[LLVMbugs] [Bug 8746] New: Scalar evolution loops forever (after 2h I got impatient :) on input file

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=8746

           Summary: Scalar evolution loops forever (after 2h I got
                    impatient :) on input file
           Product: tools
           Version: trunk
          Platform: PC
        OS/Version: All
            Status: NEW
          Severity: normal
          Priority: P
         Component: opt
        AssignedTo: unassignedbugs at nondot.org
        ReportedBy: arnold.schwaighofer at gmail.com
                CC: llvmbugs at cs.uiuc.edu


Running 'opt -O2 IndVarFailure.red.ll' will loop probably forever (if one can
ever make that claim).

The C-file that generated this IR is also attached: IndVarFailure.red.c. This C
file is the result of unrolling the HPC Challenge random access benchmark 16
times.

I tried to figure out what is going and could track it down to the scalar
evolution analysis that runs before 'indvars'. I tried to debug it, but I got
lost in deep recursions of scalar evolution.

I have also attached the IR at that point: 'opt -indvars indvarsbug.2.bp.ll'
will exhibit the same behavior.

Last tested with revision 121016.

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