}

		// Move all the stores to the root.
		for i := int64(0); i < n; i++ {
			v := a[i].store
			if v == root {
				v.Aux = cv.Type // widen store type
				v.Pos = pos
				v.SetArg(0, ptr)
				v.SetArg(1, cv)
				v.SetArg(2, mem)
			} else {
				clobber(v)
				v.Type = types.Types[types.TBOOL] // erase memory type
			}
		}
		return true
	}

	// sure that we don't end up doing O(n^2) work
	// for a chain of n copies.
	for v != w {
		x := v.Args[0]
		v.SetArg(0, w)
		v = x
	}
	return w
}

// copyelimValue ensures that no args of v are copies.
func copyelimValue(v *Value) {
	for i, a := range v.Args {
		if a.Op == OpCopy {
			v.SetArg(i, copySource(a))
		}
	}
}

// phielim eliminates redundant phi values from f.

			for i, a := range v.Args {
				if !a.Type.IsFlags() {
					continue
				}
				if a == flag {
					continue
				}
				// Recalculate a
				c := copyFlags(a, b)
				// Update v.
				v.SetArg(i, c)
				// Remember the most-recently computed flag value.
				flag = a
			}
			// Issue v.
			b.Values = append(b.Values, v)
			if v.clobbersFlags() {
				flag = nil
			}
			if v.Type.IsFlags() {

				if p.Controls[0] != a {
					continue
				}
				if e.i == 0 {
					if ct == nil {
						ct = f.ConstBool(f.Config.Types.Bool, true)
					}
					v.SetArg(i, ct)
				} else {
					if cf == nil {
						cf = f.ConstBool(f.Config.Types.Bool, false)
					}
					v.SetArg(i, cf)
				}
			}
		}
	}

	// Step 2: Redirect control flow around known branches.
	// p:
	//   ... goto b ...
	// b: <- p ...

	for _, b := range f.Blocks {
		for _, v := range b.Values {
			for i, a := range v.Args {
				if opcodeTable[a.Op].argLen == 0 {
					key := vkey{a.Op, keyFor(a), a.Aux, a.Type}
					if rv, ok := vals[key]; ok {
						v.SetArg(i, rv)
					}
				}
			}
		}
	}
}

// vkey is a type used to uniquely identify a zero arg value.
type vkey struct {
	op Op
	ai int64       // aux int
	ax Aux         // aux

		}
		// If the original block contained u = φ(u0, u1, ..., un) and
		// the current phi is
		//    v = φ(v0, v1, ..., u, ..., vk)
		// then the merged phi is
		//    v = φ(v0, v1, ..., u0, ..., vk, u1, ..., un)
		v.SetArg(i, u.Args[0])
		v.AddArgs(u.Args[1:]...)
	} else {
		// If the original block contained u = φ(u0, u1, ..., un) and
		// the current phi is
		//    v = φ(v0, v1, ...,  vi, ..., vk)

					continue // not a constant we can move around
				}
				if a.Block == b.Preds[i].b {
					continue // already in the right place
				}
				// Make a copy of a, put in predecessor block.
				v.SetArg(i, a.copyInto(b.Preds[i].b))
			}
		}
	}
}

// memState computes the memory state at the beginning and end of each block of
// the function. The memory state is represented by a value of mem type.

		for b, r := range newmemphis {
			fmt.Printf("after b=%s, rewrite=%s\n", b, r.String())
		}
	}

	// Apply collected rewrites.
	for _, r := range newmemphis {
		for _, rw := range r.rewrites {
			rw.v.SetArg(rw.i, r.after)
		}
	}

	// Rewrite backedges to include reschedule checks.
	for _, emc := range tofixBackedges {
		e := emc.e
		headerMemPhi := emc.m
		h := e.b
		i := e.i
		p := h.Preds[i]

						if w.Block == v.Block && w.Pos.Line() == v.Pos.Line() {
							v.Pos = v.Pos.WithIsStmt()
							w.Pos = w.Pos.WithNotStmt()
						} // TODO and if this fails?
					}
					v.SetArg(i, x)
					rewrites++
				}
			}
		}
		for i, v := range b.ControlValues() {
			if x := rewrite[v.ID]; x != nil {
				if v.Op == OpNilCheck {
					// nilcheck pass will remove the nil checks and log

		for i, v := range check.Args {
			if v != end {
				continue
			}

			check.SetArg(i, start)
			goto replacedEnd
		}
		panic(fmt.Sprintf("unreachable, ind: %v, start: %v, end: %v", ind, start, end))
	replacedEnd:

		for i, v := range ind.Args {
			if v != start {
				continue
			}

			ind.SetArg(i, end)
			goto replacedStart
		}