gcc 3.4 regression: sched2 moving "may throw" instructions into epilogue

[Jim Wilson]

Andrew Haley wrote:
> Insns that may trap must not be move into the epilogue, because stack
> unwinding when throwing exceptions will not work correctly.

It could work if we emitted unwind info for epilogues.  Currently we 
don't do so for targets that use the DWARF2 CFI-based unwind info.  We 
do for targets that use the IA-64 unwind info though.

An alternative would be to emit a blockage insn before the epilogue when 
-fnon-call-exceptions is used.  This will unnecessarily reduce 
performance for targets that have epilogue unwind info, probably only 
IA-64 at this point, but should make your testcase work.

For the blockage insn, you can use the hack that is used in 
expand_builtin_setjmp_receiver and expand_nl_goto_receiver, which is to 
emit an ASM_INPUT insn.
-- 
Jim Wilson, GNU Tools Support, http://www.SpecifixInc.com