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

[Yaron Keren]

  Anton & Vadim, test now three triples.

  Vadim, there is no label on Windows after the patch, the output is for x64_86-pc-windows is:

          .text
          .def     foo;
          .scl    2;
          .type   32;
          .endef
          .globl  foo
          .align  16, 0x90
  foo:                                    # @foo
  # BB#0:                                 # %entry
          leaq    _ZN11xercesc_2_56XMLUni16fgNotationStringE(%rip), %rax
          leaq    _ZN11xercesc_2_513SchemaSymbols21fgURI_SCHEMAFORSCHEMAE(%rip), %rcx
          orq     %rax, %rcx
          ud2

  should the label still be there?

http://reviews.llvm.org/D3417