On 12/03/2021 03.29, Segher Boessenkool wrote: > Hi! > > On Tue, Mar 09, 2021 at 06:19:30AM +0000, Christophe Leroy wrote: >> With some defconfig including CONFIG_CC_OPTIMIZE_FOR_SIZE, >> (for instance mvme5100_defconfig and ps3_defconfig), gcc 5 >> generates a call to _restgpr_31_x. > >> I don't know if there is a way to tell GCC not to emit that call, because at >> the end we get more instructions than needed. > > The function is required by the ABI, you need to have it. > > You get *fewer* insns statically, and that is what -Os is about: reduce > the size of the binaries.
Is there any reason to not just always build the vdso with -O2? It's one page/one VMA either way, and the vdso is about making certain system calls cheaper, so if unconditional -O2 could save a few cycles compared to -Os, why not? (And if, as it seems, there's only one user within the DSO of _restgpr_31_x, yes, the overall size of the .text segment probably increases slightly). Rasmus