This is the mail archive of the
gdb-patches@sources.redhat.com
mailing list for the GDB project.
Re: [RFA] mips fp register display
- To: Daniel Jacobowitz <dmj+ at andrew dot cmu dot edu>
- Subject: Re: [RFA] mips fp register display
- From: Don Howard <dhoward at redhat dot com>
- Date: Fri, 22 Jun 2001 10:26:30 -0700 (PDT)
- Cc: <gdb-patches at sources dot redhat dot com>
On Thu, 21 Jun 2001, Daniel Jacobowitz wrote:
> On Thu, Jun 21, 2001 at 03:42:10PM -0700, Don Howard wrote:
> >
> > This is a patch for an obscure mips fp register display problem. 32 bit mips
> > chips support 64 bit float operations using two fp registers. 64 bit mips
> > chips provide a backward compatiblity mode where 64 bit float ops are also
> > supported using 2 float regsiters -- 32 bits stored in each of the 2 64bit fp
> > regs.
> >
> > This patch addresses insight as well as cli gdb. Insight is not 100% correct:
> > single precision floats are displayed in double format =( (cli gdb displays
> > both float and double). I can change REGISTER_VIRTUAL_TYPE() to try to guess
> > the the intended type (builtin_type_{float,double}), but that is really not
> > the right place to fix this problem.
> >
> >
> > 2001-06-21 Don Howard <dhoward@redhat.com>
> >
> >
> > * mips-tdep.c (mips2_read_fp_register): New function. Reads a
> > 64-bit float value stored as two 32-bit fragments in consecutive
> > float registers.
> > (mips2_fp_compat): New function. Determine if a MIPS3 or later
> > cpu is operating in MIPS{1,2} float-compat mode.
> > (mips_get_saved_register): Modified to use new
> > mips2-compat float support.
> > (mips_print_register): Modified to display 64-bit float regs in
> > single and double precision.
>
> I see why this is necessary, but it doesn't address the problem I was
> talking about. I also don't think it's really the right solution.
> If you look a few lines higher in mips_print_register, you see:
>
> /* If an even floating point register, also print as double. */
> if (TYPE_CODE (REGISTER_VIRTUAL_TYPE (regnum)) == TYPE_CODE_FLT
> && !((regnum - FP0_REGNUM) & 1))
> if (REGISTER_RAW_SIZE (regnum) == 4) /* this would be silly on MIPS64 or N32 (Irix 6) */
> {
> char dbuffer[2 * MAX_REGISTER_RAW_SIZE];
>
> read_relative_register_raw_bytes (regnum, dbuffer);
> read_relative_register_raw_bytes (regnum + 1, dbuffer + MIPS_REGSIZE);
> REGISTER_CONVERT_TO_TYPE (regnum, builtin_type_double, dbuffer);
>
> printf_filtered ("(d%d: ", regnum - FP0_REGNUM);
> val_print (builtin_type_double, dbuffer, 0, 0,
> gdb_stdout, 0, 1, 0, Val_pretty_default);
> printf_filtered ("); ");
> }
> fputs_filtered (REGISTER_NAME (regnum), gdb_stdout);
>
> Well, obviously it's not always silly on N32. Change the
> if (REGISTER_RAW_SIZE (regnum) == 4)
> to something like
> if (mips_small_float_registers ())
>
> On the other hand, I think that perhaps if FR is set
> REGISTER_RAW_SIZE (regnum) ought to be 4. Isn't that what it means?
It seems to me that REGISTER_VIRTUAL_SIZE() is the macro that should provide
this info, as the raw register doesn't change. Neither of these check the FR
bit.
>
> Also, we already have REGISTER_CONVERT_TO_TYPE. Rather than hacking in
> a third or perhaps fourth copy of this sort of thing, why not extend
> REGISTER_CONVERT_TO_TYPE?
I would guess (I'm no authority though) that REGISTER_CONVERT_TO_VIRTUAL() and
REGISTER_CONVERT_TO_RAW() might be better places to do this.
I chose to implement a new read_fp_register() function so that insight could
benifit from the fix also. print_register() and do_register_row() affect cli
gdb only.
--
-Don
dhoward@redhat.com
gdb engineering