Author: Breno Leitao <breno.leitao@gmail.com>
Date:   Mon Apr 10 23:22:01 2017 +0000

    Do not clobber r31 if you are not omitting frame pointer

    R31 is the register that is defined in the ABI v2 as the frame pointer.
    It should not be clobbered unless we omit the frame pointer.

    Signed-off-by: Breno Leitao <breno.leitao@gmail.com>

--- greenlet-0.4.12/platform/switch_ppc64_linux.h.old	2017-04-10 19:14:26.808511638 +0000
+++ greenlet-0.4.12/platform/switch_ppc64_linux.h	2017-04-10 19:14:34.556511856 +0000
@@ -57,7 +57,7 @@
 #endif
 
 #define REGS_TO_SAVE "r2", "r14", "r15", "r16", "r17", "r18", "r19", "r20", \
-       "r21", "r22", "r23", "r24", "r25", "r26", "r27", "r28", "r29", "r31", \
+       "r21", "r22", "r23", "r24", "r25", "r26", "r27", "r28", "r29", \
        "fr14", "fr15", "fr16", "fr17", "fr18", "fr19", "fr20", "fr21", \
        "fr22", "fr23", "fr24", "fr25", "fr26", "fr27", "fr28", "fr29", \
        "fr30", "fr31", \