<li>
	<code>x</code> is <a href="#Assignability">assignable</a>
	to <code>T</code>.
	</li>
	<li>
	ignoring struct tags (see below),
	<code>x</code>'s type and <code>T</code> have <a href="#Type_identity">identical</a>
	<a href="#Types">underlying types</a>.
	</li>
	<li>
	ignoring struct tags (see below),
	<code>x</code>'s type and <code>T</code> are pointer types

	to <code>T</code>.
	</li>
	<li>
	ignoring struct tags (see below),
	<code>x</code>'s type and <code>T</code> are not
	<a href="#Type_parameter_declarations">type parameters</a> but have
	<a href="#Type_identity">identical</a> <a href="#Underlying_types">underlying types</a>.
	</li>
	<li>
	ignoring struct tags (see below),
	<code>x</code>'s type and <code>T</code> are pointer types

	FNMSUBS F1, F2, F3, F4          // ec8110fc
	FNMSUBSCC F1, F2, F3, F4        // ec8110fd
	FSEL F1, F2, F3, F4             // fc8110ee
	FSELCC F1, F2, F3, F4           // fc8110ef
	FABS F1, F2                     // fc400a10
	FNABS F1, F2                    // fc400910
	FABSCC F1, F2                   // fc400a11
	FNABSCC F1, F2                  // fc400911
	FNEG F1, F2                     // fc400850

	pkgTags  = map[string][]string{}    // map import dir to list of relevant tags
)

// tagKey returns the tag-based key to use in the pkgCache.
// It is a comma-separated string; the first part is dir, the rest tags.
// The satisfied tags are derived from context but only those that
// matter (the ones listed in the tags argument plus GOOS and GOARCH) are used.
// The tags list, which came from go/build's Package.AllTags,
// is known to be sorted.