Re: PR 37363: simplify_plus_minus creates invalid constants

["Richard Guenther" <richard dot guenther at gmail dot com>]

On Mon, Nov 10, 2008 at 5:27 PM, Richard Sandiford
<rdsandiford@googlemail.com> wrote:
> PR 37363 is about the way simplify_plus_minus can create a
> (const (minus ...)) expression in cases where such expressions
> are not allowed.  This (const (minus ...)) code was originally
> added for PowerPC TOC references, but PowerPC now uses an
> UNSPEC-based representation instead.
>
> I think we've finally weaned all other targets off (const (minus ...))
> too, so there's no longer any need to create them in simplify_plus_minus.
>
> Bootstrapped & regression-tested on x86_64-linux-gnu.  Also tested
> by comparing the before and after assembly output for:
>
>  gcc.c-torture gcc.dg g++.dg
>
> on these targets:
>
>  powerpc-darwin powerpc64-darwin i386-darwin x86_64-darwin
>  powerpc-linux-gnu powerpc64-linux-gnu powerpc-ibm-aix5.3.0
>
> using the options "-O2 -fpic".  The output was the same.
> OK to install?

Ok.

Thanks,
Richard.

> Richard
>
>
> gcc/
>        PR rtl-optimization/37363
>        * simplify-rtx.c (simplify_plus_minus): Don't create (const (minus ...))
>        expresisons.
>
> Index: gcc/simplify-rtx.c
> ===================================================================
> --- gcc/simplify-rtx.c  2008-10-08 05:15:29.000000000 +0100
> +++ gcc/simplify-rtx.c  2008-10-08 19:53:13.000000000 +0100
> @@ -3678,24 +3678,6 @@ simplify_plus_minus (enum rtx_code code,
>      one CONST_INT, and the sort will have ensured that it is last
>      in the array and that any other constant will be next-to-last.  */
>
> -  if (GET_CODE (ops[n_ops - 1].op) == CONST_INT)
> -    i = n_ops - 2;
> -  else
> -    i = n_ops - 1;
> -
> -  if (i >= 1
> -      && ops[i].neg
> -      && !ops[i - 1].neg
> -      && CONSTANT_P (ops[i].op)
> -      && GET_CODE (ops[i].op) == GET_CODE (ops[i - 1].op))
> -    {
> -      ops[i - 1].op = gen_rtx_MINUS (mode, ops[i - 1].op, ops[i].op);
> -      ops[i - 1].op = gen_rtx_CONST (mode, ops[i - 1].op);
> -      if (i < n_ops - 1)
> -       ops[i] = ops[i + 1];
> -      n_ops--;
> -    }
> -
>   if (n_ops > 1
>       && GET_CODE (ops[n_ops - 1].op) == CONST_INT
>       && CONSTANT_P (ops[n_ops - 2].op))
>