When I try to do
clang++ main.cpp -emit-llvm
without -S, clang says that he can’t:
clang: error: -emit-llvm cannot be used when linking
why can’t it emit the IR in a complete compilation process?
Is there a particular technical reason or just to avoid confusing jobs?
There is no single LLVM IR for the entire compilation process in such a command line - separate IR is created for each source file, an object file is created, then those (native, non-IR) object files are linked together. So it’s somewhat a invalid concept.
In your case, since there’s only one file anyway, just add -c and you should be fine (your IR won’t include the standard library/other thingsn that would be linked into the program - but those would be native objects and not IR in any case)
I know right, but if I do -emit-llvm clang will emit an IR module as .ll file for each source I give him. So why can’t it just emit the modules for the sources and then continue the compilation? I don’t get the point of this error. Just for curiosity
I know right, but if I do -emit-llvm clang will emit an IR module as .ll
file for each source I give him. So why can't it just emit the modules for
the sources and then continue the compilation? I don't get the point of this
error. Just for curiosity
I think it's that -emit-llvm is treated like a final-output option
(-c, -S, default is linking). There's a -save-temps option that will
store intermediate forms even when linking. I think it saves the
preprocessed source, .bc file and .o file for a link step.