On Mon, Aug 23, 2021 at 01:25:13AM +0100, Roger Sayle wrote:
> This patch has been tested on x86_64-pc-linux-gnu with "make bootstrap"
> and "make -k check" with no new failures. Ok for mainline?
>
>
> 2021-08-23 Roger Sayle <ro...@nextmovesoftware.com>
>
> gcc/ChangeLog
> * match.pd (shift transformations): Change the sign of an
> LSHIFT_EXPR if it reduces the number of explicit conversions.
This broke bootstrap on i686-linux, where it incorrectly simplifies
a cast from LSHIFT_EXPR with integral type to pointer type of the
same precision into LSHIFT_EXPR performed on the pointer type,
which is invalid IL.
> diff --git a/gcc/match.pd b/gcc/match.pd
> index 0fcfd0e..978a1b0 100644
> --- a/gcc/match.pd
> +++ b/gcc/match.pd
> @@ -3385,6 +3385,15 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
> (if (integer_zerop (@2) || integer_all_onesp (@2))
> (cmp @0 @2)))))
>
> +/* Both signed and unsigned lshift produce the same result, so use
> + the form that minimizes the number of conversions. */
> +(simplify
> + (convert (lshift:s@0 (convert:s@1 @2) INTEGER_CST@3))
> + (if (tree_nop_conversion_p (type, TREE_TYPE (@0))
I think you want
&& INTEGRAL_TYPE_P (TREE_TYPE (@1))
here as well.
> + && INTEGRAL_TYPE_P (TREE_TYPE (@2))
> + && TYPE_PRECISION (TREE_TYPE (@2)) <= TYPE_PRECISION (type))
> + (lshift (convert @2) @3)))
> +
Jakub
