Add #ifndef NDEBUG/#endif around debug-only code. (#147356)

llvm/lib/CodeGen/SelectionDAG/LegalizeFloatTypes.cpp

diff --git a/llvm/lib/CodeGen/SelectionDAG/LegalizeFloatTypes.cpp b/llvm/lib/CodeGen/SelectionDAG/LegalizeFloatTypes.cpp
index 2a947f3..eee963f 100644
--- a/llvm/lib/CodeGen/SelectionDAG/LegalizeFloatTypes.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/LegalizeFloatTypes.cpp
@@ -718,8 +718,10 @@
                              : RTLIB::getLDEXP(N->getValueType(0));
   assert(LC != RTLIB::UNKNOWN_LIBCALL && "Unexpected fpowi.");
   if (!TLI.getLibcallName(LC)) {
+#ifndef NDEBUG
     RTLIB::Libcall NewLC = RTLIB::getPOW(N->getValueType(0));
     assert(NewLC != RTLIB::UNKNOWN_LIBCALL && "Unexpected fpow type");
+#endif
 
     // Some targets don't have a powi libcall; use pow instead.
     // FIXME: Implement this if some target needs it.