I have been looking into linkers recently and I’ve been amazed at all the crazy options and optimizations that a linker may perform. Compilers are a well understood domain, taught in schools with a plethora of books but few resources exist for linkers aside from what you may find on some excellent technical blogs such as Lance Taylor’s series on writing the gold linker and Fangrui Song’s, also known as MaskRay, very in-depth blog.

Farid Zakaria’s Blog

Linker relaxation is an optimization technique where the linker transforms indirect function calls through the Global Offset Table (GOT) into more efficient direct calls when building static binaries. The R_X86_64_GOTPCRELX relocation type signals to the linker that it can safely replace a 6-byte indirect call instruction with a 5-byte direct call plus a 1-byte padding (either nop or addr32 prefix). This optimization eliminates unnecessary memory loads and improves performance by allowing the CPU to jump directly to the target address when all function locations are known at link time.

Crazy shit linkers do: Relaxation