GCC后端及汇编发布（43）

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13. genconfig工具

这个工具将产生诸如“已知最大操作数编号”，“在任一指令中match_dup的最大数目”，“在一个split中已知的最大指令数”等，连同定义来表示是否出现特殊指令的宏，例如HAVE_conditional_move,HAVE_peephole2，到文件insn-config.h

260 int

261 main (int argc, char **argv) ingenconfig.c

262 {

263 rtx desc;

264

265 progname= "genconfig";

266

267 if (argc <= 1)

268 fatal ("no input file name");

269

270 if (init_md_reader_args (argc, argv) != SUCCESS_EXIT_CODE)

271 return (FATAL_EXIT_CODE);

272

273 puts ("/* Generated automatically by the program`genconfig'");

274 puts (" from the machinedescription file `md'. */\n");

275 puts ("#ifndef GCC_INSN_CONFIG_H");

276 puts ("#define GCC_INSN_CONFIG_H\n");

277

278 /* Allow at least 30 operands for the sake ofasm constructs. */

279 /* ??? We *really* ought to reorganize thingssuch that there

280 is no fixed upper bound. */

281 max_recog_operands= 29; /* Wewill add 1 later. */

282 max_dup_operands= 1;

283

284 /* Read the machine description. */

285

286 while (1)

287 {

288 int line_no, insn_code_number = 0;

289

290 desc = read_md_rtx (&line_no,&insn_code_number);

291 if (desc == NULL)

292 break;

293

294 switch (GET_CODE (desc))

295 {

296 case DEFINE_INSN:

297 gen_insn (desc);

298 break;

299

300 case DEFINE_EXPAND:

301 gen_expand (desc);

302 break;

303

304 case DEFINE_SPLIT:

305 gen_split (desc);

306 break;

307

308 case DEFINE_PEEPHOLE2:

309 have_peephole2_flag= 1;

310 gen_peephole2 (desc);

311 break;

312

313 case DEFINE_PEEPHOLE:

314 have_peephole_flag= 1;

315 gen_peephole (desc);

316 break;

317

318 default:

319 break;

320 }

321 }

322

323 printf ("#define MAX_RECOG_OPERANDS %d\n", max_recog_operands+ 1);

324 printf ("#define MAX_DUP_OPERANDS %d\n", max_dup_operands);

325

326 /* This is conditionally defined, in case theuser writes code which emits

327 more splits than we can readily see (andknows s/he does it). */

328 printf ("#ifndef MAX_INSNS_PER_SPLIT\n");

329 printf ("#define MAX_INSNS_PER_SPLIT %d\n", max_insns_per_split);

330 printf ("#endif\n");

331

332 if (have_cc0_flag)

333 {

334 printf ("#define HAVE_cc0 1\n");

335 printf ("#define CC0_P(X) ((X) == cc0_rtx)\n");

336 }

337 else

338 {

339 printf ("#define CC0_P(X) 0\n");

340 }

341

342 if (have_cmove_flag)

343 printf ("#define HAVE_conditional_move 1\n");

344

345 if (have_cond_exec_flag)

346 printf ("#define HAVE_conditional_execution 1\n");

347

348 if (have_lo_sum_flag)

349 printf ("#define HAVE_lo_sum 1\n");

350

351 if (have_peephole_flag)

352 printf ("#define HAVE_peephole 1\n");

353

354 if (have_peephole2_flag)

355 {

356 printf ("#define HAVE_peephole2 1\n");

357 printf ("#define MAX_INSNS_PER_PEEP2 %d\n", max_insns_per_peep2);

358 }

359

360 puts("\n#endif /* GCC_INSN_CONFIG_H */");

361

362 if (ferror (stdout) || fflush (stdout) || fclose (stdout))

363 return FATAL_EXIT_CODE;

364

365 return SUCCESS_EXIT_CODE;

366 }

仅以gen_insn作为例子，对于其它模式（pattern），其处理函数是类似的。

170 static void

171 gen_insn (rtx insn) ingenconfig.c

172 {

173 int i;

174

175 /* Walk the insn pattern to gather the#define's status. */

176 clobbers_seen_this_insn= 0;

177 dup_operands_seen_this_insn= 0;

178 if (XVEC (insn, 1) != 0)

179 for(i = 0; i < XVECLEN (insn, 1); i++)

180 walk_insn_part (XVECEXP (insn, 1, i), 1,0);

181

182 if (clobbers_seen_this_insn> max_clobbers_per_insn)

183 max_clobbers_per_insn= clobbers_seen_this_insn;

184 if (dup_operands_seen_this_insn> max_dup_operands)

185 max_dup_operands= dup_operands_seen_this_insn;

186 }

我们已经看到define_insn模式的第二个孩子是一个不完整的RTL表达式向量的RTL模板，它显示了这个指令看起来应该像什么。它是不完整的，因为它可能包含了表达式match_operand，match_operator，及match_dup，它们代表了该指令的操作数。为这个向量中的每个项，调用walk_insn_part。

66 static void

67 walk_insn_part (rtx part, int recog_p, int non_pc_set_src) ingenconfig.c

68 {

69 int i, j;

70 RTX_CODE code;

71 const char *format_ptr;

73 if (part == 0)

74 return;

76 code = GET_CODE (part);

77 switch (code)

78 {

79 case CLOBBER:

80 clobbers_seen_this_insn++;

81 break;

83 case MATCH_OPERAND:

84 if (XINT (part, 0) > max_recog_operands)

85 max_recog_operands = XINT (part, 0);

86 return;

88 case MATCH_OP_DUP:

89 case MATCH_PAR_DUP:

90 ++dup_operands_seen_this_insn;

91 case MATCH_SCRATCH:

92 case MATCH_PARALLEL:

93 case MATCH_OPERATOR:

94 if (XINT (part, 0) > max_recog_operands)

95 max_recog_operands = XINT (part, 0);

96 /* Now scan the rtl's in the vector inside theMATCH_OPERATOR or

97 MATCH_PARALLEL. */

98 break;

100 case LABEL_REF:

101 if (GET_CODE (XEXP (part, 0)) == MATCH_OPERAND)

102 break;

103 return;

104

105 case MATCH_DUP:

106 ++dup_operands_seen_this_insn;

107 if (XINT (part, 0) > max_recog_operands)

108 max_recog_operands= XINT (part, 0);

109 return;

110

111 case CC0:

112 if (recog_p)

113 have_cc0_flag= 1;

114 return;

115

116 case LO_SUM:

117 if (recog_p)

118 have_lo_sum_flag= 1;

119 return;

120

121 case SET:

122 walk_insn_part (SET_DEST (part), 0,recog_p);

123 walk_insn_part (SET_SRC (part), recog_p,

124 GET_CODE (SET_DEST (part))!= PC);

125 return;

126

127 case IF_THEN_ELSE:

128 /* Only consider this machine as having aconditional move if the

129 two arms of the IF_THEN_ELSE are bothMATCH_OPERAND. Otherwise,

130 we have some specific IF_THEN_ELSEconstruct (like the doz

131 instruction on the RS/6000) that can'tbe used in the general

132 context we want it for. */

133

134 if (recog_p && non_pc_set_src

135 && GET_CODE (XEXP (part, 1)) ==MATCH_OPERAND

136 && GET_CODE (XEXP (part, 2)) ==MATCH_OPERAND)

137 have_cmove_flag= 1;

138 break;

139

140 case COND_EXEC:

141 if (recog_p)

142 have_cond_exec_flag= 1;

143 break;

144

145 case REG: caseCONST_INT: case SYMBOL_REF:

146 case PC:

147 return;

148

149 default:

150 break;

151 }

152

153 format_ptr = GET_RTX_FORMAT (GET_CODE (part));

154

155 for (i = 0; i < GET_RTX_LENGTH(GET_CODE (part)); i++)

156 switch (*format_ptr++)

157 {

158 case 'e':

159 case 'u':

160 walk_insn_part (XEXP (part,i), recog_p, non_pc_set_src);

161 break;

162 case 'E':

163 if (XVEC (part, i) != NULL)

164 for(j = 0; j < XVECLEN (part, i); j++)

165 walk_insn_part(XVECEXP (part, i, j), recog_p, non_pc_set_src);

166 break;

167 }

168 }

如果该模式（pattern）被发现在一个它通常将被识别，而不是仅产生一个指令的上下文中，参数recog_p将是非0值。而如果这个模式被发现在一个目标不是（PC）的SET的SET_SRC中，参数non_pc_set_src将是非0值。