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From: "pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/103325] New: 1 << -1 is never reduced to a constant during gimple
Date: Fri, 19 Nov 2021 01:35:51 +0000	[thread overview]
Message-ID: <bug-103325-4@http.gcc.gnu.org/bugzilla/> (raw)

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103325

            Bug ID: 103325
           Summary: 1 << -1 is never reduced to a constant during gimple
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: enhancement
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: pinskia at gcc dot gnu.org
  Target Milestone: ---

Take:
int main() {
  return 1 >> (-1);
}

GCC is the only compiler I have tried (MSVC, ICC and clang/LLVM) which does not
remove the shift.
Yes this is undefined behavior but really I think it is best to reduce to
something rather than keeping around the shift. Even converting it to
__builtin_unreachable will be ok in my book.

             reply	other threads:[~2021-11-19  1:35 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-11-19  1:35 pinskia at gcc dot gnu.org [this message]
2021-11-19  1:36 ` [Bug tree-optimization/103325] " pinskia at gcc dot gnu.org
2021-11-19  7:48 ` rguenth at gcc dot gnu.org
2021-11-19 12:14 ` pinskia at gcc dot gnu.org
2023-05-28  4:21 ` pinskia at gcc dot gnu.org

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