[PATCH] Emit a trap instruction for IR 'unreachable'

[Yaron Keren]

    foo:                                    # @foo
    # BB#0:                                 # %entry
            leaq    _ZN11xercesc_2_56XMLUni16fgNotationStringE(%rip), %rax
            leaq    _ZN11xercesc_2_513SchemaSymbols21fgURI_SCHEMAFORSCHEMAE(%rip), %rcx
            orq     %rax, %rcx
            ud2

  ok, this time looks good. Anyhow, ud2 is the last instruction.

http://reviews.llvm.org/D3417