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Subject: [Bug rtl-optimization/66552] Missed optimization when shift amount
 is result of signed modulus
Date: Mon, 19 Oct 2020 09:27:31 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D66552

--- Comment #15 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Jiu Fu Guo <guojiufu@gcc.gnu.org>:

https://gcc.gnu.org/g:222f312a773157f53396ba4cb287deb07f84cc34

commit r11-4033-g222f312a773157f53396ba4cb287deb07f84cc34
Author: guojiufu <guojiufu@linux.ibm.com>
Date:   Mon Oct 19 13:48:19 2020 +0800

    [PATCH] fold x << (n % C) to x << (n & C-1) if C meets power2

    This patch fixes PR66552 which is also as:
    https://gcc.gnu.org/pipermail/gcc-patches/2020-February/540930.html
    which requests to optimizes (x shift (n mod C)) to
    (x shift (n bit_and (C - 1))) when C is a constant and power of two.

    gcc/ChangeLog
    2020-10-19  Li Jia He  <helijia@gcc.gnu.org>

            PR tree-optimization/66552
            * match.pd (x << (n % C) -> x << (n & C-1)): New simplification.

    gcc/testsuite/ChangeLog
    2020-10-19  Li Jia He  <helijia@gcc.gnu.org>

            PR tree-optimization/66552
            * gcc.dg/pr66552.c: New testcase.=