在Makefile.in中这样定义规则：

insn-modes.h: s-modes-h; @true

s-modes-h: build/genmodes$(build_exeext)

     $(RUN_GEN) build/genmodes$(build_exeext) -h > tmp-modes.h

     $(SHELL) $(srcdir)/../move-if-change tmp-modes.h insn-modes.h

     $(STAMP) s-modes-h

即它由genmodes.exe生成，而genmodes.exe则由

build/genmodes.o : genmodes.c $(BCONFIG_H) $(SYSTEM_H) errors.h       \

  $(HASHTAB_H) machmode.def $(extra_modes_file)

# As a general rule...

build/gen%$(build_exeext): build/gen%.o $(BUILD_LIBDEPS)

     $(CC_FOR_BUILD) $(BUILD_CFLAGS) $(BUILD_LDFLAGS) -o $@ \

         $(filter-out $(BUILD_LIBDEPS), $^) $(BUILD_LIBS)

规则指定。

因而先生成genmodes.exe，再执行

genmodes.exe –h

得到insn-modes.h。

/* Generated automatically from machmode.def

   by genmodes.  */

#ifndef GCC_INSN_MODES_H

#define GCC_INSN_MODES_H

enum machine_mode

{

  VOIDmode,                /* machmode.def:169 */

  BLKmode,                 /* machmode.def:173 */

  CCmode,                  /* machmode.def:201 */

  BImode,                  /* machmode.def:176 */

  QImode,                  /* machmode.def:181 */

  HImode,                  /* machmode.def:182 */

  SImode,                  /* machmode.def:183 */

  DImode,                  /* machmode.def:184 */

  TImode,                  /* machmode.def:185 */

  QQmode,                  /* machmode.def:204 */

  HQmode,                  /* machmode.def:205 */

  SQmode,                  /* machmode.def:206 */

  DQmode,                  /* machmode.def:207 */

  TQmode,                  /* machmode.def:208 */

  UQQmode,                 /* machmode.def:210 */

  UHQmode,                 /* machmode.def:211 */

  USQmode,                 /* machmode.def:212 */

  UDQmode,                 /* machmode.def:213 */

  UTQmode,                 /* machmode.def:214 */

  HAmode,                  /* machmode.def:216 */

  SAmode,                  /* machmode.def:217 */

  DAmode,                  /* machmode.def:218 */

  TAmode,                  /* machmode.def:219 */

  UHAmode,                 /* machmode.def:221 */

  USAmode,                 /* machmode.def:222 */

  UDAmode,                 /* machmode.def:223 */

  UTAmode,                 /* machmode.def:224 */

  SFmode,                  /* machmode.def:196 */

  DFmode,                  /* machmode.def:197 */

  SDmode,                  /* machmode.def:236 */

  DDmode,                  /* machmode.def:237 */

  TDmode,                  /* machmode.def:238 */

  CQImode,                 /* machmode.def:232 */

  CHImode,                 /* machmode.def:232 */

  CSImode,                 /* machmode.def:232 */

  CDImode,                 /* machmode.def:232 */

  CTImode,                 /* machmode.def:232 */

  SCmode,                  /* machmode.def:233 */

  DCmode,                  /* machmode.def:233 */

  MAX_MACHINE_MODE,

  MIN_MODE_RANDOM = VOIDmode,

  MAX_MODE_RANDOM = BLKmode,

  MIN_MODE_CC = CCmode,

  MAX_MODE_CC = CCmode,

  MIN_MODE_INT = QImode,

  MAX_MODE_INT = TImode,

  MIN_MODE_PARTIAL_INT = VOIDmode,

  MAX_MODE_PARTIAL_INT = VOIDmode,

  MIN_MODE_FRACT = QQmode,

  MAX_MODE_FRACT = TQmode,

  MIN_MODE_UFRACT = UQQmode,

  MAX_MODE_UFRACT = UTQmode,

  MIN_MODE_ACCUM = HAmode,

  MAX_MODE_ACCUM = TAmode,

  MIN_MODE_UACCUM = UHAmode,

  MAX_MODE_UACCUM = UTAmode,

  MIN_MODE_FLOAT = SFmode,

  MAX_MODE_FLOAT = DFmode,

  MIN_MODE_DECIMAL_FLOAT = SDmode,

  MAX_MODE_DECIMAL_FLOAT = TDmode,

  MIN_MODE_COMPLEX_INT = CQImode,

  MAX_MODE_COMPLEX_INT = CTImode,

  MIN_MODE_COMPLEX_FLOAT = SCmode,

  MAX_MODE_COMPLEX_FLOAT = DCmode,

  MIN_MODE_VECTOR_INT = VOIDmode,

  MAX_MODE_VECTOR_INT = VOIDmode,

  MIN_MODE_VECTOR_FRACT = VOIDmode,

  MAX_MODE_VECTOR_FRACT = VOIDmode,

  MIN_MODE_VECTOR_UFRACT = VOIDmode,

  MAX_MODE_VECTOR_UFRACT = VOIDmode,

  MIN_MODE_VECTOR_ACCUM = VOIDmode,

  MAX_MODE_VECTOR_ACCUM = VOIDmode,

  MIN_MODE_VECTOR_UACCUM = VOIDmode,

  MAX_MODE_VECTOR_UACCUM = VOIDmode,

  MIN_MODE_VECTOR_FLOAT = VOIDmode,

  MAX_MODE_VECTOR_FLOAT = VOIDmode,

  NUM_MACHINE_MODES = MAX_MACHINE_MODE

};

#define CONST_MODE_SIZE const

#define CONST_MODE_BASE_ALIGN const

#define CONST_MODE_IBIT const

#define CONST_MODE_FBIT const

#endif /* insn-modes.h */