[rfa/arm] Handle bx and blx

[Daniel Jacobowitz <drow@false.org>]

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.

Index: gdb/arm-tdep.c
===================================================================
RCS file: /big/fsf/rsync/src-cvs/src/gdb/arm-tdep.c,v
retrieving revision 1.164
diff -u -p -r1.164 arm-tdep.c
--- gdb/arm-tdep.c	16 Feb 2004 21:49:21 -0000	1.164
+++ gdb/arm-tdep.c	28 Feb 2004 03:37:18 -0000
@@ -1657,6 +1658,17 @@ thumb_get_next_pc (CORE_ADDR pc)
       offset = (sbits (inst1, 0, 10) << 12) + (bits (inst2, 0, 10) << 1);
       nextpc = pc_val + offset;
     }
+  else if ((inst1 & 0xff80) == 0x4700)	/* branch and exchange (bx) */
+    {
+      if (bits (inst1, 3, 6) == 0x0f)
+	nextpc = pc_val;
+      else
+	nextpc = read_register (bits (inst1, 3, 6));
+
+      nextpc = ADDR_BITS_REMOVE (nextpc);
+      if (nextpc == pc)
+	error ("Infinite loop detected");
+    }
 
   return nextpc;
 }
@@ -1697,6 +1709,20 @@ arm_get_next_pc (CORE_ADDR pc)
 		&& bits (this_instr, 4, 7) == 9)	/* multiply */
 	      error ("Illegal update to pc in instruction");
 
+	    /* BX <reg>, BLX <reg> */
+	    if (bits (this_instr, 4, 28) == 0x12fff1
+		|| bits (this_instr, 4, 28) == 0x12fff3)
+	      {
+		rn = bits (this_instr, 0, 3);
+		result = (rn == 15) ? pc_val + 8 : read_register (rn);
+		nextpc = (CORE_ADDR) ADDR_BITS_REMOVE (result);
+
+		if (nextpc == pc)
+		  error ("Infinite loop detected");
+
+		return nextpc;
+	      }
+
 	    /* Multiply into PC */
 	    c = (status & FLAG_C) ? 1 : 0;
 	    rn = bits (this_instr, 16, 19);
@@ -1862,6 +1888,10 @@ arm_get_next_pc (CORE_ADDR pc)
 	  {
 	    nextpc = BranchDest (pc, this_instr);
 
+	    /* BLX */
+	    if (bits (this_instr, 28, 31) == INST_NV)
+	      nextpc |= bit (this_instr, 24) << 1;
+
 	    nextpc = ADDR_BITS_REMOVE (nextpc);
 	    if (nextpc == pc)
 	      error ("Infinite loop detected");