Index: docs/ReleaseNotes.rst
===================================================================
--- docs/ReleaseNotes.rst
+++ docs/ReleaseNotes.rst
@@ -104,6 +104,7 @@
 
  Moved some optimizations from O3 to O2 (D18562)
 
+* Enable sibling call optimization on ppc64 ELFv1/ELFv2 abi
 
 Changes to the X86 Target
 -------------------------
Index: lib/Target/PowerPC/PPCISelLowering.cpp
===================================================================
--- lib/Target/PowerPC/PPCISelLowering.cpp
+++ lib/Target/PowerPC/PPCISelLowering.cpp
@@ -55,7 +55,7 @@
 static cl::opt<bool> DisablePPCUnaligned("disable-ppc-unaligned",
 cl::desc("disable unaligned load/store generation on PPC"), cl::Hidden);
 
-static cl::opt<bool> DisableSCO("disable-ppc-sco", cl::init(true),
+static cl::opt<bool> DisableSCO("disable-ppc-sco",
 cl::desc("disable sibling call optimization on ppc"), cl::Hidden);
 
 STATISTIC(NumTailCalls, "Number of tail calls");