Mercurial > hg > CbC > CbC_gcc
annotate gcc/tree-ssa-copy.c @ 108:7ad14f446135
add CbC-example/rectypeTest/
| author | Nobuyasu Oshiro <dimolto@cr.ie.u-ryukyu.ac.jp> |
|---|---|
| date | Thu, 14 Jun 2012 20:30:24 +0900 |
| parents | f6334be47118 |
| children | 04ced10e8804 |
| rev | line source |
|---|---|
| 0 | 1 /* Copy propagation and SSA_NAME replacement support routines. |
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2 Copyright (C) 2004, 2005, 2006, 2007, 2008, 2010 |
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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 "flags.h" | |
| 27 #include "tm_p.h" | |
| 28 #include "basic-block.h" | |
| 29 #include "output.h" | |
| 30 #include "function.h" | |
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31 #include "tree-pretty-print.h" |
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32 #include "gimple-pretty-print.h" |
| 0 | 33 #include "timevar.h" |
| 34 #include "tree-dump.h" | |
| 35 #include "tree-flow.h" | |
| 36 #include "tree-pass.h" | |
| 37 #include "tree-ssa-propagate.h" | |
| 38 #include "langhooks.h" | |
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39 #include "cfgloop.h" |
| 0 | 40 |
| 41 /* This file implements the copy propagation pass and provides a | |
| 42 handful of interfaces for performing const/copy propagation and | |
| 43 simple expression replacement which keep variable annotations | |
| 44 up-to-date. | |
| 45 | |
| 46 We require that for any copy operation where the RHS and LHS have | |
| 47 a non-null memory tag the memory tag be the same. It is OK | |
| 48 for one or both of the memory tags to be NULL. | |
| 49 | |
| 50 We also require tracking if a variable is dereferenced in a load or | |
| 51 store operation. | |
| 52 | |
| 53 We enforce these requirements by having all copy propagation and | |
| 54 replacements of one SSA_NAME with a different SSA_NAME to use the | |
| 55 APIs defined in this file. */ | |
| 56 | |
| 57 /* Return true if we may propagate ORIG into DEST, false otherwise. */ | |
| 58 | |
| 59 bool | |
| 60 may_propagate_copy (tree dest, tree orig) | |
| 61 { | |
| 62 tree type_d = TREE_TYPE (dest); | |
| 63 tree type_o = TREE_TYPE (orig); | |
| 64 | |
| 65 /* If ORIG flows in from an abnormal edge, it cannot be propagated. */ | |
| 66 if (TREE_CODE (orig) == SSA_NAME | |
| 67 && SSA_NAME_OCCURS_IN_ABNORMAL_PHI (orig)) | |
| 68 return false; | |
| 69 | |
| 70 /* If DEST is an SSA_NAME that flows from an abnormal edge, then it | |
| 71 cannot be replaced. */ | |
| 72 if (TREE_CODE (dest) == SSA_NAME | |
| 73 && SSA_NAME_OCCURS_IN_ABNORMAL_PHI (dest)) | |
| 74 return false; | |
| 75 | |
| 76 /* Do not copy between types for which we *do* need a conversion. */ | |
| 77 if (!useless_type_conversion_p (type_d, type_o)) | |
| 78 return false; | |
| 79 | |
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80 /* Propagating virtual operands is always ok. */ |
| 0 | 81 if (TREE_CODE (dest) == SSA_NAME && !is_gimple_reg (dest)) |
| 82 { | |
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83 /* But only between virtual operands. */ |
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84 gcc_assert (TREE_CODE (orig) == SSA_NAME && !is_gimple_reg (orig)); |
| 0 | 85 |
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86 return true; |
| 0 | 87 } |
| 88 | |
| 89 /* Anything else is OK. */ | |
| 90 return true; | |
| 91 } | |
| 92 | |
| 93 /* Like may_propagate_copy, but use as the destination expression | |
| 94 the principal expression (typically, the RHS) contained in | |
| 95 statement DEST. This is more efficient when working with the | |
| 96 gimple tuples representation. */ | |
| 97 | |
| 98 bool | |
| 99 may_propagate_copy_into_stmt (gimple dest, tree orig) | |
| 100 { | |
| 101 tree type_d; | |
| 102 tree type_o; | |
| 103 | |
| 104 /* If the statement is a switch or a single-rhs assignment, | |
| 105 then the expression to be replaced by the propagation may | |
| 106 be an SSA_NAME. Fortunately, there is an explicit tree | |
| 107 for the expression, so we delegate to may_propagate_copy. */ | |
| 108 | |
| 109 if (gimple_assign_single_p (dest)) | |
| 110 return may_propagate_copy (gimple_assign_rhs1 (dest), orig); | |
| 111 else if (gimple_code (dest) == GIMPLE_SWITCH) | |
| 112 return may_propagate_copy (gimple_switch_index (dest), orig); | |
| 113 | |
| 114 /* In other cases, the expression is not materialized, so there | |
| 115 is no destination to pass to may_propagate_copy. On the other | |
| 116 hand, the expression cannot be an SSA_NAME, so the analysis | |
| 117 is much simpler. */ | |
| 118 | |
| 119 if (TREE_CODE (orig) == SSA_NAME | |
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120 && SSA_NAME_OCCURS_IN_ABNORMAL_PHI (orig)) |
| 0 | 121 return false; |
| 122 | |
| 123 if (is_gimple_assign (dest)) | |
| 124 type_d = TREE_TYPE (gimple_assign_lhs (dest)); | |
| 125 else if (gimple_code (dest) == GIMPLE_COND) | |
| 126 type_d = boolean_type_node; | |
| 127 else if (is_gimple_call (dest) | |
| 128 && gimple_call_lhs (dest) != NULL_TREE) | |
| 129 type_d = TREE_TYPE (gimple_call_lhs (dest)); | |
| 130 else | |
| 131 gcc_unreachable (); | |
| 132 | |
| 133 type_o = TREE_TYPE (orig); | |
| 134 | |
| 135 if (!useless_type_conversion_p (type_d, type_o)) | |
| 136 return false; | |
| 137 | |
| 138 return true; | |
| 139 } | |
| 140 | |
| 141 /* Similarly, but we know that we're propagating into an ASM_EXPR. */ | |
| 142 | |
| 143 bool | |
| 144 may_propagate_copy_into_asm (tree dest) | |
| 145 { | |
| 146 /* Hard register operands of asms are special. Do not bypass. */ | |
| 147 return !(TREE_CODE (dest) == SSA_NAME | |
| 148 && TREE_CODE (SSA_NAME_VAR (dest)) == VAR_DECL | |
| 149 && DECL_HARD_REGISTER (SSA_NAME_VAR (dest))); | |
| 150 } | |
| 151 | |
| 152 | |
| 153 /* Common code for propagate_value and replace_exp. | |
| 154 | |
| 155 Replace use operand OP_P with VAL. FOR_PROPAGATION indicates if the | |
| 156 replacement is done to propagate a value or not. */ | |
| 157 | |
| 158 static void | |
| 159 replace_exp_1 (use_operand_p op_p, tree val, | |
| 160 bool for_propagation ATTRIBUTE_UNUSED) | |
| 161 { | |
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162 #if defined ENABLE_CHECKING |
| 0 | 163 tree op = USE_FROM_PTR (op_p); |
| 164 | |
| 165 gcc_assert (!(for_propagation | |
| 166 && TREE_CODE (op) == SSA_NAME | |
| 167 && TREE_CODE (val) == SSA_NAME | |
| 168 && !may_propagate_copy (op, val))); | |
| 169 #endif | |
| 170 | |
| 171 if (TREE_CODE (val) == SSA_NAME) | |
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172 SET_USE (op_p, val); |
| 0 | 173 else |
| 174 SET_USE (op_p, unsave_expr_now (val)); | |
| 175 } | |
| 176 | |
| 177 | |
| 178 /* Propagate the value VAL (assumed to be a constant or another SSA_NAME) | |
| 179 into the operand pointed to by OP_P. | |
| 180 | |
| 181 Use this version for const/copy propagation as it will perform additional | |
| 182 checks to ensure validity of the const/copy propagation. */ | |
| 183 | |
| 184 void | |
| 185 propagate_value (use_operand_p op_p, tree val) | |
| 186 { | |
| 187 replace_exp_1 (op_p, val, true); | |
| 188 } | |
| 189 | |
| 190 /* Replace *OP_P with value VAL (assumed to be a constant or another SSA_NAME). | |
| 191 | |
| 192 Use this version when not const/copy propagating values. For example, | |
| 193 PRE uses this version when building expressions as they would appear | |
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194 in specific blocks taking into account actions of PHI nodes. |
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195 |
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196 The statement in which an expression has been replaced should be |
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197 folded using fold_stmt_inplace. */ |
| 0 | 198 |
| 199 void | |
| 200 replace_exp (use_operand_p op_p, tree val) | |
| 201 { | |
| 202 replace_exp_1 (op_p, val, false); | |
| 203 } | |
| 204 | |
| 205 | |
| 206 /* Propagate the value VAL (assumed to be a constant or another SSA_NAME) | |
| 207 into the tree pointed to by OP_P. | |
| 208 | |
| 209 Use this version for const/copy propagation when SSA operands are not | |
| 210 available. It will perform the additional checks to ensure validity of | |
| 211 the const/copy propagation, but will not update any operand information. | |
| 212 Be sure to mark the stmt as modified. */ | |
| 213 | |
| 214 void | |
| 215 propagate_tree_value (tree *op_p, tree val) | |
| 216 { | |
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217 gcc_checking_assert (!(TREE_CODE (val) == SSA_NAME |
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218 && *op_p |
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219 && TREE_CODE (*op_p) == SSA_NAME |
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220 && !may_propagate_copy (*op_p, val))); |
| 0 | 221 |
| 222 if (TREE_CODE (val) == SSA_NAME) | |
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223 *op_p = val; |
| 0 | 224 else |
| 225 *op_p = unsave_expr_now (val); | |
| 226 } | |
| 227 | |
| 228 | |
| 229 /* Like propagate_tree_value, but use as the operand to replace | |
| 230 the principal expression (typically, the RHS) contained in the | |
| 231 statement referenced by iterator GSI. Note that it is not | |
| 232 always possible to update the statement in-place, so a new | |
| 233 statement may be created to replace the original. */ | |
| 234 | |
| 235 void | |
| 236 propagate_tree_value_into_stmt (gimple_stmt_iterator *gsi, tree val) | |
| 237 { | |
| 238 gimple stmt = gsi_stmt (*gsi); | |
| 239 | |
| 240 if (is_gimple_assign (stmt)) | |
| 241 { | |
| 242 tree expr = NULL_TREE; | |
| 243 if (gimple_assign_single_p (stmt)) | |
| 244 expr = gimple_assign_rhs1 (stmt); | |
| 245 propagate_tree_value (&expr, val); | |
| 246 gimple_assign_set_rhs_from_tree (gsi, expr); | |
| 247 stmt = gsi_stmt (*gsi); | |
| 248 } | |
| 249 else if (gimple_code (stmt) == GIMPLE_COND) | |
| 250 { | |
| 251 tree lhs = NULL_TREE; | |
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252 tree rhs = build_zero_cst (TREE_TYPE (val)); |
| 0 | 253 propagate_tree_value (&lhs, val); |
| 254 gimple_cond_set_code (stmt, NE_EXPR); | |
| 255 gimple_cond_set_lhs (stmt, lhs); | |
| 256 gimple_cond_set_rhs (stmt, rhs); | |
| 257 } | |
| 258 else if (is_gimple_call (stmt) | |
| 259 && gimple_call_lhs (stmt) != NULL_TREE) | |
| 260 { | |
| 261 gimple new_stmt; | |
| 262 | |
| 263 tree expr = NULL_TREE; | |
| 264 propagate_tree_value (&expr, val); | |
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265 new_stmt = gimple_build_assign (gimple_call_lhs (stmt), expr); |
| 0 | 266 move_ssa_defining_stmt_for_defs (new_stmt, stmt); |
| 267 gsi_replace (gsi, new_stmt, false); | |
| 268 } | |
| 269 else if (gimple_code (stmt) == GIMPLE_SWITCH) | |
| 270 propagate_tree_value (gimple_switch_index_ptr (stmt), val); | |
| 271 else | |
| 272 gcc_unreachable (); | |
| 273 } | |
| 274 | |
| 275 /*--------------------------------------------------------------------------- | |
| 276 Copy propagation | |
| 277 ---------------------------------------------------------------------------*/ | |
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278 /* Lattice for copy-propagation. The lattice is initialized to |
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279 UNDEFINED (value == NULL) for SSA names that can become a copy |
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280 of something or VARYING (value == self) if not (see get_copy_of_val |
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281 and stmt_may_generate_copy). Other values make the name a COPY |
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282 of that value. |
| 0 | 283 |
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284 When visiting a statement or PHI node the lattice value for an |
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285 SSA name can transition from UNDEFINED to COPY to VARYING. */ |
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286 |
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287 struct prop_value_d { |
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288 /* Copy-of value. */ |
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289 tree value; |
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290 }; |
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291 typedef struct prop_value_d prop_value_t; |
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292 |
| 0 | 293 static prop_value_t *copy_of; |
| 294 | |
| 295 | |
| 296 /* Return true if this statement may generate a useful copy. */ | |
| 297 | |
| 298 static bool | |
| 299 stmt_may_generate_copy (gimple stmt) | |
| 300 { | |
| 301 if (gimple_code (stmt) == GIMPLE_PHI) | |
| 302 return !SSA_NAME_OCCURS_IN_ABNORMAL_PHI (gimple_phi_result (stmt)); | |
| 303 | |
| 304 if (gimple_code (stmt) != GIMPLE_ASSIGN) | |
| 305 return false; | |
| 306 | |
| 307 /* If the statement has volatile operands, it won't generate a | |
| 308 useful copy. */ | |
| 309 if (gimple_has_volatile_ops (stmt)) | |
| 310 return false; | |
| 311 | |
| 312 /* Statements with loads and/or stores will never generate a useful copy. */ | |
|
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313 if (gimple_vuse (stmt)) |
| 0 | 314 return false; |
| 315 | |
| 316 /* Otherwise, the only statements that generate useful copies are | |
| 317 assignments whose RHS is just an SSA name that doesn't flow | |
| 318 through abnormal edges. */ | |
| 319 return (gimple_assign_rhs_code (stmt) == SSA_NAME | |
| 320 && !SSA_NAME_OCCURS_IN_ABNORMAL_PHI (gimple_assign_rhs1 (stmt))); | |
| 321 } | |
| 322 | |
| 323 | |
| 324 /* Return the copy-of value for VAR. */ | |
| 325 | |
| 326 static inline prop_value_t * | |
| 327 get_copy_of_val (tree var) | |
| 328 { | |
| 329 prop_value_t *val = ©_of[SSA_NAME_VERSION (var)]; | |
| 330 | |
| 331 if (val->value == NULL_TREE | |
| 332 && !stmt_may_generate_copy (SSA_NAME_DEF_STMT (var))) | |
| 333 { | |
| 334 /* If the variable will never generate a useful copy relation, | |
| 335 make it its own copy. */ | |
| 336 val->value = var; | |
| 337 } | |
| 338 | |
| 339 return val; | |
| 340 } | |
| 341 | |
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342 /* Return the variable VAR is a copy of or VAR if VAR isn't the result |
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343 of a copy. */ |
| 0 | 344 |
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345 static inline tree |
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346 valueize_val (tree var) |
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347 { |
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348 if (TREE_CODE (var) == SSA_NAME) |
| 0 | 349 { |
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350 tree val = get_copy_of_val (var)->value; |
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351 if (val) |
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352 return val; |
| 0 | 353 } |
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354 return var; |
| 0 | 355 } |
| 356 | |
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357 /* Set VAL to be the copy of VAR. If that changed return true. */ |
| 0 | 358 |
| 359 static inline bool | |
|
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360 set_copy_of_val (tree var, tree val) |
| 0 | 361 { |
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362 unsigned int ver = SSA_NAME_VERSION (var); |
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363 tree old; |
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364 |
| 0 | 365 /* Set FIRST to be the first link in COPY_OF[DEST]. If that |
| 366 changed, return true. */ | |
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367 old = copy_of[ver].value; |
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368 copy_of[ver].value = val; |
| 0 | 369 |
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370 if (old != val |
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371 || (val && !operand_equal_p (old, val, 0))) |
| 0 | 372 return true; |
| 373 | |
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374 return false; |
| 0 | 375 } |
| 376 | |
| 377 | |
| 378 /* Dump the copy-of value for variable VAR to FILE. */ | |
| 379 | |
| 380 static void | |
| 381 dump_copy_of (FILE *file, tree var) | |
| 382 { | |
| 383 tree val; | |
| 384 | |
| 385 print_generic_expr (file, var, dump_flags); | |
| 386 if (TREE_CODE (var) != SSA_NAME) | |
| 387 return; | |
|
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388 |
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389 val = copy_of[SSA_NAME_VERSION (var)].value; |
| 0 | 390 fprintf (file, " copy-of chain: "); |
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391 print_generic_expr (file, var, 0); |
| 0 | 392 fprintf (file, " "); |
|
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393 if (!val) |
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394 fprintf (file, "[UNDEFINED]"); |
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395 else if (val == var) |
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396 fprintf (file, "[NOT A COPY]"); |
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397 else |
| 0 | 398 { |
| 399 fprintf (file, "-> "); | |
| 400 print_generic_expr (file, val, 0); | |
| 401 fprintf (file, " "); | |
|
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402 fprintf (file, "[COPY]"); |
| 0 | 403 } |
| 404 } | |
| 405 | |
| 406 | |
| 407 /* Evaluate the RHS of STMT. If it produces a valid copy, set the LHS | |
|
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408 value and store the LHS into *RESULT_P. */ |
| 0 | 409 |
| 410 static enum ssa_prop_result | |
| 411 copy_prop_visit_assignment (gimple stmt, tree *result_p) | |
| 412 { | |
| 413 tree lhs, rhs; | |
| 414 | |
| 415 lhs = gimple_assign_lhs (stmt); | |
|
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416 rhs = valueize_val (gimple_assign_rhs1 (stmt)); |
| 0 | 417 |
| 418 if (TREE_CODE (lhs) == SSA_NAME) | |
| 419 { | |
| 420 /* Straight copy between two SSA names. First, make sure that | |
| 421 we can propagate the RHS into uses of LHS. */ | |
| 422 if (!may_propagate_copy (lhs, rhs)) | |
| 423 return SSA_PROP_VARYING; | |
| 424 | |
| 425 *result_p = lhs; | |
|
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426 if (set_copy_of_val (*result_p, rhs)) |
| 0 | 427 return SSA_PROP_INTERESTING; |
| 428 else | |
| 429 return SSA_PROP_NOT_INTERESTING; | |
| 430 } | |
| 431 | |
| 432 return SSA_PROP_VARYING; | |
| 433 } | |
| 434 | |
| 435 | |
| 436 /* Visit the GIMPLE_COND STMT. Return SSA_PROP_INTERESTING | |
| 437 if it can determine which edge will be taken. Otherwise, return | |
| 438 SSA_PROP_VARYING. */ | |
| 439 | |
| 440 static enum ssa_prop_result | |
| 441 copy_prop_visit_cond_stmt (gimple stmt, edge *taken_edge_p) | |
| 442 { | |
| 443 enum ssa_prop_result retval = SSA_PROP_VARYING; | |
|
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444 location_t loc = gimple_location (stmt); |
| 0 | 445 |
| 446 tree op0 = gimple_cond_lhs (stmt); | |
| 447 tree op1 = gimple_cond_rhs (stmt); | |
| 448 | |
| 449 /* The only conditionals that we may be able to compute statically | |
| 450 are predicates involving two SSA_NAMEs. */ | |
| 451 if (TREE_CODE (op0) == SSA_NAME && TREE_CODE (op1) == SSA_NAME) | |
| 452 { | |
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453 op0 = valueize_val (op0); |
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454 op1 = valueize_val (op1); |
| 0 | 455 |
| 456 /* See if we can determine the predicate's value. */ | |
| 457 if (dump_file && (dump_flags & TDF_DETAILS)) | |
| 458 { | |
| 459 fprintf (dump_file, "Trying to determine truth value of "); | |
| 460 fprintf (dump_file, "predicate "); | |
| 461 print_gimple_stmt (dump_file, stmt, 0, 0); | |
| 462 } | |
| 463 | |
| 464 /* We can fold COND and get a useful result only when we have | |
| 465 the same SSA_NAME on both sides of a comparison operator. */ | |
| 466 if (op0 == op1) | |
| 467 { | |
|
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468 tree folded_cond = fold_binary_loc (loc, gimple_cond_code (stmt), |
| 0 | 469 boolean_type_node, op0, op1); |
| 470 if (folded_cond) | |
| 471 { | |
| 472 basic_block bb = gimple_bb (stmt); | |
| 473 *taken_edge_p = find_taken_edge (bb, folded_cond); | |
| 474 if (*taken_edge_p) | |
| 475 retval = SSA_PROP_INTERESTING; | |
| 476 } | |
| 477 } | |
| 478 } | |
| 479 | |
| 480 if (dump_file && (dump_flags & TDF_DETAILS) && *taken_edge_p) | |
| 481 fprintf (dump_file, "\nConditional will always take edge %d->%d\n", | |
| 482 (*taken_edge_p)->src->index, (*taken_edge_p)->dest->index); | |
| 483 | |
| 484 return retval; | |
| 485 } | |
| 486 | |
| 487 | |
| 488 /* Evaluate statement STMT. If the statement produces a new output | |
| 489 value, return SSA_PROP_INTERESTING and store the SSA_NAME holding | |
| 490 the new value in *RESULT_P. | |
| 491 | |
| 492 If STMT is a conditional branch and we can determine its truth | |
| 493 value, set *TAKEN_EDGE_P accordingly. | |
| 494 | |
| 495 If the new value produced by STMT is varying, return | |
| 496 SSA_PROP_VARYING. */ | |
| 497 | |
| 498 static enum ssa_prop_result | |
| 499 copy_prop_visit_stmt (gimple stmt, edge *taken_edge_p, tree *result_p) | |
| 500 { | |
| 501 enum ssa_prop_result retval; | |
| 502 | |
| 503 if (dump_file && (dump_flags & TDF_DETAILS)) | |
| 504 { | |
| 505 fprintf (dump_file, "\nVisiting statement:\n"); | |
| 506 print_gimple_stmt (dump_file, stmt, 0, dump_flags); | |
| 507 fprintf (dump_file, "\n"); | |
| 508 } | |
| 509 | |
| 510 if (gimple_assign_single_p (stmt) | |
| 511 && TREE_CODE (gimple_assign_lhs (stmt)) == SSA_NAME | |
|
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512 && (TREE_CODE (gimple_assign_rhs1 (stmt)) == SSA_NAME |
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513 || is_gimple_min_invariant (gimple_assign_rhs1 (stmt)))) |
| 0 | 514 { |
| 515 /* If the statement is a copy assignment, evaluate its RHS to | |
| 516 see if the lattice value of its output has changed. */ | |
| 517 retval = copy_prop_visit_assignment (stmt, result_p); | |
| 518 } | |
| 519 else if (gimple_code (stmt) == GIMPLE_COND) | |
| 520 { | |
| 521 /* See if we can determine which edge goes out of a conditional | |
| 522 jump. */ | |
| 523 retval = copy_prop_visit_cond_stmt (stmt, taken_edge_p); | |
| 524 } | |
| 525 else | |
| 526 retval = SSA_PROP_VARYING; | |
| 527 | |
| 528 if (retval == SSA_PROP_VARYING) | |
| 529 { | |
| 530 tree def; | |
| 531 ssa_op_iter i; | |
| 532 | |
| 533 /* Any other kind of statement is not interesting for constant | |
| 534 propagation and, therefore, not worth simulating. */ | |
| 535 if (dump_file && (dump_flags & TDF_DETAILS)) | |
| 536 fprintf (dump_file, "No interesting values produced.\n"); | |
| 537 | |
| 538 /* The assignment is not a copy operation. Don't visit this | |
| 539 statement again and mark all the definitions in the statement | |
| 540 to be copies of nothing. */ | |
| 541 FOR_EACH_SSA_TREE_OPERAND (def, stmt, i, SSA_OP_ALL_DEFS) | |
| 542 set_copy_of_val (def, def); | |
| 543 } | |
| 544 | |
| 545 return retval; | |
| 546 } | |
| 547 | |
| 548 | |
| 549 /* Visit PHI node PHI. If all the arguments produce the same value, | |
| 550 set it to be the value of the LHS of PHI. */ | |
| 551 | |
| 552 static enum ssa_prop_result | |
| 553 copy_prop_visit_phi_node (gimple phi) | |
| 554 { | |
| 555 enum ssa_prop_result retval; | |
| 556 unsigned i; | |
|
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557 prop_value_t phi_val = { NULL_TREE }; |
| 0 | 558 |
| 559 tree lhs = gimple_phi_result (phi); | |
| 560 | |
| 561 if (dump_file && (dump_flags & TDF_DETAILS)) | |
| 562 { | |
| 563 fprintf (dump_file, "\nVisiting PHI node: "); | |
| 564 print_gimple_stmt (dump_file, phi, 0, dump_flags); | |
| 565 } | |
| 566 | |
| 567 for (i = 0; i < gimple_phi_num_args (phi); i++) | |
| 568 { | |
| 569 prop_value_t *arg_val; | |
| 570 tree arg = gimple_phi_arg_def (phi, i); | |
| 571 edge e = gimple_phi_arg_edge (phi, i); | |
| 572 | |
| 573 /* We don't care about values flowing through non-executable | |
| 574 edges. */ | |
| 575 if (!(e->flags & EDGE_EXECUTABLE)) | |
| 576 continue; | |
| 577 | |
| 578 /* Constants in the argument list never generate a useful copy. | |
| 579 Similarly, names that flow through abnormal edges cannot be | |
| 580 used to derive copies. */ | |
| 581 if (TREE_CODE (arg) != SSA_NAME || SSA_NAME_OCCURS_IN_ABNORMAL_PHI (arg)) | |
| 582 { | |
| 583 phi_val.value = lhs; | |
| 584 break; | |
| 585 } | |
| 586 | |
| 587 /* Avoid copy propagation from an inner into an outer loop. | |
| 588 Otherwise, this may move loop variant variables outside of | |
| 589 their loops and prevent coalescing opportunities. If the | |
| 590 value was loop invariant, it will be hoisted by LICM and | |
|
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591 exposed for copy propagation. Not a problem for virtual |
|
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592 operands though. |
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593 ??? The value will be always loop invariant. */ |
|
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594 if (is_gimple_reg (lhs) |
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595 && loop_depth_of_name (arg) > loop_depth_of_name (lhs)) |
| 0 | 596 { |
| 597 phi_val.value = lhs; | |
| 598 break; | |
| 599 } | |
| 600 | |
| 601 if (dump_file && (dump_flags & TDF_DETAILS)) | |
| 602 { | |
| 603 fprintf (dump_file, "\tArgument #%d: ", i); | |
| 604 dump_copy_of (dump_file, arg); | |
| 605 fprintf (dump_file, "\n"); | |
| 606 } | |
| 607 | |
| 608 arg_val = get_copy_of_val (arg); | |
| 609 | |
|
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610 /* If we didn't visit the definition of arg yet treat it as |
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611 UNDEFINED. This also handles PHI arguments that are the |
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612 same as lhs. We'll come here again. */ |
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613 if (!arg_val->value) |
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614 continue; |
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615 |
| 0 | 616 /* If the LHS didn't have a value yet, make it a copy of the |
|
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617 first argument we find. */ |
| 0 | 618 if (phi_val.value == NULL_TREE) |
| 619 { | |
|
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620 phi_val.value = arg_val->value; |
| 0 | 621 continue; |
| 622 } | |
| 623 | |
| 624 /* If PHI_VAL and ARG don't have a common copy-of chain, then | |
|
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625 this PHI node cannot be a copy operation. */ |
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626 if (phi_val.value != arg_val->value |
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627 && !operand_equal_p (phi_val.value, arg_val->value, 0)) |
| 0 | 628 { |
| 629 phi_val.value = lhs; | |
| 630 break; | |
| 631 } | |
| 632 } | |
| 633 | |
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634 if (phi_val.value |
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635 && may_propagate_copy (lhs, phi_val.value) |
| 0 | 636 && set_copy_of_val (lhs, phi_val.value)) |
| 637 retval = (phi_val.value != lhs) ? SSA_PROP_INTERESTING : SSA_PROP_VARYING; | |
| 638 else | |
| 639 retval = SSA_PROP_NOT_INTERESTING; | |
| 640 | |
| 641 if (dump_file && (dump_flags & TDF_DETAILS)) | |
| 642 { | |
|
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643 fprintf (dump_file, "PHI node "); |
| 0 | 644 dump_copy_of (dump_file, lhs); |
| 645 fprintf (dump_file, "\nTelling the propagator to "); | |
| 646 if (retval == SSA_PROP_INTERESTING) | |
| 647 fprintf (dump_file, "add SSA edges out of this PHI and continue."); | |
| 648 else if (retval == SSA_PROP_VARYING) | |
| 649 fprintf (dump_file, "add SSA edges out of this PHI and never visit again."); | |
| 650 else | |
| 651 fprintf (dump_file, "do nothing with SSA edges and keep iterating."); | |
| 652 fprintf (dump_file, "\n\n"); | |
| 653 } | |
| 654 | |
| 655 return retval; | |
| 656 } | |
| 657 | |
| 658 | |
|
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659 /* Initialize structures used for copy propagation. */ |
| 0 | 660 |
| 661 static void | |
| 662 init_copy_prop (void) | |
| 663 { | |
| 664 basic_block bb; | |
| 665 | |
| 666 copy_of = XCNEWVEC (prop_value_t, num_ssa_names); | |
| 667 | |
| 668 FOR_EACH_BB (bb) | |
| 669 { | |
| 670 gimple_stmt_iterator si; | |
| 671 int depth = bb->loop_depth; | |
|
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672 bool loop_exit_p = false; |
| 0 | 673 |
| 674 for (si = gsi_start_bb (bb); !gsi_end_p (si); gsi_next (&si)) | |
| 675 { | |
| 676 gimple stmt = gsi_stmt (si); | |
| 677 ssa_op_iter iter; | |
| 678 tree def; | |
| 679 | |
| 680 /* The only statements that we care about are those that may | |
| 681 generate useful copies. We also need to mark conditional | |
| 682 jumps so that their outgoing edges are added to the work | |
| 683 lists of the propagator. | |
| 684 | |
| 685 Avoid copy propagation from an inner into an outer loop. | |
| 686 Otherwise, this may move loop variant variables outside of | |
| 687 their loops and prevent coalescing opportunities. If the | |
| 688 value was loop invariant, it will be hoisted by LICM and | |
|
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689 exposed for copy propagation. |
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690 ??? This doesn't make sense. */ |
| 0 | 691 if (stmt_ends_bb_p (stmt)) |
| 692 prop_set_simulate_again (stmt, true); | |
| 693 else if (stmt_may_generate_copy (stmt) | |
| 694 /* Since we are iterating over the statements in | |
| 695 BB, not the phi nodes, STMT will always be an | |
| 696 assignment. */ | |
| 697 && loop_depth_of_name (gimple_assign_rhs1 (stmt)) <= depth) | |
| 698 prop_set_simulate_again (stmt, true); | |
| 699 else | |
| 700 prop_set_simulate_again (stmt, false); | |
| 701 | |
| 702 /* Mark all the outputs of this statement as not being | |
| 703 the copy of anything. */ | |
| 704 FOR_EACH_SSA_TREE_OPERAND (def, stmt, iter, SSA_OP_ALL_DEFS) | |
| 705 if (!prop_simulate_again_p (stmt)) | |
| 706 set_copy_of_val (def, def); | |
| 707 } | |
| 708 | |
|
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709 /* In loop-closed SSA form do not copy-propagate through |
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710 PHI nodes in blocks with a loop exit edge predecessor. */ |
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711 if (current_loops |
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712 && loops_state_satisfies_p (LOOP_CLOSED_SSA)) |
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713 { |
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714 edge_iterator ei; |
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715 edge e; |
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716 FOR_EACH_EDGE (e, ei, bb->preds) |
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717 if (loop_exit_edge_p (e->src->loop_father, e)) |
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718 loop_exit_p = true; |
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719 } |
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720 |
| 0 | 721 for (si = gsi_start_phis (bb); !gsi_end_p (si); gsi_next (&si)) |
| 722 { | |
| 723 gimple phi = gsi_stmt (si); | |
| 724 tree def; | |
| 725 | |
| 726 def = gimple_phi_result (phi); | |
|
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727 if (!is_gimple_reg (def) |
|
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728 || loop_exit_p) |
| 0 | 729 prop_set_simulate_again (phi, false); |
| 730 else | |
| 731 prop_set_simulate_again (phi, true); | |
| 732 | |
| 733 if (!prop_simulate_again_p (phi)) | |
| 734 set_copy_of_val (def, def); | |
| 735 } | |
| 736 } | |
| 737 } | |
| 738 | |
|
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739 /* Callback for substitute_and_fold to get at the final copy-of values. */ |
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740 |
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741 static tree |
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742 get_value (tree name) |
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743 { |
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744 tree val = copy_of[SSA_NAME_VERSION (name)].value; |
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745 if (val && val != name) |
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746 return val; |
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747 return NULL_TREE; |
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748 } |
| 0 | 749 |
| 750 /* Deallocate memory used in copy propagation and do final | |
| 751 substitution. */ | |
| 752 | |
| 753 static void | |
| 754 fini_copy_prop (void) | |
| 755 { | |
|
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756 unsigned i; |
|
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757 |
| 0 | 758 /* Set the final copy-of value for each variable by traversing the |
| 759 copy-of chains. */ | |
| 760 for (i = 1; i < num_ssa_names; i++) | |
| 761 { | |
| 762 tree var = ssa_name (i); | |
|
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763 if (!var |
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764 || !copy_of[i].value |
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765 || copy_of[i].value == var) |
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766 continue; |
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767 |
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768 /* In theory the points-to solution of all members of the |
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769 copy chain is their intersection. For now we do not bother |
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770 to compute this but only make sure we do not lose points-to |
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771 information completely by setting the points-to solution |
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772 of the representative to the first solution we find if |
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773 it doesn't have one already. */ |
|
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774 if (copy_of[i].value != var |
|
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775 && POINTER_TYPE_P (TREE_TYPE (var)) |
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776 && SSA_NAME_PTR_INFO (var) |
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777 && !SSA_NAME_PTR_INFO (copy_of[i].value)) |
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778 duplicate_ssa_name_ptr_info (copy_of[i].value, SSA_NAME_PTR_INFO (var)); |
| 0 | 779 } |
| 780 | |
|
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781 /* Don't do DCE if we have loops. That's the simplest way to not |
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782 destroy the scev cache. */ |
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783 substitute_and_fold (get_value, NULL, !current_loops); |
| 0 | 784 |
| 785 free (copy_of); | |
| 786 } | |
| 787 | |
| 788 | |
| 789 /* Main entry point to the copy propagator. | |
| 790 | |
| 791 PHIS_ONLY is true if we should only consider PHI nodes as generating | |
|
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792 copy propagation opportunities. |
| 0 | 793 |
| 794 The algorithm propagates the value COPY-OF using ssa_propagate. For | |
| 795 every variable X_i, COPY-OF(X_i) indicates which variable is X_i created | |
| 796 from. The following example shows how the algorithm proceeds at a | |
| 797 high level: | |
| 798 | |
| 799 1 a_24 = x_1 | |
| 800 2 a_2 = PHI <a_24, x_1> | |
| 801 3 a_5 = PHI <a_2> | |
| 802 4 x_1 = PHI <x_298, a_5, a_2> | |
| 803 | |
| 804 The end result should be that a_2, a_5, a_24 and x_1 are a copy of | |
| 805 x_298. Propagation proceeds as follows. | |
| 806 | |
| 807 Visit #1: a_24 is copy-of x_1. Value changed. | |
| 808 Visit #2: a_2 is copy-of x_1. Value changed. | |
| 809 Visit #3: a_5 is copy-of x_1. Value changed. | |
| 810 Visit #4: x_1 is copy-of x_298. Value changed. | |
| 811 Visit #1: a_24 is copy-of x_298. Value changed. | |
| 812 Visit #2: a_2 is copy-of x_298. Value changed. | |
| 813 Visit #3: a_5 is copy-of x_298. Value changed. | |
| 814 Visit #4: x_1 is copy-of x_298. Stable state reached. | |
|
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815 |
| 0 | 816 When visiting PHI nodes, we only consider arguments that flow |
| 817 through edges marked executable by the propagation engine. So, | |
| 818 when visiting statement #2 for the first time, we will only look at | |
| 819 the first argument (a_24) and optimistically assume that its value | |
|
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820 is the copy of a_24 (x_1). */ |
| 0 | 821 |
| 822 static unsigned int | |
| 823 execute_copy_prop (void) | |
| 824 { | |
| 825 init_copy_prop (); | |
| 826 ssa_propagate (copy_prop_visit_stmt, copy_prop_visit_phi_node); | |
| 827 fini_copy_prop (); | |
| 828 return 0; | |
| 829 } | |
| 830 | |
| 831 static bool | |
| 832 gate_copy_prop (void) | |
| 833 { | |
| 834 return flag_tree_copy_prop != 0; | |
| 835 } | |
| 836 | |
| 837 struct gimple_opt_pass pass_copy_prop = | |
| 838 { | |
| 839 { | |
| 840 GIMPLE_PASS, | |
| 841 "copyprop", /* name */ | |
| 842 gate_copy_prop, /* gate */ | |
| 843 execute_copy_prop, /* execute */ | |
| 844 NULL, /* sub */ | |
| 845 NULL, /* next */ | |
| 846 0, /* static_pass_number */ | |
| 847 TV_TREE_COPY_PROP, /* tv_id */ | |
| 848 PROP_ssa | PROP_cfg, /* properties_required */ | |
| 849 0, /* properties_provided */ | |
| 850 0, /* properties_destroyed */ | |
| 851 0, /* todo_flags_start */ | |
| 852 TODO_cleanup_cfg | |
| 853 | TODO_dump_func | |
| 854 | TODO_ggc_collect | |
| 855 | TODO_verify_ssa | |
| 856 | TODO_update_ssa /* todo_flags_finish */ | |
| 857 } | |
| 858 }; |