Greetings to all.
I am facing a problem with LLVM 3.5 and suspect it is a bug. Here is my observation. I am trying to support a target specific function attribute for a particular target machine. Having followed the steps specified in the compiler documentation, I see the attribute is passed to the backend if we include the attribute in the function definition. But this attribute is not propagate to the backend if I include it only in the function’s prototype/declaration (in the C program). This virtual function (given below) invocation in clang/lib/CodeGen/CodeGenModule.cpp in clang is responsible for attaching the target specific attributes to the backend CodeGen objects (functions, variables etc.) getTargetCodeGenInfo().SetTargetAttributes(D, GO, *this) I found that this virtual function is getting invoked only for function definitions and not for function declarations. Actual requirement: Along with regular C functions we have special functions supported in the target and its definition and invocation will always come in different compilation units. There must be a way to recognize these special functions at the call-sites during codegen in the backend. By attaching some info in the function prototype, we can recognize these special functions at the call-site during backend codegen. That’s why I thought of a new target specific attribute to achieve this purpose. *Is it really a bug?* When I compile a program having function declarations/prototypes with generic attributes like __attribute__((*const*)), clang will add it to that function’s attributelist in the IR and it will be available in the backend. Similarly I expected the target specific attribute should also be added to the attributelist available in the backend and I should be able to identify it using *F.hasFnAttribute("XYZ")*, where XYZ is the new attribute name. Since I work with LLVM 3.5 code-base, I am not sure whether this issue (if it is really a bug) has already been fixed with recent compiler releases. Please write to me. Thanks, Christu
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