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78b7a675 | 1 | /* Lower GIMPLE_SWITCH expressions to something more efficient than |
2 | a jump table. | |
3 | Copyright (C) 2006, 2008, 2009, 2010, 2011, 2012 | |
4 | Free Software Foundation, Inc. | |
a347af29 | 5 | |
6 | This file is part of GCC. | |
7 | ||
8 | GCC is free software; you can redistribute it and/or modify it | |
9 | under the terms of the GNU General Public License as published by the | |
10 | Free Software Foundation; either version 3, or (at your option) any | |
11 | later version. | |
12 | ||
13 | GCC is distributed in the hope that it will be useful, but WITHOUT | |
14 | ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or | |
15 | FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License | |
16 | for more details. | |
17 | ||
18 | You should have received a copy of the GNU General Public License | |
19 | along with GCC; see the file COPYING3. If not, write to the Free | |
20 | Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA | |
21 | 02110-1301, USA. */ | |
22 | ||
78b7a675 | 23 | /* This file handles the lowering of GIMPLE_SWITCH to an indexed |
24 | load, or a series of bit-test-and-branch expressions. */ | |
25 | ||
26 | #include "config.h" | |
27 | #include "system.h" | |
28 | #include "coretypes.h" | |
29 | #include "tm.h" | |
30 | #include "line-map.h" | |
31 | #include "params.h" | |
32 | #include "flags.h" | |
33 | #include "tree.h" | |
34 | #include "basic-block.h" | |
35 | #include "tree-flow.h" | |
36 | #include "tree-flow-inline.h" | |
37 | #include "tree-ssa-operands.h" | |
38 | #include "tree-pass.h" | |
39 | #include "gimple-pretty-print.h" | |
b9ed1410 | 40 | |
41 | /* ??? For lang_hooks.types.type_for_mode, but is there a word_mode | |
42 | type in the GIMPLE type system that is language-independent? */ | |
78b7a675 | 43 | #include "langhooks.h" |
44 | ||
45 | /* Need to include expr.h and optabs.h for lshift_cheap_p. */ | |
46 | #include "expr.h" | |
47 | #include "optabs.h" | |
48 | \f | |
49 | /* Maximum number of case bit tests. | |
50 | FIXME: This should be derived from PARAM_CASE_VALUES_THRESHOLD and | |
51 | targetm.case_values_threshold(), or be its own param. */ | |
52 | #define MAX_CASE_BIT_TESTS 3 | |
53 | ||
54 | /* Split the basic block at the statement pointed to by GSIP, and insert | |
55 | a branch to the target basic block of E_TRUE conditional on tree | |
56 | expression COND. | |
57 | ||
58 | It is assumed that there is already an edge from the to-be-split | |
59 | basic block to E_TRUE->dest block. This edge is removed, and the | |
60 | profile information on the edge is re-used for the new conditional | |
61 | jump. | |
62 | ||
63 | The CFG is updated. The dominator tree will not be valid after | |
64 | this transformation, but the immediate dominators are updated if | |
65 | UPDATE_DOMINATORS is true. | |
66 | ||
67 | Returns the newly created basic block. */ | |
68 | ||
69 | static basic_block | |
70 | hoist_edge_and_branch_if_true (gimple_stmt_iterator *gsip, | |
71 | tree cond, edge e_true, | |
72 | bool update_dominators) | |
73 | { | |
74 | tree tmp; | |
75 | gimple cond_stmt; | |
76 | edge e_false; | |
77 | basic_block new_bb, split_bb = gsi_bb (*gsip); | |
78 | bool dominated_e_true = false; | |
79 | ||
80 | gcc_assert (e_true->src == split_bb); | |
81 | ||
82 | if (update_dominators | |
83 | && get_immediate_dominator (CDI_DOMINATORS, e_true->dest) == split_bb) | |
84 | dominated_e_true = true; | |
85 | ||
86 | tmp = force_gimple_operand_gsi (gsip, cond, /*simple=*/true, NULL, | |
87 | /*before=*/true, GSI_SAME_STMT); | |
88 | cond_stmt = gimple_build_cond_from_tree (tmp, NULL_TREE, NULL_TREE); | |
89 | gsi_insert_before (gsip, cond_stmt, GSI_SAME_STMT); | |
90 | ||
91 | e_false = split_block (split_bb, cond_stmt); | |
92 | new_bb = e_false->dest; | |
93 | redirect_edge_pred (e_true, split_bb); | |
94 | ||
95 | e_true->flags &= ~EDGE_FALLTHRU; | |
96 | e_true->flags |= EDGE_TRUE_VALUE; | |
97 | ||
98 | e_false->flags &= ~EDGE_FALLTHRU; | |
99 | e_false->flags |= EDGE_FALSE_VALUE; | |
100 | e_false->probability = REG_BR_PROB_BASE - e_true->probability; | |
101 | e_false->count = split_bb->count - e_true->count; | |
102 | new_bb->count = e_false->count; | |
103 | ||
104 | if (update_dominators) | |
105 | { | |
106 | if (dominated_e_true) | |
107 | set_immediate_dominator (CDI_DOMINATORS, e_true->dest, split_bb); | |
108 | set_immediate_dominator (CDI_DOMINATORS, e_false->dest, split_bb); | |
109 | } | |
110 | ||
111 | return new_bb; | |
112 | } | |
113 | ||
114 | ||
115 | /* Determine whether "1 << x" is relatively cheap in word_mode. */ | |
116 | /* FIXME: This is the function that we need rtl.h and optabs.h for. | |
117 | This function (and similar RTL-related cost code in e.g. IVOPTS) should | |
118 | be moved to some kind of interface file for GIMPLE/RTL interactions. */ | |
119 | static bool | |
120 | lshift_cheap_p (void) | |
121 | { | |
122 | /* FIXME: This should be made target dependent via this "this_target" | |
123 | mechanism, similar to e.g. can_copy_init_p in gcse.c. */ | |
124 | static bool init[2] = {false, false}; | |
125 | static bool cheap[2] = {true, true}; | |
126 | bool speed_p; | |
127 | ||
128 | /* If the targer has no lshift in word_mode, the operation will most | |
129 | probably not be cheap. ??? Does GCC even work for such targets? */ | |
130 | if (optab_handler (ashl_optab, word_mode) == CODE_FOR_nothing) | |
131 | return false; | |
132 | ||
133 | speed_p = optimize_insn_for_speed_p (); | |
134 | ||
135 | if (!init[speed_p]) | |
136 | { | |
137 | rtx reg = gen_raw_REG (word_mode, 10000); | |
138 | int cost = set_src_cost (gen_rtx_ASHIFT (word_mode, const1_rtx, reg), | |
139 | speed_p); | |
140 | cheap[speed_p] = cost < COSTS_N_INSNS (MAX_CASE_BIT_TESTS); | |
141 | init[speed_p] = true; | |
142 | } | |
143 | ||
144 | return cheap[speed_p]; | |
145 | } | |
146 | ||
147 | /* Return true if a switch should be expanded as a bit test. | |
148 | RANGE is the difference between highest and lowest case. | |
149 | UNIQ is number of unique case node targets, not counting the default case. | |
150 | COUNT is the number of comparisons needed, not counting the default case. */ | |
151 | ||
152 | static bool | |
153 | expand_switch_using_bit_tests_p (tree range, | |
154 | unsigned int uniq, | |
155 | unsigned int count) | |
156 | { | |
157 | return (((uniq == 1 && count >= 3) | |
158 | || (uniq == 2 && count >= 5) | |
159 | || (uniq == 3 && count >= 6)) | |
160 | && lshift_cheap_p () | |
161 | && compare_tree_int (range, GET_MODE_BITSIZE (word_mode)) < 0 | |
162 | && compare_tree_int (range, 0) > 0); | |
163 | } | |
164 | \f | |
165 | /* Implement switch statements with bit tests | |
166 | ||
167 | A GIMPLE switch statement can be expanded to a short sequence of bit-wise | |
168 | comparisons. "switch(x)" is converted into "if ((1 << (x-MINVAL)) & CST)" | |
169 | where CST and MINVAL are integer constants. This is better than a series | |
170 | of compare-and-banch insns in some cases, e.g. we can implement: | |
171 | ||
172 | if ((x==4) || (x==6) || (x==9) || (x==11)) | |
173 | ||
174 | as a single bit test: | |
175 | ||
176 | if ((1<<x) & ((1<<4)|(1<<6)|(1<<9)|(1<<11))) | |
177 | ||
178 | This transformation is only applied if the number of case targets is small, | |
d8ab4f2a | 179 | if CST constains at least 3 bits, and "1 << x" is cheap. The bit tests are |
78b7a675 | 180 | performed in "word_mode". |
181 | ||
182 | The following example shows the code the transformation generates: | |
183 | ||
184 | int bar(int x) | |
185 | { | |
186 | switch (x) | |
187 | { | |
188 | case '0': case '1': case '2': case '3': case '4': | |
189 | case '5': case '6': case '7': case '8': case '9': | |
190 | case 'A': case 'B': case 'C': case 'D': case 'E': | |
191 | case 'F': | |
192 | return 1; | |
193 | } | |
194 | return 0; | |
195 | } | |
196 | ||
197 | ==> | |
198 | ||
199 | bar (int x) | |
200 | { | |
201 | tmp1 = x - 48; | |
202 | if (tmp1 > (70 - 48)) goto L2; | |
203 | tmp2 = 1 << tmp1; | |
204 | tmp3 = 0b11111100000001111111111; | |
205 | if ((tmp2 & tmp3) != 0) goto L1 ; else goto L2; | |
206 | L1: | |
207 | return 1; | |
208 | L2: | |
209 | return 0; | |
210 | } | |
211 | ||
212 | TODO: There are still some improvements to this transformation that could | |
213 | be implemented: | |
214 | ||
215 | * A narrower mode than word_mode could be used if that is cheaper, e.g. | |
216 | for x86_64 where a narrower-mode shift may result in smaller code. | |
217 | ||
218 | * The compounded constant could be shifted rather than the one. The | |
219 | test would be either on the sign bit or on the least significant bit, | |
220 | depending on the direction of the shift. On some machines, the test | |
221 | for the branch would be free if the bit to test is already set by the | |
222 | shift operation. | |
223 | ||
224 | This transformation was contributed by Roger Sayle, see this e-mail: | |
225 | http://gcc.gnu.org/ml/gcc-patches/2003-01/msg01950.html | |
226 | */ | |
227 | ||
228 | /* A case_bit_test represents a set of case nodes that may be | |
229 | selected from using a bit-wise comparison. HI and LO hold | |
230 | the integer to be tested against, TARGET_EDGE contains the | |
231 | edge to the basic block to jump to upon success and BITS | |
232 | counts the number of case nodes handled by this test, | |
233 | typically the number of bits set in HI:LO. The LABEL field | |
234 | is used to quickly identify all cases in this set without | |
235 | looking at label_to_block for every case label. */ | |
236 | ||
237 | struct case_bit_test | |
238 | { | |
239 | HOST_WIDE_INT hi; | |
240 | HOST_WIDE_INT lo; | |
241 | edge target_edge; | |
242 | tree label; | |
243 | int bits; | |
244 | }; | |
245 | ||
246 | /* Comparison function for qsort to order bit tests by decreasing | |
247 | probability of execution. Our best guess comes from a measured | |
248 | profile. If the profile counts are equal, break even on the | |
249 | number of case nodes, i.e. the node with the most cases gets | |
250 | tested first. | |
251 | ||
252 | TODO: Actually this currently runs before a profile is available. | |
253 | Therefore the case-as-bit-tests transformation should be done | |
254 | later in the pass pipeline, or something along the lines of | |
255 | "Efficient and effective branch reordering using profile data" | |
256 | (Yang et. al., 2002) should be implemented (although, how good | |
257 | is a paper is called "Efficient and effective ..." when the | |
258 | latter is implied by the former, but oh well...). */ | |
259 | ||
260 | static int | |
261 | case_bit_test_cmp (const void *p1, const void *p2) | |
262 | { | |
263 | const struct case_bit_test *const d1 = (const struct case_bit_test *) p1; | |
264 | const struct case_bit_test *const d2 = (const struct case_bit_test *) p2; | |
265 | ||
266 | if (d2->target_edge->count != d1->target_edge->count) | |
267 | return d2->target_edge->count - d1->target_edge->count; | |
268 | if (d2->bits != d1->bits) | |
269 | return d2->bits - d1->bits; | |
270 | ||
271 | /* Stabilize the sort. */ | |
272 | return LABEL_DECL_UID (d2->label) - LABEL_DECL_UID (d1->label); | |
273 | } | |
274 | ||
275 | /* Expand a switch statement by a short sequence of bit-wise | |
276 | comparisons. "switch(x)" is effectively converted into | |
277 | "if ((1 << (x-MINVAL)) & CST)" where CST and MINVAL are | |
278 | integer constants. | |
279 | ||
280 | INDEX_EXPR is the value being switched on. | |
281 | ||
282 | MINVAL is the lowest case value of in the case nodes, | |
283 | and RANGE is highest value minus MINVAL. MINVAL and RANGE | |
284 | are not guaranteed to be of the same type as INDEX_EXPR | |
285 | (the gimplifier doesn't change the type of case label values, | |
286 | and MINVAL and RANGE are derived from those values). | |
287 | ||
288 | There *MUST* be MAX_CASE_BIT_TESTS or less unique case | |
289 | node targets. */ | |
290 | ||
291 | static void | |
292 | emit_case_bit_tests (gimple swtch, tree index_expr, | |
293 | tree minval, tree range) | |
294 | { | |
295 | struct case_bit_test test[MAX_CASE_BIT_TESTS]; | |
296 | unsigned int i, j, k; | |
297 | unsigned int count; | |
298 | ||
299 | basic_block switch_bb = gimple_bb (swtch); | |
300 | basic_block default_bb, new_default_bb, new_bb; | |
301 | edge default_edge; | |
302 | bool update_dom = dom_info_available_p (CDI_DOMINATORS); | |
303 | ||
304 | VEC (basic_block, heap) *bbs_to_fix_dom = NULL; | |
305 | ||
306 | tree index_type = TREE_TYPE (index_expr); | |
307 | tree unsigned_index_type = unsigned_type_for (index_type); | |
308 | unsigned int branch_num = gimple_switch_num_labels (swtch); | |
309 | ||
310 | gimple_stmt_iterator gsi; | |
311 | gimple shift_stmt; | |
312 | ||
313 | tree idx, tmp, csui; | |
314 | tree word_type_node = lang_hooks.types.type_for_mode (word_mode, 1); | |
315 | tree word_mode_zero = fold_convert (word_type_node, integer_zero_node); | |
316 | tree word_mode_one = fold_convert (word_type_node, integer_one_node); | |
317 | ||
318 | memset (&test, 0, sizeof (test)); | |
319 | ||
320 | /* Get the edge for the default case. */ | |
49a70175 | 321 | tmp = gimple_switch_default_label (swtch); |
78b7a675 | 322 | default_bb = label_to_block (CASE_LABEL (tmp)); |
323 | default_edge = find_edge (switch_bb, default_bb); | |
324 | ||
325 | /* Go through all case labels, and collect the case labels, profile | |
326 | counts, and other information we need to build the branch tests. */ | |
327 | count = 0; | |
328 | for (i = 1; i < branch_num; i++) | |
329 | { | |
330 | unsigned int lo, hi; | |
331 | tree cs = gimple_switch_label (swtch, i); | |
332 | tree label = CASE_LABEL (cs); | |
3a7ac8c6 | 333 | edge e = find_edge (switch_bb, label_to_block (label)); |
78b7a675 | 334 | for (k = 0; k < count; k++) |
3a7ac8c6 | 335 | if (e == test[k].target_edge) |
78b7a675 | 336 | break; |
337 | ||
338 | if (k == count) | |
339 | { | |
78b7a675 | 340 | gcc_checking_assert (count < MAX_CASE_BIT_TESTS); |
341 | test[k].hi = 0; | |
342 | test[k].lo = 0; | |
343 | test[k].target_edge = e; | |
344 | test[k].label = label; | |
345 | test[k].bits = 1; | |
346 | count++; | |
347 | } | |
348 | else | |
349 | test[k].bits++; | |
350 | ||
351 | lo = tree_low_cst (int_const_binop (MINUS_EXPR, | |
352 | CASE_LOW (cs), minval), | |
353 | 1); | |
354 | if (CASE_HIGH (cs) == NULL_TREE) | |
355 | hi = lo; | |
356 | else | |
357 | hi = tree_low_cst (int_const_binop (MINUS_EXPR, | |
358 | CASE_HIGH (cs), minval), | |
359 | 1); | |
360 | ||
361 | for (j = lo; j <= hi; j++) | |
362 | if (j >= HOST_BITS_PER_WIDE_INT) | |
363 | test[k].hi |= (HOST_WIDE_INT) 1 << (j - HOST_BITS_PER_INT); | |
364 | else | |
365 | test[k].lo |= (HOST_WIDE_INT) 1 << j; | |
366 | } | |
367 | ||
368 | qsort (test, count, sizeof(*test), case_bit_test_cmp); | |
369 | ||
370 | /* We generate two jumps to the default case label. | |
371 | Split the default edge, so that we don't have to do any PHI node | |
372 | updating. */ | |
373 | new_default_bb = split_edge (default_edge); | |
374 | ||
375 | if (update_dom) | |
376 | { | |
377 | bbs_to_fix_dom = VEC_alloc (basic_block, heap, 10); | |
378 | VEC_quick_push (basic_block, bbs_to_fix_dom, switch_bb); | |
379 | VEC_quick_push (basic_block, bbs_to_fix_dom, default_bb); | |
380 | VEC_quick_push (basic_block, bbs_to_fix_dom, new_default_bb); | |
381 | } | |
382 | ||
383 | /* Now build the test-and-branch code. */ | |
384 | ||
385 | gsi = gsi_last_bb (switch_bb); | |
386 | ||
9e394672 | 387 | /* idx = (unsigned)x - minval. */ |
388 | idx = fold_convert (unsigned_index_type, index_expr); | |
389 | idx = fold_build2 (MINUS_EXPR, unsigned_index_type, idx, | |
390 | fold_convert (unsigned_index_type, minval)); | |
78b7a675 | 391 | idx = force_gimple_operand_gsi (&gsi, idx, |
392 | /*simple=*/true, NULL_TREE, | |
393 | /*before=*/true, GSI_SAME_STMT); | |
394 | ||
395 | /* if (idx > range) goto default */ | |
396 | range = force_gimple_operand_gsi (&gsi, | |
397 | fold_convert (unsigned_index_type, range), | |
398 | /*simple=*/true, NULL_TREE, | |
399 | /*before=*/true, GSI_SAME_STMT); | |
400 | tmp = fold_build2 (GT_EXPR, boolean_type_node, idx, range); | |
401 | new_bb = hoist_edge_and_branch_if_true (&gsi, tmp, default_edge, update_dom); | |
402 | if (update_dom) | |
403 | VEC_quick_push (basic_block, bbs_to_fix_dom, new_bb); | |
404 | gcc_assert (gimple_bb (swtch) == new_bb); | |
405 | gsi = gsi_last_bb (new_bb); | |
406 | ||
407 | /* Any blocks dominated by the GIMPLE_SWITCH, but that are not successors | |
408 | of NEW_BB, are still immediately dominated by SWITCH_BB. Make it so. */ | |
409 | if (update_dom) | |
410 | { | |
411 | VEC (basic_block, heap) *dom_bbs; | |
412 | basic_block dom_son; | |
413 | ||
414 | dom_bbs = get_dominated_by (CDI_DOMINATORS, new_bb); | |
415 | FOR_EACH_VEC_ELT (basic_block, dom_bbs, i, dom_son) | |
416 | { | |
417 | edge e = find_edge (new_bb, dom_son); | |
418 | if (e && single_pred_p (e->dest)) | |
419 | continue; | |
420 | set_immediate_dominator (CDI_DOMINATORS, dom_son, switch_bb); | |
421 | VEC_safe_push (basic_block, heap, bbs_to_fix_dom, dom_son); | |
422 | } | |
423 | VEC_free (basic_block, heap, dom_bbs); | |
424 | } | |
425 | ||
426 | /* csui = (1 << (word_mode) idx) */ | |
03d37e4e | 427 | csui = make_ssa_name (word_type_node, NULL); |
78b7a675 | 428 | tmp = fold_build2 (LSHIFT_EXPR, word_type_node, word_mode_one, |
429 | fold_convert (word_type_node, idx)); | |
430 | tmp = force_gimple_operand_gsi (&gsi, tmp, | |
431 | /*simple=*/false, NULL_TREE, | |
432 | /*before=*/true, GSI_SAME_STMT); | |
433 | shift_stmt = gimple_build_assign (csui, tmp); | |
78b7a675 | 434 | gsi_insert_before (&gsi, shift_stmt, GSI_SAME_STMT); |
435 | update_stmt (shift_stmt); | |
436 | ||
437 | /* for each unique set of cases: | |
438 | if (const & csui) goto target */ | |
439 | for (k = 0; k < count; k++) | |
440 | { | |
441 | tmp = build_int_cst_wide (word_type_node, test[k].lo, test[k].hi); | |
442 | tmp = fold_build2 (BIT_AND_EXPR, word_type_node, csui, tmp); | |
443 | tmp = force_gimple_operand_gsi (&gsi, tmp, | |
444 | /*simple=*/true, NULL_TREE, | |
445 | /*before=*/true, GSI_SAME_STMT); | |
446 | tmp = fold_build2 (NE_EXPR, boolean_type_node, tmp, word_mode_zero); | |
447 | new_bb = hoist_edge_and_branch_if_true (&gsi, tmp, test[k].target_edge, | |
448 | update_dom); | |
449 | if (update_dom) | |
450 | VEC_safe_push (basic_block, heap, bbs_to_fix_dom, new_bb); | |
451 | gcc_assert (gimple_bb (swtch) == new_bb); | |
452 | gsi = gsi_last_bb (new_bb); | |
453 | } | |
454 | ||
455 | /* We should have removed all edges now. */ | |
456 | gcc_assert (EDGE_COUNT (gsi_bb (gsi)->succs) == 0); | |
457 | ||
458 | /* If nothing matched, go to the default label. */ | |
459 | make_edge (gsi_bb (gsi), new_default_bb, EDGE_FALLTHRU); | |
460 | ||
461 | /* The GIMPLE_SWITCH is now redundant. */ | |
462 | gsi_remove (&gsi, true); | |
463 | ||
464 | if (update_dom) | |
465 | { | |
466 | /* Fix up the dominator tree. */ | |
467 | iterate_fix_dominators (CDI_DOMINATORS, bbs_to_fix_dom, true); | |
468 | VEC_free (basic_block, heap, bbs_to_fix_dom); | |
469 | } | |
470 | } | |
471 | \f | |
a347af29 | 472 | /* |
473 | Switch initialization conversion | |
474 | ||
475 | The following pass changes simple initializations of scalars in a switch | |
5d459527 | 476 | statement into initializations from a static array. Obviously, the values |
477 | must be constant and known at compile time and a default branch must be | |
a347af29 | 478 | provided. For example, the following code: |
479 | ||
480 | int a,b; | |
481 | ||
482 | switch (argc) | |
483 | { | |
484 | case 1: | |
485 | case 2: | |
486 | a_1 = 8; | |
487 | b_1 = 6; | |
488 | break; | |
489 | case 3: | |
490 | a_2 = 9; | |
491 | b_2 = 5; | |
492 | break; | |
493 | case 12: | |
494 | a_3 = 10; | |
495 | b_3 = 4; | |
496 | break; | |
497 | default: | |
498 | a_4 = 16; | |
499 | b_4 = 1; | |
11f2f313 | 500 | break; |
a347af29 | 501 | } |
502 | a_5 = PHI <a_1, a_2, a_3, a_4> | |
503 | b_5 = PHI <b_1, b_2, b_3, b_4> | |
504 | ||
505 | ||
506 | is changed into: | |
507 | ||
508 | static const int = CSWTCH01[] = {6, 6, 5, 1, 1, 1, 1, 1, 1, 1, 1, 4}; | |
509 | static const int = CSWTCH02[] = {8, 8, 9, 16, 16, 16, 16, 16, 16, 16, | |
510 | 16, 16, 10}; | |
511 | ||
512 | if (((unsigned) argc) - 1 < 11) | |
513 | { | |
514 | a_6 = CSWTCH02[argc - 1]; | |
515 | b_6 = CSWTCH01[argc - 1]; | |
516 | } | |
517 | else | |
518 | { | |
519 | a_7 = 16; | |
520 | b_7 = 1; | |
521 | } | |
11f2f313 | 522 | a_5 = PHI <a_6, a_7> |
523 | b_b = PHI <b_6, b_7> | |
a347af29 | 524 | |
525 | There are further constraints. Specifically, the range of values across all | |
526 | case labels must not be bigger than SWITCH_CONVERSION_BRANCH_RATIO (default | |
78b7a675 | 527 | eight) times the number of the actual switch branches. |
a347af29 | 528 | |
78b7a675 | 529 | This transformation was contributed by Martin Jambor, see this e-mail: |
530 | http://gcc.gnu.org/ml/gcc-patches/2008-07/msg00011.html */ | |
a347af29 | 531 | |
532 | /* The main structure of the pass. */ | |
533 | struct switch_conv_info | |
534 | { | |
11f2f313 | 535 | /* The expression used to decide the switch branch. */ |
a347af29 | 536 | tree index_expr; |
537 | ||
11f2f313 | 538 | /* The following integer constants store the minimum and maximum value |
539 | covered by the case labels. */ | |
a347af29 | 540 | tree range_min; |
11f2f313 | 541 | tree range_max; |
a347af29 | 542 | |
11f2f313 | 543 | /* The difference between the above two numbers. Stored here because it |
544 | is used in all the conversion heuristics, as well as for some of the | |
545 | transformation, and it is expensive to re-compute it all the time. */ | |
a347af29 | 546 | tree range_size; |
547 | ||
11f2f313 | 548 | /* Basic block that contains the actual GIMPLE_SWITCH. */ |
a347af29 | 549 | basic_block switch_bb; |
550 | ||
11f2f313 | 551 | /* Basic block that is the target of the default case. */ |
552 | basic_block default_bb; | |
553 | ||
554 | /* The single successor block of all branches out of the GIMPLE_SWITCH, | |
555 | if such a block exists. Otherwise NULL. */ | |
a347af29 | 556 | basic_block final_bb; |
557 | ||
11f2f313 | 558 | /* The probability of the default edge in the replaced switch. */ |
559 | int default_prob; | |
560 | ||
561 | /* The count of the default edge in the replaced switch. */ | |
562 | gcov_type default_count; | |
563 | ||
564 | /* Combined count of all other (non-default) edges in the replaced switch. */ | |
565 | gcov_type other_count; | |
566 | ||
a347af29 | 567 | /* Number of phi nodes in the final bb (that we'll be replacing). */ |
568 | int phi_count; | |
569 | ||
cc17b19b | 570 | /* Array of default values, in the same order as phi nodes. */ |
a347af29 | 571 | tree *default_values; |
572 | ||
573 | /* Constructors of new static arrays. */ | |
574 | VEC (constructor_elt, gc) **constructors; | |
575 | ||
576 | /* Array of ssa names that are initialized with a value from a new static | |
577 | array. */ | |
578 | tree *target_inbound_names; | |
579 | ||
580 | /* Array of ssa names that are initialized with the default value if the | |
581 | switch expression is out of range. */ | |
582 | tree *target_outbound_names; | |
583 | ||
cc17b19b | 584 | /* The first load statement that loads a temporary from a new static array. |
585 | */ | |
75a70cf9 | 586 | gimple arr_ref_first; |
a347af29 | 587 | |
588 | /* The last load statement that loads a temporary from a new static array. */ | |
75a70cf9 | 589 | gimple arr_ref_last; |
a347af29 | 590 | |
591 | /* String reason why the case wasn't a good candidate that is written to the | |
592 | dump file, if there is one. */ | |
593 | const char *reason; | |
df2813c5 | 594 | |
595 | /* Parameters for expand_switch_using_bit_tests. Should be computed | |
596 | the same way as in expand_case. */ | |
11f2f313 | 597 | unsigned int uniq; |
598 | unsigned int count; | |
a347af29 | 599 | }; |
600 | ||
11f2f313 | 601 | /* Collect information about GIMPLE_SWITCH statement SWTCH into INFO. */ |
a347af29 | 602 | |
11f2f313 | 603 | static void |
604 | collect_switch_conv_info (gimple swtch, struct switch_conv_info *info) | |
a347af29 | 605 | { |
75a70cf9 | 606 | unsigned int branch_num = gimple_switch_num_labels (swtch); |
11f2f313 | 607 | tree min_case, max_case; |
608 | unsigned int count, i; | |
609 | edge e, e_default; | |
610 | edge_iterator ei; | |
611 | ||
612 | memset (info, 0, sizeof (*info)); | |
a347af29 | 613 | |
614 | /* The gimplifier has already sorted the cases by CASE_LOW and ensured there | |
49a70175 | 615 | is a default label which is the first in the vector. |
616 | Collect the bits we can deduce from the CFG. */ | |
11f2f313 | 617 | info->index_expr = gimple_switch_index (swtch); |
618 | info->switch_bb = gimple_bb (swtch); | |
619 | info->default_bb = | |
49a70175 | 620 | label_to_block (CASE_LABEL (gimple_switch_default_label (swtch))); |
11f2f313 | 621 | e_default = find_edge (info->switch_bb, info->default_bb); |
622 | info->default_prob = e_default->probability; | |
623 | info->default_count = e_default->count; | |
624 | FOR_EACH_EDGE (e, ei, info->switch_bb->succs) | |
625 | if (e != e_default) | |
626 | info->other_count += e->count; | |
a347af29 | 627 | |
11f2f313 | 628 | /* See if there is one common successor block for all branch |
629 | targets. If it exists, record it in FINAL_BB. */ | |
630 | FOR_EACH_EDGE (e, ei, info->switch_bb->succs) | |
631 | { | |
632 | if (! single_pred_p (e->dest)) | |
633 | { | |
634 | info->final_bb = e->dest; | |
635 | break; | |
636 | } | |
637 | } | |
638 | if (info->final_bb) | |
639 | FOR_EACH_EDGE (e, ei, info->switch_bb->succs) | |
640 | { | |
641 | if (e->dest == info->final_bb) | |
642 | continue; | |
643 | ||
644 | if (single_pred_p (e->dest) | |
645 | && single_succ_p (e->dest) | |
646 | && single_succ (e->dest) == info->final_bb) | |
647 | continue; | |
648 | ||
649 | info->final_bb = NULL; | |
650 | break; | |
651 | } | |
652 | ||
653 | /* Get upper and lower bounds of case values, and the covered range. */ | |
654 | min_case = gimple_switch_label (swtch, 1); | |
75a70cf9 | 655 | max_case = gimple_switch_label (swtch, branch_num - 1); |
11f2f313 | 656 | |
657 | info->range_min = CASE_LOW (min_case); | |
a347af29 | 658 | if (CASE_HIGH (max_case) != NULL_TREE) |
11f2f313 | 659 | info->range_max = CASE_HIGH (max_case); |
a347af29 | 660 | else |
11f2f313 | 661 | info->range_max = CASE_LOW (max_case); |
662 | ||
663 | info->range_size = | |
664 | int_const_binop (MINUS_EXPR, info->range_max, info->range_min); | |
a347af29 | 665 | |
11f2f313 | 666 | /* Get a count of the number of case labels. Single-valued case labels |
667 | simply count as one, but a case range counts double, since it may | |
668 | require two compares if it gets lowered as a branching tree. */ | |
669 | count = 0; | |
670 | for (i = 1; i < branch_num; i++) | |
671 | { | |
672 | tree elt = gimple_switch_label (swtch, i); | |
673 | count++; | |
674 | if (CASE_HIGH (elt) | |
675 | && ! tree_int_cst_equal (CASE_LOW (elt), CASE_HIGH (elt))) | |
676 | count++; | |
677 | } | |
678 | info->count = count; | |
679 | ||
680 | /* Get the number of unique non-default targets out of the GIMPLE_SWITCH | |
681 | block. Assume a CFG cleanup would have already removed degenerate | |
682 | switch statements, this allows us to just use EDGE_COUNT. */ | |
683 | info->uniq = EDGE_COUNT (gimple_bb (swtch)->succs) - 1; | |
684 | } | |
a347af29 | 685 | |
11f2f313 | 686 | /* Checks whether the range given by individual case statements of the SWTCH |
687 | switch statement isn't too big and whether the number of branches actually | |
688 | satisfies the size of the new array. */ | |
a347af29 | 689 | |
11f2f313 | 690 | static bool |
691 | check_range (struct switch_conv_info *info) | |
692 | { | |
5d459527 | 693 | gcc_assert (info->range_size); |
694 | if (!host_integerp (info->range_size, 1)) | |
a347af29 | 695 | { |
5d459527 | 696 | info->reason = "index range way too large or otherwise unusable"; |
a347af29 | 697 | return false; |
698 | } | |
699 | ||
5d459527 | 700 | if ((unsigned HOST_WIDE_INT) tree_low_cst (info->range_size, 1) |
11f2f313 | 701 | > ((unsigned) info->count * SWITCH_CONVERSION_BRANCH_RATIO)) |
a347af29 | 702 | { |
5d459527 | 703 | info->reason = "the maximum range-branch ratio exceeded"; |
a347af29 | 704 | return false; |
705 | } | |
706 | ||
707 | return true; | |
708 | } | |
709 | ||
11f2f313 | 710 | /* Checks whether all but the FINAL_BB basic blocks are empty. */ |
a347af29 | 711 | |
712 | static bool | |
11f2f313 | 713 | check_all_empty_except_final (struct switch_conv_info *info) |
a347af29 | 714 | { |
a347af29 | 715 | edge e; |
11f2f313 | 716 | edge_iterator ei; |
a347af29 | 717 | |
11f2f313 | 718 | FOR_EACH_EDGE (e, ei, info->switch_bb->succs) |
a347af29 | 719 | { |
11f2f313 | 720 | if (e->dest == info->final_bb) |
721 | continue; | |
a347af29 | 722 | |
11f2f313 | 723 | if (!empty_block_p (e->dest)) |
a347af29 | 724 | { |
5d459527 | 725 | info->reason = "bad case - a non-final BB not empty"; |
a347af29 | 726 | return false; |
727 | } | |
a347af29 | 728 | } |
729 | ||
730 | return true; | |
731 | } | |
732 | ||
733 | /* This function checks whether all required values in phi nodes in final_bb | |
734 | are constants. Required values are those that correspond to a basic block | |
735 | which is a part of the examined switch statement. It returns true if the | |
736 | phi nodes are OK, otherwise false. */ | |
737 | ||
738 | static bool | |
5d459527 | 739 | check_final_bb (struct switch_conv_info *info) |
a347af29 | 740 | { |
75a70cf9 | 741 | gimple_stmt_iterator gsi; |
a347af29 | 742 | |
5d459527 | 743 | info->phi_count = 0; |
744 | for (gsi = gsi_start_phis (info->final_bb); !gsi_end_p (gsi); gsi_next (&gsi)) | |
a347af29 | 745 | { |
75a70cf9 | 746 | gimple phi = gsi_stmt (gsi); |
747 | unsigned int i; | |
a347af29 | 748 | |
5d459527 | 749 | info->phi_count++; |
a347af29 | 750 | |
75a70cf9 | 751 | for (i = 0; i < gimple_phi_num_args (phi); i++) |
a347af29 | 752 | { |
75a70cf9 | 753 | basic_block bb = gimple_phi_arg_edge (phi, i)->src; |
a347af29 | 754 | |
5d459527 | 755 | if (bb == info->switch_bb |
756 | || (single_pred_p (bb) && single_pred (bb) == info->switch_bb)) | |
a347af29 | 757 | { |
54af7f7e | 758 | tree reloc, val; |
759 | ||
760 | val = gimple_phi_arg_def (phi, i); | |
761 | if (!is_gimple_ip_invariant (val)) | |
762 | { | |
5d459527 | 763 | info->reason = "non-invariant value from a case"; |
54af7f7e | 764 | return false; /* Non-invariant argument. */ |
765 | } | |
766 | reloc = initializer_constant_valid_p (val, TREE_TYPE (val)); | |
767 | if ((flag_pic && reloc != null_pointer_node) | |
768 | || (!flag_pic && reloc == NULL_TREE)) | |
769 | { | |
770 | if (reloc) | |
5d459527 | 771 | info->reason |
772 | = "value from a case would need runtime relocations"; | |
54af7f7e | 773 | else |
5d459527 | 774 | info->reason |
775 | = "value from a case is not a valid initializer"; | |
54af7f7e | 776 | return false; |
777 | } | |
a347af29 | 778 | } |
779 | } | |
780 | } | |
781 | ||
782 | return true; | |
783 | } | |
784 | ||
785 | /* The following function allocates default_values, target_{in,out}_names and | |
786 | constructors arrays. The last one is also populated with pointers to | |
787 | vectors that will become constructors of new arrays. */ | |
788 | ||
789 | static void | |
5d459527 | 790 | create_temp_arrays (struct switch_conv_info *info) |
a347af29 | 791 | { |
792 | int i; | |
793 | ||
5d459527 | 794 | info->default_values = XCNEWVEC (tree, info->phi_count * 3); |
795 | info->constructors = XCNEWVEC (VEC (constructor_elt, gc) *, info->phi_count); | |
796 | info->target_inbound_names = info->default_values + info->phi_count; | |
797 | info->target_outbound_names = info->target_inbound_names + info->phi_count; | |
798 | for (i = 0; i < info->phi_count; i++) | |
799 | info->constructors[i] | |
800 | = VEC_alloc (constructor_elt, gc, tree_low_cst (info->range_size, 1) + 1); | |
a347af29 | 801 | } |
802 | ||
803 | /* Free the arrays created by create_temp_arrays(). The vectors that are | |
804 | created by that function are not freed here, however, because they have | |
805 | already become constructors and must be preserved. */ | |
806 | ||
807 | static void | |
5d459527 | 808 | free_temp_arrays (struct switch_conv_info *info) |
a347af29 | 809 | { |
5d459527 | 810 | XDELETEVEC (info->constructors); |
811 | XDELETEVEC (info->default_values); | |
a347af29 | 812 | } |
813 | ||
814 | /* Populate the array of default values in the order of phi nodes. | |
815 | DEFAULT_CASE is the CASE_LABEL_EXPR for the default switch branch. */ | |
816 | ||
817 | static void | |
5d459527 | 818 | gather_default_values (tree default_case, struct switch_conv_info *info) |
a347af29 | 819 | { |
75a70cf9 | 820 | gimple_stmt_iterator gsi; |
a347af29 | 821 | basic_block bb = label_to_block (CASE_LABEL (default_case)); |
822 | edge e; | |
75a70cf9 | 823 | int i = 0; |
a347af29 | 824 | |
825 | gcc_assert (CASE_LOW (default_case) == NULL_TREE); | |
826 | ||
5d459527 | 827 | if (bb == info->final_bb) |
828 | e = find_edge (info->switch_bb, bb); | |
a347af29 | 829 | else |
830 | e = single_succ_edge (bb); | |
831 | ||
5d459527 | 832 | for (gsi = gsi_start_phis (info->final_bb); !gsi_end_p (gsi); gsi_next (&gsi)) |
a347af29 | 833 | { |
75a70cf9 | 834 | gimple phi = gsi_stmt (gsi); |
a347af29 | 835 | tree val = PHI_ARG_DEF_FROM_EDGE (phi, e); |
836 | gcc_assert (val); | |
5d459527 | 837 | info->default_values[i++] = val; |
a347af29 | 838 | } |
839 | } | |
840 | ||
841 | /* The following function populates the vectors in the constructors array with | |
842 | future contents of the static arrays. The vectors are populated in the | |
843 | order of phi nodes. SWTCH is the switch statement being converted. */ | |
844 | ||
845 | static void | |
5d459527 | 846 | build_constructors (gimple swtch, struct switch_conv_info *info) |
a347af29 | 847 | { |
75a70cf9 | 848 | unsigned i, branch_num = gimple_switch_num_labels (swtch); |
5d459527 | 849 | tree pos = info->range_min; |
a347af29 | 850 | |
75a70cf9 | 851 | for (i = 1; i < branch_num; i++) |
a347af29 | 852 | { |
75a70cf9 | 853 | tree cs = gimple_switch_label (swtch, i); |
a347af29 | 854 | basic_block bb = label_to_block (CASE_LABEL (cs)); |
855 | edge e; | |
75a70cf9 | 856 | tree high; |
857 | gimple_stmt_iterator gsi; | |
a347af29 | 858 | int j; |
859 | ||
5d459527 | 860 | if (bb == info->final_bb) |
861 | e = find_edge (info->switch_bb, bb); | |
a347af29 | 862 | else |
863 | e = single_succ_edge (bb); | |
864 | gcc_assert (e); | |
865 | ||
866 | while (tree_int_cst_lt (pos, CASE_LOW (cs))) | |
867 | { | |
868 | int k; | |
5d459527 | 869 | for (k = 0; k < info->phi_count; k++) |
a347af29 | 870 | { |
871 | constructor_elt *elt; | |
872 | ||
873 | elt = VEC_quick_push (constructor_elt, | |
5d459527 | 874 | info->constructors[k], NULL); |
75a70cf9 | 875 | elt->index = int_const_binop (MINUS_EXPR, pos, |
5d459527 | 876 | info->range_min); |
877 | elt->value = info->default_values[k]; | |
a347af29 | 878 | } |
879 | ||
317e2a67 | 880 | pos = int_const_binop (PLUS_EXPR, pos, integer_one_node); |
a347af29 | 881 | } |
cc17b19b | 882 | gcc_assert (tree_int_cst_equal (pos, CASE_LOW (cs))); |
a347af29 | 883 | |
884 | j = 0; | |
885 | if (CASE_HIGH (cs)) | |
886 | high = CASE_HIGH (cs); | |
887 | else | |
cc17b19b | 888 | high = CASE_LOW (cs); |
5d459527 | 889 | for (gsi = gsi_start_phis (info->final_bb); |
75a70cf9 | 890 | !gsi_end_p (gsi); gsi_next (&gsi)) |
a347af29 | 891 | { |
75a70cf9 | 892 | gimple phi = gsi_stmt (gsi); |
a347af29 | 893 | tree val = PHI_ARG_DEF_FROM_EDGE (phi, e); |
7558c999 | 894 | tree low = CASE_LOW (cs); |
a347af29 | 895 | pos = CASE_LOW (cs); |
896 | ||
48e1416a | 897 | do |
a347af29 | 898 | { |
899 | constructor_elt *elt; | |
900 | ||
901 | elt = VEC_quick_push (constructor_elt, | |
5d459527 | 902 | info->constructors[j], NULL); |
903 | elt->index = int_const_binop (MINUS_EXPR, pos, info->range_min); | |
a347af29 | 904 | elt->value = val; |
905 | ||
317e2a67 | 906 | pos = int_const_binop (PLUS_EXPR, pos, integer_one_node); |
f6ac75a7 | 907 | } while (!tree_int_cst_lt (high, pos) |
908 | && tree_int_cst_lt (low, pos)); | |
a347af29 | 909 | j++; |
910 | } | |
911 | } | |
912 | } | |
913 | ||
f6ac75a7 | 914 | /* If all values in the constructor vector are the same, return the value. |
915 | Otherwise return NULL_TREE. Not supposed to be called for empty | |
916 | vectors. */ | |
917 | ||
918 | static tree | |
919 | constructor_contains_same_values_p (VEC (constructor_elt, gc) *vec) | |
920 | { | |
df2813c5 | 921 | unsigned int i; |
f6ac75a7 | 922 | tree prev = NULL_TREE; |
df2813c5 | 923 | constructor_elt *elt; |
f6ac75a7 | 924 | |
df2813c5 | 925 | FOR_EACH_VEC_ELT (constructor_elt, vec, i, elt) |
f6ac75a7 | 926 | { |
f6ac75a7 | 927 | if (!prev) |
928 | prev = elt->value; | |
929 | else if (!operand_equal_p (elt->value, prev, OEP_ONLY_CONST)) | |
930 | return NULL_TREE; | |
931 | } | |
932 | return prev; | |
933 | } | |
934 | ||
df2813c5 | 935 | /* Return type which should be used for array elements, either TYPE, |
936 | or for integral type some smaller integral type that can still hold | |
937 | all the constants. */ | |
938 | ||
939 | static tree | |
5d459527 | 940 | array_value_type (gimple swtch, tree type, int num, |
941 | struct switch_conv_info *info) | |
df2813c5 | 942 | { |
5d459527 | 943 | unsigned int i, len = VEC_length (constructor_elt, info->constructors[num]); |
df2813c5 | 944 | constructor_elt *elt; |
945 | enum machine_mode mode; | |
946 | int sign = 0; | |
947 | tree smaller_type; | |
948 | ||
949 | if (!INTEGRAL_TYPE_P (type)) | |
950 | return type; | |
951 | ||
952 | mode = GET_CLASS_NARROWEST_MODE (GET_MODE_CLASS (TYPE_MODE (type))); | |
953 | if (GET_MODE_SIZE (TYPE_MODE (type)) <= GET_MODE_SIZE (mode)) | |
954 | return type; | |
955 | ||
956 | if (len < (optimize_bb_for_size_p (gimple_bb (swtch)) ? 2 : 32)) | |
957 | return type; | |
958 | ||
5d459527 | 959 | FOR_EACH_VEC_ELT (constructor_elt, info->constructors[num], i, elt) |
df2813c5 | 960 | { |
961 | double_int cst; | |
962 | ||
963 | if (TREE_CODE (elt->value) != INTEGER_CST) | |
964 | return type; | |
965 | ||
966 | cst = TREE_INT_CST (elt->value); | |
967 | while (1) | |
968 | { | |
969 | unsigned int prec = GET_MODE_BITSIZE (mode); | |
970 | if (prec > HOST_BITS_PER_WIDE_INT) | |
971 | return type; | |
972 | ||
cf8f0e63 | 973 | if (sign >= 0 && cst == cst.zext (prec)) |
df2813c5 | 974 | { |
cf8f0e63 | 975 | if (sign == 0 && cst == cst.sext (prec)) |
df2813c5 | 976 | break; |
977 | sign = 1; | |
978 | break; | |
979 | } | |
cf8f0e63 | 980 | if (sign <= 0 && cst == cst.sext (prec)) |
df2813c5 | 981 | { |
982 | sign = -1; | |
983 | break; | |
984 | } | |
985 | ||
986 | if (sign == 1) | |
987 | sign = 0; | |
988 | ||
989 | mode = GET_MODE_WIDER_MODE (mode); | |
990 | if (mode == VOIDmode | |
991 | || GET_MODE_SIZE (mode) >= GET_MODE_SIZE (TYPE_MODE (type))) | |
992 | return type; | |
993 | } | |
994 | } | |
995 | ||
996 | if (sign == 0) | |
997 | sign = TYPE_UNSIGNED (type) ? 1 : -1; | |
998 | smaller_type = lang_hooks.types.type_for_mode (mode, sign >= 0); | |
999 | if (GET_MODE_SIZE (TYPE_MODE (type)) | |
1000 | <= GET_MODE_SIZE (TYPE_MODE (smaller_type))) | |
1001 | return type; | |
1002 | ||
1003 | return smaller_type; | |
1004 | } | |
1005 | ||
a347af29 | 1006 | /* Create an appropriate array type and declaration and assemble a static array |
1007 | variable. Also create a load statement that initializes the variable in | |
1008 | question with a value from the static array. SWTCH is the switch statement | |
1009 | being converted, NUM is the index to arrays of constructors, default values | |
1010 | and target SSA names for this particular array. ARR_INDEX_TYPE is the type | |
1011 | of the index of the new array, PHI is the phi node of the final BB that | |
1012 | corresponds to the value that will be loaded from the created array. TIDX | |
f6ac75a7 | 1013 | is an ssa name of a temporary variable holding the index for loads from the |
1014 | new array. */ | |
a347af29 | 1015 | |
1016 | static void | |
75a70cf9 | 1017 | build_one_array (gimple swtch, int num, tree arr_index_type, gimple phi, |
5d459527 | 1018 | tree tidx, struct switch_conv_info *info) |
a347af29 | 1019 | { |
f6ac75a7 | 1020 | tree name, cst; |
75a70cf9 | 1021 | gimple load; |
f6ac75a7 | 1022 | gimple_stmt_iterator gsi = gsi_for_stmt (swtch); |
e60a6f7b | 1023 | location_t loc = gimple_location (swtch); |
a347af29 | 1024 | |
5d459527 | 1025 | gcc_assert (info->default_values[num]); |
a347af29 | 1026 | |
874117c8 | 1027 | name = copy_ssa_name (PHI_RESULT (phi), NULL); |
5d459527 | 1028 | info->target_inbound_names[num] = name; |
a347af29 | 1029 | |
5d459527 | 1030 | cst = constructor_contains_same_values_p (info->constructors[num]); |
f6ac75a7 | 1031 | if (cst) |
1032 | load = gimple_build_assign (name, cst); | |
1033 | else | |
1034 | { | |
df2813c5 | 1035 | tree array_type, ctor, decl, value_type, fetch, default_type; |
f6ac75a7 | 1036 | |
5d459527 | 1037 | default_type = TREE_TYPE (info->default_values[num]); |
1038 | value_type = array_value_type (swtch, default_type, num, info); | |
f6ac75a7 | 1039 | array_type = build_array_type (value_type, arr_index_type); |
df2813c5 | 1040 | if (default_type != value_type) |
1041 | { | |
1042 | unsigned int i; | |
1043 | constructor_elt *elt; | |
1044 | ||
5d459527 | 1045 | FOR_EACH_VEC_ELT (constructor_elt, info->constructors[num], i, elt) |
df2813c5 | 1046 | elt->value = fold_convert (value_type, elt->value); |
1047 | } | |
5d459527 | 1048 | ctor = build_constructor (array_type, info->constructors[num]); |
f6ac75a7 | 1049 | TREE_CONSTANT (ctor) = true; |
e579afdd | 1050 | TREE_STATIC (ctor) = true; |
f6ac75a7 | 1051 | |
e60a6f7b | 1052 | decl = build_decl (loc, VAR_DECL, NULL_TREE, array_type); |
f6ac75a7 | 1053 | TREE_STATIC (decl) = 1; |
1054 | DECL_INITIAL (decl) = ctor; | |
1055 | ||
1056 | DECL_NAME (decl) = create_tmp_var_name ("CSWTCH"); | |
1057 | DECL_ARTIFICIAL (decl) = 1; | |
1058 | TREE_CONSTANT (decl) = 1; | |
e7baf91d | 1059 | TREE_READONLY (decl) = 1; |
f6ac75a7 | 1060 | varpool_finalize_decl (decl); |
1061 | ||
1062 | fetch = build4 (ARRAY_REF, value_type, decl, tidx, NULL_TREE, | |
1063 | NULL_TREE); | |
df2813c5 | 1064 | if (default_type != value_type) |
1065 | { | |
1066 | fetch = fold_convert (default_type, fetch); | |
1067 | fetch = force_gimple_operand_gsi (&gsi, fetch, true, NULL_TREE, | |
1068 | true, GSI_SAME_STMT); | |
1069 | } | |
f6ac75a7 | 1070 | load = gimple_build_assign (name, fetch); |
1071 | } | |
a347af29 | 1072 | |
75a70cf9 | 1073 | gsi_insert_before (&gsi, load, GSI_SAME_STMT); |
f6ac75a7 | 1074 | update_stmt (load); |
5d459527 | 1075 | info->arr_ref_last = load; |
a347af29 | 1076 | } |
1077 | ||
1078 | /* Builds and initializes static arrays initialized with values gathered from | |
1079 | the SWTCH switch statement. Also creates statements that load values from | |
1080 | them. */ | |
1081 | ||
1082 | static void | |
5d459527 | 1083 | build_arrays (gimple swtch, struct switch_conv_info *info) |
a347af29 | 1084 | { |
1085 | tree arr_index_type; | |
03d37e4e | 1086 | tree tidx, sub, utype; |
75a70cf9 | 1087 | gimple stmt; |
1088 | gimple_stmt_iterator gsi; | |
a347af29 | 1089 | int i; |
389dd41b | 1090 | location_t loc = gimple_location (swtch); |
a347af29 | 1091 | |
75a70cf9 | 1092 | gsi = gsi_for_stmt (swtch); |
49a931ef | 1093 | |
8853d378 | 1094 | /* Make sure we do not generate arithmetics in a subrange. */ |
5d459527 | 1095 | utype = TREE_TYPE (info->index_expr); |
8853d378 | 1096 | if (TREE_TYPE (utype)) |
1097 | utype = lang_hooks.types.type_for_mode (TYPE_MODE (TREE_TYPE (utype)), 1); | |
1098 | else | |
1099 | utype = lang_hooks.types.type_for_mode (TYPE_MODE (utype), 1); | |
1100 | ||
5d459527 | 1101 | arr_index_type = build_index_type (info->range_size); |
03d37e4e | 1102 | tidx = make_ssa_name (utype, NULL); |
8853d378 | 1103 | sub = fold_build2_loc (loc, MINUS_EXPR, utype, |
5d459527 | 1104 | fold_convert_loc (loc, utype, info->index_expr), |
1105 | fold_convert_loc (loc, utype, info->range_min)); | |
42d9ffa5 | 1106 | sub = force_gimple_operand_gsi (&gsi, sub, |
75a70cf9 | 1107 | false, NULL, true, GSI_SAME_STMT); |
1108 | stmt = gimple_build_assign (tidx, sub); | |
a347af29 | 1109 | |
75a70cf9 | 1110 | gsi_insert_before (&gsi, stmt, GSI_SAME_STMT); |
f6ac75a7 | 1111 | update_stmt (stmt); |
5d459527 | 1112 | info->arr_ref_first = stmt; |
a347af29 | 1113 | |
5d459527 | 1114 | for (gsi = gsi_start_phis (info->final_bb), i = 0; |
75a70cf9 | 1115 | !gsi_end_p (gsi); gsi_next (&gsi), i++) |
5d459527 | 1116 | build_one_array (swtch, i, arr_index_type, gsi_stmt (gsi), tidx, info); |
a347af29 | 1117 | } |
1118 | ||
1119 | /* Generates and appropriately inserts loads of default values at the position | |
1120 | given by BSI. Returns the last inserted statement. */ | |
1121 | ||
75a70cf9 | 1122 | static gimple |
5d459527 | 1123 | gen_def_assigns (gimple_stmt_iterator *gsi, struct switch_conv_info *info) |
a347af29 | 1124 | { |
1125 | int i; | |
75a70cf9 | 1126 | gimple assign = NULL; |
a347af29 | 1127 | |
5d459527 | 1128 | for (i = 0; i < info->phi_count; i++) |
a347af29 | 1129 | { |
874117c8 | 1130 | tree name = copy_ssa_name (info->target_inbound_names[i], NULL); |
5d459527 | 1131 | info->target_outbound_names[i] = name; |
1132 | assign = gimple_build_assign (name, info->default_values[i]); | |
75a70cf9 | 1133 | gsi_insert_before (gsi, assign, GSI_SAME_STMT); |
f6ac75a7 | 1134 | update_stmt (assign); |
a347af29 | 1135 | } |
1136 | return assign; | |
1137 | } | |
1138 | ||
1139 | /* Deletes the unused bbs and edges that now contain the switch statement and | |
1140 | its empty branch bbs. BBD is the now dead BB containing the original switch | |
1141 | statement, FINAL is the last BB of the converted switch statement (in terms | |
1142 | of succession). */ | |
1143 | ||
1144 | static void | |
1145 | prune_bbs (basic_block bbd, basic_block final) | |
1146 | { | |
1147 | edge_iterator ei; | |
1148 | edge e; | |
1149 | ||
1150 | for (ei = ei_start (bbd->succs); (e = ei_safe_edge (ei)); ) | |
1151 | { | |
1152 | basic_block bb; | |
1153 | bb = e->dest; | |
1154 | remove_edge (e); | |
1155 | if (bb != final) | |
1156 | delete_basic_block (bb); | |
1157 | } | |
1158 | delete_basic_block (bbd); | |
1159 | } | |
1160 | ||
1161 | /* Add values to phi nodes in final_bb for the two new edges. E1F is the edge | |
1162 | from the basic block loading values from an array and E2F from the basic | |
1163 | block loading default values. BBF is the last switch basic block (see the | |
1164 | bbf description in the comment below). */ | |
1165 | ||
1166 | static void | |
5d459527 | 1167 | fix_phi_nodes (edge e1f, edge e2f, basic_block bbf, |
1168 | struct switch_conv_info *info) | |
a347af29 | 1169 | { |
75a70cf9 | 1170 | gimple_stmt_iterator gsi; |
a347af29 | 1171 | int i; |
1172 | ||
75a70cf9 | 1173 | for (gsi = gsi_start_phis (bbf), i = 0; |
1174 | !gsi_end_p (gsi); gsi_next (&gsi), i++) | |
a347af29 | 1175 | { |
75a70cf9 | 1176 | gimple phi = gsi_stmt (gsi); |
60d535d2 | 1177 | add_phi_arg (phi, info->target_inbound_names[i], e1f, UNKNOWN_LOCATION); |
1178 | add_phi_arg (phi, info->target_outbound_names[i], e2f, UNKNOWN_LOCATION); | |
a347af29 | 1179 | } |
a347af29 | 1180 | } |
1181 | ||
1182 | /* Creates a check whether the switch expression value actually falls into the | |
1183 | range given by all the cases. If it does not, the temporaries are loaded | |
1184 | with default values instead. SWTCH is the switch statement being converted. | |
1185 | ||
1186 | bb0 is the bb with the switch statement, however, we'll end it with a | |
1187 | condition instead. | |
1188 | ||
1189 | bb1 is the bb to be used when the range check went ok. It is derived from | |
1190 | the switch BB | |
1191 | ||
1192 | bb2 is the bb taken when the expression evaluated outside of the range | |
1193 | covered by the created arrays. It is populated by loads of default | |
1194 | values. | |
1195 | ||
1196 | bbF is a fall through for both bb1 and bb2 and contains exactly what | |
1197 | originally followed the switch statement. | |
1198 | ||
1199 | bbD contains the switch statement (in the end). It is unreachable but we | |
1200 | still need to strip off its edges. | |
1201 | */ | |
1202 | ||
1203 | static void | |
5d459527 | 1204 | gen_inbound_check (gimple swtch, struct switch_conv_info *info) |
a347af29 | 1205 | { |
e60a6f7b | 1206 | tree label_decl1 = create_artificial_label (UNKNOWN_LOCATION); |
1207 | tree label_decl2 = create_artificial_label (UNKNOWN_LOCATION); | |
1208 | tree label_decl3 = create_artificial_label (UNKNOWN_LOCATION); | |
75a70cf9 | 1209 | gimple label1, label2, label3; |
8853d378 | 1210 | tree utype, tidx; |
a347af29 | 1211 | tree bound; |
1212 | ||
75a70cf9 | 1213 | gimple cond_stmt; |
a347af29 | 1214 | |
75a70cf9 | 1215 | gimple last_assign; |
1216 | gimple_stmt_iterator gsi; | |
a347af29 | 1217 | basic_block bb0, bb1, bb2, bbf, bbd; |
1218 | edge e01, e02, e21, e1d, e1f, e2f; | |
389dd41b | 1219 | location_t loc = gimple_location (swtch); |
a347af29 | 1220 | |
5d459527 | 1221 | gcc_assert (info->default_values); |
6da0d726 | 1222 | |
75a70cf9 | 1223 | bb0 = gimple_bb (swtch); |
a347af29 | 1224 | |
5d459527 | 1225 | tidx = gimple_assign_lhs (info->arr_ref_first); |
8853d378 | 1226 | utype = TREE_TYPE (tidx); |
1763aab8 | 1227 | |
a347af29 | 1228 | /* (end of) block 0 */ |
5d459527 | 1229 | gsi = gsi_for_stmt (info->arr_ref_first); |
8853d378 | 1230 | gsi_next (&gsi); |
a347af29 | 1231 | |
5d459527 | 1232 | bound = fold_convert_loc (loc, utype, info->range_size); |
8853d378 | 1233 | cond_stmt = gimple_build_cond (LE_EXPR, tidx, bound, NULL_TREE, NULL_TREE); |
75a70cf9 | 1234 | gsi_insert_before (&gsi, cond_stmt, GSI_SAME_STMT); |
f6ac75a7 | 1235 | update_stmt (cond_stmt); |
a347af29 | 1236 | |
1237 | /* block 2 */ | |
75a70cf9 | 1238 | label2 = gimple_build_label (label_decl2); |
1239 | gsi_insert_before (&gsi, label2, GSI_SAME_STMT); | |
5d459527 | 1240 | last_assign = gen_def_assigns (&gsi, info); |
a347af29 | 1241 | |
1242 | /* block 1 */ | |
75a70cf9 | 1243 | label1 = gimple_build_label (label_decl1); |
1244 | gsi_insert_before (&gsi, label1, GSI_SAME_STMT); | |
a347af29 | 1245 | |
1246 | /* block F */ | |
5d459527 | 1247 | gsi = gsi_start_bb (info->final_bb); |
75a70cf9 | 1248 | label3 = gimple_build_label (label_decl3); |
1249 | gsi_insert_before (&gsi, label3, GSI_SAME_STMT); | |
a347af29 | 1250 | |
1251 | /* cfg fix */ | |
75a70cf9 | 1252 | e02 = split_block (bb0, cond_stmt); |
a347af29 | 1253 | bb2 = e02->dest; |
1254 | ||
1255 | e21 = split_block (bb2, last_assign); | |
1256 | bb1 = e21->dest; | |
1257 | remove_edge (e21); | |
1258 | ||
5d459527 | 1259 | e1d = split_block (bb1, info->arr_ref_last); |
a347af29 | 1260 | bbd = e1d->dest; |
1261 | remove_edge (e1d); | |
1262 | ||
1263 | /* flags and profiles of the edge for in-range values */ | |
1264 | e01 = make_edge (bb0, bb1, EDGE_TRUE_VALUE); | |
5d459527 | 1265 | e01->probability = REG_BR_PROB_BASE - info->default_prob; |
1266 | e01->count = info->other_count; | |
a347af29 | 1267 | |
1268 | /* flags and profiles of the edge taking care of out-of-range values */ | |
1269 | e02->flags &= ~EDGE_FALLTHRU; | |
1270 | e02->flags |= EDGE_FALSE_VALUE; | |
5d459527 | 1271 | e02->probability = info->default_prob; |
1272 | e02->count = info->default_count; | |
a347af29 | 1273 | |
5d459527 | 1274 | bbf = info->final_bb; |
a347af29 | 1275 | |
1276 | e1f = make_edge (bb1, bbf, EDGE_FALLTHRU); | |
1277 | e1f->probability = REG_BR_PROB_BASE; | |
5d459527 | 1278 | e1f->count = info->other_count; |
a347af29 | 1279 | |
1280 | e2f = make_edge (bb2, bbf, EDGE_FALLTHRU); | |
1281 | e2f->probability = REG_BR_PROB_BASE; | |
5d459527 | 1282 | e2f->count = info->default_count; |
a347af29 | 1283 | |
1284 | /* frequencies of the new BBs */ | |
1285 | bb1->frequency = EDGE_FREQUENCY (e01); | |
1286 | bb2->frequency = EDGE_FREQUENCY (e02); | |
1287 | bbf->frequency = EDGE_FREQUENCY (e1f) + EDGE_FREQUENCY (e2f); | |
1288 | ||
6da0d726 | 1289 | /* Tidy blocks that have become unreachable. */ |
1290 | prune_bbs (bbd, info->final_bb); | |
a347af29 | 1291 | |
6da0d726 | 1292 | /* Fixup the PHI nodes in bbF. */ |
5d459527 | 1293 | fix_phi_nodes (e1f, e2f, bbf, info); |
a347af29 | 1294 | |
6da0d726 | 1295 | /* Fix the dominator tree, if it is available. */ |
1296 | if (dom_info_available_p (CDI_DOMINATORS)) | |
1297 | { | |
1298 | VEC (basic_block, heap) *bbs_to_fix_dom; | |
1299 | ||
1300 | set_immediate_dominator (CDI_DOMINATORS, bb1, bb0); | |
1301 | set_immediate_dominator (CDI_DOMINATORS, bb2, bb0); | |
78b7a675 | 1302 | if (! get_immediate_dominator (CDI_DOMINATORS, bbf)) |
6da0d726 | 1303 | /* If bbD was the immediate dominator ... */ |
1304 | set_immediate_dominator (CDI_DOMINATORS, bbf, bb0); | |
1305 | ||
1306 | bbs_to_fix_dom = VEC_alloc (basic_block, heap, 4); | |
1307 | VEC_quick_push (basic_block, bbs_to_fix_dom, bb0); | |
1308 | VEC_quick_push (basic_block, bbs_to_fix_dom, bb1); | |
1309 | VEC_quick_push (basic_block, bbs_to_fix_dom, bb2); | |
1310 | VEC_quick_push (basic_block, bbs_to_fix_dom, bbf); | |
1311 | ||
1312 | iterate_fix_dominators (CDI_DOMINATORS, bbs_to_fix_dom, true); | |
1313 | VEC_free (basic_block, heap, bbs_to_fix_dom); | |
1314 | } | |
a347af29 | 1315 | } |
1316 | ||
1317 | /* The following function is invoked on every switch statement (the current one | |
1318 | is given in SWTCH) and runs the individual phases of switch conversion on it | |
5d459527 | 1319 | one after another until one fails or the conversion is completed. |
1320 | Returns NULL on success, or a pointer to a string with the reason why the | |
1321 | conversion failed. */ | |
a347af29 | 1322 | |
5d459527 | 1323 | static const char * |
75a70cf9 | 1324 | process_switch (gimple swtch) |
a347af29 | 1325 | { |
5d459527 | 1326 | struct switch_conv_info info; |
a347af29 | 1327 | |
b7d0690f | 1328 | /* Group case labels so that we get the right results from the heuristics |
1329 | that decide on the code generation approach for this switch. */ | |
1330 | group_case_labels_stmt (swtch); | |
1331 | ||
1332 | /* If this switch is now a degenerate case with only a default label, | |
1333 | there is nothing left for us to do. */ | |
1334 | if (gimple_switch_num_labels (swtch) < 2) | |
1335 | return "switch is a degenerate case"; | |
11f2f313 | 1336 | |
1337 | collect_switch_conv_info (swtch, &info); | |
1338 | ||
1339 | /* No error markers should reach here (they should be filtered out | |
1340 | during gimplification). */ | |
1341 | gcc_checking_assert (TREE_TYPE (info.index_expr) != error_mark_node); | |
1342 | ||
78b7a675 | 1343 | /* A switch on a constant should have been optimized in tree-cfg-cleanup. */ |
1344 | gcc_checking_assert (! TREE_CONSTANT (info.index_expr)); | |
11f2f313 | 1345 | |
78b7a675 | 1346 | if (info.uniq <= MAX_CASE_BIT_TESTS) |
11f2f313 | 1347 | { |
78b7a675 | 1348 | if (expand_switch_using_bit_tests_p (info.range_size, |
11f2f313 | 1349 | info.uniq, info.count)) |
78b7a675 | 1350 | { |
1351 | if (dump_file) | |
1352 | fputs (" expanding as bit test is preferable\n", dump_file); | |
1353 | emit_case_bit_tests (swtch, info.index_expr, | |
1354 | info.range_min, info.range_size); | |
1355 | return NULL; | |
1356 | } | |
1357 | ||
1358 | if (info.uniq <= 2) | |
1359 | /* This will be expanded as a decision tree in stmt.c:expand_case. */ | |
1360 | return " expanding as jumps is preferable"; | |
11f2f313 | 1361 | } |
a347af29 | 1362 | |
78b7a675 | 1363 | /* If there is no common successor, we cannot do the transformation. */ |
1364 | if (! info.final_bb) | |
1365 | return "no common successor to all case label target blocks found"; | |
1366 | ||
a347af29 | 1367 | /* Check the case label values are within reasonable range: */ |
11f2f313 | 1368 | if (!check_range (&info)) |
5d459527 | 1369 | { |
1370 | gcc_assert (info.reason); | |
1371 | return info.reason; | |
1372 | } | |
a347af29 | 1373 | |
1374 | /* For all the cases, see whether they are empty, the assignments they | |
1375 | represent constant and so on... */ | |
11f2f313 | 1376 | if (! check_all_empty_except_final (&info)) |
df2813c5 | 1377 | { |
11f2f313 | 1378 | gcc_assert (info.reason); |
1379 | return info.reason; | |
df2813c5 | 1380 | } |
5d459527 | 1381 | if (!check_final_bb (&info)) |
1382 | { | |
1383 | gcc_assert (info.reason); | |
1384 | return info.reason; | |
1385 | } | |
a347af29 | 1386 | |
1387 | /* At this point all checks have passed and we can proceed with the | |
1388 | transformation. */ | |
1389 | ||
5d459527 | 1390 | create_temp_arrays (&info); |
49a70175 | 1391 | gather_default_values (gimple_switch_default_label (swtch), &info); |
5d459527 | 1392 | build_constructors (swtch, &info); |
a347af29 | 1393 | |
5d459527 | 1394 | build_arrays (swtch, &info); /* Build the static arrays and assignments. */ |
1395 | gen_inbound_check (swtch, &info); /* Build the bounds check. */ | |
a347af29 | 1396 | |
1397 | /* Cleanup: */ | |
5d459527 | 1398 | free_temp_arrays (&info); |
1399 | return NULL; | |
a347af29 | 1400 | } |
1401 | ||
1402 | /* The main function of the pass scans statements for switches and invokes | |
1403 | process_switch on them. */ | |
1404 | ||
1405 | static unsigned int | |
1406 | do_switchconv (void) | |
1407 | { | |
1408 | basic_block bb; | |
1409 | ||
1410 | FOR_EACH_BB (bb) | |
1411 | { | |
5d459527 | 1412 | const char *failure_reason; |
75a70cf9 | 1413 | gimple stmt = last_stmt (bb); |
1414 | if (stmt && gimple_code (stmt) == GIMPLE_SWITCH) | |
a347af29 | 1415 | { |
a347af29 | 1416 | if (dump_file) |
1417 | { | |
75a70cf9 | 1418 | expanded_location loc = expand_location (gimple_location (stmt)); |
1419 | ||
a347af29 | 1420 | fprintf (dump_file, "beginning to process the following " |
1421 | "SWITCH statement (%s:%d) : ------- \n", | |
1422 | loc.file, loc.line); | |
75a70cf9 | 1423 | print_gimple_stmt (dump_file, stmt, 0, TDF_SLIM); |
609e7ca1 | 1424 | putc ('\n', dump_file); |
a347af29 | 1425 | } |
1426 | ||
5d459527 | 1427 | failure_reason = process_switch (stmt); |
1428 | if (! failure_reason) | |
a347af29 | 1429 | { |
1430 | if (dump_file) | |
1431 | { | |
609e7ca1 | 1432 | fputs ("Switch converted\n", dump_file); |
1433 | fputs ("--------------------------------\n", dump_file); | |
a347af29 | 1434 | } |
78b7a675 | 1435 | |
1436 | /* Make no effort to update the post-dominator tree. It is actually not | |
1437 | that hard for the transformations we have performed, but it is not | |
1438 | supported by iterate_fix_dominators. */ | |
1439 | free_dominance_info (CDI_POST_DOMINATORS); | |
a347af29 | 1440 | } |
1441 | else | |
1442 | { | |
1443 | if (dump_file) | |
1444 | { | |
609e7ca1 | 1445 | fputs ("Bailing out - ", dump_file); |
5d459527 | 1446 | fputs (failure_reason, dump_file); |
1447 | fputs ("\n--------------------------------\n", dump_file); | |
a347af29 | 1448 | } |
1449 | } | |
1450 | } | |
1451 | } | |
1452 | ||
1453 | return 0; | |
1454 | } | |
1455 | ||
1456 | /* The pass gate. */ | |
1457 | ||
1458 | static bool | |
1459 | switchconv_gate (void) | |
1460 | { | |
1461 | return flag_tree_switch_conversion != 0; | |
1462 | } | |
1463 | ||
1464 | struct gimple_opt_pass pass_convert_switch = | |
1465 | { | |
1466 | { | |
1467 | GIMPLE_PASS, | |
1468 | "switchconv", /* name */ | |
cc17b19b | 1469 | switchconv_gate, /* gate */ |
a347af29 | 1470 | do_switchconv, /* execute */ |
1471 | NULL, /* sub */ | |
1472 | NULL, /* next */ | |
1473 | 0, /* static_pass_number */ | |
f28b0a6a | 1474 | TV_TREE_SWITCH_CONVERSION, /* tv_id */ |
a347af29 | 1475 | PROP_cfg | PROP_ssa, /* properties_required */ |
1476 | 0, /* properties_provided */ | |
1477 | 0, /* properties_destroyed */ | |
1478 | 0, /* todo_flags_start */ | |
771e2890 | 1479 | TODO_update_ssa |
78b7a675 | 1480 | | TODO_ggc_collect | TODO_verify_ssa |
1481 | | TODO_verify_stmts | |
1482 | | TODO_verify_flow /* todo_flags_finish */ | |
a347af29 | 1483 | } |
1484 | }; |