}
}

// newPhiFor inserts a new Phi function into b,
// with all inputs set to v.
func newPhiFor(b *Block, v *Value) *Value {
	phiV := b.NewValue0(b.Pos, OpPhi, v.Type)

	for range b.Preds {
		phiV.AddArg(v)
	}
	return phiV
}

// rewriteNewPhis updates newphis[h] to record all places where the new phi function inserted

			phis = phis[:0]
			for i := len(b.Values) - 1; i >= 0; i-- {
				v := b.Values[i]
				live.remove(v.ID)
				if v.Op == OpPhi {
					// Save phi for later.
					// Note: its args might need a stack slot even though
					// the phi itself doesn't. So don't use needSlot.
					if !v.Type.IsMemory() && !v.Type.IsVoid() {
						phis = append(phis, v)
					}
					continue
				}

		for k := range localAddrs {
			delete(localAddrs, k)
		}
		stores = stores[:0]
		for _, v := range b.Values {
			if v.Op == OpPhi {
				// Ignore phis - they will always be first and can't be eliminated
				continue
			}
			if v.Type.IsMemory() {
				stores = append(stores, v)
				for _, a := range v.Args {
					if a.Block == b && a.Type.IsMemory() {

					// If no mem phi, take mem of any predecessor.
					mem = lastmem[b.Preds[0].b.ID]
				}
				for _, a := range v.Args {
					if a.Type.IsMemory() && a != mem {
						f.Fatalf("two live mems @ %s: %s and %s", v, mem, a)
					}
				}
				if v.Type.IsMemory() {
					mem = v
				}
			}
		}
	}

	// Check that after scheduling, phis are always first in the block.
	if f.scheduled {

		Bloc("b2",
			Valu("ptr2", OpAddr, ptrType, 0, nil, "sb"),
			Goto("checkPtr")),
		// both ptr1 and ptr2 are guaranteed non-nil here
		Bloc("checkPtr",
			Valu("phi", OpPhi, ptrType, 0, nil, "ptr1", "ptr2"),
			Valu("bool2", OpIsNonNil, c.config.Types.Bool, 0, nil, "phi"),
			If("bool2", "extra", "exit")),
		Bloc("extra",
			Goto("exit")),
		Bloc("exit",
			Exit("mem")))

	CheckFunc(fun.f)
	nilcheckelim(fun.f)

		b.Fatalf("inconsistent state for %v, num predecessors: %d, num phi args: %d", phi, n, numPhiArgs)
	}
	phi.Args[i].Uses--
	phi.Args[i] = phi.Args[n]
	phi.Args[n] = nil
	phi.Args = phi.Args[:n]
	phielimValue(phi)
}

// LackingPos indicates whether b is a block whose position should be inherited
// from its successors.  This is true if all the values within it have unreliable positions

				// Nil checks must come before loads from the same address.
				score[v.ID] = ScoreNilCheck
			case v.Op == OpPhi:
				// We want all the phis first.
				score[v.ID] = ScorePhi
			case v.Op == OpArgIntReg || v.Op == OpArgFloatReg:
				// In-register args must be scheduled as early as possible to ensure that they
				// are not stomped (similar to the closure pointer above).

	for _, use := range t.defUse[val] {
		if val == use {
			// Phi may refer to itself as uses, ignore them to avoid re-visiting phi
			// for performance reason
			continue
		}
		t.uses = append(t.uses, use)
	}
	for _, block := range t.defBlock[val] {
		if t.visitedBlock[block.ID] {
			t.propagate(block)
		}
	}
}

// meet meets all of phi arguments and computes result lattice

	// tuple selectors must be tightened to generators and de-duplicated before scheduling
	{"tighten tuple selectors", "schedule"},
	// remove critical edges before phi tighten, so that phi args get better placement
	{"critical", "phi tighten"},
	// don't layout blocks until critical edges have been removed
	{"critical", "layout"},
	// regalloc requires the removal of all critical edges
	{"critical", "regalloc"},

//   - the minimum bound
//   - the increment value
//   - the "next" value (SSA value that is Phi'd into the induction variable every loop)
//
// Currently, we detect induction variables that match (Phi min nxt),
// with nxt being (Add inc ind).
// If it can't parse the induction variable correctly, it returns (nil, nil, nil).
func parseIndVar(ind *Value) (min, inc, nxt *Value) {
	if ind.Op != OpPhi {
		return
	}