[Qemu-devel] [RFC PATCH 2/3] tcg: Add support for fence generation in x86 backend

[Pranith Kumar <bobby.prani@gmail.com>]

Signed-off-by: Pranith Kumar <bobby.prani@gmail.com>
---
 tcg/i386/tcg-target.h     | 1 +
 tcg/i386/tcg-target.inc.c | 9 +++++++++
 tcg/tcg-opc.h             | 2 +-
 tcg/tcg.c                 | 1 +
 4 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/tcg/i386/tcg-target.h b/tcg/i386/tcg-target.h
index 92be341..93ea42e 100644
--- a/tcg/i386/tcg-target.h
+++ b/tcg/i386/tcg-target.h
@@ -100,6 +100,7 @@ extern bool have_bmi1;
 #define TCG_TARGET_HAS_muls2_i32        1
 #define TCG_TARGET_HAS_muluh_i32        0
 #define TCG_TARGET_HAS_mulsh_i32        0
+#define TCG_TARGET_HAS_fence            1
 
 #if TCG_TARGET_REG_BITS == 64
 #define TCG_TARGET_HAS_extrl_i64_i32    0
diff --git a/tcg/i386/tcg-target.inc.c b/tcg/i386/tcg-target.inc.c
index 238fa10..cf49272 100644
--- a/tcg/i386/tcg-target.inc.c
+++ b/tcg/i386/tcg-target.inc.c
@@ -347,6 +347,7 @@ static inline int tcg_target_const_match(tcg_target_long val, TCGType type,
 #define OPC_SHRX        (0xf7 | P_EXT38 | P_SIMDF2)
 #define OPC_TESTL	(0x85)
 #define OPC_XCHG_ax_r32	(0x90)
+#define OPC_MFENCE      (0xAE | P_EXT)
 
 #define OPC_GRP3_Ev	(0xf7)
 #define OPC_GRP5	(0xff)
@@ -686,6 +687,14 @@ static inline void tcg_out_pushi(TCGContext *s, tcg_target_long val)
     }
 }
 
+static inline void tcg_out_fence(TCGContext *s)
+{
+    /* TODO: Figure out an appropriate place for the encoding */
+    tcg_out8(s, 0x0F);
+    tcg_out8(s, 0xAE);
+    tcg_out8(s, 0xF0);
+}
+
 static inline void tcg_out_push(TCGContext *s, int reg)
 {
     tcg_out_opc(s, OPC_PUSH_r32 + LOWREGMASK(reg), 0, reg, 0);
diff --git a/tcg/tcg-opc.h b/tcg/tcg-opc.h
index 4696cf1..b772d90 100644
--- a/tcg/tcg-opc.h
+++ b/tcg/tcg-opc.h
@@ -42,7 +42,7 @@ DEF(br, 0, 0, 1, TCG_OPF_BB_END)
 # define IMPL64  TCG_OPF_64BIT
 #endif
 
-DEF(fence, 0, 0, 0, 0)
+DEF(fence, 0, 0, 0, TCG_OPF_SIDE_EFFECTS)
 
 DEF(mov_i32, 1, 1, 0, TCG_OPF_NOT_PRESENT)
 DEF(movi_i32, 1, 0, 1, TCG_OPF_NOT_PRESENT)
diff --git a/tcg/tcg.c b/tcg/tcg.c
index b5a22ba..461a33e 100644
--- a/tcg/tcg.c
+++ b/tcg/tcg.c
@@ -2444,6 +2444,7 @@ int tcg_gen_code(TCGContext *s, TranslationBlock *tb)
                                dead_args, sync_args);
             break;
         case INDEX_op_fence:
+            tcg_out_fence(s);
             break;
         default:
             /* Sanity check that we've not introduced any unhandled opcodes. */
-- 
2.8.3