1 /*
2 * CSE - walk the linearized instruction flow, and
3 * see if we can simplify it and apply CSE on it.
4 *
5 * Copyright (C) 2004 Linus Torvalds
6 */
7
8 #include <string.h>
9 #include <stdarg.h>
10 #include <stdlib.h>
11 #include <stdio.h>
12 #include <stddef.h>
13 #include <assert.h>
14
15 #include "parse.h"
16 #include "expression.h"
17 #include "flowgraph.h"
18 #include "linearize.h"
19 #include "flow.h"
20 #include "cse.h"
21
22 #define INSN_HASH_SIZE 256
23 static struct instruction_list *insn_hash_table[INSN_HASH_SIZE];
24
phi_compare(pseudo_t phi1,pseudo_t phi2)25 static int phi_compare(pseudo_t phi1, pseudo_t phi2)
26 {
27 const struct instruction *def1 = phi1->def;
28 const struct instruction *def2 = phi2->def;
29
30 if (def1->src1 != def2->src1)
31 return def1->src1 < def2->src1 ? -1 : 1;
32 if (def1->bb != def2->bb)
33 return def1->bb < def2->bb ? -1 : 1;
34 return 0;
35 }
36
37
cse_collect(struct instruction * insn)38 void cse_collect(struct instruction *insn)
39 {
40 unsigned long hash;
41
42 hash = (insn->opcode << 3) + (insn->size >> 3);
43 switch (insn->opcode) {
44 case OP_SEL:
45 hash += hashval(insn->src3);
46 /* Fall through */
47
48 /* Binary arithmetic */
49 case OP_ADD: case OP_SUB:
50 case OP_MUL:
51 case OP_DIVU: case OP_DIVS:
52 case OP_MODU: case OP_MODS:
53 case OP_SHL:
54 case OP_LSR: case OP_ASR:
55 case OP_AND: case OP_OR:
56
57 /* Binary logical */
58 case OP_XOR:
59
60 /* Binary comparison */
61 case OP_SET_EQ: case OP_SET_NE:
62 case OP_SET_LE: case OP_SET_GE:
63 case OP_SET_LT: case OP_SET_GT:
64 case OP_SET_B: case OP_SET_A:
65 case OP_SET_BE: case OP_SET_AE:
66
67 /* floating-point arithmetic & comparison */
68 case OP_FPCMP ... OP_FPCMP_END:
69 case OP_FADD:
70 case OP_FSUB:
71 case OP_FMUL:
72 case OP_FDIV:
73 hash += hashval(insn->src2);
74 /* Fall through */
75
76 /* Unary */
77 case OP_NOT: case OP_NEG:
78 case OP_FNEG:
79 case OP_SYMADDR:
80 hash += hashval(insn->src1);
81 break;
82
83 case OP_SETVAL:
84 hash += hashval(insn->val);
85 break;
86
87 case OP_SETFVAL:
88 hash += hashval(insn->fvalue);
89 break;
90
91 case OP_SEXT: case OP_ZEXT:
92 case OP_TRUNC:
93 case OP_PTRCAST:
94 case OP_UTPTR: case OP_PTRTU:
95 if (!insn->orig_type || insn->orig_type->bit_size < 0)
96 return;
97 hash += hashval(insn->src);
98
99 // Note: see corresponding line in insn_compare()
100 hash += hashval(insn->orig_type->bit_size);
101 break;
102
103 /* Other */
104 case OP_PHI: {
105 pseudo_t phi;
106 FOR_EACH_PTR(insn->phi_list, phi) {
107 struct instruction *def;
108 if (phi == VOID || !phi->def)
109 continue;
110 def = phi->def;
111 hash += hashval(def->src1);
112 hash += hashval(def->bb);
113 } END_FOR_EACH_PTR(phi);
114 break;
115 }
116
117 default:
118 /*
119 * Nothing to do, don't even bother hashing them,
120 * we're not going to try to CSE them
121 */
122 return;
123 }
124 hash += hash >> 16;
125 hash &= INSN_HASH_SIZE-1;
126 add_instruction(insn_hash_table + hash, insn);
127 }
128
129 /* Compare two (sorted) phi-lists */
phi_list_compare(struct pseudo_list * l1,struct pseudo_list * l2)130 static int phi_list_compare(struct pseudo_list *l1, struct pseudo_list *l2)
131 {
132 pseudo_t phi1, phi2;
133
134 PREPARE_PTR_LIST(l1, phi1);
135 PREPARE_PTR_LIST(l2, phi2);
136 for (;;) {
137 int cmp;
138
139 while (phi1 && (phi1 == VOID || !phi1->def))
140 NEXT_PTR_LIST(phi1);
141 while (phi2 && (phi2 == VOID || !phi2->def))
142 NEXT_PTR_LIST(phi2);
143
144 if (!phi1)
145 return phi2 ? -1 : 0;
146 if (!phi2)
147 return phi1 ? 1 : 0;
148 cmp = phi_compare(phi1, phi2);
149 if (cmp)
150 return cmp;
151 NEXT_PTR_LIST(phi1);
152 NEXT_PTR_LIST(phi2);
153 }
154 /* Not reached, but we need to make the nesting come out right */
155 FINISH_PTR_LIST(phi2);
156 FINISH_PTR_LIST(phi1);
157 }
158
insn_compare(const void * _i1,const void * _i2)159 static int insn_compare(const void *_i1, const void *_i2)
160 {
161 const struct instruction *i1 = _i1;
162 const struct instruction *i2 = _i2;
163 int size1, size2;
164 int diff;
165
166 if (i1->opcode != i2->opcode)
167 return i1->opcode < i2->opcode ? -1 : 1;
168
169 switch (i1->opcode) {
170
171 /* commutative binop */
172 case OP_ADD:
173 case OP_MUL:
174 case OP_AND: case OP_OR:
175 case OP_XOR:
176 case OP_SET_EQ: case OP_SET_NE:
177 if (i1->src1 == i2->src2 && i1->src2 == i2->src1)
178 return 0;
179 goto case_binops;
180
181 case OP_SEL:
182 if (i1->src3 != i2->src3)
183 return i1->src3 < i2->src3 ? -1 : 1;
184 /* Fall-through to binops */
185
186 /* Binary arithmetic */
187 case OP_SUB:
188 case OP_DIVU: case OP_DIVS:
189 case OP_MODU: case OP_MODS:
190 case OP_SHL:
191 case OP_LSR: case OP_ASR:
192
193 /* Binary comparison */
194 case OP_SET_LE: case OP_SET_GE:
195 case OP_SET_LT: case OP_SET_GT:
196 case OP_SET_B: case OP_SET_A:
197 case OP_SET_BE: case OP_SET_AE:
198
199 /* floating-point arithmetic */
200 case OP_FPCMP ... OP_FPCMP_END:
201 case OP_FADD:
202 case OP_FSUB:
203 case OP_FMUL:
204 case OP_FDIV:
205 case_binops:
206 if (i1->src2 != i2->src2)
207 return i1->src2 < i2->src2 ? -1 : 1;
208 /* Fall through to unops */
209
210 /* Unary */
211 case OP_NOT: case OP_NEG:
212 case OP_FNEG:
213 case OP_SYMADDR:
214 if (i1->src1 != i2->src1)
215 return i1->src1 < i2->src1 ? -1 : 1;
216 break;
217
218 case OP_SETVAL:
219 if (i1->val != i2->val)
220 return i1->val < i2->val ? -1 : 1;
221 break;
222
223 case OP_SETFVAL:
224 diff = memcmp(&i1->fvalue, &i2->fvalue, sizeof(i1->fvalue));
225 if (diff)
226 return diff;
227 break;
228
229 /* Other */
230 case OP_PHI:
231 return phi_list_compare(i1->phi_list, i2->phi_list);
232
233 case OP_SEXT: case OP_ZEXT:
234 case OP_TRUNC:
235 case OP_PTRCAST:
236 case OP_UTPTR: case OP_PTRTU:
237 if (i1->src != i2->src)
238 return i1->src < i2->src ? -1 : 1;
239
240 // Note: if it can be guaranted that identical ->src
241 // implies identical orig_type->bit_size, then this
242 // test and the hashing of the original size in
243 // cse_collect() are not needed.
244 // It must be generaly true but it isn't guaranted (yet).
245 size1 = i1->orig_type->bit_size;
246 size2 = i2->orig_type->bit_size;
247 if (size1 != size2)
248 return size1 < size2 ? -1 : 1;
249 break;
250
251 default:
252 warning(i1->pos, "bad instruction on hash chain");
253 }
254 if (i1->size != i2->size)
255 return i1->size < i2->size ? -1 : 1;
256 return 0;
257 }
258
sort_instruction_list(struct instruction_list ** list)259 static void sort_instruction_list(struct instruction_list **list)
260 {
261 sort_list((struct ptr_list **)list , insn_compare);
262 }
263
cse_one_instruction(struct instruction * insn,struct instruction * def)264 static struct instruction * cse_one_instruction(struct instruction *insn, struct instruction *def)
265 {
266 convert_instruction_target(insn, def->target);
267
268 kill_instruction(insn);
269 repeat_phase |= REPEAT_CSE;
270 return def;
271 }
272
trivial_common_parent(struct basic_block * bb1,struct basic_block * bb2)273 static struct basic_block *trivial_common_parent(struct basic_block *bb1, struct basic_block *bb2)
274 {
275 struct basic_block *parent;
276
277 if (bb_list_size(bb1->parents) != 1)
278 return NULL;
279 parent = first_basic_block(bb1->parents);
280 if (bb_list_size(bb2->parents) != 1)
281 return NULL;
282 if (first_basic_block(bb2->parents) != parent)
283 return NULL;
284 return parent;
285 }
286
remove_instruction(struct instruction_list ** list,struct instruction * insn,int count)287 static inline void remove_instruction(struct instruction_list **list, struct instruction *insn, int count)
288 {
289 delete_ptr_list_entry((struct ptr_list **)list, insn, count);
290 }
291
add_instruction_to_end(struct instruction * insn,struct basic_block * bb)292 static void add_instruction_to_end(struct instruction *insn, struct basic_block *bb)
293 {
294 struct instruction *br = delete_last_instruction(&bb->insns);
295 insn->bb = bb;
296 add_instruction(&bb->insns, insn);
297 add_instruction(&bb->insns, br);
298 }
299
try_to_cse(struct entrypoint * ep,struct instruction * i1,struct instruction * i2)300 static struct instruction * try_to_cse(struct entrypoint *ep, struct instruction *i1, struct instruction *i2)
301 {
302 struct basic_block *b1, *b2, *common;
303
304 /*
305 * OK, i1 and i2 are the same instruction, modulo "target".
306 * We should now see if we can combine them.
307 */
308 b1 = i1->bb;
309 b2 = i2->bb;
310
311 /*
312 * Currently we only handle the uninteresting degenerate case where
313 * the CSE is inside one basic-block.
314 */
315 if (b1 == b2) {
316 struct instruction *insn;
317 FOR_EACH_PTR(b1->insns, insn) {
318 if (insn == i1)
319 return cse_one_instruction(i2, i1);
320 if (insn == i2)
321 return cse_one_instruction(i1, i2);
322 } END_FOR_EACH_PTR(insn);
323 warning(b1->pos, "Whaa? unable to find CSE instructions");
324 return i1;
325 }
326 if (domtree_dominates(b1, b2))
327 return cse_one_instruction(i2, i1);
328
329 if (domtree_dominates(b2, b1))
330 return cse_one_instruction(i1, i2);
331
332 /* No direct dominance - but we could try to find a common ancestor.. */
333 common = trivial_common_parent(b1, b2);
334 if (common) {
335 i1 = cse_one_instruction(i2, i1);
336 remove_instruction(&b1->insns, i1, 1);
337 add_instruction_to_end(i1, common);
338 } else {
339 i1 = i2;
340 }
341
342 return i1;
343 }
344
cse_eliminate(struct entrypoint * ep)345 void cse_eliminate(struct entrypoint *ep)
346 {
347 int i;
348
349 for (i = 0; i < INSN_HASH_SIZE; i++) {
350 struct instruction_list **list = insn_hash_table + i;
351 if (*list) {
352 if (instruction_list_size(*list) > 1) {
353 struct instruction *insn, *last;
354
355 sort_instruction_list(list);
356
357 last = NULL;
358 FOR_EACH_PTR(*list, insn) {
359 if (!insn->bb)
360 continue;
361 if (last) {
362 if (!insn_compare(last, insn))
363 insn = try_to_cse(ep, last, insn);
364 }
365 last = insn;
366 } END_FOR_EACH_PTR(insn);
367 }
368 free_ptr_list(list);
369 }
370 }
371 }
372