On 10/02/2017 01:35 PM, Segher Boessenkool wrote:
> If we have (X&C1)|C2 simplify_binary_operation_1 makes C1 as small as
> possible. This makes worse code in common cases like when the AND with
> C1 is from a zero-extension. This patch fixes it by removing this
> transformation (twice).
>
> I tested this on 31 targets, also some variations that do the
> transformation only for some conditions (like, do not do it if the
> resulting constant looks "worse", e.g. has more stretches of ones).
> 22 of those targets show no difference; 8 are best with this patch
> variant (never do the transformation); and 64-bit hppa is not best,
> but the difference is only four insns in a million.
>
> Bootstrapped and tested on powerpc64-linux {-m32,-m64}. Is this okay
> for trunk? And backports?
>
>
> Segher
>
>
> 2017-10-02 Segher Boessenkool <seg...@kernel.crashing.org>
>
> PR rtl-optimization/77729
> * simplify-rtx.c (simplify_binary_operation_1): Delete the (X&C1)|C2
> to (X&(C1&~C2))|C2 transformations.
OK for the trunk. I'm not sure if the BZ in question qualifies this
patch for backporting though. Release managers have the final say on
the backport question.
And FWIW, the PA being an outlier on an optimization question should
never IMHO be a blocker :-)
jeff
