trace: [all] Add "guest_mem_before" event

The event is described in "trace-events". Note that the "MO_AMASK" flag
is not traced, since it does not seem to affect the visible semantics of
instructions.

[s/inline inline/inline/ to fix clang build.
--Stefan]

Signed-off-by: Lluís Vilanova <vilanova@ac.upc.edu>
Reviewed-by: Richard Henderson <rth@twiddle.net>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Message-id: 146549350711.18437.726780393247474362.stgit@fimbulvetr.bsc.es
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

trace/mem.h

@@ -0,0 +1,34 @@
+/*
+ * Helper functions for guest memory tracing
+ *
+ * Copyright (C) 2016 Lluís Vilanova <vilanova@ac.upc.edu>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+
+#ifndef TRACE__MEM_H
+#define TRACE__MEM_H
+
+#include "tcg/tcg.h"
+
+
+/**
+ * trace_mem_get_info:
+ *
+ * Return a value for the 'info' argument in guest memory access traces.
+ */
+static uint8_t trace_mem_get_info(TCGMemOp op, bool store);
+
+/**
+ * trace_mem_build_info:
+ *
+ * Return a value for the 'info' argument in guest memory access traces.
+ */
+static uint8_t trace_mem_build_info(TCGMemOp size, bool sign_extend,
+                                    TCGMemOp endianness, bool store);
+
+
+#include "trace/mem-internal.h"
+
+#endif  /* TRACE__MEM_H */