[patch rfc] Add the frame's type to the unwinder

[Andrew Cagney]

> Hello,
> 
> The attached patch, moves the frame's type into `struct frame_unwind' and in doing so makes it possible to combine the sequence:
> 
>     prev->type = frame_type_from_pc()
>     prev->unwind = frame_unwind_find_by_pc()
> 
> into a single:
> 
>     prev->unwind = frame_unwind_find_by_pc();
>     // prev->type == prev->unwind->type;
> 
> and hence eliminate the the call to frame_type_from_pc().
> 
> 
> Fine print:
> 
> While the above is true for new code, old code continues to use the same confused combination of frame_type_from_pc(), frame_unwind_find_by_pc(), deprecated_set_frame_type(), and legacy_get_prev_frame().  A legacy frame's type is initialized to UNKNOWN_FRAME, and then zero or more of those functions will override it.  get_frame_type() mapping an UNKNOWN_FRAME onto a NORMAL_FRAME.
> 
> Importantly, if a legacy frame's unwinder returns a known frame type (!UNKNOWN_FRAME) then that will be used in preference to any other value.  This should make it possible for old architectures to incrementally implement new unwinders.
> 
> 
> Tested on d10v, ppc, and i386.  I'll commit in a few days,

I've checked this in.

Andrew


> 2003-04-02  Andrew Cagney  <cagney@redhat.com>
> 
> 	* frame.c (get_prev_frame): Do not call frame_type_from_pc.  Set
> 	the frame's type from the unwinder.
> 	(get_frame_type): Map UNKNOWN_FRAME onto NORMAL_FRAME.
> 	(create_new_frame, legacy_get_prev_frame): When the unwinder's
> 	type isn't UNKNOWN_FRAME, initalize "type" from the unwinder.
> 	(get_frame_base_address): Use get_frame_type.
> 	(get_frame_locals_address, get_frame_args_address): Ditto.
> 	(legacy_saved_regs_unwinder): Set the type to UNKNOWN_TYPE.
> 	* frame.h (enum frame_type): Add UNKNOWN_FRAME.
> 	(struct frame_info): Add comment explaining why the frame contains
> 	a "type" field.
> 	* dummy-frame.c (dummy_frame_unwind): Set the type to DUMMY_FRAME.
> 	* d10v-tdep.c (d10v_frame_unwind): Set the type to NORMAL_FRAME.
> 	* sentinel-frame.c (sentinel_frame_unwinder): Set the type to
> 	NORMAL_FRAME.
> 	* frame-unwind.h: Include "frame.h".
> 	(struct frame_unwind): Add "type" field.
> 	* Makefile.in (frame_unwind_h): Add $(frame_h).
> 	
> Inde