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Re: Question on fixup_abnormal_edges
Michael Matz wrote:
> > ;; End of basic block 175, registers live:
> > 29 [$29] 30 [$30] 31 [AP] 63 [FP]
>
> Ok, no $22 here. So either the caller-save code should take the current
> liveness into account before emitting loads/stores around calls (which I'm
> not sure it is able to, considering non-optimizing compilation) or not
> emit loads after non-return calls at all (and stores are probably useless
> to, except maybe for unwinding the stack).
Actually, this list is always there, and is sometimes augmented by a couple
of pseudos.
In the case eventually causing trouble, a pseudo is live throughout the block
with the noreturn abnormal call and this pseudo is assigned hard reg 22.
I tried a patch inhibiting the emission of the restore insns after a noreturn
call in save_call_clobbered_regs, and it seems to work fine. At least, it
fixes the SEGV we've been observing and does not trigger any regression
against our testsuite for GNAT.
It is very simple, and I can post it here if you think it could be useful.
I would also test/submit it more formally through gcc-patches if you think
appropriate.
Besides, Jan, you mentioned a potential problem with liveness computation
elsewhere. I'd be happy to investigate this further if you think need be.
As I am not very familiar with this code in GCC, some clues as to where/how
noreturn calls are supposed to impact the computation would be very welcome.
Thanks for your help,
Kind Regards,
Olivier