[flang] add folding support for quad bessels (#77314)

This is done using libquadmath and the mappings are only available if
libquadmath was found by cmake.
Support for non quad bessels is already available on POSIX platform
using libm extensions.

flang/lib/Evaluate/intrinsics-library.cpp

@@ -321,6 +321,7 @@ template <> struct HostRuntimeLibrary<float, LibraryVersion::LibmExtensions> {
 template <> struct HostRuntimeLibrary<__float128, LibraryVersion::Libm> {
   using F = FuncPointer<__float128, __float128>;
   using F2 = FuncPointer<__float128, __float128, __float128>;
+  using FN = FuncPointer<__float128, int, __float128>;
   static constexpr HostRuntimeFunction table[]{
       FolderFactory<F, F{::acosq}>::Create("acos"),
       FolderFactory<F, F{::acoshq}>::Create("acosh"),
@@ -329,6 +330,12 @@ template <> struct HostRuntimeLibrary<__float128, LibraryVersion::Libm> {
       FolderFactory<F, F{::atanq}>::Create("atan"),
       FolderFactory<F2, F2{::atan2q}>::Create("atan2"),
       FolderFactory<F, F{::atanhq}>::Create("atanh"),
+      FolderFactory<F, F{::j0q}>::Create("bessel_j0"),
+      FolderFactory<F, F{::j1q}>::Create("bessel_j1"),
+      FolderFactory<FN, FN{::jnq}>::Create("bessel_jn"),
+      FolderFactory<F, F{::y0q}>::Create("bessel_y0"),
+      FolderFactory<F, F{::y1q}>::Create("bessel_y1"),
+      FolderFactory<FN, FN{::ynq}>::Create("bessel_yn"),
       FolderFactory<F, F{::cosq}>::Create("cos"),
       FolderFactory<F, F{::coshq}>::Create("cosh"),
       FolderFactory<F, F{::erfq}>::Create("erf"),