On Mon, May 11, 2015 at 1:36 PM, Jeff Law <l...@redhat.com> wrote: > On 05/10/2015 10:59 AM, Jan Hubicka wrote: >>> >>> This patch introduces option -fno-plt that allows to expand calls that >>> would >>> go via PLT to load the address of the function immediately at call site >>> (which >>> introduces a GOT load). Cover letter explains the motivation for this >>> patch. >>> >>> New option documentation for invoke.texi is missing from the patch; if >>> this is >>> accepted I'll be happy to send a v2 with documentation added. >>> >>> * calls.c (prepare_call_address): Transform PLT call to GOT >>> lookup and >>> indirect call by forcing address into a pseudo with -fno-plt. >>> * common.opt (flag_plt): New option. >>> >>> diff --git a/gcc/common.opt b/gcc/common.opt >>> index b49ac46..cd8b256 100644 >>> --- a/gcc/common.opt >>> +++ b/gcc/common.opt >>> @@ -1773,12 +1773,16 @@ Common Report Var(flag_pic,1) Negative(fpie) >>> Generate position-independent code if possible (small mode) >>> >>> fpie >>> Common Report Var(flag_pie,1) Negative(fPIC) >>> Generate position-independent code for executables if possible (small >>> mode) >>> >>> +fplt >>> +Common Report Var(flag_plt) Init(1) >>> +Use PLT for PIC calls (-fno-plt: load the address from GOT at call site) >>> + >> >> >> This won't play well with LTO since fplt will become another global flag >> while >> it affects codegen. > > I know Richi explained this to me in the past, but I can't remember the > details of why this is bad. Can you walk me through it again? >
I have proposed a different approach: https://gcc.gnu.org/ml/gcc/2015-05/msg00086.html -- H.J.
