Re: Long double support on m68k

[Andrew Cagney <ac131313 at cygnus dot com>]

> Andrew Cagney <ac131313@cygnus.com> writes:
> 
> |> > This patch enables long double support for m68k.
> |> > Andreas.
> |> > 2001-07-23  Andreas Schwab  <schwab@suse.de>
> |> > * config/m68k/tm-m68k.h (TARGET_LONG_DOUBLE_FORMAT): Define.
> |> > (TARGET_LONG_DOUBLE_BIT): Define.
> |> > (REGISTER_VIRTUAL_SIZE): Return 12 for floating point registers.
> |> > (MAX_REGISTER_VIRTUAL_SIZE): Increase to 12.
> |> > (REGISTER_VIRTUAL_TYPE): Return builtin_type_long_double for
> |> > floating point registers.
> |> > (REGISTER_CONVERTIBLE, REGISTER_CONVERT_TO_VIRTUAL,
> |> > REGISTER_CONVERT_TO_RAW): Remove.
> |> > * config/m68k/xm-linux.h (HOST_LONG_DOUBLE_FORMAT): Define.
> |> |> |> The patch changes something included by all the other config/m68k/tm-*.h
> |> header files.  Can you explain why it won't break some of those targets.
> 
> Well, that's how the m68k looks like on all targets (if they support
> floating point at all).  All targets that make use of the fpu do it
> similar as m68k-linux and don't touch any of the macros I changed, so I
> think this should be safe.  The patch only changes the representation of
> floating point values at gdb's point of view, not how the target is using
> it.


So, what you're saying is that:

o 
only tm-m68k defines the current
	REGISTER_CONVERT* macros.  All
	m68k targets import/use this.

o 
the existing REGISTER_CONVERT* macro's
	only work when the raw register buffer
	is laid out using a specific format.

o 
A target's FP only works when
	the target has a raw register buffer
	that correctly matches REGISTER_CONVERT*

o 
If a target has somehow managed to get
	a raw register buffer that doesn't match
	REGISTER_CONVERT* then, even
	before this change, it is broken.

So, if a target's raw FP registers are in the correct format for 
REGISTER_CONVERT* then they are also in the correct format for this 
change and such targets will continue to work.  If a target's raw FP 
registers were not in the correct format then, that target is already 
broken and this change doesn't make things better or worse.

Correct?

	Andrew