[PATCH 4/5] tcg: Create tcg_req_mo

[Richard Henderson <richard.henderson@linaro.org>]

Split out the logic to emit a host memory barrier in response to
a guest memory operation.  Do not provide a true default for
TCG_GUEST_DEFAULT_MO because the defined() check will still be
useful for determining if a guest has been updated for MTTCG.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 include/tcg/tcg.h   | 20 ++++++++++++++++++++
 accel/tcg/tcg-all.c |  6 +-----
 tcg/tcg-op.c        |  8 +-------
 3 files changed, 22 insertions(+), 12 deletions(-)

diff --git a/include/tcg/tcg.h b/include/tcg/tcg.h
index 0f0695e90d..395b3b6964 100644
--- a/include/tcg/tcg.h
+++ b/include/tcg/tcg.h
@@ -1245,6 +1245,26 @@ static inline unsigned get_mmuidx(TCGMemOpIdx oi)
     return oi & 15;
 }
 
+/**
+ * tcg_req_mo:
+ * @type: TCGBar
+ *
+ * Filter @type to the barrier that is required for the guest
+ * memory ordering vs the host memory ordering.  A non-zero
+ * result indicates that some barrier is required.
+ *
+ * If TCG_GUEST_DEFAULT_MO is not defined, assume that the
+ * guest requires strict alignment.
+ *
+ * This is a macro so that it's constant even without optimization.
+ */
+#ifdef TCG_GUEST_DEFAULT_MO
+# define tcg_req_mo(type) \
+    ((type) & TCG_GUEST_DEFAULT_MO & ~TCG_TARGET_DEFAULT_MO)
+#else
+# define tcg_req_mo(type) ((type) & ~TCG_TARGET_DEFAULT_MO)
+#endif
+
 /**
  * tcg_qemu_tb_exec:
  * @env: pointer to CPUArchState for the CPU
diff --git a/accel/tcg/tcg-all.c b/accel/tcg/tcg-all.c
index e378c2db73..6ae51e3476 100644
--- a/accel/tcg/tcg-all.c
+++ b/accel/tcg/tcg-all.c
@@ -69,11 +69,7 @@ DECLARE_INSTANCE_CHECKER(TCGState, TCG_STATE,
 
 static bool check_tcg_memory_orders_compatible(void)
 {
-#if defined(TCG_GUEST_DEFAULT_MO) && defined(TCG_TARGET_DEFAULT_MO)
-    return (TCG_GUEST_DEFAULT_MO & ~TCG_TARGET_DEFAULT_MO) == 0;
-#else
-    return false;
-#endif
+    return tcg_req_mo(TCG_MO_ALL) == 0;
 }
 
 static bool default_mttcg_enabled(void)
diff --git a/tcg/tcg-op.c b/tcg/tcg-op.c
index c8501508c2..12fc8a1b17 100644
--- a/tcg/tcg-op.c
+++ b/tcg/tcg-op.c
@@ -2796,13 +2796,7 @@ static void gen_ldst_i64(TCGOpcode opc, TCGv_i64 val, TCGv addr,
 
 static void tcg_gen_req_mo(TCGBar type)
 {
-#ifdef TCG_GUEST_DEFAULT_MO
-    type &= TCG_GUEST_DEFAULT_MO;
-#endif
-    type &= ~TCG_TARGET_DEFAULT_MO;
-    if (type) {
-        tcg_gen_mb(type | TCG_BAR_SC);
-    }
+    tcg_gen_mb(tcg_req_mo(type) | TCG_BAR_SC);
 }
 
 static inline TCGv plugin_prep_mem_callbacks(TCGv vaddr)
-- 
2.25.1