]>
Commit | Line | Data |
---|---|---|
6de9cd9a | 1 | /* Conditional constant propagation pass for the GNU compiler. |
1e052c19 KH |
2 | Copyright (C) 2000, 2001, 2002, 2003, 2004, 2005 |
3 | Free Software Foundation, Inc. | |
6de9cd9a DN |
4 | Adapted from original RTL SSA-CCP by Daniel Berlin <dberlin@dberlin.org> |
5 | Adapted to GIMPLE trees by Diego Novillo <dnovillo@redhat.com> | |
6 | ||
7 | This file is part of GCC. | |
8 | ||
9 | GCC is free software; you can redistribute it and/or modify it | |
10 | under the terms of the GNU General Public License as published by the | |
11 | Free Software Foundation; either version 2, or (at your option) any | |
12 | later version. | |
13 | ||
14 | GCC is distributed in the hope that it will be useful, but WITHOUT | |
15 | ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or | |
16 | FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License | |
17 | for more details. | |
18 | ||
19 | You should have received a copy of the GNU General Public License | |
20 | along with GCC; see the file COPYING. If not, write to the Free | |
21 | Software Foundation, 59 Temple Place - Suite 330, Boston, MA | |
22 | 02111-1307, USA. */ | |
23 | ||
0bca51f0 DN |
24 | /* Conditional constant propagation (CCP) is based on the SSA |
25 | propagation engine (tree-ssa-propagate.c). Constant assignments of | |
26 | the form VAR = CST are propagated from the assignments into uses of | |
27 | VAR, which in turn may generate new constants. The simulation uses | |
28 | a four level lattice to keep track of constant values associated | |
29 | with SSA names. Given an SSA name V_i, it may take one of the | |
30 | following values: | |
31 | ||
32 | UNINITIALIZED -> This is the default starting value. V_i | |
33 | has not been processed yet. | |
34 | ||
35 | UNDEFINED -> V_i is a local variable whose definition | |
36 | has not been processed yet. Therefore we | |
37 | don't yet know if its value is a constant | |
38 | or not. | |
39 | ||
40 | CONSTANT -> V_i has been found to hold a constant | |
41 | value C. | |
42 | ||
43 | VARYING -> V_i cannot take a constant value, or if it | |
44 | does, it is not possible to determine it | |
45 | at compile time. | |
46 | ||
47 | The core of SSA-CCP is in ccp_visit_stmt and ccp_visit_phi_node: | |
48 | ||
49 | 1- In ccp_visit_stmt, we are interested in assignments whose RHS | |
50 | evaluates into a constant and conditional jumps whose predicate | |
51 | evaluates into a boolean true or false. When an assignment of | |
52 | the form V_i = CONST is found, V_i's lattice value is set to | |
53 | CONSTANT and CONST is associated with it. This causes the | |
54 | propagation engine to add all the SSA edges coming out the | |
55 | assignment into the worklists, so that statements that use V_i | |
56 | can be visited. | |
57 | ||
58 | If the statement is a conditional with a constant predicate, we | |
59 | mark the outgoing edges as executable or not executable | |
60 | depending on the predicate's value. This is then used when | |
61 | visiting PHI nodes to know when a PHI argument can be ignored. | |
62 | ||
63 | ||
64 | 2- In ccp_visit_phi_node, if all the PHI arguments evaluate to the | |
65 | same constant C, then the LHS of the PHI is set to C. This | |
66 | evaluation is known as the "meet operation". Since one of the | |
67 | goals of this evaluation is to optimistically return constant | |
68 | values as often as possible, it uses two main short cuts: | |
69 | ||
70 | - If an argument is flowing in through a non-executable edge, it | |
71 | is ignored. This is useful in cases like this: | |
72 | ||
73 | if (PRED) | |
74 | a_9 = 3; | |
75 | else | |
76 | a_10 = 100; | |
77 | a_11 = PHI (a_9, a_10) | |
78 | ||
79 | If PRED is known to always evaluate to false, then we can | |
80 | assume that a_11 will always take its value from a_10, meaning | |
81 | that instead of consider it VARYING (a_9 and a_10 have | |
82 | different values), we can consider it CONSTANT 100. | |
83 | ||
84 | - If an argument has an UNDEFINED value, then it does not affect | |
85 | the outcome of the meet operation. If a variable V_i has an | |
86 | UNDEFINED value, it means that either its defining statement | |
87 | hasn't been visited yet or V_i has no defining statement, in | |
88 | which case the original symbol 'V' is being used | |
89 | uninitialized. Since 'V' is a local variable, the compiler | |
90 | may assume any initial value for it. | |
91 | ||
92 | ||
93 | After propagation, every variable V_i that ends up with a lattice | |
94 | value of CONSTANT will have the associated constant value in the | |
95 | array CONST_VAL[i].VALUE. That is fed into substitute_and_fold for | |
96 | final substitution and folding. | |
97 | ||
98 | ||
99 | Constant propagation in stores and loads (STORE-CCP) | |
100 | ---------------------------------------------------- | |
101 | ||
102 | While CCP has all the logic to propagate constants in GIMPLE | |
103 | registers, it is missing the ability to associate constants with | |
104 | stores and loads (i.e., pointer dereferences, structures and | |
105 | global/aliased variables). We don't keep loads and stores in | |
106 | SSA, but we do build a factored use-def web for them (in the | |
107 | virtual operands). | |
108 | ||
109 | For instance, consider the following code fragment: | |
110 | ||
111 | struct A a; | |
112 | const int B = 42; | |
113 | ||
114 | void foo (int i) | |
115 | { | |
116 | if (i > 10) | |
117 | a.a = 42; | |
118 | else | |
119 | { | |
120 | a.b = 21; | |
121 | a.a = a.b + 21; | |
122 | } | |
123 | ||
124 | if (a.a != B) | |
125 | never_executed (); | |
126 | } | |
127 | ||
128 | We should be able to deduce that the predicate 'a.a != B' is always | |
129 | false. To achieve this, we associate constant values to the SSA | |
130 | names in the V_MAY_DEF and V_MUST_DEF operands for each store. | |
131 | Additionally, since we also glob partial loads/stores with the base | |
132 | symbol, we also keep track of the memory reference where the | |
133 | constant value was stored (in the MEM_REF field of PROP_VALUE_T). | |
134 | For instance, | |
135 | ||
136 | # a_5 = V_MAY_DEF <a_4> | |
137 | a.a = 2; | |
138 | ||
139 | # VUSE <a_5> | |
140 | x_3 = a.b; | |
141 | ||
142 | In the example above, CCP will associate value '2' with 'a_5', but | |
143 | it would be wrong to replace the load from 'a.b' with '2', because | |
144 | '2' had been stored into a.a. | |
145 | ||
146 | To support STORE-CCP, it is necessary to add a new value to the | |
147 | constant propagation lattice. When evaluating a load for a memory | |
148 | reference we can no longer assume a value of UNDEFINED if we | |
149 | haven't seen a preceding store to the same memory location. | |
150 | Consider, for instance global variables: | |
151 | ||
152 | int A; | |
153 | ||
154 | foo (int i) | |
155 | { | |
156 | if (i_3 > 10) | |
157 | A_4 = 3; | |
158 | # A_5 = PHI (A_4, A_2); | |
159 | ||
160 | # VUSE <A_5> | |
161 | A.0_6 = A; | |
162 | ||
163 | return A.0_6; | |
164 | } | |
165 | ||
166 | The value of A_2 cannot be assumed to be UNDEFINED, as it may have | |
167 | been defined outside of foo. If we were to assume it UNDEFINED, we | |
168 | would erroneously optimize the above into 'return 3;'. Therefore, | |
169 | when doing STORE-CCP, we introduce a fifth lattice value | |
170 | (UNKNOWN_VAL), which overrides any other value when computing the | |
171 | meet operation in PHI nodes. | |
172 | ||
173 | Though STORE-CCP is not too expensive, it does have to do more work | |
174 | than regular CCP, so it is only enabled at -O2. Both regular CCP | |
175 | and STORE-CCP use the exact same algorithm. The only distinction | |
176 | is that when doing STORE-CCP, the boolean variable DO_STORE_CCP is | |
177 | set to true. This affects the evaluation of statements and PHI | |
178 | nodes. | |
6de9cd9a DN |
179 | |
180 | References: | |
181 | ||
182 | Constant propagation with conditional branches, | |
183 | Wegman and Zadeck, ACM TOPLAS 13(2):181-210. | |
184 | ||
185 | Building an Optimizing Compiler, | |
186 | Robert Morgan, Butterworth-Heinemann, 1998, Section 8.9. | |
187 | ||
188 | Advanced Compiler Design and Implementation, | |
189 | Steven Muchnick, Morgan Kaufmann, 1997, Section 12.6 */ | |
190 | ||
191 | #include "config.h" | |
192 | #include "system.h" | |
193 | #include "coretypes.h" | |
194 | #include "tm.h" | |
6de9cd9a | 195 | #include "tree.h" |
750628d8 | 196 | #include "flags.h" |
6de9cd9a DN |
197 | #include "rtl.h" |
198 | #include "tm_p.h" | |
750628d8 | 199 | #include "ggc.h" |
6de9cd9a | 200 | #include "basic-block.h" |
750628d8 DN |
201 | #include "output.h" |
202 | #include "errors.h" | |
203 | #include "expr.h" | |
204 | #include "function.h" | |
6de9cd9a | 205 | #include "diagnostic.h" |
750628d8 | 206 | #include "timevar.h" |
6de9cd9a | 207 | #include "tree-dump.h" |
750628d8 | 208 | #include "tree-flow.h" |
6de9cd9a | 209 | #include "tree-pass.h" |
750628d8 DN |
210 | #include "tree-ssa-propagate.h" |
211 | #include "langhooks.h" | |
6de9cd9a DN |
212 | |
213 | ||
214 | /* Possible lattice values. */ | |
215 | typedef enum | |
216 | { | |
217 | UNINITIALIZED = 0, | |
218 | UNDEFINED, | |
173b818d | 219 | UNKNOWN_VAL, |
6de9cd9a DN |
220 | CONSTANT, |
221 | VARYING | |
0bca51f0 | 222 | } ccp_lattice_t; |
6de9cd9a | 223 | |
0bca51f0 DN |
224 | /* Array of propagated constant values. After propagation, |
225 | CONST_VAL[I].VALUE holds the constant value for SSA_NAME(I). If | |
226 | the constant is held in an SSA name representing a memory store | |
227 | (i.e., a V_MAY_DEF or V_MUST_DEF), CONST_VAL[I].MEM_REF will | |
228 | contain the actual memory reference used to store (i.e., the LHS of | |
229 | the assignment doing the store). */ | |
230 | prop_value_t *const_val; | |
6de9cd9a | 231 | |
0bca51f0 DN |
232 | /* True if we are also propagating constants in stores and loads. */ |
233 | static bool do_store_ccp; | |
6de9cd9a | 234 | |
0bca51f0 | 235 | /* Dump constant propagation value VAL to file OUTF prefixed by PREFIX. */ |
95eec0d6 DB |
236 | |
237 | static void | |
0bca51f0 | 238 | dump_lattice_value (FILE *outf, const char *prefix, prop_value_t val) |
95eec0d6 | 239 | { |
750628d8 | 240 | switch (val.lattice_val) |
95eec0d6 | 241 | { |
0bca51f0 DN |
242 | case UNINITIALIZED: |
243 | fprintf (outf, "%sUNINITIALIZED", prefix); | |
244 | break; | |
750628d8 DN |
245 | case UNDEFINED: |
246 | fprintf (outf, "%sUNDEFINED", prefix); | |
247 | break; | |
248 | case VARYING: | |
249 | fprintf (outf, "%sVARYING", prefix); | |
250 | break; | |
251 | case UNKNOWN_VAL: | |
252 | fprintf (outf, "%sUNKNOWN_VAL", prefix); | |
253 | break; | |
254 | case CONSTANT: | |
255 | fprintf (outf, "%sCONSTANT ", prefix); | |
0bca51f0 | 256 | print_generic_expr (outf, val.value, dump_flags); |
750628d8 DN |
257 | break; |
258 | default: | |
1e128c5f | 259 | gcc_unreachable (); |
750628d8 | 260 | } |
95eec0d6 | 261 | } |
6de9cd9a | 262 | |
6de9cd9a | 263 | |
0bca51f0 DN |
264 | /* Print lattice value VAL to stderr. */ |
265 | ||
266 | void debug_lattice_value (prop_value_t val); | |
267 | ||
268 | void | |
269 | debug_lattice_value (prop_value_t val) | |
270 | { | |
271 | dump_lattice_value (stderr, "", val); | |
272 | fprintf (stderr, "\n"); | |
273 | } | |
6de9cd9a | 274 | |
6de9cd9a | 275 | |
0bca51f0 DN |
276 | /* Compute a default value for variable VAR and store it in the |
277 | CONST_VAL array. The following rules are used to get default | |
278 | values: | |
95eec0d6 | 279 | |
0bca51f0 DN |
280 | 1- Global and static variables that are declared constant are |
281 | considered CONSTANT. | |
282 | ||
283 | 2- Any other value is considered UNDEFINED. This is useful when | |
750628d8 DN |
284 | considering PHI nodes. PHI arguments that are undefined do not |
285 | change the constant value of the PHI node, which allows for more | |
0bca51f0 | 286 | constants to be propagated. |
6de9cd9a | 287 | |
0bca51f0 DN |
288 | 3- If SSA_NAME_VALUE is set and it is a constant, its value is |
289 | used. | |
6de9cd9a | 290 | |
0bca51f0 DN |
291 | 4- Variables defined by statements other than assignments and PHI |
292 | nodes are considered VARYING. | |
6de9cd9a | 293 | |
0bca51f0 DN |
294 | 5- Variables that are not GIMPLE registers are considered |
295 | UNKNOWN_VAL, which is really a stronger version of UNDEFINED. | |
296 | It's used to avoid the short circuit evaluation implied by | |
297 | UNDEFINED in ccp_lattice_meet. */ | |
6de9cd9a | 298 | |
0bca51f0 DN |
299 | static prop_value_t |
300 | get_default_value (tree var) | |
301 | { | |
302 | tree sym = SSA_NAME_VAR (var); | |
303 | prop_value_t val = { UNINITIALIZED, NULL_TREE, NULL_TREE }; | |
304 | ||
305 | if (!do_store_ccp && !is_gimple_reg (var)) | |
6de9cd9a | 306 | { |
0bca51f0 DN |
307 | /* Short circuit for regular CCP. We are not interested in any |
308 | non-register when DO_STORE_CCP is false. */ | |
750628d8 | 309 | val.lattice_val = VARYING; |
6de9cd9a | 310 | } |
0bca51f0 DN |
311 | else if (SSA_NAME_VALUE (var) |
312 | && is_gimple_min_invariant (SSA_NAME_VALUE (var))) | |
750628d8 | 313 | { |
0bca51f0 DN |
314 | val.lattice_val = CONSTANT; |
315 | val.value = SSA_NAME_VALUE (var); | |
750628d8 | 316 | } |
0bca51f0 DN |
317 | else if (TREE_STATIC (sym) |
318 | && TREE_READONLY (sym) | |
319 | && DECL_INITIAL (sym) | |
320 | && is_gimple_min_invariant (DECL_INITIAL (sym))) | |
750628d8 | 321 | { |
0bca51f0 DN |
322 | /* Globals and static variables declared 'const' take their |
323 | initial value. */ | |
324 | val.lattice_val = CONSTANT; | |
325 | val.value = DECL_INITIAL (sym); | |
326 | val.mem_ref = sym; | |
750628d8 DN |
327 | } |
328 | else | |
329 | { | |
750628d8 | 330 | tree stmt = SSA_NAME_DEF_STMT (var); |
6de9cd9a | 331 | |
0bca51f0 DN |
332 | if (IS_EMPTY_STMT (stmt)) |
333 | { | |
334 | /* Variables defined by an empty statement are those used | |
335 | before being initialized. If VAR is a local variable, we | |
336 | can assume initially that it is UNDEFINED. If we are | |
337 | doing STORE-CCP, function arguments and non-register | |
338 | variables are initially UNKNOWN_VAL, because we cannot | |
339 | discard the value incoming from outside of this function | |
340 | (see ccp_lattice_meet for details). */ | |
341 | if (is_gimple_reg (sym) && TREE_CODE (sym) != PARM_DECL) | |
342 | val.lattice_val = UNDEFINED; | |
343 | else if (do_store_ccp) | |
344 | val.lattice_val = UNKNOWN_VAL; | |
345 | else | |
750628d8 DN |
346 | val.lattice_val = VARYING; |
347 | } | |
0bca51f0 DN |
348 | else if (TREE_CODE (stmt) == MODIFY_EXPR |
349 | || TREE_CODE (stmt) == PHI_NODE) | |
350 | { | |
351 | /* Any other variable defined by an assignment or a PHI node | |
352 | is considered UNDEFINED (or UNKNOWN_VAL if VAR is not a | |
353 | GIMPLE register). */ | |
354 | val.lattice_val = is_gimple_reg (sym) ? UNDEFINED : UNKNOWN_VAL; | |
355 | } | |
356 | else | |
357 | { | |
358 | /* Otherwise, VAR will never take on a constant value. */ | |
359 | val.lattice_val = VARYING; | |
360 | } | |
750628d8 | 361 | } |
6de9cd9a | 362 | |
750628d8 DN |
363 | return val; |
364 | } | |
6de9cd9a | 365 | |
6de9cd9a | 366 | |
0bca51f0 DN |
367 | /* Get the constant value associated with variable VAR. If |
368 | MAY_USE_DEFAULT_P is true, call get_default_value on variables that | |
369 | have the lattice value UNINITIALIZED. */ | |
6de9cd9a | 370 | |
0bca51f0 DN |
371 | static prop_value_t * |
372 | get_value (tree var, bool may_use_default_p) | |
373 | { | |
374 | prop_value_t *val = &const_val[SSA_NAME_VERSION (var)]; | |
375 | if (may_use_default_p && val->lattice_val == UNINITIALIZED) | |
6de9cd9a DN |
376 | *val = get_default_value (var); |
377 | ||
378 | return val; | |
379 | } | |
380 | ||
381 | ||
0bca51f0 DN |
382 | /* Set the value for variable VAR to NEW_VAL. Return true if the new |
383 | value is different from VAR's previous value. */ | |
6de9cd9a | 384 | |
750628d8 | 385 | static bool |
0bca51f0 | 386 | set_lattice_value (tree var, prop_value_t new_val) |
6de9cd9a | 387 | { |
0bca51f0 DN |
388 | prop_value_t *old_val = get_value (var, false); |
389 | ||
390 | /* Lattice transitions must always be monotonically increasing in | |
391 | value. We allow two exceptions: | |
392 | ||
393 | 1- If *OLD_VAL and NEW_VAL are the same, return false to | |
394 | inform the caller that this was a non-transition. | |
395 | ||
396 | 2- If we are doing store-ccp (i.e., DOING_STORE_CCP is true), | |
397 | allow CONSTANT->UNKNOWN_VAL. The UNKNOWN_VAL state is a | |
398 | special type of UNDEFINED state which prevents the short | |
399 | circuit evaluation of PHI arguments (see ccp_visit_phi_node | |
400 | and ccp_lattice_meet). */ | |
401 | gcc_assert (old_val->lattice_val <= new_val.lattice_val | |
402 | || (old_val->lattice_val == new_val.lattice_val | |
403 | && old_val->value == new_val.value | |
404 | && old_val->mem_ref == new_val.mem_ref) | |
405 | || (do_store_ccp | |
406 | && old_val->lattice_val == CONSTANT | |
407 | && new_val.lattice_val == UNKNOWN_VAL)); | |
408 | ||
409 | if (old_val->lattice_val != new_val.lattice_val) | |
6de9cd9a | 410 | { |
750628d8 DN |
411 | if (dump_file && (dump_flags & TDF_DETAILS)) |
412 | { | |
0bca51f0 DN |
413 | dump_lattice_value (dump_file, "Lattice value changed to ", new_val); |
414 | fprintf (dump_file, ". %sdding SSA edges to worklist.\n", | |
415 | new_val.lattice_val != UNDEFINED ? "A" : "Not a"); | |
750628d8 DN |
416 | } |
417 | ||
0bca51f0 DN |
418 | *old_val = new_val; |
419 | ||
420 | /* Transitions UNINITIALIZED -> UNDEFINED are never interesting | |
421 | for propagation purposes. In these cases return false to | |
422 | avoid doing useless work. */ | |
423 | return (new_val.lattice_val != UNDEFINED); | |
6de9cd9a | 424 | } |
750628d8 DN |
425 | |
426 | return false; | |
6de9cd9a DN |
427 | } |
428 | ||
429 | ||
0bca51f0 | 430 | /* Return the likely CCP lattice value for STMT. |
6de9cd9a | 431 | |
750628d8 | 432 | If STMT has no operands, then return CONSTANT. |
6de9cd9a | 433 | |
750628d8 | 434 | Else if any operands of STMT are undefined, then return UNDEFINED. |
6de9cd9a | 435 | |
750628d8 | 436 | Else if any operands of STMT are constants, then return CONSTANT. |
6de9cd9a | 437 | |
750628d8 | 438 | Else return VARYING. */ |
6de9cd9a | 439 | |
0bca51f0 | 440 | static ccp_lattice_t |
750628d8 DN |
441 | likely_value (tree stmt) |
442 | { | |
0bca51f0 | 443 | bool found_constant; |
750628d8 DN |
444 | stmt_ann_t ann; |
445 | tree use; | |
446 | ssa_op_iter iter; | |
6de9cd9a | 447 | |
750628d8 | 448 | ann = stmt_ann (stmt); |
0bca51f0 DN |
449 | |
450 | /* If the statement has volatile operands, it won't fold to a | |
451 | constant value. */ | |
452 | if (ann->has_volatile_ops) | |
453 | return VARYING; | |
454 | ||
455 | /* If we are not doing store-ccp, statements with loads | |
456 | and/or stores will never fold into a constant. */ | |
457 | if (!do_store_ccp | |
458 | && (ann->makes_aliased_stores | |
459 | || ann->makes_aliased_loads | |
f47c96aa | 460 | || !ZERO_SSA_OPERANDS (stmt, SSA_OP_ALL_VIRTUALS))) |
750628d8 | 461 | return VARYING; |
6de9cd9a | 462 | |
0bca51f0 DN |
463 | |
464 | /* A CALL_EXPR is assumed to be varying. NOTE: This may be overly | |
465 | conservative, in the presence of const and pure calls. */ | |
750628d8 DN |
466 | if (get_call_expr_in (stmt) != NULL_TREE) |
467 | return VARYING; | |
6de9cd9a | 468 | |
0bca51f0 DN |
469 | /* Anything other than assignments and conditional jumps are not |
470 | interesting for CCP. */ | |
471 | if (TREE_CODE (stmt) != MODIFY_EXPR | |
472 | && TREE_CODE (stmt) != COND_EXPR | |
473 | && TREE_CODE (stmt) != SWITCH_EXPR) | |
474 | return VARYING; | |
475 | ||
0bca51f0 DN |
476 | found_constant = false; |
477 | FOR_EACH_SSA_TREE_OPERAND (use, stmt, iter, SSA_OP_USE|SSA_OP_VUSE) | |
750628d8 | 478 | { |
0bca51f0 | 479 | prop_value_t *val = get_value (use, true); |
750628d8 | 480 | |
0bca51f0 DN |
481 | if (val->lattice_val == VARYING) |
482 | return VARYING; | |
750628d8 | 483 | |
750628d8 | 484 | if (val->lattice_val == UNKNOWN_VAL) |
0bca51f0 DN |
485 | { |
486 | /* UNKNOWN_VAL is invalid when not doing STORE-CCP. */ | |
487 | gcc_assert (do_store_ccp); | |
488 | return UNKNOWN_VAL; | |
489 | } | |
490 | ||
750628d8 | 491 | if (val->lattice_val == CONSTANT) |
0bca51f0 | 492 | found_constant = true; |
6de9cd9a | 493 | } |
750628d8 | 494 | |
0bca51f0 | 495 | if (found_constant |
f47c96aa AM |
496 | || ZERO_SSA_OPERANDS (stmt, SSA_OP_USE) |
497 | || ZERO_SSA_OPERANDS (stmt, SSA_OP_VUSE)) | |
0bca51f0 DN |
498 | return CONSTANT; |
499 | ||
500 | return UNDEFINED; | |
6de9cd9a DN |
501 | } |
502 | ||
503 | ||
750628d8 | 504 | /* Initialize local data structures for CCP. */ |
6de9cd9a DN |
505 | |
506 | static void | |
750628d8 | 507 | ccp_initialize (void) |
6de9cd9a | 508 | { |
750628d8 | 509 | basic_block bb; |
6de9cd9a | 510 | |
0bca51f0 DN |
511 | const_val = xmalloc (num_ssa_names * sizeof (*const_val)); |
512 | memset (const_val, 0, num_ssa_names * sizeof (*const_val)); | |
6de9cd9a | 513 | |
750628d8 DN |
514 | /* Initialize simulation flags for PHI nodes and statements. */ |
515 | FOR_EACH_BB (bb) | |
6de9cd9a | 516 | { |
750628d8 | 517 | block_stmt_iterator i; |
6de9cd9a | 518 | |
750628d8 DN |
519 | for (i = bsi_start (bb); !bsi_end_p (i); bsi_next (&i)) |
520 | { | |
521 | bool is_varying = false; | |
522 | tree stmt = bsi_stmt (i); | |
6de9cd9a | 523 | |
0bca51f0 | 524 | if (likely_value (stmt) == VARYING) |
6de9cd9a | 525 | |
750628d8 | 526 | { |
0bca51f0 DN |
527 | tree def; |
528 | ssa_op_iter iter; | |
529 | ||
530 | /* If the statement will not produce a constant, mark | |
531 | all its outputs VARYING. */ | |
532 | FOR_EACH_SSA_TREE_OPERAND (def, stmt, iter, SSA_OP_ALL_DEFS) | |
533 | get_value (def, false)->lattice_val = VARYING; | |
534 | ||
535 | /* Never mark conditional jumps with DONT_SIMULATE_AGAIN, | |
536 | otherwise the propagator will never add the outgoing | |
537 | control edges. */ | |
538 | if (TREE_CODE (stmt) != COND_EXPR | |
539 | && TREE_CODE (stmt) != SWITCH_EXPR) | |
540 | is_varying = true; | |
750628d8 DN |
541 | } |
542 | ||
750628d8 DN |
543 | DONT_SIMULATE_AGAIN (stmt) = is_varying; |
544 | } | |
6de9cd9a DN |
545 | } |
546 | ||
750628d8 DN |
547 | /* Now process PHI nodes. */ |
548 | FOR_EACH_BB (bb) | |
6de9cd9a | 549 | { |
0bca51f0 | 550 | tree phi; |
750628d8 DN |
551 | |
552 | for (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi)) | |
553 | { | |
0bca51f0 DN |
554 | int i; |
555 | tree arg; | |
556 | prop_value_t *val = get_value (PHI_RESULT (phi), false); | |
750628d8 | 557 | |
0bca51f0 | 558 | for (i = 0; i < PHI_NUM_ARGS (phi); i++) |
750628d8 | 559 | { |
0bca51f0 | 560 | arg = PHI_ARG_DEF (phi, i); |
750628d8 | 561 | |
0bca51f0 DN |
562 | if (TREE_CODE (arg) == SSA_NAME |
563 | && get_value (arg, false)->lattice_val == VARYING) | |
750628d8 | 564 | { |
0bca51f0 DN |
565 | val->lattice_val = VARYING; |
566 | break; | |
750628d8 DN |
567 | } |
568 | } | |
569 | ||
570 | DONT_SIMULATE_AGAIN (phi) = (val->lattice_val == VARYING); | |
571 | } | |
6de9cd9a | 572 | } |
750628d8 | 573 | } |
6de9cd9a | 574 | |
6de9cd9a | 575 | |
0bca51f0 DN |
576 | /* Do final substitution of propagated values, cleanup the flowgraph and |
577 | free allocated storage. */ | |
6de9cd9a | 578 | |
0bca51f0 DN |
579 | static void |
580 | ccp_finalize (void) | |
6de9cd9a | 581 | { |
0bca51f0 DN |
582 | /* Perform substitutions based on the known constant values. */ |
583 | substitute_and_fold (const_val); | |
6de9cd9a | 584 | |
0bca51f0 | 585 | free (const_val); |
6de9cd9a DN |
586 | } |
587 | ||
588 | ||
0bca51f0 DN |
589 | /* Compute the meet operator between *VAL1 and *VAL2. Store the result |
590 | in VAL1. | |
591 | ||
592 | any M UNDEFINED = any | |
593 | any M UNKNOWN_VAL = UNKNOWN_VAL | |
594 | any M VARYING = VARYING | |
595 | Ci M Cj = Ci if (i == j) | |
596 | Ci M Cj = VARYING if (i != j) | |
597 | ||
598 | Lattice values UNKNOWN_VAL and UNDEFINED are similar but have | |
599 | different semantics at PHI nodes. Both values imply that we don't | |
600 | know whether the variable is constant or not. However, UNKNOWN_VAL | |
601 | values override all others. For instance, suppose that A is a | |
602 | global variable: | |
603 | ||
604 | +------+ | |
605 | | | | |
606 | | / \ | |
607 | | / \ | |
608 | | | A_1 = 4 | |
609 | | \ / | |
610 | | \ / | |
611 | | A_3 = PHI (A_2, A_1) | |
612 | | ... = A_3 | |
613 | | | | |
614 | +----+ | |
615 | ||
616 | If the edge into A_2 is not executable, the first visit to A_3 will | |
617 | yield the constant 4. But the second visit to A_3 will be with A_2 | |
618 | in state UNKNOWN_VAL. We can no longer conclude that A_3 is 4 | |
619 | because A_2 may have been set in another function. If we had used | |
620 | the lattice value UNDEFINED, we would have had wrongly concluded | |
621 | that A_3 is 4. */ | |
622 | ||
6de9cd9a DN |
623 | |
624 | static void | |
0bca51f0 | 625 | ccp_lattice_meet (prop_value_t *val1, prop_value_t *val2) |
6de9cd9a | 626 | { |
0bca51f0 | 627 | if (val1->lattice_val == UNDEFINED) |
6de9cd9a | 628 | { |
0bca51f0 DN |
629 | /* UNDEFINED M any = any */ |
630 | *val1 = *val2; | |
750628d8 | 631 | } |
0bca51f0 | 632 | else if (val2->lattice_val == UNDEFINED) |
195da47b | 633 | { |
0bca51f0 DN |
634 | /* any M UNDEFINED = any |
635 | Nothing to do. VAL1 already contains the value we want. */ | |
636 | ; | |
195da47b | 637 | } |
0bca51f0 DN |
638 | else if (val1->lattice_val == UNKNOWN_VAL |
639 | || val2->lattice_val == UNKNOWN_VAL) | |
6de9cd9a | 640 | { |
0bca51f0 DN |
641 | /* UNKNOWN_VAL values are invalid if we are not doing STORE-CCP. */ |
642 | gcc_assert (do_store_ccp); | |
6de9cd9a | 643 | |
0bca51f0 DN |
644 | /* any M UNKNOWN_VAL = UNKNOWN_VAL. */ |
645 | val1->lattice_val = UNKNOWN_VAL; | |
646 | val1->value = NULL_TREE; | |
647 | val1->mem_ref = NULL_TREE; | |
648 | } | |
649 | else if (val1->lattice_val == VARYING | |
650 | || val2->lattice_val == VARYING) | |
750628d8 | 651 | { |
0bca51f0 DN |
652 | /* any M VARYING = VARYING. */ |
653 | val1->lattice_val = VARYING; | |
654 | val1->value = NULL_TREE; | |
655 | val1->mem_ref = NULL_TREE; | |
750628d8 | 656 | } |
0bca51f0 DN |
657 | else if (val1->lattice_val == CONSTANT |
658 | && val2->lattice_val == CONSTANT | |
659 | && simple_cst_equal (val1->value, val2->value) == 1 | |
660 | && (!do_store_ccp | |
661 | || simple_cst_equal (val1->mem_ref, val2->mem_ref) == 1)) | |
750628d8 | 662 | { |
0bca51f0 DN |
663 | /* Ci M Cj = Ci if (i == j) |
664 | Ci M Cj = VARYING if (i != j) | |
665 | ||
666 | If these two values come from memory stores, make sure that | |
667 | they come from the same memory reference. */ | |
668 | val1->lattice_val = CONSTANT; | |
669 | val1->value = val1->value; | |
670 | val1->mem_ref = val1->mem_ref; | |
750628d8 DN |
671 | } |
672 | else | |
673 | { | |
0bca51f0 DN |
674 | /* Any other combination is VARYING. */ |
675 | val1->lattice_val = VARYING; | |
676 | val1->value = NULL_TREE; | |
677 | val1->mem_ref = NULL_TREE; | |
750628d8 | 678 | } |
6de9cd9a DN |
679 | } |
680 | ||
681 | ||
750628d8 DN |
682 | /* Loop through the PHI_NODE's parameters for BLOCK and compare their |
683 | lattice values to determine PHI_NODE's lattice value. The value of a | |
0bca51f0 | 684 | PHI node is determined calling ccp_lattice_meet with all the arguments |
750628d8 | 685 | of the PHI node that are incoming via executable edges. */ |
6de9cd9a | 686 | |
750628d8 DN |
687 | static enum ssa_prop_result |
688 | ccp_visit_phi_node (tree phi) | |
6de9cd9a | 689 | { |
750628d8 | 690 | int i; |
0bca51f0 | 691 | prop_value_t *old_val, new_val; |
6de9cd9a | 692 | |
750628d8 | 693 | if (dump_file && (dump_flags & TDF_DETAILS)) |
6de9cd9a | 694 | { |
750628d8 DN |
695 | fprintf (dump_file, "\nVisiting PHI node: "); |
696 | print_generic_expr (dump_file, phi, dump_flags); | |
6de9cd9a | 697 | } |
6de9cd9a | 698 | |
0bca51f0 | 699 | old_val = get_value (PHI_RESULT (phi), false); |
750628d8 DN |
700 | switch (old_val->lattice_val) |
701 | { | |
702 | case VARYING: | |
0bca51f0 | 703 | return SSA_PROP_VARYING; |
6de9cd9a | 704 | |
750628d8 DN |
705 | case CONSTANT: |
706 | new_val = *old_val; | |
707 | break; | |
6de9cd9a | 708 | |
750628d8 DN |
709 | case UNKNOWN_VAL: |
710 | /* To avoid the default value of UNKNOWN_VAL overriding | |
711 | that of its possible constant arguments, temporarily | |
712 | set the PHI node's default lattice value to be | |
713 | UNDEFINED. If the PHI node's old value was UNKNOWN_VAL and | |
714 | the new value is UNDEFINED, then we prevent the invalid | |
715 | transition by not calling set_lattice_value. */ | |
0bca51f0 DN |
716 | gcc_assert (do_store_ccp); |
717 | ||
718 | /* FALLTHRU */ | |
6de9cd9a | 719 | |
750628d8 DN |
720 | case UNDEFINED: |
721 | case UNINITIALIZED: | |
722 | new_val.lattice_val = UNDEFINED; | |
0bca51f0 DN |
723 | new_val.value = NULL_TREE; |
724 | new_val.mem_ref = NULL_TREE; | |
750628d8 | 725 | break; |
6de9cd9a | 726 | |
750628d8 | 727 | default: |
1e128c5f | 728 | gcc_unreachable (); |
750628d8 | 729 | } |
6de9cd9a | 730 | |
750628d8 DN |
731 | for (i = 0; i < PHI_NUM_ARGS (phi); i++) |
732 | { | |
0bca51f0 DN |
733 | /* Compute the meet operator over all the PHI arguments flowing |
734 | through executable edges. */ | |
750628d8 | 735 | edge e = PHI_ARG_EDGE (phi, i); |
6de9cd9a | 736 | |
750628d8 DN |
737 | if (dump_file && (dump_flags & TDF_DETAILS)) |
738 | { | |
739 | fprintf (dump_file, | |
740 | "\n Argument #%d (%d -> %d %sexecutable)\n", | |
741 | i, e->src->index, e->dest->index, | |
742 | (e->flags & EDGE_EXECUTABLE) ? "" : "not "); | |
743 | } | |
744 | ||
745 | /* If the incoming edge is executable, Compute the meet operator for | |
746 | the existing value of the PHI node and the current PHI argument. */ | |
747 | if (e->flags & EDGE_EXECUTABLE) | |
748 | { | |
0bca51f0 DN |
749 | tree arg = PHI_ARG_DEF (phi, i); |
750 | prop_value_t arg_val; | |
6de9cd9a | 751 | |
0bca51f0 | 752 | if (is_gimple_min_invariant (arg)) |
750628d8 | 753 | { |
0bca51f0 DN |
754 | arg_val.lattice_val = CONSTANT; |
755 | arg_val.value = arg; | |
756 | arg_val.mem_ref = NULL_TREE; | |
750628d8 DN |
757 | } |
758 | else | |
0bca51f0 | 759 | arg_val = *(get_value (arg, true)); |
6de9cd9a | 760 | |
0bca51f0 | 761 | ccp_lattice_meet (&new_val, &arg_val); |
6de9cd9a | 762 | |
750628d8 DN |
763 | if (dump_file && (dump_flags & TDF_DETAILS)) |
764 | { | |
765 | fprintf (dump_file, "\t"); | |
0bca51f0 DN |
766 | print_generic_expr (dump_file, arg, dump_flags); |
767 | dump_lattice_value (dump_file, "\tValue: ", arg_val); | |
750628d8 DN |
768 | fprintf (dump_file, "\n"); |
769 | } | |
6de9cd9a | 770 | |
750628d8 DN |
771 | if (new_val.lattice_val == VARYING) |
772 | break; | |
773 | } | |
774 | } | |
6de9cd9a DN |
775 | |
776 | if (dump_file && (dump_flags & TDF_DETAILS)) | |
750628d8 DN |
777 | { |
778 | dump_lattice_value (dump_file, "\n PHI node value: ", new_val); | |
779 | fprintf (dump_file, "\n\n"); | |
780 | } | |
781 | ||
8c27b7d4 | 782 | /* Check for an invalid change from UNKNOWN_VAL to UNDEFINED. */ |
0bca51f0 DN |
783 | if (do_store_ccp |
784 | && old_val->lattice_val == UNKNOWN_VAL | |
750628d8 DN |
785 | && new_val.lattice_val == UNDEFINED) |
786 | return SSA_PROP_NOT_INTERESTING; | |
787 | ||
788 | /* Otherwise, make the transition to the new value. */ | |
789 | if (set_lattice_value (PHI_RESULT (phi), new_val)) | |
790 | { | |
791 | if (new_val.lattice_val == VARYING) | |
792 | return SSA_PROP_VARYING; | |
793 | else | |
794 | return SSA_PROP_INTERESTING; | |
795 | } | |
796 | else | |
797 | return SSA_PROP_NOT_INTERESTING; | |
6de9cd9a DN |
798 | } |
799 | ||
800 | ||
750628d8 DN |
801 | /* CCP specific front-end to the non-destructive constant folding |
802 | routines. | |
6de9cd9a DN |
803 | |
804 | Attempt to simplify the RHS of STMT knowing that one or more | |
805 | operands are constants. | |
806 | ||
807 | If simplification is possible, return the simplified RHS, | |
808 | otherwise return the original RHS. */ | |
809 | ||
810 | static tree | |
811 | ccp_fold (tree stmt) | |
812 | { | |
813 | tree rhs = get_rhs (stmt); | |
814 | enum tree_code code = TREE_CODE (rhs); | |
6615c446 | 815 | enum tree_code_class kind = TREE_CODE_CLASS (code); |
6de9cd9a DN |
816 | tree retval = NULL_TREE; |
817 | ||
6de9cd9a | 818 | if (TREE_CODE (rhs) == SSA_NAME) |
0bca51f0 DN |
819 | { |
820 | /* If the RHS is an SSA_NAME, return its known constant value, | |
821 | if any. */ | |
822 | return get_value (rhs, true)->value; | |
823 | } | |
824 | else if (do_store_ccp && stmt_makes_single_load (stmt)) | |
825 | { | |
826 | /* If the RHS is a memory load, see if the VUSEs associated with | |
827 | it are a valid constant for that memory load. */ | |
828 | prop_value_t *val = get_value_loaded_by (stmt, const_val); | |
829 | if (val && simple_cst_equal (val->mem_ref, rhs) == 1) | |
830 | return val->value; | |
831 | else | |
832 | return NULL_TREE; | |
833 | } | |
6de9cd9a DN |
834 | |
835 | /* Unary operators. Note that we know the single operand must | |
836 | be a constant. So this should almost always return a | |
837 | simplified RHS. */ | |
6615c446 | 838 | if (kind == tcc_unary) |
6de9cd9a DN |
839 | { |
840 | /* Handle unary operators which can appear in GIMPLE form. */ | |
841 | tree op0 = TREE_OPERAND (rhs, 0); | |
842 | ||
843 | /* Simplify the operand down to a constant. */ | |
844 | if (TREE_CODE (op0) == SSA_NAME) | |
845 | { | |
0bca51f0 | 846 | prop_value_t *val = get_value (op0, true); |
6de9cd9a | 847 | if (val->lattice_val == CONSTANT) |
0bca51f0 | 848 | op0 = get_value (op0, true)->value; |
6de9cd9a DN |
849 | } |
850 | ||
b52d5eaa | 851 | retval = fold_unary_to_constant (code, TREE_TYPE (rhs), op0); |
6de9cd9a DN |
852 | |
853 | /* If we folded, but did not create an invariant, then we can not | |
854 | use this expression. */ | |
855 | if (retval && ! is_gimple_min_invariant (retval)) | |
856 | return NULL; | |
857 | ||
858 | /* If we could not fold the expression, but the arguments are all | |
859 | constants and gimple values, then build and return the new | |
860 | expression. | |
861 | ||
862 | In some cases the new expression is still something we can | |
863 | use as a replacement for an argument. This happens with | |
864 | NOP conversions of types for example. | |
865 | ||
866 | In other cases the new expression can not be used as a | |
867 | replacement for an argument (as it would create non-gimple | |
868 | code). But the new expression can still be used to derive | |
869 | other constants. */ | |
870 | if (! retval && is_gimple_min_invariant (op0)) | |
871 | return build1 (code, TREE_TYPE (rhs), op0); | |
872 | } | |
873 | ||
874 | /* Binary and comparison operators. We know one or both of the | |
875 | operands are constants. */ | |
6615c446 JO |
876 | else if (kind == tcc_binary |
877 | || kind == tcc_comparison | |
6de9cd9a DN |
878 | || code == TRUTH_AND_EXPR |
879 | || code == TRUTH_OR_EXPR | |
880 | || code == TRUTH_XOR_EXPR) | |
881 | { | |
882 | /* Handle binary and comparison operators that can appear in | |
883 | GIMPLE form. */ | |
884 | tree op0 = TREE_OPERAND (rhs, 0); | |
885 | tree op1 = TREE_OPERAND (rhs, 1); | |
886 | ||
887 | /* Simplify the operands down to constants when appropriate. */ | |
888 | if (TREE_CODE (op0) == SSA_NAME) | |
889 | { | |
0bca51f0 | 890 | prop_value_t *val = get_value (op0, true); |
6de9cd9a | 891 | if (val->lattice_val == CONSTANT) |
0bca51f0 | 892 | op0 = val->value; |
6de9cd9a DN |
893 | } |
894 | ||
895 | if (TREE_CODE (op1) == SSA_NAME) | |
896 | { | |
0bca51f0 | 897 | prop_value_t *val = get_value (op1, true); |
6de9cd9a | 898 | if (val->lattice_val == CONSTANT) |
0bca51f0 | 899 | op1 = val->value; |
6de9cd9a DN |
900 | } |
901 | ||
b52d5eaa | 902 | retval = fold_binary_to_constant (code, TREE_TYPE (rhs), op0, op1); |
6de9cd9a DN |
903 | |
904 | /* If we folded, but did not create an invariant, then we can not | |
905 | use this expression. */ | |
906 | if (retval && ! is_gimple_min_invariant (retval)) | |
907 | return NULL; | |
908 | ||
909 | /* If we could not fold the expression, but the arguments are all | |
910 | constants and gimple values, then build and return the new | |
911 | expression. | |
912 | ||
913 | In some cases the new expression is still something we can | |
914 | use as a replacement for an argument. This happens with | |
915 | NOP conversions of types for example. | |
916 | ||
917 | In other cases the new expression can not be used as a | |
918 | replacement for an argument (as it would create non-gimple | |
919 | code). But the new expression can still be used to derive | |
920 | other constants. */ | |
921 | if (! retval | |
922 | && is_gimple_min_invariant (op0) | |
923 | && is_gimple_min_invariant (op1)) | |
924 | return build (code, TREE_TYPE (rhs), op0, op1); | |
925 | } | |
926 | ||
927 | /* We may be able to fold away calls to builtin functions if their | |
9cf737f8 | 928 | arguments are constants. */ |
6de9cd9a DN |
929 | else if (code == CALL_EXPR |
930 | && TREE_CODE (TREE_OPERAND (rhs, 0)) == ADDR_EXPR | |
931 | && (TREE_CODE (TREE_OPERAND (TREE_OPERAND (rhs, 0), 0)) | |
932 | == FUNCTION_DECL) | |
933 | && DECL_BUILT_IN (TREE_OPERAND (TREE_OPERAND (rhs, 0), 0))) | |
934 | { | |
f47c96aa | 935 | if (!ZERO_SSA_OPERANDS (stmt, SSA_OP_USE)) |
6de9cd9a | 936 | { |
f47c96aa | 937 | tree *orig, var; |
49d1af89 | 938 | tree fndecl, arglist; |
f47c96aa AM |
939 | size_t i = 0; |
940 | ssa_op_iter iter; | |
941 | use_operand_p var_p; | |
6de9cd9a DN |
942 | |
943 | /* Preserve the original values of every operand. */ | |
f47c96aa AM |
944 | orig = xmalloc (sizeof (tree) * NUM_SSA_OPERANDS (stmt, SSA_OP_USE)); |
945 | FOR_EACH_SSA_TREE_OPERAND (var, stmt, iter, SSA_OP_USE) | |
946 | orig[i++] = var; | |
6de9cd9a DN |
947 | |
948 | /* Substitute operands with their values and try to fold. */ | |
0bca51f0 | 949 | replace_uses_in (stmt, NULL, const_val); |
49d1af89 KH |
950 | fndecl = get_callee_fndecl (rhs); |
951 | arglist = TREE_OPERAND (rhs, 1); | |
952 | retval = fold_builtin (fndecl, arglist, false); | |
6de9cd9a DN |
953 | |
954 | /* Restore operands to their original form. */ | |
f47c96aa AM |
955 | i = 0; |
956 | FOR_EACH_SSA_USE_OPERAND (var_p, stmt, iter, SSA_OP_USE) | |
957 | SET_USE (var_p, orig[i++]); | |
6de9cd9a DN |
958 | free (orig); |
959 | } | |
960 | } | |
961 | else | |
962 | return rhs; | |
963 | ||
964 | /* If we got a simplified form, see if we need to convert its type. */ | |
965 | if (retval) | |
a32e70c3 | 966 | return fold_convert (TREE_TYPE (rhs), retval); |
6de9cd9a DN |
967 | |
968 | /* No simplification was possible. */ | |
969 | return rhs; | |
970 | } | |
971 | ||
972 | ||
973 | /* Evaluate statement STMT. */ | |
974 | ||
0bca51f0 | 975 | static prop_value_t |
6de9cd9a DN |
976 | evaluate_stmt (tree stmt) |
977 | { | |
0bca51f0 | 978 | prop_value_t val; |
6de9cd9a | 979 | tree simplified; |
0bca51f0 DN |
980 | ccp_lattice_t likelyvalue = likely_value (stmt); |
981 | ||
982 | val.mem_ref = NULL_TREE; | |
6de9cd9a DN |
983 | |
984 | /* If the statement is likely to have a CONSTANT result, then try | |
985 | to fold the statement to determine the constant value. */ | |
986 | if (likelyvalue == CONSTANT) | |
987 | simplified = ccp_fold (stmt); | |
988 | /* If the statement is likely to have a VARYING result, then do not | |
989 | bother folding the statement. */ | |
990 | else if (likelyvalue == VARYING) | |
991 | simplified = get_rhs (stmt); | |
992 | /* Otherwise the statement is likely to have an UNDEFINED value and | |
993 | there will be nothing to do. */ | |
994 | else | |
995 | simplified = NULL_TREE; | |
996 | ||
997 | if (simplified && is_gimple_min_invariant (simplified)) | |
998 | { | |
999 | /* The statement produced a constant value. */ | |
1000 | val.lattice_val = CONSTANT; | |
0bca51f0 | 1001 | val.value = simplified; |
6de9cd9a DN |
1002 | } |
1003 | else | |
1004 | { | |
1005 | /* The statement produced a nonconstant value. If the statement | |
0bca51f0 DN |
1006 | had UNDEFINED operands, then the result of the statement |
1007 | should be UNDEFINED. Otherwise, the statement is VARYING. */ | |
1008 | val.lattice_val = (likelyvalue == UNDEFINED) ? UNDEFINED : VARYING; | |
1009 | val.value = NULL_TREE; | |
6de9cd9a | 1010 | } |
750628d8 DN |
1011 | |
1012 | return val; | |
6de9cd9a DN |
1013 | } |
1014 | ||
1015 | ||
750628d8 | 1016 | /* Visit the assignment statement STMT. Set the value of its LHS to the |
0bca51f0 DN |
1017 | value computed by the RHS and store LHS in *OUTPUT_P. If STMT |
1018 | creates virtual definitions, set the value of each new name to that | |
1019 | of the RHS (if we can derive a constant out of the RHS). */ | |
6de9cd9a | 1020 | |
750628d8 DN |
1021 | static enum ssa_prop_result |
1022 | visit_assignment (tree stmt, tree *output_p) | |
6de9cd9a | 1023 | { |
0bca51f0 | 1024 | prop_value_t val; |
750628d8 | 1025 | tree lhs, rhs; |
0bca51f0 | 1026 | enum ssa_prop_result retval; |
6de9cd9a | 1027 | |
750628d8 DN |
1028 | lhs = TREE_OPERAND (stmt, 0); |
1029 | rhs = TREE_OPERAND (stmt, 1); | |
6de9cd9a | 1030 | |
750628d8 DN |
1031 | if (TREE_CODE (rhs) == SSA_NAME) |
1032 | { | |
1033 | /* For a simple copy operation, we copy the lattice values. */ | |
0bca51f0 | 1034 | prop_value_t *nval = get_value (rhs, true); |
750628d8 DN |
1035 | val = *nval; |
1036 | } | |
0bca51f0 | 1037 | else if (do_store_ccp && stmt_makes_single_load (stmt)) |
750628d8 | 1038 | { |
0bca51f0 DN |
1039 | /* Same as above, but the RHS is not a gimple register and yet |
1040 | has a known VUSE. If STMT is loading from the same memory | |
1041 | location that created the SSA_NAMEs for the virtual operands, | |
1042 | we can propagate the value on the RHS. */ | |
1043 | prop_value_t *nval = get_value_loaded_by (stmt, const_val); | |
1044 | ||
1045 | if (nval && simple_cst_equal (nval->mem_ref, rhs) == 1) | |
1046 | val = *nval; | |
1047 | else | |
1048 | val = evaluate_stmt (stmt); | |
750628d8 DN |
1049 | } |
1050 | else | |
9390c347 | 1051 | /* Evaluate the statement. */ |
750628d8 | 1052 | val = evaluate_stmt (stmt); |
6de9cd9a | 1053 | |
9390c347 | 1054 | /* If the original LHS was a VIEW_CONVERT_EXPR, modify the constant |
ae95537a | 1055 | value to be a VIEW_CONVERT_EXPR of the old constant value. |
9390c347 RK |
1056 | |
1057 | ??? Also, if this was a definition of a bitfield, we need to widen | |
750628d8 DN |
1058 | the constant value into the type of the destination variable. This |
1059 | should not be necessary if GCC represented bitfields properly. */ | |
1060 | { | |
9390c347 RK |
1061 | tree orig_lhs = TREE_OPERAND (stmt, 0); |
1062 | ||
1063 | if (TREE_CODE (orig_lhs) == VIEW_CONVERT_EXPR | |
1064 | && val.lattice_val == CONSTANT) | |
1065 | { | |
ae95537a RK |
1066 | tree w = fold (build1 (VIEW_CONVERT_EXPR, |
1067 | TREE_TYPE (TREE_OPERAND (orig_lhs, 0)), | |
0bca51f0 | 1068 | val.value)); |
ae95537a | 1069 | |
3d36fb45 | 1070 | orig_lhs = TREE_OPERAND (orig_lhs, 0); |
ae95537a | 1071 | if (w && is_gimple_min_invariant (w)) |
0bca51f0 | 1072 | val.value = w; |
ae95537a RK |
1073 | else |
1074 | { | |
1075 | val.lattice_val = VARYING; | |
0bca51f0 | 1076 | val.value = NULL; |
ae95537a | 1077 | } |
9390c347 RK |
1078 | } |
1079 | ||
750628d8 | 1080 | if (val.lattice_val == CONSTANT |
9390c347 RK |
1081 | && TREE_CODE (orig_lhs) == COMPONENT_REF |
1082 | && DECL_BIT_FIELD (TREE_OPERAND (orig_lhs, 1))) | |
6de9cd9a | 1083 | { |
0bca51f0 | 1084 | tree w = widen_bitfield (val.value, TREE_OPERAND (orig_lhs, 1), |
9390c347 | 1085 | orig_lhs); |
750628d8 DN |
1086 | |
1087 | if (w && is_gimple_min_invariant (w)) | |
0bca51f0 | 1088 | val.value = w; |
750628d8 | 1089 | else |
6de9cd9a | 1090 | { |
750628d8 | 1091 | val.lattice_val = VARYING; |
0bca51f0 DN |
1092 | val.value = NULL_TREE; |
1093 | val.mem_ref = NULL_TREE; | |
6de9cd9a | 1094 | } |
6de9cd9a | 1095 | } |
750628d8 | 1096 | } |
6de9cd9a | 1097 | |
0bca51f0 | 1098 | retval = SSA_PROP_NOT_INTERESTING; |
6de9cd9a | 1099 | |
750628d8 | 1100 | /* Set the lattice value of the statement's output. */ |
0bca51f0 | 1101 | if (TREE_CODE (lhs) == SSA_NAME) |
6de9cd9a | 1102 | { |
0bca51f0 DN |
1103 | /* If STMT is an assignment to an SSA_NAME, we only have one |
1104 | value to set. */ | |
1105 | if (set_lattice_value (lhs, val)) | |
1106 | { | |
1107 | *output_p = lhs; | |
1108 | if (val.lattice_val == VARYING) | |
1109 | retval = SSA_PROP_VARYING; | |
1110 | else | |
1111 | retval = SSA_PROP_INTERESTING; | |
1112 | } | |
6de9cd9a | 1113 | } |
0bca51f0 DN |
1114 | else if (do_store_ccp && stmt_makes_single_store (stmt)) |
1115 | { | |
1116 | /* Otherwise, set the names in V_MAY_DEF/V_MUST_DEF operands | |
1117 | to the new constant value and mark the LHS as the memory | |
1118 | reference associated with VAL. */ | |
1119 | ssa_op_iter i; | |
1120 | tree vdef; | |
1121 | bool changed; | |
1122 | ||
1123 | /* Stores cannot take on an UNDEFINED value. */ | |
1124 | if (val.lattice_val == UNDEFINED) | |
1125 | val.lattice_val = UNKNOWN_VAL; | |
1126 | ||
1127 | /* Mark VAL as stored in the LHS of this assignment. */ | |
1128 | val.mem_ref = lhs; | |
1129 | ||
1130 | /* Set the value of every VDEF to VAL. */ | |
1131 | changed = false; | |
1132 | FOR_EACH_SSA_TREE_OPERAND (vdef, stmt, i, SSA_OP_VIRTUAL_DEFS) | |
1133 | changed |= set_lattice_value (vdef, val); | |
1134 | ||
1135 | /* Note that for propagation purposes, we are only interested in | |
1136 | visiting statements that load the exact same memory reference | |
1137 | stored here. Those statements will have the exact same list | |
1138 | of virtual uses, so it is enough to set the output of this | |
1139 | statement to be its first virtual definition. */ | |
1140 | *output_p = first_vdef (stmt); | |
1141 | if (changed) | |
1142 | { | |
1143 | if (val.lattice_val == VARYING) | |
1144 | retval = SSA_PROP_VARYING; | |
1145 | else | |
1146 | retval = SSA_PROP_INTERESTING; | |
1147 | } | |
1148 | } | |
1149 | ||
1150 | return retval; | |
6de9cd9a DN |
1151 | } |
1152 | ||
6de9cd9a | 1153 | |
750628d8 DN |
1154 | /* Visit the conditional statement STMT. Return SSA_PROP_INTERESTING |
1155 | if it can determine which edge will be taken. Otherwise, return | |
1156 | SSA_PROP_VARYING. */ | |
1157 | ||
1158 | static enum ssa_prop_result | |
1159 | visit_cond_stmt (tree stmt, edge *taken_edge_p) | |
6de9cd9a | 1160 | { |
0bca51f0 | 1161 | prop_value_t val; |
750628d8 DN |
1162 | basic_block block; |
1163 | ||
1164 | block = bb_for_stmt (stmt); | |
1165 | val = evaluate_stmt (stmt); | |
1166 | ||
1167 | /* Find which edge out of the conditional block will be taken and add it | |
1168 | to the worklist. If no single edge can be determined statically, | |
1169 | return SSA_PROP_VARYING to feed all the outgoing edges to the | |
1170 | propagation engine. */ | |
0bca51f0 | 1171 | *taken_edge_p = val.value ? find_taken_edge (block, val.value) : 0; |
750628d8 DN |
1172 | if (*taken_edge_p) |
1173 | return SSA_PROP_INTERESTING; | |
1174 | else | |
1175 | return SSA_PROP_VARYING; | |
6de9cd9a DN |
1176 | } |
1177 | ||
6de9cd9a | 1178 | |
750628d8 DN |
1179 | /* Evaluate statement STMT. If the statement produces an output value and |
1180 | its evaluation changes the lattice value of its output, return | |
1181 | SSA_PROP_INTERESTING and set *OUTPUT_P to the SSA_NAME holding the | |
1182 | output value. | |
1183 | ||
1184 | If STMT is a conditional branch and we can determine its truth | |
1185 | value, set *TAKEN_EDGE_P accordingly. If STMT produces a varying | |
1186 | value, return SSA_PROP_VARYING. */ | |
6de9cd9a | 1187 | |
750628d8 DN |
1188 | static enum ssa_prop_result |
1189 | ccp_visit_stmt (tree stmt, edge *taken_edge_p, tree *output_p) | |
1190 | { | |
750628d8 DN |
1191 | tree def; |
1192 | ssa_op_iter iter; | |
6de9cd9a | 1193 | |
750628d8 | 1194 | if (dump_file && (dump_flags & TDF_DETAILS)) |
6de9cd9a | 1195 | { |
0bca51f0 DN |
1196 | fprintf (dump_file, "\nVisiting statement:\n"); |
1197 | print_generic_stmt (dump_file, stmt, dump_flags); | |
750628d8 | 1198 | fprintf (dump_file, "\n"); |
6de9cd9a | 1199 | } |
6de9cd9a | 1200 | |
0bca51f0 | 1201 | if (TREE_CODE (stmt) == MODIFY_EXPR) |
6de9cd9a | 1202 | { |
750628d8 DN |
1203 | /* If the statement is an assignment that produces a single |
1204 | output value, evaluate its RHS to see if the lattice value of | |
1205 | its output has changed. */ | |
1206 | return visit_assignment (stmt, output_p); | |
6de9cd9a | 1207 | } |
750628d8 | 1208 | else if (TREE_CODE (stmt) == COND_EXPR || TREE_CODE (stmt) == SWITCH_EXPR) |
6de9cd9a | 1209 | { |
750628d8 DN |
1210 | /* If STMT is a conditional branch, see if we can determine |
1211 | which branch will be taken. */ | |
1212 | return visit_cond_stmt (stmt, taken_edge_p); | |
6de9cd9a | 1213 | } |
6de9cd9a | 1214 | |
750628d8 DN |
1215 | /* Any other kind of statement is not interesting for constant |
1216 | propagation and, therefore, not worth simulating. */ | |
750628d8 DN |
1217 | if (dump_file && (dump_flags & TDF_DETAILS)) |
1218 | fprintf (dump_file, "No interesting values produced. Marked VARYING.\n"); | |
6de9cd9a | 1219 | |
750628d8 DN |
1220 | /* Definitions made by statements other than assignments to |
1221 | SSA_NAMEs represent unknown modifications to their outputs. | |
1222 | Mark them VARYING. */ | |
0bca51f0 DN |
1223 | FOR_EACH_SSA_TREE_OPERAND (def, stmt, iter, SSA_OP_ALL_DEFS) |
1224 | { | |
1225 | prop_value_t v = { VARYING, NULL_TREE, NULL_TREE }; | |
1226 | set_lattice_value (def, v); | |
1227 | } | |
6de9cd9a | 1228 | |
750628d8 DN |
1229 | return SSA_PROP_VARYING; |
1230 | } | |
6de9cd9a | 1231 | |
6de9cd9a | 1232 | |
0bca51f0 | 1233 | /* Main entry point for SSA Conditional Constant Propagation. */ |
750628d8 DN |
1234 | |
1235 | static void | |
0bca51f0 | 1236 | execute_ssa_ccp (bool store_ccp) |
750628d8 | 1237 | { |
0bca51f0 | 1238 | do_store_ccp = store_ccp; |
750628d8 DN |
1239 | ccp_initialize (); |
1240 | ssa_propagate (ccp_visit_stmt, ccp_visit_phi_node); | |
1241 | ccp_finalize (); | |
6de9cd9a DN |
1242 | } |
1243 | ||
173b818d | 1244 | |
0bca51f0 DN |
1245 | static void |
1246 | do_ssa_ccp (void) | |
1247 | { | |
1248 | execute_ssa_ccp (false); | |
1249 | } | |
1250 | ||
1251 | ||
173b818d | 1252 | static bool |
750628d8 | 1253 | gate_ccp (void) |
173b818d | 1254 | { |
750628d8 | 1255 | return flag_tree_ccp != 0; |
173b818d BB |
1256 | } |
1257 | ||
6de9cd9a | 1258 | |
750628d8 DN |
1259 | struct tree_opt_pass pass_ccp = |
1260 | { | |
1261 | "ccp", /* name */ | |
1262 | gate_ccp, /* gate */ | |
0bca51f0 | 1263 | do_ssa_ccp, /* execute */ |
750628d8 DN |
1264 | NULL, /* sub */ |
1265 | NULL, /* next */ | |
1266 | 0, /* static_pass_number */ | |
1267 | TV_TREE_CCP, /* tv_id */ | |
1268 | PROP_cfg | PROP_ssa | PROP_alias, /* properties_required */ | |
1269 | 0, /* properties_provided */ | |
1270 | 0, /* properties_destroyed */ | |
1271 | 0, /* todo_flags_start */ | |
0bca51f0 | 1272 | TODO_cleanup_cfg | TODO_dump_func | TODO_update_ssa |
750628d8 | 1273 | | TODO_ggc_collect | TODO_verify_ssa |
9f8628ba PB |
1274 | | TODO_verify_stmts, /* todo_flags_finish */ |
1275 | 0 /* letter */ | |
750628d8 | 1276 | }; |
6de9cd9a | 1277 | |
6de9cd9a | 1278 | |
0bca51f0 DN |
1279 | static void |
1280 | do_ssa_store_ccp (void) | |
1281 | { | |
1282 | /* If STORE-CCP is not enabled, we just run regular CCP. */ | |
1283 | execute_ssa_ccp (flag_tree_store_ccp != 0); | |
1284 | } | |
1285 | ||
1286 | static bool | |
1287 | gate_store_ccp (void) | |
1288 | { | |
1289 | /* STORE-CCP is enabled only with -ftree-store-ccp, but when | |
1290 | -fno-tree-store-ccp is specified, we should run regular CCP. | |
1291 | That's why the pass is enabled with either flag. */ | |
1292 | return flag_tree_store_ccp != 0 || flag_tree_ccp != 0; | |
1293 | } | |
1294 | ||
1295 | ||
1296 | struct tree_opt_pass pass_store_ccp = | |
1297 | { | |
1298 | "store_ccp", /* name */ | |
1299 | gate_store_ccp, /* gate */ | |
1300 | do_ssa_store_ccp, /* execute */ | |
1301 | NULL, /* sub */ | |
1302 | NULL, /* next */ | |
1303 | 0, /* static_pass_number */ | |
1304 | TV_TREE_STORE_CCP, /* tv_id */ | |
1305 | PROP_cfg | PROP_ssa | PROP_alias, /* properties_required */ | |
1306 | 0, /* properties_provided */ | |
1307 | 0, /* properties_destroyed */ | |
1308 | 0, /* todo_flags_start */ | |
1309 | TODO_dump_func | TODO_update_ssa | |
1310 | | TODO_ggc_collect | TODO_verify_ssa | |
1311 | | TODO_cleanup_cfg | |
1312 | | TODO_verify_stmts, /* todo_flags_finish */ | |
1313 | 0 /* letter */ | |
1314 | }; | |
1315 | ||
750628d8 DN |
1316 | /* Given a constant value VAL for bitfield FIELD, and a destination |
1317 | variable VAR, return VAL appropriately widened to fit into VAR. If | |
1318 | FIELD is wider than HOST_WIDE_INT, NULL is returned. */ | |
6de9cd9a | 1319 | |
750628d8 DN |
1320 | tree |
1321 | widen_bitfield (tree val, tree field, tree var) | |
6de9cd9a | 1322 | { |
750628d8 DN |
1323 | unsigned HOST_WIDE_INT var_size, field_size; |
1324 | tree wide_val; | |
1325 | unsigned HOST_WIDE_INT mask; | |
1326 | unsigned int i; | |
6de9cd9a | 1327 | |
750628d8 DN |
1328 | /* We can only do this if the size of the type and field and VAL are |
1329 | all constants representable in HOST_WIDE_INT. */ | |
1330 | if (!host_integerp (TYPE_SIZE (TREE_TYPE (var)), 1) | |
1331 | || !host_integerp (DECL_SIZE (field), 1) | |
1332 | || !host_integerp (val, 0)) | |
1333 | return NULL_TREE; | |
6de9cd9a | 1334 | |
750628d8 DN |
1335 | var_size = tree_low_cst (TYPE_SIZE (TREE_TYPE (var)), 1); |
1336 | field_size = tree_low_cst (DECL_SIZE (field), 1); | |
6de9cd9a | 1337 | |
750628d8 DN |
1338 | /* Give up if either the bitfield or the variable are too wide. */ |
1339 | if (field_size > HOST_BITS_PER_WIDE_INT || var_size > HOST_BITS_PER_WIDE_INT) | |
1340 | return NULL_TREE; | |
6de9cd9a | 1341 | |
1e128c5f | 1342 | gcc_assert (var_size >= field_size); |
6de9cd9a | 1343 | |
750628d8 DN |
1344 | /* If the sign bit of the value is not set or the field's type is unsigned, |
1345 | just mask off the high order bits of the value. */ | |
1346 | if (DECL_UNSIGNED (field) | |
1347 | || !(tree_low_cst (val, 0) & (((HOST_WIDE_INT)1) << (field_size - 1)))) | |
1348 | { | |
1349 | /* Zero extension. Build a mask with the lower 'field_size' bits | |
1350 | set and a BIT_AND_EXPR node to clear the high order bits of | |
1351 | the value. */ | |
1352 | for (i = 0, mask = 0; i < field_size; i++) | |
1353 | mask |= ((HOST_WIDE_INT) 1) << i; | |
6de9cd9a | 1354 | |
5ff489f1 JM |
1355 | wide_val = build2 (BIT_AND_EXPR, TREE_TYPE (var), val, |
1356 | build_int_cst (TREE_TYPE (var), mask)); | |
6de9cd9a | 1357 | } |
750628d8 | 1358 | else |
173b818d | 1359 | { |
750628d8 DN |
1360 | /* Sign extension. Create a mask with the upper 'field_size' |
1361 | bits set and a BIT_IOR_EXPR to set the high order bits of the | |
1362 | value. */ | |
1363 | for (i = 0, mask = 0; i < (var_size - field_size); i++) | |
1364 | mask |= ((HOST_WIDE_INT) 1) << (var_size - i - 1); | |
1365 | ||
5ff489f1 JM |
1366 | wide_val = build2 (BIT_IOR_EXPR, TREE_TYPE (var), val, |
1367 | build_int_cst (TREE_TYPE (var), mask)); | |
173b818d | 1368 | } |
6de9cd9a | 1369 | |
750628d8 | 1370 | return fold (wide_val); |
6de9cd9a DN |
1371 | } |
1372 | ||
750628d8 | 1373 | |
6de9cd9a DN |
1374 | /* A subroutine of fold_stmt_r. Attempts to fold *(A+O) to A[X]. |
1375 | BASE is an array type. OFFSET is a byte displacement. ORIG_TYPE | |
9cf737f8 | 1376 | is the desired result type. */ |
6de9cd9a DN |
1377 | |
1378 | static tree | |
1379 | maybe_fold_offset_to_array_ref (tree base, tree offset, tree orig_type) | |
1380 | { | |
44de5aeb RK |
1381 | tree min_idx, idx, elt_offset = integer_zero_node; |
1382 | tree array_type, elt_type, elt_size; | |
1383 | ||
1384 | /* If BASE is an ARRAY_REF, we can pick up another offset (this time | |
1385 | measured in units of the size of elements type) from that ARRAY_REF). | |
1386 | We can't do anything if either is variable. | |
1387 | ||
1388 | The case we handle here is *(&A[N]+O). */ | |
1389 | if (TREE_CODE (base) == ARRAY_REF) | |
1390 | { | |
1391 | tree low_bound = array_ref_low_bound (base); | |
1392 | ||
1393 | elt_offset = TREE_OPERAND (base, 1); | |
1394 | if (TREE_CODE (low_bound) != INTEGER_CST | |
1395 | || TREE_CODE (elt_offset) != INTEGER_CST) | |
1396 | return NULL_TREE; | |
1397 | ||
1398 | elt_offset = int_const_binop (MINUS_EXPR, elt_offset, low_bound, 0); | |
1399 | base = TREE_OPERAND (base, 0); | |
1400 | } | |
6de9cd9a DN |
1401 | |
1402 | /* Ignore stupid user tricks of indexing non-array variables. */ | |
1403 | array_type = TREE_TYPE (base); | |
1404 | if (TREE_CODE (array_type) != ARRAY_TYPE) | |
1405 | return NULL_TREE; | |
1406 | elt_type = TREE_TYPE (array_type); | |
1407 | if (!lang_hooks.types_compatible_p (orig_type, elt_type)) | |
1408 | return NULL_TREE; | |
1409 | ||
44de5aeb RK |
1410 | /* If OFFSET and ELT_OFFSET are zero, we don't care about the size of the |
1411 | element type (so we can use the alignment if it's not constant). | |
1412 | Otherwise, compute the offset as an index by using a division. If the | |
1413 | division isn't exact, then don't do anything. */ | |
6de9cd9a | 1414 | elt_size = TYPE_SIZE_UNIT (elt_type); |
44de5aeb RK |
1415 | if (integer_zerop (offset)) |
1416 | { | |
1417 | if (TREE_CODE (elt_size) != INTEGER_CST) | |
1418 | elt_size = size_int (TYPE_ALIGN (elt_type)); | |
6de9cd9a | 1419 | |
44de5aeb RK |
1420 | idx = integer_zero_node; |
1421 | } | |
1422 | else | |
1423 | { | |
1424 | unsigned HOST_WIDE_INT lquo, lrem; | |
1425 | HOST_WIDE_INT hquo, hrem; | |
1426 | ||
1427 | if (TREE_CODE (elt_size) != INTEGER_CST | |
1428 | || div_and_round_double (TRUNC_DIV_EXPR, 1, | |
1429 | TREE_INT_CST_LOW (offset), | |
1430 | TREE_INT_CST_HIGH (offset), | |
1431 | TREE_INT_CST_LOW (elt_size), | |
1432 | TREE_INT_CST_HIGH (elt_size), | |
1433 | &lquo, &hquo, &lrem, &hrem) | |
1434 | || lrem || hrem) | |
1435 | return NULL_TREE; | |
6de9cd9a | 1436 | |
7d60be94 | 1437 | idx = build_int_cst_wide (NULL_TREE, lquo, hquo); |
44de5aeb RK |
1438 | } |
1439 | ||
1440 | /* Assume the low bound is zero. If there is a domain type, get the | |
1441 | low bound, if any, convert the index into that type, and add the | |
1442 | low bound. */ | |
1443 | min_idx = integer_zero_node; | |
1444 | if (TYPE_DOMAIN (array_type)) | |
6de9cd9a | 1445 | { |
44de5aeb RK |
1446 | if (TYPE_MIN_VALUE (TYPE_DOMAIN (array_type))) |
1447 | min_idx = TYPE_MIN_VALUE (TYPE_DOMAIN (array_type)); | |
1448 | else | |
1449 | min_idx = fold_convert (TYPE_DOMAIN (array_type), min_idx); | |
1450 | ||
1451 | if (TREE_CODE (min_idx) != INTEGER_CST) | |
1452 | return NULL_TREE; | |
1453 | ||
1454 | idx = fold_convert (TYPE_DOMAIN (array_type), idx); | |
1455 | elt_offset = fold_convert (TYPE_DOMAIN (array_type), elt_offset); | |
6de9cd9a DN |
1456 | } |
1457 | ||
44de5aeb RK |
1458 | if (!integer_zerop (min_idx)) |
1459 | idx = int_const_binop (PLUS_EXPR, idx, min_idx, 0); | |
1460 | if (!integer_zerop (elt_offset)) | |
1461 | idx = int_const_binop (PLUS_EXPR, idx, elt_offset, 0); | |
1462 | ||
1463 | return build (ARRAY_REF, orig_type, base, idx, min_idx, | |
1464 | size_int (tree_low_cst (elt_size, 1) | |
a4e9ffe5 | 1465 | / (TYPE_ALIGN_UNIT (elt_type)))); |
6de9cd9a DN |
1466 | } |
1467 | ||
750628d8 | 1468 | |
6de9cd9a DN |
1469 | /* A subroutine of fold_stmt_r. Attempts to fold *(S+O) to S.X. |
1470 | BASE is a record type. OFFSET is a byte displacement. ORIG_TYPE | |
1471 | is the desired result type. */ | |
1472 | /* ??? This doesn't handle class inheritance. */ | |
1473 | ||
1474 | static tree | |
1475 | maybe_fold_offset_to_component_ref (tree record_type, tree base, tree offset, | |
1476 | tree orig_type, bool base_is_ptr) | |
1477 | { | |
f34fa464 | 1478 | tree f, t, field_type, tail_array_field, field_offset; |
6de9cd9a DN |
1479 | |
1480 | if (TREE_CODE (record_type) != RECORD_TYPE | |
1481 | && TREE_CODE (record_type) != UNION_TYPE | |
1482 | && TREE_CODE (record_type) != QUAL_UNION_TYPE) | |
1483 | return NULL_TREE; | |
1484 | ||
1485 | /* Short-circuit silly cases. */ | |
1486 | if (lang_hooks.types_compatible_p (record_type, orig_type)) | |
1487 | return NULL_TREE; | |
1488 | ||
1489 | tail_array_field = NULL_TREE; | |
1490 | for (f = TYPE_FIELDS (record_type); f ; f = TREE_CHAIN (f)) | |
1491 | { | |
1492 | int cmp; | |
1493 | ||
1494 | if (TREE_CODE (f) != FIELD_DECL) | |
1495 | continue; | |
1496 | if (DECL_BIT_FIELD (f)) | |
1497 | continue; | |
f34fa464 ZD |
1498 | |
1499 | field_offset = byte_position (f); | |
1500 | if (TREE_CODE (field_offset) != INTEGER_CST) | |
6de9cd9a DN |
1501 | continue; |
1502 | ||
1503 | /* ??? Java creates "interesting" fields for representing base classes. | |
1504 | They have no name, and have no context. With no context, we get into | |
1505 | trouble with nonoverlapping_component_refs_p. Skip them. */ | |
1506 | if (!DECL_FIELD_CONTEXT (f)) | |
1507 | continue; | |
1508 | ||
1509 | /* The previous array field isn't at the end. */ | |
1510 | tail_array_field = NULL_TREE; | |
1511 | ||
1512 | /* Check to see if this offset overlaps with the field. */ | |
f34fa464 | 1513 | cmp = tree_int_cst_compare (field_offset, offset); |
6de9cd9a DN |
1514 | if (cmp > 0) |
1515 | continue; | |
1516 | ||
1517 | field_type = TREE_TYPE (f); | |
6de9cd9a DN |
1518 | |
1519 | /* Here we exactly match the offset being checked. If the types match, | |
1520 | then we can return that field. */ | |
53dba802 ZD |
1521 | if (cmp == 0 |
1522 | && lang_hooks.types_compatible_p (orig_type, field_type)) | |
6de9cd9a DN |
1523 | { |
1524 | if (base_is_ptr) | |
1525 | base = build1 (INDIRECT_REF, record_type, base); | |
44de5aeb | 1526 | t = build (COMPONENT_REF, field_type, base, f, NULL_TREE); |
6de9cd9a DN |
1527 | return t; |
1528 | } | |
53dba802 ZD |
1529 | |
1530 | /* Don't care about offsets into the middle of scalars. */ | |
1531 | if (!AGGREGATE_TYPE_P (field_type)) | |
1532 | continue; | |
6de9cd9a | 1533 | |
53dba802 ZD |
1534 | /* Check for array at the end of the struct. This is often |
1535 | used as for flexible array members. We should be able to | |
1536 | turn this into an array access anyway. */ | |
1537 | if (TREE_CODE (field_type) == ARRAY_TYPE) | |
1538 | tail_array_field = f; | |
1539 | ||
1540 | /* Check the end of the field against the offset. */ | |
1541 | if (!DECL_SIZE_UNIT (f) | |
1542 | || TREE_CODE (DECL_SIZE_UNIT (f)) != INTEGER_CST) | |
1543 | continue; | |
1544 | t = int_const_binop (MINUS_EXPR, offset, field_offset, 1); | |
1545 | if (!tree_int_cst_lt (t, DECL_SIZE_UNIT (f))) | |
1546 | continue; | |
6de9cd9a | 1547 | |
53dba802 ZD |
1548 | /* If we matched, then set offset to the displacement into |
1549 | this field. */ | |
1550 | offset = t; | |
6de9cd9a DN |
1551 | goto found; |
1552 | } | |
1553 | ||
1554 | if (!tail_array_field) | |
1555 | return NULL_TREE; | |
1556 | ||
1557 | f = tail_array_field; | |
1558 | field_type = TREE_TYPE (f); | |
53dba802 | 1559 | offset = int_const_binop (MINUS_EXPR, offset, byte_position (f), 1); |
6de9cd9a DN |
1560 | |
1561 | found: | |
1562 | /* If we get here, we've got an aggregate field, and a possibly | |
1ea7e6ad | 1563 | nonzero offset into them. Recurse and hope for a valid match. */ |
6de9cd9a DN |
1564 | if (base_is_ptr) |
1565 | base = build1 (INDIRECT_REF, record_type, base); | |
44de5aeb | 1566 | base = build (COMPONENT_REF, field_type, base, f, NULL_TREE); |
6de9cd9a DN |
1567 | |
1568 | t = maybe_fold_offset_to_array_ref (base, offset, orig_type); | |
1569 | if (t) | |
1570 | return t; | |
1571 | return maybe_fold_offset_to_component_ref (field_type, base, offset, | |
1572 | orig_type, false); | |
1573 | } | |
1574 | ||
750628d8 | 1575 | |
6de9cd9a DN |
1576 | /* A subroutine of fold_stmt_r. Attempt to simplify *(BASE+OFFSET). |
1577 | Return the simplified expression, or NULL if nothing could be done. */ | |
1578 | ||
1579 | static tree | |
1580 | maybe_fold_stmt_indirect (tree expr, tree base, tree offset) | |
1581 | { | |
1582 | tree t; | |
1583 | ||
1584 | /* We may well have constructed a double-nested PLUS_EXPR via multiple | |
1585 | substitutions. Fold that down to one. Remove NON_LVALUE_EXPRs that | |
1586 | are sometimes added. */ | |
1587 | base = fold (base); | |
ff7c8597 | 1588 | STRIP_TYPE_NOPS (base); |
6de9cd9a DN |
1589 | TREE_OPERAND (expr, 0) = base; |
1590 | ||
1591 | /* One possibility is that the address reduces to a string constant. */ | |
1592 | t = fold_read_from_constant_string (expr); | |
1593 | if (t) | |
1594 | return t; | |
1595 | ||
1596 | /* Add in any offset from a PLUS_EXPR. */ | |
1597 | if (TREE_CODE (base) == PLUS_EXPR) | |
1598 | { | |
1599 | tree offset2; | |
1600 | ||
1601 | offset2 = TREE_OPERAND (base, 1); | |
1602 | if (TREE_CODE (offset2) != INTEGER_CST) | |
1603 | return NULL_TREE; | |
1604 | base = TREE_OPERAND (base, 0); | |
1605 | ||
1606 | offset = int_const_binop (PLUS_EXPR, offset, offset2, 1); | |
1607 | } | |
1608 | ||
1609 | if (TREE_CODE (base) == ADDR_EXPR) | |
1610 | { | |
1611 | /* Strip the ADDR_EXPR. */ | |
1612 | base = TREE_OPERAND (base, 0); | |
1613 | ||
0534fa56 RH |
1614 | /* Fold away CONST_DECL to its value, if the type is scalar. */ |
1615 | if (TREE_CODE (base) == CONST_DECL | |
1616 | && is_gimple_min_invariant (DECL_INITIAL (base))) | |
1617 | return DECL_INITIAL (base); | |
1618 | ||
6de9cd9a DN |
1619 | /* Try folding *(&B+O) to B[X]. */ |
1620 | t = maybe_fold_offset_to_array_ref (base, offset, TREE_TYPE (expr)); | |
1621 | if (t) | |
1622 | return t; | |
1623 | ||
1624 | /* Try folding *(&B+O) to B.X. */ | |
1625 | t = maybe_fold_offset_to_component_ref (TREE_TYPE (base), base, offset, | |
1626 | TREE_TYPE (expr), false); | |
1627 | if (t) | |
1628 | return t; | |
1629 | ||
44de5aeb RK |
1630 | /* Fold *&B to B. We can only do this if EXPR is the same type |
1631 | as BASE. We can't do this if EXPR is the element type of an array | |
1632 | and BASE is the array. */ | |
1633 | if (integer_zerop (offset) | |
1634 | && lang_hooks.types_compatible_p (TREE_TYPE (base), | |
1635 | TREE_TYPE (expr))) | |
6de9cd9a DN |
1636 | return base; |
1637 | } | |
1638 | else | |
1639 | { | |
1640 | /* We can get here for out-of-range string constant accesses, | |
1641 | such as "_"[3]. Bail out of the entire substitution search | |
1642 | and arrange for the entire statement to be replaced by a | |
aabcd309 | 1643 | call to __builtin_trap. In all likelihood this will all be |
6de9cd9a DN |
1644 | constant-folded away, but in the meantime we can't leave with |
1645 | something that get_expr_operands can't understand. */ | |
1646 | ||
1647 | t = base; | |
1648 | STRIP_NOPS (t); | |
1649 | if (TREE_CODE (t) == ADDR_EXPR | |
1650 | && TREE_CODE (TREE_OPERAND (t, 0)) == STRING_CST) | |
1651 | { | |
1652 | /* FIXME: Except that this causes problems elsewhere with dead | |
0e61db61 | 1653 | code not being deleted, and we die in the rtl expanders |
6de9cd9a DN |
1654 | because we failed to remove some ssa_name. In the meantime, |
1655 | just return zero. */ | |
1656 | /* FIXME2: This condition should be signaled by | |
1657 | fold_read_from_constant_string directly, rather than | |
1658 | re-checking for it here. */ | |
1659 | return integer_zero_node; | |
1660 | } | |
1661 | ||
1662 | /* Try folding *(B+O) to B->X. Still an improvement. */ | |
1663 | if (POINTER_TYPE_P (TREE_TYPE (base))) | |
1664 | { | |
1665 | t = maybe_fold_offset_to_component_ref (TREE_TYPE (TREE_TYPE (base)), | |
1666 | base, offset, | |
1667 | TREE_TYPE (expr), true); | |
1668 | if (t) | |
1669 | return t; | |
1670 | } | |
1671 | } | |
1672 | ||
1673 | /* Otherwise we had an offset that we could not simplify. */ | |
1674 | return NULL_TREE; | |
1675 | } | |
1676 | ||
750628d8 | 1677 | |
6de9cd9a DN |
1678 | /* A subroutine of fold_stmt_r. EXPR is a PLUS_EXPR. |
1679 | ||
1680 | A quaint feature extant in our address arithmetic is that there | |
1681 | can be hidden type changes here. The type of the result need | |
1682 | not be the same as the type of the input pointer. | |
1683 | ||
1684 | What we're after here is an expression of the form | |
1685 | (T *)(&array + const) | |
1686 | where the cast doesn't actually exist, but is implicit in the | |
1687 | type of the PLUS_EXPR. We'd like to turn this into | |
1688 | &array[x] | |
1689 | which may be able to propagate further. */ | |
1690 | ||
1691 | static tree | |
1692 | maybe_fold_stmt_addition (tree expr) | |
1693 | { | |
1694 | tree op0 = TREE_OPERAND (expr, 0); | |
1695 | tree op1 = TREE_OPERAND (expr, 1); | |
1696 | tree ptr_type = TREE_TYPE (expr); | |
1697 | tree ptd_type; | |
1698 | tree t; | |
1699 | bool subtract = (TREE_CODE (expr) == MINUS_EXPR); | |
1700 | ||
1701 | /* We're only interested in pointer arithmetic. */ | |
1702 | if (!POINTER_TYPE_P (ptr_type)) | |
1703 | return NULL_TREE; | |
1704 | /* Canonicalize the integral operand to op1. */ | |
1705 | if (INTEGRAL_TYPE_P (TREE_TYPE (op0))) | |
1706 | { | |
1707 | if (subtract) | |
1708 | return NULL_TREE; | |
1709 | t = op0, op0 = op1, op1 = t; | |
1710 | } | |
1711 | /* It had better be a constant. */ | |
1712 | if (TREE_CODE (op1) != INTEGER_CST) | |
1713 | return NULL_TREE; | |
1714 | /* The first operand should be an ADDR_EXPR. */ | |
1715 | if (TREE_CODE (op0) != ADDR_EXPR) | |
1716 | return NULL_TREE; | |
1717 | op0 = TREE_OPERAND (op0, 0); | |
1718 | ||
1719 | /* If the first operand is an ARRAY_REF, expand it so that we can fold | |
1720 | the offset into it. */ | |
1721 | while (TREE_CODE (op0) == ARRAY_REF) | |
1722 | { | |
1723 | tree array_obj = TREE_OPERAND (op0, 0); | |
1724 | tree array_idx = TREE_OPERAND (op0, 1); | |
1725 | tree elt_type = TREE_TYPE (op0); | |
1726 | tree elt_size = TYPE_SIZE_UNIT (elt_type); | |
1727 | tree min_idx; | |
1728 | ||
1729 | if (TREE_CODE (array_idx) != INTEGER_CST) | |
1730 | break; | |
1731 | if (TREE_CODE (elt_size) != INTEGER_CST) | |
1732 | break; | |
1733 | ||
1734 | /* Un-bias the index by the min index of the array type. */ | |
1735 | min_idx = TYPE_DOMAIN (TREE_TYPE (array_obj)); | |
1736 | if (min_idx) | |
1737 | { | |
1738 | min_idx = TYPE_MIN_VALUE (min_idx); | |
1739 | if (min_idx) | |
1740 | { | |
44de5aeb RK |
1741 | if (TREE_CODE (min_idx) != INTEGER_CST) |
1742 | break; | |
1743 | ||
6de9cd9a DN |
1744 | array_idx = convert (TREE_TYPE (min_idx), array_idx); |
1745 | if (!integer_zerop (min_idx)) | |
1746 | array_idx = int_const_binop (MINUS_EXPR, array_idx, | |
1747 | min_idx, 0); | |
1748 | } | |
1749 | } | |
1750 | ||
1751 | /* Convert the index to a byte offset. */ | |
1752 | array_idx = convert (sizetype, array_idx); | |
1753 | array_idx = int_const_binop (MULT_EXPR, array_idx, elt_size, 0); | |
1754 | ||
1755 | /* Update the operands for the next round, or for folding. */ | |
1756 | /* If we're manipulating unsigned types, then folding into negative | |
1757 | values can produce incorrect results. Particularly if the type | |
1758 | is smaller than the width of the pointer. */ | |
1759 | if (subtract | |
1760 | && TYPE_UNSIGNED (TREE_TYPE (op1)) | |
1761 | && tree_int_cst_lt (array_idx, op1)) | |
1762 | return NULL; | |
1763 | op1 = int_const_binop (subtract ? MINUS_EXPR : PLUS_EXPR, | |
1764 | array_idx, op1, 0); | |
1765 | subtract = false; | |
1766 | op0 = array_obj; | |
1767 | } | |
1768 | ||
1769 | /* If we weren't able to fold the subtraction into another array reference, | |
1770 | canonicalize the integer for passing to the array and component ref | |
1771 | simplification functions. */ | |
1772 | if (subtract) | |
1773 | { | |
1774 | if (TYPE_UNSIGNED (TREE_TYPE (op1))) | |
1775 | return NULL; | |
1776 | op1 = fold (build1 (NEGATE_EXPR, TREE_TYPE (op1), op1)); | |
1777 | /* ??? In theory fold should always produce another integer. */ | |
1778 | if (TREE_CODE (op1) != INTEGER_CST) | |
1779 | return NULL; | |
1780 | } | |
1781 | ||
1782 | ptd_type = TREE_TYPE (ptr_type); | |
1783 | ||
1784 | /* At which point we can try some of the same things as for indirects. */ | |
1785 | t = maybe_fold_offset_to_array_ref (op0, op1, ptd_type); | |
1786 | if (!t) | |
1787 | t = maybe_fold_offset_to_component_ref (TREE_TYPE (op0), op0, op1, | |
1788 | ptd_type, false); | |
1789 | if (t) | |
1790 | t = build1 (ADDR_EXPR, ptr_type, t); | |
1791 | ||
1792 | return t; | |
1793 | } | |
1794 | ||
750628d8 | 1795 | |
6de9cd9a DN |
1796 | /* Subroutine of fold_stmt called via walk_tree. We perform several |
1797 | simplifications of EXPR_P, mostly having to do with pointer arithmetic. */ | |
1798 | ||
1799 | static tree | |
1800 | fold_stmt_r (tree *expr_p, int *walk_subtrees, void *data) | |
1801 | { | |
1802 | bool *changed_p = data; | |
1803 | tree expr = *expr_p, t; | |
1804 | ||
1805 | /* ??? It'd be nice if walk_tree had a pre-order option. */ | |
1806 | switch (TREE_CODE (expr)) | |
1807 | { | |
1808 | case INDIRECT_REF: | |
1809 | t = walk_tree (&TREE_OPERAND (expr, 0), fold_stmt_r, data, NULL); | |
1810 | if (t) | |
1811 | return t; | |
1812 | *walk_subtrees = 0; | |
1813 | ||
1814 | t = maybe_fold_stmt_indirect (expr, TREE_OPERAND (expr, 0), | |
1815 | integer_zero_node); | |
1816 | break; | |
1817 | ||
1818 | /* ??? Could handle ARRAY_REF here, as a variant of INDIRECT_REF. | |
1819 | We'd only want to bother decomposing an existing ARRAY_REF if | |
1820 | the base array is found to have another offset contained within. | |
1821 | Otherwise we'd be wasting time. */ | |
1822 | ||
1823 | case ADDR_EXPR: | |
1824 | t = walk_tree (&TREE_OPERAND (expr, 0), fold_stmt_r, data, NULL); | |
1825 | if (t) | |
1826 | return t; | |
1827 | *walk_subtrees = 0; | |
1828 | ||
1829 | /* Set TREE_INVARIANT properly so that the value is properly | |
1830 | considered constant, and so gets propagated as expected. */ | |
1831 | if (*changed_p) | |
1832 | recompute_tree_invarant_for_addr_expr (expr); | |
1833 | return NULL_TREE; | |
1834 | ||
1835 | case PLUS_EXPR: | |
1836 | case MINUS_EXPR: | |
1837 | t = walk_tree (&TREE_OPERAND (expr, 0), fold_stmt_r, data, NULL); | |
1838 | if (t) | |
1839 | return t; | |
1840 | t = walk_tree (&TREE_OPERAND (expr, 1), fold_stmt_r, data, NULL); | |
1841 | if (t) | |
1842 | return t; | |
1843 | *walk_subtrees = 0; | |
1844 | ||
1845 | t = maybe_fold_stmt_addition (expr); | |
1846 | break; | |
1847 | ||
1848 | case COMPONENT_REF: | |
1849 | t = walk_tree (&TREE_OPERAND (expr, 0), fold_stmt_r, data, NULL); | |
1850 | if (t) | |
1851 | return t; | |
1852 | *walk_subtrees = 0; | |
1853 | ||
fa27426e RH |
1854 | /* Make sure the FIELD_DECL is actually a field in the type on the lhs. |
1855 | We've already checked that the records are compatible, so we should | |
1856 | come up with a set of compatible fields. */ | |
1857 | { | |
1858 | tree expr_record = TREE_TYPE (TREE_OPERAND (expr, 0)); | |
1859 | tree expr_field = TREE_OPERAND (expr, 1); | |
1860 | ||
1861 | if (DECL_FIELD_CONTEXT (expr_field) != TYPE_MAIN_VARIANT (expr_record)) | |
1862 | { | |
1863 | expr_field = find_compatible_field (expr_record, expr_field); | |
1864 | TREE_OPERAND (expr, 1) = expr_field; | |
1865 | } | |
1866 | } | |
6de9cd9a DN |
1867 | break; |
1868 | ||
1869 | default: | |
1870 | return NULL_TREE; | |
1871 | } | |
1872 | ||
1873 | if (t) | |
1874 | { | |
1875 | *expr_p = t; | |
1876 | *changed_p = true; | |
1877 | } | |
1878 | ||
1879 | return NULL_TREE; | |
1880 | } | |
1881 | ||
6de9cd9a | 1882 | |
750628d8 DN |
1883 | /* Return the string length of ARG in LENGTH. If ARG is an SSA name variable, |
1884 | follow its use-def chains. If LENGTH is not NULL and its value is not | |
1885 | equal to the length we determine, or if we are unable to determine the | |
1886 | length, return false. VISITED is a bitmap of visited variables. */ | |
6de9cd9a | 1887 | |
06a9b53f | 1888 | static bool |
750628d8 | 1889 | get_strlen (tree arg, tree *length, bitmap visited) |
6de9cd9a | 1890 | { |
750628d8 DN |
1891 | tree var, def_stmt, val; |
1892 | ||
1893 | if (TREE_CODE (arg) != SSA_NAME) | |
06a9b53f | 1894 | { |
750628d8 DN |
1895 | val = c_strlen (arg, 1); |
1896 | if (!val) | |
06a9b53f | 1897 | return false; |
cd709752 | 1898 | |
750628d8 DN |
1899 | if (*length && simple_cst_equal (val, *length) != 1) |
1900 | return false; | |
6de9cd9a | 1901 | |
750628d8 DN |
1902 | *length = val; |
1903 | return true; | |
6de9cd9a | 1904 | } |
06a9b53f | 1905 | |
750628d8 DN |
1906 | /* If we were already here, break the infinite cycle. */ |
1907 | if (bitmap_bit_p (visited, SSA_NAME_VERSION (arg))) | |
1908 | return true; | |
1909 | bitmap_set_bit (visited, SSA_NAME_VERSION (arg)); | |
1910 | ||
1911 | var = arg; | |
1912 | def_stmt = SSA_NAME_DEF_STMT (var); | |
6de9cd9a | 1913 | |
750628d8 DN |
1914 | switch (TREE_CODE (def_stmt)) |
1915 | { | |
1916 | case MODIFY_EXPR: | |
1917 | { | |
1918 | tree len, rhs; | |
1919 | ||
1920 | /* The RHS of the statement defining VAR must either have a | |
1921 | constant length or come from another SSA_NAME with a constant | |
1922 | length. */ | |
1923 | rhs = TREE_OPERAND (def_stmt, 1); | |
1924 | STRIP_NOPS (rhs); | |
1925 | if (TREE_CODE (rhs) == SSA_NAME) | |
1926 | return get_strlen (rhs, length, visited); | |
6de9cd9a | 1927 | |
750628d8 DN |
1928 | /* See if the RHS is a constant length. */ |
1929 | len = c_strlen (rhs, 1); | |
1930 | if (len) | |
1931 | { | |
1932 | if (*length && simple_cst_equal (len, *length) != 1) | |
1933 | return false; | |
6de9cd9a | 1934 | |
750628d8 DN |
1935 | *length = len; |
1936 | return true; | |
1937 | } | |
6de9cd9a | 1938 | |
750628d8 DN |
1939 | break; |
1940 | } | |
6de9cd9a | 1941 | |
750628d8 DN |
1942 | case PHI_NODE: |
1943 | { | |
1944 | /* All the arguments of the PHI node must have the same constant | |
1945 | length. */ | |
1946 | int i; | |
6de9cd9a | 1947 | |
750628d8 DN |
1948 | for (i = 0; i < PHI_NUM_ARGS (def_stmt); i++) |
1949 | { | |
1950 | tree arg = PHI_ARG_DEF (def_stmt, i); | |
6de9cd9a | 1951 | |
750628d8 DN |
1952 | /* If this PHI has itself as an argument, we cannot |
1953 | determine the string length of this argument. However, | |
1954 | if we can find a constant string length for the other | |
1955 | PHI args then we can still be sure that this is a | |
1956 | constant string length. So be optimistic and just | |
1957 | continue with the next argument. */ | |
1958 | if (arg == PHI_RESULT (def_stmt)) | |
1959 | continue; | |
6de9cd9a | 1960 | |
750628d8 DN |
1961 | if (!get_strlen (arg, length, visited)) |
1962 | return false; | |
1963 | } | |
6de9cd9a | 1964 | |
750628d8 | 1965 | return true; |
173b818d | 1966 | } |
6de9cd9a | 1967 | |
750628d8 DN |
1968 | default: |
1969 | break; | |
6de9cd9a DN |
1970 | } |
1971 | ||
750628d8 DN |
1972 | |
1973 | return false; | |
6de9cd9a DN |
1974 | } |
1975 | ||
1976 | ||
1977 | /* Fold builtin call FN in statement STMT. If it cannot be folded into a | |
1978 | constant, return NULL_TREE. Otherwise, return its constant value. */ | |
1979 | ||
1980 | static tree | |
1981 | ccp_fold_builtin (tree stmt, tree fn) | |
1982 | { | |
1983 | tree result, strlen_val[2]; | |
a32e70c3 | 1984 | tree callee, arglist, a; |
6de9cd9a | 1985 | int strlen_arg, i; |
a32e70c3 RS |
1986 | bitmap visited; |
1987 | bool ignore; | |
6de9cd9a | 1988 | |
a32e70c3 | 1989 | ignore = TREE_CODE (stmt) != MODIFY_EXPR; |
6de9cd9a DN |
1990 | |
1991 | /* First try the generic builtin folder. If that succeeds, return the | |
1992 | result directly. */ | |
49d1af89 KH |
1993 | callee = get_callee_fndecl (fn); |
1994 | arglist = TREE_OPERAND (fn, 1); | |
1995 | result = fold_builtin (callee, arglist, ignore); | |
6de9cd9a | 1996 | if (result) |
a32e70c3 RS |
1997 | { |
1998 | if (ignore) | |
1999 | STRIP_NOPS (result); | |
6de9cd9a | 2000 | return result; |
a32e70c3 RS |
2001 | } |
2002 | ||
2003 | /* Ignore MD builtins. */ | |
a32e70c3 RS |
2004 | if (DECL_BUILT_IN_CLASS (callee) == BUILT_IN_MD) |
2005 | return NULL_TREE; | |
6de9cd9a DN |
2006 | |
2007 | /* If the builtin could not be folded, and it has no argument list, | |
2008 | we're done. */ | |
2009 | if (!arglist) | |
2010 | return NULL_TREE; | |
2011 | ||
2012 | /* Limit the work only for builtins we know how to simplify. */ | |
2013 | switch (DECL_FUNCTION_CODE (callee)) | |
2014 | { | |
2015 | case BUILT_IN_STRLEN: | |
2016 | case BUILT_IN_FPUTS: | |
2017 | case BUILT_IN_FPUTS_UNLOCKED: | |
2018 | strlen_arg = 1; | |
2019 | break; | |
2020 | case BUILT_IN_STRCPY: | |
2021 | case BUILT_IN_STRNCPY: | |
2022 | strlen_arg = 2; | |
2023 | break; | |
2024 | default: | |
2025 | return NULL_TREE; | |
2026 | } | |
2027 | ||
2028 | /* Try to use the dataflow information gathered by the CCP process. */ | |
8bdbfff5 | 2029 | visited = BITMAP_ALLOC (NULL); |
6de9cd9a DN |
2030 | |
2031 | memset (strlen_val, 0, sizeof (strlen_val)); | |
2032 | for (i = 0, a = arglist; | |
2033 | strlen_arg; | |
2034 | i++, strlen_arg >>= 1, a = TREE_CHAIN (a)) | |
2035 | if (strlen_arg & 1) | |
2036 | { | |
2037 | bitmap_clear (visited); | |
2038 | if (!get_strlen (TREE_VALUE (a), &strlen_val[i], visited)) | |
2039 | strlen_val[i] = NULL_TREE; | |
2040 | } | |
2041 | ||
8bdbfff5 | 2042 | BITMAP_FREE (visited); |
6de9cd9a | 2043 | |
a32e70c3 | 2044 | result = NULL_TREE; |
6de9cd9a DN |
2045 | switch (DECL_FUNCTION_CODE (callee)) |
2046 | { | |
2047 | case BUILT_IN_STRLEN: | |
a32e70c3 | 2048 | if (strlen_val[0]) |
6de9cd9a | 2049 | { |
a32e70c3 | 2050 | tree new = fold_convert (TREE_TYPE (fn), strlen_val[0]); |
6de9cd9a DN |
2051 | |
2052 | /* If the result is not a valid gimple value, or not a cast | |
2053 | of a valid gimple value, then we can not use the result. */ | |
2054 | if (is_gimple_val (new) | |
2055 | || (is_gimple_cast (new) | |
2056 | && is_gimple_val (TREE_OPERAND (new, 0)))) | |
2057 | return new; | |
6de9cd9a | 2058 | } |
a32e70c3 RS |
2059 | break; |
2060 | ||
6de9cd9a | 2061 | case BUILT_IN_STRCPY: |
a32e70c3 | 2062 | if (strlen_val[1] && is_gimple_val (strlen_val[1])) |
a456b432 KH |
2063 | { |
2064 | tree fndecl = get_callee_fndecl (fn); | |
2065 | tree arglist = TREE_OPERAND (fn, 1); | |
2066 | result = fold_builtin_strcpy (fndecl, arglist, strlen_val[1]); | |
2067 | } | |
a32e70c3 RS |
2068 | break; |
2069 | ||
6de9cd9a | 2070 | case BUILT_IN_STRNCPY: |
a32e70c3 | 2071 | if (strlen_val[1] && is_gimple_val (strlen_val[1])) |
a456b432 KH |
2072 | { |
2073 | tree fndecl = get_callee_fndecl (fn); | |
2074 | tree arglist = TREE_OPERAND (fn, 1); | |
2075 | result = fold_builtin_strncpy (fndecl, arglist, strlen_val[1]); | |
2076 | } | |
a32e70c3 RS |
2077 | break; |
2078 | ||
6de9cd9a | 2079 | case BUILT_IN_FPUTS: |
a32e70c3 RS |
2080 | result = fold_builtin_fputs (arglist, |
2081 | TREE_CODE (stmt) != MODIFY_EXPR, 0, | |
2082 | strlen_val[0]); | |
2083 | break; | |
2084 | ||
6de9cd9a | 2085 | case BUILT_IN_FPUTS_UNLOCKED: |
a32e70c3 RS |
2086 | result = fold_builtin_fputs (arglist, |
2087 | TREE_CODE (stmt) != MODIFY_EXPR, 1, | |
2088 | strlen_val[0]); | |
2089 | break; | |
6de9cd9a DN |
2090 | |
2091 | default: | |
1e128c5f | 2092 | gcc_unreachable (); |
6de9cd9a DN |
2093 | } |
2094 | ||
a32e70c3 | 2095 | if (result && ignore) |
9675412f | 2096 | result = fold_ignored_result (result); |
a32e70c3 | 2097 | return result; |
6de9cd9a DN |
2098 | } |
2099 | ||
2100 | ||
750628d8 DN |
2101 | /* Fold the statement pointed by STMT_P. In some cases, this function may |
2102 | replace the whole statement with a new one. Returns true iff folding | |
2103 | makes any changes. */ | |
6de9cd9a | 2104 | |
750628d8 DN |
2105 | bool |
2106 | fold_stmt (tree *stmt_p) | |
6de9cd9a | 2107 | { |
750628d8 DN |
2108 | tree rhs, result, stmt; |
2109 | bool changed = false; | |
6de9cd9a | 2110 | |
750628d8 | 2111 | stmt = *stmt_p; |
6de9cd9a | 2112 | |
750628d8 DN |
2113 | /* If we replaced constants and the statement makes pointer dereferences, |
2114 | then we may need to fold instances of *&VAR into VAR, etc. */ | |
2115 | if (walk_tree (stmt_p, fold_stmt_r, &changed, NULL)) | |
2116 | { | |
2117 | *stmt_p | |
2118 | = build_function_call_expr (implicit_built_in_decls[BUILT_IN_TRAP], | |
2119 | NULL); | |
6de9cd9a DN |
2120 | return true; |
2121 | } | |
2122 | ||
750628d8 DN |
2123 | rhs = get_rhs (stmt); |
2124 | if (!rhs) | |
2125 | return changed; | |
2126 | result = NULL_TREE; | |
6de9cd9a | 2127 | |
750628d8 | 2128 | if (TREE_CODE (rhs) == CALL_EXPR) |
6de9cd9a | 2129 | { |
750628d8 | 2130 | tree callee; |
6de9cd9a | 2131 | |
750628d8 DN |
2132 | /* Check for builtins that CCP can handle using information not |
2133 | available in the generic fold routines. */ | |
2134 | callee = get_callee_fndecl (rhs); | |
2135 | if (callee && DECL_BUILT_IN (callee)) | |
2136 | result = ccp_fold_builtin (stmt, rhs); | |
2137 | else | |
6de9cd9a | 2138 | { |
750628d8 DN |
2139 | /* Check for resolvable OBJ_TYPE_REF. The only sorts we can resolve |
2140 | here are when we've propagated the address of a decl into the | |
2141 | object slot. */ | |
2142 | /* ??? Should perhaps do this in fold proper. However, doing it | |
2143 | there requires that we create a new CALL_EXPR, and that requires | |
2144 | copying EH region info to the new node. Easier to just do it | |
2145 | here where we can just smash the call operand. */ | |
2146 | callee = TREE_OPERAND (rhs, 0); | |
2147 | if (TREE_CODE (callee) == OBJ_TYPE_REF | |
2148 | && lang_hooks.fold_obj_type_ref | |
2149 | && TREE_CODE (OBJ_TYPE_REF_OBJECT (callee)) == ADDR_EXPR | |
6615c446 JO |
2150 | && DECL_P (TREE_OPERAND |
2151 | (OBJ_TYPE_REF_OBJECT (callee), 0))) | |
6de9cd9a | 2152 | { |
750628d8 | 2153 | tree t; |
6de9cd9a | 2154 | |
750628d8 DN |
2155 | /* ??? Caution: Broken ADDR_EXPR semantics means that |
2156 | looking at the type of the operand of the addr_expr | |
2157 | can yield an array type. See silly exception in | |
2158 | check_pointer_types_r. */ | |
6de9cd9a | 2159 | |
750628d8 DN |
2160 | t = TREE_TYPE (TREE_TYPE (OBJ_TYPE_REF_OBJECT (callee))); |
2161 | t = lang_hooks.fold_obj_type_ref (callee, t); | |
2162 | if (t) | |
2163 | { | |
2164 | TREE_OPERAND (rhs, 0) = t; | |
2165 | changed = true; | |
2166 | } | |
6de9cd9a | 2167 | } |
6de9cd9a | 2168 | } |
6de9cd9a DN |
2169 | } |
2170 | ||
750628d8 DN |
2171 | /* If we couldn't fold the RHS, hand over to the generic fold routines. */ |
2172 | if (result == NULL_TREE) | |
2173 | result = fold (rhs); | |
6de9cd9a | 2174 | |
750628d8 DN |
2175 | /* Strip away useless type conversions. Both the NON_LVALUE_EXPR that |
2176 | may have been added by fold, and "useless" type conversions that might | |
2177 | now be apparent due to propagation. */ | |
2178 | STRIP_USELESS_TYPE_CONVERSION (result); | |
2179 | ||
2180 | if (result != rhs) | |
2181 | changed |= set_rhs (stmt_p, result); | |
2182 | ||
2183 | return changed; | |
6de9cd9a DN |
2184 | } |
2185 | ||
2186 | \f | |
b28b1600 JJ |
2187 | /* Convert EXPR into a GIMPLE value suitable for substitution on the |
2188 | RHS of an assignment. Insert the necessary statements before | |
2189 | iterator *SI_P. */ | |
2190 | ||
2191 | static tree | |
2192 | convert_to_gimple_builtin (block_stmt_iterator *si_p, tree expr) | |
2193 | { | |
2194 | tree_stmt_iterator ti; | |
2195 | tree stmt = bsi_stmt (*si_p); | |
2196 | tree tmp, stmts = NULL; | |
2197 | ||
2198 | push_gimplify_context (); | |
2199 | tmp = get_initialized_tmp_var (expr, &stmts, NULL); | |
2200 | pop_gimplify_context (NULL); | |
2201 | ||
f47c96aa AM |
2202 | if (EXPR_HAS_LOCATION (stmt)) |
2203 | annotate_all_with_locus (&stmts, EXPR_LOCATION (stmt)); | |
2204 | ||
b28b1600 JJ |
2205 | /* The replacement can expose previously unreferenced variables. */ |
2206 | for (ti = tsi_start (stmts); !tsi_end_p (ti); tsi_next (&ti)) | |
2207 | { | |
f47c96aa | 2208 | tree new_stmt = tsi_stmt (ti); |
b28b1600 | 2209 | find_new_referenced_vars (tsi_stmt_ptr (ti)); |
f47c96aa AM |
2210 | bsi_insert_before (si_p, new_stmt, BSI_NEW_STMT); |
2211 | mark_new_vars_to_rename (bsi_stmt (*si_p)); | |
2212 | bsi_next (si_p); | |
b28b1600 JJ |
2213 | } |
2214 | ||
b28b1600 JJ |
2215 | return tmp; |
2216 | } | |
2217 | ||
2218 | ||
6de9cd9a DN |
2219 | /* A simple pass that attempts to fold all builtin functions. This pass |
2220 | is run after we've propagated as many constants as we can. */ | |
2221 | ||
2222 | static void | |
2223 | execute_fold_all_builtins (void) | |
2224 | { | |
a7d6ba24 | 2225 | bool cfg_changed = false; |
6de9cd9a DN |
2226 | basic_block bb; |
2227 | FOR_EACH_BB (bb) | |
2228 | { | |
2229 | block_stmt_iterator i; | |
2230 | for (i = bsi_start (bb); !bsi_end_p (i); bsi_next (&i)) | |
2231 | { | |
2232 | tree *stmtp = bsi_stmt_ptr (i); | |
2233 | tree call = get_rhs (*stmtp); | |
2234 | tree callee, result; | |
2235 | ||
2236 | if (!call || TREE_CODE (call) != CALL_EXPR) | |
2237 | continue; | |
2238 | callee = get_callee_fndecl (call); | |
2239 | if (!callee || DECL_BUILT_IN_CLASS (callee) != BUILT_IN_NORMAL) | |
2240 | continue; | |
2241 | ||
2242 | result = ccp_fold_builtin (*stmtp, call); | |
2243 | if (!result) | |
2244 | switch (DECL_FUNCTION_CODE (callee)) | |
2245 | { | |
2246 | case BUILT_IN_CONSTANT_P: | |
2247 | /* Resolve __builtin_constant_p. If it hasn't been | |
2248 | folded to integer_one_node by now, it's fairly | |
2249 | certain that the value simply isn't constant. */ | |
2250 | result = integer_zero_node; | |
2251 | break; | |
2252 | ||
2253 | default: | |
2254 | continue; | |
2255 | } | |
2256 | ||
2257 | if (dump_file && (dump_flags & TDF_DETAILS)) | |
2258 | { | |
2259 | fprintf (dump_file, "Simplified\n "); | |
2260 | print_generic_stmt (dump_file, *stmtp, dump_flags); | |
2261 | } | |
2262 | ||
b28b1600 JJ |
2263 | if (!set_rhs (stmtp, result)) |
2264 | { | |
2265 | result = convert_to_gimple_builtin (&i, result); | |
e16acfcd NS |
2266 | if (result) |
2267 | { | |
2268 | bool ok = set_rhs (stmtp, result); | |
2269 | ||
2270 | gcc_assert (ok); | |
2271 | } | |
b28b1600 | 2272 | } |
f430bae8 | 2273 | update_stmt (*stmtp); |
a7d6ba24 JJ |
2274 | if (maybe_clean_eh_stmt (*stmtp) |
2275 | && tree_purge_dead_eh_edges (bb)) | |
2276 | cfg_changed = true; | |
6de9cd9a DN |
2277 | |
2278 | if (dump_file && (dump_flags & TDF_DETAILS)) | |
2279 | { | |
2280 | fprintf (dump_file, "to\n "); | |
2281 | print_generic_stmt (dump_file, *stmtp, dump_flags); | |
2282 | fprintf (dump_file, "\n"); | |
2283 | } | |
2284 | } | |
2285 | } | |
a7d6ba24 JJ |
2286 | |
2287 | /* Delete unreachable blocks. */ | |
2288 | if (cfg_changed) | |
2289 | cleanup_tree_cfg (); | |
6de9cd9a DN |
2290 | } |
2291 | ||
750628d8 | 2292 | |
6de9cd9a DN |
2293 | struct tree_opt_pass pass_fold_builtins = |
2294 | { | |
2295 | "fab", /* name */ | |
2296 | NULL, /* gate */ | |
2297 | execute_fold_all_builtins, /* execute */ | |
2298 | NULL, /* sub */ | |
2299 | NULL, /* next */ | |
2300 | 0, /* static_pass_number */ | |
2301 | 0, /* tv_id */ | |
c1b763fa | 2302 | PROP_cfg | PROP_ssa | PROP_alias, /* properties_required */ |
6de9cd9a DN |
2303 | 0, /* properties_provided */ |
2304 | 0, /* properties_destroyed */ | |
2305 | 0, /* todo_flags_start */ | |
b28b1600 JJ |
2306 | TODO_dump_func |
2307 | | TODO_verify_ssa | |
0bca51f0 | 2308 | | TODO_update_ssa, /* todo_flags_finish */ |
9f8628ba | 2309 | 0 /* letter */ |
6de9cd9a | 2310 | }; |