PPC64: Implemented the Word64Clz TurboFan operator.

src/compiler/ppc/code-generator-ppc.cc

Index: src/compiler/ppc/code-generator-ppc.cc
diff --git a/src/compiler/ppc/code-generator-ppc.cc b/src/compiler/ppc/code-generator-ppc.cc
index 9f3cb0c6fe5dc511441978cd443b155d883e5f82..dbc776ef9efbd3ee83060658eddd35211e328f90 100644
--- a/src/compiler/ppc/code-generator-ppc.cc
+++ b/src/compiler/ppc/code-generator-ppc.cc
@@ -944,6 +944,12 @@ void CodeGenerator::AssembleArchInstruction(Instruction* instr) {
       __ cntlzw_(i.OutputRegister(), i.InputRegister(0));
       DCHECK_EQ(LeaveRC, i.OutputRCBit());
       break;
+#if V8_TARGET_ARCH_PPC64
+    case kPPC_Cntlz64:
+      __ cntlzd_(i.OutputRegister(), i.InputRegister(0));
+      DCHECK_EQ(LeaveRC, i.OutputRCBit());
+      break;
+#endif
     case kPPC_Popcnt32:
       __ popcntw(i.OutputRegister(), i.InputRegister(0));
       DCHECK_EQ(LeaveRC, i.OutputRCBit());