cmake - Emitting a single IR bitcode File with LLVM LLD using CMake

Question

I'm using Ubuntu 16.04 x86_64 and LLVM 5.0 and would like to compile a project to a single LLVM IR bitcode file using CMake. I know there is a way to do this using the GOLD Linker with the LLVM Plugin and add the CMake linker flags "-fuse-ld=gold -Wl,-plugin-opt=emit-llvm" and the CXX flag "-flto".

But when I try to compile the project with the LLVM LLD linker and the "-fuse-ld=lld -Wl,-plugin-opt=emit-llvm" respectively "-flto" Flag, the linker is generating a native executable and no LLVM IR file. I was searching for other LLD options to emit a LLVM IR file but found nothing.

Is there a way (or option) to generate a single LLVM IR file using LLD?

Answer 1

You can use the -save-temps option.

clang -flto -fuse-ld=lld -Wl,-save-temps a.o b.o -o myprogram

This will generate myprogramXYZ.precodegen.bc among other files. You can then use llvm-dis to get it in readable IR format.