if possibleConst(arg) && possibleConst(val) {
					if _, exist := t.defUse[arg]; !exist {
						t.defUse[arg] = make([]*Value, 0, arg.Uses)
					}
					t.defUse[arg] = append(t.defUse[arg], val)
				}
			}
		}
		for _, ctl := range block.ControlValues() {
			// for control values that can become constants, find their use blocks
			if possibleConst(ctl) {