[Bug target/51784] PIC register not correctly preserved in nested funcs / with non-local goto

["iains at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51784

--- Comment #33 from Iain Sandoe <iains at gcc dot gnu.org> 2012-01-15 11:25:31 UTC ---
Created attachment 26330
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=26330
second (non working) go

I'm finding this moderately hard.

I understand what you're suggesting that I should do - but between gccint.pdf,
looking at other .md files and so on there is really rather scarce information
-- trial & error is not a productive way forward .. so I'm still a bit stuck.

The attached does the right thing with the testcase - it inserts the restore
when PIC is used and not when it isn't.

But the compiler fails to bootstrap because eh_personality.cc in the c++
library seems to cause the insert of the nonlocal_rx (for eh) but then, somehow
the initial use of the pic register is optimized away .. and thus we end up
with a load of "L000003$pd" can't be undefined...

... so ... how can I ensure that the test of "uses_pic_" is only done after
optimization?

(or any other help would be welcome).