As       As        // assembler opcode
	Reg      int16     // 2nd source operand
	RegTo2   int16     // 2nd destination operand
	Mark     uint16    // bitmask of arch-specific items
	Optab    uint16    // arch-specific opcode index
	Scond    uint8     // bits that describe instruction suffixes (e.g. ARM conditions, RISCV Rounding Mode)
	Back     uint8     // for x86 back end: backwards branch state

			p.As = AANDISCC
			p.From.Offset >>= 16
		}

	// To maintain backwards compatibility, we accept some 4 argument usage of
	// several opcodes which was likely not intended, but did work. These are not
	// added to optab to avoid the chance this behavior might be used with newer
	// instructions.
	//
	// Rewrite argument ordering like "ADDEX R3, $3, R4, R5" into
	//                                "ADDEX R3, R4, $3, R5"

// from an interface's descriptor word (whether a *runtime._type or
// *runtime.itab pointer).
func typeHashFieldOf(pos src.XPos, itab *ir.UnaryExpr) *ir.SelectorExpr {
	if itab.Op() != ir.OITAB {
		base.Fatalf("expected OITAB, got %v", itab.Op())
	}
	var hashField *types.Field
	if itab.X.Type().IsEmptyInterface() {
		// runtime._type's hash field
		if rtypeHashField == nil {

			n.SetType(nil)
			return n
		}
	}
	return n
}

// tcITab typechecks an OITAB node.
func tcITab(n *ir.UnaryExpr) ir.Node {
	n.X = Expr(n.X)
	t := n.X.Type()
	if t == nil {
		n.SetType(nil)
		return n
	}
	if !t.IsInterface() {
		base.Fatalf("OITAB of %v", t)
	}
	n.SetType(types.NewPtr(types.Types[types.TUINTPTR]))
	return n
}

			ir.OAND, ir.OANDNOT, ir.OLSH, ir.OOR, ir.ORSH, ir.OXOR, ir.OCOMPLEX, ir.OMAKEFACE,
			ir.OADDR, ir.OBITNOT, ir.ONOT, ir.OPLUS,
			ir.OCAP, ir.OIMAG, ir.OLEN, ir.OREAL,
			ir.OCONVNOP, ir.ODOT,
			ir.OCFUNC, ir.OIDATA, ir.OITAB, ir.OSPTR,
			ir.OBYTES2STRTMP, ir.OGETG, ir.OGETCALLERPC, ir.OGETCALLERSP, ir.OSLICEHEADER, ir.OSTRINGHEADER:
			// ok: operations that don't require function calls.
			// Expand as needed.
		}

		return false

	case ir.OUNSAFESTRINGDATA:
		n := n.(*ir.UnaryExpr)
		return tcUnsafeData(n)

	case ir.OITAB:
		n := n.(*ir.UnaryExpr)
		return tcITab(n)

	case ir.OIDATA:
		// Whoever creates the OIDATA node must know a priori the concrete type at that moment,
		// usually by just having checked the OITAB.
		n := n.(*ir.UnaryExpr)
		base.Fatalf("cannot typecheck interface data %v", n)
		panic("unreachable")

		n := n.(*ir.SelectorExpr)
		return n.FuncName()

	case ir.OMIN, ir.OMAX:
		n := n.(*ir.CallExpr)
		return walkMinMax(n, init)

	case ir.ONOT, ir.ONEG, ir.OPLUS, ir.OBITNOT, ir.OREAL, ir.OIMAG, ir.OSPTR, ir.OITAB, ir.OIDATA:
		n := n.(*ir.UnaryExpr)
		n.X = walkExpr(n.X, init)
		return n

	case ir.ODOTMETH, ir.ODOTINTER:
		n := n.(*ir.SelectorExpr)
		n.X = walkExpr(n.X, init)
		return n

	case ir.OADDR:

	types, etypes         uintptr
	rodata                uintptr
	gofunc                uintptr // go.func.*

	textsectmap []textsect
	typelinks   []int32 // offsets from types
	itablinks   []*itab

	ptab []ptabEntry

	pluginpath string
	pkghashes  []modulehash

	// This slice records the initializing tasks that need to be
	// done to start up the program. It is built by the linker.
	inittasks []*initTask