new macro PRE_GCC3_DWARF_FRAME_REGISTERS

[Aldy Hernandez <aldyh at redhat dot com>]

hullo.

as per our conversation, and the previous thread on DWARF_FRAME_REGS.

first, DWARF_FRAME_REGISTERS was undocumented.  added docs.

second, added a new macro PRE_GCC3_DWARF_FRAME_REGISTERS for pre 3.0 EH
compatability.

the idea is to set PRE_GCC3_DWARF_FRAME_REGISTERS to the current value
of DWARF_FRAME_REGS in the ppc port, and add the altivec registers to
DWARF_FRAME_REGS.  this way, EH still works with pre gcc3 compiled
glibc, *and* we new altivec code works.

*please correct me, i'm sure i'm muffing up the description above* :)

bootstrapped on x86.

ok?

-- 
Aldy Hernandez			E-mail: aldyh@redhat.com
Professional Gypsy
Red Hat, Inc.

2001-12-05  Aldy Hernandez  <aldyh@redhat.com>
	    Richard Henderson 	<rth@redhat.com>

	* tm.texi (DWARF_FRAME_REGISTERS): Add documentation.
	(PRE_GCC3_DWARF_FRAME_REGISTERS): Same.

	* unwind-dw2.c (__frame_state_for): Change DWARF_FRAME_REGISTERS
	to PRE_GCC3_DWARF_FRAME_REGISTERS.
	(frame_state): Same.
	(PRE_GCC3_DWARF_FRAME_REGISTERS): Define if not already defined.

Index: unwind-dw2.c
===================================================================
RCS file: /cvs/uberbaum/gcc/unwind-dw2.c,v
retrieving revision 1.12
diff -c -p -r1.12 unwind-dw2.c
*** unwind-dw2.c	2001/11/07 06:33:57	1.12
--- unwind-dw2.c	2001/12/06 18:18:33
***************
*** 42,47 ****
--- 42,52 ----
  #define DWARF_FRAME_REGISTERS FIRST_PSEUDO_REGISTER
  #endif
  
+ /* Dwarf frame registers used for pre gcc 3.0 compiled glibc.  */
+ #ifndef PRE_GCC3_DWARF_FRAME_REGISTERS
+ #define PRE_GCC3_DWARF_FRAME_REGISTERS DWARF_FRAME_REGISTERS
+ #endif
+ 
  /* This is the register and unwind state for a particular frame.  */
  struct _Unwind_Context
  {
*************** typedef struct frame_state
*** 944,953 ****
    void *eh_ptr;
    long cfa_offset;
    long args_size;
!   long reg_or_offset[DWARF_FRAME_REGISTERS+1];
    unsigned short cfa_reg;
    unsigned short retaddr_column;
!   char saved[DWARF_FRAME_REGISTERS+1];
  } frame_state;
  
  struct frame_state * __frame_state_for (void *, struct frame_state *);
--- 949,958 ----
    void *eh_ptr;
    long cfa_offset;
    long args_size;
!   long reg_or_offset[PRE_GCC3_DWARF_FRAME_REGISTERS+1];
    unsigned short cfa_reg;
    unsigned short retaddr_column;
!   char saved[PRE_GCC3_DWARF_FRAME_REGISTERS+1];
  } frame_state;
  
  struct frame_state * __frame_state_for (void *, struct frame_state *);
*************** __frame_state_for (void *pc_target, stru
*** 974,980 ****
    if (fs.cfa_how == CFA_EXP)
      return 0;
  
!   for (reg = 0; reg < DWARF_FRAME_REGISTERS + 1; reg++)
      {
        state_in->saved[reg] = fs.regs.reg[reg].how;
        switch (state_in->saved[reg])
--- 979,985 ----
    if (fs.cfa_how == CFA_EXP)
      return 0;
  
!   for (reg = 0; reg < PRE_GCC3_DWARF_FRAME_REGISTERS + 1; reg++)
      {
        state_in->saved[reg] = fs.regs.reg[reg].how;
        switch (state_in->saved[reg])
Index: doc/tm.texi
===================================================================
RCS file: /cvs/uberbaum/gcc/doc/tm.texi,v
retrieving revision 1.71
diff -c -p -r1.71 tm.texi
*** tm.texi	2001/11/28 09:47:24	1.71
--- tm.texi	2001/12/06 18:18:35
*************** macros and should be used to refer to th
*** 3003,3008 ****
--- 3003,3035 ----
  
  If the static chain is passed in a register, the two previous macros should
  be defined instead.
+ 
+ @findex DWARF_FRAME_REGISTERS
+ @item DWARF_FRAME_REGISTERS
+ This macro specifies the maximum number of hard registers that can be
+ saved in a call frame.  This is used to size data structures used in
+ DWARF2 exception handling.
+ 
+ If this macro is not defined, it defaults to
+ @code{FIRST_PSEUDO_REGISTER}.
+ 
+ @findex PRE_GCC3_DWARF_FRAME_REGISTERS
+ @item PRE_GCC3_DWARF_FRAME_REGISTERS
+ 
+ This macro is similar to @code{DWARF_FRAME_REGISTERS}, but is provided
+ for backward compatibility.
+ 
+ Prior to GCC 3.0, this macro was needed in order to establish a stable
+ exception handling ABI in the face of adding new hard registers for ISA
+ extensions.  In GCC 3.0 and later, the EH ABI is insulated from changes
+ in the number of hard registers.  Nevertheless, this macro can still be
+ used to reduce the runtime memory requirements of the exception handling
+ routines, which can be substantial if the ISA contains a lot of
+ registers that are not call-saved.
+ 
+ If this macro is not defined, it defaults to
+ @code{DWARF_FRAME_REGISTERS}.
+ 
  @end table
  
  @node Elimination