Re: [middle-end PATCH] Constant fold {-1,-1} << 1 in simplify-rtx.cc

[Richard Biener <richard.guenther@gmail.com>]

On Fri, Jan 26, 2024 at 7:26 PM Roger Sayle <roger@nextmovesoftware.com> wrote:
>
>
> This patch addresses a missed optimization opportunity in the RTL
> optimization passes.  The function simplify_const_binary_operation
> will constant fold binary operators with two CONST_INT operands,
> and those with two CONST_VECTOR operands, but is missing compile-time
> evaluation of binary operators with a CONST_VECTOR and a CONST_INT,
> such as vector shifts and rotates.
>
> My first version of this patch didn't contain a switch statement to
> explicitly check for valid binary opcodes, which bootstrapped and
> regression tested fine, but by paranoia has got the better of me,
> so this version now checks that VEC_SELECT or some funky (future)
> rtx_code doesn't cause problems.
>
> This patch has been tested on x86_64-pc-linux-gnu with make bootstrap
> and make -k check, both with and without --target_board=unix{-m32}
> with no new failures.  Ok for mainline (in stage 1)?

OK.

Thanks,
Richard.

>
> 2024-01-26  Roger Sayle  <roger@nextmovesoftware.com>
>
> gcc/ChangeLog
>         * simplify-rtx.cc (simplify_const_binary_operation): Constant
>         fold binary operations where the LHS is CONST_VECTOR and the
>         RHS is CONST_INT (or CONST_DOUBLE) such as vector shifts.
>
>
> Thanks in advance,
> Roger
> --
>