Re: [patch tree-ssa-math-opts]: Improve bswap detection

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

On Mon, Jun 27, 2011 at 10:06 AM, Kai Tietz <ktietz@redhat.com> wrote:
> Hello,
>
> this patch improves the bswap (32/64) detection and fixes an issue about shifted bit values out of type-size precision.
>
> ChangeLog
>
> 2011-06-27  Kai Tietz  <ktietz@redhat.com>
>
>        * tree-ssa-math-opts.c (do_shift_rotate): Zero bits
>        out of type precision after operation.
>        (find_bswap): Take for limit value the integer auto-
>        promotion into account.
>
> ChangeLog
>
> 2011-06-27  Kai Tietz  <ktietz@redhat.com>
>
>        * gcc.dg/optimize-bswapdi-2.c: New test.
>
> Bootstrapped and regression tested for x86_64-pc-linux-gnu. Ok for apply?

The do_shift_rotate hunk is ok.  Where did you get the testcase from?
I can easily construct testcases that go via an intermediate SImode step
and the still won't be recongized.  Thus, is the testcase practically
relevant?  If so we should add 1 + log2 (byte-size) instead of 3 to also
cover the SImode -> HImode intermediate case.

Thanks,
Richard.

> Regards,
> Kai
>