[LLVMbugs] [Bug 5837] New: loop rotate (really ssaupdate) inserts many duplicate phi nodes

[bugzilla-daemon at cs.uiuc.edu]

http://llvm.org/bugs/show_bug.cgi?id=5837

           Summary: loop rotate (really ssaupdate) inserts many duplicate
                    phi nodes
           Product: libraries
           Version: 1.0
          Platform: PC
        OS/Version: All
            Status: NEW
          Keywords: code-quality
          Severity: normal
          Priority: P2
         Component: Transformation Utilities
        AssignedTo: unassignedbugs at nondot.org
        ReportedBy: clattner at apple.com
                CC: llvmbugs at cs.uiuc.edu


Loop rotate transforms this input testcase with no phi nodes to this:

for.body:                                         ; preds = %bb.nph, %for.cond
  %j.05 = phi i64 [ 1, %bb.nph ], [ %j.0, %for.cond ] ; <i64> [#uses=1]
  %j.04 = phi i64 [ 1, %bb.nph ], [ %j.0, %for.cond ] ; <i64> [#uses=1]
  %j.03 = phi i64 [ 1, %bb.nph ], [ %j.0, %for.cond ] ; <i64> [#uses=1]
  %j.02 = phi i64 [ 1, %bb.nph ], [ %j.0, %for.cond ] ; <i64> [#uses=1]
  %arrayidx = getelementptr inbounds double* %G, i64 %j.05 ; <double*>
[#uses=1]
  %tmp3 = load double* %arrayidx                  ; <double> [#uses=1]
  %sub = sub i64 %j.04, 1                         ; <i64> [#uses=1]
  %arrayidx6 = getelementptr inbounds double* %G, i64 %sub ; <double*>
[#uses=1]

This can't be good.


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