[LLVMbugs] [Bug 2253] New: getTripCount() of a Loop does not seem to give the correct trip count

[bugzilla-daemon at cs.uiuc.edu]

http://llvm.org/bugs/show_bug.cgi?id=2253

           Summary: getTripCount() of a Loop does not seem to give the
                    correct trip count
           Product: new-bugs
           Version: unspecified
          Platform: PC
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P2
         Component: new bugs
        AssignedTo: unassignedbugs at nondot.org
        ReportedBy: prakash.prabhu at gmail.com
                CC: llvmbugs at cs.uiuc.edu


Hi,

I am trying to add a new loop pass in which I making a call to get the trip
count of the loop using

Value *TripCountValue = L->getTripCount()

However I am always getting NULL for TripCountValue (confirmed through gdb). I
am running this pass after the canonicalization of induction variables:

opt --debug-pass=Structure -stats -indvars -loop-rotate -my-loop-pass < main.bc
> main.unroll.s
Pass Arguments:  -domtree -loops -scalar-evolution -loopsimplify -domfrontier
-scalar-evolution -lcssa -indvars -loop-rotate -domfrontier -scalar-evolution
-lcssa -my-loop-pass -preverify -domtree -verify
Target Data Layout
  ModulePass Manager
    FunctionPass Manager
      Dominator Tree Construction
      Natural Loop Construction
      Scalar Evolution Analysis
--      Scalar Evolution Analysis
      Canonicalize natural loops
      Dominance Frontier Construction
      Scalar Evolution Analysis
      Loop Pass Manager
        Loop-Closed SSA Form Pass
        Canonicalize Induction Variables
--        Canonicalize Induction Variables
        Rotate Loops
--        Loop-Closed SSA Form Pass
--        Rotate Loops
--      Dominance Frontier Construction
--      Scalar Evolution Analysis
      Dominance Frontier Construction
      Scalar Evolution Analysis
      Loop Pass Manager
        Loop-Closed SSA Form Pass
        <My Loop Pass>
--        <My Loop Pass>
--        Loop-Closed SSA Form Pass
--      Natural Loop Construction
--      Canonicalize natural loops
--      Dominance Frontier Construction
--      Dominator Tree Construction
--      Scalar Evolution Analysis
      Preliminary module verification
      Dominator Tree Construction
      Module Verifier
--      Preliminary module verification
--      Dominator Tree Construction
--      Module Verifier
    Bitcode Writer
--    Bitcode Writer

I have two loops in my source program which have statically-determinable
bounds:

for (i=1; i < 99999; i++)
{
....
}

Is there anything else I should be doing before invoking the getTripCount()
method ?

thanks,
Prakash


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