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

// zcse does an initial pass of common-subexpression elimination on the
// function for values with zero arguments to allow the more expensive cse
// to begin with a reduced number of values. Values are just relinked,
// nothing is deleted. A subsequent deadcode pass is required to actually
// remove duplicate expressions.
func zcse(f *Func) { … }

type vkey …

// keyFor returns the AuxInt portion of a  key structure uniquely identifying a
// zero arg value for the supported ops.
func keyFor(v *Value) int64 { … }