Re: [PATCH] Fix dead_debug_insert_before ICE (PR debug/49522)

[Jakub Jelinek <jakub@redhat.com>]

On Tue, Jul 05, 2011 at 10:35:11AM +0200, Eric Botcazou wrote:
> > There are two kinds of changes we do on the debug insns without immediate
> > rescanning:
> > 1) reset the debug insn
> > 2) replace a reg use with DEBUG_EXPR of the same mode or
> >    subreg of a larger DEBUG_EXPR with the same outer mode as the reg
> >
> > In the attached testcase on arm a debug insn is reset, because a multi-reg
> > register has been used there and as the debug insn location was that
> > multi-reg register before, it is now VOIDmode after the reset - (clobber
> > (const_int 0)).
> 
> That can happen only in this case, right?  Otherwise, for a single register, 
> the debug insn would have been removed from debug->head already.  If so, how 
> simpler would it be to remove the other uses in dead_debug_reset instead?

So you prefer something like this (untested) instead?
Without the second loop I have no idea how to make it work in
dead_debug_reset, the other dead_debug_use referencing the same insn might
be earlier or later in the chain.

--- gcc/df-problems.c	2011-07-04 19:17:50.757435754 +0200
+++ gcc/df-problems.c	2011-07-05 22:04:19.817464710 +0200
@@ -3117,6 +3117,25 @@ dead_debug_reset (struct dead_debug *deb
       else
 	tailp = &(*tailp)->next;
     }
+
+  /* If any other dead_debug_use structs refer to the debug insns
+     that have been reset above, remove them too.  */
+  if (debug->to_rescan != NULL)
+    {
+      tailp = &debug->head;
+      while ((cur = *tailp))
+	{
+	  insn = DF_REF_INSN (cur->use);
+	  if (bitmap_bit_p (debug->to_rescan, INSN_UID (insn))
+	      && VAR_LOC_UNKNOWN_P (INSN_VAR_LOCATION_LOC (insn)))
+	    {
+	      *tailp = cur->next;
+	      XDELETE (cur);
+	    }
+	  else
+	    tailp = &(*tailp)->next;
+	}
+    }
 }
 
 /* Add USE to DEBUG.  It must be a dead reference to UREGNO in a debug


	Jakub