rs6000: Don't clobber return value when eh_return called [PR114846]

rs6000: Don't clobber return value when eh_return called [PR114846]

As the associated test case in PR114846 shows, currently
with eh_return involved some register restoring for EH
RETURN DATA in epilogue can clobber the one which holding
the return value.  Referring to the existing handlings in
some other targets, this patch makes eh_return expander
call one new define_insn_and_split eh_return_internal which
directly calls rs6000_emit_epilogue with epilogue_type
EPILOGUE_TYPE_EH_RETURN instead of the previous treating
normal return with crtl->calls_eh_return specially.

	PR target/114846

gcc/ChangeLog:

	* config/rs6000/rs6000-logue.cc (rs6000_emit_epilogue): As
	EPILOGUE_TYPE_EH_RETURN would be passed as epilogue_type directly
	now, adjust the relevant handlings on it.
	* config/rs6000/rs6000.md (eh_return expander): Append by calling
	gen_eh_return_internal and emit_barrier.
	(eh_return_internal): New define_insn_and_split, call function
	rs6000_emit_epilogue with epilogue type EPILOGUE_TYPE_EH_RETURN.

gcc/testsuite/ChangeLog:

	* gcc.target/powerpc/pr114846.c: New test.

(cherry picked from commit e5fc5d42d25c86ae48178db04ce64d340a834614)