* findvar.c (value_of_register, value_from_register),

hppa-tdep.c (pa_print_fp_reg), infcmd.c (do_registers_info),
	valops.c (value_assign):   Use REGISTER_CONVERT_TO_* only if
	REGISTER_CONVERTIBLE is defined, otherwise just copy the content.
	Pass desired type to REGISTER_CONVERT_TO_*.

	* config/m68k/tm-m68k.h, config/i960/tm-i960.h (REGISTER_CONVERT_*):
	Pass length of desired type to store/extract_floating.
	* config/i386/tm-arm.h, config/i386/tm-i386aix.h,
	config/i386/tm-sun386.h, config/i386/tm-symmetry.h,
	config/m88k/tm-m88k.h config/rs6000/tm-rs6000.h (REGISTER_CONVERT_*):
	Use extract_floating and store_floating with length of desired type.
	* config/m68k/tm-news.h (STORE,EXTRACT_RETURN_VALUE):  Add type
	parameter to REGISTER_CONVERT_*.

	* config/a29k/tm-a29k.h, config/convex/tm-convex.h,
	config/gould/tm-np1.h, config/gould/tm-pn.h, config/h8300/tm-h8300.h,
	config/h8500/tm-h8500.h, config/i386/tm-i386v.h,
	config/mips/tm-mips.h, config/ns32k/tm-merlin.h,
	config/ns32k/tm-umax.h, config/pa/tm-hppa.h, config/pyr/tm-pyr.h,
	config/sh/tm-sh.h, config/sparc/tm-sparc.h, config/tahoe/tm-tahoe.h,
	config/vax/tm-vax.h, config/z8k/tm-z8k.h (REGISTER_CONVERTIBLE,
	REGISTER_CONVERT_TO_RAW, REGISTER_CONVERT_TO_VIRTUAL):  Remove
	versions for which REGISTER_CONVERTIBLE is always false.
	* z8k-tdep.c (register_convert_to_virtual, register_convert_to_raw):
	Remove, no longer used.

	* alpha-tdep.c (alpha_register_convert_to_raw,
	alpha_register_convert_to_virtual):  New routines to handle
	the different raw formats in alpha floating point registers.
	* config/alpha/tm-alpha.h (REGISTER_CONVERTIBLE,
	REGISTER_CONVERT_TO_VIRTUAL, REGISTER_CONVERT_TO_RAW):  Use them.

gdb/valops.c

@@ -286,7 +286,6 @@ value_assign (toval, fromval)
   register struct type *type = VALUE_TYPE (toval);
   register value val;
   char raw_buffer[MAX_REGISTER_RAW_SIZE];
-  char virtual_buffer[MAX_REGISTER_VIRTUAL_SIZE];
   int use_buffer = 0;
 
   COERCE_ARRAY (fromval);
@@ -300,17 +299,19 @@ value_assign (toval, fromval)
      convert FROMVAL's contents now, with result in `raw_buffer',
      and set USE_BUFFER to the number of bytes to write.  */
 
+#ifdef REGISTER_CONVERTIBLE
   if (VALUE_REGNO (toval) >= 0
       && REGISTER_CONVERTIBLE (VALUE_REGNO (toval)))
     {
       int regno = VALUE_REGNO (toval);
-      if (VALUE_TYPE (fromval) != REGISTER_VIRTUAL_TYPE (regno))
-	fromval = value_cast (REGISTER_VIRTUAL_TYPE (regno), fromval);
-      memcpy (virtual_buffer, VALUE_CONTENTS (fromval),
-	     REGISTER_VIRTUAL_SIZE (regno));
-      REGISTER_CONVERT_TO_RAW (regno, virtual_buffer, raw_buffer);
-      use_buffer = REGISTER_RAW_SIZE (regno);
+      if (REGISTER_CONVERTIBLE (regno))
+	{
+	  REGISTER_CONVERT_TO_RAW (VALUE_TYPE (fromval), regno,
+				   VALUE_CONTENTS (fromval), raw_buffer);
+	  use_buffer = REGISTER_RAW_SIZE (regno);
+	}
     }
+#endif
 
   switch (VALUE_LVAL (toval))
     {
@@ -336,10 +337,10 @@ value_assign (toval, fromval)
 		     + VALUE_BITSIZE (toval)
 		     + HOST_CHAR_BIT - 1)
 		    / HOST_CHAR_BIT;
-	  /* If bigger than a LONGEST, we don't handle it correctly,
-	     but at least avoid corrupting memory.  */
+
 	  if (len > sizeof (LONGEST))
-	    len = sizeof (LONGEST);
+	    error ("Can't handle bitfields which don't fit in a %d bit word.",
+		   sizeof (LONGEST) * HOST_CHAR_BIT);
 
 	  read_memory (VALUE_ADDRESS (toval) + VALUE_OFFSET (toval),
 		       buffer, len);
@@ -359,8 +360,20 @@ value_assign (toval, fromval)
     case lval_register:
       if (VALUE_BITSIZE (toval))
 	{
-	  char buffer[MAX_REGISTER_RAW_SIZE];
+	  char buffer[sizeof (LONGEST)];
           int len = REGISTER_RAW_SIZE (VALUE_REGNO (toval));
+
+	  if (len > sizeof (LONGEST))
+	    error ("Can't handle bitfields in registers larger than %d bits.",
+		   sizeof (LONGEST) * HOST_CHAR_BIT);
+
+	  if (VALUE_BITPOS (toval) + VALUE_BITSIZE (toval)
+	      > len * HOST_CHAR_BIT)
+	    /* Getting this right would involve being very careful about
+	       byte order.  */
+	    error ("\
+Can't handle bitfield which doesn't fit in a single register.");
+
           read_register_bytes (VALUE_ADDRESS (toval) + VALUE_OFFSET (toval),
                                buffer, len);
           modify_field (buffer, value_as_long (fromval),
@@ -485,9 +498,6 @@ value_assign (toval, fromval)
       type = VALUE_TYPE (fromval);
     }
 
-  /* FIXME: This loses if fromval is a different size than toval, for
-     example because fromval got cast in the REGISTER_CONVERTIBLE case
-     above.  */
   val = allocate_value (type);
   memcpy (val, toval, VALUE_CONTENTS_RAW (val) - (char *) val);
   memcpy (VALUE_CONTENTS_RAW (val), VALUE_CONTENTS (fromval),