[RFA] Fix mips32_relative_offset()

[RFA] Fix mips32_relative_offset()

[Mark Kettenis]

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

Re: [RFA] Fix mips32_relative_offset()

[Andrew Cagney]

Mark Kettenis wrote:
> 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?

Yes.

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

and take a ULONGEST as input.  If you want to do that, ok.

Andrew

> 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
> 

Re: [RFA] Fix mips32_relative_offset()

[Mark Kettenis]

   Date: Wed, 10 Nov 2004 09:38:20 -0500
   From: Andrew Cagney <cagney@gnu.org>

   Mark Kettenis wrote:
   > 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?

   Yes.

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

   and take a ULONGEST as input.  If you want to do that, ok.

Thanks, I committed the attached.

Mark


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

	* mips-tdep.c (mips32_relative_offset): Change return type to
	LONGEST, change argument type to ULONGEST.  Fix sign-extension.

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 10 Nov 2004 17:45:32 -0000
@@ -878,17 +878,10 @@ mips_fetch_instruction (CORE_ADDR addr)
 #define rtype_shamt(x) ((x >> 6) & 0x1f)
 #define rtype_funct(x) (x & 0x3f)
 
-static CORE_ADDR
-mips32_relative_offset (unsigned long inst)
+static LONGEST
+mips32_relative_offset (ULONGEST inst)
 {
-  long x;
-  x = itype_immediate (inst);
-  if (x & 0x8000)		/* sign bit set */
-    {
-      x |= 0xffff0000;		/* sign extension */
-    }
-  x = x << 2;
-  return x;
+  return ((itype_immediate (inst) ^ 0x8000) - 0x8000) << 2;
 }
 
 /* Determine whate to set a single step breakpoint while considering