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From: "aldyh at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug ipa/110753] [14 Regression] ICE in meet_with_1, at
 ipa-cp.cc:1057
Date: Thu, 03 Aug 2023 09:10:31 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D110753

Aldy Hernandez <aldyh at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |aldyh at gcc dot gnu.org
           Assignee|unassigned at gcc dot gnu.org      |aldyh at gcc dot gn=
u.org

--- Comment #3 from Aldy Hernandez <aldyh at gcc dot gnu.org> ---
The intersection of two mask/value pairs is being pessimized incorrectly.

MASK 0x0 VALUE 0x1 (value is known to be 1)
MASK 0xfffffffffffffffc VALUE 0x0 (low 2 bits are known to be 1, everything
else is unknown).

irange_bitmask::intersect() is intersecting these to:

MASK 0xffffffffffffffff VALUE 0x0

(i.e. totally unknown value).

This is causing union_bitmask() to return a change when none actually occur=
red,
because we end up losing the bitmask.

Mine.=