sim: invert sim_state storage

Currently all ports have to declare sim_state themselves in their
sim-main.h and then embed the common sim_state_base & sim_cpu in it.
This dynamic makes it impossible to share common object code among
multiple ports because the core data structure is always different.

Let's invert this relationship: common code declares sim_state, and
if the port actually needs state on a per-instance basis, it can use
the new arch_data field for it.  Most ports don't actually use it,
so they don't need to declare anything at all.

This is the first in a series of changes: it adds a define to select
between the old & new layouts, then converts all the ports that don't
need custom state over to the new layout.

3 files changed, 38 insertions, 11 deletions

diff --git a/sim/common/ChangeLog b/sim/common/ChangeLog
index 1d875bb..f3fcaee 100644
--- a/sim/common/ChangeLog
+++ b/sim/common/ChangeLog
@@ -1,3 +1,13 @@
+2021-05-17  Mike Frysinger  <vapier@gentoo.org>
+
+	* sim-base.h (struct sim_state): Update comment.
+	(struct sim_state): Define.
+	(STATE_ARCH_DATA): Likewise.
+	(sim_state_alloc): New define.
+	(sim_state_alloc_extra): Renamed & add 3rd arg.
+	* sim-utils.c (sim_state_alloc): Likewise.
+	(sim_state_alloc_extra): Set arch data.
+
 2021-05-16  Mike Frysinger  <vapier@gentoo.org>
 
 	* callback.c: Replace config.h include with defs.h.
diff --git a/sim/common/sim-base.h b/sim/common/sim-base.h
index 731fc7f..f38e841 100644
--- a/sim/common/sim-base.h
+++ b/sim/common/sim-base.h
@@ -42,14 +42,7 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
         sim_cpu_base base;
      };
 
-     struct sim_state {
-       sim_cpu *cpu[MAX_NR_PROCESSORS];
-       ... simulator specific members ...
-       sim_state_base base;
-     };
-
-   Note that `base' appears last.  This makes `base.magic' appear last
-   in the entire struct and helps catch miscompilation errors. */
+   If your sim needs to allocate sim-wide state, use STATE_ARCH_DATA.  */
 
 
 #ifndef SIM_BASE_H
@@ -226,8 +219,27 @@ typedef struct {
 #define STATE_MAGIC(sd) ((sd)->base.magic)
 } sim_state_base;
 
+#ifdef SIM_HAVE_COMMON_SIM_STATE
+/* TODO: Merge sim_state & sim_state_base.  */
+struct sim_state {
+  /* All the cpus for this instance.  */
+  sim_cpu *cpu[MAX_NR_PROCESSORS];
+
+  /* All the common state.  */
+  sim_state_base base;
+
+  /* Pointer for sim target to store arbitrary state data.  Normally the
+     target should define a struct and use it here.  */
+  void *arch_data;
+#define STATE_ARCH_DATA(sd) ((sd)->arch_data)
+};
+#endif
+
 /* Functions for allocating/freeing a sim_state.  */
-SIM_DESC sim_state_alloc (SIM_OPEN_KIND kind, host_callback *callback);
+SIM_DESC sim_state_alloc_extra (SIM_OPEN_KIND kind, host_callback *callback,
+				size_t extra_bytes);
+#define sim_state_alloc(kind, callback) sim_state_alloc_extra(kind, callback, 0)
+
 void sim_state_free (SIM_DESC);
 
 #ifdef __cplusplus
diff --git a/sim/common/sim-utils.c b/sim/common/sim-utils.c
index abb87f8..7a94375 100644
--- a/sim/common/sim-utils.c
+++ b/sim/common/sim-utils.c
@@ -48,8 +48,8 @@ zalloc (unsigned long size)
 /* Allocate a sim_state struct.  */
 
 SIM_DESC
-sim_state_alloc (SIM_OPEN_KIND kind,
-		 host_callback *callback)
+sim_state_alloc_extra (SIM_OPEN_KIND kind, host_callback *callback,
+		       size_t extra_bytes)
 {
   SIM_DESC sd = ZALLOC (struct sim_state);
 
@@ -57,6 +57,11 @@ sim_state_alloc (SIM_OPEN_KIND kind,
   STATE_CALLBACK (sd) = callback;
   STATE_OPEN_KIND (sd) = kind;
 
+#ifdef SIM_HAVE_COMMON_SIM_STATE
+  if (extra_bytes)
+    STATE_ARCH_DATA (sd) = zalloc (extra_bytes);
+#endif
+
 #if 0
   {
     int cpu_nr;