The spec is somewhat ambiguous as to what should happen in this case:

<label>label-wrapping-text
    <input id="foo" type="text" title="text-title" placeholder="text-placeholder">
</label>

For #foo, common sense suggests that the accessible name should be "label-wrapping-text" and the description/help should be "text-placeholder". However, implementing a naive, literal reading of the API results in the accessible name being "label-wrapping-text text-placeholder" and the description being "text-placeholder".

There's no specific guidance about computing text of descendants of a wrapped label. We can make a guess, but this case should probably be addressed in the 
HTML Accessibility API Mappings doc.