df-scan.c (df_notes_rescan): Do nothing if the instruction does not yet have a basic block.

gcc/
	* df-scan.c (df_notes_rescan): Do nothing if the instruction does
	not yet have a basic block.
	* dse.c (find_shift_sequence): Don't set DF_NO_INSN_RESCAN.

From-SVN: r128563

gcc/ChangeLog

 2007-09-18  Richard Sandiford  <rsandifo@nildram.co.uk>
 
+	* df-scan.c (df_notes_rescan): Do nothing if the instruction does
+	not yet have a basic block.
+	* dse.c (find_shift_sequence): Don't set DF_NO_INSN_RESCAN.
+
+2007-09-18  Richard Sandiford  <rsandifo@nildram.co.uk>
+
 	* config/mips/mips.c (mips_file_start): Add ".previous" directives
 	to both ".section"s.
 

gcc/df-scan.c

@@ -2004,6 +2004,10 @@ df_notes_rescan (rtx insn)
   if (df->changeable_flags & DF_NO_INSN_RESCAN)
     return;
 
+  /* Do nothing if the insn hasn't been emitted yet.  */
+  if (!BLOCK_FOR_INSN (insn))
+    return;
+
   df_grow_bb_info (df_scan);
   df_grow_reg_info ();
 

gcc/dse.c

@@ -1428,10 +1428,8 @@ find_shift_sequence (rtx read_reg,
       /* In theory we could also check for an ashr.  Ian Taylor knows
 	 of one dsp where the cost of these two was not the same.  But
 	 this really is a rare case anyway.  */
-      df_set_flags (DF_NO_INSN_RESCAN);
       target = expand_binop (new_mode, lshr_optab, new_reg,
 			     GEN_INT (shift), new_reg, 1, OPTAB_DIRECT);
-      df_clear_flags (DF_NO_INSN_RESCAN);
 
       if (target == new_reg)
 	{