This commit introduces the TCGOpcode for memory barrier instruction.
This opcode takes an argument which is the type of memory barrier
which should be generated.
Signed-off-by: Pranith Kumar <bobby.pr...@gmail.com>
---
tcg/README | 17 +++++++++++++++++
tcg/tcg-op.c | 17 +++++++++++++++++
tcg/tcg-op.h | 2 ++
tcg/tcg-opc.h | 2 ++
tcg/tcg.h | 19 +++++++++++++++++++
5 files changed, 57 insertions(+)
diff --git a/tcg/README b/tcg/README
index ce8beba..1d48aa9 100644
--- a/tcg/README
+++ b/tcg/README
@@ -402,6 +402,23 @@ double-word product T0. The later is returned in two
single-word outputs.
Similar to mulu2, except the two inputs T1 and T2 are signed.
+********* Memory Barrier support
+
+* mb <$arg>
+
+Generate a target memory barrier instruction to ensure memory ordering as being
+enforced by a corresponding guest memory barrier instruction. The ordering
+enforced by the backend may be stricter than the ordering required by the
guest.
+It cannot be weaker. This opcode takes a constant argument which is required to
+generate the appropriate barrier instruction. The backend should take care to
+emit the target barrier instruction only when necessary i.e., for SMP guests
and
+when MTTCG is enabled.
+
+The guest translators should generate this opcode for all guest instructions
+which have ordering side effects.
+
+Please see docs/atomics.txt for more information on memory barriers.
+
********* 64-bit guest on 32-bit host support
The following opcodes are internal to TCG. Thus they are to be implemented by
diff --git a/tcg/tcg-op.c b/tcg/tcg-op.c
index 293b854..149f4a9 100644
--- a/tcg/tcg-op.c
+++ b/tcg/tcg-op.c
@@ -148,6 +148,23 @@ void tcg_gen_op6(TCGContext *ctx, TCGOpcode opc, TCGArg
a1, TCGArg a2,
tcg_emit_op(ctx, opc, pi);
}
+void tcg_gen_mb(TCGArg mb_type)
+{
+ bool emit_barriers = true;
+
+#ifndef CONFIG_USER_ONLY
+ /* TODO: When MTTCG is available for system mode, we will check
+ * the following condition and enable emit_barriers
+ * (qemu_tcg_mttcg_enabled() && smp_cpus > 1)
+ */
+ emit_barriers = false;
+#endif
+
+ if (emit_barriers) {
+ tcg_gen_op1(&tcg_ctx, INDEX_op_mb, mb_type);
+ }
+}
+
/* 32 bit ops */
void tcg_gen_addi_i32(TCGv_i32 ret, TCGv_i32 arg1, int32_t arg2)
diff --git a/tcg/tcg-op.h b/tcg/tcg-op.h
index f217e80..41890cc 100644
--- a/tcg/tcg-op.h
+++ b/tcg/tcg-op.h
@@ -261,6 +261,8 @@ static inline void tcg_gen_br(TCGLabel *l)
tcg_gen_op1(&tcg_ctx, INDEX_op_br, label_arg(l));
}
+void tcg_gen_mb(TCGArg a);
+
/* Helper calls. */
/* 32 bit ops */
diff --git a/tcg/tcg-opc.h b/tcg/tcg-opc.h
index 6d0410c..45528d2 100644
--- a/tcg/tcg-opc.h
+++ b/tcg/tcg-opc.h
@@ -42,6 +42,8 @@ DEF(br, 0, 0, 1, TCG_OPF_BB_END)
# define IMPL64 TCG_OPF_64BIT
#endif
+DEF(mb, 0, 0, 1, 0)
+
DEF(mov_i32, 1, 1, 0, TCG_OPF_NOT_PRESENT)
DEF(movi_i32, 1, 0, 1, TCG_OPF_NOT_PRESENT)
DEF(setcond_i32, 1, 2, 1, 0)
diff --git a/tcg/tcg.h b/tcg/tcg.h
index 66ae0c7..639e30c 100644
--- a/tcg/tcg.h
+++ b/tcg/tcg.h
@@ -478,6 +478,25 @@ static inline intptr_t QEMU_ARTIFICIAL
GET_TCGV_PTR(TCGv_ptr t)
#define TCG_CALL_DUMMY_TCGV MAKE_TCGV_I32(-1)
#define TCG_CALL_DUMMY_ARG ((TCGArg)(-1))
+/* used to indicate the type of accesses on which ordering is to be
+ ensured. Modeled after SPARC barriers */
+typedef enum {
+ TCG_MO_LD_LD = 1,
+ TCG_MO_ST_LD = 2,
+ TCG_MO_LD_ST = 4,
+ TCG_MO_ST_ST = 8,
+ TCG_MO_ALL = 0xF, /* OR of all above */
+} TCGOrder;
+
+/* used to indicate the kind of ordering which is to be ensured by the
+ instruction. These types are derived from x86/aarch64 instructions.
+ It should be noted that these are different from C11 semantics */
+typedef enum {
+ TCG_BAR_LDAQ = 0x10, /* generated for aarch64 load-acquire inst. */
+ TCG_BAR_STRL = 0x20, /* generated for aarch64 store-rel inst. */
+ TCG_BAR_SC = 0x40, /* generated for all other ordering inst. */
+} TCGBar;
+
/* Conditions. Note that these are laid out for easy manipulation by
the functions below:
bit 0 is used for inverting;
--
2.9.0
