Alain Ketterlin <alain.ketter...@gmail.com> writes: > When compiling at -O2 and -O3 optimization, I've found several > instances of routines ending with: > > retq > jmp <address-of-next-routine> > > with no branch pointing to the jmp instruction. Is there any specific > reason for such code? Is there a way to avoid this? > > This is gcc 4.4.5, as installed on Ubuntu 10.10, compiling the SPEC > OMP and CPU-2006 benchmarks.
This question borders on being more appropriate for the mailing list gcc-h...@gcc.gnu.org than for the gcc@gcc.gnu.org mailing list. Please consider whether to use gcc-help for future questions. Thanks. It always helps to give a specific example, and to mention the specific target--I infer x86, but 32-bit or 64-bit? Which specific processor, or in other words which -mtune option? In any case I would guess that it is due to -falign-functions. The x86 GNU assembler does alignment by inserting nops, and if it needs to align more than some number of bytes it does it using a jump instruction. For some x86 tuning targets the default for -falign-functions is 32, and gas will certainly use a jmp if it has to skip more than 15 bytes. Ian
