[RFA] Fix mips32_relative_offset()

[Mark Kettenis <kettenis@gnu.org>]

The current code assumes that sizeof(long) == 32, which obviously
isn't true on LP64 platforms.  The attached patch fixes that by using
the sign-extension idiom that's also used for SPARC.  It still assumes
that a long can hold a 18-bit signed integer, but ISO C guarantees
that it can.

OK?

Mark

P.S. Incidentally I think the function should return a LONGEST instead
     of CORE_ADDR.


Index: ChangeLog
from  Mark Kettenis  <kettenis@gnu.org>

	* mips-tdep.c (mips32_relative_offset): Avoid ussumption that
	sizeof(long) == 32.

Index: mips-tdep.c
===================================================================
RCS file: /cvs/src/src/gdb/mips-tdep.c,v
retrieving revision 1.362
diff -u -p -r1.362 mips-tdep.c
--- mips-tdep.c 31 Oct 2004 21:51:58 -0000 1.362
+++ mips-tdep.c 9 Nov 2004 12:51:40 -0000
@@ -881,14 +881,8 @@ mips_fetch_instruction (CORE_ADDR addr)
 static CORE_ADDR
 mips32_relative_offset (unsigned long inst)
 {
-  long x;
-  x = itype_immediate (inst);
-  if (x & 0x8000)		/* sign bit set */
-    {
-      x |= 0xffff0000;		/* sign extension */
-    }
-  x = x << 2;
-  return x;
+  long x = ((itype_immediate (inst) ^ 0x8000) - 0x8000);
+  return x << 2;
 }
 
 /* Determine whate to set a single step breakpoint while considering