// entry block prolog.
func locatePrologEnd(f *Func, needCloCtx bool) (ID, *Value) {

	// returns true if this instruction looks like it moves an ABI
	// register (or context register for rangefunc bodies) to the
	// stack, along with the value being stored.
	isRegMoveLike := func(v *Value) (bool, ID) {
		n, ok := v.Aux.(*ir.Name)
		var r ID
		if (!ok || n.Class != ir.PPARAM) && !needCloCtx {

		sym := (*types.Pkg)(nil).Lookup(name)
		return types.NewField(src.NoXPos, sym, t)
	}

	fields := []*types.Field{
		makefield("heap", types.Types[types.TBOOL]),
		makefield("rangefunc", types.Types[types.TBOOL]),
		makefield("sp", types.Types[types.TUINTPTR]),
		makefield("pc", types.Types[types.TUINTPTR]),
		// Note: the types here don't really matter. Defer structures

				case "runtime.racefuncenter", "runtime.racefuncexit",
					"runtime.panicdivide", "runtime.panicwrap",
					"runtime.panicshift":
					continue
				}
				// If we encountered any call, we need to keep racefunc*,
				// for accurate stacktraces.
				return false
			case OpPanicBounds, OpPanicExtend:
				// Note: these are panic generators that are ok (like the static calls above).