On Mon, Sep 18, 2017 at 12:28 PM, Grazvydas Ignotas <nota...@gmail.com> wrote: > On some platforms, gcc generates library calls when __atomic_* functions > are used, but does not link the required library automatically. Detect > this and add the library when needed. > > This change was tested on armel (library was added) and on x86_64 (was > not, as expected). > > Fixes: 8915f0c0 "util: use GCC atomic intrinsics with explicit memory model" > Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=102573 > Signed-off-by: Grazvydas Ignotas <nota...@gmail.com> > --- > configure.ac | 13 +++++++++++++ > src/util/Makefile.am | 3 ++- > 2 files changed, 15 insertions(+), 1 deletion(-) > > diff --git a/configure.ac b/configure.ac > index 605c9b4..b46f29d 100644 > --- a/configure.ac > +++ b/configure.ac > @@ -377,12 +377,25 @@ int main() { > int n; > return __atomic_load_n(&n, __ATOMIC_ACQUIRE); > }]])], GCC_ATOMIC_BUILTINS_SUPPORTED=1) > if test "x$GCC_ATOMIC_BUILTINS_SUPPORTED" = x1; then > DEFINES="$DEFINES -DUSE_GCC_ATOMIC_BUILTINS" > + dnl On some platforms, new-style atomics need a helper library > + AC_MSG_CHECKING(whether -latomic is needed) > + AC_LINK_IFELSE([AC_LANG_SOURCE([[ > + #include <stdint.h> > + uint64_t v; > + int main() { > + return (int)__atomic_load_n(&v, __ATOMIC_ACQUIRE); > + }]])], GCC_ATOMIC_BUILTINS_NEED_LIBATOMIC=no, > GCC_ATOMIC_BUILTINS_NEED_LIBATOMIC=yes) > + AC_MSG_RESULT($GCC_ATOMIC_BUILTINS_NEED_LIBATOMIC) > + if test "x$GCC_ATOMIC_BUILTINS_NEED_LIBATOMIC" = xyes; then > + LIBATOMIC_LIBS="-latomic" > + fi > fi > AM_CONDITIONAL([GCC_ATOMIC_BUILTINS_SUPPORTED], [test > x$GCC_ATOMIC_BUILTINS_SUPPORTED = x1]) > +AC_SUBST([LIBATOMIC_LIBS]) > > dnl Check if host supports 64-bit atomics > dnl note that lack of support usually results in link (not compile) error > AC_MSG_CHECKING(whether __sync_add_and_fetch_8 is supported) > AC_LINK_IFELSE([AC_LANG_SOURCE([[ > diff --git a/src/util/Makefile.am b/src/util/Makefile.am > index 9885bbe..c37afff 100644 > --- a/src/util/Makefile.am > +++ b/src/util/Makefile.am > @@ -46,11 +46,12 @@ libmesautil_la_SOURCES = \ > $(MESA_UTIL_FILES) \ > $(MESA_UTIL_GENERATED_FILES) > > libmesautil_la_LIBADD = \ > $(CLOCK_LIB) \ > - $(ZLIB_LIBS) > + $(ZLIB_LIBS) \ > + $(LIBATOMIC_LIBS)
I can't remember how this works -- will $(LIBATOMIC_LIBS) be added transitively to anything that LDADDs libmesautil? I hope so... Both are Reviewed-by: Matt Turner <matts...@gmail.com> FWIW, libatomic only exists since gcc-4.8, so we'll still have some gaps. _______________________________________________ mesa-dev mailing list mesa-dev@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/mesa-dev
