Be more careful with degenerate blocks in maintainOperandStack
Be more careful with degenerate blocks in maintainOperandStack

BruceForstall/llilc,adiaaida/llilc,dkorolev/llilc,manu-silicon/llilc,BruceForstall/llilc,marksantos/llilc,JosephTremoulet/llilc,swaroop-sridhar/llilc,adiaaida/llilc,manu-silicon/llilc,JosephTremoulet/llilc,dkorolev/llilc,marksantos/llilc,AndyAyersMS/llilc,manu-silicon/llilc,BruceForstall/llilc,JosephTremoulet/llilc,dotnet/llilc,russellhadley/llilc,russellhadley/llilc,AndyAyersMS/llilc,marksantos/llilc,adiaaida/llilc,kyulee1/llilcjit,russellhadley/llilc,kyulee1/llilcjit,kyulee1/llilcjit,swaroop-sridhar/llilc,AndyAyersMS/llilc,dotnet/llilc,swaroop-sridhar/llilc,dotnet/llilc,dkorolev/llilc