- return ConstantRange(APInt(DstTySize,0), APInt(DstTySize,1).shl(SrcTySize));
+ APInt LowerExt(DstTySize, 0);
+ if (!Upper) // special case: [X, 0) -- not really wrapping around
+ LowerExt = Lower.zext(DstTySize);
+ return ConstantRange(LowerExt, APInt::getOneBitSet(DstTySize, SrcTySize));
+ }