On Thu, 2019-06-13 at 13:55 +0100, Guillaume Tucker wrote: > On 06/06/2019 08:18, Ser, Simon wrote: > > On Mon, 2019-06-03 at 12:54 +0100, Guillaume Tucker wrote: > > > Add dependency to libatomic in order to be able to use the __atomic_* > > > functions instead of the older __sync_* ones. This is to enable > > > atomic operations on a wider number of architectures including MIPS. > > > > Thanks for your patch! I have a few questions because I don't know well > > how libatomic works. > > Thanks for the review! > > > Do we want to always link against libatomic? For instance LLVM tries to > > compile a program with atomic before falling back to libatomic: > > https://github.com/llvm-mirror/llvm/blob/master/cmake/modules/CheckAtomic.cmake > > > > Should this dependency be mandatory? > > I've had a look around, the short answer is we should make this > dependency optional. I'm sending a v2 of this series which > addresses this issue. > > From what I understand, linking against libatomic is actually > only needed when some atomic operations aren't supported natively > by a CPU architecture. For example, this is the case with 64-bit > atomics on 32-bit MIPS. If the CPU can't do an atomic operation > and there's no libatomic available, then it won't build. So I've > made a test in meson.build to check whether linking against > libatomic is required or not, to drop the dependency when it > isn't. I've verified that the test passes on x86 (i.e. no > dependency) and fails on 32-bit MIPS (i.e. with dependency). Nice! Looks like a good idea to me. > Guillaume > > > > > Signed-off-by: Guillaume Tucker <guillaume.tucker@xxxxxxxxxxxxx> > > > --- > > > meson.build | 1 + > > > tests/meson.build | 2 +- > > > 2 files changed, 2 insertions(+), 1 deletion(-) > > > > > > diff --git a/meson.build b/meson.build > > > index 6268c58d3634..4e5bb323fa49 100644 > > > --- a/meson.build > > > +++ b/meson.build > > > @@ -179,6 +179,7 @@ math = cc.find_library('m') > > > realtime = cc.find_library('rt') > > > dlsym = cc.find_library('dl') > > > zlib = cc.find_library('z') > > > +libatomic = cc.find_library('atomic') > > > > > > if cc.has_header('linux/kd.h') > > > config.set('HAVE_LINUX_KD_H', 1) > > > diff --git a/tests/meson.build b/tests/meson.build > > > index 806766e51667..6877ccd59235 100644 > > > --- a/tests/meson.build > > > +++ b/tests/meson.build > > > @@ -233,7 +233,7 @@ i915_progs = [ > > > 'i915_suspend', > > > ] > > > > > > -test_deps = [ igt_deps ] > > > +test_deps = [ igt_deps, libatomic ] > > > > > > if libdrm_nouveau.found() > > > test_progs += [ _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/intel-gfx
