Mercurial > hg > CbC > CbC_gcc
annotate gcc/tree-nrv.c @ 63:b7f97abdc517 gcc-4.6-20100522
update gcc from gcc-4.5.0 to gcc-4.6
| author | ryoma <e075725@ie.u-ryukyu.ac.jp> |
|---|---|
| date | Mon, 24 May 2010 12:47:05 +0900 |
| parents | 77e2b8dfacca |
| children | f6334be47118 |
| rev | line source |
|---|---|
| 0 | 1 /* Language independent return value optimizations |
|
63
b7f97abdc517
update gcc from gcc-4.5.0 to gcc-4.6
ryoma <e075725@ie.u-ryukyu.ac.jp>
parents:
55
diff
changeset
|
2 Copyright (C) 2004, 2005, 2007, 2008, 2009, 2010 |
|
b7f97abdc517
update gcc from gcc-4.5.0 to gcc-4.6
ryoma <e075725@ie.u-ryukyu.ac.jp>
parents:
55
diff
changeset
|
3 Free Software Foundation, Inc. |
| 0 | 4 |
| 5 This file is part of GCC. | |
| 6 | |
| 7 GCC is free software; you can redistribute it and/or modify | |
| 8 it under the terms of the GNU General Public License as published by | |
| 9 the Free Software Foundation; either version 3, or (at your option) | |
| 10 any later version. | |
| 11 | |
| 12 GCC is distributed in the hope that it will be useful, | |
| 13 but WITHOUT ANY WARRANTY; without even the implied warranty of | |
| 14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
| 15 GNU General Public License for more details. | |
| 16 | |
| 17 You should have received a copy of the GNU General Public License | |
| 18 along with GCC; see the file COPYING3. If not see | |
| 19 <http://www.gnu.org/licenses/>. */ | |
| 20 | |
| 21 #include "config.h" | |
| 22 #include "system.h" | |
| 23 #include "coretypes.h" | |
| 24 #include "tm.h" | |
| 25 #include "tree.h" | |
| 26 #include "function.h" | |
| 27 #include "basic-block.h" | |
| 28 #include "diagnostic.h" | |
|
63
b7f97abdc517
update gcc from gcc-4.5.0 to gcc-4.6
ryoma <e075725@ie.u-ryukyu.ac.jp>
parents:
55
diff
changeset
|
29 #include "tree-pretty-print.h" |
| 0 | 30 #include "tree-flow.h" |
| 31 #include "timevar.h" | |
| 32 #include "tree-dump.h" | |
| 33 #include "tree-pass.h" | |
| 34 #include "langhooks.h" | |
|
63
b7f97abdc517
update gcc from gcc-4.5.0 to gcc-4.6
ryoma <e075725@ie.u-ryukyu.ac.jp>
parents:
55
diff
changeset
|
35 #include "flags.h" /* For "optimize" in gate_pass_return_slot. |
|
b7f97abdc517
update gcc from gcc-4.5.0 to gcc-4.6
ryoma <e075725@ie.u-ryukyu.ac.jp>
parents:
55
diff
changeset
|
36 FIXME: That should be up to the pass manager, |
|
b7f97abdc517
update gcc from gcc-4.5.0 to gcc-4.6
ryoma <e075725@ie.u-ryukyu.ac.jp>
parents:
55
diff
changeset
|
37 but pass_nrv is not in pass_all_optimizations. */ |
| 0 | 38 |
| 39 /* This file implements return value optimizations for functions which | |
| 40 return aggregate types. | |
| 41 | |
| 42 Basically this pass searches the function for return statements which | |
| 43 return a local aggregate. When converted to RTL such statements will | |
| 44 generate a copy from the local aggregate to final return value destination | |
| 45 mandated by the target's ABI. | |
| 46 | |
| 47 That copy can often be avoided by directly constructing the return value | |
| 48 into the final destination mandated by the target's ABI. | |
| 49 | |
|
55
77e2b8dfacca
update it from 4.4.3 to 4.5.0
ryoma <e075725@ie.u-ryukyu.ac.jp>
parents:
0
diff
changeset
|
50 This is basically a generic equivalent to the C++ front-end's |
| 0 | 51 Named Return Value optimization. */ |
| 52 | |
| 53 struct nrv_data | |
| 54 { | |
| 55 /* This is the temporary (a VAR_DECL) which appears in all of | |
| 56 this function's RETURN_EXPR statements. */ | |
| 57 tree var; | |
| 58 | |
| 59 /* This is the function's RESULT_DECL. We will replace all occurrences | |
| 60 of VAR with RESULT_DECL when we apply this optimization. */ | |
| 61 tree result; | |
|
55
77e2b8dfacca
update it from 4.4.3 to 4.5.0
ryoma <e075725@ie.u-ryukyu.ac.jp>
parents:
0
diff
changeset
|
62 int modified; |
| 0 | 63 }; |
| 64 | |
| 65 static tree finalize_nrv_r (tree *, int *, void *); | |
| 66 | |
| 67 /* Callback for the tree walker. | |
| 68 | |
| 69 If TP refers to a RETURN_EXPR, then set the expression being returned | |
| 70 to nrv_data->result. | |
| 71 | |
| 72 If TP refers to nrv_data->var, then replace nrv_data->var with | |
| 73 nrv_data->result. | |
| 74 | |
| 75 If we reach a node where we know all the subtrees are uninteresting, | |
| 76 then set *WALK_SUBTREES to zero. */ | |
| 77 | |
| 78 static tree | |
| 79 finalize_nrv_r (tree *tp, int *walk_subtrees, void *data) | |
| 80 { | |
| 81 struct walk_stmt_info *wi = (struct walk_stmt_info *) data; | |
| 82 struct nrv_data *dp = (struct nrv_data *) wi->info; | |
| 83 | |
| 84 /* No need to walk into types. */ | |
| 85 if (TYPE_P (*tp)) | |
| 86 *walk_subtrees = 0; | |
| 87 | |
| 88 /* Otherwise replace all occurrences of VAR with RESULT. */ | |
| 89 else if (*tp == dp->var) | |
|
55
77e2b8dfacca
update it from 4.4.3 to 4.5.0
ryoma <e075725@ie.u-ryukyu.ac.jp>
parents:
0
diff
changeset
|
90 { |
|
77e2b8dfacca
update it from 4.4.3 to 4.5.0
ryoma <e075725@ie.u-ryukyu.ac.jp>
parents:
0
diff
changeset
|
91 *tp = dp->result; |
|
77e2b8dfacca
update it from 4.4.3 to 4.5.0
ryoma <e075725@ie.u-ryukyu.ac.jp>
parents:
0
diff
changeset
|
92 dp->modified = 1; |
|
77e2b8dfacca
update it from 4.4.3 to 4.5.0
ryoma <e075725@ie.u-ryukyu.ac.jp>
parents:
0
diff
changeset
|
93 } |
| 0 | 94 |
| 95 /* Keep iterating. */ | |
| 96 return NULL_TREE; | |
| 97 } | |
| 98 | |
| 99 /* Main entry point for return value optimizations. | |
| 100 | |
| 101 If this function always returns the same local variable, and that | |
| 102 local variable is an aggregate type, then replace the variable with | |
| 103 the function's DECL_RESULT. | |
| 104 | |
| 105 This is the equivalent of the C++ named return value optimization | |
| 106 applied to optimized trees in a language independent form. If we | |
| 107 ever encounter languages which prevent this kind of optimization, | |
| 108 then we could either have the languages register the optimization or | |
| 109 we could change the gating function to check the current language. */ | |
|
55
77e2b8dfacca
update it from 4.4.3 to 4.5.0
ryoma <e075725@ie.u-ryukyu.ac.jp>
parents:
0
diff
changeset
|
110 |
| 0 | 111 static unsigned int |
| 112 tree_nrv (void) | |
| 113 { | |
| 114 tree result = DECL_RESULT (current_function_decl); | |
| 115 tree result_type = TREE_TYPE (result); | |
| 116 tree found = NULL; | |
| 117 basic_block bb; | |
| 118 gimple_stmt_iterator gsi; | |
| 119 struct nrv_data data; | |
| 120 | |
| 121 /* If this function does not return an aggregate type in memory, then | |
| 122 there is nothing to do. */ | |
| 123 if (!aggregate_value_p (result, current_function_decl)) | |
| 124 return 0; | |
| 125 | |
| 126 /* If a GIMPLE type is returned in memory, finalize_nrv_r might create | |
| 127 non-GIMPLE. */ | |
| 128 if (is_gimple_reg_type (result_type)) | |
| 129 return 0; | |
| 130 | |
| 131 /* If the front end already did something like this, don't do it here. */ | |
| 132 if (DECL_NAME (result)) | |
| 133 return 0; | |
| 134 | |
|
55
77e2b8dfacca
update it from 4.4.3 to 4.5.0
ryoma <e075725@ie.u-ryukyu.ac.jp>
parents:
0
diff
changeset
|
135 /* If the result has its address taken then it might be modified |
|
77e2b8dfacca
update it from 4.4.3 to 4.5.0
ryoma <e075725@ie.u-ryukyu.ac.jp>
parents:
0
diff
changeset
|
136 by means not detected in the following loop. Bail out in this |
|
77e2b8dfacca
update it from 4.4.3 to 4.5.0
ryoma <e075725@ie.u-ryukyu.ac.jp>
parents:
0
diff
changeset
|
137 case. */ |
|
77e2b8dfacca
update it from 4.4.3 to 4.5.0
ryoma <e075725@ie.u-ryukyu.ac.jp>
parents:
0
diff
changeset
|
138 if (TREE_ADDRESSABLE (result)) |
|
77e2b8dfacca
update it from 4.4.3 to 4.5.0
ryoma <e075725@ie.u-ryukyu.ac.jp>
parents:
0
diff
changeset
|
139 return 0; |
|
77e2b8dfacca
update it from 4.4.3 to 4.5.0
ryoma <e075725@ie.u-ryukyu.ac.jp>
parents:
0
diff
changeset
|
140 |
| 0 | 141 /* Look through each block for assignments to the RESULT_DECL. */ |
| 142 FOR_EACH_BB (bb) | |
| 143 { | |
| 144 for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi)) | |
| 145 { | |
| 146 gimple stmt = gsi_stmt (gsi); | |
| 147 tree ret_val; | |
| 148 | |
| 149 if (gimple_code (stmt) == GIMPLE_RETURN) | |
| 150 { | |
| 151 /* In a function with an aggregate return value, the | |
| 152 gimplifier has changed all non-empty RETURN_EXPRs to | |
| 153 return the RESULT_DECL. */ | |
| 154 ret_val = gimple_return_retval (stmt); | |
| 155 if (ret_val) | |
| 156 gcc_assert (ret_val == result); | |
| 157 } | |
| 158 else if (gimple_has_lhs (stmt) | |
| 159 && gimple_get_lhs (stmt) == result) | |
| 160 { | |
| 161 tree rhs; | |
| 162 | |
| 163 if (!gimple_assign_copy_p (stmt)) | |
| 164 return 0; | |
| 165 | |
| 166 rhs = gimple_assign_rhs1 (stmt); | |
| 167 | |
| 168 /* Now verify that this return statement uses the same value | |
| 169 as any previously encountered return statement. */ | |
| 170 if (found != NULL) | |
| 171 { | |
| 172 /* If we found a return statement using a different variable | |
| 173 than previous return statements, then we can not perform | |
| 174 NRV optimizations. */ | |
| 175 if (found != rhs) | |
| 176 return 0; | |
| 177 } | |
| 178 else | |
| 179 found = rhs; | |
| 180 | |
| 181 /* The returned value must be a local automatic variable of the | |
| 182 same type and alignment as the function's result. */ | |
| 183 if (TREE_CODE (found) != VAR_DECL | |
| 184 || TREE_THIS_VOLATILE (found) | |
| 185 || DECL_CONTEXT (found) != current_function_decl | |
| 186 || TREE_STATIC (found) | |
| 187 || TREE_ADDRESSABLE (found) | |
| 188 || DECL_ALIGN (found) > DECL_ALIGN (result) | |
| 189 || !useless_type_conversion_p (result_type, | |
|
55
77e2b8dfacca
update it from 4.4.3 to 4.5.0
ryoma <e075725@ie.u-ryukyu.ac.jp>
parents:
0
diff
changeset
|
190 TREE_TYPE (found))) |
| 0 | 191 return 0; |
| 192 } | |
| 193 else if (gimple_has_lhs (stmt)) | |
| 194 { | |
| 195 tree addr = get_base_address (gimple_get_lhs (stmt)); | |
|
55
77e2b8dfacca
update it from 4.4.3 to 4.5.0
ryoma <e075725@ie.u-ryukyu.ac.jp>
parents:
0
diff
changeset
|
196 /* If there's any MODIFY of component of RESULT, |
| 0 | 197 then bail out. */ |
| 198 if (addr && addr == result) | |
| 199 return 0; | |
| 200 } | |
| 201 } | |
| 202 } | |
| 203 | |
| 204 if (!found) | |
| 205 return 0; | |
| 206 | |
| 207 /* If dumping details, then note once and only the NRV replacement. */ | |
| 208 if (dump_file && (dump_flags & TDF_DETAILS)) | |
| 209 { | |
| 210 fprintf (dump_file, "NRV Replaced: "); | |
| 211 print_generic_expr (dump_file, found, dump_flags); | |
| 212 fprintf (dump_file, " with: "); | |
| 213 print_generic_expr (dump_file, result, dump_flags); | |
| 214 fprintf (dump_file, "\n"); | |
| 215 } | |
| 216 | |
| 217 /* At this point we know that all the return statements return the | |
| 218 same local which has suitable attributes for NRV. Copy debugging | |
| 219 information from FOUND to RESULT if it will be useful. But don't set | |
| 220 DECL_ABSTRACT_ORIGIN to point at another function. */ | |
| 221 if (!DECL_IGNORED_P (found) | |
| 222 && !(DECL_ABSTRACT_ORIGIN (found) | |
| 223 && DECL_CONTEXT (DECL_ABSTRACT_ORIGIN (found)) != current_function_decl)) | |
| 224 { | |
| 225 DECL_NAME (result) = DECL_NAME (found); | |
| 226 DECL_SOURCE_LOCATION (result) = DECL_SOURCE_LOCATION (found); | |
| 227 DECL_ABSTRACT_ORIGIN (result) = DECL_ABSTRACT_ORIGIN (found); | |
| 228 } | |
| 229 | |
|
55
77e2b8dfacca
update it from 4.4.3 to 4.5.0
ryoma <e075725@ie.u-ryukyu.ac.jp>
parents:
0
diff
changeset
|
230 TREE_ADDRESSABLE (result) |= TREE_ADDRESSABLE (found); |
| 0 | 231 |
| 232 /* Now walk through the function changing all references to VAR to be | |
| 233 RESULT. */ | |
| 234 data.var = found; | |
| 235 data.result = result; | |
| 236 FOR_EACH_BB (bb) | |
| 237 { | |
| 238 for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); ) | |
| 239 { | |
| 240 gimple stmt = gsi_stmt (gsi); | |
| 241 /* If this is a copy from VAR to RESULT, remove it. */ | |
| 242 if (gimple_assign_copy_p (stmt) | |
| 243 && gimple_assign_lhs (stmt) == result | |
| 244 && gimple_assign_rhs1 (stmt) == found) | |
|
55
77e2b8dfacca
update it from 4.4.3 to 4.5.0
ryoma <e075725@ie.u-ryukyu.ac.jp>
parents:
0
diff
changeset
|
245 { |
|
77e2b8dfacca
update it from 4.4.3 to 4.5.0
ryoma <e075725@ie.u-ryukyu.ac.jp>
parents:
0
diff
changeset
|
246 unlink_stmt_vdef (stmt); |
|
77e2b8dfacca
update it from 4.4.3 to 4.5.0
ryoma <e075725@ie.u-ryukyu.ac.jp>
parents:
0
diff
changeset
|
247 gsi_remove (&gsi, true); |
|
77e2b8dfacca
update it from 4.4.3 to 4.5.0
ryoma <e075725@ie.u-ryukyu.ac.jp>
parents:
0
diff
changeset
|
248 } |
| 0 | 249 else |
| 250 { | |
| 251 struct walk_stmt_info wi; | |
| 252 memset (&wi, 0, sizeof (wi)); | |
| 253 wi.info = &data; | |
|
55
77e2b8dfacca
update it from 4.4.3 to 4.5.0
ryoma <e075725@ie.u-ryukyu.ac.jp>
parents:
0
diff
changeset
|
254 data.modified = 0; |
| 0 | 255 walk_gimple_op (stmt, finalize_nrv_r, &wi); |
|
55
77e2b8dfacca
update it from 4.4.3 to 4.5.0
ryoma <e075725@ie.u-ryukyu.ac.jp>
parents:
0
diff
changeset
|
256 if (data.modified) |
|
77e2b8dfacca
update it from 4.4.3 to 4.5.0
ryoma <e075725@ie.u-ryukyu.ac.jp>
parents:
0
diff
changeset
|
257 update_stmt (stmt); |
| 0 | 258 gsi_next (&gsi); |
| 259 } | |
| 260 } | |
| 261 } | |
| 262 | |
| 263 /* FOUND is no longer used. Ensure it gets removed. */ | |
| 264 var_ann (found)->used = 0; | |
| 265 return 0; | |
| 266 } | |
| 267 | |
| 268 static bool | |
| 269 gate_pass_return_slot (void) | |
| 270 { | |
| 271 return optimize > 0; | |
| 272 } | |
| 273 | |
|
55
77e2b8dfacca
update it from 4.4.3 to 4.5.0
ryoma <e075725@ie.u-ryukyu.ac.jp>
parents:
0
diff
changeset
|
274 struct gimple_opt_pass pass_nrv = |
| 0 | 275 { |
| 276 { | |
| 277 GIMPLE_PASS, | |
| 278 "nrv", /* name */ | |
| 279 gate_pass_return_slot, /* gate */ | |
| 280 tree_nrv, /* execute */ | |
| 281 NULL, /* sub */ | |
| 282 NULL, /* next */ | |
| 283 0, /* static_pass_number */ | |
| 284 TV_TREE_NRV, /* tv_id */ | |
|
55
77e2b8dfacca
update it from 4.4.3 to 4.5.0
ryoma <e075725@ie.u-ryukyu.ac.jp>
parents:
0
diff
changeset
|
285 PROP_ssa | PROP_cfg, /* properties_required */ |
| 0 | 286 0, /* properties_provided */ |
| 287 0, /* properties_destroyed */ | |
| 288 0, /* todo_flags_start */ | |
| 289 TODO_dump_func | TODO_ggc_collect /* todo_flags_finish */ | |
| 290 } | |
| 291 }; | |
| 292 | |
| 293 /* Determine (pessimistically) whether DEST is available for NRV | |
| 294 optimization, where DEST is expected to be the LHS of a modify | |
| 295 expression where the RHS is a function returning an aggregate. | |
| 296 | |
|
63
b7f97abdc517
update gcc from gcc-4.5.0 to gcc-4.6
ryoma <e075725@ie.u-ryukyu.ac.jp>
parents:
55
diff
changeset
|
297 DEST is available if it is not clobbered by the call. */ |
| 0 | 298 |
| 299 static bool | |
|
63
b7f97abdc517
update gcc from gcc-4.5.0 to gcc-4.6
ryoma <e075725@ie.u-ryukyu.ac.jp>
parents:
55
diff
changeset
|
300 dest_safe_for_nrv_p (gimple call) |
| 0 | 301 { |
|
63
b7f97abdc517
update gcc from gcc-4.5.0 to gcc-4.6
ryoma <e075725@ie.u-ryukyu.ac.jp>
parents:
55
diff
changeset
|
302 tree dest = gimple_call_lhs (call); |
| 0 | 303 |
|
63
b7f97abdc517
update gcc from gcc-4.5.0 to gcc-4.6
ryoma <e075725@ie.u-ryukyu.ac.jp>
parents:
55
diff
changeset
|
304 dest = get_base_address (dest); |
|
b7f97abdc517
update gcc from gcc-4.5.0 to gcc-4.6
ryoma <e075725@ie.u-ryukyu.ac.jp>
parents:
55
diff
changeset
|
305 if (! dest) |
| 0 | 306 return false; |
| 307 | |
| 308 if (TREE_CODE (dest) == SSA_NAME) | |
|
63
b7f97abdc517
update gcc from gcc-4.5.0 to gcc-4.6
ryoma <e075725@ie.u-ryukyu.ac.jp>
parents:
55
diff
changeset
|
309 return true; |
| 0 | 310 |
|
63
b7f97abdc517
update gcc from gcc-4.5.0 to gcc-4.6
ryoma <e075725@ie.u-ryukyu.ac.jp>
parents:
55
diff
changeset
|
311 if (call_may_clobber_ref_p (call, dest)) |
| 0 | 312 return false; |
| 313 | |
| 314 return true; | |
| 315 } | |
| 316 | |
| 317 /* Walk through the function looking for GIMPLE_ASSIGNs with calls that | |
| 318 return in memory on the RHS. For each of these, determine whether it is | |
| 319 safe to pass the address of the LHS as the return slot, and mark the | |
| 320 call appropriately if so. | |
| 321 | |
| 322 The NRV shares the return slot with a local variable in the callee; this | |
| 323 optimization shares the return slot with the target of the call within | |
| 324 the caller. If the NRV is performed (which we can't know in general), | |
| 325 this optimization is safe if the address of the target has not | |
| 326 escaped prior to the call. If it has, modifications to the local | |
| 327 variable will produce visible changes elsewhere, as in PR c++/19317. */ | |
| 328 | |
| 329 static unsigned int | |
| 330 execute_return_slot_opt (void) | |
| 331 { | |
| 332 basic_block bb; | |
| 333 | |
| 334 FOR_EACH_BB (bb) | |
| 335 { | |
| 336 gimple_stmt_iterator gsi; | |
| 337 for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi)) | |
| 338 { | |
| 339 gimple stmt = gsi_stmt (gsi); | |
| 340 bool slot_opt_p; | |
| 341 | |
| 342 if (is_gimple_call (stmt) | |
| 343 && gimple_call_lhs (stmt) | |
| 344 && !gimple_call_return_slot_opt_p (stmt) | |
| 345 && aggregate_value_p (TREE_TYPE (gimple_call_lhs (stmt)), | |
| 346 gimple_call_fndecl (stmt)) | |
| 347 ) | |
| 348 { | |
| 349 /* Check if the location being assigned to is | |
|
63
b7f97abdc517
update gcc from gcc-4.5.0 to gcc-4.6
ryoma <e075725@ie.u-ryukyu.ac.jp>
parents:
55
diff
changeset
|
350 clobbered by the call. */ |
|
b7f97abdc517
update gcc from gcc-4.5.0 to gcc-4.6
ryoma <e075725@ie.u-ryukyu.ac.jp>
parents:
55
diff
changeset
|
351 slot_opt_p = dest_safe_for_nrv_p (stmt); |
| 0 | 352 gimple_call_set_return_slot_opt (stmt, slot_opt_p); |
| 353 } | |
| 354 } | |
| 355 } | |
| 356 return 0; | |
| 357 } | |
| 358 | |
|
55
77e2b8dfacca
update it from 4.4.3 to 4.5.0
ryoma <e075725@ie.u-ryukyu.ac.jp>
parents:
0
diff
changeset
|
359 struct gimple_opt_pass pass_return_slot = |
| 0 | 360 { |
| 361 { | |
| 362 GIMPLE_PASS, | |
| 363 "retslot", /* name */ | |
| 364 NULL, /* gate */ | |
| 365 execute_return_slot_opt, /* execute */ | |
| 366 NULL, /* sub */ | |
| 367 NULL, /* next */ | |
| 368 0, /* static_pass_number */ | |
|
55
77e2b8dfacca
update it from 4.4.3 to 4.5.0
ryoma <e075725@ie.u-ryukyu.ac.jp>
parents:
0
diff
changeset
|
369 TV_NONE, /* tv_id */ |
|
77e2b8dfacca
update it from 4.4.3 to 4.5.0
ryoma <e075725@ie.u-ryukyu.ac.jp>
parents:
0
diff
changeset
|
370 PROP_ssa, /* properties_required */ |
| 0 | 371 0, /* properties_provided */ |
| 372 0, /* properties_destroyed */ | |
| 373 0, /* todo_flags_start */ | |
| 374 0 /* todo_flags_finish */ | |
| 375 } | |
| 376 }; |