cmd/compile: intrinsify runtime/internal/sys.Ctz{32,64} on ppc64

These functions are identical to math/bits.TrailingZeros{32,64}, which
are already intrinsified on ppc64.

Change-Id: If7ee57e7afe53154874f4b66bacdb6237806128a
Reviewed-on: https://go-review.googlesource.com/70350
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>

src/cmd/compile/internal/gc/ssa.go

@@ -2652,12 +2652,12 @@ func init() {
 		func(s *state, n *Node, args []*ssa.Value) *ssa.Value {
 			return s.newValue1(ssa.OpCtz32, types.Types[TINT], args[0])
 		},
-		sys.AMD64, sys.ARM64, sys.ARM, sys.S390X, sys.MIPS)
+		sys.AMD64, sys.ARM64, sys.ARM, sys.S390X, sys.MIPS, sys.PPC64)
 	addF("runtime/internal/sys", "Ctz64",
 		func(s *state, n *Node, args []*ssa.Value) *ssa.Value {
 			return s.newValue1(ssa.OpCtz64, types.Types[TINT], args[0])
 		},
-		sys.AMD64, sys.ARM64, sys.ARM, sys.S390X, sys.MIPS)
+		sys.AMD64, sys.ARM64, sys.ARM, sys.S390X, sys.MIPS, sys.PPC64)
 	addF("runtime/internal/sys", "Bswap32",
 		func(s *state, n *Node, args []*ssa.Value) *ssa.Value {
 			return s.newValue1(ssa.OpBswap32, types.Types[TUINT32], args[0])