Re: [RFC] mips-tdep.c: pseudo-register -> raw register sign extension

[Kevin Buettner <kevinb@redhat.com>]

On Thu, 9 Dec 2010 12:19:00 +0100 (CET)
Mark Kettenis <mark.kettenis@xs4all.nl> wrote:

> > +	  LONGEST regval = extract_signed_integer (buf, 4, byte_order);
> > +	  store_signed_integer (buf8, 8, byte_order, regval);
> > +	  regcache_raw_write (regcache, rawnum, buf8);
> 
> How about using regcache_raw_write_signed() here?  I think that
> simplifies the code enough to change mips_pseudo_register_read() to
> use regcache_raw_read_signed() and get rid of the explicit endian-ness
> check as well.

I like this suggestion.  See below for a revised patch...

Kevin

	* mips-tdep.c (mips_pseudo_register_write): Sign extend 32-bit
	cooked values that are being transferred to 64-bit raw registers.
	(mips_pseudo_register_read): Revise to preserve symmetry with
	mips_pseudo_register_write().

Index: mips-tdep.c
===================================================================
RCS file: /cvs/src/src/gdb/mips-tdep.c,v
retrieving revision 1.508
diff -u -p -r1.508 mips-tdep.c
--- mips-tdep.c	28 Nov 2010 04:31:24 -0000	1.508
+++ mips-tdep.c	9 Dec 2010 23:03:02 -0000
@@ -559,11 +559,15 @@ mips_pseudo_register_read (struct gdbarc
   else if (register_size (gdbarch, rawnum) >
 	   register_size (gdbarch, cookednum))
     {
-      if (gdbarch_tdep (gdbarch)->mips64_transfers_32bit_regs_p
-	  || gdbarch_byte_order (gdbarch) == BFD_ENDIAN_LITTLE)
+      if (gdbarch_tdep (gdbarch)->mips64_transfers_32bit_regs_p)
 	regcache_raw_read_part (regcache, rawnum, 0, 4, buf);
       else
-	regcache_raw_read_part (regcache, rawnum, 4, 4, buf);
+	{
+	  enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
+	  LONGEST regval;
+	  regcache_raw_read_signed (regcache, rawnum, &regval);
+	  store_signed_integer (buf, 4, byte_order, regval);
+	}
     }
   else
     internal_error (__FILE__, __LINE__, _("bad register size"));
@@ -582,11 +586,17 @@ mips_pseudo_register_write (struct gdbar
   else if (register_size (gdbarch, rawnum) >
 	   register_size (gdbarch, cookednum))
     {
-      if (gdbarch_tdep (gdbarch)->mips64_transfers_32bit_regs_p
-	  || gdbarch_byte_order (gdbarch) == BFD_ENDIAN_LITTLE)
+      if (gdbarch_tdep (gdbarch)->mips64_transfers_32bit_regs_p)
 	regcache_raw_write_part (regcache, rawnum, 0, 4, buf);
       else
-	regcache_raw_write_part (regcache, rawnum, 4, 4, buf);
+	{
+	  /* Sign extend the shortened version of the register prior
+	     to placing it in the raw register.  This is required for
+	     some mips64 parts in order to avoid unpredictable behavior.  */
+	  enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
+	  LONGEST regval = extract_signed_integer (buf, 4, byte_order);
+	  regcache_raw_write_signed (regcache, rawnum, regval);
+	}
     }
   else
     internal_error (__FILE__, __LINE__, _("bad register size"));