Check for libatomic dependency for atomic operationswip/T19119

Some platforms (e.g. RISC-V) require linking against libatomic for some
(e.g. sub-word-sized) atomic operations.

Fixes #19119.

2 files changed, 26 insertions, 0 deletions

diff --git a/configure.ac b/configure.ac
index d69ff312b8..67c645a3d0 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1211,6 +1211,27 @@ AC_CHECK_FUNC(pthread_create,
 AC_DEFINE_UNQUOTED([NEED_PTHREAD_LIB], [$need_lpthread],
     [Define 1 if we need to link code using pthreads with -lpthread])
 
+AC_MSG_CHECKING(whether -latomic is needed for sub-word-sized atomic operations)
+AC_CHECK_FUNC(atomic_fetch_or,
+    [
+        AC_MSG_RESULT(no)
+        AC_SUBST([CabalNeedAtomic],[False])
+        need_latomic=0
+    ],
+    [
+        AC_CHECK_LIB(atomic, atomic_fetch_or,
+            [
+                AC_MSG_RESULT(yes)
+                AC_SUBST([CabalNeedAtomic],[True])
+                need_latomic=1
+            ],
+            [
+                AC_SUBST([CabalNeedAtomic],[False])
+                AC_MSG_ERROR([sub-word-sized atomic operations not available.])
+                need_latomic=0
+            ])
+    ])
+
 dnl ** pthread_setname_np is a recent addition to glibc, and OS X has
 dnl    a different single-argument version.
 AC_CHECK_LIB(pthread, pthread_setname_np)
diff --git a/rts/rts.cabal.in b/rts/rts.cabal.in
index ed727111ca..b41e3538b0 100644
--- a/rts/rts.cabal.in
+++ b/rts/rts.cabal.in
@@ -18,6 +18,8 @@ flag libbfd
   default: @CabalHaveLibbfd@
 flag mingwex
   default: @CabalMingwex@
+flag need-atomic
+  default: @CabalNeedLibatomic@
 flag libdw
   default: @CabalHaveLibdw@
 flag libnuma
@@ -120,6 +122,9 @@ library
     if flag(need-pthread)
        -- for pthread_getthreadid_np, pthread_create, ...
        extra-libraries: pthread
+    if flag(need-libatomic)
+       -- for sub-word-sized atomic operations (#19119)
+       extra-libraries: atomic
     if flag(libbfd)
        -- for debugging
        extra-libraries: bfd iberty