go/src/cmd/compile/internal/ssa/tuple.go

// tightenTupleSelectors ensures that tuple selectors (Select0, Select1,
// and SelectN ops) are in the same block as their tuple generator. The
// function also ensures that there are no duplicate tuple selectors.
// These properties are expected by the scheduler but may not have
// been maintained by the optimization pipeline up to this point.
//
// See issues 16741 and 39472.
func tightenTupleSelectors(f *Func) { … }