GCC backend and Assembly release (42)

12. genflags Tool

This tool outputs insn-flags, functions generated by genemit, and a series of have _ * Macros containing conditions templates in the define_insn and define_expand modes.

 

233Int

234Main (INT argc, char ** argv) inGenflags. c

235{

236Rtx desc;

237RTX dummy;

238RTX * insns;

239RTX * insn_ptr;

240

241 progname= "Genflags ";

242Obstack_init (&Obstack);

243

244/* We need to see all the possibilities. elided insns may have

245Direct callto their generators in cCode .*/

246 insn_elision= 0;

247

248If (argc <= 1)

249Fatal ("no input file name ");

250

251If (init_md_reader_args (argc, argv )! = Success_exit_code)

252Return (fatal_exit_code );

253

254Puts ("/* generated automatically by the program 'genflags '");

255Puts ("from the machine descriptionfile 'md'. */\ n ");

256Puts ("# ifndef gcc_insn_flags_h ");

257Puts ("# define gcc_insn_flags_h \ n ");

258

259/* Read the machine description .*/

260

261While (1)

262{

263Int line_no, insn_code_number = 0;

264

265Desc = read_md_rtx (& line_no, & insn_code_number );

266If (DESC = NULL)

267Break;

268If (get_code (DESC) = define_insn | get_code (DESC) = define_expand)

269Gen_insn (DESC );

270}

271

272/* Print out the prototypes now .*/

273Dummy = (RTx) 0;

274Obstack_grow (&Obstack, & Dummy, sizeof (RTx ));

275Insns = (RTX *) obstack_finish (&Obstack);

276

277For (insn_ptr = insns; * insn_ptr; insn_ptr ++)

278Gen_proto (* insn_ptr );

279

280Puts ("\ n # endif/* gcc_insn_flags_h */");

281

282If (ferror (stdout) | fflush (stdout) | fclose (stdout ))

283Return fatal_exit_code;

284

285Return success_exit_code;

286}

 

As we can see from other chapters,Init_md_reader_argsAndRead_md_rtxRead the pattern from the machine description file, and build the correspondingDescThe RTX object. This object consistsGen_insn.

 

192Static void

193Gen_insn (RTX insn) inGenflags. c

194{

195Const char * name = xstr (insn, 0 );

196Const char * P;

197Int Len;

198Int truth = maybe_eval_c_test (xstr (insn, 2 ));

199

200/* Don't mention instructions whose names arethe Null String

201Or begin with '*'. They are in the machinedescription just

202To be recognized .*/

203If (name [0] = 0 | Name [0] = '*')

204Return;

205

206Len = strlen (name );

207

208If (LEN>Max_id_len)

209 max_id_len= Len;

210

211If (truth = 0)

212/* Emit nothing .*/;

213Else if (truth = 1)

214Printf ("# define have _ % S 1 \ n", name );

215Else

216{

217/* Write the macro definition, putting \'s atthe end of each line,

218If more than one .*/

219Printf ("# define have _ % s (", name );

220For (P = xstr (insn, 2); * P; P ++)

221{

222If (is_vspace (* p ))

223Fputs ("\\\ N", stdout );

224Else

225Putchar (* P );

226}

227Fputs (") \ n", stdout );

228}

229

230Obstack_grow (&Obstack, & Insn, sizeof (RTx ));

231}

 

We already know that for expressions that are known to be true at the time of compilation,Maybe_eval_c_test1 is returned. If it is a false expression, 0 is returned. If it is other expressions,-1 is returned. Note that in row 203, the anonymous mode or the mode whose name starts with '*' will be ignored. In row 3, the address of the qualified RTX object will be savedObstack.

BackMainIn row 275, an empty RTX object is addedObstackTo ensure that 277 rowsForThe loop can exit correctly. For each meaningful define_insn or define_expand mode (pattern ),Gen_protoPerform the following operations.

 

129Static void

130Gen_proto (RTX insn) inGenflags. c

131{

132Int num = num_operands (insn );

133Int I;

134Const char * name = xstr (insn, 0 );

135Int truth = maybe_eval_c_test (xstr (insn, 2 ));

136

137/* Specify MD files don't refer to the last twooperands passed to

138Call patterns. This means their generatorfunctions will be two

139Arguments too short. Instead of changingevery MD file to touch

140Those operands, we wrap the prototypes inmacros that take

141Correct number of arguments .*/

142If (name [0] = 'C' | Name [0] ='s ')

143{

144If (! Strcmp (name, "call ")

145|! Strcmp (name, "call_pop ")

146|! Strcmp (name, "sibcall ")

147|! Strcmp (name, "sibcall_pop "))

148Gen_macro (name, num, 4 );

149Else if (! Strcmp (name, "call_value ")

150|! Strcmp (name, "call_value_pop ")

151|! Strcmp (name, "sibcall_value ")

152|! Strcmp (name, "sibcall_value_pop "))

153Gen_macro (name, num, 5 );

154}

155

156If (truth! = 0)

157Printf ("extern RTX Gen _ %-* s (",Max_id_len, Name );

158Else

159Printf ("static inline RTX Gen _ %-* s (",Max_id_len, Name );

160

161If (num = 0)

162Fputs ("Void", stdout );

163Else

164{

165For (I = 1; I <num; I ++)

166Fputs ("RTX,", stdout );

167

168Fputs ("RTX", stdout );

169}

170

171Puts (");");

172

173/* Some back ends want to take the address ofgenerator functions,

174So we cannot simply use # define for thesedummy definitions .*/

175If (truth = 0)

176{

177Printf ("static inline RTX \ ngen _ % s", name );

178If (Num> 0)

179{

180Putchar ('(');

181For (I = 0; I <num-1; I ++)

182Printf ("RTX % cattribute_unused,", 'A' + I );

183Printf ("RTX % C attribute_unused) \ n", 'A' + I );

184}

185Else

186Puts ("(void )");

187Puts ("{\ n return0; \ n }");

188}

189

190}

 

We can see the pattern with the name "call", "call_pop", "sibcall", "sbicall_pop", "call_value_pop", "call_value", "sibcall_value", and "sibcall_value_pop) furtherGen_macroPerform the following operations.

 

100Static void

101Gen_macro (const char * Name, int real, intexpect) in
Genflags. c

102{

103Int I;

104

105If (real> exact CT)

106Abort ();

107If (real = 0)

108Abort ();

109

110/* # Define gen_call (A, B, C, D) gen_call (a), (B ))*/

111Fputs ("# define Gen _", stdout );

112For (I = 0; name [I]; I ++)

113Putchar (toupper (name [I]);

114

115Putchar ('(');

116For (I = 0; I <CT-1; I ++)

117Printf ("% C,", I + 'A ');

118Printf ("% C) Gen _ % s (", I + 'A', name );

119

120For (I = 0; I <real-1; I ++)

121Printf ("(% C),", I + 'A ');

122Printf ("(% C) \ n", I + 'A ');

123}

 

This function generates a macro for the corresponding function used in the pattern mentioned above. BackGen_proto, Output the prototype of these functions from rows 156 to 169. Note that for the pattern condition template that is known as false at the time of compilation, its definition will also appear in insn-Flags -- 175 to 188 rows to generate the functions that return 0.