on darwin<10, fallback to .weak_definition (PPC,X86)
.weak_def_can_be_hidden was not yet supported by the system assembler

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@196970 91177308-0d34-0410-b5e6-96231b3b80d8
Use llvm_unreachable instead of assert(0)

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@196971 91177308-0d34-0410-b5e6-96231b3b80d8