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

// phiopt eliminates boolean Phis based on the previous if.
//
// Main use case is to transform:
//
//	x := false
//	if b {
//	  x = true
//	}
//
// into x = b.
//
// In SSA code this appears as
//
//	b0
//	  If b -> b1 b2
//	b1
//	  Plain -> b2
//	b2
//	  x = (OpPhi (ConstBool [true]) (ConstBool [false]))
//
// In this case we can replace x with a copy of b.
func phiopt(f *Func) { … }

func phioptint(v *Value, b0 *Block, reverse int) { … }

// b is the If block giving the boolean value.
// v is the phi value v = (OpPhi (ConstBool [true]) (ConstBool [false])).
// reverse is the predecessor from which the truth value comes.
func convertPhi(b *Block, v *Value, reverse int) { … }