altivec: switch to disable VRSAVE generation

[Aldy Hernandez <aldyh at redhat dot com>]

both linux and eabi altivec do not need vrsave instructions to
be generated, so their generation just bloats both code and the
stack frame.

this patch adds a switch to disable its generation.  the default
is still on, but i could default it to NO if there is no objection.

it's probably best we apply this patch only to the trunk.

ok for trunk?

2002-04-30  Aldy Hernandez  <aldyh@redhat.com>

	* doc/invoke.texi (Option Summary): Add -mvrsave=.
	(RS/6000 and PowerPC Options): Document -mvrsave=.

	* config/rs6000/rs6000.c (rs6000_altivec_vrsave): New global.
	(rs6000_altivec_vrsave_string): Same.
	(rs6000_override_options): Call rs6000_parse_vrsave_option.
	(rs6000_parse_vrsave_option): New.
	(rs6000_stack_info): Only generate vrsave instructions when
	TARGET_ALTIVEC_VRSAVE.

	* config/rs6000/rs6000.h (TARGET_OPTIONS): Add -mvrsave= option.
	(rs6000_altivec_vrsave_string): Define extern.
	(rs6000_altivec_vrsave): Same.
	(TARGET_ALTIVEC_VRSAVE): New.


Index: doc/invoke.texi
===================================================================
RCS file: /cvs/uberbaum/gcc/doc/invoke.texi,v
retrieving revision 1.137
diff -c -p -r1.137 invoke.texi
*** doc/invoke.texi	31 Mar 2002 03:11:19 -0000	1.137
--- doc/invoke.texi	30 Apr 2002 04:56:13 -0000
*************** in the following sections.
*** 447,452 ****
--- 447,453 ----
  -mcall-aix -mcall-sysv -mcall-netbsd @gol
  -maix-struct-return -msvr4-struct-return
  -mabi=altivec -mabi=no-altivec @gol
+ -mvrsave=yes -mvrsave=no @gol
  -mprototype  -mno-prototype @gol
  -msim  -mmvme  -mads  -myellowknife  -memb -msdata @gol
  -msdata=@var{opt}  -mvxworks -G @var{num} -pthread}
*************** These switches enable or disable the use
*** 6428,6433 ****
--- 6429,6441 ----
  allow access to the AltiVec instruction set.  You may also need to set
  @option{-mabi=altivec} to adjust the current ABI with AltiVec ABI
  enhancements.
+ 
+ @item -mvrsave=@var{yes/no}
+ @itemx -mvrsave
+ @opindex mvrsave
+ This switch enables or disables the generation of VRSAVE save and
+ restore instructions when using the AltiVec instruction set.  If this
+ switch is unspecified, the default is to generate VRSAVE instructions.
  
  @item -mfull-toc
  @itemx -mno-fp-in-toc
Index: config/rs6000/rs6000.h
===================================================================
RCS file: /cvs/uberbaum/gcc/config/rs6000/rs6000.h,v
retrieving revision 1.199
diff -c -p -r1.199 rs6000.h
*** config/rs6000/rs6000.h	12 Apr 2002 16:57:47 -0000	1.199
--- config/rs6000/rs6000.h	30 Apr 2002 04:56:16 -0000
*************** extern enum processor_type rs6000_cpu;
*** 430,435 ****
--- 430,437 ----
     {"abi=", &rs6000_abi_string, N_("Specify ABI to use") },		\
     {"long-double-", &rs6000_long_double_size_string,			\
      N_("Specify size of long double (64 or 128 bits)") },		\
+    {"vrsave=", &rs6000_altivec_vrsave_string,                         \
+     N_("Specify yes/no if VRSAVE instructions should be generated for AltiVec") }, \
     SUBTARGET_OPTIONS							\
  }
  
*************** extern int rs6000_debug_arg;		/* debug a
*** 458,466 ****
--- 460,471 ----
  extern const char *rs6000_long_double_size_string;
  extern int rs6000_long_double_type_size;
  extern int rs6000_altivec_abi;
+ extern const char *rs6000_altivec_vrsave_string;
+ extern int rs6000_altivec_vrsave;
  
  #define TARGET_LONG_DOUBLE_128 (rs6000_long_double_type_size == 128)
  #define TARGET_ALTIVEC_ABI rs6000_altivec_abi
+ #define TARGET_ALTIVEC_VRSAVE rs6000_altivec_vrsave
  
  /* Sometimes certain combinations of command options do not make sense
     on a particular target machine.  You can define a macro
*************** extern int rs6000_altivec_abi;
*** 518,523 ****
--- 523,534 ----
     For RS/6000 we can decide arbitrarily since there are no machine
     instructions for them.  Might as well be consistent with bits and bytes.  */
  #define WORDS_BIG_ENDIAN 1
+ 
+ /* Define to TRUE on a big-endian system when structure arguments
+    passed (and returned) in registers are passed in a little-endian
+    manner instead of a big-endian manner.  */
+ 
+ #define FUNCTION_ARG_REG_LITTLE_ENDIAN 1
  
  #define MAX_BITS_PER_WORD 64
  
Index: config/rs6000/rs6000.c
===================================================================
RCS file: /cvs/uberbaum/gcc/config/rs6000/rs6000.c,v
retrieving revision 1.306
diff -c -p -r1.306 rs6000.c
*** config/rs6000/rs6000.c	15 Apr 2002 22:39:09 -0000	1.306
--- config/rs6000/rs6000.c	30 Apr 2002 04:56:21 -0000
*************** int rs6000_long_double_type_size;
*** 74,79 ****
--- 74,85 ----
  /* Whether -mabi=altivec has appeared */
  int rs6000_altivec_abi;
  
+ /* Whether VRSAVE instructions should be generated.  */
+ int rs6000_altivec_vrsave;
+ 
+ /* String from -mvrsave= option.  */
+ const char *rs6000_altivec_vrsave_string;
+ 
  /* Set to non-zero once AIX common-mode calls have been defined.  */
  static int common_mode_defined;
  
*************** static rtx altivec_expand_predicate_buil
*** 168,173 ****
--- 174,180 ----
  static rtx altivec_expand_ternop_builtin PARAMS ((enum insn_code, tree, rtx));
  static rtx altivec_expand_stv_builtin PARAMS ((enum insn_code, tree));
  static void rs6000_parse_abi_options PARAMS ((void));
+ static void rs6000_parse_vrsave_option PARAMS ((void));
  static int first_altivec_reg_to_save PARAMS ((void));
  static unsigned int compute_vrsave_mask PARAMS ((void));
  static void is_altivec_return_reg PARAMS ((rtx, void *));
*************** rs6000_override_options (default_cpu)
*** 534,539 ****
--- 541,549 ----
    /* Handle -mabi= options.  */
    rs6000_parse_abi_options ();
  
+   /* Handle -mvrsave= option.  */
+   rs6000_parse_vrsave_option ();
+ 
  #ifdef TARGET_REGNAMES
    /* If the user desires alternate register names, copy in the
       alternate names now.  */
*************** rs6000_override_options (default_cpu)
*** 581,586 ****
--- 591,611 ----
    free_machine_status = rs6000_free_machine_status;
  }
  
+ /* Handle -mvrsave= options.  */
+ static void
+ rs6000_parse_vrsave_option ()
+ {
+   /* Generate VRSAVE instructions by default.  */
+   if (rs6000_altivec_vrsave_string == 0
+       || ! strcmp (rs6000_altivec_vrsave_string, "yes"))
+     rs6000_altivec_vrsave = 1;
+   else if (! strcmp (rs6000_altivec_vrsave_string, "no"))
+     rs6000_altivec_vrsave = 0;
+   else
+     error ("unknown -mvrsave= option specified: '%s'",
+ 	   rs6000_altivec_vrsave_string);
+ }
+ 
  /* Handle -mabi= options.  */
  static void
  rs6000_parse_abi_options ()
*************** rs6000_stack_info ()
*** 7759,7765 ****
    info_ptr->parm_size    = RS6000_ALIGN (current_function_outgoing_args_size,
  					 8);
  
!   if (TARGET_ALTIVEC_ABI)
      {
        info_ptr->vrsave_mask = compute_vrsave_mask ();
        info_ptr->vrsave_size  = info_ptr->vrsave_mask ? 4 : 0;
--- 7784,7790 ----
    info_ptr->parm_size    = RS6000_ALIGN (current_function_outgoing_args_size,
  					 8);
  
!   if (TARGET_ALTIVEC_ABI && TARGET_ALTIVEC_VRSAVE)
      {
        info_ptr->vrsave_mask = compute_vrsave_mask ();
        info_ptr->vrsave_size  = info_ptr->vrsave_mask ? 4 : 0;