Editing Linker (computing) (section)

== {{Anchor|Relaxation|Jump-sizing}}Relocation ==
As the compiler has no information on the layout of objects in the final output, it cannot take advantage of shorter or more efficient instructions that place a requirement on the address of another object. For example, a jump instruction can reference an absolute address or an offset from the current location, and the offset could be expressed with different lengths depending on the distance to the target. By first generating the most conservative instruction (usually the largest relative or absolute variant, depending on platform) and adding ''relaxation hints'', it is possible to substitute shorter or more efficient instructions during the final link. In regard to jump optimizations this is also called ''automatic jump-sizing''.<ref name="Salomon_1992"/> This step can be performed only after all input objects have been read and assigned temporary addresses; the '''linker relaxation''' pass subsequently reassigns addresses, which may in turn allow more potential relaxations to occur. In general, the substituted sequences are shorter, which allows this process to always converge on the best solution given a fixed order of objects; if this is not the case, relaxations can conflict, and the linker needs to weigh the advantages of either option.

While instruction relaxation typically occurs at link-time, inner-module relaxation can already take place as part of the optimizing process at [[compile-time]]. In some cases, relaxation can also occur at [[load-time]] as part of the relocation process or combined with [[dynamic dead-code elimination]] techniques.