On 10/13/2017 12:45 PM, Sebastian Huber wrote: > > > ----- Am 13. Okt 2017 um 20:39 schrieb David Edelsohn dje....@gmail.com: > >> On Fri, Oct 13, 2017 at 2:34 PM, Sebastian Huber >> <sebastian.hu...@embedded-brains.de> wrote: >> >>>>> Do these options affect the code generation? >>>> They can affect code generation. By placing each object into its own >>>> section it's no longer viable to use one object to refer to another >>>> because the relative addresses are unknown until link time. Without >>>> those options the assembler can compute the offset between two objects >>>> within a given section when they come from the same translation unit. >>> >>> Is this similar to moving all distinct objects into one compiler generated >>> structure? >> >> It places each function and each datum into a separate section, which >> can be placed or removed independently. It is not combining data or >> altering the order of structures. It allows the linker to position >> functions and data items as individual components instead of a single >> object file "text" or "data" blobs. > > Is the optimization opportunity described by Jeff (which is prevented by the > use of function and data sections) similar to moving all distinct objects > into one compiler generated structure? Yes. And it's something that is inhibited by -fdata-sections because with -fdata-sections the relative locations of any two objects is unknown until link time.
-ffunction-sections will do things like inhibit call->short-call relaxations that are sometimes done by the assembler. jeff
