// TestNilcheckAddr verifies that nilchecks of OpAddr constructed values are removed.
func TestNilcheckAddr(t *testing.T) {
	c := testConfig(t)
	ptrType := c.config.Types.BytePtr
	fun := c.Fun("entry",
		Bloc("entry",
			Valu("mem", OpInitMem, types.TypeMem, 0, nil),
			Valu("sb", OpSB, c.config.Types.Uintptr, 0, nil),
			Goto("checkPtr")),
		Bloc("checkPtr",
			Valu("ptr1", OpAddr, ptrType, 0, nil, "sb"),

			// find SB and SP values in entry block
			initpos := f.Entry.Pos
			sp, sb = f.spSb()
			wbsym := f.fe.Syslook("writeBarrier")
			wbaddr = f.Entry.NewValue1A(initpos, OpAddr, f.Config.Types.UInt32Ptr, wbsym, sb)
			wbZero = f.fe.Syslook("wbZero")
			wbMove = f.fe.Syslook("wbMove")
			if buildcfg.Experiment.CgoCheck2 {
				cgoCheckPtrWrite = f.fe.Syslook("cgoCheckPtrWrite")

				f.Fatalf("phi length %s does not match pred length %d for block %s", v.LongString(), len(b.Preds), b)
			}

			if v.Op == OpAddr {
				if len(v.Args) == 0 {
					f.Fatalf("no args for OpAddr %s", v.LongString())
				}
				if v.Args[0].Op != OpSB {
					f.Fatalf("bad arg to OpAddr %v", v)
				}
			}

			if v.Op == OpLocalAddr {
				if len(v.Args) != 2 {

	switch op {
	// Note that Nilcheck often vanishes, but when it doesn't, you'd love to start the statement there
	// so that a debugger-user sees the stop before the panic, and can examine the value.
	case OpAddr, OpLocalAddr, OpOffPtr, OpStructSelect, OpPhi, OpITab, OpIData,
		OpIMake, OpStringMake, OpSliceMake, OpStructMake0, OpStructMake1, OpStructMake2, OpStructMake3, OpStructMake4,

	}
	base, _ := splitPtr(v.Args[0])
	mem := v.Args[1]
	size := v.Type.Size()

	if root.Block.Func.Config.arch == "S390X" {
		// s390x can't handle unaligned accesses to global variables.
		if base.ptr.Op == OpAddr {
			return false
		}
	}

	// Check all the entries, extract useful info.
	type LoadRecord struct {
		load   *Value
		offset int64 // offset of load address from base
		shift  int64
	}

			// We assume that SlicePtr is non-nil because we do a bounds check
			// before the slice access (and all cap>0 slices have a non-nil ptr). See #30366.
			if v.Op == OpAddr || v.Op == OpLocalAddr || v.Op == OpAddPtr || v.Op == OpOffPtr || v.Op == OpAdd32 || v.Op == OpAdd64 || v.Op == OpSub32 || v.Op == OpSub64 || v.Op == OpSlicePtr {
				nonNilValues[v.ID] = v
			}
		}
	}

// The debug info encodes value locations like 8(R3)
// as a sequence of these op codes.
// This package does not implement full expressions;
// the opPlusUconst operator is expected by the type parser.
const (
	opAddr       = 0x03 /* 1 op, const addr */
	opDeref      = 0x06
	opConst1u    = 0x08 /* 1 op, 1 byte const */
	opConst1s    = 0x09 /*	" signed */
	opConst2u    = 0x0A /* 1 op, 2 byte const  */

	var used ir.NameSet               // used autos that must be kept

	// visit the value and report whether any of the maps are updated
	visit := func(v *Value) (changed bool) {
		args := v.Args
		switch v.Op {
		case OpAddr, OpLocalAddr:
			// Propagate the address if it points to an auto.
			n, ok := v.Aux.(*ir.Name)
			if !ok || n.Class != ir.PAUTO {
				return
			}
			if addr[v] == nil {
				addr[v] = n
				changed = true

	}
	// match: (EqPtr (Addr {x} _) (Addr {y} _))
	// result: (ConstBool [x == y])
	for {
		for _i0 := 0; _i0 <= 1; _i0, v_0, v_1 = _i0+1, v_1, v_0 {
			if v_0.Op != OpAddr {
				continue
			}
			x := auxToSym(v_0.Aux)
			if v_1.Op != OpAddr {
				continue
			}
			y := auxToSym(v_1.Aux)
			v.reset(OpConstBool)
			v.AuxInt = boolToAuxInt(x == y)
			return true
		}
		break
	}

		return !overlap(off1, n1, off2, n2)
	}
	// p1 and p2 are not the same, so if they are both OpAddrs then
	// they point to different variables.
	// If one pointer is on the stack and the other is an argument
	// then they can't overlap.
	switch p1.Op {
	case OpAddr, OpLocalAddr:
		if p2.Op == OpAddr || p2.Op == OpLocalAddr || p2.Op == OpSP {
			return true
		}