target/sparc: Set TCG_GUEST_DEFAULT_MO

Always use TSO, per the Oracle 2015 manual.
This is slightly less restrictive than the TCG_MO_ALL default,
and happens to match the i386 model, which will eliminate a few
extra barriers on that host.

Tested-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Acked-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

target/sparc/cpu.h

@@ -6,6 +6,29 @@
 #include "exec/cpu-defs.h"
 #include "qemu/cpu-float.h"
 
+/*
+ * From Oracle SPARC Architecture 2015:
+ *
+ *   Compatibility notes: The PSO memory model described in SPARC V8 and
+ *   SPARC V9 compatibility architecture specifications was never implemented
+ *   in a SPARC V9 implementation and is not included in the Oracle SPARC
+ *   Architecture specification.
+ *
+ *   The RMO memory model described in the SPARC V9 specification was
+ *   implemented in some non-Sun SPARC V9 implementations, but is not
+ *   directly supported in Oracle SPARC Architecture 2015 implementations.
+ *
+ * Therefore always use TSO in QEMU.
+ *
+ * D.5 Specification of Partial Store Order (PSO)
+ *   ... [loads] are followed by an implied MEMBAR #LoadLoad | #LoadStore.
+ *
+ * D.6 Specification of Total Store Order (TSO)
+ *   ... PSO with the additional requirement that all [stores] are followed
+ *   by an implied MEMBAR #StoreStore.
+ */
+#define TCG_GUEST_DEFAULT_MO  (TCG_MO_LD_LD | TCG_MO_LD_ST | TCG_MO_ST_ST)
+
 #if !defined(TARGET_SPARC64)
 #define TARGET_DPREGS 16
 #else