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Subject: [Bug c/102245] [12 Regression] false  int-in-bool-context warning
 with shift
Date: Fri, 17 Sep 2021 14:58:40 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D102245

--- Comment #9 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Roger Sayle <sayle@gcc.gnu.org>:

https://gcc.gnu.org/g:2578a3870ef849dc77e98796600181b64ae4fd61

commit r12-3623-g2578a3870ef849dc77e98796600181b64ae4fd61
Author: Roger Sayle <roger@nextmovesoftware.com>
Date:   Fri Sep 17 15:57:34 2021 +0100

    PR c/102245: Disable sign-changing optimization for shifts by zero.

    Respecting Jakub's suggestion that it may be better to warn-on-valid for
    "if (x << 0)" as the author might have intended "if (x < 0)" [which will
    also warn when x is _Bool], the simplest way to resolve this regression
    is to disable the recently added fold transformation for shifts by zero;
    these will be optimized later (elsewhere).  Guarding against integer_ze=
rop
    is the simplest of three alternatives; the second being to only apply
    this transformation to GIMPLE and not GENERIC, and the third (potential=
ly)
    being to explicitly handle shifts by zero here, with an (if cond then
else),
    optimizing the expression to a convert, but awkwardly duplicating a
    more general transformation earlier in match.pd's shift simplifications.

    2021-09-17  Roger Sayle  <roger@nextmovesoftware.com>

    gcc/ChangeLog
            PR c/102245
            * match.pd (shift optimizations): Disable recent sign-changing
            optimization for shifts by zero, these will be folded later.

    gcc/testsuite/ChangeLog
            PR c/102245
            * gcc.dg/Wint-in-bool-context-4.c: New test case.=