new arm option -mabort-on-noreturn

["Catherine L. Moore" <clm at cygnus dot com>]

  The arm port was generating a call to abort if a function
that was declared noreturn tried to return.  This patch
causes the compiler to generate the call to abort only if
the -mabort-on-noreturn option is specified.  I checked in this
patch this afternoon.  Nick Clifton approved it.

Catherine

Index: arm.c
===================================================================
RCS file: /egcs/carton/cvsfiles/egcs/gcc/config/arm/arm.c,v
retrieving revision 1.21
diff -p -r1.21 arm.c
*** arm.c	1998/12/16 21:01:29	1.21
--- arm.c	1999/01/13 22:25:37
*************** output_func_epilogue (f, frame_size)
*** 5006,5012 ****
      goto epilogue_done;
  
    /* A volatile function should never return.  Call abort.  */
!   if (volatile_func)
      {
        rtx op = gen_rtx (SYMBOL_REF, Pmode, "abort");
        assemble_external_libcall (op);
--- 5006,5012 ----
      goto epilogue_done;
  
    /* A volatile function should never return.  Call abort.  */
!   if (TARGET_ABORT_NORETURN && volatile_func)
      {
        rtx op = gen_rtx (SYMBOL_REF, Pmode, "abort");
        assemble_external_libcall (op);
Index: arm.h
===================================================================
RCS file: /egcs/carton/cvsfiles/egcs/gcc/config/arm/arm.h,v
retrieving revision 1.16
diff -p -r1.16 arm.h
*** arm.h	1998/12/16 21:01:30	1.16
--- arm.h	1999/01/13 22:26:04
*************** extern char *target_fp_name;
*** 312,317 ****
--- 312,321 ----
     big-endian (for backwards compatibility with older versions of GCC).  */
  #define ARM_FLAG_LITTLE_WORDS	(0x2000)
  
+ /* Nonzero if a call to abort should be generated if a noreturn 
+ function tries to return. */
+ #define ARM_FLAG_ABORT_NORETURN (0x8000)
+ 
  #define TARGET_APCS			(target_flags & ARM_FLAG_APCS_FRAME)
  #define TARGET_POKE_FUNCTION_NAME	(target_flags & ARM_FLAG_POKE)
  #define TARGET_FPE			(target_flags & ARM_FLAG_FPE)
*************** extern char *target_fp_name;
*** 327,332 ****
--- 331,337 ----
  #define TARGET_BIG_END			(target_flags & ARM_FLAG_BIG_END)
  #define TARGET_THUMB_INTERWORK		(target_flags & ARM_FLAG_THUMB)
  #define TARGET_LITTLE_WORDS		(target_flags & ARM_FLAG_LITTLE_WORDS)
+ #define TARGET_ABORT_NORETURN           (target_flags & ARM_FLAG_ABORT_NORETURN)
  
  /* SUBTARGET_SWITCHES is used to add flags on a per-config basis.
     Bit 31 is reserved.  See riscix.h.  */
*************** extern char *target_fp_name;
*** 377,382 ****
--- 382,391 ----
    {"thumb-interwork",		ARM_FLAG_THUMB, 	\
       "Support calls between THUMB and ARM instructions sets" },	\
    {"no-thumb-interwork",       -ARM_FLAG_THUMB, "" },	\
+   {"abort-on-noreturn",         ARM_FLAG_ABORT_NORETURN,     \
+    "Generate a call to abort if a noreturn function returns"}, \
+   {"no-abort-on-noreturn",      -ARM_FLAG_ABORT_NORETURN, ""}, \
+ 
    SUBTARGET_SWITCHES					\
    {"",				TARGET_DEFAULT }	\
  }