AArch64/ARM64: port across stub handling for ELF C++ exceptions.

The most important part here is that we should actuall emit the stubs we refer
to in the exception table, but as a side issue this uses more sensible & GCC
compatible representations for some of the bits of information.

llvm-svn: 206380

llvm/lib/MC/MCObjectFileInfo.cpp

@@ -289,8 +289,9 @@ void MCObjectFileInfo::InitELFMCObjectFileInfo(Triple T) {
       TTypeEncoding = (CMModel == CodeModel::Small)
         ? dwarf::DW_EH_PE_udata4 : dwarf::DW_EH_PE_absptr;
     }
-  }  else if (T.getArch() == Triple::aarch64 ||
-              T.getArch() == Triple::aarch64_be ) {
+  } else if (T.getArch() == Triple::aarch64 ||
+             T.getArch() == Triple::aarch64_be ||
+             T.getArch() == Triple::arm64) {
     // The small model guarantees static code/data size < 4GB, but not where it
     // will be in memory. Most of these could end up >2GB away so even a signed
     // pc-relative 32-bit address is insufficient, theoretically.