On Wed, 25 Jan 2017, Yuri Gribov wrote:
> Hi all,
>
> This fixes inefficient bitfield code reported in
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67328
>
> Bootstrapped and regtested on x86_64.
>
> Ok for trunk?
This isn't a regression fix and thus not appropriate at this stage.
Some comments on the patch:
+/* A & (2**N - 1) <= 2**K - 1 -> ~(A & (2**N - 2**K)
+ A & (2**N - 1) < 2**K -> ~(A & (2**N - 2**K)
+ A & (2**N - 1) >= 2**K -> A & (2**N - 2**K)
+ A & (2**N - 1) > 2**K - 1 -> A & (2**N - 2**K)
+ */
you miss the != 0/== 0 in the result (and the ~ is redundant then).
Note that A & (2**N - 1) >= 2**K should already have been simplified
to A & (2**N - 1) > 2**K - 1 (we canonicalize to smaller constants).
+ (if (TYPE_UNSIGNED (TREE_TYPE (@0)) && tree_fits_uhwi_p (@2) &&
tree_fits_uhwi_p (@3))
+ (with
+ {
I think you should restrict this to INTEGRAL_TYPE_P types.
Please use wide-ints so you do not restrict yourself to fits_uhwi_p
values.
Thanks,
Richard.
