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From: "klaus.doldinger64 at googlemail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug rtl-optimization/109476] Missing optimization for 8bit/8bit
 multiplication / regression
Date: Wed, 12 Apr 2023 16:48:56 +0000
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X-Bugzilla-Component: rtl-optimization
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X-Bugzilla-Keywords: missed-optimization
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D109476

--- Comment #6 from Wilhelm M <klaus.doldinger64 at googlemail dot com> ---
The following "solution"

constexpr uint16_t mul(const uint8_t a, const uint16_t b) {
    const auto aa =3D std::bit_cast<std::array<uint8_t, 2>>(b);
    return aa[1] * a;
}

or=20

constexpr uint16_t mul(const uint8_t a, const uint16_t b) {
    uint8_t aa[2];
    std::memcpy(aa, &b, 2);
    return aa[1] * a;
}

gives optimal result ;-)=