On Tue, Feb 3, 2015 at 11:36 AM, Jakub Jelinek <ja...@redhat.com> wrote: > On Tue, Feb 03, 2015 at 11:25:38AM -0800, Sriraman Tallam wrote: >> This was the original patch to i386.c to let global accesses take >> advantage of copy relocations and avoid the GOT. >> >> >> @@ -13113,7 +13113,11 @@ legitimate_pic_address_disp_p (rtx disp) >> return true; >> } >> else if (!SYMBOL_REF_FAR_ADDR_P (op0) >> - && SYMBOL_REF_LOCAL_P (op0) >> + && (SYMBOL_REF_LOCAL_P (op0) >> + || (HAVE_LD_PIE_COPYRELOC >> + && flag_pie >> + && !SYMBOL_REF_WEAK (op0) >> + && !SYMBOL_REF_FUNCTION_P (op0))) >> && ix86_cmodel != CM_LARGE_PIC) >> >> I do not understand here why weak global data access must go through >> the GOT and not use copy relocations. Ultimately, there is only going >> to be one copy of the global either defined in the executable or the >> shared object right? >> >> Can we remove the check for SYMBOL_REF_WEAK? > > So, what will then happen if the weak undef symbol isn't defined anywhere? > In non-PIE binaries that is fine, the linker will store 0. > But in PIE binaries, the 0 would be biased by the PIE load bias and thus > wouldn't be NULL.
Thanks for clarifying. > You can only optimize weak vars if there is some weak definition in the > current TU. Would this be fine then? Replace !SYMBOL_REF_WEAK (op0) with !(SYMBOL_REF_WEAK (op0) && SYMBOL_REF_EXTERNAL_P (op0)) Thanks Sri > > Jakub
