Index: unroll.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/unroll.c,v
retrieving revision 1.146
diff -u -r1.146 unroll.c
--- unroll.c	2001/11/16 17:08:12	1.146
+++ unroll.c	2001/11/26 16:44:55
@@ -3479,6 +3479,8 @@
   int unsigned_p, compare_dir, final_larger;
   rtx last_loop_insn;
   rtx reg_term;
+  rtx insn;
+  rtx end_loop_scan;
   struct iv_class *bl;
 
   loop_info->n_iterations = 0;
@@ -3704,6 +3706,62 @@
 
   if (initial_value == 0)
     return 0;
+
+  /* Some code transformations can result in code akin to
+
+	LOOP_BEG
+	  goto start;
+	top:
+	  i++;
+	start:
+	  ...
+	LOOP_CONT
+	  if (i < n) goto top;
+	LOOP_END
+
+     In this situation, we skip the increment the first time through
+     the loop, which results in an incorrect estimate of the number
+     of iterations.  As we did for GIVs above, adjust the initial value
+     to compensate.  */
+
+  off_by_one = 0;
+  if (loop->top)
+    end_loop_scan = loop->top;
+  else
+    end_loop_scan = loop->cont;
+
+  for (insn = loop->start; insn != end_loop_scan; insn = NEXT_INSN (insn))
+    if (GET_CODE (insn) == JUMP_INSN)
+      {
+	if (any_uncondjump_p (insn)
+	    && JUMP_LABEL (insn)
+	    && INSN_IN_RANGE_P (JUMP_LABEL (insn), insn, loop->end))
+	  {
+	    if (reg_set_between_p (bl->biv->src_reg, insn, JUMP_LABEL (insn)))
+	      off_by_one = 1;
+	    break;
+	  }
+	/* No idea what's going on.  */
+	if (loop_dump_stream)
+	  fprintf (loop_dump_stream,
+		   "Loop iterations: Confused by jump before loop top.\n");
+	return 0;
+      }
+
+  if (off_by_one)
+    {
+      if (loop_dump_stream)
+	fprintf (loop_dump_stream,
+		 "Loop iterations: Basic induction var skips initial incr.\n");
+      if (GET_CODE (increment) != CONST_INT)
+	{
+	  if (loop_dump_stream)
+	    fprintf (loop_dump_stream,
+		     "Loop iterations: Can't adjust with non-constant incr.\n");
+	  return 0;
+	}
+      initial_value = plus_constant (initial_value, -INTVAL (increment));
+    }
 
   unsigned_p = 0;
   off_by_one = 0;