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.


M    gcc/ChangeLog
A    gcc/testsuite/gcc.dg/debug/pr49522.c
M    gcc/testsuite/ChangeLog
M    gcc/df-problems.c


git-svn-id: https://gcc.gnu.org/svn/gcc/trunk@175987 138bc75d-0d04-0410-961f-82ee72b054a4

1 files changed, 22 insertions, 2 deletions

diff --git a/gcc/df-problems.c b/gcc/df-problems.c
index 59bed8bd667..e547b67c55f 100644
--- a/gcc/df-problems.c
+++ b/gcc/df-problems.c
@@ -3096,6 +3096,7 @@ static void
 dead_debug_reset (struct dead_debug *debug, unsigned int dregno)
 {
   struct dead_debug_use **tailp = &debug->head;
+  struct dead_debug_use **insnp = &debug->head;
   struct dead_debug_use *cur;
   rtx insn;
 
@@ -3113,9 +3114,25 @@ dead_debug_reset (struct dead_debug *debug, unsigned int dregno)
 	    debug->to_rescan = BITMAP_ALLOC (NULL);
 	  bitmap_set_bit (debug->to_rescan, INSN_UID (insn));
 	  XDELETE (cur);
+	  /* If the current use isn't the first one attached to INSN, go back
+	     to this first use.  We assume that the uses attached to an insn
+	     are adjacent.  */                                                                       
+	  if (tailp != insnp && DF_REF_INSN ((*insnp)->use) == insn)
+	    tailp = insnp;
+	  /* Then remove all the other uses attached to INSN.  */
+	  while ((cur = *tailp) && DF_REF_INSN (cur->use) == insn)
+	    {
+	      *tailp = cur->next;
+	      XDELETE (cur);
+	    }
+	  insnp = tailp;
 	}
       else
-	tailp = &(*tailp)->next;
+	{
+	  if (DF_REF_INSN ((*insnp)->use) != DF_REF_INSN (cur->use))
+	    insnp = tailp;
+	  tailp = &(*tailp)->next;
+	}
     }
 }
 
@@ -3174,7 +3191,10 @@ dead_debug_insert_before (struct dead_debug *debug, unsigned int uregno,
 	tailp = &(*tailp)->next;
     }
 
-  gcc_assert (reg);
+  /* We may have dangling bits in debug->used for registers that were part
+     of a multi-register use, one component of which has been reset.  */
+  if (reg == NULL)
+    return;
 
   /* Create DEBUG_EXPR (and DEBUG_EXPR_DECL).  */
   dval = make_debug_expr_from_rtl (reg);