I used to naively assume that Clang always handed off the same IR to the LLVM optimisation pipeline regardless of optimisation level. In an attempt to gain a bit more understanding into exactly what kinds of decisions depend on optimisation level in Clang, I surveyed the IR emission code paths.
I recently started exploring link-time optimisation (LTO), which I used to think was just a single boolean choice in the compilation and linking workflow, and perhaps it was like that a while ago… I’ve learned that these days, there are many different dimensions of LTO across compilers and linkers today and more variations are being proposed all the time. In this “living guide”, I aim to cover the LTO-related features I have encountered thus far....