Re: [RFA] MIPS DWARF2 CFI support

[Daniel Jacobowitz <drow@false.org>]

On Mon, Jun 07, 2004 at 08:49:08PM -0700, Martin M. Hunt wrote:
> This is really kevinb's work, with some minor tweaks.  I've tested this
> on over 50 multilib combinations and it looks goood.
> 
> 2004-05-26  Kevin Buettner: 
> 
> 	* dwarf2-frame.c (execute_cfa_program): Fix typo in which the
> 	alignment was being added to the offset instead of multiplied.
> 
> 	* dwarf2-frame.c (struct comp_unit): Add new field ``signed_addr_p''.
> 	(encoding_for_size): Add new parameter ``signed_addr_p''.  Adjust
> 	all callers.  Add code for handling signed encodings.
> 	(dwarf2_build_frame_info): Initialize ``unit.signed_addr_p''.
> 
> 	* dwarf2-frame.c (dwarf2_build_frame_info): Set unit.addr_size.
> 
> 	* config/mips/tm-mips.h (SP_REGNUM): Delete define.
> 	* mips-tdep.h (MIPS_SP_REGNUM): Define.
> 	* mips-tdep.c (mips_gdbarch_init): Set SP_REGNUM via call
> 	to set_gdbarch_sp_regnum().  Use cooked register number.
> 	(SP_REGNUM): Replace all occurrences with MIPS_SP_REGNUM.
> 
> 	* mips-tdep.c (mips_gdbarch_init): Set PC_REGNUM (via
> 	call to set_gdbarch_pc_regnum()) to cooked register number.
> 
> 	* mips-tdep.c (dwarf2-frame.h): Include.
> 	(mips_gdbarch_init): Enable DWARF2 CFI support.

I've got three objections:
  - This is a whole lot of changes.  Please submit them independently,
    with some sort of attempt at explanation.

> -  unit.addr_size = objfile->obfd->arch_info->bits_per_address / 8;
> +  unit.addr_size = TYPE_LENGTH (builtin_type_void_data_ptr);
> +  unit.signed_addr_p = bfd_get_sign_extend_vma (unit.abfd);

  - This is wrong; please don't introduce dependencies on GDB's type
    system in dwarf2-frame.c.  I imagine what's there isn't right
    either because arch_info is completely unreliable on MIPS.  There
    is already a dwarf64_p where this is used; is that right?

    Actually, this sounds like a problem in the dwarf3 draft that
    someone (maybe Jim?) brought up on the dwarf2 list a few weeks ago.
    Jim, do you remember?

And somewhat theoretical:
  - I'd really rather not enable dwarf2 unwinding for MIPS until
    someone makes a go at fixing the MIPS prologue unwinder.  Either
    that or rip it out; because after this patch it will get almost
    zero coverage in the testsuite.  This is an ongoing problem.
    I know that the existing prologue unwinder is broken at the
    beginning of functions and in a number of other situations.


-- 
Daniel Jacobowitz