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From: "jakub at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug tree-optimization/98856] [11 Regression] botan AES-128/XTS is
 slower by ~17% since r11-6649-g285fa338b06b804e72997c4d876ecf08a9c083af
Date: Fri, 05 Feb 2021 11:52:53 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D98856

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jakub at gcc dot gnu.org

--- Comment #9 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
For arithmetic >> (element_precision - 1) one can just use
{,v}pxor + {,v}pcmpgtq, as in instead of return vec >> 63; do return vec < =
0;
(in C++-ish way), aka VEC_COND_EXPR vec < 0, { all ones }, { 0 }
For other arithmetic shifts by scalar constant, perhaps one can replace
return vec >> 17; with return (vectype) ((uvectype) vec >> 17) | ((vec < 0)=
 <<
(64 - 17));
- it will actually work even for non-constant scalar shift amounts because
{,v}psllq treats shift counts > 63 as 0.=