commit df79b996a7b21c6ea7847f7927a2e1a294b86c72
author Richard Henderson <rth@twiddle.net> Fri Sep 02 12:23:57 2016 -0700
committer Richard Henderson <rth@twiddle.net> Wed Oct 26 08:29:01 2016 -0700
tree 878779e7214c310b0b0929ca115e286a9f0ba12f
parent 7ebee43ee3e2fcd7b5063058b7ef74bc43216733

tcg: Add CONFIG_ATOMIC64

Allow qemu to build on 32-bit hosts without 64-bit atomic ops.

Even if we only allow 32-bit hosts to multi-thread emulate 32-bit
guests, we still need some way to handle the 32-bit guest using a
64-bit atomic operation.  Do so by dropping back to single-step.

Reviewed-by: Emilio G. Cota <cota@braap.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Richard Henderson <rth@twiddle.net>

configure

diff --git a/configure b/configure
index cc3301f..8e10059 100755
--- a/configure
+++ b/configure
@@ -4544,6 +4544,35 @@
   fi
 fi
 
+#########################################
+# See if 64-bit atomic operations are supported.
+# Note that without __atomic builtins, we can only
+# assume atomic loads/stores max at pointer size.
+
+cat > $TMPC << EOF
+#include <stdint.h>
+int main(void)
+{
+  uint64_t x = 0, y = 0;
+#ifdef __ATOMIC_RELAXED
+  y = __atomic_load_8(&x, 0);
+  __atomic_store_8(&x, y, 0);
+  __atomic_compare_exchange_8(&x, &y, x, 0, 0, 0);
+  __atomic_exchange_8(&x, y, 0);
+  __atomic_fetch_add_8(&x, y, 0);
+#else
+  typedef char is_host64[sizeof(void *) >= sizeof(uint64_t) ? 1 : -1];
+  __sync_lock_test_and_set(&x, y);
+  __sync_val_compare_and_swap(&x, y, 0);
+  __sync_fetch_and_add(&x, y);
+#endif
+  return 0;
+}
+EOF
+if compile_prog "" "" ; then
+  atomic64=yes
+fi
+
 ########################################
 # check if getauxval is available.
 
@@ -5510,6 +5539,10 @@
   echo "CONFIG_ATOMIC128=y" >> $config_host_mak
 fi
 
+if test "$atomic64" = "yes" ; then
+  echo "CONFIG_ATOMIC64=y" >> $config_host_mak
+fi
+
 if test "$getauxval" = "yes" ; then
   echo "CONFIG_GETAUXVAL=y" >> $config_host_mak
 fi