[LazyValueInfo] Make LVILatticeVal intersect method take arguments by reference so we don't copy ConstantRanges unless we need to.

llvm-svn: 304990

llvm/lib/Analysis/LazyValueInfo.cpp

@@ -302,7 +302,7 @@ static bool hasSingleValue(const LVILatticeVal &Val) {
 ///   contradictory.  If this happens, we return some valid lattice value so as
 ///   not confuse the rest of LVI.  Ideally, we'd always return Undefined, but
 ///   we do not make this guarantee.  TODO: This would be a useful enhancement.
-static LVILatticeVal intersect(LVILatticeVal A, LVILatticeVal B) {
+static LVILatticeVal intersect(const LVILatticeVal &A, const LVILatticeVal &B) {
   // Undefined is the strongest state.  It means the value is known to be along
   // an unreachable path.
   if (A.isUndefined())