Basic Picturefill

{% if entry.homepageHeroDesktop|length > 0 and entry.homepageHeroMobile|length > 0 %}
  <div class="homepage-hero homepage-hero--image">
    <figure>
      <picture>

        {% set homepageHeroDesktop = entry.homepageHeroDesktop.first().getUrl() %}
        {% set homepageHeroMobile = entry.homepageHeroMobile.first().getUrl() %}

        <!--[if IE 9]><video style="display: none;"><![endif]-->
        <source srcset="{{ homepageHeroDesktop }}" media="(min-width: 540px)">
        <source srcset="{{ homepageHeroMobile }}">
        <!--[if IE 9]></video><![endif]-->

        <!--[if lt IE 9]>
        <img src="{{ homepageHeroDesktop }}" alt="">
        <![endif]-->

        <!--[if !lt IE 9]> -->
        <img srcset="{{ homepageHeroDesktop }}" alt="">
        <!-- <![endif]-->

      </picture>
      <div class="homepage-hero__overlay">{{ entry.homepageHeroText }}</div>
    </figure>

  </div>
{% endif %}

Less than ie9 just uses fallback <img src>, does Picturefill not polyfill for ie less than 9?