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
				}

	}
}

// 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

					// reaching an op, but some ops can take
					// multiple pointers (e.g. NeqPtr, Phi etc.).
					// This is rare, so just propagate the first
					// value to keep things simple.
					used.Add(n)
					changed = true
				}
			}
		}
		if node == nil {
			return
		}
		if addr[v] == nil {
			// The address of an auto reaches this op.
			addr[v] = node
			changed = true
			return
		}

	work = append(work, bp{block: f.Entry})

	// map from value ID to known non-nil version of that value ID
	// (in the current dominator path being walked). This slice is updated by
	// walkStates to maintain the known non-nil values.
	// If there is extrinsic information about non-nil-ness, this map
	// points a value to itself. If a value is known non-nil because we
	// already did a nil check on it, it points to the nil check operation.

			If("bool2", "extra", "exit")),
		Bloc("extra",
			// prevent fuse from eliminating this block
			Valu("store", OpStore, types.TypeMem, 0, ptrType, "ptr1", "nilptr", "mem"),
			Goto("exit")),
		Bloc("exit",
			Valu("phi", OpPhi, types.TypeMem, 0, nil, "mem", "store"),
			Exit("phi")))

	CheckFunc(fun.f)
	// we need the opt here to rewrite the user nilcheck
	opt(fun.f)
	nilcheckelim(fun.f)

				// of flag values.
				score[v.ID] = ScoreReadFlags
			case v.isFlagOp():
				// Schedule flag register generation as late as possible.
				// This makes sure that we only have one live flags
				// value at a time.
				// Note that this case is after the case above, so values
				// which both read and generate flags are given ScoreReadFlags.
				score[v.ID] = ScoreFlags
			default:

					// 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 {

		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

	// original value, this behavior is undesired, because the lattice of values
	// may change multiple times, once it was rewritten, we lose the opportunity
	// to change it permanently, which can lead to errors. For example, We cannot
	// change its value immediately after visiting Phi, because some of its input
	// edges may still not be visited at this moment.

 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0