15. genpeep工具
模式define_peephole的细节参考概览 – 关于define_peephole一节，这个工具不处理define_peephole2模式，这个模式则由genemit，genoutput及genrecog工具处理了。
353 int
354 main (int argc, char **argv) ingenpeep.c
355 {
356 rtx desc;
357
358 max_opno= -1;
359
360 progname= "genpeep";
361
362 if (argc <= 1)
363 fatal ("no input file name");
364
365 if (init_md_reader_args (argc, argv) != SUCCESS_EXIT_CODE)
366 return (FATAL_EXIT_CODE);
367
368 printf ("/* Generated automatically by the program `genpeep'\n\
369 from the machine description file`md'. */\n\n");
370
371 printf ("#include\"config.h\"\n");
372 printf ("#include \"system.h\"\n");
373 printf ("#include \"coretypes.h\"\n");
374 printf ("#include \"tm.h\"\n");
375 printf ("#include \"insn-config.h\"\n");
376 printf ("#include \"rtl.h\"\n");
377 printf ("#include \"tm_p.h\"\n");
378 printf ("#include \"regs.h\"\n");
379 printf ("#include \"output.h\"\n");
380 printf ("#include \"real.h\"\n");
381 printf ("#include \"recog.h\"\n");
382 printf ("#include \"except.h\"\n\n");
383 printf ("#include \"function.h\"\n\n");
384
385 printf ("#ifdef HAVE_peephole\n");
386 printf ("extern rtx peep_operand[];\n\n");
387 printf ("#define operands peep_operand\n\n");
388
389 printf ("rtx\npeephole (rtx ins1)\n{\n");
390 printf (" rtx insn ATTRIBUTE_UNUSED, xATTRIBUTE_UNUSED, pat ATTRIBUTE_UNUSED;\n\n");
391
392 /* Early out: no peepholes for insns followedby barriers. */
393 printf (" if (NEXT_INSN(ins1)\n");
394 printf (" &&GET_CODE (NEXT_INSN (ins1)) == BARRIER)\n");
395 printf (" return0;\n\n");
396
397 /* Read the machine description. */
398
399 while (1)
400 {
401 int line_no, rtx_number = 0;
402
403 desc = read_md_rtx (&line_no,&rtx_number);
404 if (desc == NULL)
405 break;
406
407 if (GET_CODE (desc) == DEFINE_PEEPHOLE)
408 {
409 gen_peephole (desc);
410 insn_code_number++;
411 }
412 if (GET_CODE (desc) == DEFINE_INSN
413 || GET_CODE (desc) == DEFINE_EXPAND
414 || GET_CODE (desc) == DEFINE_SPLIT
415 || GET_CODE (desc) == DEFINE_PEEPHOLE2)
416 {
417 insn_code_number++;
418 }
419 }
420
421 printf (" return0;\n}\n\n");
422
423 if (max_opno== -1)
424 max_opno= 1;
425
426 printf ("rtx peep_operand[%d];\n", max_opno + 1);
427 printf ("#endif\n");
428
429 fflush (stdout);
430 return (ferror (stdout) != 0 ?FATAL_EXIT_CODE : SUCCESS_EXIT_CODE);
431 }
直到399行，我们可以看到如下的输出的片段。
/* Generated automatically by theprogram `genpeep'
from the machine description file`md'. */
#include "config.h"
#include "system.h"
#include "coretypes.h"
#include "tm.h"
#include "insn-config.h"
#include "rtl.h"
#include "tm_p.h"
#include "regs.h"
#include "output.h"
#include "real.h"
#include "recog.h"
#include "except.h"
#include "function.h"
#ifdef HAVE_peephole
extern rtx peep_operand[];
#define operands peep_operand
rtx
peephole (rtx ins1)
{
rtx insn ATTRIBUTE_UNUSED, x ATTRIBUTE_UNUSED, pat ATTRIBUTE_UNUSED;
if (NEXT_INSN (ins1)
&& GET_CODE (NEXT_INSN (ins1)) ==BARRIER)
return 0;
gen_peephole continues to ouput the pattern in the
peephole function.
61 static void
62 gen_peephole (rtx peep) ingenpeep.c
63 {
64 int ninsns = XVECLEN (peep, 0);
65 int i;
66
67 n_operands= 0;
68
69 printf (" insn =ins1;\n");
70
71 for(i = 0; i < ninsns; i++)
72 {
73 if (i > 0)
74 {
75 printf (" do { insn =NEXT_INSN (insn);\n");
76 printf (" if (insn == 0) goto L%d; }\n",
77 insn_code_number);
78 printf (" while (GET_CODE(insn) == NOTE\n");
79 printf ("\t || (GET_CODE(insn) == INSN\n");
80 printf ("\t &&(GET_CODE (PATTERN (insn)) == USE\n");
81 printf ("\t\t || GET_CODE (PATTERN (insn)) == CLOBBER)));\n");
82
83 printf (" if (GET_CODE(insn) == CODE_LABEL\n\
84 || GET_CODE (insn) ==BARRIER)\n goto L%d;\n",
85 insn_code_number);
86 }
87
88 printf (" pat = PATTERN (insn);\n");
89
90 /* Walk the insn's pattern, remembering at alltimes the path
91 down to the walking point. */
92
93 match_rtx (XVECEXP (peep, 0, i), NULL,
insn_code_number);
94 }
95
96 /* We get this far if the pattern matches.
97 Now test the extra condition. */
98
99 if (XSTR (peep, 1) && XSTR (peep, 1)[0])
100 printf (" if (! (%s)) gotoL%d;\n",
101 XSTR (peep, 1), insn_code_number);
102
103 /* If that matches, construct new pattern andput it in the first insn.
104 This new pattern will never be matched.
105 It exists only so that insn-extract can getthe operands back.
106 So use a simple regular form: a PARALLELcontaining a vector
107 of all the operands. */
108
109 printf (" PATTERN (ins1) =gen_rtx_PARALLEL (VOIDmode, gen_rtvec_v (%d, operands));\n",
n_operands);
110
111 /* Record this define_peephole's insn code inthe insn,
112 as if it had been recognized to matchthis. */
113 printf (" INSN_CODE (ins1) = %d;\n",
114 insn_code_number);
115
116 /* Delete the remaining insns. */
117 if (ninsns > 1)
118 printf (" delete_for_peephole (NEXT_INSN (ins1), insn);\n");
119
120 /* See reload1.c for insertion of NOTE whichguarantees that this
121 cannot be zero. */
122 printf (" return NEXT_INSN(insn);\n");
123
124 printf (" L%d:\n\n", insn_code_number);
125 }
那么如果架构（对于i386系统，没有定义define_peephole）包含define_peephole，直到 93行，在调用match_rtx之前，我们可以得到如下的peephole函数。
rtx
peephole (rtx ins1)
{
rtx insn ATTRIBUTE_UNUSED, x ATTRIBUTE_UNUSED, pat ATTRIBUTE_UNUSED;
if (NEXT_INSN (ins1)
&& GET_CODE (NEXT_INSN (ins1)) ==BARRIER)
return 0;
insn = ins1;
do { insn = NEXT_INSN (insn);
if (insn == 0) gotoL’insn-code-num`; }
while (GET_CODE (insn) == NOTE
|| (GET_CODE (insn) == INSN
&& (GET_CODE(PATTERN (insn)) == USE
|| GET_CODE (PATTERN(insn)) == CLOBBER)));
if (GET_CODE (insn) == CODE_LABEL
|| GET_CODE (insn)== BARRIER)
goto L’insn-code-num`;
pat = PATTERN (insn);
对于我们在概览 – 关于define_peephole中看到的例子，这个rtx对象的第一个孩子是如下的rtx对象，它将是match_rtx的第一个参数。
[(set(reg:SI 15) (plus:SI (reg:SI 15) (const_int 4)))
(set(match_operand:DF 0 "register_operand" "=f")
(match_operand:DF 1"register_operand" "ad"))]
它是包含两条指令的parallel。
在输出的peephole中，insn是由emit_insn产生的rtx对象，PATTERN将从这个指令获取define_insn的rtx对象。
127 static void
128 match_rtx (rtx x, struct link *path, intfail_label) in
genpeep.c
129 {
130 RTX_CODE code;
131 int i;
132 int len;
133 constchar *fmt;
134 struct link link;
135
136 if (x == 0)
137 return;
138
139
140 code = GET_CODE (x);
141
142 switch (code)
143 {
144 case MATCH_OPERAND:
145 if (XINT (x, 0) > max_opno)
146 max_opno= XINT (x, 0);
147 if (XINT (x, 0) >= n_operands)
148 n_operands= 1 + XINT (x, 0);
149
150 printf (" x = ");
151 print_path (path);
152 printf (";\n");
153
154 printf (" operands[%d] =x;\n", XINT (x, 0));
155 if (XSTR (x, 1) && XSTR (x, 1)[0])
156 printf (" if (! %s (x,%smode)) goto L%d;\n",
157 XSTR(x, 1), GET_MODE_NAME (GET_MODE (x)), fail_label);
158 return;
159
160 case MATCH_DUP:
161 case MATCH_PAR_DUP:
162 printf (" x = ");
163 print_path (path);
164 printf (";\n");
165
166 printf (" if (!rtx_equal_p(operands[%d], x)) goto L%d;\n",
167 XINT (x, 0), fail_label);
168 return;
169
170 case MATCH_OP_DUP:
171 printf (" x = ");
172 print_path (path);
173 printf (";\n");
174
175 printf (" if (GET_CODE(operands[%d]) != GET_CODE (x)\n", XINT (x, 0));
176 printf (" || GET_MODE(operands[%d]) != GET_MODE (x)) goto L%d;\n",
177 XINT (x, 0), fail_label);
178 printf (" operands[%d] =x;\n", XINT (x, 0));
179 link.next = path;
180 link.vecelt = -1;
181 for(i = 0; i < XVECLEN (x, 1); i++)
182 {
183 link.pos = i;
184 match_rtx (XVECEXP (x, 1, i), &link,fail_label);
185 }
186 return;
187
188 case MATCH_OPERATOR:
189 if (XINT (x, 0) > max_opno)
190 max_opno= XINT (x, 0);
191 if (XINT (x, 0) >= n_operands)
192 n_operands= 1 + XINT (x, 0);
193
194 printf (" x = ");
195 print_path (path);
196 printf (";\n");
197
198 printf (" operands[%d] =x;\n", XINT (x, 0));
199 if (XSTR (x, 1) && XSTR (x, 1)[0])
200 printf (" if (! %s (x,%smode)) goto L%d;\n",
201 XSTR (x, 1), GET_MODE_NAME(GET_MODE (x)), fail_label);
202 link.next = path;
203 link.vecelt = -1;
204 for(i = 0; i < XVECLEN (x, 2); i++)
205 {
206 link.pos = i;
207 match_rtx (XVECEXP (x, 2, i), &link,fail_label);
208 }
209 return;
210
211 case MATCH_PARALLEL:
212 if (XINT (x, 0) > max_opno)
213 max_opno= XINT (x, 0);
214 if (XINT (x, 0) >= n_operands)
215 n_operands= 1 + XINT (x, 0);
216
217 printf (" x = ");
218 print_path (path);
219 printf (";\n");
220
221 printf (" if (GET_CODE (x)!= PARALLEL) goto L%d;\n", fail_label);
222 printf (" operands[%d] =x;\n", XINT (x, 0));
223 if (XSTR (x, 1) && XSTR (x, 1)[0])
224 printf (" if (! %s (x,%smode)) goto L%d;\n",
225 XSTR(x, 1), GET_MODE_NAME (GET_MODE (x)), fail_label);
226 link.next = path;
227 link.pos = 0;
228 for(i = 0; i < XVECLEN (x, 2); i++)
229 {
230 link.vecelt = i;
231 match_rtx (XVECEXP (x, 2, i), &link,fail_label);
232 }
233 return;
234
235 case ADDRESS:
236 match_rtx (XEXP (x, 0),path, fail_label);
237 return;
238
239 default:
240 break;
241 }
242
243 printf (" x = ");
244 print_path (path);
245 printf (";\n");
246
247 printf (" if (GET_CODE (x)!= ");
248 print_code (code);
249 printf (") goto L%d;\n",fail_label);
250
251 if (GET_MODE (x) != VOIDmode)
252 {
253 printf (" if (GET_MODE (x)!= %smode) goto L%d;\n",
254 GET_MODE_NAME (GET_MODE (x)),fail_label);
255 }
256
257 link.next = path;
258 link.vecelt = -1;
259 fmt = GET_RTX_FORMAT (code);
260 len = GET_RTX_LENGTH (code);
261 for(i = 0; i < len; i++)
262 {
263 link.pos = i;
264 if (fmt[i] == 'e' || fmt[i] =='u')
265 match_rtx (XEXP (x, i),&link, fail_label);
266 else if (fmt[i] == 'E')
267 {
268 int j;
269 printf (" if (XVECLEN (x,%d) != %d) goto L%d;\n",
270 i, XVECLEN (x, i),fail_label);
271 for(j = 0; j < XVECLEN (x, i); j++)
272 {
273 link.vecelt = j;
274 match_rtx (XVECEXP (x, i, j), &link,fail_label);
275 }
276 }
277 else if (fmt[i] == 'i')
278 {
279 /* Make sure that at run time `x' is the RTXwe want to test. */
280 if (i != 0)
281 {
282 printf (" x = ");
283 print_path (path);
284 printf (";\n");
285 }
286
287 printf (" if (XINT (x, %d)!= %d) goto L%d;\n",
288 i, XINT (x, i), fail_label);
289 }
290 else if (fmt[i] == 'w')
291 {
292 /* Make sure that at run time `x' is the RTXwe want to test. */
293 if (i != 0)
294 {
295 printf (" x = ");
296 print_path (path);
297 printf (";\n");
298 }
299
300 printf (" if (XWINT (x, %d)!= ", i);
301 printf (HOST_WIDE_INT_PRINT_DEC, XWINT (x, i));
302 printf (") goto L%d;\n", fail_label);
303 }
304 else if (fmt[i] == 's')
305 {
306 /* Make sure that at run time `x' is the RTXwe want to test. */
307 if (i != 0)
308 {
309 printf (" x = ");
310 print_path (path);
311 printf (";\n");
312 }
313
314 printf (" if (strcmp (XSTR(x, %d), \"%s\")) goto L%d;\n",
315 i, XSTR (x, i),fail_label);
316 }
317 }
318 }
324 static void
325 print_path (struct link *path) in
genpeep.c
326 {
327 if (path == 0)
328 printf ("pat");
329 else if (path->vecelt >= 0)
330 {
331 printf ("XVECEXP (");
332 print_path (path->next);
333 printf (", %d, %d)", path->pos, path->vecelt);
334 }
335 else
336 {
337 printf ("XEXP (");
338 print_path (path->next);
339 printf (", %d)", path->pos);
340 }
341 }
对于指令，输出的peephole如下：
1 rtx
2 peephole (rtx ins1)
3 {
4 rtx insnATTRIBUTE_UNUSED, x ATTRIBUTE_UNUSED, pat ATTRIBUTE_UNUSED;
5
6 if(NEXT_INSN (ins1)
7 && GET_CODE (NEXT_INSN (ins1)) == BARRIER)
8 return0;
9
10 insn = ins1;
11 do { insn = NEXT_INSN(insn);
12 if (insn == 0) goto L`insn-code-num`; }
13 while (GET_CODE (insn)== NOTE
14 || (GET_CODE (insn) ==INSN
15 && (GET_CODE (PATTERN (insn)) == USE
16 || GET_CODE (PATTERN (insn)) == CLOBBER)));
17
18 if (GET_CODE (insn) ==CODE_LABEL
19 || GET_CODE (insn) == BARRIER)
20 goto L`insn-code-num`;
21
22 pat = PATTERN (insn); // first insn
23 x = pat;
24 if (GET_CODE (x) !=SET) goto L`insn-code-num`; // set
25 if (GET_CODE (x) != REG)goto L`insn-code-num`; // reg:SI 15
26 if (GET_MODE (x) !=SImode) goto L`insn-code-num`;
27 x = XEXP (pat, 0);
28 if (XINT (x, 0) != 15)goto L`insn-code-num`;
29 if (GET_CODE (x)!= PLUS) goto L`insn-code-num`; //plus
30 if (GET_MODE (x) !=SImode) goto L`insn-code-num`;
31 if (GET_CODE (x) != REG)goto L`insn-code-num`; // reg:SI 15
32 if (GET_MODE (x) !=SImode) goto L`insn-code-num`;
33 x = XEXP (XEXP(pat,1), 0);
34 if (XINT (x, 0) != 15)goto L`insn-code-num`;
35 if (GET_CODE(x) !=CONST_INT) goto L`insn-code-num`; //const_int
36 x = XEXP (XEXP(pat,1), 1);
37 if (XWINT (x, 0) != 4)goto L`insn-code-num`;
38
39 do { insn = NEXT_INSN(insn); // second insn
40 if (insn == 0) goto L`insn-code-num`; }
41 while (GET_CODE (insn)== NOTE
42 || (GET_CODE (insn) ==INSN
43 && (GET_CODE (PATTERN (insn)) == USE
44 || GET_CODE (PATTERN (insn)) == CLOBBER)));
45
46 if (GET_CODE (insn) ==CODE_LABEL
47 || GET_CODE (insn) == BARRIER)
48 goto L`insn-code-num`;
49
50 pat = PATTERN (insn);
51 x = pat;
52 if (GET_CODE (x) !=SET) goto L`insn-code-num`; // set
53 x = XEXP (pat, 0);
54 operands [0] = x;
55 if (!match_operand (x,DFmode)) goto L`insn-code-num`; //match_operand 0
56 x = XEXP (pat, 1);
57 operands [1] = x;
58 if (!match_operand (x,DFmode)) goto L`insn-code-num`; //match_operand 1
59 if (FP_REG_P(operands[0]) && ! FP_REG_P (operands[1])) goto L`insn-code-num`;
60 // out of match_rtx
61 PATTERN (ins1) =gen_rtx_PARALLEL (VOIDmode, gen_rtvec_v (2, operands));
62 INSN_CODE (ins1) =`insn-code-num`;
63 delete_for_peephole(NEXT_INSN (ins1), insn);
64 return NEXT_INSN(insn);
65 L`insn-code-num`:
66 return 0;
67 }
68
69 rtx peep_operand[2];
70 #endif
有趣的是，在上面，当指令序列匹配时，新的指令对象将被构建并加入序列在。在genoutput工具一节，define_peephole被赋予唯一的指令编号，并且输出用于汇编生成的数据。看到在上面62行， 这个新的指令对象被赋予这个指令编号。这个号码将是找出对应汇编输出模板的索引。