[PATCH] simplify_rtx shouldn't modify its argument

[Geoff Keating]

Roger Sayle <roger@eyesopen.com> writes:

> The following patch is another step towards unification of GCC's
> RTL simplifiers.  The preferred "one", simplify_rtx, is far more
> useful to the rest of the compiler if it doesn't modify its
> argument directly, especially if it then decides to return NULL_RTX
> anyway, providing no warning of the modification to the caller.
> 
> 
> The following patch has been tested on i686-pc-linux-gnu with a
> complete "make bbotstrap", all languages except treelang, and regression
> tested with a top-level "make -k check" with no new failures.
> 
> 
> Ok for mainline?

Could you look at the history of this code?  It seems odd to me that
it wouldn't have been written this way all along...

> 2003-07-17  Roger Sayle  <roger@eyesopen.com>
> 
> 	* simplify-rtx.c (simplify_rtx): Use simplify_gen_binary to swap
> 	commutative operands instead of modifying the RTL in-place.
> 
> 
> Index: simplify-rtx.c
> ===================================================================
> RCS file: /cvs/gcc/gcc/gcc/simplify-rtx.c,v
> retrieving revision 1.148
> diff -c -3 -p -r1.148 simplify-rtx.c
> *** simplify-rtx.c	16 Jul 2003 19:34:50 -0000	1.148
> --- simplify-rtx.c	17 Jul 2003 12:45:44 -0000
> *************** simplify_rtx (rtx x)
> *** 3048,3062 ****
>   				       XEXP (x, 0), GET_MODE (XEXP (x, 0)));
>       case 'c':
>         if (swap_commutative_operands_p (XEXP (x, 0), XEXP (x, 1)))
> ! 	{
> ! 	  rtx tem;
> 
> ! 	  tem = XEXP (x, 0);
> ! 	  XEXP (x, 0) = XEXP (x, 1);
> ! 	  XEXP (x, 1) = tem;
> ! 	  return simplify_binary_operation (code, mode,
> ! 					    XEXP (x, 0), XEXP (x, 1));
> ! 	}
> 
>       case '2':
>         return simplify_binary_operation (code, mode, XEXP (x, 0), XEXP (x, 1));
> --- 3048,3056 ----
>   				       XEXP (x, 0), GET_MODE (XEXP (x, 0)));
>       case 'c':
>         if (swap_commutative_operands_p (XEXP (x, 0), XEXP (x, 1)))
> ! 	return simplify_gen_binary (code, mode, XEXP (x, 1), XEXP (x, 0));
> 
> !       /* ... fall through ... */
> 
>       case '2':
>         return simplify_binary_operation (code, mode, XEXP (x, 0), XEXP (x, 1));
> 
> 
> Roger
> --
> Roger Sayle,                         E-mail: roger@eyesopen.com
> OpenEye Scientific Software,         WWW: http://www.eyesopen.com/
> Suite 1107, 3600 Cerrillos Road,     Tel: (+1) 505-473-7385
> Santa Fe, New Mexico, 87507.         Fax: (+1) 505-473-0833
> 
> 

-- 
- Geoffrey Keating <geoffk@geoffk.org>