On Mon, Sep 18, 2017 at 11:30 PM, Matt Turner <matts...@gmail.com> wrote: > 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...
I'm not sure either, I've simply tried it and it seemed to work. Maybe Emil can comment if it's the right way... > Oh, also, these should get a Cc: mesa-stable tag. It has been said (and documented in docs/submittingpatches.html) that Fixes: tag is enough for stable, and 2/2 it's strictly necessary I think. _______________________________________________ mesa-dev mailing list mesa-dev@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/mesa-dev
