return
	}
	ln.calculateDepths()
	b2l := ln.b2l
	for _, b := range ln.po {
		l := b2l[b.ID]
		if l != nil && len(b.Succs) == 2 {
			sl := b2l[b.Succs[0].b.ID]
			if recordIfExit(l, sl, b.Succs[0].b) {
				continue
			}
			sl = b2l[b.Succs[1].b.ID]
			if recordIfExit(l, sl, b.Succs[1].b) {
				continue
			}
		}
	}
	ln.initializedExits = true
}

		return false
	}
	yes, no := b.Succs[0].Block(), b.Succs[1].Block()
	if !isLeafPlain(yes) || len(yes.Values) > 1 || !canSpeculativelyExecute(yes) {
		return false
	}
	if !isLeafPlain(no) || len(no.Values) > 1 || !canSpeculativelyExecute(no) {
		return false
	}
	if b.Succs[0].Block().Succs[0].Block() != b.Succs[1].Block().Succs[0].Block() {
		return false
	}

			}
		case BlockRetJmp:
			if len(b.Succs) != 0 {
				f.Fatalf("retjmp block %s len(Succs)==%d, want 0", b, len(b.Succs))
			}
			if b.NumControls() != 1 {
				f.Fatalf("retjmp block %s has nil control", b)
			}
			if !b.Controls[0].Type.IsMemory() {
				f.Fatalf("retjmp block %s has non-memory control value %s", b, b.Controls[0].LongString())
			}
		case BlockPlain:
			if len(b.Succs) != 1 {

				return false
			}
			for i := range fb.Values {
				if !checkVal(fb.Values[i], gb.Values[i]) {
					return false
				}
			}
			if len(fb.Succs) != len(gb.Succs) {
				return false
			}
			for i := range fb.Succs {
				if !checkBlk(fb.Succs[i].b, gb.Succs[i].b) {
					return false
				}
			}
			if len(fb.Preds) != len(gb.Preds) {
				return false
			}
			for i := range fb.Preds {

	// In these cases, we can reconstruct what the value
	// of any phi in b must be in the successor blocks.

	if len(t.Preds) == 1 && len(t.Succs) == 1 &&
		len(u.Preds) == 1 && len(u.Succs) == 1 &&
		t.Succs[0].b == u.Succs[0].b && len(t.Succs[0].b.Preds) == 2 {
		// p   q
		//  \ /
		//   b
		//  / \
		// t   u
		//  \ /
		//   m
		//

		Stmt:  stmt,
	}
	block.Succs = block.succs2[:0]
	g.Blocks = append(g.Blocks, block)
	return block
}

func (b *builder) add(n ast.Node) {
	b.current.Nodes = append(b.current.Nodes, n)
}

// jump adds an edge from the current block to the target block,
// and sets b.current to nil.
func (b *builder) jump(target *Block) {
	b.current.Succs = append(b.current.Succs, target)
	b.current = nil
}

func (b *Block) removeSucc(i int) {
	n := len(b.Succs) - 1
	if i != n {
		e := b.Succs[n]
		b.Succs[i] = e
		// Update the other end of the edge we moved.
		e.b.Preds[e.i].i = i
	}
	b.Succs[n] = Edge{}
	b.Succs = b.Succs[:n]
	b.Func.invalidateCFG()
}

func (b *Block) swapSuccessors() {
	if len(b.Succs) != 2 {
		b.Fatalf("swapSuccessors with len(Succs)=%d", len(b.Succs))
	}
	e0 := b.Succs[0]

	case ssa.BlockPlain:
		if next != b.Succs[0].Block() {
			s.Br(obj.AJMP, b.Succs[0].Block())
		}

	case ssa.BlockIf:
		switch next {
		case b.Succs[0].Block():
			// if false, jump to b.Succs[1]
			getValue32(s, b.Controls[0])
			s.Prog(wasm.AI32Eqz)
			s.Prog(wasm.AIf)
			s.Br(obj.AJMP, b.Succs[1].Block())
			s.Prog(wasm.AEnd)
		case b.Succs[1].Block():
			// if true, jump to b.Succs[0]

	// Check if newsuccs is the same set as succs.
	succs := s[data.controls:]
	newsuccs := t[outdata.controls:]
	m := map[string]bool{}
	for _, succ := range succs {
		if m[succ] {
			log.Fatalf("can't have a repeat successor name %s in %s", succ, rule)
		}
		m[succ] = true
	}
	for _, succ := range newsuccs {
		if !m[succ] {
			log.Fatalf("unknown successor %s in %s", succ, rule)
		}
		delete(m, succ)
	}

	// whether a block has already been emitted. In general forward
	// branches are assumed 'not taken' and backward branches are
	// assumed 'taken'.
	if next == succs[0] {
		succs[0], succs[1] = succs[1], succs[0]
		mask = mask.Inverse()
	}

	p := s.Br(blockAsm(b), succs[0])
	switch b.Kind {
	case ssa.BlockS390XBRC:
		p.From.Type = obj.TYPE_CONST
		p.From.Offset = int64(mask)
	case ssa.BlockS390XCGRJ, ssa.BlockS390XCRJ,