Re: [rfa/arm] Handle bx and blx

[Daniel Jacobowitz <drow@false.org>]

On Wed, Mar 03, 2004 at 04:01:55PM +0000, Richard Earnshaw wrote:
> > The software single-step implementation in GDB doesn't know either BX or
> > BLX.  This results in losing control of the inferior when we single-step
> > over them.  I based this on the ARM ARM, so I'm pretty sure I've got the
> > numbers correct.
> > 
> > OK to check in?
> > 
> > -- 
> > Daniel Jacobowitz
> > MontaVista Software                         Debian GNU/Linux Developer
> > 
> > 2004-02-28  Daniel Jacobowitz  <drow@mvista.com>
> > 
> > 	* arm-tdep.c (thumb_get_next_pc): Handle BX.
> > 	(arm_get_next_pc): Handle BX and BLX.
> 
> Yikes!  Yes, this is OK.  However, Thumb has BLX (2 variants) as well.

Right you are.  I've checked in the above; if I'm reading
thumb_get_next_pc and the ARM correctly, then the below is all I need
for BLX.  The first form is already handled since we don't check H.
The second form can be handled identically to BX by relaxing a test.

OK?

-- 
Daniel Jacobowitz
MontaVista Software                         Debian GNU/Linux Developer

2004-03-07  Daniel Jacobowitz  <drow@mvista.com>

	* arm-tdep.c (thumb_get_next_pc): Handle Thumb BLX.

Index: arm-tdep.c
===================================================================
RCS file: /cvs/src/src/gdb/arm-tdep.c,v
retrieving revision 1.165
diff -u -p -r1.165 arm-tdep.c
--- arm-tdep.c	7 Mar 2004 20:03:12 -0000	1.165
+++ arm-tdep.c	7 Mar 2004 20:13:34 -0000
@@ -1651,13 +1651,13 @@ thumb_get_next_pc (CORE_ADDR pc)
     {
       nextpc = pc_val + (sbits (inst1, 0, 10) << 1);
     }
-  else if ((inst1 & 0xf800) == 0xf000)	/* long branch with link */
+  else if ((inst1 & 0xf800) == 0xf000)	/* long branch with link, and blx */
     {
       unsigned short inst2 = read_memory_integer (pc + 2, 2);
       offset = (sbits (inst1, 0, 10) << 12) + (bits (inst2, 0, 10) << 1);
       nextpc = pc_val + offset;
     }
-  else if ((inst1 & 0xff80) == 0x4700)	/* branch and exchange (bx) */
+  else if ((inst1 & 0xff00) == 0x4700)	/* bx REG, blx REG */
     {
       if (bits (inst1, 3, 6) == 0x0f)
 	nextpc = pc_val;