func (u *inlineUnwinder) resolveInternal(pc uintptr) inlineFrame {
	return inlineFrame{
		pc: pc,
		// Conveniently, this returns -1 if there's an error, which is the same
		// value we use for the outermost frame.
		index: pcdatavalue1(u.f, abi.PCDATA_InlTreeIndex, pc, false),
	}
}

func (uf inlineFrame) valid() bool {
	return uf.pc != 0
}

// next returns the frame representing uf's logical caller.