Re: Why does IRA force all pseudos live across a setjmp call to be spilled?

[Peter Bergner <bergner@vnet.ibm.com>]

On 3/4/18 7:57 AM, Eric Botcazou wrote:
>> I can't argue with anything in that comment, other than the conclusion. :-)
>> It's not the compiler's job to implement the setjmp/longjmp save/restore.
>> Maybe Kenny was working around a problem with some target's buggy setjmp
>> and spilling everything "fixed" it?
> 
> What are the requirements imposed on setjmp exactly and by whom?  The psABI on 
> SPARC (the SCD) has an explicit note saying that setjmp/sigsetjmp/vfork don't 
> (have to) preserve the usual non-volatile registers.

I'm not a language lawyer and I don't play one on TV either, but I believe
the requirements come from multiple sources.  You've pointed out your ABI
and Andreas pointed out the C standard also places requirements:

    https://gcc.gnu.org/ml/gcc/2018-03/msg00030.html

I wouldn't be surprised if there are more specs/standards that place
restrictions too.  Clearly returning from the function that calls
setjmp before calling longjmp must be illegal, since that would result
in clobbering of the stack frame the longjmp would attempt to restore to.
I don't know off hand who/what states that restriction.

Peter