gdb: use reg_buffer_common throughout gdbsupport/common-regcache.h

Right now, gdbsupport/common-regcache.h contains two abstractons for a
regcache.  An opaque type `regcache` (gdb and gdbserver both have their
own regcache that is the concrete version of this) and an abstract base
class `reg_buffer_common`, that is the base of regcaches on both sides.
These abstractions allow code to be written for both gdb and gdbserver,
for instance in the gdb/arch sub-directory.

However, having two
different abstractions is impractical.  If some common code has a regcache,
and wants to use an operation defined on reg_buffer_common, it can't.
It would be better to have just one.  Change all instances of `regcache
*` in gdbsupport/common-regcache.h to be `reg_buffer_common *`, then fix
fallouts.

Implementations in gdb and gdbserver now need to down-cast (using
gdb::checked_static_cast) from reg_buffer_common to their concrete
regcache type.  Some of them could be avoided by changing free functions
(like regcache_register_size) to be virtual methods on
reg_buffer_common.  I tried it, it seems to work, but I did not include
it in this series to avoid adding unnecessary changes.

Change-Id: Ia5503adb6b5509a0f4604bd2a68b4642cc5283fd
Reviewed-by: John Baldwin <jhb@FreeBSD.org>

4 files changed, 10 insertions, 9 deletions

diff --git a/gdb/arch/arm-get-next-pcs.c b/gdb/arch/arm-get-next-pcs.c
index dcbb5a5..528753a 100644
--- a/gdb/arch/arm-get-next-pcs.c
+++ b/gdb/arch/arm-get-next-pcs.c
@@ -32,7 +32,7 @@ arm_get_next_pcs_ctor (struct arm_get_next_pcs *self,
 		       int byte_order,
 		       int byte_order_for_code,
 		       int has_thumb2_breakpoint,
-		       struct regcache *regcache)
+		       reg_buffer_common *regcache)
 {
   self->ops = ops;
   self->byte_order = byte_order;
@@ -268,12 +268,12 @@ thumb_get_next_pcs_raw (struct arm_get_next_pcs *self)
 {
   int byte_order = self->byte_order;
   int byte_order_for_code = self->byte_order_for_code;
+  reg_buffer_common *regcache = self->regcache;
   CORE_ADDR pc = regcache_read_pc (self->regcache);
   unsigned long pc_val = ((unsigned long) pc) + 4;	/* PC after prefetch */
   unsigned short inst1;
   CORE_ADDR nextpc = pc + 2;		/* Default is next instruction.  */
   ULONGEST status, itstate;
-  struct regcache *regcache = self->regcache;
   std::vector<CORE_ADDR> next_pcs;
 
   nextpc = MAKE_THUMB_ADDR (nextpc);
@@ -653,8 +653,8 @@ arm_get_next_pcs_raw (struct arm_get_next_pcs *self)
   unsigned long this_instr = 0;
   unsigned long status;
   CORE_ADDR nextpc;
-  struct regcache *regcache = self->regcache;
-  CORE_ADDR pc = regcache_read_pc (self->regcache);
+  reg_buffer_common *regcache = self->regcache;
+  CORE_ADDR pc = regcache_read_pc (regcache);
   std::vector<CORE_ADDR> next_pcs;
 
   pc_val = (unsigned long) pc;
diff --git a/gdb/arch/arm-get-next-pcs.h b/gdb/arch/arm-get-next-pcs.h
index e6bb8d8..ec347f0 100644
--- a/gdb/arch/arm-get-next-pcs.h
+++ b/gdb/arch/arm-get-next-pcs.h
@@ -24,6 +24,7 @@
 
 /* Forward declaration.  */
 struct arm_get_next_pcs;
+struct reg_buffer_common;
 
 /* get_next_pcs operations.  */
 struct arm_get_next_pcs_ops
@@ -50,7 +51,7 @@ struct arm_get_next_pcs
      not.  */
   int has_thumb2_breakpoint;
   /* Registry cache.  */
-  struct regcache *regcache;
+  reg_buffer_common *regcache;
 };
 
 /* Initialize arm_get_next_pcs.  */
@@ -59,7 +60,7 @@ void arm_get_next_pcs_ctor (struct arm_get_next_pcs *self,
 			    int byte_order,
 			    int byte_order_for_code,
 			    int has_thumb2_breakpoint,
-			    struct regcache *regcache);
+			    reg_buffer_common *regcache);
 
 /* Find the next possible PCs after the current instruction executes.  */
 std::vector<CORE_ADDR> arm_get_next_pcs (struct arm_get_next_pcs *self);
diff --git a/gdb/arch/arm.c b/gdb/arch/arm.c
index 6fc4c0e..5c41b26 100644
--- a/gdb/arch/arm.c
+++ b/gdb/arch/arm.c
@@ -322,7 +322,7 @@ thumb2_instruction_changes_pc (unsigned short inst1, unsigned short inst2)
 /* See arm.h.  */
 
 unsigned long
-shifted_reg_val (struct regcache *regcache, unsigned long inst,
+shifted_reg_val (reg_buffer_common *regcache, unsigned long inst,
 		 int carry, unsigned long pc_val, unsigned long status_reg)
 {
   unsigned long res, shift;
diff --git a/gdb/arch/arm.h b/gdb/arch/arm.h
index c64a156..b6c3161 100644
--- a/gdb/arch/arm.h
+++ b/gdb/arch/arm.h
@@ -188,7 +188,7 @@ enum system_register_address : CORE_ADDR
   ((CORE_ADDR) (((unsigned long) (addr)) + 8 + (sbits (instr, 0, 23) << 2)))
 
 /* Forward declaration.  */
-struct regcache;
+struct reg_buffer_common;
 
 /* Return the size in bytes of the complete Thumb instruction whose
    first halfword is INST1.  */
@@ -213,7 +213,7 @@ int thumb_advance_itstate (unsigned int itstate);
 
 /* Decode shifted register value.  */
 
-unsigned long shifted_reg_val (struct regcache *regcache,
+unsigned long shifted_reg_val (reg_buffer_common *regcache,
 			       unsigned long inst,
 			       int carry,
 			       unsigned long pc_val,