Dead Store Elimination

Dead store elimination is a compiler optimization that removes assignments to memory locations that are never subsequently read before being overwritten. The analysis is deceptively simple in concept — identify a store whose value is killed by a later store to the same location — but its implementation depends on precise alias analysis to prove that no intervening code reads the location through a different name. Without alias information, the compiler must conservatively assume that every pointer may alias every location, and the optimization collapses into a vacuous check that never fires.

Dead store elimination is the canary in the coal mine for alias analysis precision. When you see a compiler failing to remove an obviously redundant assignment, the problem is rarely in the dead-store pass itself; it is in the alias analysis that could not prove the store was truly dead.