[PATCH] Fix dead_debug_insert_before ICE (PR debug/49522, take 2)

[Jakub Jelinek <jakub@redhat.com>]

On Tue, Jul 05, 2011 at 10:06:51PM +0200, Jakub Jelinek wrote:
> 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.

And here is a version that passed bootstrap/regtest on x86_64-linux and
i686-linux:

2011-07-06  Jakub Jelinek  <jakub@redhat.com>

	PR debug/49522
	* df-problems.c (dead_debug_reset): Remove dead_debug_uses
	referencing debug insns that have been reset.
	(dead_debug_insert_before): Don't assert reg is non-NULL,
	instead return immediately if it is NULL.

	* gcc.dg/debug/pr49522.c: New test.

--- gcc/df-problems.c.jj	2011-07-04 19:17:50.757435754 +0200
+++ gcc/df-problems.c	2011-07-06 17:20:06.264420868 +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
@@ -3174,7 +3193,8 @@ dead_debug_insert_before (struct dead_de
 	tailp = &(*tailp)->next;
     }
 
-  gcc_assert (reg);
+  if (reg == NULL)
+    return;
 
   /* Create DEBUG_EXPR (and DEBUG_EXPR_DECL).  */
   dval = make_debug_expr_from_rtl (reg);
--- gcc/testsuite/gcc.dg/debug/pr49522.c.jj	2011-07-04 10:54:23.000000000 +0200
+++ gcc/testsuite/gcc.dg/debug/pr49522.c	2011-07-04 10:54:02.000000000 +0200
@@ -0,0 +1,41 @@
+/* PR debug/49522 */
+/* { dg-do compile } */
+/* { dg-options "-fcompare-debug" } */
+
+int val1 = 0L;
+volatile int val2 = 7L;
+long long val3;
+int *ptr = &val1;
+
+static int
+func1 ()
+{
+  return 0;
+}
+
+static short int
+func2 (short int a, unsigned int b)
+{
+  return !b ? a : a >> b;
+}
+
+static unsigned long long
+func3 (unsigned long long a, unsigned long long b)
+{
+  return !b ? a : a % b;
+}
+
+void
+func4 (unsigned short arg1, int arg2)
+{
+  for (arg2 = 0; arg2 < 2; arg2++)
+    {
+      *ptr = func3 (func3 (10, func2 (val3, val2)), val3);
+      for (arg1 = -14; arg1 > 14; arg1 = func1 ())
+	{
+	  *ptr = -1;
+	  if (foo ())
+	    ;
+	}
+    }
+}

	Jakub