[llvm-dev] Attribute C-interface since LLVM-4.0

[Henning Thielemann via llvm-dev]

I try to guess how the new Attribute C-interface since LLVM-3.9 works, but 
it seems I have not guessed correctly so far. See attached example. First 
file uses the API before LLVM-3.9 and second file uses the API starting 
with LLVM-3.9. Essentially I replaced

   LLVMAddInstrAttribute
     (call_exp, LLVMAttributeFunctionIndex, LLVMReadNoneAttribute);

by

   unsigned attrKind = LLVMGetEnumAttributeKindForName("readnone", 8);
   LLVMContextRef context = LLVMGetGlobalContext();
   LLVMAttributeRef attr = LLVMCreateEnumAttribute (context, attrKind, 0);
   LLVMAddAttributeAtIndex(call_exp, LLVMAttributeFunctionIndex, attr);

But in the generated Bitcode file no "readnone" attribute shows up.
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