| Message ID | 20120422175040.224BE190A4E@elbrus2.mtv.corp.google.com |
|---|---|
| State | New |
| Headers | show |
On Sun, Apr 22, 2012 at 10:50 AM, Paul Pluzhnikov <ppluzhnikov@google.com> wrote: > Greetings, > > The patch below is needed for google/integration branch: > we want to be able build libgomp.a with -fPIC, be able to link it into a > shared library, and be able to dlopen that library without running out of > static TLS space (-ftls-model=initial-exec precludes that last part). Do you understand the reason why it was made -ftls-model=initial-exec in the first place? IIRC the main reason is because the slow down from not using initial-exec model for GOMP is a lot. Thanks, Andrew Pinski > Google ref b/6368405 > Google ref b/6156799 > > Tested: make && make check > > > 2012-04-22 Paul Pluzhnikov <ppluzhnikov@google.com> > > * libgomp/configure.tgt: Don't force initial-exec. > > Index: libgomp/configure.tgt > =================================================================== > --- libgomp/configure.tgt (revision 186636) > +++ libgomp/configure.tgt (working copy) > @@ -10,16 +10,6 @@ > # XCFLAGS Add extra compile flags to use. > # XLDFLAGS Add extra link flags to use. > > -# Optimize TLS usage by avoiding the overhead of dynamic allocation. > -if test $gcc_cv_have_tls = yes ; then > - case "${target}" in > - > - *-*-linux*) > - XCFLAGS="${XCFLAGS} -ftls-model=initial-exec" > - ;; > - esac > -fi > - > # Since we require POSIX threads, assume a POSIX system by default. > config_path="posix" > > > -- > This patch is available for review at http://codereview.appspot.com/6107046
On Sun, Apr 22, 2012 at 10:09:46PM -0700, Andrew Pinski wrote: > On Sun, Apr 22, 2012 at 10:50 AM, Paul Pluzhnikov > <ppluzhnikov@google.com> wrote: > > Greetings, > > > > The patch below is needed for google/integration branch: > > we want to be able build libgomp.a with -fPIC, be able to link it into a > > shared library, and be able to dlopen that library without running out of > > static TLS space (-ftls-model=initial-exec precludes that last part). > > Do you understand the reason why it was made -ftls-model=initial-exec > in the first place? > IIRC the main reason is because the slow down from not using > initial-exec model for GOMP is a lot. Yes, the reason is that initial-exec is much faster than global-exec. Jakub
On Sun, Apr 22, 2012 at 10:09 PM, Andrew Pinski <pinskia@gmail.com> wrote: > IIRC the main reason is because the slow down from not using > initial-exec model for GOMP is a lot. Given a choice between "slows down a lot" and "doesn't work at all", we prefer the former ;-) I see that we are not alone: http://old.nabble.com/-patch--libgomp%3A-removing-nodlopen-flag-for-portability-td10286039.html Generally we don't use OpenMP, but some of our third-party libraries do depend on it. Thanks for the heads-up.
Index: libgomp/configure.tgt =================================================================== --- libgomp/configure.tgt (revision 186636) +++ libgomp/configure.tgt (working copy) @@ -10,16 +10,6 @@ # XCFLAGS Add extra compile flags to use. # XLDFLAGS Add extra link flags to use. -# Optimize TLS usage by avoiding the overhead of dynamic allocation. -if test $gcc_cv_have_tls = yes ; then - case "${target}" in - - *-*-linux*) - XCFLAGS="${XCFLAGS} -ftls-model=initial-exec" - ;; - esac -fi - # Since we require POSIX threads, assume a POSIX system by default. config_path="posix"