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 {
				if !checkBlk(fb.Preds[i].b, gb.Preds[i].b) {
					return false
				}
			}
			return true

		}
		return blkcor[fb] == gb && blkcor[gb] == fb
	}

				decisionBlock = c
			} else if len(c.Preds) == 1 && len(d.Preds) == 1 && c.Preds[0].Block() == d.Preds[0].Block() {
				decisionBlock = c.Preds[0].Block()
			} else {
				lv.f.Fatalf("can't find write barrier pattern %v", v)
			}
			if len(decisionBlock.Succs) != 2 {
				lv.f.Fatalf("common predecessor block the wrong type %s", decisionBlock.Kind)
			}

			// Flow backwards from the control value to find the

	after := map[ID][]*Block{}

	// Check each loop header and decide if we want to move it.
	for _, loop := range loopnest.loops {
		b := loop.header
		var p *Block // b's in-loop predecessor
		for _, e := range b.Preds {
			if e.b.Kind != BlockPlain {
				continue
			}
			if loopnest.b2l[e.b.ID] != loop {
				continue
			}
			p = e.b
		}
		if p == nil {
			continue
		}
		p.Hotness |= HotInitial

		// facts of b.Preds[1] are (in general, b.Preds[1] is
		// a loop-back edge, so we haven't even been there
		// yet). As a conservative approximation, we look for
		// this condition in the predecessor chain until we
		// hit a join point.
		uniquePred := func(b *Block) *Block {
			if len(b.Preds) == 1 {
				return b.Preds[0].b
			}
			return nil
		}

	for len(q) > 0 {
		// pop a reachable value
		v := q[len(q)-1]
		q[len(q)-1] = nil
		q = q[:len(q)-1]
		for i, x := range v.Args {
			if v.Op == OpPhi && !reachable[v.Block.Preds[i].b.ID] {
				continue
			}
			if !live[x.ID] {
				live[x.ID] = true
				q = append(q, x) // push
				if x.Pos.IsStmt() != src.PosNotStmt {
					liveOrderStmts = append(liveOrderStmts, x)
				}
			}

		node := work[len(work)-1]
		work = work[:len(work)-1]

		switch node.op {
		case Work:
			b := node.block

			// First, see if we're dominated by an explicit nil check.
			if len(b.Preds) == 1 {
				p := b.Preds[0].b
				if p.Kind == BlockIf && p.Controls[0].Op == OpIsNonNil && p.Succs[0].b == b {
					if ptr := p.Controls[0].Args[0]; nonNilValues[ptr.ID] == nil {
						nonNilValues[ptr.ID] = ptr

		if b == f.Entry {
			// Regalloc state is empty to start.
			if nphi > 0 {
				f.Fatalf("phis in entry block")
			}
		} else if len(b.Preds) == 1 {
			// Start regalloc state with the end state of the previous block.
			s.setState(s.endRegs[b.Preds[0].b.ID])
			if nphi > 0 {
				f.Fatalf("phis in single-predecessor block")
			}
			// Drop any values which are no longer live.

//		do something
//	      nxt = inc + ind
//		goto loop
//
//	 exit_loop:
func findIndVar(f *Func) []indVar {
	var iv []indVar
	sdom := f.Sdom()

	for _, b := range f.Blocks {
		if b.Kind != BlockIf || len(b.Preds) != 2 {
			continue
		}

		var ind *Value   // induction variable
		var init *Value  // starting value
		var limit *Value // ending value

		// Check that the control if it either ind </<= limit or limit </<= ind.

// CHECK:   cf.br ^bb1([[CASTENTRY]] : tensor<!tf_type.variant>)
// CHECK: ^bb1([[CONDARG0:%.+]]: tensor<!tf_type.variant>):        // 2 preds: ^bb0, ^bb2
// CHECK:   [[CONTINUE:%.+]] = call @testWhileCond([[CONDARG0]]) : (tensor<!tf_type.variant>) -> tensor<i1>
// CHECK:   [[TOBOOL:%.+]] = "tf.ToBool"([[CONTINUE]]) : (tensor<i1>) -> tensor<i1>

					}
				}
			}

			// for each predecessor of b, expand its list of live-at-end values
			// invariant: s contains the values live at the start of b (excluding phi inputs)
			for i, e := range b.Preds {
				p := e.b
				t.clear()
				t.addAll(s.live[p.ID])
				t.addAll(live.contents())
				t.addAll(spillLive[p.ID])
				for _, v := range phis {
					a := v.Args[i]
					if s.values[a.ID].needSlot {