 | gimple use_stmt; | |
112 | imm_use_iterator ui2; | |
113 | bool ok = true; | |
67514449 | 114 | |
7f8fdb9f RG |
115 | /* The def stmts of the virtual uses need to be dominated by bb. */ |
116 | gcc_assert (vuse != NULL_TREE); | |
67514449 | 117 | |
7f8fdb9f RG |
118 | FOR_EACH_IMM_USE_STMT (use_stmt, ui2, vuse) |
119 | { | |
120 | /* If BB does not dominate a VDEF, the value is invalid. */ | |
121 | if ((gimple_vdef (use_stmt) != NULL_TREE | |
122 | || gimple_code (use_stmt) == GIMPLE_PHI) | |
123 | && !dominated_by_p (CDI_DOMINATORS, gimple_bb (use_stmt), bb)) | |
67514449 | 124 | { |
7f8fdb9f RG |
125 | ok = false; |
126 | BREAK_FROM_IMM_USE_STMT (ui2); | |
67514449 | 127 | } |
67514449 RG |
128 | } |
129 | ||
7f8fdb9f | 130 | return ok; |
67514449 RG |
131 | } |
132 | ||
133 | /* Insert a new phi node for the dereference of PHI at basic_block | |
134 | BB with the virtual operands from USE_STMT. */ | |
135 | ||
136 | static tree | |
726a989a | 137 | phiprop_insert_phi (basic_block bb, gimple phi, gimple use_stmt, |
67514449 RG |
138 | struct phiprop_d *phivn, size_t n) |
139 | { | |
726a989a RB |
140 | tree res; |
141 | gimple new_phi; | |
67514449 RG |
142 | edge_iterator ei; |
143 | edge e; | |
144 | ||
726a989a | 145 | gcc_assert (is_gimple_assign (use_stmt) |
70f34814 | 146 | && gimple_assign_rhs_code (use_stmt) == MEM_REF); |
726a989a | 147 | |
67514449 RG |
148 | /* Build a new PHI node to replace the definition of |
149 | the indirect reference lhs. */ | |
726a989a | 150 | res = gimple_assign_lhs (use_stmt); |
dcc748dd | 151 | new_phi = create_phi_node (res, bb); |
67514449 | 152 | |
7f8fdb9f RG |
153 | if (dump_file && (dump_flags & TDF_DETAILS)) |
154 | { | |
155 | fprintf (dump_file, "Inserting PHI for result of load "); | |
156 | print_gimple_stmt (dump_file, use_stmt, 0, 0); | |
157 | } | |
158 | ||
67514449 RG |
159 | /* Add PHI arguments for each edge inserting loads of the |
160 | addressable operands. */ | |
161 | FOR_EACH_EDGE (e, ei, bb->preds) | |
162 | { | |
726a989a RB |
163 | tree old_arg, new_var; |
164 | gimple tmp; | |
f5045c96 | 165 | source_location locus; |
67514449 RG |
166 | |
167 | old_arg = PHI_ARG_DEF_FROM_EDGE (phi, e); | |
f5045c96 | 168 | locus = gimple_phi_arg_location_from_edge (phi, e); |
67514449 RG |
169 | while (TREE_CODE (old_arg) == SSA_NAME |
170 | && (SSA_NAME_VERSION (old_arg) >= n | |
171 | || phivn[SSA_NAME_VERSION (old_arg)].value == NULL_TREE)) | |
172 | { | |
726a989a RB |
173 | gimple def_stmt = SSA_NAME_DEF_STMT (old_arg); |
174 | old_arg = gimple_assign_rhs1 (def_stmt); | |
f5045c96 | 175 | locus = gimple_location (def_stmt); |
67514449 RG |
176 | } |
177 | ||
178 | if (TREE_CODE (old_arg) == SSA_NAME) | |
7f8fdb9f RG |
179 | { |
180 | if (dump_file && (dump_flags & TDF_DETAILS)) | |
181 | { | |
182 | fprintf (dump_file, " for edge defining "); | |
183 | print_generic_expr (dump_file, PHI_ARG_DEF_FROM_EDGE (phi, e), 0); | |
184 | fprintf (dump_file, " reusing PHI result "); | |
185 | print_generic_expr (dump_file, | |
186 | phivn[SSA_NAME_VERSION (old_arg)].value, 0); | |
187 | fprintf (dump_file, "\n"); | |
188 | } | |
189 | /* Reuse a formerly created dereference. */ | |
190 | new_var = phivn[SSA_NAME_VERSION (old_arg)].value; | |
191 | } | |
67514449 RG |
192 | else |
193 | { | |
f076deba | 194 | tree rhs = gimple_assign_rhs1 (use_stmt); |
726a989a | 195 | gcc_assert (TREE_CODE (old_arg) == ADDR_EXPR); |
83d5977e | 196 | new_var = make_ssa_name (TREE_TYPE (rhs), NULL); |
f076deba RG |
197 | if (!is_gimple_min_invariant (old_arg)) |
198 | old_arg = PHI_ARG_DEF_FROM_EDGE (phi, e); | |
199 | else | |
200 | old_arg = unshare_expr (old_arg); | |
201 | tmp = gimple_build_assign (new_var, | |
202 | fold_build2 (MEM_REF, TREE_TYPE (rhs), | |
203 | old_arg, | |
204 | TREE_OPERAND (rhs, 1))); | |
f5045c96 | 205 | gimple_set_location (tmp, locus); |
67514449 | 206 | |
726a989a | 207 | gsi_insert_on_edge (e, tmp); |
67514449 | 208 | update_stmt (tmp); |
7f8fdb9f RG |
209 | |
210 | if (dump_file && (dump_flags & TDF_DETAILS)) | |
211 | { | |
212 | fprintf (dump_file, " for edge defining "); | |
213 | print_generic_expr (dump_file, PHI_ARG_DEF_FROM_EDGE (phi, e), 0); | |
214 | fprintf (dump_file, " inserting load "); | |
215 | print_gimple_stmt (dump_file, tmp, 0, 0); | |
216 | } | |
67514449 RG |
217 | } |
218 | ||
9e227d60 | 219 | add_phi_arg (new_phi, new_var, e, locus); |
67514449 RG |
220 | } |
221 | ||
222 | update_stmt (new_phi); | |
223 | ||
7f8fdb9f RG |
224 | if (dump_file && (dump_flags & TDF_DETAILS)) |
225 | print_gimple_stmt (dump_file, new_phi, 0, 0); | |
226 | ||
67514449 RG |
227 | return res; |
228 | } | |
229 | ||
230 | /* Propagate between the phi node arguments of PHI in BB and phi result | |
231 | users. For now this matches | |
232 | # p_2 = PHI <&x, &y> | |
233 | <Lx>:; | |
234 | p_3 = p_2; | |
235 | z_2 = *p_3; | |
236 | and converts it to | |
237 | # z_2 = PHI <x, y> | |
238 | <Lx>:; | |
239 | Returns true if a transformation was done and edge insertions | |
240 | need to be committed. Global data PHIVN and N is used to track | |
241 | past transformation results. We need to be especially careful here | |
242 | with aliasing issues as we are moving memory reads. */ | |
243 | ||
244 | static bool | |
726a989a RB |
245 | propagate_with_phi (basic_block bb, gimple phi, struct phiprop_d *phivn, |
246 | size_t n) | |
67514449 RG |
247 | { |
248 | tree ptr = PHI_RESULT (phi); | |
726a989a RB |
249 | gimple use_stmt; |
250 | tree res = NULL_TREE; | |
251 | gimple_stmt_iterator gsi; | |
67514449 RG |
252 | imm_use_iterator ui; |
253 | use_operand_p arg_p, use; | |
254 | ssa_op_iter i; | |
255 | bool phi_inserted; | |
f076deba | 256 | tree type = NULL_TREE; |
67514449 | 257 | |
5006671f | 258 | if (!POINTER_TYPE_P (TREE_TYPE (ptr)) |
67514449 RG |
259 | || !is_gimple_reg_type (TREE_TYPE (TREE_TYPE (ptr)))) |
260 | return false; | |
261 | ||
262 | /* Check if we can "cheaply" dereference all phi arguments. */ | |
263 | FOR_EACH_PHI_ARG (arg_p, phi, i, SSA_OP_USE) | |
264 | { | |
265 | tree arg = USE_FROM_PTR (arg_p); | |
266 | /* Walk the ssa chain until we reach a ssa name we already | |
267 | created a value for or we reach a definition of the form | |
268 | ssa_name_n = &var; */ | |
269 | while (TREE_CODE (arg) == SSA_NAME | |
270 | && !SSA_NAME_IS_DEFAULT_DEF (arg) | |
271 | && (SSA_NAME_VERSION (arg) >= n | |
272 | || phivn[SSA_NAME_VERSION (arg)].value == NULL_TREE)) | |
273 | { | |
726a989a | 274 | gimple def_stmt = SSA_NAME_DEF_STMT (arg); |
e49a540c | 275 | if (!gimple_assign_single_p (def_stmt)) |
67514449 | 276 | return false; |
726a989a | 277 | arg = gimple_assign_rhs1 (def_stmt); |
67514449 | 278 | } |
f076deba | 279 | if (TREE_CODE (arg) != ADDR_EXPR |
67514449 | 280 | && !(TREE_CODE (arg) == SSA_NAME |
2970ccb3 | 281 | && SSA_NAME_VERSION (arg) < n |
67514449 | 282 | && phivn[SSA_NAME_VERSION (arg)].value != NULL_TREE |
f076deba RG |
283 | && (!type |
284 | || types_compatible_p | |
285 | (type, TREE_TYPE (phivn[SSA_NAME_VERSION (arg)].value))) | |
67514449 RG |
286 | && phivn_valid_p (phivn, arg, bb))) |
287 | return false; | |
f076deba RG |
288 | if (!type |
289 | && TREE_CODE (arg) == SSA_NAME) | |
290 | type = TREE_TYPE (phivn[SSA_NAME_VERSION (arg)].value); | |
67514449 RG |
291 | } |
292 | ||
293 | /* Find a dereferencing use. First follow (single use) ssa | |
294 | copy chains for ptr. */ | |
295 | while (single_imm_use (ptr, &use, &use_stmt) | |
726a989a RB |
296 | && gimple_assign_ssa_name_copy_p (use_stmt)) |
297 | ptr = gimple_assign_lhs (use_stmt); | |
67514449 RG |
298 | |
299 | /* Replace the first dereference of *ptr if there is one and if we | |
300 | can move the loads to the place of the ptr phi node. */ | |
301 | phi_inserted = false; | |
302 | FOR_EACH_IMM_USE_STMT (use_stmt, ui, ptr) | |
303 | { | |
7f8fdb9f | 304 | gimple def_stmt; |
67514449 RG |
305 | tree vuse; |
306 | ||
307 | /* Check whether this is a load of *ptr. */ | |
726a989a | 308 | if (!(is_gimple_assign (use_stmt) |
b8698a0f | 309 | && TREE_CODE (gimple_assign_lhs (use_stmt)) == SSA_NAME |
70f34814 | 310 | && gimple_assign_rhs_code (use_stmt) == MEM_REF |
726a989a | 311 | && TREE_OPERAND (gimple_assign_rhs1 (use_stmt), 0) == ptr |
70f34814 | 312 | && integer_zerop (TREE_OPERAND (gimple_assign_rhs1 (use_stmt), 1)) |
f076deba RG |
313 | && (!type |
314 | || types_compatible_p | |
315 | (TREE_TYPE (gimple_assign_lhs (use_stmt)), type)) | |
67514449 | 316 | /* We cannot replace a load that may throw or is volatile. */ |
726a989a | 317 | && !stmt_can_throw_internal (use_stmt))) |
67514449 RG |
318 | continue; |
319 | ||
7f8fdb9f RG |
320 | /* Check if we can move the loads. The def stmt of the virtual use |
321 | needs to be in a different basic block dominating bb. */ | |
322 | vuse = gimple_vuse (use_stmt); | |
323 | def_stmt = SSA_NAME_DEF_STMT (vuse); | |
324 | if (!SSA_NAME_IS_DEFAULT_DEF (vuse) | |
325 | && (gimple_bb (def_stmt) == bb | |
326 | || !dominated_by_p (CDI_DOMINATORS, | |
327 | bb, gimple_bb (def_stmt)))) | |
328 | goto next; | |
67514449 RG |
329 | |
330 | /* Found a proper dereference. Insert a phi node if this | |
331 | is the first load transformation. */ | |
332 | if (!phi_inserted) | |
333 | { | |
334 | res = phiprop_insert_phi (bb, phi, use_stmt, phivn, n); | |
f076deba | 335 | type = TREE_TYPE (res); |
67514449 RG |
336 | |
337 | /* Remember the value we created for *ptr. */ | |
338 | phivn[SSA_NAME_VERSION (ptr)].value = res; | |
7f8fdb9f | 339 | phivn[SSA_NAME_VERSION (ptr)].vuse = vuse; |
67514449 RG |
340 | |
341 | /* Remove old stmt. The phi is taken care of by DCE, if we | |
342 | want to delete it here we also have to delete all intermediate | |
343 | copies. */ | |
726a989a | 344 | gsi = gsi_for_stmt (use_stmt); |
b1193f61 | 345 | gsi_remove (&gsi, true); |
67514449 RG |
346 | |
347 | phi_inserted = true; | |
348 | } | |
349 | else | |
350 | { | |
351 | /* Further replacements are easy, just make a copy out of the | |
352 | load. */ | |
726a989a | 353 | gimple_assign_set_rhs1 (use_stmt, res); |
67514449 RG |
354 | update_stmt (use_stmt); |
355 | } | |
356 | ||
357 | next:; | |
358 | /* Continue searching for a proper dereference. */ | |
359 | } | |
360 | ||
361 | return phi_inserted; | |
362 | } | |
363 | ||
67514449 RG |
364 | /* Main entry for phiprop pass. */ |
365 | ||
366 | static unsigned int | |
367 | tree_ssa_phiprop (void) | |
368 | { | |
9771b263 | 369 | vec<basic_block> bbs; |
67514449 | 370 | struct phiprop_d *phivn; |
b8698a0f | 371 | bool did_something = false; |
438c239d RG |
372 | basic_block bb; |
373 | gimple_stmt_iterator gsi; | |
374 | unsigned i; | |
2970ccb3 | 375 | size_t n; |
67514449 RG |
376 | |
377 | calculate_dominance_info (CDI_DOMINATORS); | |
378 | ||
2970ccb3 RG |
379 | n = num_ssa_names; |
380 | phivn = XCNEWVEC (struct phiprop_d, n); | |
67514449 | 381 | |
438c239d RG |
382 | /* Walk the dominator tree in preorder. */ |
383 | bbs = get_all_dominated_blocks (CDI_DOMINATORS, | |
384 | single_succ (ENTRY_BLOCK_PTR)); | |
9771b263 | 385 | FOR_EACH_VEC_ELT (bbs, i, bb) |
438c239d | 386 | for (gsi = gsi_start_phis (bb); !gsi_end_p (gsi); gsi_next (&gsi)) |
2970ccb3 | 387 | did_something |= propagate_with_phi (bb, gsi_stmt (gsi), phivn, n); |
438c239d RG |
388 | |
389 | if (did_something) | |
726a989a | 390 | gsi_commit_edge_inserts (); |
67514449 | 391 | |
9771b263 | 392 | bbs.release (); |
67514449 RG |
393 | free (phivn); |
394 | ||
395 | return 0; | |
396 | } | |
397 | ||
398 | static bool | |
399 | gate_phiprop (void) | |
400 | { | |
248fc9f3 | 401 | return flag_tree_phiprop; |
67514449 RG |
402 | } |
403 | ||
27a4cd48 DM |
404 | namespace { |
405 | ||
406 | const pass_data pass_data_phiprop = | |
8ddbbcae | 407 | { |
27a4cd48 DM |
408 | GIMPLE_PASS, /* type */ |
409 | "phiprop", /* name */ | |
410 | OPTGROUP_NONE, /* optinfo_flags */ | |
411 | true, /* has_gate */ | |
412 | true, /* has_execute */ | |
413 | TV_TREE_PHIPROP, /* tv_id */ | |
414 | ( PROP_cfg | PROP_ssa ), /* properties_required */ | |
415 | 0, /* properties_provided */ | |
416 | 0, /* properties_destroyed */ | |
417 | 0, /* todo_flags_start */ | |
418 | ( TODO_update_ssa | TODO_verify_ssa ), /* todo_flags_finish */ | |
67514449 | 419 | }; |
27a4cd48 DM |
420 | |
421 | class pass_phiprop : public gimple_opt_pass | |
422 | { | |
423 | public: | |
c3284718 RS |
424 | pass_phiprop (gcc::context *ctxt) |
425 | : gimple_opt_pass (pass_data_phiprop, ctxt) | |
27a4cd48 DM |
426 | {} |
427 | ||
428 | /* opt_pass methods: */ | |
429 | bool gate () { return gate_phiprop (); } | |
430 | unsigned int execute () { return tree_ssa_phiprop (); } | |
431 | ||
432 | }; // class pass_phiprop | |
433 | ||
434 | } // anon namespace | |
435 | ||
436 | gimple_opt_pass * | |
437 | make_pass_phiprop (gcc::context *ctxt) | |
438 | { | |
439 | return new pass_phiprop (ctxt); | |
440 | } |