Re: [PATCH][RFC] Remove warning for SET VOIDmode -> BLKmode.

[Jeff Law <law at redhat dot com>]

On 11/03/2015 10:16 AM, Dominik Vogt wrote:
> (Debug code removed from patch.)
>
> Ciao
>
> Dominik ^_^  ^_^
>
> -- Dominik Vogt IBM Germany
>
>
> 0001-ChangeLog
>
>
> gcc/ChangeLog
>
> 	* genrecog.c (validate_pattern): Allow "set VOIDmode -> BLKmode" without
> 	warnings.
First, for reference, I was initially concerned the patterns were bogus, 
but these are reasonably canonical ways to implement memset and the like.

> 0001-Remove-warning-for-SET-VOIDmode-BLKmode.patch
>
>
>  From 04376919c108c42a2e9835dd1809b198bc47513f Mon Sep 17 00:00:00 2001
> From: Dominik Vogt<vogt@linux.vnet.ibm.com>
> Date: Tue, 3 Nov 2015 16:42:37 +0100
> Subject: [PATCH] Remove warning for SET VOIDmode -> BLKmode.
>
> ---
>   gcc/genrecog.c | 20 ++++++++++++++------
>   1 file changed, 14 insertions(+), 6 deletions(-)
>
> diff --git a/gcc/genrecog.c b/gcc/genrecog.c
> index 599121f..2c1fb47 100644
> --- a/gcc/genrecog.c
> +++ b/gcc/genrecog.c
> @@ -545,7 +545,7 @@ validate_pattern (rtx pattern, md_rtx_info *info, rtx set, int set_code)
> @@ -616,8 +616,13 @@ validate_pattern (rtx pattern, md_rtx_info *info, rtx set, int set_code)
>   	    && pred->allows_non_const
>   	    && strstr (c_test, "operands") == NULL
>   	    && ! (set
> +		  && set_code
>   		  && GET_CODE (set) == SET
> -		  && GET_CODE (SET_SRC (set)) == CALL))
> +		  && GET_CODE (SET_SRC (set)) == CALL)
> +	    && ! (set
> +		  && set_code == 0
> +		  && GET_CODE (set) == SET
> +		  && GET_MODE (SET_DEST (set)) == BLKmode))
Did you really mean to change the set_code test here?  It looks like you 
totally flipped it around.

> @@ -691,13 +697,15 @@ validate_pattern (rtx pattern, md_rtx_info *info, rtx set, int set_code)
>         return;
>
>       case ZERO_EXTRACT:
> -      validate_pattern (XEXP (pattern, 0), info, set, set ? '+' : 0);
> +      validate_pattern (XEXP (pattern, 0), info,
> +			set_code ? set : NULL_RTX, set_code ? '+' : 0);
>         validate_pattern (XEXP (pattern, 1), info, NULL_RTX, 0);
>         validate_pattern (XEXP (pattern, 2), info, NULL_RTX, 0);
>         return;
>
>       case STRICT_LOW_PART:
> -      validate_pattern (XEXP (pattern, 0), info, set, set ? '+' : 0);
> +      validate_pattern (XEXP (pattern, 0), info,
> +			set_code ? set : NULL_RTX, set_code ? '+' : 0);
>         return;
Don't these bypass the constraint checking when SET is non-null, but 
SET_CODE is 0?

I'd be a lot more comfortable here is you verified that patterns without 
the proper constraints got the proper warnings.  If you are indeed 
handling those cases right, comments would help.

Sadly, I don't think we have a good way to test gen* right now.

jeff