See http://gcc.gnu.org/ml/gcc-patches/2004-09/msg01240.html, this causes
us to miss sibcall opportunities with -g

Index: gcc-3.3.3/gcc/sibcall.c
===================================================================
--- gcc-3.3.3.orig/gcc/sibcall.c	2009-11-20 13:04:57.000000000 +0100
+++ gcc-3.3.3/gcc/sibcall.c	2009-11-20 13:06:50.000000000 +0100
@@ -377,7 +377,8 @@ call_ends_block_p (insn, end)
 {
   rtx new_insn;
   /* END might be a note, so get the last nonnote insn of the block.  */
-  end = next_nonnote_insn (PREV_INSN (end));
+  if (GET_CODE (end) == NOTE)
+    end = prev_nonnote_insn (end);
 
   /* If the call was the end of the block, then we're OK.  */
   if (insn == end)