[llvm-bugs] [Bug 29048] New: JumpThreading.cpp segfault in ThreadEdge function

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https://llvm.org/bugs/show_bug.cgi?id=29048

            Bug ID: 29048
           Summary: JumpThreading.cpp segfault in ThreadEdge function
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: Scalar Optimizations
          Assignee: unassignedbugs at nondot.org
          Reporter: davidnoursi at gmail.com
                CC: llvm-bugs at lists.llvm.org
    Classification: Unclassified

We have been modifying LLVM for use to compile our C-like language, and in the
process of debugging some newly overloaded intrinsics we experienced segfaults
in JumpThreading.cpp. Although we never quite determined what in the IR caused
this segfault, we found the bug in the code and corrected it; my reference is
the code at http://llvm.org/docs/doxygen/html/JumpThreading_8cpp_source.html.

Our correction involved the declaration of SSAUpdater SSAUpdate on line 1535,
which is not initialized until after a conditional "continue" statement on line
1553. We found, with print statements, that the segfault occurred from the
SSAUpdater destructor at the very end of ThreadEdge. We eliminated the error by
moving the declaration from line 1535 to an else statement on lines 1554-1567.

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