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

// combine copyelim and phielim into a single pass.
// copyelim removes all uses of OpCopy values from f.
// A subsequent deadcode pass is needed to actually remove the copies.
func copyelim(f *Func) { … }

// copySource returns the (non-copy) op which is the
// ultimate source of v.  v must be a copy op.
func copySource(v *Value) *Value { … }

// copyelimValue ensures that no args of v are copies.
func copyelimValue(v *Value) { … }

// phielim eliminates redundant phi values from f.
// A phi is redundant if its arguments are all equal. For
// purposes of counting, ignore the phi itself. Both of
// these phis are redundant:
//
//	v = phi(x,x,x)
//	v = phi(x,v,x,v)
//
// We repeat this process to also catch situations like:
//
//	v = phi(x, phi(x, x), phi(x, v))
//
// TODO: Can we also simplify cases like:
//
//	v = phi(v, w, x)
//	w = phi(v, w, x)
//
// and would that be useful?
func phielim(f *Func) { … }

// phielimValue tries to convert the phi v to a copy.
func phielimValue(v *Value) bool { … }