Fix for 'Deadly optimization bug' (see egcs mailing list archive)

From-SVN: r28928

gcc/ChangeLog

+Fri Aug 27 10:33:35 1999  Bernd Schmidt  <bernds@cygnus.co.uk>
+
+	* combine.c (get_last_value): Don't look for earlier sets if the last
+	known set is somewhere in between the insns being combined.
+
 Fri Aug 27 10:03:12 BST 1999  Nathan Sidwell  <nathan@acm.org>
 
 	* configure.in: Don't use shell ! to negate exit codes

gcc/combine.c

@@ -10832,6 +10832,11 @@ get_last_value (x)
     {
       rtx insn, set;
 
+      /* We can't do anything if the value is set in between the insns we are
+	 processing.  */
+      if (INSN_CUID (reg_last_set[regno]) <= INSN_CUID (subst_insn))
+	return 0;
+
       /* We can not do anything useful in this case, because there is
 	 an instruction which is not on the insn chain.  */
       if (subst_prev_insn)