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1 | /* Conditional compare related functions | |
2 | Copyright (C) 2014-2020 Free Software Foundation, Inc. | |
3 | ||
4 | This file is part of GCC. | |
5 | ||
6 | GCC is free software; you can redistribute it and/or modify it under | |
7 | the terms of the GNU General Public License as published by the Free | |
8 | Software Foundation; either version 3, or (at your option) any later | |
9 | version. | |
10 | ||
11 | GCC is distributed in the hope that it will be useful, but WITHOUT ANY | |
12 | 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. | |
15 | ||
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 "backend.h" | |
24 | #include "target.h" | |
25 | #include "rtl.h" | |
26 | #include "tree.h" | |
27 | #include "gimple.h" | |
28 | #include "memmodel.h" | |
29 | #include "tm_p.h" | |
30 | #include "ssa.h" | |
31 | #include "expmed.h" | |
32 | #include "optabs.h" | |
33 | #include "emit-rtl.h" | |
34 | #include "stor-layout.h" | |
35 | #include "tree-ssa-live.h" | |
36 | #include "tree-outof-ssa.h" | |
37 | #include "cfgexpand.h" | |
38 | #include "ccmp.h" | |
39 | #include "predict.h" | |
40 | ||
41 | /* Check whether T is a simple boolean variable or a SSA name | |
42 | set by a comparison operator in the same basic block. */ | |
43 | static bool | |
44 | ccmp_tree_comparison_p (tree t, basic_block bb) | |
45 | { | |
46 | gimple *g = get_gimple_for_ssa_name (t); | |
47 | tree_code tcode; | |
48 | ||
49 | /* If we have a boolean variable allow it and generate a compare | |
50 | to zero reg when expanding. */ | |
51 | if (!g) | |
52 | return (TREE_CODE (TREE_TYPE (t)) == BOOLEAN_TYPE); | |
53 | ||
54 | /* Check to see if SSA name is set by a comparison operator in | |
55 | the same basic block. */ | |
56 | if (!is_gimple_assign (g)) | |
57 | return false; | |
58 | if (bb != gimple_bb (g)) | |
59 | return false; | |
60 | tcode = gimple_assign_rhs_code (g); | |
61 | return TREE_CODE_CLASS (tcode) == tcc_comparison; | |
62 | } | |
63 | ||
64 | /* The following functions expand conditional compare (CCMP) instructions. | |
65 | Here is a short description about the over all algorithm: | |
66 | * ccmp_candidate_p is used to identify the CCMP candidate | |
67 | ||
68 | * expand_ccmp_expr is the main entry, which calls expand_ccmp_expr_1 | |
69 | to expand CCMP. | |
70 | ||
71 | * expand_ccmp_expr_1 uses a recursive algorithm to expand CCMP. | |
72 | It calls two target hooks gen_ccmp_first and gen_ccmp_next to generate | |
73 | CCMP instructions. | |
74 | - gen_ccmp_first expands the first compare in CCMP. | |
75 | - gen_ccmp_next expands the following compares. | |
76 | ||
77 | Both hooks return a comparison with the CC register that is equivalent | |
78 | to the value of the gimple comparison. This is used by the next CCMP | |
79 | and in the final conditional store. | |
80 | ||
81 | * We use cstorecc4 pattern to convert the CCmode intermediate to | |
82 | the integer mode result that expand_normal is expecting. | |
83 | ||
84 | Since the operands of the later compares might clobber CC reg, we do not | |
85 | emit the insns during expand. We keep the insn sequences in two seq | |
86 | ||
87 | * prep_seq, which includes all the insns to prepare the operands. | |
88 | * gen_seq, which includes all the compare and conditional compares. | |
89 | ||
90 | If all checks OK in expand_ccmp_expr, it emits insns in prep_seq, then | |
91 | insns in gen_seq. */ | |
92 | ||
93 | /* Check whether G is a potential conditional compare candidate. */ | |
94 | static bool | |
95 | ccmp_candidate_p (gimple *g) | |
96 | { | |
97 | tree lhs, op0, op1; | |
98 | gimple *gs0, *gs1; | |
99 | tree_code tcode; | |
100 | basic_block bb; | |
101 | ||
102 | if (!g) | |
103 | return false; | |
104 | ||
105 | tcode = gimple_assign_rhs_code (g); | |
106 | if (tcode != BIT_AND_EXPR && tcode != BIT_IOR_EXPR) | |
107 | return false; | |
108 | ||
109 | lhs = gimple_assign_lhs (g); | |
110 | op0 = gimple_assign_rhs1 (g); | |
111 | op1 = gimple_assign_rhs2 (g); | |
112 | if ((TREE_CODE (op0) != SSA_NAME) || (TREE_CODE (op1) != SSA_NAME) | |
113 | || !has_single_use (lhs)) | |
114 | return false; | |
115 | ||
116 | bb = gimple_bb (g); | |
117 | gs0 = get_gimple_for_ssa_name (op0); /* gs0 may be NULL */ | |
118 | gs1 = get_gimple_for_ssa_name (op1); /* gs1 may be NULL */ | |
119 | ||
120 | if (ccmp_tree_comparison_p (op0, bb) && ccmp_tree_comparison_p (op1, bb)) | |
121 | return true; | |
122 | if (ccmp_tree_comparison_p (op0, bb) && ccmp_candidate_p (gs1)) | |
123 | return true; | |
124 | if (ccmp_tree_comparison_p (op1, bb) && ccmp_candidate_p (gs0)) | |
125 | return true; | |
126 | /* We skip ccmp_candidate_p (gs1) && ccmp_candidate_p (gs0) since | |
127 | there is no way to set and maintain the CC flag on both sides of | |
128 | the logical operator at the same time. */ | |
129 | return false; | |
130 | } | |
131 | ||
132 | /* Extract the comparison we want to do from the tree. */ | |
133 | void | |
134 | get_compare_parts (tree t, int *up, rtx_code *rcode, | |
135 | tree *rhs1, tree *rhs2) | |
136 | { | |
137 | tree_code code; | |
138 | gimple *g = get_gimple_for_ssa_name (t); | |
139 | if (g) | |
140 | { | |
141 | *up = TYPE_UNSIGNED (TREE_TYPE (gimple_assign_rhs1 (g))); | |
142 | code = gimple_assign_rhs_code (g); | |
143 | *rcode = get_rtx_code (code, *up); | |
144 | *rhs1 = gimple_assign_rhs1 (g); | |
145 | *rhs2 = gimple_assign_rhs2 (g); | |
146 | } | |
147 | else | |
148 | { | |
149 | /* If g is not a comparison operator create a compare to zero. */ | |
150 | *up = 1; | |
151 | *rcode = NE; | |
152 | *rhs1 = t; | |
153 | *rhs2 = build_zero_cst (TREE_TYPE (t)); | |
154 | } | |
155 | } | |
156 | ||
157 | /* PREV is a comparison with the CC register which represents the | |
158 | result of the previous CMP or CCMP. The function expands the | |
159 | next compare based on G which is ANDed/ORed with the previous | |
160 | compare depending on CODE. | |
161 | PREP_SEQ returns all insns to prepare opearands for compare. | |
162 | GEN_SEQ returns all compare insns. */ | |
163 | static rtx | |
164 | expand_ccmp_next (tree op, tree_code code, rtx prev, | |
165 | rtx_insn **prep_seq, rtx_insn **gen_seq) | |
166 | { | |
167 | rtx_code rcode; | |
168 | int unsignedp; | |
169 | tree rhs1, rhs2; | |
170 | ||
171 | get_compare_parts(op, &unsignedp, &rcode, &rhs1, &rhs2); | |
172 | return targetm.gen_ccmp_next (prep_seq, gen_seq, prev, rcode, | |
173 | rhs1, rhs2, get_rtx_code (code, 0)); | |
174 | } | |
175 | ||
176 | /* Expand conditional compare gimple G. A typical CCMP sequence is like: | |
177 | ||
178 | CC0 = CMP (a, b); | |
179 | CC1 = CCMP (NE (CC0, 0), CMP (e, f)); | |
180 | ... | |
181 | CCn = CCMP (NE (CCn-1, 0), CMP (...)); | |
182 | ||
183 | hook gen_ccmp_first is used to expand the first compare. | |
184 | hook gen_ccmp_next is used to expand the following CCMP. | |
185 | PREP_SEQ returns all insns to prepare opearand. | |
186 | GEN_SEQ returns all compare insns. */ | |
187 | static rtx | |
188 | expand_ccmp_expr_1 (gimple *g, rtx_insn **prep_seq, rtx_insn **gen_seq) | |
189 | { | |
190 | tree_code code = gimple_assign_rhs_code (g); | |
191 | basic_block bb = gimple_bb (g); | |
192 | ||
193 | tree op0 = gimple_assign_rhs1 (g); | |
194 | tree op1 = gimple_assign_rhs2 (g); | |
195 | gimple *gs0 = get_gimple_for_ssa_name (op0); | |
196 | gimple *gs1 = get_gimple_for_ssa_name (op1); | |
197 | rtx tmp; | |
198 | ||
199 | gcc_assert (code == BIT_AND_EXPR || code == BIT_IOR_EXPR); | |
200 | ||
201 | if (ccmp_tree_comparison_p (op0, bb)) | |
202 | { | |
203 | if (ccmp_tree_comparison_p (op1, bb)) | |
204 | { | |
205 | int unsignedp0, unsignedp1; | |
206 | rtx_code rcode0, rcode1; | |
207 | tree logical_op0_rhs1, logical_op0_rhs2; | |
208 | tree logical_op1_rhs1, logical_op1_rhs2; | |
209 | int speed_p = optimize_insn_for_speed_p (); | |
210 | ||
211 | rtx tmp2 = NULL_RTX, ret = NULL_RTX, ret2 = NULL_RTX; | |
212 | unsigned cost1 = MAX_COST; | |
213 | unsigned cost2 = MAX_COST; | |
214 | ||
215 | get_compare_parts (op0, &unsignedp0, &rcode0, | |
216 | &logical_op0_rhs1, &logical_op0_rhs2); | |
217 | ||
218 | get_compare_parts (op1, &unsignedp1, &rcode1, | |
219 | &logical_op1_rhs1, &logical_op1_rhs2); | |
220 | ||
221 | rtx_insn *prep_seq_1, *gen_seq_1; | |
222 | tmp = targetm.gen_ccmp_first (&prep_seq_1, &gen_seq_1, rcode0, | |
223 | logical_op0_rhs1, logical_op0_rhs2); | |
224 | if (tmp != NULL) | |
225 | { | |
226 | ret = expand_ccmp_next (op1, code, tmp, &prep_seq_1, &gen_seq_1); | |
227 | cost1 = seq_cost (prep_seq_1, speed_p); | |
228 | cost1 += seq_cost (gen_seq_1, speed_p); | |
229 | } | |
230 | ||
231 | /* FIXME: Temporary workaround for PR69619. | |
232 | Avoid exponential compile time due to expanding gs0 and gs1 twice. | |
233 | If gs0 and gs1 are complex, the cost will be high, so avoid | |
234 | reevaluation if above an arbitrary threshold. */ | |
235 | rtx_insn *prep_seq_2, *gen_seq_2; | |
236 | if (tmp == NULL || cost1 < COSTS_N_INSNS (25)) | |
237 | tmp2 = targetm.gen_ccmp_first (&prep_seq_2, &gen_seq_2, rcode1, | |
238 | logical_op1_rhs1, logical_op1_rhs2); | |
239 | if (!tmp && !tmp2) | |
240 | return NULL_RTX; | |
241 | if (tmp2 != NULL) | |
242 | { | |
243 | ret2 = expand_ccmp_next (op0, code, tmp2, &prep_seq_2, | |
244 | &gen_seq_2); | |
245 | cost2 = seq_cost (prep_seq_2, speed_p); | |
246 | cost2 += seq_cost (gen_seq_2, speed_p); | |
247 | } | |
248 | if (cost2 < cost1) | |
249 | { | |
250 | *prep_seq = prep_seq_2; | |
251 | *gen_seq = gen_seq_2; | |
252 | return ret2; | |
253 | } | |
254 | *prep_seq = prep_seq_1; | |
255 | *gen_seq = gen_seq_1; | |
256 | return ret; | |
257 | } | |
258 | else | |
259 | { | |
260 | tmp = expand_ccmp_expr_1 (gs1, prep_seq, gen_seq); | |
261 | if (!tmp) | |
262 | return NULL_RTX; | |
263 | return expand_ccmp_next (op0, code, tmp, prep_seq, gen_seq); | |
264 | } | |
265 | } | |
266 | else | |
267 | { | |
268 | gcc_assert (gimple_assign_rhs_code (gs0) == BIT_AND_EXPR | |
269 | || gimple_assign_rhs_code (gs0) == BIT_IOR_EXPR); | |
270 | gcc_assert (ccmp_tree_comparison_p (op1, bb)); | |
271 | tmp = expand_ccmp_expr_1 (gs0, prep_seq, gen_seq); | |
272 | if (!tmp) | |
273 | return NULL_RTX; | |
274 | return expand_ccmp_next (op1, code, tmp, prep_seq, gen_seq); | |
275 | } | |
276 | ||
277 | return NULL_RTX; | |
278 | } | |
279 | ||
280 | /* Main entry to expand conditional compare statement G. | |
281 | Return NULL_RTX if G is not a legal candidate or expand fail. | |
282 | Otherwise return the target. */ | |
283 | rtx | |
284 | expand_ccmp_expr (gimple *g, machine_mode mode) | |
285 | { | |
286 | rtx_insn *last; | |
287 | rtx tmp; | |
288 | ||
289 | if (!ccmp_candidate_p (g)) | |
290 | return NULL_RTX; | |
291 | ||
292 | last = get_last_insn (); | |
293 | ||
294 | rtx_insn *prep_seq = NULL, *gen_seq = NULL; | |
295 | tmp = expand_ccmp_expr_1 (g, &prep_seq, &gen_seq); | |
296 | ||
297 | if (tmp) | |
298 | { | |
299 | insn_code icode; | |
300 | machine_mode cc_mode = CCmode; | |
301 | rtx_code cmp_code = GET_CODE (tmp); | |
302 | ||
303 | #ifdef SELECT_CC_MODE | |
304 | cc_mode = SELECT_CC_MODE (cmp_code, XEXP (tmp, 0), const0_rtx); | |
305 | #endif | |
306 | icode = optab_handler (cstore_optab, cc_mode); | |
307 | if (icode != CODE_FOR_nothing) | |
308 | { | |
309 | rtx target = gen_reg_rtx (mode); | |
310 | ||
311 | emit_insn (prep_seq); | |
312 | emit_insn (gen_seq); | |
313 | ||
314 | tmp = emit_cstore (target, icode, cmp_code, cc_mode, cc_mode, | |
315 | 0, XEXP (tmp, 0), const0_rtx, 1, mode); | |
316 | if (tmp) | |
317 | return tmp; | |
318 | } | |
319 | } | |
320 | /* Clean up. */ | |
321 | delete_insns_since (last); | |
322 | return NULL_RTX; | |
323 | } |