Mercurial > hg > CbC > CbC_gcc
annotate gcc/tree-ssa-loop-ch.c @ 55:77e2b8dfacca gcc-4.4.5
update it from 4.4.3 to 4.5.0
| author | ryoma <e075725@ie.u-ryukyu.ac.jp> |
|---|---|
| date | Fri, 12 Feb 2010 23:39:51 +0900 |
| parents | a06113de4d67 |
| children | b7f97abdc517 |
| rev | line source |
|---|---|
| 0 | 1 /* Loop header copying on trees. |
| 2 Copyright (C) 2004, 2005, 2006, 2007, 2008 Free Software Foundation, Inc. | |
|
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3 |
| 0 | 4 This file is part of GCC. |
|
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5 |
| 0 | 6 GCC is free software; you can redistribute it and/or modify it |
| 7 under the terms of the GNU General Public License as published by the | |
| 8 Free Software Foundation; either version 3, or (at your option) any | |
| 9 later version. | |
|
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10 |
| 0 | 11 GCC is distributed in the hope that it will be useful, but WITHOUT |
| 12 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or | |
| 13 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License | |
| 14 for more details. | |
|
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15 |
| 0 | 16 You should have received a copy of the GNU General Public License |
| 17 along with GCC; see the file COPYING3. If not see | |
| 18 <http://www.gnu.org/licenses/>. */ | |
| 19 | |
| 20 #include "config.h" | |
| 21 #include "system.h" | |
| 22 #include "coretypes.h" | |
| 23 #include "tm.h" | |
| 24 #include "tree.h" | |
| 25 #include "rtl.h" | |
| 26 #include "tm_p.h" | |
| 27 #include "hard-reg-set.h" | |
| 28 #include "basic-block.h" | |
| 29 #include "output.h" | |
| 30 #include "diagnostic.h" | |
| 31 #include "tree-flow.h" | |
| 32 #include "tree-dump.h" | |
| 33 #include "tree-pass.h" | |
| 34 #include "timevar.h" | |
| 35 #include "cfgloop.h" | |
| 36 #include "tree-inline.h" | |
| 37 #include "flags.h" | |
| 38 #include "tree-inline.h" | |
| 39 | |
| 40 /* Duplicates headers of loops if they are small enough, so that the statements | |
| 41 in the loop body are always executed when the loop is entered. This | |
| 42 increases effectiveness of code motion optimizations, and reduces the need | |
| 43 for loop preconditioning. */ | |
| 44 | |
| 45 /* Check whether we should duplicate HEADER of LOOP. At most *LIMIT | |
| 46 instructions should be duplicated, limit is decreased by the actual | |
| 47 amount. */ | |
| 48 | |
| 49 static bool | |
| 50 should_duplicate_loop_header_p (basic_block header, struct loop *loop, | |
| 51 int *limit) | |
| 52 { | |
| 53 gimple_stmt_iterator bsi; | |
| 54 gimple last; | |
| 55 | |
| 56 /* Do not copy one block more than once (we do not really want to do | |
| 57 loop peeling here). */ | |
| 58 if (header->aux) | |
| 59 return false; | |
| 60 | |
| 61 /* Loop header copying usually increases size of the code. This used not to | |
| 62 be true, since quite often it is possible to verify that the condition is | |
| 63 satisfied in the first iteration and therefore to eliminate it. Jump | |
| 64 threading handles these cases now. */ | |
| 65 if (optimize_loop_for_size_p (loop)) | |
| 66 return false; | |
| 67 | |
| 68 gcc_assert (EDGE_COUNT (header->succs) > 0); | |
| 69 if (single_succ_p (header)) | |
| 70 return false; | |
| 71 if (flow_bb_inside_loop_p (loop, EDGE_SUCC (header, 0)->dest) | |
| 72 && flow_bb_inside_loop_p (loop, EDGE_SUCC (header, 1)->dest)) | |
| 73 return false; | |
| 74 | |
| 75 /* If this is not the original loop header, we want it to have just | |
| 76 one predecessor in order to match the && pattern. */ | |
| 77 if (header != loop->header && !single_pred_p (header)) | |
| 78 return false; | |
| 79 | |
| 80 last = last_stmt (header); | |
| 81 if (gimple_code (last) != GIMPLE_COND) | |
| 82 return false; | |
| 83 | |
| 84 /* Approximately copy the conditions that used to be used in jump.c -- | |
| 85 at most 20 insns and no calls. */ | |
| 86 for (bsi = gsi_start_bb (header); !gsi_end_p (bsi); gsi_next (&bsi)) | |
| 87 { | |
| 88 last = gsi_stmt (bsi); | |
| 89 | |
| 90 if (gimple_code (last) == GIMPLE_LABEL) | |
| 91 continue; | |
| 92 | |
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93 if (is_gimple_debug (last)) |
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94 continue; |
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77e2b8dfacca
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ryoma <e075725@ie.u-ryukyu.ac.jp>
parents:
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95 |
| 0 | 96 if (is_gimple_call (last)) |
| 97 return false; | |
| 98 | |
| 99 *limit -= estimate_num_insns (last, &eni_size_weights); | |
| 100 if (*limit < 0) | |
| 101 return false; | |
| 102 } | |
| 103 | |
| 104 return true; | |
| 105 } | |
| 106 | |
| 107 /* Checks whether LOOP is a do-while style loop. */ | |
| 108 | |
| 109 static bool | |
| 110 do_while_loop_p (struct loop *loop) | |
| 111 { | |
| 112 gimple stmt = last_stmt (loop->latch); | |
| 113 | |
| 114 /* If the latch of the loop is not empty, it is not a do-while loop. */ | |
| 115 if (stmt | |
| 116 && gimple_code (stmt) != GIMPLE_LABEL) | |
| 117 return false; | |
| 118 | |
| 119 /* If the header contains just a condition, it is not a do-while loop. */ | |
| 120 stmt = last_and_only_stmt (loop->header); | |
| 121 if (stmt | |
| 122 && gimple_code (stmt) == GIMPLE_COND) | |
| 123 return false; | |
| 124 | |
| 125 return true; | |
| 126 } | |
| 127 | |
| 128 /* For all loops, copy the condition at the end of the loop body in front | |
| 129 of the loop. This is beneficial since it increases efficiency of | |
| 130 code motion optimizations. It also saves one jump on entry to the loop. */ | |
| 131 | |
| 132 static unsigned int | |
| 133 copy_loop_headers (void) | |
| 134 { | |
| 135 loop_iterator li; | |
| 136 struct loop *loop; | |
| 137 basic_block header; | |
| 138 edge exit, entry; | |
| 139 basic_block *bbs, *copied_bbs; | |
| 140 unsigned n_bbs; | |
| 141 unsigned bbs_size; | |
| 142 | |
| 143 loop_optimizer_init (LOOPS_HAVE_PREHEADERS | |
| 144 | LOOPS_HAVE_SIMPLE_LATCHES); | |
| 145 if (number_of_loops () <= 1) | |
| 146 { | |
| 147 loop_optimizer_finalize (); | |
| 148 return 0; | |
| 149 } | |
| 150 | |
| 151 #ifdef ENABLE_CHECKING | |
| 152 verify_loop_structure (); | |
| 153 #endif | |
| 154 | |
| 155 bbs = XNEWVEC (basic_block, n_basic_blocks); | |
| 156 copied_bbs = XNEWVEC (basic_block, n_basic_blocks); | |
| 157 bbs_size = n_basic_blocks; | |
| 158 | |
| 159 FOR_EACH_LOOP (li, loop, 0) | |
| 160 { | |
| 161 /* Copy at most 20 insns. */ | |
| 162 int limit = 20; | |
| 163 | |
| 164 header = loop->header; | |
| 165 | |
| 166 /* If the loop is already a do-while style one (either because it was | |
| 167 written as such, or because jump threading transformed it into one), | |
| 168 we might be in fact peeling the first iteration of the loop. This | |
| 169 in general is not a good idea. */ | |
| 170 if (do_while_loop_p (loop)) | |
| 171 continue; | |
| 172 | |
| 173 /* Iterate the header copying up to limit; this takes care of the cases | |
| 174 like while (a && b) {...}, where we want to have both of the conditions | |
| 175 copied. TODO -- handle while (a || b) - like cases, by not requiring | |
| 176 the header to have just a single successor and copying up to | |
| 177 postdominator. */ | |
| 178 | |
| 179 exit = NULL; | |
| 180 n_bbs = 0; | |
| 181 while (should_duplicate_loop_header_p (header, loop, &limit)) | |
| 182 { | |
| 183 /* Find a successor of header that is inside a loop; i.e. the new | |
| 184 header after the condition is copied. */ | |
| 185 if (flow_bb_inside_loop_p (loop, EDGE_SUCC (header, 0)->dest)) | |
| 186 exit = EDGE_SUCC (header, 0); | |
| 187 else | |
| 188 exit = EDGE_SUCC (header, 1); | |
| 189 bbs[n_bbs++] = header; | |
| 190 gcc_assert (bbs_size > n_bbs); | |
| 191 header = exit->dest; | |
| 192 } | |
| 193 | |
| 194 if (!exit) | |
| 195 continue; | |
| 196 | |
| 197 if (dump_file && (dump_flags & TDF_DETAILS)) | |
| 198 fprintf (dump_file, | |
| 199 "Duplicating header of the loop %d up to edge %d->%d.\n", | |
| 200 loop->num, exit->src->index, exit->dest->index); | |
| 201 | |
| 202 /* Ensure that the header will have just the latch as a predecessor | |
| 203 inside the loop. */ | |
| 204 if (!single_pred_p (exit->dest)) | |
| 205 exit = single_pred_edge (split_edge (exit)); | |
| 206 | |
| 207 entry = loop_preheader_edge (loop); | |
| 208 | |
| 209 if (!gimple_duplicate_sese_region (entry, exit, bbs, n_bbs, copied_bbs)) | |
| 210 { | |
| 211 fprintf (dump_file, "Duplication failed.\n"); | |
| 212 continue; | |
| 213 } | |
| 214 | |
| 215 /* If the loop has the form "for (i = j; i < j + 10; i++)" then | |
| 216 this copying can introduce a case where we rely on undefined | |
| 217 signed overflow to eliminate the preheader condition, because | |
| 218 we assume that "j < j + 10" is true. We don't want to warn | |
| 219 about that case for -Wstrict-overflow, because in general we | |
| 220 don't warn about overflow involving loops. Prevent the | |
| 221 warning by setting the no_warning flag in the condition. */ | |
| 222 if (warn_strict_overflow > 0) | |
| 223 { | |
| 224 unsigned int i; | |
| 225 | |
| 226 for (i = 0; i < n_bbs; ++i) | |
| 227 { | |
| 228 gimple_stmt_iterator bsi; | |
| 229 | |
| 230 for (bsi = gsi_start_bb (copied_bbs[i]); | |
| 231 !gsi_end_p (bsi); | |
| 232 gsi_next (&bsi)) | |
| 233 { | |
| 234 gimple stmt = gsi_stmt (bsi); | |
| 235 if (gimple_code (stmt) == GIMPLE_COND) | |
| 236 gimple_set_no_warning (stmt, true); | |
| 237 else if (is_gimple_assign (stmt)) | |
| 238 { | |
| 239 enum tree_code rhs_code = gimple_assign_rhs_code (stmt); | |
| 240 if (TREE_CODE_CLASS (rhs_code) == tcc_comparison) | |
| 241 gimple_set_no_warning (stmt, true); | |
| 242 } | |
| 243 } | |
| 244 } | |
| 245 } | |
| 246 | |
| 247 /* Ensure that the latch and the preheader is simple (we know that they | |
| 248 are not now, since there was the loop exit condition. */ | |
| 249 split_edge (loop_preheader_edge (loop)); | |
| 250 split_edge (loop_latch_edge (loop)); | |
| 251 } | |
| 252 | |
| 253 free (bbs); | |
| 254 free (copied_bbs); | |
| 255 | |
| 256 loop_optimizer_finalize (); | |
| 257 return 0; | |
| 258 } | |
| 259 | |
| 260 static bool | |
| 261 gate_ch (void) | |
| 262 { | |
| 263 return flag_tree_ch != 0; | |
| 264 } | |
| 265 | |
|
55
77e2b8dfacca
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ryoma <e075725@ie.u-ryukyu.ac.jp>
parents:
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diff
changeset
|
266 struct gimple_opt_pass pass_ch = |
| 0 | 267 { |
| 268 { | |
| 269 GIMPLE_PASS, | |
| 270 "ch", /* name */ | |
| 271 gate_ch, /* gate */ | |
| 272 copy_loop_headers, /* execute */ | |
| 273 NULL, /* sub */ | |
| 274 NULL, /* next */ | |
| 275 0, /* static_pass_number */ | |
| 276 TV_TREE_CH, /* tv_id */ | |
| 277 PROP_cfg | PROP_ssa, /* properties_required */ | |
| 278 0, /* properties_provided */ | |
| 279 0, /* properties_destroyed */ | |
| 280 0, /* todo_flags_start */ | |
|
55
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ryoma <e075725@ie.u-ryukyu.ac.jp>
parents:
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diff
changeset
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281 TODO_cleanup_cfg | TODO_dump_func |
| 0 | 282 | TODO_verify_ssa /* todo_flags_finish */ |
| 283 } | |
| 284 }; |