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From: "pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/105119] the division in x / (1 << y) is optimized
 away when x has unsigned type, but not when it's signed
Date: Mon, 28 Nov 2022 20:09:45 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D105119

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2022-11-28
     Ever confirmed|0                           |1

--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
The unsigned case is handled with r8-1550-g71f82be94fad15 .

The comment in match.pd is now:
/* (A / (1 << B)) -> (A >> B).
   Only for unsigned A.  For signed A, this would not preserve rounding
   toward zero.
   For example: (-1 / ( 1 << B)) !=3D  -1 >> B.
   Also also [handle] widening conversions, like:
   (A / (unsigned long long) (1U << B)) -> (A >> B)
   or
   (A / (unsigned long long) (1 << B)) -> (A >> B).
   If the left shift is signed, it can be done only if the upper bits
   of A starting from shift's type sign bit are zero, as
   (unsigned long long) (1 << 31) is -2147483648ULL, not 2147483648ULL,
   so it is valid only if A >> 31 is zero.  */

Confirmed.=