Class readonly_detached_regcache

This patch adds a new class (type) for readonly regcache, which is
created via regcache::save.  readonly_detached_regcache inherits
readable_regcache.

gdb:

2018-02-21  Yao Qi  <yao.qi@linaro.org>

	* dummy-frame.c (dummy_frame_cache) <prev_regcache>: Use
	readonly_detached_regcache.
	(dummy_frame_prev_register): Use regcache->cooked_read.
	* frame.c (frame_save_as_regcache): Change return type.
	(frame_pop): Update.
	* frame.h (frame_save_as_regcache): Update declaration.
	* inferior.h (get_infcall_suspend_state_regcache): Update
	declaration.
	* infrun.c (infcall_suspend_state) <registers>: use
	readonly_detached_regcache.
	(save_infcall_suspend_state): Don't use regcache_dup.
	(get_infcall_suspend_state_regcache): Change return type.
	* linux-fork.c (struct fork_info) <savedregs>: Change to
	readonly_detached_regcache.
	<pc>: New field.
	(fork_save_infrun_state): Don't use regcache_dup.
	(info_checkpoints_command): Adjust.
	* mi/mi-main.c (register_changed_p): Update declaration.
	(mi_cmd_data_list_changed_registers): Use
	readonly_detached_regcache.
	(register_changed_p): Change parameter type to
	readonly_detached_regcache.
	* ppc-linux-tdep.c (ppu2spu_cache) <regcache>: Use
	readonly_detached_regcache.
	(ppu2spu_sniffer): Construct a new readonly_detached_regcache.
	* regcache.c (readonly_detached_regcache::readonly_detached_regcache):
	New.
	(regcache::save): Move it to reg_buffer.
	(regcache::restore): Change parameter type.
	(regcache_dup): Remove.
	* regcache.h (reg_buffer) <save>: New method.
	(readonly_detached_regcache): New class.
	* spu-tdep.c (spu2ppu_cache) <regcache>: Use
	readonly_detached_regcache.
	(spu2ppu_sniffer): Construct a new readonly_detached_regcache.

12 files changed, 118 insertions, 64 deletions

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index a7da794..bb59b31 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,5 +1,43 @@
 2018-02-21  Yao Qi  <yao.qi@linaro.org>
 
+	* dummy-frame.c (dummy_frame_cache) <prev_regcache>: Use
+	readonly_detached_regcache.
+	(dummy_frame_prev_register): Use regcache->cooked_read.
+	* frame.c (frame_save_as_regcache): Change return type.
+	(frame_pop): Update.
+	* frame.h (frame_save_as_regcache): Update declaration.
+	* inferior.h (get_infcall_suspend_state_regcache): Update
+	declaration.
+	* infrun.c (infcall_suspend_state) <registers>: use
+	readonly_detached_regcache.
+	(save_infcall_suspend_state): Don't use regcache_dup.
+	(get_infcall_suspend_state_regcache): Change return type.
+	* linux-fork.c (struct fork_info) <savedregs>: Change to
+	readonly_detached_regcache.
+	<pc>: New field.
+	(fork_save_infrun_state): Don't use regcache_dup.
+	(info_checkpoints_command): Adjust.
+	* mi/mi-main.c (register_changed_p): Update declaration.
+	(mi_cmd_data_list_changed_registers): Use
+	readonly_detached_regcache.
+	(register_changed_p): Change parameter type to
+	readonly_detached_regcache.
+	* ppc-linux-tdep.c (ppu2spu_cache) <regcache>: Use
+	readonly_detached_regcache.
+	(ppu2spu_sniffer): Construct a new readonly_detached_regcache.
+	* regcache.c (readonly_detached_regcache::readonly_detached_regcache):
+	New.
+	(regcache::save): Move it to reg_buffer.
+	(regcache::restore): Change parameter type.
+	(regcache_dup): Remove.
+	* regcache.h (reg_buffer) <save>: New method.
+	(readonly_detached_regcache): New class.
+	* spu-tdep.c (spu2ppu_cache) <regcache>: Use
+	readonly_detached_regcache.
+	(spu2ppu_sniffer): Construct a new readonly_detached_regcache.
+
+2018-02-21  Yao Qi  <yao.qi@linaro.org>
+
 	* frame.c (frame_save_as_regcache): Use regcache method save.
 	(frame_pop): Use regcache method restore.
 	* infrun.c (restore_infcall_suspend_state): Likewise.
diff --git a/gdb/dummy-frame.c b/gdb/dummy-frame.c
index db8ba1b..a67033e 100644
--- a/gdb/dummy-frame.c
+++ b/gdb/dummy-frame.c
@@ -282,7 +282,7 @@ cleanup_dummy_frames (struct target_ops *target, int from_tty)
 struct dummy_frame_cache
 {
   struct frame_id this_id;
-  struct regcache *prev_regcache;
+  readonly_detached_regcache *prev_regcache;
 };
 
 static int
@@ -352,8 +352,8 @@ dummy_frame_prev_register (struct frame_info *this_frame,
   /* Use the regcache_cooked_read() method so that it, on the fly,
      constructs either a raw or pseudo register from the raw
      register cache.  */
-  regcache_cooked_read (cache->prev_regcache, regnum,
-			value_contents_writeable (reg_val));
+  cache->prev_regcache->cooked_read (regnum,
+				     value_contents_writeable (reg_val));
   return reg_val;
 }
 
diff --git a/gdb/frame.c b/gdb/frame.c
index 773fd04..0b04a4e 100644
--- a/gdb/frame.c
+++ b/gdb/frame.c
@@ -1017,13 +1017,13 @@ do_frame_register_read (void *src, int regnum, gdb_byte *buf)
     return REG_VALID;
 }
 
-std::unique_ptr<struct regcache>
+std::unique_ptr<readonly_detached_regcache>
 frame_save_as_regcache (struct frame_info *this_frame)
 {
-  std::unique_ptr<struct regcache> regcache
-    (new struct regcache (get_frame_arch (this_frame)));
+  std::unique_ptr<readonly_detached_regcache> regcache
+    (new readonly_detached_regcache (get_frame_arch (this_frame),
+				     do_frame_register_read, this_frame));
 
-  regcache->save (do_frame_register_read, this_frame);
   return regcache;
 }
 
@@ -1057,7 +1057,7 @@ frame_pop (struct frame_info *this_frame)
      Save them in a scratch buffer so that there isn't a race between
      trying to extract the old values from the current regcache while
      at the same time writing new values into that same cache.  */
-  std::unique_ptr<struct regcache> scratch
+  std::unique_ptr<readonly_detached_regcache> scratch
     = frame_save_as_regcache (prev_frame);
 
   /* FIXME: cagney/2003-03-16: It should be possible to tell the
diff --git a/gdb/frame.h b/gdb/frame.h
index 8293a49..d5800b7 100644
--- a/gdb/frame.h
+++ b/gdb/frame.h
@@ -680,8 +680,9 @@ extern void *frame_obstack_zalloc (unsigned long size);
 #define FRAME_OBSTACK_CALLOC(NUMBER,TYPE) \
   ((TYPE *) frame_obstack_zalloc ((NUMBER) * sizeof (TYPE)))
 
+class readonly_detached_regcache;
 /* Create a regcache, and copy the frame's registers into it.  */
-std::unique_ptr<struct regcache> frame_save_as_regcache
+std::unique_ptr<readonly_detached_regcache> frame_save_as_regcache
     (struct frame_info *this_frame);
 
 extern const struct block *get_frame_block (struct frame_info *,
diff --git a/gdb/inferior.h b/gdb/inferior.h
index 22008a0..391a5fd 100644
--- a/gdb/inferior.h
+++ b/gdb/inferior.h
@@ -70,7 +70,7 @@ extern struct cleanup *make_cleanup_restore_infcall_control_state
 extern void discard_infcall_suspend_state (struct infcall_suspend_state *);
 extern void discard_infcall_control_state (struct infcall_control_state *);
 
-extern struct regcache *
+extern readonly_detached_regcache *
   get_infcall_suspend_state_regcache (struct infcall_suspend_state *);
 
 extern void set_sigint_trap (void);
diff --git a/gdb/infrun.c b/gdb/infrun.c
index b4e6c6b..c663908 100644
--- a/gdb/infrun.c
+++ b/gdb/infrun.c
@@ -8805,7 +8805,7 @@ struct infcall_suspend_state
 
   /* Other fields:  */
   CORE_ADDR stop_pc;
-  struct regcache *registers;
+  readonly_detached_regcache *registers;
 
   /* Format of SIGINFO_DATA or NULL if it is not present.  */
   struct gdbarch *siginfo_gdbarch;
@@ -8861,7 +8861,7 @@ save_infcall_suspend_state (void)
 
   inf_state->stop_pc = stop_pc;
 
-  inf_state->registers = regcache_dup (regcache);
+  inf_state->registers = new readonly_detached_regcache (*regcache);
 
   return inf_state;
 }
@@ -8918,7 +8918,7 @@ discard_infcall_suspend_state (struct infcall_suspend_state *inf_state)
   xfree (inf_state);
 }
 
-struct regcache *
+readonly_detached_regcache *
 get_infcall_suspend_state_regcache (struct infcall_suspend_state *inf_state)
 {
   return inf_state->registers;
diff --git a/gdb/linux-fork.c b/gdb/linux-fork.c
index df7ea4e..9ffab1f 100644
--- a/gdb/linux-fork.c
+++ b/gdb/linux-fork.c
@@ -45,8 +45,9 @@ struct fork_info
   ptid_t ptid;
   ptid_t parent_ptid;
   int num;			/* Convenient handle (GDB fork id).  */
-  struct regcache *savedregs;	/* Convenient for info fork, saves
+  readonly_detached_regcache *savedregs;	/* Convenient for info fork, saves
 				   having to actually switch contexts.  */
+  CORE_ADDR pc;
   int clobber_regs;		/* True if we should restore saved regs.  */
   off_t *filepos;		/* Set of open file descriptors' offsets.  */
   int maxfd;
@@ -294,7 +295,8 @@ fork_save_infrun_state (struct fork_info *fp, int clobber_regs)
   if (fp->savedregs)
     delete fp->savedregs;
 
-  fp->savedregs = regcache_dup (get_current_regcache ());
+  fp->savedregs = new readonly_detached_regcache (*get_current_regcache ());
+  fp->pc = regcache_read_pc (get_current_regcache ());
   fp->clobber_regs = clobber_regs;
 
   if (clobber_regs)
@@ -590,15 +592,11 @@ info_checkpoints_command (const char *arg, int from_tty)
 
       printed = fp;
       if (ptid_equal (fp->ptid, inferior_ptid))
-	{
-	  printf_filtered ("* ");
-	  pc = regcache_read_pc (get_current_regcache ());
-	}
+	printf_filtered ("* ");
       else
-	{
-	  printf_filtered ("  ");
-	  pc = regcache_read_pc (fp->savedregs);
-	}
+	printf_filtered ("  ");
+
+      pc = fp->pc;
       printf_filtered ("%d %s", fp->num, target_pid_to_str (fp->ptid));
       if (fp->num == 0)
 	printf_filtered (_(" (main process)"));
diff --git a/gdb/mi/mi-main.c b/gdb/mi/mi-main.c
index 51d33c9..1716a7f 100644
--- a/gdb/mi/mi-main.c
+++ b/gdb/mi/mi-main.c
@@ -96,8 +96,8 @@ static void mi_execute_cli_command (const char *cmd, int args_p,
 				    const char *args);
 static void mi_execute_async_cli_command (const char *cli_command,
 					  char **argv, int argc);
-static bool register_changed_p (int regnum, regcache *,
-				regcache *);
+static bool register_changed_p (int regnum, readonly_detached_regcache *,
+			       readonly_detached_regcache *);
 static void output_register (struct frame_info *, int regnum, int format,
 			     int skip_unavailable);
 
@@ -931,9 +931,9 @@ mi_cmd_data_list_register_names (const char *command, char **argv, int argc)
 void
 mi_cmd_data_list_changed_registers (const char *command, char **argv, int argc)
 {
-  static std::unique_ptr<struct regcache> this_regs;
+  static std::unique_ptr<readonly_detached_regcache> this_regs;
   struct ui_out *uiout = current_uiout;
-  std::unique_ptr<struct regcache> prev_regs;
+  std::unique_ptr<readonly_detached_regcache> prev_regs;
   struct gdbarch *gdbarch;
   int regnum, numregs;
   int i;
@@ -995,8 +995,8 @@ mi_cmd_data_list_changed_registers (const char *command, char **argv, int argc)
 }
 
 static bool
-register_changed_p (int regnum, struct regcache *prev_regs,
-		    struct regcache *this_regs)
+register_changed_p (int regnum, readonly_detached_regcache *prev_regs,
+		    readonly_detached_regcache *this_regs)
 {
   struct gdbarch *gdbarch = this_regs->arch ();
   struct value *prev_value, *this_value;
diff --git a/gdb/ppc-linux-tdep.c b/gdb/ppc-linux-tdep.c
index 13a50d6..d6a98fc 100644
--- a/gdb/ppc-linux-tdep.c
+++ b/gdb/ppc-linux-tdep.c
@@ -1262,7 +1262,7 @@ ppc_linux_spe_context (int wordsize, enum bfd_endian byte_order,
 struct ppu2spu_cache
 {
   struct frame_id frame_id;
-  struct regcache *regcache;
+  readonly_detached_regcache *regcache;
 };
 
 static struct gdbarch *
@@ -1369,10 +1369,10 @@ ppu2spu_sniffer (const struct frame_unwind *self,
 	{
 	  struct ppu2spu_cache *cache
 	    = FRAME_OBSTACK_CALLOC (1, struct ppu2spu_cache);
-	  std::unique_ptr<struct regcache> regcache
-	    (new struct regcache (data.gdbarch));
-
-	  regcache->save (ppu2spu_unwind_register, &data);
+	  std::unique_ptr<readonly_detached_regcache> regcache
+	    (new readonly_detached_regcache (data.gdbarch,
+					     ppu2spu_unwind_register,
+					     &data));
 
 	  cache->frame_id = frame_id_build (base, func);
 	  cache->regcache = regcache.release ();
diff --git a/gdb/regcache.c b/gdb/regcache.c
index 0df6a88..ebe3c7b 100644
--- a/gdb/regcache.c
+++ b/gdb/regcache.c
@@ -226,6 +226,11 @@ regcache::regcache (readonly_t, const regcache &src)
   save (do_cooked_read, (void *) &src);
 }
 
+readonly_detached_regcache::readonly_detached_regcache (const regcache &src)
+  : readonly_detached_regcache (src.arch (), do_cooked_read, (void *) &src)
+{
+}
+
 gdbarch *
 reg_buffer::arch () const
 {
@@ -282,16 +287,14 @@ reg_buffer::register_buffer (int regnum) const
 }
 
 void
-regcache::save (regcache_cooked_read_ftype *cooked_read,
-		void *src)
+reg_buffer::save (regcache_cooked_read_ftype *cooked_read,
+		  void *src)
 {
   struct gdbarch *gdbarch = m_descr->gdbarch;
   int regnum;
 
-  /* The DST should be `read-only', if it wasn't then the save would
-     end up trying to write the register values back out to the
-     target.  */
-  gdb_assert (m_readonly_p);
+  /* It should have pseudo registers.  */
+  gdb_assert (m_has_pseudo);
   /* Clear the dest.  */
   memset (m_registers, 0, m_descr->sizeof_cooked_registers);
   memset (m_register_status, 0, m_descr->nr_cooked_registers);
@@ -317,16 +320,14 @@ regcache::save (regcache_cooked_read_ftype *cooked_read,
 }
 
 void
-regcache::restore (struct regcache *src)
+regcache::restore (readonly_detached_regcache *src)
 {
   struct gdbarch *gdbarch = m_descr->gdbarch;
   int regnum;
 
   gdb_assert (src != NULL);
-  /* The dst had better not be read-only.  If it is, the `restore'
-     doesn't make much sense.  */
   gdb_assert (!m_readonly_p);
-  gdb_assert (src->m_readonly_p);
+  gdb_assert (src->m_has_pseudo);
 
   gdb_assert (gdbarch == src->arch ());
 
@@ -344,12 +345,6 @@ regcache::restore (struct regcache *src)
     }
 }
 
-struct regcache *
-regcache_dup (struct regcache *src)
-{
-  return new regcache (regcache::readonly, *src);
-}
-
 enum register_status
 regcache_register_status (const struct regcache *regcache, int regnum)
 {
diff --git a/gdb/regcache.h b/gdb/regcache.h
index a4ca2ec..4ad0060 100644
--- a/gdb/regcache.h
+++ b/gdb/regcache.h
@@ -243,6 +243,11 @@ protected:
 
   gdb_byte *register_buffer (int regnum) const;
 
+  /* Save a register cache.  The set of registers saved into the
+     regcache determined by the save_reggroup.  COOKED_READ returns
+     zero iff the register's value can't be returned.  */
+  void save (regcache_cooked_read_ftype *cooked_read, void *src);
+
   struct regcache_descr *m_descr;
 
   bool m_has_pseudo;
@@ -250,6 +255,8 @@ protected:
   gdb_byte *m_registers;
   /* Register cache status.  */
   signed char *m_register_status;
+
+  friend class regcache;
 };
 
 /* An abstract class which only has methods doing read.  */
@@ -284,6 +291,8 @@ protected:
 				  bool is_raw);
 };
 
+class readonly_detached_regcache;
+
 /* The register cache for storing raw register values.  */
 
 class regcache : public readable_regcache
@@ -307,15 +316,11 @@ public:
     return m_aspace;
   }
 
-/* Save/restore 'this' regcache.  The set of registers saved /
-   restored into the regcache determined by the save_reggroup /
-   restore_reggroup respectively.  COOKED_READ returns zero iff the
-   register's value can't be returned.  */
-  void save (regcache_cooked_read_ftype *cooked_read, void *src);
-
-  /* Writes to regcache will go through to the target.  SRC is a
+  /* Restore 'this' regcache.  The set of registers restored into
+     the regcache determined by the restore_reggroup.
+     Writes to regcache will go through to the target.  SRC is a
      read-only register cache.  */
-  void restore (struct regcache *src);
+  void restore (readonly_detached_regcache *src);
 
   void cooked_write (int regnum, const gdb_byte *buf);
 
@@ -413,9 +418,26 @@ private:
   registers_changed_ptid (ptid_t ptid);
 };
 
-/* Duplicate the contents of a register cache to a read-only register
-   cache.  The operation is pass-through.  */
-extern struct regcache *regcache_dup (struct regcache *regcache);
+class readonly_detached_regcache : public readable_regcache
+{
+public:
+  readonly_detached_regcache (const regcache &src);
+
+  /* Create a readonly regcache by getting contents from COOKED_READ.  */
+
+  readonly_detached_regcache (gdbarch *gdbarch,
+			      regcache_cooked_read_ftype *cooked_read,
+			      void *src)
+    : readable_regcache (gdbarch, true)
+  {
+    save (cooked_read, src);
+  }
+
+  DISABLE_COPY_AND_ASSIGN (readonly_detached_regcache);
+
+  void raw_update (int regnum) override
+  {}
+};
 
 extern void registers_changed (void);
 extern void registers_changed_ptid (ptid_t);
diff --git a/gdb/spu-tdep.c b/gdb/spu-tdep.c
index da7b937..a632c06 100644
--- a/gdb/spu-tdep.c
+++ b/gdb/spu-tdep.c
@@ -1202,7 +1202,7 @@ spu_write_pc (struct regcache *regcache, CORE_ADDR pc)
 struct spu2ppu_cache
 {
   struct frame_id frame_id;
-  struct regcache *regcache;
+  readonly_detached_regcache *regcache;
 };
 
 static struct gdbarch *
@@ -1229,7 +1229,7 @@ spu2ppu_prev_register (struct frame_info *this_frame,
   gdb_byte *buf;
 
   buf = (gdb_byte *) alloca (register_size (gdbarch, regnum));
-  regcache_cooked_read (cache->regcache, regnum, buf);
+  cache->regcache->cooked_read (regnum, buf);
   return frame_unwind_got_bytes (this_frame, regnum, buf);
 }
 
@@ -1274,7 +1274,7 @@ spu2ppu_sniffer (const struct frame_unwind *self,
 	{
 	  struct regcache *regcache;
 	  regcache = get_thread_arch_regcache (inferior_ptid, target_gdbarch ());
-	  cache->regcache = regcache_dup (regcache);
+	  cache->regcache = new readonly_detached_regcache (*regcache);
 	  *this_prologue_cache = cache;
 	  return 1;
 	}