https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69625
--- Comment #1 from Dominik Vogt <vogt at linux dot vnet.ibm.com> --- It's a bug in the S/390 backend that sometimes trashes r6 in vararg functions. We're working on a fix.
vogt at linux dot vnet.ibm.com Wed, 03 Feb 2016 06:15:59 -0800
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69625
--- Comment #1 from Dominik Vogt <vogt at linux dot vnet.ibm.com> --- It's a bug in the S/390 backend that sometimes trashes r6 in vararg functions. We're working on a fix.