text: #ifndef _H8300_SWITCH_TO_H
  #define _H8300_SWITCH_TO_H
  
  /*
   * switch_to(n) should switch tasks to task ptr, first checking that
   * ptr isn't the current task, in which case it does nothing.  This
   * also clears the TS-flag if the task we switched to has used the
   * math co-processor latest.
   */
  /*
   * switch_to() saves the extra registers, that are not saved
   * automatically by SAVE_SWITCH_STACK in resume(), ie. d0-d5 and
   * a0-a1. Some of these are used by schedule() and its predecessors
   * and so we might get see unexpected behaviors when a task returns
   * with unexpected register values.
   *
   * syscall stores these registers itself and none of them are used
   * by syscall after the function in the syscall has been called.
   *
   * Beware that resume now expects *next to be in d1 and the offset of
   * tss to be in a1. This saves a few instructions as we no longer have
   * to push them onto the stack and read them back right after.
   *
   * 02/17/96 - Jes Sorensen (jds@kom.auc.dk)
   *
   * Changed 96/09/19 by Andreas Schwab
   * pass prev in a0, next in a1, offset of tss in d1, and whether
   * the mm structures are shared in d2 (to avoid atc flushing).
   *
   * H8/300 Porting 2002/09/04 Yoshinori Sato
   */
  
  asmlinkage void resume(void);
  #define switch_to(prev,next,last) {                         \
    void *_last;						    \
    __asm__ __volatile__(					    \
    			"mov.l	%1, er0\n\t"		    \
  			"mov.l	%2, er1\n\t"		    \
                          "mov.l  %3, er2\n\t"                \
  			"jsr @_resume\n\t"                  \
                          "mov.l  er2,%0\n\t"                 \
  		       : "=r" (_last)			    \
  		       : "r" (&(prev->thread)),		    \
  			 "r" (&(next->thread)),		    \
                           "g" (prev)                         \
  		       : "cc", "er0", "er1", "er2", "er3"); \
    (last) = _last; 					    \
  }
  
  #endif /* _H8300_SWITCH_TO_H */
  