This is the mail archive of the gcc-patches@gcc.gnu.org mailing list for the GCC project.


Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]
Other format: [Raw text]

Re: [PATCH] Fix up rotate expansion (take 2)


Doing some work on the msp430 failures, I discovered that this patch:

> --- gcc/expmed.c.jj	2013-05-07 10:26:46.000000000 +0200
> +++ gcc/expmed.c	2013-05-11 09:11:54.087412982 +0200
> @@ -2181,14 +2182,22 @@ expand_shift_1 (enum tree_code code, enu
>  	      rtx temp1;
>  
>  	      new_amount = op1;
> -	      if (CONST_INT_P (op1))
> +	      if (op1 == const0_rtx)
> +		return shifted;
> +	      else if (CONST_INT_P (op1))
>  		other_amount = GEN_INT (GET_MODE_BITSIZE (mode)
>  					- INTVAL (op1));
>  	      else
> -		other_amount
> -		  = simplify_gen_binary (MINUS, GET_MODE (op1),
> -					 GEN_INT (GET_MODE_PRECISION (mode)),
> -					 op1);
> +		{
> +		  other_amount
> +		    = simplify_gen_unary (NEG, GET_MODE (op1),
> +					  op1, GET_MODE (op1));
> +		  other_amount
> +		    = simplify_gen_binary (AND, GET_MODE (op1),
> +					   other_amount,
> +					   GEN_INT (GET_MODE_PRECISION (mode)
> +						    - 1));
> +		}
>  
>  	      shifted = force_reg (mode, shifted);
>  

causes an ICE in gcc.c-torture/execute/20020226-1.c, which we tried to
avoid by adding an "addneghi" pattern (which itself has a bug, hence me
investigating).

It seems like the code creates an (and (neg ...)) RTL pattern in
HImode.  If you try to do an SImode shift, that pattern (the shift
count portion) needs to be converted HI->SI to match the msp430's
shift pattern (it's an ABI call, must be SImode).  The code that does
that hits the "convert by parts" case and just copies the generated
RTL to a register, using emit_move, *without* checking to see if it's
valid.

The result is that the (and (neg ...)) RTL makes it all the way to
recog and fails to match anything.

Where would/should such validation take place?

Reproducible if you take out the "andneghi" pattern in msp430.md


Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]