/* Setjmp and longjmp for mmix.

   Copyright (C) 2001 Hans-Peter Nilsson.

   Permission to use, copy, modify, and distribute this software is freely
   granted, provided that this notice is preserved with no changes.
   THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
   IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
   WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
   PURPOSE.

   jmp_buf[5]:
   0: fp
   1: rJ (return-address)
   2: sp
   3: rO *before* the setjmp call.
   4: temporary storage.  Reserved between setjmp and longjmp.  */

#ifdef __MMIX_ABI_GNU__
#define arg1 $231
#define arg2 $232
#define outret $231
#define popval 0
#else
#define arg1 $0
#define arg2 $1
#define outret $0
#define popval 1
#endif

      .section .text.setjmp,"ax",@progbits
      .global setjmp
setjmp:
% Store fp, sp and return address.  Recycle the static-chain and
% structure-return registers as temporary register, since we need to keep
% the jmp_buf (parameter 1) and the return address across a "POP".
      SET  $251,arg1
      STOU $253,$251,0
      GET  $252,rJ
      STOU $252,$251,8
      STOU $254,$251,16
      SETL outret,0

% Jump through hoops to get the value of rO *before* the setjmp call.
      GETA $255,0f
      PUT  rJ,$255
      POP  popval,0
0:
      GET  $255,rO
      STOU $255,$251,24
      GO   $255,$252,0
      .size setjmp,.-setjmp

      .section .text.longjmp,"ax",@progbits
      .global longjmp
longjmp:
% Reset arg2 to 1 if it is 0 (see longjmp(2)) and store it in jmp_buf.
% Save arg1 in a global register, since it will be destroyed by the POPs
% (in the mmixware ABI).
      CSZ  arg2,arg2,1
      STOU arg2,arg1,32
      SET  $251,arg1

% Loop and "POP 0,0" until rO is the expected value, like
% the expansion of nonlocal_goto_receiver, except that we put the return
% value in the right register and make sure that the POP causes it to
% enter the right return-value register as seen by the caller.  For the
% GNU ABI, it is unnecessary to do this in the loop and perhaps the memory
% access can be hoisted outside the loop, but this is safe and simple and
% I see no need to optimize longjmps.
      GETA $255,0f
      PUT  rJ,$255
      LDOU $255,$251,24
0:
      GET  $252,rO
      CMPU $252,$252,$255
      BNP  $252,1f
      LDOU outret,$251,32
      POP  popval,0
1:
      LDOU $253,$251,0
      LDOU $255,$251,8
      LDOU $254,$251,16
      GO   $255,$255,0
      .size longjmp,.-longjmp