re: [dataflow][RFC] Fix mode-switching for MODE_ENTRY/EXIT target

[Kenneth Zadeck <Kenneth dot Zadeck at NaturalBridge dot com>]

Kaz

This is fine for the dataflow branch.

Kenny

> This is against mode-switching.c but would be actually SH specific.
> In mode-switching.c/optimize_mode_switching, split_edge and
> create_pre_exit might make new blocks after df_analyze is already done.
> It causes a segfault:
> 
> Program received signal SIGSEGV, Segmentation fault.
> 0x08530503 in rest_of_handle_mode_switching ()
>     at ../../TMP/dataflow/gcc/mode-switching.c:463
> 463               REG_SET_TO_HARD_REG_SET (live_now, DF_LIVE_IN (bb));
> 
> The attached patch moves df_analyze after split_edge and create_pre_exit.
> This change will affect the SH target only because these split_edge and
> create_pre_exit are guarded with MODE_ENTRY/EXIT macros which are defined
> only by SH now.  The first hunk of the patch is to tweak create_pre_exit
> for -O0.  When runnning C testsuite for SH, I see ICEs with
> 
>   internal compiler error: in create_pre_exit, at mode-switching.c:352
> 
> It seems that the rtl (clobber (reg [<result>])) was optimized away
> with the trunk compiler even at -O0 but isn't optimized away with
> the dataflow-branch compiler at -O0.  The attached patch is to handle
> this.  Again it'll affect SH only because create_pre_exit is called
> by SH backend only.
> Bootstrapped and regtested on i686-pc-linux-gnu and sh4-unknown-linux-gnu
> with no new failures.
> 
> Regards,
> 	kaz
> --
> 	* mode-switching.c (create_pre_exit): Skip CLOBBER of pseudo
> 	register for the result when not optimizing.
> 	(optimize_mode_switching): Move	df_ri_add_problem and df_analyze
> 	calls after create_pre_exit call.
> 
> diff -uprN ORIG/dataflow/gcc/mode-switching.c LOCAL/dataflow/gcc/mode-switching.c
> --- ORIG/dataflow/gcc/mode-switching.c	2007-01-24 09:06:41.000000000 +0900
> +++ LOCAL/dataflow/gcc/mode-switching.c	2007-01-26 20:56:58.000000000 +0900
> @@ -1,5 +1,5 @@
>  /* CPU mode switching
> -   Copyright (C) 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005
> +   Copyright (C) 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2007
>     Free Software Foundation, Inc.
>  
>  This file is part of GCC.
> @@ -268,6 +268,25 @@ create_pre_exit (int n_entities, int *en
>  			return_copy_pat = PATTERN (return_copy);
>  			if (GET_CODE (return_copy_pat) != CLOBBER)
>  			  break;
> +			else if (!optimize)
> +			  {
> +			    /* This might be (clobber (reg [<result>]))
> +			       when not optimizing.  Then check if
> +			       the previous insn is the clobber for
> +			       the return register.  */
> +			    copy_reg = SET_DEST (return_copy_pat);
> +			    if (GET_CODE (copy_reg) == REG
> +				&& !HARD_REGISTER_NUM_P (REGNO (copy_reg)))
> +			      {
> +				if (INSN_P (PREV_INSN (return_copy)))
> +				  {
> +				    return_copy = PREV_INSN (return_copy);
> +				    return_copy_pat = PATTERN (return_copy);
> +				    if (GET_CODE (return_copy_pat) != CLOBBER)
> +				      break;
> +				  }
> +			      }
> +			  }
>  		      }
>  		    copy_reg = SET_DEST (return_copy_pat);
>  		    if (GET_CODE (copy_reg) == REG)
> @@ -420,9 +439,6 @@ optimize_mode_switching (void)
>    if (! n_entities)
>      return 0;
>  
> -  df_ri_add_problem (0);
> -  df_analyze ();
> -
>  #if defined (MODE_ENTRY) && defined (MODE_EXIT)
>    /* Split the edge from the entry block, so that we can note that
>       there NORMAL_MODE is supplied.  */
> @@ -430,6 +446,9 @@ optimize_mode_switching (void)
>    pre_exit = create_pre_exit (n_entities, entity_map, num_modes);
>  #endif
>  
> +  df_ri_add_problem (0);
> +  df_analyze ();
> +
>    /* Create the bitmap vectors.  */
>  
>    antic = sbitmap_vector_alloc (last_basic_block, n_entities);