tcg: Add atomic128 helpers
Force the use of cmpxchg16b on x86_64.
Wikipedia suggests that only very old AMD64 (circa 2004) did not have
this instruction. Further, it's required by Windows 8 so no new cpus
will ever omit it.
If we truely care about these, then we could check this at startup time
and then avoid executing paths that use it.
Reviewed-by: Emilio G. Cota <cota@braap.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Richard Henderson <rth@twiddle.net>
diff --git a/configure b/configure
index d3dafcb..cc3301f 100755
--- a/configure
+++ b/configure
@@ -1216,7 +1216,10 @@
cc_i386='$(CC) -m32'
;;
x86_64)
- CPU_CFLAGS="-m64"
+ # ??? Only extremely old AMD cpus do not have cmpxchg16b.
+ # If we truly care, we should simply detect this case at
+ # runtime and generate the fallback to serial emulation.
+ CPU_CFLAGS="-m64 -mcx16"
LDFLAGS="-m64 $LDFLAGS"
cc_i386='$(CC) -m32'
;;
@@ -4521,6 +4524,26 @@
int128=yes
fi
+#########################################
+# See if 128-bit atomic operations are supported.
+
+atomic128=no
+if test "$int128" = "yes"; then
+ cat > $TMPC << EOF
+int main(void)
+{
+ unsigned __int128 x = 0, y = 0;
+ y = __atomic_load_16(&x, 0);
+ __atomic_store_16(&x, y, 0);
+ __atomic_compare_exchange_16(&x, &y, x, 0, 0, 0);
+ return 0;
+}
+EOF
+ if compile_prog "" "" ; then
+ atomic128=yes
+ fi
+fi
+
########################################
# check if getauxval is available.
@@ -5483,6 +5506,10 @@
echo "CONFIG_INT128=y" >> $config_host_mak
fi
+if test "$atomic128" = "yes" ; then
+ echo "CONFIG_ATOMIC128=y" >> $config_host_mak
+fi
+
if test "$getauxval" = "yes" ; then
echo "CONFIG_GETAUXVAL=y" >> $config_host_mak
fi
