fix overflow in example code.

[0x00-pl]

Summary

fix overflow in example code in 'llvm/lib/Transforms/Scalar/LoopInterchange.cpp'
A[j-1][i-1]+k; is access memory before A when i and j is 0.

llvm/lib/Transforms/Scalar/LoopInterchange.cpp

           if (!SE->isSCEVable(GEP->getOperand(i)->getType()))
             continue;
 
           const SCEV *OperandVal = SE->getSCEV(GEP->getOperand(i));
           const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(OperandVal);
           if (!AR)
             continue;
 
           // If we find the inner induction after an outer induction e.g.
-          // for(int i=0;i<N;i++)
-          //   for(int j=0;j<N;j++)
+          // for(int i=1;i<N;i++)
+          //   for(int j=1;j<N;j++)
           //     A[i][j] = A[i-1][j-1]+k;
           // then it is a good order.
           if (AR->getLoop() == InnerLoop) {
             // We found an InnerLoop induction after OuterLoop induction. It is
             // a good order.
             FoundInnerInduction = true;
             if (FoundOuterInduction) {
               GoodOrder++;
               break;
             }
           }
           // If we find the outer induction after an inner induction e.g.
-          // for(int i=0;i<N;i++)
-          //   for(int j=0;j<N;j++)
+          // for(int i=1;i<N;i++)
+          //   for(int j=1;j<N;j++)
           //     A[j][i] = A[j-1][i-1]+k;
           // then it is a bad order.
           if (AR->getLoop() == OuterLoop) {
             // We found an OuterLoop induction after InnerLoop induction. It is
             // a bad order.
             FoundOuterInduction = true;
             if (FoundInnerInduction) {
               BadOrder++;
               break;