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From: "jakub at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug tree-optimization/99079] Maybe a wrong code since
 r6-1462-g4ab1e111ef0669bb
Date: Fri, 12 Feb 2021 19:09:47 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D99079

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
  Attachment #50175|0                           |1
        is obsolete|                            |

--- Comment #3 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Created attachment 50176
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=3D50176&action=3Dedit
gcc11-pr99079.patch

Updated patch.  Actually, I think widening conversion from signed TREE_TYPE
(@1)
to signed type is fine too.
In the problematic case where @1 is negative (i.e. powerof2 << var which sh=
ifts
it into the sign bit, certainly valid at least in C++20), if we say have in=
t to
long long conversion and we know the dividend is non-negative, it would be
@0 % (long long) INT_MIN, i.e. @0 % -0x80000000LL and that can still be
expanded
as @0 & 0x7fffffffLL.=