2008-10-18  Pedro Alves  <pedro@codesourcery.com>

	* infrun.c (adjust_pc_after_break): Do nothing if executing in
	reverse.

---
 gdb/infrun.c |   27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)

Index: src/gdb/infrun.c
===================================================================
--- src.orig/gdb/infrun.c	2008-10-18 02:06:15.000000000 +0100
+++ src/gdb/infrun.c	2008-10-18 02:09:36.000000000 +0100
@@ -1787,6 +1787,33 @@ adjust_pc_after_break (struct execution_
   if (ecs->ws.value.sig != TARGET_SIGNAL_TRAP)
     return;
 
+  /* In reverse execution, when a breakpoint is hit, the instruction
+     under it has already been de-executed.  The reported PC always
+     points at the breakpoint address, so adjusting it further would
+     be wrong.  E.g., consider:
+
+       B1         0x08000000 :   INSN1
+       B2         0x08000001 :   INSN2
+		  0x08000002 :   INSN3
+	    PC -> 0x08000003 :   INSN4
+
+      Say you're stopped at 0x08000003 as above.  Reverse continuing
+      from that point should hit B2 as below.  Reading the PC when the
+      SIGTRAP is reported should read 0x08000001 and INSN2 should have
+      been de-executed already.
+
+       B1         0x08000000 :   INSN1
+       B2   PC -> 0x08000001 :   INSN2
+		  0x08000002 :   INSN3
+		  0x08000003 :   INSN4
+
+      If we tried to adjust the PC on for example, a
+      decr_pc_after_break == 1 architecture, we would wrongly further
+      adjust the PC to 0x08000000 and report a hit on B1, although the
+      INSN1 effects hadn't been de-executed yet.  */
+  if (execution_direction == EXEC_REVERSE)
+    return;
+
   /* If this target does not decrement the PC after breakpoints, then
      we have nothing to do.  */
   regcache = get_thread_regcache (ecs->ptid);