The word cīra at the end of a tat-puruṣa samāsa has acute accent (udātta) on the first syllable when something is compared with it.,
Thus वस्त्रम् चीरमिव = वस्त्रचीर꣡म्, पटचीर꣡म्, कम्बलचीर꣡म् ॥ Why do we say 'when comparison is meant?' Observe परमचीरम् ॥,