as: s390 Instruction Marker

 
 9.40.3.7 Instruction Marker
 ...........................
 
 The thread local storage instruction markers are used by the linker to
 perform code optimization.
 
 ':tls_load'
      The :tls_load marker is used to flag the load instruction in the
      initial exec TLS model that retrieves the offset from the thread
      pointer to a thread local storage variable from the GOT.
 ':tls_gdcall'
      The :tls_gdcall marker is used to flag the branch-and-save
      instruction to the __tls_get_offset function in the global dynamic
      TLS model.
 ':tls_ldcall'
      The :tls_ldcall marker is used to flag the branch-and-save
      instruction to the __tls_get_offset function in the local dynamic
      TLS model.
 
    For more information about the thread local storage instruction
 marker and the linker optimizations see the ELF extension documentation
 'ELF Handling For Thread-Local Storage'.