[build] Move unwinder to toplevel libgcc

[Rainer Orth]

"Joseph S. Myers" <joseph@codesourcery.com> writes:

> On Mon, 20 Jun 2011, Rainer Orth wrote:
>
>> * Move all remaining unwinder-only macros to libgcc: UNW_IVMS_MODE,
>>   MD_UNW_COMPATIBLE_PERSONALITY_P, MD_FROB_UPDATE_CONTEXT.
>
> I don't see any sign of macros being poisoned in system.h.  For macros 
> used in target-independent unwinder code - at least MD_FROB_UPDATE_CONTEXT 
> - that used to be defined in the host tm.h but now no longer should be, I 
> think poisoning in system.h is appropriate.

Good point: I simply had forgotten about this.

>> * The only unwinder-related macro I haven't moved is
>>   LIBGCC2_UNWIND_ATTRIBUTE.  It is only defined gcc/config/mips/mips.h.
>>   I suppose we would need a libgcc equivalent of tm.h for that,
>>   something I didn't want to attack at this point.
>
> What about DWARF_ZERO_REG and PRE_GCC3_DWARF_FRAME_REGISTERS?  
> DWARF_REG_TO_UNWIND_COLUMN may be more complicated because it's used on 
> the host in rs6000.c (although not in target-independent host code) as 
> well as on the target - I suspect that will be a case where duplicating 
> the definition (with a comment in one place pointing to the other place as 
> needing to be kept consistent, and with the host-side copy renamed to 
> facilitate poisoning) may make sense.  And all three are defined in 
> <arch>.h headers so your reason for moving them separately may apply.

I guess.  For the moment, I've concentrated on moving the sources
themselves and the build logic since I've experienced the gcc side
getting in the way of the libgcc side here.

> (There are lots more macros used in the unwinder and on the host for which 
> macros predefined with -fbuilding-libgcc may be appropriate in a later 
> patch.)

Certainly: your wiki entry gives a good overview.  For the moment, I'll
probably concentrate on the build side of things, though.  I may attack
gthr* stuff and fp-bit.[ch] next, both of which I can at least partially
test on my targets.

	Rainer

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Rainer Orth, Center for Biotechnology, Bielefeld University