[llvm-bugs] [Bug 43493] New: Infinite loop in MemorySSAUpdater::applyInsertUpdates during loop-rotate

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=43493

            Bug ID: 43493
           Summary: Infinite loop in MemorySSAUpdater::applyInsertUpdates
                    during loop-rotate
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Scalar Optimizations
          Assignee: unassignedbugs at nondot.org
          Reporter: bjorn.a.pettersson at ericsson.com
                CC: llvm-bugs at lists.llvm.org

Created attachment 22598
  --> https://bugs.llvm.org/attachment.cgi?id=22598&action=edit
reduced reproducer

Looks like we get stuck in an infinite loop in
MemorySSAUpdater::applyInsertUpdates when running

  opt -enable-mssa-loop-dependency=true -loop-rotate -S -o - mssa5.ll

Problem is not seen with -enable-mssa-loop-dependency=false.

Reproduced with trunk at llvm-svn: 373150

The attached mssa5.ll is a quite heavily reduced test case (still in loop
simplify form). Original C test case was generated by csmith.

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