regcache: Add functions suitable for regset_supply/collect.

These functions are intended to suit all targets that don't require too
special logic in their regset supply/collect methods.  Having such
generic functions helps reducing target-specific complexity.

gdb/ChangeLog

@@ -1,3 +1,12 @@
+2014-08-07  Andreas Arnez  <arnez@linux.vnet.ibm.com>
+
+	* regcache.c: Include "regset.h".
+	(regcache_transfer_regset): New local function.
+	(regcache_supply_regset, regcache_collect_regset): New functions.
+	* regcache.h (struct regcache_map_entry): New structure.
+	(REGCACHE_MAP_SKIP): New enum value.
+	(regcache_supply_regset, regcache_collect_regset): New prototypes.
+
 2014-08-07  Andreas Arnez  <arnez@linux.vnet.ibm.com>
 
 	* regset.h (struct regset): Rename 'descr' field to 'regmap'.

gdb/regcache.c

@@ -28,6 +28,7 @@
 #include "exceptions.h"
 #include "remote.h"
 #include "valprint.h"
+#include "regset.h"
 
 /*
  * DATA STRUCTURE
@@ -1066,6 +1067,92 @@ regcache_raw_collect (const struct regcache *regcache, int regnum, void *buf)
   memcpy (buf, regbuf, size);
 }
 
+/* Transfer a single or all registers belonging to a certain register
+   set to or from a buffer.  This is the main worker function for
+   regcache_supply_regset and regcache_collect_regset.  */
+
+static void
+regcache_transfer_regset (const struct regset *regset,
+			  const struct regcache *regcache,
+			  struct regcache *out_regcache,
+			  int regnum, const void *in_buf,
+			  void *out_buf, size_t size)
+{
+  const struct regcache_map_entry *map;
+  int offs = 0, count;
+
+  for (map = regset->regmap; (count = map->count) != 0; map++)
+    {
+      int regno = map->regno;
+      int slot_size = map->size;
+
+      if (slot_size == 0 && regno != REGCACHE_MAP_SKIP)
+	slot_size = regcache->descr->sizeof_register[regno];
+
+      if (regno == REGCACHE_MAP_SKIP
+	  || (regnum != -1
+	      && (regnum < regno || regnum >= regno + count)))
+	  offs += count * slot_size;
+
+      else if (regnum == -1)
+	for (; count--; regno++, offs += slot_size)
+	  {
+	    if (offs + slot_size > size)
+	      break;
+
+	    if (out_buf)
+	      regcache_raw_collect (regcache, regno,
+				    (gdb_byte *) out_buf + offs);
+	    else
+	      regcache_raw_supply (out_regcache, regno, in_buf
+				   ? (const gdb_byte *) in_buf + offs
+				   : NULL);
+	  }
+      else
+	{
+	  /* Transfer a single register and return.  */
+	  offs += (regnum - regno) * slot_size;
+	  if (offs + slot_size > size)
+	    return;
+
+	  if (out_buf)
+	    regcache_raw_collect (regcache, regnum,
+				  (gdb_byte *) out_buf + offs);
+	  else
+	    regcache_raw_supply (out_regcache, regnum, in_buf
+				 ? (const gdb_byte *) in_buf + offs
+				 : NULL);
+	  return;
+	}
+    }
+}
+
+/* Supply register REGNUM from BUF to REGCACHE, using the register map
+   in REGSET.  If REGNUM is -1, do this for all registers in REGSET.
+   If BUF is NULL, set the register(s) to "unavailable" status. */
+
+void
+regcache_supply_regset (const struct regset *regset,
+			struct regcache *regcache,
+			int regnum, const void *buf, size_t size)
+{
+  regcache_transfer_regset (regset, regcache, regcache, regnum,
+			    buf, NULL, size);
+}
+
+/* Collect register REGNUM from REGCACHE to BUF, using the register
+   map in REGSET.  If REGNUM is -1, do this for all registers in
+   REGSET.  */
+
+void
+regcache_collect_regset (const struct regset *regset,
+			 const struct regcache *regcache,
+			 int regnum, void *buf, size_t size)
+{
+  regcache_transfer_regset (regset, regcache, NULL, regnum,
+			    NULL, buf, size);
+}
+
 
 /* Special handling for register PC.  */
 

gdb/regcache.h

@@ -147,6 +147,51 @@ extern void regcache_raw_supply (struct regcache *regcache,
 extern void regcache_raw_collect (const struct regcache *regcache,
 				  int regnum, void *buf);
 
+/* Mapping between register numbers and offsets in a buffer, for use
+   in the '*regset' functions below.  In an array of
+   'regcache_map_entry' each element is interpreted like follows:
+
+   - If 'regno' is a register number: Map register 'regno' to the
+     current offset (starting with 0) and increase the current offset
+     by 'size' (or the register's size, if 'size' is zero).  Repeat
+     this with consecutive register numbers up to 'regno+count-1'.
+
+   - If 'regno' is REGCACHE_MAP_SKIP: Add 'count*size' to the current
+     offset.
+
+   - If count=0: End of the map.  */
+
+struct regcache_map_entry
+{
+  int count;
+  int regno;
+  int size;
+};
+
+/* Special value for the 'regno' field in the struct above.  */
+
+enum
+  {
+    REGCACHE_MAP_SKIP = -1,
+  };
+
+/* Transfer a set of registers (as described by REGSET) between
+   REGCACHE and BUF.  If REGNUM == -1, transfer all registers
+   belonging to the regset, otherwise just the register numbered
+   REGNUM.  The REGSET's 'regmap' field must point to an array of
+   'struct regcache_map_entry'.
+
+   These functions are suitable for the 'regset_supply' and
+   'regset_collect' fields in a regset structure.  */
+
+extern void regcache_supply_regset (const struct regset *regset,
+				    struct regcache *regcache,
+				    int regnum, const void *buf,
+				    size_t size);
+extern void regcache_collect_regset (const struct regset *regset,
+				     const struct regcache *regcache,
+				     int regnum, void *buf, size_t size);
+
 
 /* The type of a register.  This function is slightly more efficient
    then its gdbarch vector counterpart since it returns a precomputed