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From: "segher at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug middle-end/90323] powerpc should convert equivalent sequences
 to vec_sel()
Date: Thu, 08 Apr 2021 20:49:41 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D90323

--- Comment #10 from Segher Boessenkool <segher at gcc dot gnu.org> ---
You cannot fix a simplify-rtx problem in much earlier passes!  It may be
useful of course (I have no idea, I don't know gimple well enough), but
it is no solution to the problem at all.  The xor/and/xor thing should be
simplified to something proper.

((A^B)&C)^A =3D (A&~C)^(B&C) =3D (A&~C)|(B&C)

This should already be done by the expand pass.  At gimple level the logical
complement is counted as an operation, making the contorted xor/and/xor form
the best form to use, but in a system that considers more than just operati=
on
counts (like in RTL) this is not the best form at all.  But, anyway, RTL
simplification should be able to do this.

Similar problems happen all over the place, fwiw -- see the various rl* tes=
ts
for rs6000, for example.=