Re: How should -ffixed-@var{reg} global registers be identifiedfor setjump coding?

[Paul Schlie <schlie at comcast dot net>]

Alternatively, should it be sufficient to universally include a declaration
of the desired global register variables during the compilation of all
source files (including set/longjump routines) such that the compiler will
uniformly exclude global registers from all register allocations, and
thereby also have their definition visible to set/longjump implementation
So that they may be correspondingly properly excluded.

(anyone know of any subtle way in which this strategy could possibly fail?)

(is there any convenient way to ascertain which callee-saved registers may
have been utilized by built-in functions, so they would be known as not
being save to designate as safely alternatively declared as being global
registers?)


> From: Paul Schlie <schlie@comcast.net>
> Thank you, but if the declared global-registers are consistently declared
> at compile-time, including during the compile of an in-line asm coding of
> set/longjump (i.e. not embedded in a pre-compiled library), then as long as
> they can be procedurally identified, as the register allocator is hopefully
> doing to avoid using them itself, they should be able to be correspondingly
> identified and excluded from the save/restore jumpbuf state during its
> compilation if enabled through the use of a __reserved compiler function call
> or shared variable hopefully (I would like to think/hope), as otherwise the
> use of compile-time global registers and set/longjump like functionality is
> needlessly otherwise mutually exclusive, even if compiled with the same
> compile-time switches?
> 
> (if there is no present method by which a source file can access this compiler
> defined data, is their a recommended method to define new reserved
> __function calls which may be invoked by a source file to access private
> compiler data?)
> 
>> From: Ramana Radhakrishnan <ramana.r@gmail.com>
>> This was raised in the mailing list earlier this month .
>> http://gcc.gnu.org/ml/gcc/2005-01/msg00902.html contains the reply .
>> 
>> Its not possible for ffixed-reg to be used with setjmp / longjmp with
>> the features that you want right now AFAIK. The reply to that thread
>> deals with a case that you might like to see.
>> 
>>> On Sat, 29 Jan 2005 23:53:53 -0500, Paul Schlie <schlie@comcast.net> wrote:
>>> Although it may be staring me in the face, what's is the proper method
>>> to identify compile-time -ffixed-@var{reg} declared global-registers
>>> so that they may be properly excluded from being saved/restored by a
>>> set/longjump routine implementation?
>>> 
>>> Any insight would be appreciated, thanks, -paul-