[LLVMbugs] [Bug 22360] New: ATS exposes -O2 bug

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=22360

            Bug ID: 22360
           Summary: ATS exposes -O2 bug
           Product: clang
           Version: 3.5
          Hardware: PC
                OS: All
            Status: NEW
          Severity: normal
          Priority: P
         Component: -New Bugs
          Assignee: unassignedclangbugs at nondot.org
          Reporter: garious at gmail.com
                CC: llvmbugs at cs.uiuc.edu
    Classification: Unclassified

The ATS community is having trouble with clang 3.5.  Moving from
-O1 to -O2 triggers a crash on startup in the clang-generated
executable.  Hongwei Xi rebuilt with -fsanitize=undefined and
-fsanitize=address and has verified the code has no dependencies on undefined
behavior.
Their workaround is to add a dummy level of indirection to prevent the
[unknown] broken optimization from firing.

https://github.com/githwxi/ATS-Postiats/commit/5e17db4badf58b404598e8b3ae4a666b8b0e889c

Looks like a bug on the LLVM side.  He says it worked with clang 3.2,
but breaks on 3.4 and 3.5 (didn't try 3.3).

Steps to reproduce, build ATS2 with clang 3.5:

    http://www.ats-lang.org/Downloads.html

Ensure your source code does not include the previously-mentioned workaround:

    5e17db4badf58b404598e8b3ae4a666b8b0e889c

Run 'patopt' on the command-line.  If the the bug is present, you should see a
crash on startup.

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