xsltproc very slow processing HTML piped through tidy

Question

I'm using xsltproc to fix HTML files that have been converted to well-formed XML using tidy, but the run-time is unbelievable bad, upwards of a minute for each file. I'm wondering if the XML output by tidy is a problem, or my xsl is stupid, though it's pretty damn simple:

<xsl:stylesheet version="1.0"
 xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
 xmlns:h="http://www.w3.org/1999/xhtml">
    <xsl:output method="html" indent="yes" omit-xml-declaration="yes"/>
    <xsl:template match="@*|node()">
        <xsl:copy>
            <xsl:apply-templates select="@*|node()"/>
        </xsl:copy>
    </xsl:template>
    <xsl:template match="processing-instruction('php')"></xsl:template>
</xsl:stylesheet>