[Power9]Legalize and emit code for round & convert quad-precision values

Legalize and emit code for round & convert float128 to double precision and
single precision.

Differential Revision: https://reviews.llvm.org/D46997

llvm-svn: 336299
diff --git a/llvm/lib/Target/PowerPC/P9InstrResources.td b/llvm/lib/Target/PowerPC/P9InstrResources.td
index 7b04875..34df845 100644
--- a/llvm/lib/Target/PowerPC/P9InstrResources.td
+++ b/llvm/lib/Target/PowerPC/P9InstrResources.td
@@ -515,7 +515,8 @@
     XSRSQRTESP,
     XSSUBDP,
     XSSUBSP,
-    XSCVDPSPN
+    XSCVDPSPN,
+    XSRSP
 )>;
 
 // Three Cycle PM operation. Only one PM unit per superslice so we use the whole