Re: [patch rfc] Add NUM_REGS pseudo regs to MIPS

[Andrew Cagney <ac131313@redhat.com>]

> Andrew Cagney wrote:
> 
>> [ ... ] This adds NUM_REGS pseudo registers to the MIPS [ ... ]
> 
> 
> OK, not a direct reply to your rfc, but it's in the right part of the
> forest to be causing my problem, so...
> 
> I've built a Linux cross MIPS toolchain from a combined source tree,
> checked out of the sources.redhat.com tree yesterday (6 July), and when
> I attempt to do anything in the sim with the register set, I hit an
> assert:
> 
> ../../combined/gdb/mips-tdep.c:5669: internal-error: mips_register_sim_regno: Assertion `regnum >= 0 && regnum < NUM_REGS' failed.
> 
> Setting breakpoints and doing a nested gdb on the thing reveals that
> it's trying to display register 90.  The path there is kinda ugly,
> but here's the trace into gdbarch_num_regs(), which is about to
> return 90:

Ok, I can see what is happening, but not why.

For some reason mips_register_sim_regno is being called with a pseudo 
register value.  I think that is just wrong. 
mips_pseudo_register_read/write should have converted that pseudo into a 
raw :-/

Unfortunatly the below backtrace doesn't explain why (notice how 
mips_register_sim_regno doesn't appear?).  Run the gdb and when it 
internal errors, let it drop a core file, and then run gdb on that vis: 
gdb mips-linux-gnu-gdb core.  Otherwize run gdb on gdb and set the 
breakpoint on `internal_error'.

Andrew


> #0  gdbarch_num_regs (gdbarch=0x82fdc48) at ../../combined/gdb/gdbarch.c:3077
> #1  0x080da346 in mips_print_registers_info (gdbarch=0x82fdc48, file=0x82fc890, 
>     frame=0x82e0f40, regnum=-1, all=0) at ../../combined/gdb/mips-tdep.c:4345
> #2  0x080c9fb3 in gdbarch_print_registers_info (gdbarch=0x82fdc48, file=0x82fc890, 
>     frame=0x82e0f40, regnum=-1, all=0) at ../../combined/gdb/gdbarch.c:4007
> #3  0x080b7e92 in registers_info (addr_exp=0x0, fpregs=0)
>     at ../../combined/gdb/infcmd.c:1620

> Here's what the gdbarch structure looks like (well, the first bits, anyhow):
> 
> (top-gdb) print gdbarch
> $8 = (struct gdbarch *) 0x82fdc48
> (top-gdb) print *gdbarch
> $9 = {initialized_p = 1, bfd_arch_info = 0x8286740, byte_order = 0, 
>   osabi = GDB_OSABI_UNKNOWN, tdep = 0x82fdc18, dump_tdep = 0x80dcc9c <mips_dump_tdep>, 
>   nr_data = 6, data = 0x82fded0, swap = 0x82fdef0, short_bit = 16, int_bit = 32, 
>   long_bit = 32, long_long_bit = 64, float_bit = 32, double_bit = 64, 
>   long_double_bit = 64, ptr_bit = 32, addr_bit = 32, bfd_vma_bit = 32, char_signed = 1, 
>   read_pc = 0x80d53c8 <mips_read_pc>, write_pc = 0x8095214 <generic_target_write_pc>, 
>   read_sp = 0x80d5204 <mips_read_sp>, 
>   virtual_frame_pointer = 0x80ce958 <legacy_virtual_frame_pointer>, 
>   pseudo_register_read = 0x80d4aec <mips_pseudo_register_read>, 
>   pseudo_register_write = 0x80d4b78 <mips_pseudo_register_write>, num_regs = 90, 
>   num_pseudo_regs = 90, sp_regnum = -1, pc_regnum = -1, ps_regnum = -1, fp0_regnum = -1, 
>   npc_regnum = -1, stab_reg_to_regnum = 0x80dbda4 <mips_stab_reg_to_regnum>, 
>   ecoff_reg_to_regnum = 0x80dbe0c <mips_dwarf_dwarf2_ecoff_reg_to_regnum>, 
>   dwarf_reg_to_regnum = 0x80dbe0c <mips_dwarf_dwarf2_ecoff_reg_to_regnum>, 
>   sdb_reg_to_regnum = 0x80ce8a4 <no_op_reg_to_regnum>, 
>   dwarf2_reg_to_regnum = 0x80dbe0c <mips_dwarf_dwarf2_ecoff_reg_to_regnum>, 
>   register_name = 0x80d48ec <mips_register_name>, 
>   register_type = 0x80d5178 <mips_register_type>, deprecated_register_virtual_type = 0, 
> [ etc etc ]
> 
> Being rather weak in gdb-fu, I thought I'd defer to an expert.  Or at least someone
> who's generated patches in the vicinity.
> 
> If you'd like me to try some other stuff or provide more data, that can easily
> be arranged.