Re: Request for clarification - call frame instruction DW_CFA_remember_state

[David B Anderson <davea at quasar dot engr dot sgi dot com>]

Ron writes:
>Besides, if CFA is (ncessarily) "merely" one of the logical registers,
>why are there several DW_CFA instructions that set/modify the
>CFA specifically and a distinct set of instructions that apply to the
>registers? If the CFA is one of "the registers", then all of the former
>are redundant, yes?

Well, 'merely' is not a word I would use  as CFA is a bit
special since other stuff refers to it implicitly.  But it is
given a 'dwarf register number' as that is the way it is given
a 'rule' number.

I see no way for the CFA 'rule' number to be other than a
register number, though it is not (that is, not necessarily,
depending on the implementation) a real register.  Logically.
There is just one 'namespace' here of rules/registers and if
they overlap...disaster.

I grant it's not as clear as I once thought it was.
Specifically the rules/registers/columns description has at
least one more interpretation than I could see till earlier
today...  But I think only one really 'works'.   Clarifying
this would be good.

>Me thinks we agree that we want CFA to be saved/restored and only the
>means to assure clarity is at issue. I am open to suggestions...

Agreed.

davea@sgi.com