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From: "glisse at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/95926] Failure to optimize xor pattern when
 using temporary variable
Date: Sat, 27 Jun 2020 11:59:23 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D95926

--- Comment #1 from Marc Glisse <glisse at gcc dot gnu.org> ---
It is different to gcc because in the first case, tmp is used twice, while =
in
the second case, each a&b is only used once, and gcc only transforms (a&b)^=
b to
b&~a if this is the only use of a&b. Yes, this heuristic often backfires, b=
ut
as long as we consider &~ as 2 operations, not restricting the transformati=
on
could generate worse code in some cases.=